State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, PR China.
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, PR China.
J Hazard Mater. 2021 Mar 15;406:124702. doi: 10.1016/j.jhazmat.2020.124702. Epub 2020 Nov 28.
Dissolved organic matter (DOM) is a crucial controlling factor in mobilizing arsenic. However, direct delineations of DOM regarding both optical properties and molecular signatures were rarely conducted in high-arsenic groundwater. Here, both groundwater and surface water were taken from the Hetao Basin, China, to decipher DOM properties with both optical spectrophotometer and Fourier transform ion cyclotron resonance mass spectrometry. The tryptophan-like component (C4) was averagely less than 30% in groundwater DOM, being positively associated with high H/C-ratio molecules (H/C > 1.2) and mainly grouped as highly unsaturated and phenolic compounds and aliphatic compounds. Other three humic-like components (C1, C2, C3) had positive associations with low H/C-ratio molecules (H/C < 1.2), which mainly consisted of highly unsaturated and phenolic compounds, polyphenols, and polycyclic aromatics. Groundwater arsenic concentrations were positively correlated with humic-like, low H/C-ratio, and recalcitrant organic compounds, which may be the consequence of labile organic matter degradation. The degradation caused Fe(III) oxide reduction and mobilized the solid arsenic. In addition, high abundances of these recalcitrant organic compounds in high-arsenic groundwater may contribute to arsenic enrichment via electron shuttling, competition for surface sites, and complexation process. It suggested that groundwater proxies would be either the result or the cause of biogeochemical processes in aquifers.
溶解有机质 (DOM) 是砷迁移的关键控制因素。然而，在高砷地下水中，很少直接对 DOM 的光学性质和分子特征进行描述。本研究从中国河套盆地采集地下水和地表水，利用分光光度计和傅里叶变换离子回旋共振质谱仪来解析 DOM 的性质。在地下水中，色氨酸类物质 (C4) 的平均值不到 DOM 的 30%，与高 H/C-比分子（H/C > 1.2）呈正相关，主要为高度不饱和和酚类化合物以及脂肪族化合物。其他三种类腐殖质物质（C1、C2、C3）与低 H/C-比分子（H/C < 1.2）呈正相关，主要由高度不饱和和酚类化合物、多酚和多环芳烃组成。地下水中的砷浓度与类腐殖质、低 H/C-比和难降解有机化合物呈正相关，这可能是由于易降解有机物的降解所致。这种降解导致三价铁氧化物的还原和固砷的迁移。此外，这些难降解有机化合物在高砷地下水中的高丰度可能通过电子穿梭、表面位点竞争和络合过程促进砷的富集。这表明地下水指标可能是含水层中生物地球化学过程的结果或原因。
