Most of the previous studies on the heavy pollution process in winter in Beijing focused on aerosol and paid less attention to fog in the process. Based on the L-band radiosonde and surface meteorological observation data of Beijing southern suburb observatory, as well as satellite data, such as MODIS and VISSR, the fogs during the period of heavy pollution in Beijing from January 12 to 15, 2013 were analyzed. The results showed that two radiation fog processes and two advection fog processes occurred in four days during the period. Each day's fog was completely different in terms of type, vertical distribution, formation process, stratification and so on. A mature radiation fog occurred on the morning of January 12, and the generation and development of radiation fog made the stratification of surface layer change from stable condition to near-neutral. Advection fog with 2 connected layers each with different origin occurred on the morning of January 13. The arrival of advection fog dissipated the fog in the surface layer and increased the vertical diffusion capability in the low atmosphere. Another radiation fog occurred on the morning of January 14, and the development was limited to its incipient stage and the lifetime was just about 2 h. There was ground inversion when the fog occurred. Deepened advection fog occurred on the morning of January 15. The height of fog top raised about 500 m compared with the last night fog. Given the complexity and variability in the fog formation, its vertical structure and influence on stratification during heavy pollution in winter in Beijing, research on fog layer and its effects on vertical diffusion and radiation during the heavy pollution needed to be strengthened.

In order to compare the air quality of Beijing and Hohhot and discuss the different causes and the prevention and control measures of air pollution, the characteristics of air pollutant quality concentration, primary pollutant change and air quality index of the two cities was analyzed based on the regular monitoring data of air quality of the two cities from January 2014 to December 2019 released by Environmental Monitoring Station of China. The results showed that: The pollutants in the atmosphere of Beijing and Hohhot, including PM₁₀, PM_2.5, SO₂, NO₂ and CO, shared similar seasonal variation characteristics. The air quality of both cities was the best in summer and the worst in winter. The chief pollutant contributing to the air quality of the two cities was particulate matter, with PM_2.5 in Beijing and PM₁₀ in Hohhot. Long-term monitoring data showed that the concentration of pollutants in the air of the both cities present a continuous downward trend with the rapid development of economy and society, while the concentration of O₃ was still increasing. According to the correlation analysis between the economic index and pollutant concentration in the two cities, high-quality urban development is increasingly constrained by air quality, improving urban economic structure plays an important role in preventing and controlling air pollution.

Based on the monitoring data of national control monitoring stations in the urban area of Kunming in 2013-2020, the temporal and spatial distribution features of atmospheric pollutants were analyzed. The results showed that during the period of 2013-2020, the annually-averaged concentration of O₃ in the urban area of Kunming generally showed an upward trend, and the annually-averaged concentrations of other pollutants showed a downward trend. The annually-averaged concentration of O₃ increased by 4.1%, while that of SO₂ dropped by 67.9% and other pollutants dropped by 35.0%-55.0%. The proportion of days of primary pollutants exceeding Level 1 or above the standard of Ambient Air Quality Standards (GB 3095—2012 ) indicated that O₃ instead of PM_2.5 had become the primary atmospheric pollutant in Kunming. The highest concentration of O₃ appeared in spring, followed by summer, and the lowest in autumn, the concentrations of PM₁₀ and PM_2.5 were generally high in spring and winter but low in autumn, and as for SO₂, NO₂ and CO, the highest concentrations appeared in winter and lowest in summer. But the variation ranges in four seasons of SO₂ and NO₂ were smaller than that of other pollutants. O₃ in spring and summer and PM_2.5 in spring and winter were the key points of air pollutants control in Kunming. The daily variation of O₃ presented single peak distribution, CO, NO₂, PM₁₀ and PM_2.5 presented double peaks distribution, but the variation of peak-valley of PM₁₀ and PM_2.5 concentrations were not distinct. The peaks of NO₂, PM_2.5, PM₁₀ and CO were identical to morning rush hours, the peak of O₃ usually appeared during 14:00-15:00, and the concentration of SO₂ was higher in the morning than in the afternoon. As for spatial distribution patterns, remarkable distinctions existed for different pollutants. The concentrations of SO₂, PM_2.5, NO₂, PM₁₀ and CO of western stations were 54.5%, 20.0%, 17.9%, 14.6% and 2.4%, respectively higher than those of eastern stations. On the contrary, O₃ concentrations in eastern stations were 9.0% higher than that of western stations. The difference of SO₂, NO₂ and O₃ concentrations between eastern and western stations had narrowed down year by year, and this might be caused by the weakening of the impact of pollution transmission from Anning Industrial Park.

Metal elements (MEs) are important compositions of atmospheric particles. The research progress of distributions and ecological and human health risk assessments of MEs in atmospheric particles with different particle sizes were reviewed. In atmospheric particles, MEs mainly presented three particle size distributions: unimodal distribution with the peak in fine or coarse mode particles, and bimodal distribution, corresponding to different pollution sources. Moreover, enrichment factor, geo-accumulation index and potential ecological risk index were the common three methods for ecological risk assessment of MEs. The degrees of enrichment of fine mode particles were significantly higher than that of coarse mode particles for most MEs. Atmospheric particles in Chinese cities all showed a very high comprehensive potential ecological risks (Risk Index > 1 000). Cd, Pb, As were the main polluting elements at present, which should be paid special attention to. In addition, particles of different sizes would be deposited in different parts of the respiratory system. The health risk assessments showed that heavy metals had carcinogenic and non-carcinogenic risks to the human body in most Chinese cities. Cr, As and Cd showed carcinogenic risks to human health, and Mn may cause non-cancer risks. Thus, combining the distribution characteristics of MEs in particles with different particle sizes with their risk assessment was the key research direction in this field in the future.

Hetian oasis located at the south edge of Taklimakan Desert was selected as the study area, and the 36 h of the backward trajectory of air parcel at the ending point (79.72°E, 37.26°N) for 2891 dusty days in the period of 2004-2018 were simulated by using HYSPLIT backward trajectory model and NCEP-GDAS global meteorological data. The transport pathway and meteorological characteristics of air parcel in dusty days were quantitatively analyzed by using k-means clustering technique. The results showed that there was no significant variation in the annual frequency of dust storms from 2004 to 2018, and there was no obvious increase or decrease trend. Spring and summer (from March to July) were the main dusty seasons, accounting for 70.2% of the total dust weather in the whole year, with May and June being the most active periods of strong dust storms. During the dust weather, the movement height and trajectory pathway of air parcel were quite different. The trajectories of dust storms arriving at Moyu County were categorized by k-means clustering into 4 clusters, NW-W cluster, N-N cluster, NE-E cluster and E-ES cluster, which showed distinct features in terms of the air parcel origins and the entry direction to the study site, and their frequencies were 18.9%, 12.3%, 60.1% and 7.8%, respectively. Among them, air masses arriving at the study area from east to west showed the highest frequency (60.1%), and it was mainly floating dust weather. The frequency of dust from northwest to southeast was not high, but the moving speed was the fastest, and strong dust storms and sand blowing mainly came from northwest and west. The dust storms from north to south had the slowest speed (1.36 m/s), the lowest air humidity (26.4%), and the highest temperature (292.58 K). The different transport pathways of dust storms in Moyu County were quantitatively confirmed, which could provide a reference for the study of dust storms in the oasis area.

In order to understand the emission of flue gas pollutants from open burning of crop straws in Inner Mongolia Autonomous Region, a self-designed biomass combustion system was used and typical crop (sunflower and corn) straws in Inner Mongolia were taken as the research objects to conduct indoor simulated combustion experiment. The emission characteristics of straw burning were studied by comparing the differences of emission factors of CO, CO₂, NO_x, C_xH_y and PM_2.5 in different areas. The results showed that the emission factors of CO, CO₂, NO_x, C_xH_y and PM_2.5 of sunflower straw were (344.71±66.36), (1 147.73±229.01), (3.20±0.62), (138.48±28.22) and (0.97±0.20) g/kg, respectively, and the emission factors of CO, CO₂, NO_x, C_xH_y and PM_2.5 of corn straw were (319.69±52.27), (1 178.75±149.00), (1.29±0.04), (57.83±9.45) and (1.44±0.17) g/kg, respectively. The emission factors of PM_2.5 of crop straws in different areas were (0.23±0.11) - (3.26±0.16) and (0.53±0.35) - (2.91±1.69) g/kg in flaming and smoldering, respectively; the emission factors of CO were (162.66±15.94) - (381.65±81.74) and (235.29±34.43) - (569.80±165.72) g/kg in flaming and smoldering, respectively; the emission factors of CO₂ were (1 094.96±182.04) - (1 866.22±377.83) and (725.10±107.71) - (1 409.43±82.32) g/kg in flaming and smoldering, respectively. The emission factor of CO₂ was higher in flaming than that of smoldering, and the emission factors of CO, NO_x, C_xH_y and PM_2.5 were higher in smoldering than those in flaming.

Taking Fujian Province as the research object, based on the data from 37 national air monitoring stations and land use/cover data in Fujian Province, the effects of land use/cover on the annual and seasonal variations of SO₂, NO₂, O₃ and CO pollution concentrations were analyzed. Then, buffer zones of different radii of the national monitoring stations were established, the landscape pattern indexes were calculated, and the effects of the landscape pattern of land use/cover on SO₂, NO₂, O₃ and CO concentrations at different scales were discussed. The results showed that: Land use/cover had a significant effect on the change of atmospheric pollutant concentration. SO₂, NO₂ and CO concentrations all showed the highest values in construction land, and O₃ concentrations showed the highest values in cultivated land. The seasonal variation of the concentration of air pollutants under different land uses/covers was different. The concentration of SO₂ in cultivated land was low in spring and winter, high in summer and autumn, and others were high in spring and winter, low in summer and autumn. The concentration of NO₂ was high in spring and winter, but low in summer and autumn. The concentration of O₃ in cultivated land and forest land was high in spring and autumn, and low in summer and winter, while the concentration of O₃ in construction land and grassland decreased from spring to winter successively. The CO concentration was low in summer and autumn, but high in spring and winter. The effects of different landscape pattern indexes on the concentration of air pollutants were different with the scale effect. Among them, the patch density (PD) in the grassland within the radius of 3 000 m in spring and winter and 4 000 m in summer and autumn had the most significant and negative correlation on SO₂ concentration, indicating that the higher the density of grassland patches was, the lower the SO₂ concentration would be. There was a positive correlation between the number of patches (NP) and NO₂ concentration in the 4 000 m radius of forest land in spring and winter, indicating that the more broken forest land was, the higher the NO₂ concentration would be. NP of construction land within 3 000 m radius was negatively correlated with NO₂ concentration, indicating that the more broken the construction land was, the lower the NO₂ concentration would be. There was a positive correlation between the concentration of O₃ and the proportion of landscape (PLAND) of cultivated land in the radius of 5 000 m, indicating that the greater the PLAND of cultivated land was, the higher the concentration of O₃ would be. There was a positive correlation between the concentration of O₃ and the PLAND of forest land in the radius of 1 000 m, indicating that the increase of PLAND of forest land had certain influence on the increase of O₃ concentration. Except for autumn, the PLAND of forest land was related to the CO concentration in the radius of 1 000 m, showing that the greater the PLAND of forest land was, the lower the concentration of CO would be. At the same time, through the analysis of different scales of landscape indexes, it was found that the best study scale of SO₂ was 3 000 m, and that for NO₂ and O₃ was 4 000 and 5 000 m, respectively, while a better study scale for CO was 3 000 m.

The emission characteristics of gaseous pollutants and the fuel consumption from eleven gasoline light-duty gasoline cars were studied, using the portable emission measurement system (PEMS). The results showed that the emission factors of light-duty gasoline cars were (910.4±822.6) mg/km for carbon monoxide (CO), (58.0±48.3) mg/km for nitrogen oxides (NO_x), and (21.6±16.1) mg/km for total hydrocarbons (THC), respectively. The emission rates of CO, NO_x, and THC increased with the increase of vehicle specific power-velocity (VSP-v), and the emissions in the cold start phase accounted for 11.2%±2.1%, 3.7%±5.4%, and 52.7%±4.6% of the total CO, NO_x, and THC mass, respectively. The transient fuel consumption rates of the light-duty gasoline cars increased with the increase of VSP-v. Vehicle relative fuel consumption increased significantly as the vehicle average speed was less than 15 km/h, and increased slightly as the vehicle average speed was over 40 km/h. The emission rates of CO, NO_x, and THC at 20 ℃ were higher than those at 1 ℃. Ambient temperature also dramatically influenced vehicle fuel consumption rate. Especially when the vehicle was running at high speed, the fuel consumption rate at 1 ℃ was 27.1%±24.5% higher than that at 20 ℃.

Guided by IPCC Guidelines for National Greenhouse Gas Inventories and Guidelines for the Preparation of Provincial Greenhouse Gas List, the greenhouse gas (GHG) emission list of three municipal solid waste (MSW) treatment methods in Beijing was established, the GHG emissions of CH₄, CO₂ and N₂O under different MSW treatment methods in 2010-2019 were calculated, the variation characteristics of CO₂ emissions over time were analyzed, and carbon emission reduction strategies were put forward. The results showed that: 1) From 2010 to 2019, the GHG emissions from MSW treatment in Beijing generally increased first and then reduced, and the change range had slowed down. In 2019, it reached the lowest level in 10 years, which was mainly related to the change of waste treatment from landfill to incineration in Beijing in recent years. 2) In 2018, the incineration amount of MSW exceeded the landfill amount in Beijing, and the CO₂ emissions of MSW incineration treatment were much lower than that of landfill treatment, indicating that the CO₂ emission intensity of incineration treatment was lower than that of landfill treatment. 3) The GHG emission of MSW treatment was closely related to the garbage treatment methods and treatment amount. With the increasing production of MSW, it was suggested to strengthen waste fine classification in the whole process of MSW management and promote source reduction, carry out the construction of waste treatment facilities reasonably, optimize the waste collection and transportation system, prevent the secondary pollution of waste treatment, and explore a low-carbon optimization model suitable for China's MSW treatment.

Technology life cycle assessment (TLCA) can provide methodological support for technological improvement, scientific decision-making and carbon neutrality. CiteSpace software was used to study the research characteristics, changing trends, key areas and evolution paths of TLCA and its research progresses in the field of carbon neutralization in recent 20 years. The results showed that the number of published literature related to TLCA was rising, and had entered a rapid development stage since 2006. The papers mainly focused on Engineering, Ecology, Environmental Science, Engineering Environmental, Science & Technology: Other Topics, Energy & Fuels, Green & Sustainable Science & Technology. The research object, evaluation method and application of TLCA were research hotspots in recent years. The energy production technology, carbon footprints and waste treatment technology were the research focus of TLCA. System, model, framework, uncertainty and other aspects were the key points to improve the evaluation method. Applicability development and comprehensive evaluation of methods became the follow-up development direction. Improving the effectiveness of sustainability, efficiency and decision support was the breakthrough to improve the application of TLCA. Carbon footprint LCA could be used to guide the realization and path selection of technology carbon neutralization goals. The combination of LCA system and other assessment methods was becoming a trend, which could improve the accuracy and effectiveness of comprehensive assessment of technology and provide an effective reference for achieving the goal of carbon neutrality.

Taking the screen room in municipal sewage treatment plants (MSTPs) as the object, a new-type double medium pneumatic atomization spray system was developed based on the characterisctics of odour from scattered sources in MSTPs, and the operating parameters of the system were optimized. The system was applied in a MSTP in Beijing and its performence was studied. The results showed that the removal efficiency of hydrogen sulfide and ammonia in the screen room were 90.54%-97.80% and 93.75%-99.42%, respectively with a good deodorization effect. The investment cost of the system was 950 000 yuan, and the operating cost was 36 200 yuan/a. The water cost accounted for 51.10% of the operating cost. The new-type double medium pneumatic atomization spray system is suitable for the in-situ treatment of odour from scattered sources in MSTPs.

As one of the economically highly developed regions in China, Jiangsu Province of the lower reaches of the Yangtze River and the area around Taihu Lake have presented a series of problems in the urban water eco-environment, due to the increasing pollutant discharges brought by urban development and the limited sewage collection and treatment capacity. The characteristics of the urban water eco-environment of 10 cities in this area were summarized from four aspects: water environmental quality, water resources, aquatic ecology and drinking water safety. The existing problems of the regional urban water eco-environment were analyzed from the aspects of pollution source discharge load, urban sewage collection, treatment and reclamation, urban non-point source, industrial sources and risks, aquatic ecology and so on. The results showed that the major source of urban pollutants in the studied region was the urban domestic source, followed by the non-point source in the urban area. The capacity of sewage collection and treatment needed to be improved and the water quality during the rainy season was poor. Industrial pollution showed obvious characteristics in the chemical and textile printing and dyeing industries. The eutrophication and the change of river network structure caused by urbanization led to the degradation of water ecological functions. And then, according to the above characteristics problems and analytical results of regional cities, the corresponding countermeasures and suggestions for water resources protection, urban domestic source control, urban non-point sources control, industrial pollution and risk prevention and control, and the restoration of water ecology were put forward.

The recharging sources of river and reservoir type of drinking water sources in Zhuhai City are mainly from Xijiang River, among which the water storage of reservoir type of water sources is mainly supplied by pumping stations from Xijiang River. Cluster analysis and discriminant analysis were used to analyze the characteristics of spatial and temporal distribution of water quality in drinking water sources, so as to discuss the influence of water season change and water sources location on water quality. Water retention time calculation and correlation analysis were used to preliminarily study the influence of water resources allocation and hydraulic retention time on water quality. The result shows that the source water quality in Zhuhai City could be divided into three categories: upstream river type, downstream river type and reservoir type. The concentrations of total phosphorus, fecal coliform, sulfide and nitrate in reservoir type of water sources were lower than those in river type of water sources. The total phosphorus concentrations in the reservoir and river types of water sources were 0.01-0.04 and 0.04-0.12 mg/L, respectively; and the nitrate concentrations were 0.006-1 and 0.100-2 mg/L, respectively. The river type of water sources in the upstream were less affected by the salt tide. The concentrations of sulfate and chloride of river type of water sources in the downstream increased significantly in the dry season, and the water quality of the water source of the downstream in the wet season was similar to that of the upstream. Based on the above analysis result, water resources allocation measures are proposed: Firstly, the self-purification function of reservoir type of drinking water sources could be utilized by extending the hydraulic retention time, including increasing the utilization rate of the reservoir with large capacity and adjusting the connection mode between reservoirs and pumping stations. Secondly, the salt tide resistance function of upstream river type of drinking water sources could be utilized to ensure water salinity meeting the standard in the dry season. Lower cost advantage of downstream river type of drinking water source could be utilized and the water utilization proportion could be increased in the wet season. Furthermore, the pumping stations with lower total phosphorus and nitrate concentrations (such as total phosphorus concentration reaching the standard limit value of type Ⅲ of lake-reservoir type water sources) and closer to the urban area were preferentially selected for water supply. Through the implementation of the above measures, the consideration of water quality factors in water resource allocation is improved, and the impact of water resource scheduling on water quality and the risk of water quality exceeding standard are reduced.

More than 90% of global groundwater exploitation is used for agricultural production, and groundwater has become an important strategic resource concerning global food security. Hence, understanding the research hot spots and the trends on the impacts of global agricultural production on groundwater is critical for sustainable irrigated agricultural development and groundwater resource protection and utilization. The article is based on China National Knowledge Infrastructure (CNKI) core journal database and Web of Science (WoS) database, the CiteSpace tool was employed to analyze the research papers concerning the impacts of agricultural production on groundwater globally from 2000 to 2020. This study aimed to summarize the frontier, hot spots, and trends of the research field in the past two decades. The results indicated that in the study of the impact of agricultural production on groundwater, the average annual increases of the number of CNKI and WoS papers reached 1.45 and 53.7, respectively. The United States and China were the leading countries in the research field on the impact of agricultural production on groundwater, accounting for 24.94% and 15.70% of published papers, respectively. Among the major research institutions in the world, Chinese Academy of Sciences was the most internationally influential academic institution. The themes of non-point agricultural pollution and groundwater health risk assessment both were the research hot spots worldwide, and would continue to be the hot research topics under the background of population increase, water resource shortage, food crisis and global climate change. Groundwater overexploitation was an important research theme in the field of the impacts of global agricultural production on groundwater, and the highly cited papers by experts Scanlon and Taylor et al were the most influential papers in this research field.

By summarizing the distribution status and research progress of microplastics in the freshwater environment, the abundance, type, particle size, color, shape and influence factors of microplastics in the freshwater environment were analyzed, and the toxic of microplastics on different trophic organisms in freshwater environment ecosystem were summarized. The results showed that the microplastics distribution in the freshwater bodies was affected by human activities, hydrological characteristics, seasons and microplastics types. Freshwater with more human activities, poor hydrodynamic conditions and more precipitation was seriously polluted by microplastics, and the occurrence of microplastics with different densities was different in environmental media. The toxicity of microplastics was closely related to their concentration, particle size and type, and affected the feeding, growth and reproduction ability of aquatic organisms through the enrichment and carrying of chemical pollutants in organisms. The abundance of microplastics in the freshwater environment in China was higher than that in other countries. It was suggested to gradually carry out the investigation and monitoring of microplastics flux in the freshwater environment and river into the sea. The present microplastics research on the toxic effect at home and abroad mainly focused on phytoplankton, Daphnia magna, mussels and zebrafish, which still could not meet the requirement of the microplastics ecological and health risk assessment. It was urgent to research the microplastics toxicity effect of native organisms at different trophic levels in China, so as to provide scientific and technological support for the establishment of the microplastics environmental benchmark in the freshwater environment in the future.

According to the lake ecological restoration theory and engineering practice cases, the construction technology of macrophytes-dominated clear water ecosystem of a new artificial lake was proposed. Through the habitat optimization and the construction of aquatic animals, aquatic plants and microbial systems, as well as regular observation, debugging and maintenance management, a macrophytes-dominated clear water ecosystem was formed with submerged plants as the core, which had strong resistance and self-recovery capabilities. Taking an artificial lake in the northwest as an example, the proposed method was used to construct a water ecosystem. After one year of operation, the main water quality indexes (except TN) reached Class Ⅲ water quality standard of Environmental Quality Standards for Surface Water (GB 3838-2002). In the lake, 5 submersed aquatic plants were widely distributed, such as Potamogeton lucens Linn and Hydrilla verticillata, and had a good reduction effect on pollutants. And a stable macrophytes-dominated clear water ecosystem was realized.

Based on land use classification data in 2000, 2010 and 2018 in Beijing-Tianjin-Hebei Region, the spatial-temporal evolution of ecosystem service value (ESV) in 13 cities were explored by analyzing land use structure and dynamic changes and constructing the ESV model, and the driving factors of ESV in Beijing-Tianjin-Hebei Region were analyzed by geodetector. The results showed that: 1) From 2000 to 2018, cultivated land was the main land use type in Beijing-Tianjin-Hebei Region. Construction land was the land use type with the largest changes in area and amplitude. 2) From 2000 to 2018, ESV in Beijing-Tianjin-Hebei Region showed a downward trend and then an upward trend. Regulation services and support services were always the core functions of ecosystem services in Beijing-Tianjin-Hebei Region, in which hydrological regulation contributed the most. 3) In terms of time, the average ESV (AESV) of Beijing-Tianjin-Hebei Region had little change. From the perspective of space, the spatial distribution difference of AESV in Beijing-Tianjin-Hebei Region was obvious. The high value areas were mainly distributed in the northern Hebei and Beijing-Tianjin regions, and the low value areas were mainly distributed in the plain areas in the central and southern regions. The change of AESV in Beijing-Tianjin-Hebei Region was obvious, and most cities showed a decreasing trend. 4) The sensitivity index of each land use type was less than 1, and the sensitivity index of woodland was the highest, which had the greatest impact on ESV. 5) Geodetector analysis showed that the spatial distribution difference of AESV in Beijing-Tianjin-Hebei Region was affected by regional natural, economic and social factors. The contribution rate of elevation, average GDP and population density was larger. The interaction between different driving forces had a significant effect on the spatial differentiation of AESV in Beijing-Tianjin-Hebei Region.

The core of urbanization strategy is to guide the city and the ecological environment to coexist harmoniously and take the road of sustainable development. Liaoning Province is one of the old industrial bases in northeast China, so it is of great significance to study the coordinated relationship between urbanization and eco-environment quality for the sustainable development of Liaoning Province. Coupling degree, coupling coordination degree and geographical detector were used to empirically analyze the urbanization and eco-environmental quality index, coupling coordination degree and influencing factors of Liaoning Province from 2005 to 2019. The results showed that the urbanization and eco-environmental quality index of the province from 2005 to 2019 ranged from 2.44 to 4.79, with an obvious upward trend on the whole. The urbanization index showed a spatial trend of Shenyang and Dalian as the high-value core area with cluster development of surroundings; the eco-environmental quality index showed the trend of Shenyang as the core area with cluster development of surroundings. The coupling coordination degree of provincial scale kept rising steadily, and the regional coupling coordination degree was mainly near disorder and barely disorder, and the spatial distribution pattern was high in Shenyang and Dalian, and low in eastern and western regions. The influence factors involved in the subsystems of ecological environment governance, economic urbanization and social urbanization contribute greatly to the detection power value of the coupling coordination factor between urbanization and ecological environment quality in different periods. The main influencing factors included the built-up area, the number of people participating in the basic endowment insurance, the transportation volume of domestic garbage and the daily treatment capacity of urban sewage. The overall development of urbanization and eco-environment quality in Liaoning Province was good, and the coupling coordination degree needed to be improved. The government should continue to pay attention to eco-environment governance, strengthen environmental protection, and improve people's quality of life.

In the context of the construction of Xiong'an New Area, it is very important to ensure the biological safety of Daqing River system. In order to study the distribution of invasive plants in Daqing River system and explore the driving factors affecting the distribution, the vegetation in the river/lake riparian zone of Daqing River system was investigated. The invasive plants in the riparian zone were identified, the invasion grade of each species determined, the correlation between the distribution of species invasion and influencing factors including natural environment and human activities analyzed, and the risk of plant invasion and preventive measures in Xiong'an New Area put forward. The results showed that there were 24 species of invasive plants in Daqing River system, 54.2% of the invasive species were amaranth and compositae, the annual species and unintroduced species accounted for 83.3% and 62.5%, respectively, and 62.5% of the invasive plants originated from American. Six kinds of plants, including Amaranthus retroflexus, Bidens pilosa, Pharbitis purpurea, Eclipta prostrata, Bidens frondosa, Abutilon theophrasti, were widely distributed in the basin. There were three regions in which the number of species and invasiveness of invasive plants were significantly higher than that in other regions, including Fangshan mountain section in the upper reaches of Juma River in the middle reaches of the basin, Bazhou urban section of Mangniu River in the lower reaches of the basin, and the plain and mountain junction area near the 100 m elevation boundary. Human activity was the main factor affecting the degree of plant invasion. The higher the road network density and the proportion of construction land, the more conducive to the distribution and diffusion of invasive plants. The degree of plant invasion in Daqing River system could be controlled currently, but it was necessary to pay attention to the risk of plant invasion, settlement, and diffusion during the construction of Xiong'an New Area and take early precautions.

In order to solve the problems of high water consumption and high intensity of water pollution discharge in industrial parks, it is necessary to optimize the water resources network of the parks as a whole to realize the efficient use of water resources. Based on the mathematical planning method, considering the differences in water consumption, discharge volume and water quality among the enterprises in the parks and taking into account the economic and environmental factors, a water network optimization mathematical model including water source, treatment unit and water trap was constructed to form an indirect recycling optimization method of water resources applicable to industrial parks. Based on the water network optimization model, the freshwater demand, wastewater discharge and total cost under different scenarios with the objective of minimum freshwater demand in a typical industrial park were compared. The research results showed that the adoption of the indirect recycling water network optimization scheme could reduce the total freshwater demand by 24.7%, reduce wastewater discharge by 40.5%, and increase wastewater reuse rate by 40.5%, and the total cost was moderate at 4.860 9 million yuan/a, which had high environmental benefits. The optimization model could significantly improve the efficiency of water resource utilization in industrial parks.

The pollution sources in municipal drainage pipe networks are usually diversified. It is of great difficulty to distinguish the various pollution sources. Generally, if the pollution sources are not well identified, the pertinence of pollution control might be impaired. Therefore, it is likely that the mitigation effects will not be satisfactory. Up to now, there still lacks a systematical overview with a focus on the present pollution source identification technologies in municipal drainage pipe networks, which might make it difficult to determine the corresponding traceability technologies according to the pollution scenes quickly and accurately. The existing pollution source identification technologies in municipal drainage pipe networks were systematically reviewed, including the physical investigation, marker species, and water fingerprinting methods, etc. The principles and application status of each typical pollution traceability technology for pipe networks are well illustrated. In addition, the pros and cons of each technology and its application scenarios were compared. At last, the future research orientation of pollution identification technologies in pipe networks was prospected. Aiming at the dislocation of pollution sources in the drainage pipe networks, it was required to apply physical investigation primarily, and then to couple the numerical simulation, water fingerprinting, and marker species methods. Therefore, the target pipe sections, possible discharge industries, and specific drainage entities could be determined. The production, transportation, and discharge characteristics of pollutants could be further clarified using the stable isotope method. This study could provide fundamental support for the efficient identification of the location, intensity, and discharge process of the pollution sources.

Grasping the construction status and operating status of the drainage pipe network is conducive to making targeted decisions on the maintenance and repair of the drainage pipe network. An evaluation index system for the status and operation efficiency of urban drainage pipe network including 14 indexes was established based on service performance, construction status, and maintenance management, and combined with Analytic Hierarchy Process (AHP)-fuzzy comprehensive evaluation method, the status and operation efficiency of the pipe network in Huai'an District, Huai'an City were comprehensively evaluated. The results showed that the main factors affecting the status and operating efficiency of the drainage pipeline network in Huai'an were the centralized collection rate of domestic sewage, the rain and sewage diversion ratio, the sewage treatment rate and the maintenance level of the pipeline network. The sum of the weights of the 4 indicators was greater than the sum of the weights of the other 10 indicators. The comprehensive evaluation level of the drainage pipe network in Huai'an District was above the medium level, among which the service performance and maintenance management of the drainage pipe network were above the medium level and the construction status was below the medium level. Based on the results of the general survey of the pipeline network in Huai'an District, it was proposed that the management of pipeline network diseases and pipeline defects should be the focus of pipeline network maintenance work in the future.

An assembly-type optional sewage-interception rainwater inlet was proposed, with geotextile, stainless steel screen and five different fillers as the filter modules, and the artificial simulated rainwater was equipped for the test to study its removal effect on the pollutants of suspended solids (SS), chemical oxygen demand (COD), ammonia nitrogen (NH₄ ⁺-N), total nitrogen (TN) and total phosphorus (TP), in the initial rainwater under different sewage intercepting devices. Its ability to reduce the initial runoff pollution was tested and the feasibility and economy in practical engineering applications were evaluated. The test results showed that: in the geotextile and stainless steel screen filter modules, geotextile had a good removal effect on SS, while the stainless steel screen had an obvious removal effect on SS when the aperture was decreased to 0.074 mm, but the two filter modules had poor removal effect on COD, NH₄ ⁺-N, TN and TP. The five filtration modules with high furnace ash coke particles, activated zeolite, coconut shell biochar, ceramsite and activated carbon as filter materials, could effectively improve the removal effects of COD, NH₄ ⁺-N, TN and TP in the initial rainwater. Among them, ceramsite could not only achieve the ideal removal effect of nitrogen and phosphorus, but also achieve good removal effect on SS and COD. Its service life was comparable with other filtration modules, and the market unit price (5-13 yuan/kg) was slightly lower than other filtration modules .

The effluent from municipal wastewater treatment plants contains nitrogen and phosphorus compounds, and the effluent discharged into the water body is still easy to cause eutrophication. The study on advanced treatment of effluent to further remove nitrogen and phosphorus pollutants is of practical significance. The removal effect of co-cultivation of different bacteria and microalgae on nitrogen and phosphorus was studied in the experiment, and the combination of dominant bacteria and microalgae was screened out. Response surface methodology (RSM) was used to study the interactive effects of light wavelength (LW), aeration rate (AR) and the inoculation ratio of bacteria (IR) on the removal effect of nitrogen and phosphorus. The optimal parameter combination was proposed, a microalga-bacterial symbiosis system was established, and a verification experiment was carried out. The results showed that among different combinations of algae and bacteria, the co-culture group of Chlorella proteinosa, Bacillus licheniformis and Pseudomonas putida had the best removal effect on TN and TP. When LW was blue light, AR was 1.8 L/min, and IR was 20%, TN maximum removal rate could reach 93.7%, and TP was basically completely removed after 1 day. When LW was blue light, AR was 2.0 L/min, and IR was 5%, the removal rate of ammonia nitrogen after 2 days was 98.4%. When LW was red light, AR was 2.0-3.0 L/min, and IR was 10%-20%, ammonia nitrogen after 2 days was basically completely removed. When LW was blue light, AR was 1.8 L/min, and IR was 20%, it was the optimal parameter condition for nitrogen and phosphorus removal efficiency. The verification results of the optimized parameter combination were consistent with the predicted values. The effluent of the system met Class Ⅴ of Environmental Quality Standards for Surface Water (GB 3838-2002), which provided a theoretical basis for the practical application of the microalgae-bacteria symbiotic system.

In order to fully understand the emission characteristics of microbial aerosols in municipal wastewater treatment plants (MWWTPs), the research progress of microbial aerosols in MWWTPs at home and abroad was systematically expounded. The treatment facilities involving mechanical push flow and aeration mixing in MWWTPs, which included grid room, grit tank, aeration tank, and sludge dewatering room, were the main sources of microbial aerosols. Microbial aerosols were mainly distributed in the inhalable particle size range of less than 4.7 µm. There were differences in the population community of microbial aerosols at various wastewater treatment facilities. Acinetobacter, Enterobacter, Arcobacter, Pseudomonas, and Escherichia coli were common potential pathogenic bacteria in microbial aerosols in the wastewater treatment facilities, which could pose a direct threat to human health through the mucous membrane, damaged skin, and digestive and respiratory tract. The emission characteristics of microbial aerosols in MWWTPs were affected by many factors such as type of sewage treatment process, type and rate of aeration, quality of influent water, temperature and relative humidity, wind speed and direction, solar radiation, and season.

To study the denitrification performance and mechanism of tubular bio-reactor device (TBD) filled with slow-release carbon source for domestic sewage with different nitrogen components, the actual operation effect of TBD in pilot scale under three different concentrations of dissolved oxygen (DO), ammonia nitrogen (NH₄ ⁺-N) and nitrate nitrogen (NO₃ ⁻-N) was investigated. At the same time, the change trends of environmental factors such as DO concentration, carbon-nitrogen ratio (C/N ratio), and carbon source along the TBD were monitored, and 16S rRNA diversity high-throughput sequencing of the matrix in the tube of TBD was conducted at the end of the operation period. The results showed that the removal rates of NH₄ ⁺-N, NO₃ ⁻-N and total nitrogen (TN) in sewage by TBD under three working conditions were more than 90%, proving that TBD had good denitrification performance. The slow-release carbon source contributed to the increase of C/N ratio along the TBD, and COD_Cr of TBD effluent was always lower than the Class Ⅴ standard of Environmental Quality Standards for Surface Water (GB 3838-2002), which indicated that the TBD did not produce excessive organic matter emission during enhanced nitrogen removal. Furthermore, the decrease of DO concentration along the process formed the characteristics of aerobic hypoxia distribution along the TBD and promoted the distribution of aerobic denitrification-anoxic denitrification bacteria along the TBD.

To explore the rules of pollutant migration/deposition in the membrane filtration process, a set of mathematical models conforming to the actual filtration process was introduced. By integrating existing mathematical models and analyzing their respective and common limitations, combining various existing research methods to establish ideas, the concept of the "Unsteady Membrane Clogging Model Fitting Test Method" was put forward to deeply analyze the distribution of pollutants in different spaces inside the membrane module at different times during the membrane filtration process, and to realize the continuity of the whole process of the membrane filtration process and membrane clogging mechanism. In this way, the problem of pollutant deposition on the different trapping layers inside the membrane module could be solved more targetedly. At the same time, the model optimization technology was proposed to provide a theoretical basis for model establishment and refinement.

In order to reveal the pollution mechanism of red mud to groundwater and prevent the pollution, the water quality of leachate from a red mud pile site of an aluminium refinery in northern China was analyzed. Three characteristic pollutants severely exceeding standards were identified: F⁻, SO₄ ²⁻, Al³⁺. Through a one-dimensional sand column experiment, the migration law of the characteristic pollutions in saturated medium sand, fine sand and silt sand was studied. The results showed that the greater the migration distance of characteristic pollutants in the sand column, the smaller the concentration of the pollutants; the smaller the sand particle size, the smaller the permeability coefficient, which means the stronger retention capacity of pollutants and the longer complete penetration time of characteristic pollutants in the sand column. Using Hydrus-1D software to simulate the migration process of the three characteristic pollutants in saturated sand, the dispersion degree （$\alpha$） of the medium sand, fine sand and silty sand was 1.76, 0.95 and 0.58 cm, respectively. The solute reaction parameters K_d and N_u of F⁻ in the three different sands were 2.10, 1.00, 4.10 mg/mL and 24, 28, 30 mL/mg; SO₄ ²⁻ were 1.78, 0.99, 5.00 mg/mL and 12, 20, 32 mL/mg; Al³⁺ were 1.44, 1.65, 4.44 mg/mL and 18, 17, 45 mL/mg, respectively. It was displayed that the smaller the grain of sand, the stronger the adsorption capacity (larger K_d) and the faster the adsorption speed (larger N_u). In order to prevent the pollution of red mud, it was recommended to use silt soil or finer-grained clay as the pollution impermeable layer according to the principle of economy and convenience.

A novel water treatment agent, chloromethyl polystyrene resin supported task-specific ionic liquid(PS-CH₂-(CH₂)₁₆Im) was synthesized by a bonding method. Cr(Ⅵ) and methyl orange (MO) were selected as model anionic pollutants. The performance of selective removal of anionic pollutants in water was systematically investigated by both static and dynamic column tests. The results showed that PS-CH₂-(CH₂)₁₆Im had good selective adsorption for anionic pollutants. The adsorption equilibrium could be reached in 30 minutes, with static maximum adsorption capacity of 90.9 and 62.8 mg/g for Cr(Ⅵ) and MO, respectively, and also could effectively remove Cr(Ⅵ) at a concentration as low as 0.004 mg/L. PS-CH₂-(CH₂)₁₆Im was easy to regenerate and recycle at least 5 times without obvious loss in adsorption performance. By measuring the association constant, it was known that the adsorption mechanism of PS-CH₂-(CH₂)₁₆Im on anionic pollutants was ion association.

The contents of 8 heavy metals in 70 surface soil samples were determined, which were collected in Shanghai City, including six functional areas of parks, traffic areas, education areas, residential areas, industrial enterprises and farmlands. The pollution status and human exposure risk of heavy metals (HMs) in different functional areas were evaluated by pollution index evaluation method and health risk model. Meanwhile, the spatial distributions of HMs based on the geography information system (GIS) were plotted. The results showed that the average values of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn were 8.03, 0.22, 62.73, 35.52, 0.19, 33.67, 29.54 and 116.78 mg/kg, respectively. The contents of Cd, Cu, Hg, Pb and Zn were higher than the soil background values in Shanghai, the enrichment of Hg, Cd and Pb was obvious and the high values were concentrated in the center city. 10% of the soil samples were heavily polluted and 15.7% of the soil samples were moderately polluted. The areas with higher pollution index were mainly located in the urban areas, and the western and northeastern suburbs as well. From the perspective of different functional areas, the traffic areas and the enterprises were severely and moderately polluted, respectively, with a higher pollution index of Cu, Hg and Cd. Human health risk assessment results showed that the descending order of total carcinogenic risk in different functional areas was as follows: enterprises > traffic areas > residential areas > farmlands > education areas > parks, and As contributed the most to carcinogenic risk. High risk areas were concentrated in urban and the southern suburb. The total noncarcinogenic risks were found to be in descending order of residential areas > farmlands > education areas > traffic areas > enterprises > parks. As, Pb and Ni were the main pollutants affecting noncarcinogenic risk. The sampling sites exceeding the acceptable level were located in the eastern area. The study showed that under different assessment methods, heavy metals in urban soils displayed differentiated spatial distribution characteristics, with certain differences in terms of the relative pollution degree in each functional area.

Waste paper recycling has become the primary approach and trend to solve the pressing problem of insufficient traditional pulp and paper raw materials. A comprehensive efficiency evaluation model of waste paper recycling involving multiple indexes was proposed to analyze the comprehensive efficiency of the waste paper recycling process. An evaluation index system of the comprehensive efficiency of the waste paper recycling process was established by specifying five indexes according to material flow and energy flow involved in the process. Based on the combination weighting of game theory, the optimal combination weight of the evaluation index was obtained by optimizing the combination of subjective and objective weights. After that, the comprehensive efficiency evaluation model of waste paper recycling was established based on the matter element model. By applying the proposed evaluation model to the waste paper recycling process of nine enterprises, the comprehensive efficiency level of each enterprise was obtained. The results showed that two enterprises were at a high level, three were medium-high, and four were poor. The study case showed that this model was feasible in reflecting the relative level of comprehensive efficiency and the promotion direction of each enterprise.

Evaluation of the regeneration benefit of zinc oxide enrichment for zinc smelting is of great significance for promoting rational planning of the utilization of regenerated zinc resources and supporting scientific decision-making of environmental management. Based on the survey results of domestic enterprises, an evaluation index system for the comprehensive benefits of zinc oxide enrichment regeneration was established, considering economic, resource, environmental and social factors, where comprehensive weights were obtained by applying the analytic hierarchy process (AHP) and CRITIC method for weighting, and the standard cloud divided by the golden section method was modified. Then a comprehensive benefit evaluation model based on the combination weighting method and cloud model was constructed. After that, a lead-zinc metal company in Jiangxi Province was used as a case study. The results showed that the comprehensive benefit level of the company's zinc production from zinc oxide enrichment regeneration was at a high level. Regarding the first-level factors, the resource benefit was at the highest level; the environmental, social and economic benefits were at the second high level, and the evaluation results of environmental and social benefits were more uncertain. The fuzziness and randomness were considered in the process of evaluation, which provided more comprehensive evaluation information of the regeneration benefit of zinc oxide enrichment for zinc smelting.

Aiming at the difficulty of dewatering and realizing volume reduction of the lead-containing industrial sludge produced from lead-acid battery plants, Fe²⁺ in the sludge was used to perform Fenton preconditioning, and the effect of different dosages of hydrogen peroxide on the subsequent electroosmotic dewatering and reduction of the sludge was explored. The experimental results showed that the sludge pretreated by Fenton conditioning would break some of the flocs and reduce sludge viscosity from 18.0 mPa·s to 4.7 mPa·s. Part of the inorganic ions in the sludge left the solid phase system and entered the filtrate during the dewatering process, resulting in the water content of the subsequent electroosmotic dewatered sludge cake reducing from 82.72% to 69.34% and the content of volatile suspended solids increasing about 30%. Compared with the direct dewatering of the original sludge, the optimized H₂O₂ addition could promote the subsequent reduction of 66.20% of sludge by electroosmotic dewatering. At the same time, Pb content in the dry basis was increased from 265.2 g/kg to 453.6 g/kg, which was beneficial for the subsequent resource utilization or harmless landfill treatment of the sludge.

As a kind of rare and scattered metal, the amount of indium in the crust is little. The indium of waste liquid crystal display (LCD) panels has great resource value. It is of significant reference value for the optimization of the indium regeneration process of waste LCD panels to research on high-efficiency leaching of indium from waste LCD panels and synchronous transfer control of impurity ions. Waste LCD panels were used as test material and sulfuric acid as extractant to study the influences of sulfuric acid concentration, leaching time, liquid-solid ratio and reaction temperature on the leaching rate of indium, iron, aluminium and silicon. The results showed that the concentration of sulfuric acid had a great influence on the leaching of indium, iron, aluminium and silicon, the leaching of impurity elements could be inhibited effectively by controlling appropriate sulfuric acid concentration. Properly prolonging the leaching time was beneficial to the leaching of indium, but had little effect on the leaching of iron, aluminium and silicon. The optimum conditions of indium extraction were as follows: sulfuric acid concentration was 15%, the acid leaching time was 5 h, the liquid-solid ratio was 10, the reaction temperature was 20 ℃, and the indium extraction rate reached 98%.

Natural capital is a necessary guarantee for the green and sustainable development of the economy and society, and its assessment is an important part of maintaining the balance of the regional ecosystem. From the perspective of natural capital for the mining areas, a three-dimensional ecological footprint model was used to calculate the depth and breadth of the ecological footprint of Shanxi mining areas in the Yellow River Basin, its dynamic evolution characteristics were analyzed, and the mechanism of the dynamic evolution of the ecological occupation of the mining areas was further explained. The results showed that: the per capita ecological deficit of Shanxi mining areas in the Yellow River Basin increased from 4.40 hm² in 2010 to 6.31 hm² in 2016, and then decreased to 5.02 hm² in 2019. The gap between ecological footprint and ecological carrying capacity tended to narrow overall. The breadth of the per capita ecological footprint generally showed a declining trend, from 0.63 hm² in 2020 to 0.47 hm² in 2019, and the depth of the per capita ecological footprint showed an inverted U-shaped change trend that first increased and then decreased. The driving mechanism of the spatiotemporal dynamic evolution process of natural capital in Shanxi mining areas in the Yellow River Basin was driven by many factors such as ecological environment supply, resource endowment, social development, economic growth, energy loss and coal pollution. The dynamic evolution of natural capital occupation was positively correlated with coal pollution, energy loss, resource endowment and the secondary industry added value of economic growth, and negatively correlated with ecological environment supply and the environmental regulations of social development. The gap between the ecological footprint and carrying capacity of Shanxi mining areas in the Yellow River Basin tended to improve, but the ecological occupation deficit still existed.

Through analysis of the economic and social development of Xiong'an New Area, following its planning and construction requirements of "promoting green, low carbon production and lifestyle", from four dimensions of economic development, green production, social development and green life, 27 indicators inflecting the main characteristic indicators of the social and economic carrying capacity in the New Area, such as GDP per capita, water consumption per 10 000 yuan GDP, urbanization rate, coverage rate of geothermal resource heating, were extracted by the quantitative methods of correlation analysis and principal component analysis. An evaluation index system of the social and economic carrying capacity of Xiong'an New Area, which conformed to regional characteristics and could reflect the coordinated development degree between social and economic systems, was constructed and used to evaluate the social and economic carrying capacity of the New Area from 2014 to 2018. The results showed that the social and economic carrying capacity of the New Area had shown a steady upward trend, with an average annual growth rate of 12.81%. Especially after 2016, the speed of economic construction and social development had been improved, and investments in green production and green life increased in 2017. Thus the social and economic carrying capacity of the New Area in 2018 was significantly enhanced, 37.66% and 25.01% higher than that in 2016 and 2017 respectively. Finally, the promotion countermeasures were proposed to improve the social and economic carrying capacity of the New Area by sustainably optimizing and adjusting of industrial structure and forming a green production mode, strengthening environmental governance and ecological restoration and promoting a green lifestyle mode, so as to provide a reference for sustainable development of economy and society in the New Area.

To evaluate the degree of coupling and coordination between economic development and ecological environment protection, the coupling coordination relationship between economic and environmental systems was studied by using the comprehensive development evaluation model and the coupling coordination degree model. Taking Gansu Province as an example, the coupling coordination between economy and environment at the provincial level and 14 cities (prefectures) under its jurisdiction from 2011 to 2019 were analyzed in terms of time and space. The results showed that: 1) The comprehensive development level of Gansu Province increased year by year, and the coupling coordination degree of economy and environment increased from 0.005 5 to 0.911 0. The coupling coordination level of Gansu Province was generally on the rise, and achieved good coupling coordination in 2017 with the synchronization economic development and ecological environment protection. 2) The comprehensive development level of economy and environment in 14 cities (prefectures) showed an upward trend, and some cities (prefectures) showed fluctuations in 2016 and 2018. The comprehensive development level of Jiuquan and Lanzhou was higher, while that of Gannan and Dingxi was lower. 3) The coupling coordination degree of economy and environment in 14 cities (prefectures) all broke away from the imbalance recession and entered the coupling coordination stage in 2016. In space, it was the best in the central region, followed by the north and slightly worse in the south.

There exists the problems of single scenario, large amount of data, multiple links involved, complex models, cumbersome operations and unclear governance effects in the process of identifying the key source areas of agricultural non-point source pollution (ANSP). To solve these problems, an information system that could identify and simulate the treatment of the key source areas of ANSP was constructed by using GIS technology combined with InVEST water yield and nutrient transfer rate model. The key source areas identification function was designed under three scenarios, based on the river inflow load, potential runoff concentration and load to water yield ratio, respectively, and the distribution of key source areas under the three scenarios was simulated. The water yield, nutrient transfer rate and loss load sub-models of InVEST were integrated. A simulation function for the treatment of key source areas of ANSP was designed, which could visually display the treatment effects of the key source areas identified under the three scenarios. Taking Haihe River Basin as an example, the software was used to identify and simulate the treatment of the key source areas of non-point source of total nitrogen (TN) in farmland. The results showed that: 1) The key source areas identified based on the river inflow load scenario were relatively scattered, and distributed in most of the water systems except Yongding River and Ziya River. Based on the potential runoff concentration scenario, the distribution of key source areas was relatively concentrated, mostly distributed in the areas from the middle to the south, and the rest were distributed in the southeast. The distribution of key source areas identified based on the load-to-yield ratio scenario of the river basin was highly concentrated, ranging from central to southern of the area. 2) The scenarios based on potential runoff concentration and the ratio of load to water yield had similar effects in the simulation of TN and total phosphorus (TP) governance, and were significantly better than the scenario based on the inflow load. Combined with the above three scenarios set in the software, it could reduce the impact of complex geographic environment, improve the identification efficiency of key source areas of ANSP, and enhance the scientific nature of governance decision-making for the areas. The software is practical.

Nano gas layer, a quasi-two-dimensional gassy absorbate located at the liquid-solid interface, still remains many open questions after relevant investigations for more than ten years. Based on the existing studies, the essential puzzles and significant achievements of the nano gas layers were summarized. The properties of nano gas layer, the relationship between the nano gas layer and nanobubbles, and their dynamic equilibrium were illustrated. More importantly, the current attention and controversies in this field, such as the gas phase authenticity, stability, structural order, and efficient preparation of the nano gas layer were introduced and discussed. Some suggestions to resolve these challenges were presented. This review reported the past development of research of nano gas layers as well as the prospect of their potential applications in some important interfacial reactions in the future.

There are various bubble generation methods which can produce bulk nanobubbles with different sizes and different number concentrations. However, the polydispersity of bubble size and the intrinsic difference of number concentration are inconvenient to the performance research and efficiency comparison of bulk nanobubbles, and it is also not conducive to the standardization and industrialization of nanobubble technology. Therefore, the size control and number concentration adjustment for the bulk nanobubbles are very important. The technologies for controlling the size and number concentration of the bulk nanobubbles in recent years were summarized and comprehensively evaluated. The advantages and disadvantages of size control methods such as cyclic homogenization, microfluidic technology and membrane technology, and number concentration control methods such as freeze-thaw removal method and ultrasonication reduction method were analyzed and compared. All methods were evaluated in terms of controllability, equipment dependence, process difficulty, scalability and cost, and new understandings and ideas for the regulation of nanobubble size and concentration were proposed combined with the published research results. It helped to deeply understand the size effect of the nanobubbles and extra stabilization mechanism and provide new ideas for the quantitative analysis and applications of bulk nanobubbles, especially for the nanobubble size-related properties, effects and applications.

Aiming at solving the problem of low mass transfer efficiency and easy generation of disinfection by-products of traditional ozonation technology, ozone micro-nanobubbles combined with H₂O₂ oxidation system was adopted to improve mass transfer efficiency and oxidation capacity and reduce the production of disinfection by-products. The effects of ozone flow rate, H₂O₂ concentration, and common groundwater geochemical parameters on the degradation of 2-chlorophenol were investigated, and the application of the O₃-H₂O₂ system to typical environmental pollutants was studied. The experimental results showed that the ozone utilization rate was the highest when the ozone rate was 40 mg/min; O₃-H₂O₂ system had the best degradation efficiency on 2-chlorophenol when H₂O₂ concentration was 0.5 mmol/L and pH=9; the existence of Cl⁻, CO₃ ²⁻/HCO₃ ⁻ and natural organic matter inhibited O₃-H₂O₂ system; O₃-H₂O₂ system had good degradation effects on four typical environmental pollutants including antibiotics, chlorophenols, chlorinated hydrocarbons, and nitro-containing organic compounds.

Due to their unique physical and chemical characteristics such as ultra-high stability, easily producing free radicals and high mass transfer efficiency, micro-nanobubbles continue to arouse the exploration interest of domestic and foreign researchers. In recent years, micro-nanobubble technology as a new and high-efficiency technique, has been widely used in aquaculture, agricultural planting, flotation, water treatment, etc. But it is insufficient in the application of improving the soil environment. In this review, based on the existing research results of improving soil environment with micro-nano bubbles, their basic properties, domestic and overseas research progress and applications were reviewed and discussed, and the effect of micro-nanobubbles in the soil improvement process was preliminarily clarified, which could enhance soil permeability, effectively remove organic and metal pollutants in water, change the structure of microbial clusters, and reduce the ability of mineral deposition. It was expected to bring some inspiration for subsequent research on micro-nanobubbles to improve the soil environment.

In order to explore the contribution of organics and salts to membrane fouling and the control effect of micro-nanobubbles on different types of membrane fouling in the treatment of high salt wastewater by vacuum membrane distillation, three typical organic pollutants, humic acid, bovine serum protein and sodium alginate, were selected to investigate the influence of single organic matter, the coexistence of organic matter and salt on membrane pollution and the control effect of micro-nanobubble aeration on membrane pollution. The results showed that the membrane pollution caused by sodium alginate was the most serious among the three organic compounds. When the sodium alginate concentration was 100 mg/L, the relative membrane flux decreased to 67.07% after 7 h of vacuum membrane distillation system operation. When the humic acid concentration of feed solution was 10, 50 and 100 mg/L, the relative membrane flux decreased to 36.33%, 33.15% and 20.59%, respectively, after 7 h of system operation. When three organic compounds coexisted with salt, the membrane pollution was worse than that when single organic compound coexisted with salt. Micro-nanobubbles could effectively control the compound pollution caused by organic-salt coexistence in vacuum membrane distillation system.

Micro-nanobubbles have the characteristics of small bubble particle size, large specific surface area, high dissolved oxygen concentration, long residence time in water and high mass transfer efficiency. Therefore, they have a good application prospect in the field of in-situ remediation of organic pollutants in groundwater. A simple landfill in the south of China was selected as the test site, and the micro-nanobubble preparation and injection integrated device was used to study the effects of process conditions such as extraction synergy, injection flow and injection duration on the mass transfer of oxygen micro-nanobubbles and the degradation and remediation of groundwater pollutants. The test showed that compared with ordinary air aeration, the oxygen concentration peak of oxygen micro-nanobubbles in water was higher and lasted longer. The extraction could significantly improve the mass transfer efficiency of micro-nanobubbles, enhance the influence radius and strengthen the degradation and removal effect of pollutants. Under the condition of multi-round injection-extraction combined processes, the injection influence radius could reach 4 m, with the removal rate of COD and NH₃-N reaching 96.1% and 92.4%, respectively. However, there was a certain rebound after the injection was stopped.

The efficient and compact microbubble generation technology and particle size control technology are the premise and foundation of large-scale industrial application of microbubble technology. The foaming characteristics of gas-liquid two-phase mixing in two-stage Venturi series bubble generator were studied employing CFD numerical simulation and experimental test, the key structural parameters were optimized, and the interactions were analyzed by Response Surface Method. The results showed that the diameter of the throat in the second stage had the greatest influence on the bubble particle size of the two-stage Venturi series bubble generator, followed by the diameter of the throat in the first stage and the second stage expansion angle, while the expansion angle in the first stage had the least influence. Under the same working conditions, the median particle size of bubbles generated by single-stage Venturi bubble generator was 543.64 μm, and the proportion of fine bubbles with particle size less than 100 μm was 8.6%. The median particle size of bubbles generated by two-stage Venturi series bubble generator was 515.99 μm, and the proportion of fine bubbles increased to 12.1%. Thus by controlling the flow rate and changing the number of Venturis in series, the bubble particle size could be adjusted from millimeter level to micron level.