Relationships between dissolved organic matter (DOM) reactivity and chemical composition in a groundwater plume containing petroleum-derived DOM were examined by quantitative and qualitative measurements to determine the source and chemical composition of the compounds that persist downgradient. Samples were collected from a transect down the core of the plume in the direction of groundwater flow. An exponential decrease in dissolved organic carbon concentration resulting from biodegradation along the transect correlated with a continuous shift in fluorescent DOM from shorter to longer wavelengths. Moreover, ultrahigh resolution mass spectrometry showed a shift from low molecular weight (MW) aliphatic, reduced compounds to high MW, unsaturated (alicyclic/aromatic), high oxygen compounds that are consistent with carboxyl-rich alicyclic molecules. The degree of condensed aromaticity increased downgradient, indicating that compounds with larger, conjugated aromatic core structures were less susceptible to biodegradation. Nuclear magnetic resonance spectroscopy showed a decrease in alkyl (particularly methyl) and an increase in aromatic/olefinic structural motifs. Collectively, data obtained from the combination of these complementary analytical techniques indicated that changes in the DOM composition of a groundwater plume are gradual, as relatively low molecular weight (MW), reduced, aliphatic compounds from the oil source were selectively degraded and high MW, alicyclic/aromatic, oxidized compounds persisted.

通过定量和定性测量来检查含有石油衍生的DOM的地下水羽中溶解有机物（DOM）反应性与化学组成之间的关系，以确定持续下降的化合物的来源和化学组成。沿地下水流的方向从羽状岩心下方的横断面收集样品。沿着横断面的生物降解导致的溶解有机碳浓度的指数下降与荧光DOM从较短波长到较长波长的连续移动相关。此外，超高分辨率质谱显示从低分子量（MW）的脂肪族还原化合物转变为与富含羧基的脂环族分子一致的高MW，不饱和（脂环族/芳族）高氧化合物。稠合芳族化合物的程度降低了梯度，表明具有较大共轭芳族核结构的化合物较不易被生物降解。核磁共振波谱显示烷基（特别是甲基）的减少和芳烃/烯烃结构基序的增加。总的来说，从这些互补的分析技术的组合中获得的数据表明，地下水羽流中DOM组成的变化是渐进的，因为相对较低的分子量（MW），还原的，来自油源的脂肪族化合物被选择性地降解，并且高MW，脂环族/芳族氧化化合物持续存在。核磁共振波谱显示烷基（特别是甲基）的减少和芳烃/烯烃结构基序的增加。总的来说，从这些互补的分析技术的组合中获得的数据表明，地下水羽流中DOM组成的变化是渐进的，因为相对较低的分子量（MW），还原的，来自油源的脂肪族化合物被选择性地降解，并且高MW，脂环族/芳族氧化化合物持续存在。核磁共振波谱显示烷基（特别是甲基）的减少和芳烃/烯烃结构基序的增加。总的来说，从这些互补的分析技术的组合中获得的数据表明，地下水羽流中DOM组成的变化是渐进的，因为相对较低的分子量（MW），还原的，来自油源的脂肪族化合物被选择性地降解，并且高MW，脂环族/芳族氧化化合物持续存在。