Volatile organic contaminants (VOCs) are among the most frequently detected pollutants in groundwater of industrial contaminated site in China. VOCs are commonly found entrapped as non-aqueous phase liquids (NAPL) in the soil pores of subsurface and become persistent sources of groundwater pollution with higher risk of environment and health. Monitoring natural attenuation (MNA) technology has gained more and more attention in recent years due to its low cost, small disturbance and no secondary pollution. The current frequently applied approaches to assess the ability of natural attenuation of aquifer contaminants were summarized both abroad and at home. The case studies of natural attenuation assessment for 60 sites showed that trend analysis of contaminant concentration and hydro-geochemical indicator methods were the most frequently applied methods. For a simple contaminated site, the in situ biodegradation process could be accurately and reliably assessed by the above two methods. For a complex contaminated site, the integration of different technologies, such as microcosm, microbiological analysis and stable isotope analysis, was recommended for a more robust and reliable characterization of in situ degradation process. In recent years, Stable Isotope Analysis method had gained increasing attention for assessing natural attenuation of organic contaminants in aquifers due to its potential to indicate contaminants degradation pathway and to quantify the rate of natural attenuation.
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