Isotope method to identify and quantify organic pollutant biodegradation during natural attenuation monitoring

Abstract

BACKGROUND: Organic pollution poses a huge threat to the environment and human health. It is necessary to evaluate the degree of the physical and chemical reactions of organic pollutants and to clarify the time and space laws of their degradation, so as to guide the pollution remediation work. This study aimed to evaluate the biodegradation process of typical pollutant components (benzene (BZ) and dichloroethylene (DCE)) in groundwater in a study area using the 13 C compound specific isotope analysis, and to evaluate the differences in calculated degradation rates by using theoretical results. RESULTS:The field-measured spatio-temporal concentrations of BZ and DCE and the isotope data of 13 C and 14 C in groundwater proved the leading role of microorganisms in the degradation process. The BZ degradation extent (92.11%) was higher than that of DCE (83.67%) within 1 year, and indoor experiments verified this result. Microbial degradation extents calculated by 13 C isotope were 85% and 79%, respectively. The first-order degradation kinetic model verified the reasonability of the degradation results calculated by 13 C isotope; the deviations of the degradation extents calculated by field-measured data and 13 C isotope are both <10%. In addition, BZ was more likely to degrade upstream of the groundwater flow path. CONCLUSION: Biodegradation was the most important attenuation method of BZ and DCE, but there were differences in the degradation abilities of BZ and DCE by biological action, and BZ was preferentially degraded over DCE in the groundwater flow path.