The anaerobic degradation of aromatic hydrocarbons in a plume originating from a Pintsch gas tar-DNAPL zone was investigated using molecular, isotopic- and microbial analyses. Benzene concentrations diminished at the relatively small meter scale dimensions of the nitrate reducing plume fringe. The ratio of benzene to toluene, ethylbenzene, xylenes and naphthalene (BTEXN) in the fringe zone compared to the plume zone, indicated relatively more loss of benzene in the fringe zone than TEXN. This was substantiated by changes in relative concentrations of BTEXN, and multi-element compound specific isotope analysis for δ²H and δ¹³C. This was supported by the presence of (abcA) genes, indicating the presumed benzene carboxylase enzyme in the nitrate-reducing plume fringe. Biodegradation of most hydrocarbon contaminants at iron reducing conditions in the plume core, appears to be quantitatively of greater significance due to the large volume of the plume core, rather than relatively faster biodegradation under nitrate reducing conditions at the smaller volume of the plume fringe. Contaminant concentration reductions by biodegradation processes were shown to vary distinctively between the source, plume (both iron-reducing) and fringe (nitrate-reducing) zones of the plume. High anaerobic microbial activity was detected in the plume zone as well as in the dense non aqueous phase liquid (DNAPL) containing source zone. Biodegradation of most, if not all, other water-soluble Pintsch gas tar aromatic hydrocarbon contaminants occur at the relatively large dimensions of the anoxic plume core. The highest diversity and concentrations of metabolites were detected in the iron-reducing plume core, where the sum of parent compounds of aromatic hydrocarbons was greater than 10 mg/L. The relatively high concentrations of metabolites suggest a hot spot for anaerobic degradation in the core of the plume downgradient but relatively close to the DNAPL containing source zone.

使用分子、同位素和微生物分析研究了源自 Pintsch 气体焦油-DNAPL 区的羽流中芳烃的厌氧降解。在硝酸盐减少的羽流边缘的相对较小的米尺度尺寸处苯浓度降低。与羽流区相比，边缘区的苯与甲苯、乙苯、二甲苯和萘 (BTEXN) 的比率表明，边缘区的苯损失比 TEXN 相对更多。BTEXN 相对浓度的变化以及 δ²H 和 δ¹³C 的多元素化合物特异性同位素分析证实了这一点) 基因，表明假定的苯羧化酶存在于减少硝酸盐的羽流边缘。大多数碳氢化合物污染物在羽核中的铁还原条件下的生物降解似乎在数量上更重要，因为羽核体积较大，而不是在较小体积的羽流边缘在硝酸盐还原条件下相对较快的生物降解。显示通过生物降解过程降低的污染物浓度在羽流的来源、羽流（铁还原）和边缘（硝酸盐还原）区域之间存在显着差异。在羽流区以及含有致密非水相液体 (DNAPL) 的源区中检测到高厌氧微生物活性。大多数（如果不是全部）的生物降解，其他水溶性 Pintsch 气焦油芳烃污染物出现在相对较大尺寸的缺氧羽流核心处。在铁还原羽核心中检测到代谢物的最高多样性和浓度，其中芳烃母体化合物的总和大于10 mg / L。相对高浓度的代谢物表明在羽流下降的核心是厌氧降解的热点，但相对接近于含有 DNAPL 的源区。