2023 Vol. 13, No. 6

Display Method:
Phosphorus morphology characteristics and its response to climate change in Xingkai Lake
WANG Yang, XIE Zijian, SUN Daixi, LI Chunhua, YE Chun, WANG Wenquan, WEI Weiwei, WANG Hao
2023, 13(6): 1965-1975. doi: 10.12153/j.issn.1674-991X.20230249
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Xingkai Lake is the largest freshwater lake in northeast Asia, and its excessive concentration of total phosphorus (TP) is the main reason for the decline of water quality in Xingkai Lake in recent years. Climate change may have an important impact on regional water quality decline. Taking Chinese region of Xingkai Lake as the research area, by analyzing the temporal and spatial variation characteristics of phosphorus in the water body of Xingkai Lake, the main composition and morphology of phosphorus in the water body of Xingkai Lake were explored, and the change law of climate factors in the region and its influence on TP of the water body of Xingkai Lake were clarified. The results showed that: (1) From 2010 to 2021, the overall TP concentration change in Xingkai Lake showed a trend of first decreasing and then rising, and the water quality of Xingkai Lake in the freezing period was better than that in the non-freezing period, and TP concentration in Great Xingkai Lake was higher than that in Small Xingkai Lake. (2) The phosphorus morphology data in May 2022 showed that the TP of the water bodies in Great Xingkai Lake and Small Xingkai Lake was mainly composed of granular phosphorus (PP) (accounting for 60% and 76%, respectively), which was the main form of TP exceedance. Both the granular phosphorus and dissolved phosphorus in Small Xingkai Lake were higher in the north and lower in the south. For Great Xingkai Lake, the granular phosphorus was higher in the east than in the west, and the dissolved phosphorus showed the opposite trend. (3) In recent years, both temperature and rainfall had shown an upward trend in Xingkai Lake basin, and TP in Great Xingkai Lake had a significant positive correlation with temperature and rainfall, the increase in temperature and rainfall may lead to more nutrients entering the water body, resulting in a decrease in the quality of the water environment. There was no significant correlation between TP of Great Xingkai Lake and climate change, but there was a significant positive correlation between TP of Great Xingkai Lake and Small Xingkai Lake, indicating that Great Xingkai Lake was less affected by regional climate change, but its water quality condition was closely correlated with Small Xingkai Lake. The water quality of Small Xingkai Lake was better than that of Great Xingkai Lake no matter in the freezing or non-freezing period, and as the antecedent reservoir of Great Xingkai Lake, Small Xingkai Lake played an important role in purifying the surface source pollution in the upper watershed.

Distribution characteristics and source analysis of nutrients in sediments of Xingkai Lake
SUN Daixi, XIE Zijian, WANG Yang, YE Chun, LI Chunhua, WEI Weiwei, WANG Hao, ZHENG Xiangyong
2023, 13(6): 1976-1986. doi: 10.12153/j.issn.1674-991X.20220987
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Xingkai Lake is the largest international cross-border lake in China. The water quality of Xingkai Lake has attracted international attention. The release of sediment internal pollution is an important factor affecting water quality. Studying the distribution characteristics and sources of sediment nutrients can provide important support for the water environment management of Xingkai Lake. Small Xingkai Lake and Great Xingkai Lake in China were investigated. Firstly, the distribution characteristics and burial fluxes of total nitrogen (TN), total phosphorus (TP) and organic matter (OM) in the sediments were clarified through the investigation of sediment nutrients and accumulation of sediment. Subsequently, the organic pollution index method was used to evaluate the sediment pollution level of Xingkai Lake. Additionally, nutrient sources were analyzed based on C/N and C/P values. The results showed that compared with other lakes in China, the average concentration of TP in the sediment of Xingkai Lake was at a low level, while the average concentrations of TN and OM in the sediment of Small Xingkai Lake were at a high level. The nutrient concentration was higher in the west and northeast of Small Xingkai Lake with high coverage of aquatic plants, and in the west and middle of Great Xingkai Lake with serious sediment deposition. The OM in the sediments was influenced by both aquatic plants and terrestrial inputs, and Small Xingkai Lake was more affected by terrestrial inputs. Pearson correlation analysis showed that OM and TN were homologous and not homologous with TP. The organic pollution evaluation results presented that Xingkai Lake was in light pollution, while the organic pollution in Small Xingkai Lake was more serious than that in Great Xingkai Lake. In conclusion, Small Xingkai Lake, as the front lake of Great Xingkai Lake, reduced the pollutants imported into Great Xingkai Lake. However, its high sediment nutrient concentrations may have a potential impact on Great Xingkai Lake. Therefore, attention should be paid to the sediment pollution of Small Xingkai Lake.

Ecological risk assessment and pollution characteristic analysis of heavy metals in sediments of Xingkai Lake
XIE Zijian, ZHAO Rongbo, WANG Yang, WANG Hao, LI Chunhua, YU Zongling, YE Chun
2023, 13(6): 1987-1996. doi: 10.12153/j.issn.1674-991X.20230668
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Xingkai Lake is a cross-border lake between China and Russia. It is of great practical significance to study the sources and ecological risks of heavy metals in the sediments of Xingkai Lake for the protection and treatment of the regional ecological environment. The surface and columnar sediment samples of Xingkai Lake in China were collected systematically, and the contents of heavy metals As, Cd, Cu, Pb, Hg, Ni, Cr and Zn were determined. The pollution status and potential ecological risk of heavy metals were evaluated by the geo-accumulation index method and potential risk index method, and their potential sources were analyzed by the mathematical statistics method. The mean values of Cr, Ni, As, Cr and Hg in the surface sediments of Small Xingkai Lake exceeded the reference values of Heilongjiang soil background, while only Ni and Cd in Great Xingkai Lake exceeded the reference values of Heilongjiang soil background. The soil accumulation index evaluation shows that Hg in the surface sediments of Small Xingkai Lake has a high degree of pollution, mainly light pollution and moderate pollution, As and Cd are mainly pollution-free, followed by light pollution, Cd in Great Xingkai Lake is mainly light pollution, and other heavy metals are mainly pollution-free. The evaluation results of the potential ecological risk index show that the surface sediments of Xingkai Lake are generally pollution-free to moderately polluted, and Cd is the most important ecological risk factor. As, Hg and Cd are the main factors of heavy metal pollution, and the areas in the west and east sides of Small Xingkai Lake and the west side of Great Xingkai Lake are more seriously polluted. The pollution is affected by agricultural production activities and mineral exploitation and smelting in the upper reaches. In addition, considering that Cd is enriched at the bottom of Great Xingkai Lake, it may be affected by the natural background.

Effect of land use on the water quality of rivers flowing into Xingkai Lake and ecological restoration strategies
XU Yixue, XIE Zijian, WANG Hao, LI Chunhua, LI Ji, WEI Weiwei, ZHENG Ye, YE Chun
2023, 13(6): 1997-2005. doi: 10.12153/j.issn.1674-991X.20230218
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Xingkai Lake is a cross-border lake between China and Russia, and its water quality change has received high attention from the international community. The water quality of rivers flowing into the lake has an important impact on the water quality of Xingkai Lake. Taking Xingkai Lake basin in China as the research area, based on Nemero pollution index method, variance analysis, redundancy analysis and cluster analysis, the water quality characteristics of the rivers flowing into Xingkai Lake were analyzed, and the impact of land use structure on the river water quality was explored. Classified repair strategies were also proposed accordingly. The results showed that the water quality categories of rivers flowing into Xingkai Lake were Class Ⅲ to Class Ⅴ or below Class Ⅴ of Environmental Quality Standards for Surface Water (GB 3838-2002 ). Chemical oxygen demand, total phosphorus and permanganate index were the main factors exceeding the standard. The water quality of rivers flowing into Xingkai Lake in high flow period was better than that in normal flow period. The water quality of the rivers flowing into Great Xingkai Lake was better than that of the rivers flowing into Small Xingkai Lake. The explanatory degree of land use in Xingkai Lake basin on the water quality of rivers flowing into the lake reached 52.31% and 45.38% during the high and normal flow periods, respectively. Cultivated land had a negative impact on the water quality of the rivers. Forest land and water body had an improvement effect, while artificial surface and grassland had different impacts in different water periods. Based on the cluster analysis of water quality and land use structure, the rivers flowing into Xingkai Lake were divided into three types, i.e. ecological conservation type, ecological restoration type and comprehensive treatment type, and targeted treatment and repair strategies were proposed.

Spatial and temporal characteristics and the heterogeneity of influencing factors of the synergism of pollution and carbon emissions reduction in Beijing-Tianjin-Hebei urban agglomeration
LI Yunyan, DU Wenxin
2023, 13(6): 2006-2015. doi: 10.12153/j.issn.1674-991X.20230269
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Based on the data of Beijing-Tianjin-Hebei urban agglomeration from 2003 to 2020, the coupling coordination degree, spatial Durbin and spatial-temporal geographical weighted regression models were used to explore the spatial and temporal characteristics of the synergistic effect of pollution reduction and carbon reduction in the urban agglomeration and the heterogeneity of its influencing factors. The study showed that carbon emissions grew rapidly from the 10th to the 11th Five-year Plan periods, and then slowed down after the 12th Five-year Plan period. The emission of atmospheric pollutants reached its peak during the 12th Five-year Plan period, and the emission reduction effect during the 13th Five-year Plan period was significant. During the study period, the level of pollution and carbon reduction coupling and coordination showed three phases of fluctuating increase, namely, slow increase, hovering exploration and steady increase; the energy consumption intensity and total energy consumption were the core factors directly affecting the level of pollution and carbon reduction coupling and coordination in the cities. The urbanization rate, real GDP per capita, industrial structure, the amount of foreign investment utilized and the proportion of science and technology expenditure were the core factors affecting the level of pollution and carbon reduction coupling and coordination by affecting energy consumption, and all factors showed spatial and temporal heterogeneity. Finally, optimized countermeasures were proposed in terms of promoting collaborative control of regional pollution reduction and carbon reduction, strengthening differentiated collaborative emission reduction strategies for key cities and key industries, promoting energy restructuring, and focusing on green technology innovation and green financial support.

Prediction of carbon emissions in Shanxi Province based on PSO-BP neural network
YANG Junqi, FAN Xiaojun, ZHAO Yuehua, YUAN Jin
2023, 13(6): 2016-2024. doi: 10.12153/j.issn.1674-991X.20230190
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Shanxi, as a major province of energy use and carbon emission, has an important demonstration significance for the whole country to promote the "dual carbon" strategy. The carbon emissions of Shanxi Province from 2000 to 2020 were calculated based on IPCC emission coefficient method. Tapio decoupling model was used to analyze the decoupling relationship between carbon emissions and economic development, LMDI method was used to decompose the factors affecting carbon emission changes, and PSO-BP neural network model was used to simulate and forecast the carbon emissions of Shanxi Province. The results showed that the carbon emission in Shanxi Province increased during 2000-2020, while the carbon emission intensity decreased, and the decoupling coefficient was 0.585, indicating a weak decoupling state as a whole. Economic growth was the determining factor of carbon emission growth, and the optimization and adjustment of industrial structure and energy intensity was the leading factor to restrain carbon emission. The introduction of particle swarm optimization (PSO) improved the prediction accuracy of BP neural network effectively. The predicted results showed that carbon emissions in Shanxi Province would peak in 2032, 2029 and 2027 under three scenarios: baseline scenario, low carbon scenario and intensive low carbon scenario, respectively. In view of the forecast results, relevant policy suggestions were put forward.

Spatial distribution and regulatory countermeasures of key emission units in the national carbon market
LI Guangyu, WANG Xiaomeng, REN Hui, ZHAI Mingyang, WANG Xiaohui, ZHOU Changbo, LI Mingkui
2023, 13(6): 2025-2032. doi: 10.12153/j.issn.1674-991X.20230406
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The spatial distribution characteristics of key emission units are of great significance to the ecological and environmental departments in formulating the supervision policies for national carbon market data quality, but the current knowledge of these characteristics is still limited. Taking the distribution of key emission units in administrative regions as the research object, and the spatial agglomeration characteristics of key emission units were explored using global and local spatial autocorrelation analysis. Various regions were identified by the spatial clustering method, and control measures were discussed in the context of socioeconomic development, electricity consumption, industrial structure, and other factors. The findings demonstrated that the distribution of key emission units was more concentrated in east and north China, with clear signs of positive spatial autocorrelation at the city and county scales. The results also demonstrated that both high high and low low agglomeration exhibited continuous distribution, with high high agglomeration mainly distributed in areas with abundant coal resources and developed economies. The cities in China were classified into seven regions based on the quantity of key emissionunits and carbon emission-related factors. Region 1 was dominated by the northwest region. Region 2 included parts of Shanxi, Shaanxi, as well as central and eastern Ningxia, northern Xinjiang, and eastern Inner Mongolia. Regions 3, 4, 5 and 6 were primarily found in northeast, north, east, and southwest China, respectively. Region 7 was mostly in the center and south of China. The accuracy of data on carbon emissions could be rapidly evaluated by comparing coal quality parameters between local mines and key emission units in Regions 1, 2 and 6. The distinction between local and imported coal in Regions 3 and 4 could help to categorize and regulate the key emission units, while Regions 5 and 7 should pay close attention to the effects of coal sources on carbon emissions. Additionally, basic capacity building for carbon emission supervision in the concentrated regions of key emission units should be enhanced, and help for carbon emission data quality management should be offered to key emission units in socioeconomically backward areas.

Analysis of synergic reduction of greenhouse gases and air pollutants emission in the urban transportation sector: taking Tangshan City as an example
YANG Rupu, FENG Xiangzhao, WANG Min, LI Liping
2023, 13(6): 2033-2042. doi: 10.12153/j.issn.1674-991X.20230055
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The evaluation of the potential of the synergic reduction of greenhouse gases (GHG) and air pollutants emissions was carried out in the transportation sector, with Tangshan City as a case study, taking into account the GHG emission caused by refrigerant leakage in automobile air conditioning in the synergic emission reduction for the first time. The side effects of phasing out old vehicles were pointed out, and the indicator of synergy degree in the synergic theory was adopted to quantify the synergic reduction capability of the corresponding measures to reduce pollutants and GHG emissions. The results showed that under the implementation of all emission reduction measures, GHG emission from the transportation sector would peak in 2030, and the emission of air pollutants would achieve peak value at the end of the 14th Five-Year Plan. The GHG emission effect of current automobile refrigerant leakage in Tangshan City reached 280 800 tons of CO2 equivalent, accounting for about 4.7% of the total GHG emission. 50% of the leakage came from automobiles, and the leakage would ramp up with the increase in automobile ownership. Therefore, specified measures should be taken to mitigate the leakage of the air conditioning refrigerant in the operation, maintenance, and scrapping processes. The degree of synergic reduction could be effectively distinguished by using synergy evaluation criteria. The absolute emission reduction of phasing out vehicles of national stage Ⅲ and below was large and had good synergy. Although it may cause an increase in refrigerant leakage during the implementation period, it was able to achieve a synergic reduction of GHG and air pollutants overall. Replacing diesel trucks with natural gas ones and improving the "road to water" ratio had a good reduction synergy degree. However, they had a negative synergy in reducing single air pollutant and GHG emissions, which needed to be carried out simultaneously with other emission reduction measures.

Research progress of greenhouse gas emissions and optimization of pollution removal and carbon reduction in constructed wetland
MA Hongyun, ZHOU Lei, ZHANG Xueqi, KONG Lingwei, CHENG Shuiping
2023, 13(6): 2043-2052. doi: 10.12153/j.issn.1674-991X.20230175
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The problem of global warming has being paid attention to increasingly, and the greenhouse gases (GHGs) emissions from the constructed wetlands (CWs) have been concerned, with the widely application of CWs in water treatment. A bibliometric analysis of the related literatures on GHGs emissions from CWs in the Web of Science (WoS) core database was conducted, the key words of 216 research articles were analyzed by clustering, and the progress of main research subjects were summarized. The results showed that: 1) The number of literature on GHGs emissions from constructed wetlands had been increasing since 2003, and the citation frequency of articles also increased. The hot-spot clustering keywords focused on four research directions: the effects of substrate and aeration on greenhouse gases emissions, the effects of plants on greenhouse gases emissions, nitrous oxide (N2O) production and removal pathways, methane (CH4) production and removal pathways. 2) The type and configuration of substrates played important roles in the GHGs emissions in CWs. The process of aeration has the potential to alter the internal redox in CWs, thereby impacting the release of GHGs. The presence of plants led to a decrease in the overall GHGs emissions in CWs, while variations in aerenchyma and biomass among different plants resulted in different GHGs emissions. 3) The N2O in CW was produced by various processes such as nitrification/denitrification, anaerobic ammonia oxidation, nitrate reduction to ammonium, and other pathways. However, denitrification was the unique pathway to remove N2O. The CH4 was produced by anaerobic oxidation of organic matter and removed in two paths of aerobic oxidation and anaerobic oxidation. Therefore, an optimized model was proposed to regulate GHGs emissions in CWs by process combination and operation, substrate configuration and plant selection, carbon addition and intermittent aeration. And it was also proposed to further study the conversion mechanism of N2O and CH4 in CWs, optimize the regulation of GHGs emissions, and achieve pollution reduction and carbon reduction in CWs in the future.

Carbon emission analysis of municipal wastewater treatment plants and discussion on synergistic path of pollution and carbon reduction
ZHANG Haiya, LI Siqi, LI Mingyue, DUAN Liang, ZHANG Hongwei, QIN Wei, ZHAO Liwei, LIU Peng, LÜ Yunlong, WANG Yulong
2023, 13(6): 2053-2062. doi: 10.12153/j.issn.1674-991X.20230040
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The wastewater treatment industry is one of the top ten CO2 emission industries, the carbon emissions of which account for 2%-3% of the total global carbon emissions, and its carbon emissions show an increasing trend year by year. So, carrying out carbon emission reduction in the wastewater treatment industry and achieving the synergistic effect of pollution reduction and carbon reduction is the necessary path to promote the realization of the "double carbon" goal in China. The carbon emission situation of the wastewater treatment plants (WWTPs) of China was systematically analyzed. The result showed that direct CO2 emissions produced by the biochemical treatment process occupied a large proportion of that in the whole processing section, and among them, the direct CO2 emission in the aerobic area was the largest. Meanwhile, the indirect carbon emissions resulting from power and drug consumption accounted for a large proportion of whole direct and indirect carbon emissions, which was the key link of carbon emission reduction of WWTPs. Additionally, the way of anaerobic digestion + biogas power generation was the recommended low-carbon treatment of sludge. The problems of carbon emission reduction in WWTPs mainly included inaccurate carbon emission accounting, the lack of development and application regarding the low-carbon wastewater treatment technology, and inadequate top-level design and management. Based on this, the possible pathways suitable for the synergistic reduction of pollution and carbon of WWTPs in China were put forward, which needed multiple efforts. These efforts included accounting the carbon emission accurately, strengthening the development and application of energy-saving, carbon reduction, carbon replacement and carbon sequestration technology, and designing a multi-dimensional carbon control scheme. Moreover, an overall framework for carbon reduction driven by technological innovation and policy support should be built, thus forming a closed-loop system for carbon reduction in WWTPs, and assisting the low-carbon development of WWTPs of China.

Spatial correlation of PM2.5 pollution in Beijing-Tianjin-Hebei and surrounding cities based on complex networks and their motif
AN Haigang, ZHANG Cuizhi, NIU Jianguang, DONG Xiaojuan
2023, 13(6): 2063-2071. doi: 10.12153/j.issn.1674-991X.20220825
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In recent years, with the increase of pollution control and ecological environmental protection, the quality of the ecological environment in Beijing-Tianjin-Hebei region has continued to improve, but the problem of air pollution with PM2.5 characteristics should not be underestimated. PM2.5 data of 31 cities in Beijing-Tianjin-Hebei and surrounding areas from January 1, 2015 to November 30, 2022 were selected, combined with the gravity model and Pearson correlation index, to construct a spatial correlation network of PM2.5 pollution in Beijing-Tianjin-Hebei and surrounding cities, and the overall characteristics of the network and the seasonal changes of the motif were analyzed statistically. The results showed that Xingtai, Shijiazhuang and Handan ranked top 3 in degree value, betweenness centrality and closeness centrality. They were at the core of the network and had strong spatial correlation with PM2.5 pollution in multiple cities, which played an important role in controlling the spatial spillover of PM2.5 pollution. The density and average degree of the four seasons correlation network of the motif were not different, but both were high. There was a strong spatial correlation between PM2.5 among cities, and the network density was the highest in winter. Shijiazhuang, Xingtai and Hengshui played an important role in the four seasons correlation network of the motif. For the cities in the core position of the spatial correlation network of PM2.5 pollution in Beijing-Tianjin-Hebei and surrounding cities, while strengthening their own PM2.5 control, policies should be formulated to reduce the spatial spillover effect of PM2.5 pollution on neighboring cities. According to the correlation of the motif in different seasons, corresponding collaborative governance policies should be formulated to strengthen the collaborative governance of urban PM2.5 pollution of the motif, while weakening the spatial correlation and spillover effect of PM2.5 pollution between them.

Study on the emission inventory and characteristics of air pollutants from inland and coastal ships in Guangxi
FAN Yongji, CHEN Xuan, XIE Hua, LU Yingyuan, LU Jiahui, WANG Xinyan, TANG Zhao
2023, 13(6): 2072-2080. doi: 10.12153/j.issn.1674-991X.20230219
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Based on the data such as the number and types of ships in Guangxi, and the power of ship engines, taking Guangxi Zhuang Autonomous Region as an example, the ship engine power method was used to establish the 2020 Guangxi inland and coastal ship emission list, and to explore the spatial distribution of the main air pollutant emissions from inland and coastal ships in Guangxi in 2020. The impact of ship air pollutant emissions on the atmospheric environment of Guangxi coastal port areas was simulated using an atmospheric diffusion model. The results showed that the dry cargo ships contributed 35.6% of the emissions from inland vessels, while the fourth-class ships accounted for 26.07% of the emissions. The contribution of tugboat emissions to coastal ships was 44.16%-49.33%, with emissions from main engines, auxiliary engines, and boilers being 52.39%, 21.43%, and 26.18%, respectively. Under different operating conditions, Coastal ship berthing conditions account for the highest percentage of SO2 emissions, while for other pollutants the highest emissions were observed in slow-driving conditions. In 2020, the average emission intensity of SO2, NOx, HC, and CO2 from ships in Beibu Gulf of Guangxi was 0.32, 2.14, 0.07, 121.93 t/km2, respectively.

Factors influencing the hygroscopicity of aerosols and the effects of hygroscopicity on aerosol optical properties
CHEN Jianhua, SHEN Yicheng, CHI Xiangyu, ZHU Shuang
2023, 13(6): 2081-2091. doi: 10.12153/j.issn.1674-991X.20230052
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The hygroscopicity is one of the important physicochemical properties of aerosols, which not only affects the climate through atmospheric radiation effects, but also has an important impact on atmospheric visibility. The concepts of aerosol particle size hygroscopic growth and scattered hygroscopic growth were introduced, the methods for measuring aerosol hygroscopic growth were summarized and the effects of particle size, chemical compositions, pollution conditions and mixing state on hygroscopicity were analyzed. It was found that the hygroscopic growth of aerosols could increase the water content of particles and affect the aerosol extinction capacity, thus affecting atmospheric visibility and aerosol radiative forcing. In the future, it was recommended to focus on aerosol hygroscopic growth at high relative humidity (>95%), strengthen vertical observation research on aerosol hygroscopic growth, and widely carry out the measurement and research on aerosol scattering hygroscopic growth under both hygroscopic and dehydrated conditions.

Removal efficiency of nitrobenzene and electricity generation by microbial fuel cell with algal biochar modified electrode
XU Daifei, WU Bingdang, YANG Jingjing, SHEN Zhengdong, HUANG Tianyin
2023, 13(6): 2092-2104. doi: 10.12153/j.issn.1674-991X.20230092
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Development of electrodes that facilitate microbial enrichment and excellent electrical conductivity is the key to improving the performance of microbial fuel cell (MFC). By acid and base activation way, the anode carbon felt (CF) with spirulina biochar (one type of algal biochar) was modified. The performance of MFC based on modified electrodes for electricity generation and pollutant conversion was explored with nitrobenzene as a representative of refractory pollutants, by detecting the electrochemical performance of the electrode and the pollutant degradation process. The results showed that the maximum MFC voltage in the modified CF electrode system (NaOH-AC700, 700 ℃ and modified by NaOH) could reach up to 670 mV, which was 26% higher than CF system, and the acclimation time was reduced from 7 days to 2 days. The modified electrode system could efficiently generate electricity while also degrading pollutants. The removal of nitrobenzene by the cathode in the modified CF electrode system was 99.9%, which was 22.1% higher than the unmodified CF electrode system, and the aniline production was increased by 123.3%. Microbial community analysis showed that the electrogenic microorganisms on the electrode surface were mainly Arcobacter and Pseudomonas, and the highest abundance of electrogenic microorganisms was found on the surface of NaOH-AC700/CF anode, thus facilitating the electrogenesis of MFC and the reduction of nitrobenzene.

FeS2 enhanced microbial fuel cell anode denitrification and electricity generation characteristics
GE Dandan, WU Bingdang, YANG Jingjing, XU Xiaoyi, WU Wei, HUANG Tianyin
2023, 13(6): 2105-2116. doi: 10.12153/j.issn.1674-991X.20230093
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In recent years, the research on enhanced microbial fuel cell (MFC) treatment of nitrogen-containing wastewater has attracted extensive attention at home and abroad. FeS2 was introduced into MFC anode to construct a FeS2-enhanced microbial fuel cell (Pyr-MFC) system for wastewater with different carbon to nitrogen ratios (C/N). The blank control group without FeS2 (C-MFC) was used as a control to explore its effects on nitrogen removal and electro-generation. High throughput sequencing, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to investigate the changes of microbial abundance, sulfur and iron elements in the system, and the mechanism of nitrogen removal under low C/N in FeS2-enhanced system was obtained. The results showed: 1) The denitrification efficiency and power generation density of Pyr-MFC were higher than those of the control group, the nitrate nitrogen removal rate was increased by 15.7%, and the maximum voltage increase was as high as 0.274 V. 2) NO3 -N removal rates of Pyr-MFC at different C/N ratios (4, 3, 2 and 1) were 100%, 97.8%, 58.4% and 49.7%, respectively, all higher than those of the control group, indicating that FeS2 could effectively reduce the dependence of the system on carbon sources. 3) The microbial community test results showed that FeS2 increased the species abundance of electrogenic microorganisms (Thauera, Thiobacillus and Geobacter) by about 9.43%. 4) The results of material transfer analysis showed that S provided electrons for the denitrification process, and Fe2+ enhanced the electron transfer and improved the electro-generation performance of the system as an electron shuttle.

Effect of immobilized bacteria and algae on enhanced nitrogen and phosphorus removal in bioretention tank
WANG Xiaoping, CHEN Yao, HUANG Ruting, CHEN Zhong
2023, 13(6): 2117-2125. doi: 10.12153/j.issn.1674-991X.20230125
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In view of the poor nitrogen and phosphorus removal efficiency of the traditional bioretention tank, a study was carried out on the leaching test of immobilized bacteria algae packing, and the nitrogen and phosphorus removal efficiency of biological retention ponds with different proportions of immobilized bacteria algae packing. The characteristics of nutrient release were studied by continuous leaching of immobilized bacteria algae packing in deionized water. G1 group accounting for 2/5 of the filler layer and G2 group accounting for 4/5 of the filler layer were set up to study and analyze the nitrogen and phosphorus removal effects under different submergence heights (0, 30, 60 cm) and drying periods. The results showed that total phosphorus (TP) and total nitrogen (TN) were not detected in the first 8 times leaching of immobilized bacteria algae packing, and immobilized bacteria algae packing was suitable as the improver of bioretention tank packing. With the increase of submergence height, the removal rate of ammonia nitrogen (NH3-N) and TN by bioretention tank increased. At the submergence height 60 cm, the average removal rates of NH3-N in G1 and G2 groups were 68.25% and 72.00%, and the average removal rates of TN were 64.20% and 68.70%, respectively. At the submergence height 0 cm or 60 cm, the removal rates of TP in G1 and G2 groups were 79.50% and 78.00%, 70.05% and 71.00%, respectively. At the submergence height 30 cm, the removal rate of TP in G2 group was the highest, reaching 86.00%. When the drying period was extended from 2 days to 8 days, the removal rate of NH3-N and TN decreased from the highest of 69.38% and 67.10% to the lowest of 55.13% and 57.70%, respectively, while the removal rates of TP increased from the lowest of 75.50% to 90.00%. The test results showed that the immobilized bacteria and algae filler could effectively improve the nitrogen and phosphorus removal performance of bioretention tank.

Advanced nitrogen removal efficiency of MSW leachate treated by SND with ASBR combined with SBBR process
QIAO Zhuangming, WEN Chunyan, TAI Jiafen, LI Jianping, KONG Weizhong, WANG Kai
2023, 13(6): 2126-2134. doi: 10.12153/j.issn.1674-991X.20230130
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Abstract:

In order to improve TN removal rate of leachate, the anaerobic sequencing batch reactor (ASBR) combined with the improved sequencing batch biofilm reactor (SBBR) process was used to treat the actual municipal solid waste (MSW) leachate with chemical oxygen demand (COD) of (5 700±500) mg/L and TN concentration of (210±50) mg/L. The results showed that the effluent of ASBR entered SBBR reactor for deep denitrification, and the main function was to adjust C/N of subsequent SBBR influent, and the removal rate of COD in leachate was 90%. C/N was the key to determining the nitrogen removal efficiency of SBBR. After adjusting the influent C/N to 4.8, under the action of biofilm, the deep denitrification of MSW leachate could be achieved only by anaerobic stirring and simultaneous nitrification and denitrification (SND) in the aerobic stage. The effluent total nitrogen concentration was lower than 10 mg/L, and the cycle running time was shortened from 24 hours on the 54th day to 5.6 hours. The best treatment effect could be achieved after 103 days of domestication and start-up of the whole system. The concentrations of COD, NH4 +-N and TN in the effluent were (380±10), (1.0±0.5) and (5±5) mg/L, respectively, and the removal rates were more than 93%, 99% and 95%, respectively. Through high-throughput sequencing analysis, the relative abundance of Proteobacteria and Bacteroides in the system was high, with 55.11% and 21.32%, respectively. In the system, the abundance of Firmicutes with denitrification accounted for 2.81%, which may be the key to achieving an excellent denitrification effect in SBBR. At the genus level, the bacteria with denitrification function in the system were mainly Thauera and Limnobacter, accounting for 15.22% and 2.84%, respectively. Their existence may be one of the main reasons for the good effect of the system SND. The system achieved deep denitrification of leachate without adding any carbon source and had high nitrogen removal efficiency, which provided an effective way for MSW leachate to meet the discharge standard of total nitrogen.

Preparation of modified sodium alginate gel material and its chromium removal performance
ZHANG Yujia, WANG Xingrun, WANG Lei, LIU Hai, YAN Xianghua
2023, 13(6): 2135-2142. doi: 10.12153/j.issn.1674-991X.20230030
Abstract(140) HTML (78) PDF(5726KB)(33)
Abstract:

Sodium alginate gel (SA) material has problems such as unsatisfactory treatment effect and low utilization rate in the treatment of chromium-containing wastewater. In order to solve these problems, sodium alginate was used as raw material, and gel balls (SA-Ba) were prepared by gel embedding method loaded with Ba2+, and polyethylene glycol was added for covalent mixing and modification to obtain polyethylene glycol modified barium alginate gel material (PEG-SA-Ba). Compared with the traditional calcium alginate (SA-Ca) gel ball, the chromium removal effect of the three gel ball materials and the effects of experimental parameters such as pH, initial Cr(Ⅵ) concentration, and PEG-SA-Ba dosage on the chromium removal effect of PEG-SA-Ba materials were investigated, and the samples were characterized by scanning electron microscopy (SEM) and Fourier infrared spectroscopy (FTIR). The results showed that: SA-Ba crosslinked with sodium alginate and Ba2+ greatly improved the chromium removal effect of SA, and the chromium removal amount was more than 800 times that of SA-Ca; the covalently modified PEG-SA-Ba provided more active sites for the adsorption of Cr(Ⅵ), and the chromium removal capacity was increased by 4.38 mg/g compared with that without modification. With the increase of pH, the removal rate of Cr(Ⅵ) by PEG-SA-Ba also continued to increase; the chromium removal capacity at pH 6 was 16.24 mg/g higher than that at pH 2, and when pH exceeds 8, the structure of the gel ball was unstable and easy to cause ion leakage, resulting in precipitate formation outside the gel ball. The chromium removal capacity of PEG-SA-Ba increased with the increase of Cr(Ⅵ) concentration and decreased with the increase of dosage. SEM and FTIR characterization verified that the Ba2+ loading was successful and the crosslinking effect of polyethylene glycol and sodium alginate was good. Finally, the discussion found that PEG-SA-BA gel ball materials had obvious advantages in preparation cost and method, saving more than 99% and 24% of material costs compared with SA and SA-Ba, respectively.

Study on efficient arsenic removal performance and mechanism of natural ferromanganese ore
TIAN Zhouyang, ZHENG Qian, DU Xiaoli, CHEN Cheng, LI Chuanwei, TU Shuxin
2023, 13(6): 2143-2153. doi: 10.12153/j.issn.1674-991X.20230058
Abstract(123) HTML (63) PDF(3144KB)(32)
Abstract:

In order to develop an efficient and inexpensive material for As(Ⅲ) removal from water, natural ferromanganese ore (NFM) was used as adsorbent. Kinetic, thermodynamic, isothermal adsorption and adsorption/desorption experiments were conducted to evaluate the adsorption performance of As(Ⅲ). The mechanism was analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and the adsorption characteristics were compared with those of iron-manganese binary oxide (FMO), birnessite (Bir), and goethite (Goe). The results showed that NFM was mainly composed of manganese oxide and iron oxide, with a Fe-Mn molar ratio of 6∶1, the specific surface area of 280.4 m2/g, and a saturation adsorption capacity of 48.3 mg/g for As(Ⅲ). The Freundlich model and the pseudo-second order kinetic model could better fit the adsorption process of NFM. XPS and other characterization analyses indicated that the synergistic effect of adsorption and oxidation of NFM was the key factor for As(Ⅲ) removal. Among them, manganese oxides exhibited excellent oxidation of As(Ⅲ), while iron oxides had strong adsorption.

Research progress on the degradation of environmental organic pollutants by activated peracetic acid technology
WANG Huifeng, GUO Yanfei, GUO Zhuang, HUANG Yihan, XU Dongyao, WEI Jian
2023, 13(6): 2154-2164. doi: 10.12153/j.issn.1674-991X.20230056
Abstract(355) HTML (86) PDF(883KB)(93)
Abstract:

The frequent detection of emerging contaminants poses a potential risk to ecosystems and human health, such as antibiotics and endocrine disruptors in the environment in recent years. The research and development of efficient and stable organic pollutant control technology is a research hotspot in the current environmental field. Taking the advanced oxidation technology of activated peracetic acid (PAA) as the research example, the effectiveness of activated PAA through transition metals, carbon materials and their composites, and their degradation mechanism of organics were discussed, with emphasis on the degradation mechanism of free radicals (organic radicals, hydroxyl radicals) and non-radicals (singlet oxygen, high-valent metal-Oxo species, electron transfer and surface complexes). In addition, the application effect of activated PAA in wastewater, soil or sediments, groundwater, and other environmental media for the degradation of organic pollutants was summarized. Finally, future research focuses were proposed, including developing the catalysts of activated PAA with efficiency and stability, strengthening the mechanism exploration of activated PAA to degrade organic pollutants in soil and sediment, and deepening the application studies of combined treatment technologies.

Research advances and prospects of source separation and recycling technologies of toilet black water
LIU Cunhui, YANG Wenjing, ZHANG Xiaomei, LIANG Jinsong, CHEN Le, FANG Wei, WU Zhen, ZHANG Panyue
2023, 13(6): 2165-2173. doi: 10.12153/j.issn.1674-991X.20221262
Abstract(146) HTML (77) PDF(2255KB)(47)
Abstract:

Toilets are the basic facilities of daily life, playing an important role in improving human living environment. Toilet black water mainly consists of feces and urine with a large amount of organics and nutrients such as nitrogen and phosphorus, and its source separation and recycling are becoming an urgent environmental and technological issue. Through literature research and analysis, the main technical route of toilet black water source separation and recycling was sorted out. Focusing on the source separation of toilet black water, the new developed source separation equipment and their application scope were summarized. Based on the characteristics of fecal wastewater and urine, the research progress of main treatment and resource recycling technologies of different wastewater after source separation were analyzed systematically, and the fundamental tasks of pollution control and efficient recovery of carbon, nitrogen and phosphorus were revealed. Finally, the challenges on the assessment and green development of toilet black water source separation and recycling technologies, reasonable combination of multiple technologies, and centralized and intelligent operation and management were summarized and relevant suggestions were proposed, according to the current research and engineering application. This study aimed to provide theoretical basis and key reference for promoting the large-scale application of suitable source separation and recycling technologies of toilet black water in accordance with local conditions.

Spatial and temporal distribution characteristics of phycobiliprotein in Dianchi Lake and analysis of its influencing factors
LIU Ping, WEI Wei, YANG Junhui, LI Jianwen, ZUO Limei, MENG Rui, DUAN Pingzhou, JIAO Lixin
2023, 13(6): 2174-2183. doi: 10.12153/j.issn.1674-991X.20230146
Abstract(139) HTML (74) PDF(15227KB)(31)
Abstract:

Phycobiliprotein has important economic value. It can be extracted and processed from algae to realize the reduction and recycling of algae sludge waste. Aiming to clarify the spatial and temporal distribution characteristics of phycobiliprotein in Dianchi Lake and its influencing factors, four samples were collected by seasons in 2022. Upon establishing the detection method of phycobiliprotein, the spatial and temporal variation characteristics of phycobiliprotein in four areas of Dianchi Lake, namely Caohai, northern Waihai, central Waihai and southern Waihai were analyzed. Based on ArcGIS, the time and spatial sequence grid data chart of phycobiliprotein concentration in Dianchi Lake was established. The results showed that the phycobiliprotein concentrations in Dianchi Lake presented the distribution characteristics of summer>autumn>spring>winter in time, the rule of northern Waihai>central Waihai>southern Waihai>Caohai in space, and the concentration of phycobiliprotein was low with phycocyanin as the main component. Through the statistical analysis of various influencing factors, it was found that there was a strong linear correlation between phycocyanin concentration and TP and BOD5 (P<0.01). The correlation between phycoerythrin and nutrients was low. The increase of phycobiliprotein in turn would affect pH, DO and transparency of the water body (P<0.05). The influencing factors of phycobiliprotein were discussed in different areas, and it was concluded that nitrogen and phosphorus were the main driving factors of phycobiliprotein distribution, which might be affected by hydraulic conditions and algae population types. Although Caohai had the highest average concentration of TN and TP, its N/P value was too high, and the blue-green algae community was replaced by green algae. At the same time, its phycobiliprotein concentrationd was the lowest. While the northern Waihai had long hydraulic retention time and low N/P value, resulting in a higher proportion of blue-green algae population and the highest concentration of phycobiliprotein. N/P of Dianchi Lake water body in spring and winter was significantly higher than that in summer and autumn, which was one of the main reasons for the higher concentration of phycobiliprotein in summer and autumn.

Study on the differences in the remediating effects of different formulations of bacterial agents on black and odorous water bodies and sediments
CHEN Shijie, WANG Kai, TAN Yong, LIU Siyun, ZHOU Jinyan, PEI Changying, HUANG Mingtao, LI Bolin
2023, 13(6): 2184-2191. doi: 10.12153/j.issn.1674-991X.20230272
Abstract(270) HTML (93) PDF(2476KB)(74)
Abstract:

In order to explore the remediation effect of different bacterial agents on black and odorous water bodies, and reveal the changing law of microbial communities during the research process, different formulations of bacterial agents were used to restore black and odorous water bodies, and the effects of different bacterial agents on overlying water, sediment and microorganisms were discussed. The results showed that the pH of the overlying water in the bacterial agent group was slightly higher than that before the experiment. DO concentration in the overlying water of the chemical-composite microbial agent group was slightly lower than that of the blank group (6.95 mg/L), and the removal rates of NH4 +-N and TP in the overlying water reached 86.60% and 66.07%, while the removal rates of volatile sulfur (AVS) and organic matter in the sediment reached 79.20% and 52.71%, respectively. The removal effects were significantly better than other experimental groups. High-throughput sequencing showed that nitrifying bacteria、denitrifying bacteria and organic matter degrading bacteria in the sediment of the microbial inoculum group had high relative abundance, and the relative abundance of a genus under Vicinamibacterales in the chemical-compound microbial inoculum group was significantly higher than that in other experimental groups (1.07%-2.18%). The results of this study indicate that the chemical composite microbial agent has a good remediation effect on black and odorous water bodies.

Effect of Fe2+-PDS conditioning-horizontal electro-dewatering process on dewatering performance of dredged sediment
ZHU Shuyuan, WANG Yili
2023, 13(6): 2192-2203. doi: 10.12153/j.issn.1674-991X.20230045
Abstract(101) HTML (42) PDF(5806KB)(24)
Abstract:

Aiming at the problem of restricting the subsequent disposal of dredged sediment with high water content, Fe2+-perdisulfate (PDS) conditioning - horizontal electro-dewatering (HED) process was used to treat sediment samples. The operating parameters (Fe2+ and PDS dosage, voltage, power-on time) of Fe2+-PDS conditioning - HED process were optimized through the response surface method (RSM), and the variations in the morphology and properties of the sediment at the conditioning stage, as well as the changes in the water content and organic components of the sediment at various stages of the process (conditioning, gravity settling, HED) were analyzed. The results showed as follows: 1) The optimal dosage of Fe2+ and PDS for the conditioning stage was 4 mg/g (TSS) and 10 mg/g (TSS), respectively. The optimal power-on time and voltage of the HED stage were 80 min and 45 V, respectively. Under the above parameters, the water content of dredged sediment decreased from 88.55% to 55.15%. 2) At the conditioning stage, the bound water content of sediment decreased from 0.44 g/g (DS) to 0.28 g/g, the total amounts of proteins and polysaccharides in extracellular polymeric substances (EPS) increased, while the fluorescence intensity of protein-like substances and soluble microbial byproduct-like materials (SMBP) in Slime layer decreased. The total fluorescence intensity in the tightly bound EPS (TB-EPS) increased to 12.40×107 AU·nm2. At the HED stage, the effect of electric field led to further release of the organic matters in the sediment around the cathode region, and the fluorescence intensity of SMBP in each layer of EPS around the cathode region increased significantly. 3) SO4 · produced at the conditioning stage could oxidize and crack the microbial cells in the sediment and release the intracellular contents into EPS, and the simultaneous changes in water distribution and EPS components of the sediment occurred. Fe(Ⅲ) produced in situ altered the floc structure of the sediment through coagulation, thus contributing to the improvement of the dewatering performance of the sediment. The research showed that Fe2+-PDS conditioning-HED process could effectively reduce the water content of the dredged sediment, so as to provide technical support for the treatment of dredged sediment.

Heavy metal enrichment characteristics and medicinal health risk assessment of dominant plants around a mining area in Henan Province
CHANG Xiangling
2023, 13(6): 2204-2212. doi: 10.12153/j.issn.1674-991X.20221252
Abstract(208) HTML (102) PDF(1634KB)(46)
Abstract:

Screening medicinal plants suitable for growth in abandoned mining areas and evaluating their heavy metal enrichment ability and medicinal risks can provide the scientific basis for reducing the risk of heavy metal pollution in mining areas and improving land use efficiency. Nine dominant medicinal plants naturally growing at the top of the slope of a mining area in Henan Province were selected, and the whole plants and rhizosphere soil of 0-10 cm were collected. Using transport coefficient, bioenrichment coefficient, hazard quotient method and human health risk assessment model, the enrichment and transfer characteristics of each plant to the nine heavy metals were analyzed, and the potential health risks of medicinal plants to the human body were studied. The results showed that the proportion of available Cd and As in the rhizosphere soil was more than 20%, indicating a moderate risk. The contents of As and Cu were higher in Conyza canadensis; the contents of Cr and Ni were higher in Imperata cylindrica, Conyza canadensis and Setaira viridis; the contents of Pb were higher in Imperata cylindrica, Conyza canadensis and Lonicera japonica. Artemisia argyi had a strong enrichment ability of Cr, and Lonicera japonica had a strong adsorption ability of Cd, As, Cu, Pb, Hg, Ag and other elements in the soil. At the same time, Artemisia argyi and Lonicera japonica had a low degree of harm to the human body. Conyza canadensis and Miscanthus floridulus had a strong adsorption and transport ability of Cd, As, Cu, Pb, Hg, Ag and other heavy metals in soil, but they had great risks to human health. Salsola collina and Rhus chinensis had a weak adsorption and transport ability of heavy metals such as Cd, As, Cu, Pb, Hg, Ag, and they were tolerant to heavy metals, so they belonged to plants with low accumulation of heavy metals. In the future research and ecological construction, it was necessary to select suitable plants for cultivation and restoration for specific purposes.

Environmental risk assessment of humic acid modified dealkalized red mud
LI Da, XU Kangning, GUO Fei
2023, 13(6): 2213-2220. doi: 10.12153/j.issn.1674-991X.20230047
Abstract(169) HTML (90) PDF(2328KB)(39)
Abstract:

Untreated accumulation of red mud that has been treated with acid mine drainage can cause serious harm to the environment. Soil improvement is a feasible method to consume it on a large scale. Humic acid is acidic and is a large molecular organic substance widely present in nature, and its effect on soil restoration and improvement is significant. To study the environmental risk of humic acid modified dealkalized red mud, humic acid combined with dealkalized red mud experiment was carried out. The physicochemical properties of the dealkalized red mud and its leachate were analyzed, and the leaching risk of dealkalized red mud after adding humic acid was evaluated. The results showed that the best effect of improving dealkalized red mud by humic acid with a mass percentage (humic acid/red mud) of 10% was achieved. Adding 10% mass percentage of humic acid could reduce pH of dealkalized red mud from 9.1 to around 7.8. It could increase the absolute value of the electric potential (Zeta potential) of dealkalized red mud from 20 to 28 at higher pH. The fulvic acid substances in humic acid would gradually transform into more stable humic acid substances. Humic acid could reduce the concentration of metal ions in the leachate of dealkalized red mud and had a positive effect on fixing metal ions in red mud. In summary, humic acid could improve dealkalized red mud and reduce its environmental risk.

Adsorption efficiency and mechanism of uranium in seepage of uranium tailing pond using biochar prepared from oxytetracycline fermentation residues at high temperature
NIU Ziming, CAO Xinran, PENG Guowen, LI Liang, DAI Lichun
2023, 13(6): 2221-2228. doi: 10.12153/j.issn.1674-991X.20230133
Abstract(98) HTML (51) PDF(6286KB)(25)
Abstract:

Oxytetracycline fermentation residues (OFR) were used to prepare biochar under different temperatures (from 300 to 900 ℃ with an interval of 100 ℃) for uranium adsorption and removal in the wastewater, and the adsorption efficiency and mechanism were studied. The results showed that as the rise of temperature, the surface function groups of OFR biochar, prepared at different temperatures, were decreased gradually and the crystal morphology of Ca was transformed from CaC2O4 (300-400 ℃) to CaCO3 (500-700 ℃) and CaO (800-900 ℃), which leaded to the changes of removal efficiency. When the temperature was raised to 800-900 ℃, the biochar adsorption achieved more than 98% removal efficiency of uranium in seepage of a tailing pond in the South of China in 10 min. Further studies found that more than 98% of uranium could be removed under the condition of wide range of pH (4.0-9.0) and initial uranium concentration (0.8-3.0 mg/L), and the supernatant after treated was much lower than the limit of discharge standard stipulated by radiation protection and radiation environment protection in uranium mining and metallurgy. Therefore, OFR biochar prepared at high temperature showed a good application prospect in in-situ treatment of uranium tailings drainage.

Typical elements distribution in water-based drilling cuttings from Hainan Province and their effects on groundwater after using as a pave in drilling site
BAO Weilei, LUO Biao, YAO Guangyuan, SHU Huixiu, ZHOU Qi, SUN Yingjie, HUANG Qifei
2023, 13(6): 2229-2239. doi: 10.12153/j.issn.1674-991X.20230082
Abstract(153) HTML (93) PDF(1718KB)(35)
Abstract:

The use of water-based drilling cuttings as a pave in drilling site is an important way for the reuse of the waste. However, the environmental impact from the reuse has not been fully understood due to the variation in the contents of elements in water-based drill cuttings from different regions. The distribution and leaching characteristics of typical elements in the water-based drilling cuttings from the drilling platforms of five typical oil and gas fields in Hainan, China, were investigated. Further, the environmental impacts on groundwater from the reuse were assessed. The results indicated that the concentrations of Ni, As, Se, Sb, Pb, Hg, Tl, Mo and Ba in the investigated water-based drilling cuttings did not exceed the corresponding risk screening values for Class Ⅱ land specified in Soil environment quality: risk control standard for soil contamination of development land (GB 36600-2018); and the concentrations of all elements, excluding Tl, were related with the sampling depths significantly. Compared with the limits of Class Ⅲ set in Groundwater Quality Standard (GB/T 14848-2017), the exceedance rates of Pb, Tl and As in the leachate reached 36.5%, 16.5% and 16.5%, respectively. Among the investigated elements, arsenic had the highest leaching rate (35.7%). The results of risk estimation based on Texas model and on-site measurement of the groundwater below the pave in drilling site suggested that the use of water-based drill cuttings as a paved surface in drilling site was safe, with the concentrations of all tested items not exceeding the Class Ⅲ limit specified in GB/T 14848-2017.

Preparation and application of an immobilized bio-filler
LI Ping, LIU Jia, LU Shaojie, TAO Min, HAN Yueyang, LIANG Wenjun
2023, 13(6): 2240-2247. doi: 10.12153/j.issn.1674-991X.20230054
Abstract(290) HTML (77) PDF(6456KB)(37)
Abstract:

A kind of immobilized bio-filler (BM filler) was prepared by immobilization technology, combining polyvinyl alcohol (PVA) and sodium alginate (SA) to construct a gel skeleton, introducing activated carbon (AC), CaCO3, and composite bacterial powder, and optimizing the particle size of AC added to BM filler. The removal effect of the biological trickling filter (BTF) packed with the filler was investigated using ethylbenzene as the target pollutant. When the added AC was 100 mesh, the specific surface area of BM filler reached 57.46 m2/g with the highest mechanical strength and the best degradation effect on ethylbenzene. The results of physicochemical properties analysis showed that the filler had a dense three-dimensional internal mesh structure, with good hydrophilicity and adsorption capacity, and a large number of hydrophilic groups such as —OH and —COO on the surface, and the adsorption of ethylbenzene was 2.9 times higher than that of polyurethane sponge (PU) filler under the same conditions. Meanwhile, the filler had good acid resistance and still maintained a high degradation activity when pH dropped to 1. The BTF packed with BM filler could be started up in 6 days; after 7 days of stagnation, the removal efficiency recovered to 100% in 5 days; and ethylbenzene could still be completely removed at the inlet ethylbenzene concentration of 800-900 mg/m3 and the empty bed residence time (EBRT) of 33 s. Compared with the BTF packed with PU filler, the BTF packed with BM filler showed superior performance.

Identification of key areas for ecological restoration of territorial space based on ecological security pattern: a case of five plateau lake basins in central Yunnan
CHEN Xiangbiao, DING Wenrong
2023, 13(6): 2248-2260. doi: 10.12153/j.issn.1674-991X.20221153
Abstract(543) HTML (456) PDF(20286KB)(107)
Abstract:

In order to explore the identification methods of key areas of ecological protection and restoration of land space in lake basins, five plateau lake basins in central Yunnan (Dianchi Lake, Fuxian Lake, Xingyun Lake, Qilu Lake and Yangzong Lake) were taken as research examples, the habitat quality model, morphological spatial pattern analysis model, landscape connectivity model, minimum cumulative resistance model and circuit theory were comprehensively used to construct a regional ecological security pattern, identify ecological pinch points, ecological obstacle points and ecological break points, and clarify the key areas of ecological protection and restoration of land space in lake basins. The results showed that: the ecological source areas of the five major plateau lake basins in central Yunnan accounted for 23.43% of the total land area of the whole basins, including 33 ecological source patches, mainly distributed in five plateau lake basins and mountain and forest lands, and the ecological corridors were identified with a total length of 488.85 km and discrete distribution in a network connection. The key areas of ecological restoration in the watershed were identified, including 93 ecological pinch points with an area of 119.17 km2, mainly distributed in Dianchi Lake basin, 62 ecological obstacle points in urgent need of protection and restoration with an area of 41.96 km2, the overlapping area of ecological pinch points and ecological obstacle points of 17.40 km2, and 77 ecological break points, with the densest distribution in Dianchi Lake basin. Combined with the spatial distribution characteristics and land use status of various key areas of ecological protection and restoration in the basins, the directions of ecological protection and restoration improvement were proposed. This method could effectively identify the areas to be repaired by the ecological network, and provide technical support for the ecological protection and restoration of land space.

Evaluation of salt tolerance of eight coastal afforestation species in Jiangsu Province
ZHENG Xu, ZHAO Wenjing, LIU Xingman, ZHANG Kang, BIAN Jian, YAN Hongmin, WANG Xiaoxiao, TANG Luozhong
2023, 13(6): 2261-2270. doi: 10.12153/j.issn.1674-991X.20230061
Abstract(168) HTML (82) PDF(1731KB)(26)
Abstract:

In order to understand the salt tolerance of typical tree species in the coastal areas of Jiangsu Province, the coastal area of Dafeng District, Yancheng City was chosen as the research area, and eight afforestation tree species such as Taxodium 'Zhongshanshan', Ulmus pumila, Taxodium distichum, Ulmus parvifolia, Triadica sebifera, Salix ohsidare, Broussonetia papyrifera and Melia azedarach were chosen as the study objects. The soil salt content and its relationship with the survival rate, and the annual growth of diameter at breast height (DBH) and height of trees in different afforestation sites were studied. The comprehensive evaluation of the salt tolerance of each tree species was carried out by using the membership function analysis method. The results showed that the soil salt content of forty-eight sample plots ranged from 0.4 to 11.9 mg/g, and there were significant differences among different plots. At the sample plots with high soil salt content, the salt content of the upper soil was generally higher than that of the subsoil, which showed a typical salt accumulation in the topsoil. The survival rate, DBH and height of the eight tree species were negatively correlated with the soil salt content. According to the evaluation results of salt tolerance of eight tree species, the salt tolerance of eight tree species was as follows: Ulmus pumila > Melia azedarach > Taxodium distichum > Triadica sebifera > Ulmus parvifolia > Taxodium 'Zhongshanshan' > Salix ohsidare > Broussonetia papyrifera. Ulmus pumila and Melia azedarach could tolerate about 6 mg/g of the soil salt content; Taxodium distichum, Triadica sebifera, Ulmus parvifolia and Taxodium 'Zhongshanshan' could tolerate about 4 mg/g of the soil salt content; and Salix ohsidare and Broussonetia papyrifera could only tolerate about 3 mg/g of the soil salt content. Therefore, Ulmus pumila and Melia azedarach could be planted in coastal areas with high salt content, while Taxodium distichum, Triadica sebifera, Ulmus parvifolia and Taxodium 'Zhongshanshan' could be planted in coastal areas with medium salt content, and Salix ohsidare and Broussonetia papyrifera could only be planted in coastal areas with low salt content.

Effect of soil quality on physical and chemical properties of vegetation concrete and plant growth
LIU Daxiang, SONG Qiangbing, LONG Lijun, YANG Yueshu, DING Yu, XU Wennian
2023, 13(6): 2271-2278. doi: 10.12153/j.issn.1674-991X.20230194
Abstract(284) HTML (94) PDF(2295KB)(47)
Abstract:

Vegetation concrete is widely used in ecological restoration of exposed slopes at present. Different soil types have great differences in substrate strength and water retention, which affects plant growth. The essence of different soils is the difference of soil particle gradation, where sand particles form a skeleton with coarse particles, and fine particles are filled and bonded. Indoor maintenance and outdoor potted plants were combined to explore the effects of soil quality (silty sand, low liquid limit silty soil and low liquid limit clay) on the physical and chemical properties of vegetation concrete and the growth of ryegrass. The results showed that the permeability coefficient was positively correlated with large pore size and total porosity, and also related to cement hydration. Saturated water content was positively correlated with total porosity and capillary porosity. Water evaporation rate was negatively correlated with capillary porosity and water content, and cohesion was related to gradation and cement cementation. The internal friction angle was positively correlated with coarse particles, which was related to roundness and cement hydration. Nitrate content and nitrate leaching rate were related to capillary pores and substrate compactness. Ammonium nitrogen content and ammonium nitrogen leaching rate were related to capillary pores and clay content. The polarizing microscope was used to explain the reasons why different soil properties affected the macro-characteristics of vegetation concrete from the perspective of meso-structure. Based on the above index analysis and practical experience, it was concluded that vegetation concrete made of silty sand was more conducive to plant growth, and all the indexes were within the acceptable range.

Research progress on ecosystem services of slope hedgerows
CHEN Yanmei, GUO Wenfang, GAO Jixi
2023, 13(6): 2279-2288. doi: 10.12153/j.issn.1674-991X.20230251
Abstract(209) HTML (98) PDF(583KB)(41)
Abstract:

Slope hedgerow has become an important bioengineering technology for slope improvement due to its low cost and remarkable ecological function. The relevant research results on the slope hedgerow technology were compiled and, based on a new perspective of ecosystem services, the concept and classification of slope hedgerows, the technical points of species selection and spatial structure were elaborated. The support services, regulation services, and supply services, etc. provided by slope hedgerows were explored, and the existing issues in the current study were analyzed. In the future, the research on the theoretical basis and evaluation methodology system about ecosystem services of slope hedgerows should be strengthened, the microscopic mechanisms of ecosystem services of slope hedgerows should be explored, the comprehensive technical system of slope hedgerows species selection, spatial allocation and management should be improved, and the scope of trial planting and promotion efforts should be gradually increased.

Research on the verifying method of allowable discharge in printing and dyeing industry based on different discharge reduction scenarios: a case study in Nantong City of Jiangsu Province
LI Xueping, WANG Xiaohui, WU Peng, JIANG Rongrong, ZHANG Tingting, BAI Zhenzhi, CHAI Xilong
2023, 13(6): 2289-2298. doi: 10.12153/j.issn.1674-991X.20230421
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Abstract:

In view of the need for reasonable determination of allowable emission limits in China's emission permit system, 88 printing and dyeing enterprises in Nantong City were taken as the research object, and the traditional discharge performance accounting methods and baseline setting methods were adopted to determine the discharge performance of printing and dyeing enterprises based on the actual emission level. Meanwhile, the allowable limits of printing and dyeing enterprises were determined under three scenarios of strong, medium and weak discharge reduction from a hypothetical quantitative perspective. The discharge reductions of chemical oxygen demand (CODCr), ammonia nitrogen (NH3-N), total nitrogen (TN) and total phosphorus (TP) under the three scenarios were projected. The results showed as follows: 1) The maximum average value of the actual discharges of CODCr, NH3-N,TN and TP in 88 printing and dyeing enterprises did not exceed 34.46% of the allowable discharges, the permissible discharge of major water pollutants in Nantong printing and dyeing enterprises had great potential for verification and reduction. 2) 95% and 99% quantile values of the 4 pollutants from 88 printing and dyeing enterprises obtained by the quantile value method were equivalent to the corresponding performance values of P95 and P99 obtained by the normal distribution analysis method. 3) Comparing the numerical reference lines obtained by the quantile value method and the normal distribution analysis method with the actual average and standard performances of 88 printing and dyeing enterprises, it was found that as to the four pollutants, at least 71.59% of the enterprises were below the average performances, 17.05% of the enterprises were between the average performances and the 95% quintile, and 2.33% of the enterprises were between the 95% quintile and the standard performances. 4) Based on the three discharge reduction scenarios of weak, medium, and strong, the projected discharge reductions for four pollutants were 2.08%-5.99%, 11.73%-20.05% and 23.24%-36.04%, respectively.