| As an emerging organic pollutant with toxic effects such as mutagenesis, pathogenesis and carcinogenesis,1,2,3-trichloropropane (TCP) has attracted more and more attention in developed conutries. But its behavior and relevant mechanism in soil and groundwater haven't been undstand comprehensively, accompanied with short of remediation and control technologies. In China, this pollutant even hasn't aroused people's concern. This study tries to understand this synthetic organic pollutant's environmental behavior and its attenuation law in field groundwater, for the purpose of managing, preventing and remediating its pollution scientifically, and promoting public's concern on this contanminant in regional investigating of groundwater pollution in our country.This study is accomplished after a geological survey programme to investigate a contaminated site with chlorohydrocarbon pollution. TCP is the most important contanminant in this site. Dynamics analysis of TCP's migration and suitability analysis of its micro-biological degradation in groundwater are the focused research contents, followed the research difficulty of identification of TCP's micro-biological degradation. Based on a large number of data about geologic structure, dynamic field, hydrogeochemistry and contamination status of soil and groundwater of the polluted site, TCP's environmental behavior in groundwater is representated by dynamics analyzing, and then dynamics mode of TCP's migrating in groundwater is proposed. Following these, objective possibilities of TCP's biodegradation in field groundwater is analyzed from two objective conditions: oxidation-deoxidation environment and microorganism's distribution, and then the existence of TCP's biodegradation is demonstrated by two ways:characteristic index of hydrogeochemistry and compound-specific stable isotope of carbon, applying conventional approach, such as hydrodynamics and hydrogeochemistry, and new technologies, such as sequencing analysis of microorganism and compound-specific stable isotope. At last, TCP's natural rate of decay and biodegradation rate are estimated. The main results are listed in the following: (1) Basing on the dynamics analysis and estimation, the environmental dynamic mode of TCP's migrating acted by groundwater convecting mainly and attenuation acted by biochemistry mainly is proposed, followed a preliminary detennination of the existence of TCP's biochemical degradation in this field groundwater.(2) Both oxidation-deoxidation environment analysis and distribution characteristics of microorganism indicate that field groundwater environment is suitable for biodegradation in this site. The field groundwater environment presents medium and strong reduction, providing the basic environmental condition for TCP's reductive biodegradation. Microorganism's distribution with higher bacterial abundance but lower diversity closing to pollution source area indicates that polluted groundewater have some tendency to be more suitable for optional microbial community. Besides, some anaerobic bacterias, pseudomonas, burkholderia, ralstonia, rhodococcus, dehalogenimonas, which are suspected to be able to degrade TCP in former's study are found in the field groundwater.(3) The distribution of both characteristic index of hydrogeochemistry and ?13C prove the existence of TCP's biodegradation. Following the analyzing of hydrogeochemistry, we can see that a series of reduction biodegradation, oxygen reduction, nitrate redauction, ferro-manganese reduction and sulfate reduction, have been existed orderly in shallow groundwater, but only the former two reduction in deep groundwater. Distribution of TCP's ?13C in field groundwater presents decreasing tendency both to downstream far from pollution source area and to deep, which also demonstrates that the existence of TCP's biodegradtion, and the lower degradation rate of deep groundwater than shallow.(4) Natural attenuation rate of TCP in this field groundwater is estimated applying trend line method, and the rate in shallow groundwater is 0.002253 d-1, in deep is 0.002195 d-1. The max biodegradation rate of TCP, estimated applying Buscheck-Alcantar method, are 0.001894 d-1(0.6912a-1) in shallow and 0.002899 d-1 (0.6892 a-1) in deep. The estimated results indicate that TCP's attenuation is slow, and its slower biodegration in shallow groundwater is a little higher than that in deep, which indicates that stronger reducibility means stronger biodegradation of TCP. And the accumulative effect of slow but long-term biodegration has affected the distribution range of TCP's pollution plume observably. |
PDF Full Text Request