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Seasonal dynamics of dissolved organic matter in high arsenic shallow groundwater systems
Journal of Hydrology ( IF 6.4 ) Pub Date : 2020-10-01 , DOI: 10.1016/j.jhydrol.2020.125120
Yijun Yang , Xiaofang Yuan , Yamin Deng , Xianjun Xie , Yiqun Gan , Yanxin Wang

Abstract Dissolved organic matter (DOM) plays critical roles in biogeochemistry of arsenic in groundwater systems. To characterize the spatial–temporal variations of groundwater DOM and its impacts on arsenic dynamics, surface water and shallow groundwater from two different depths were collected during monsoon and non-monsoon periods in Jianghan Plain, central Yangtze River Basin. Parallel factor analysis (PARAFAC) of the three-dimensional fluorescence excitation–emission matrix (EEM) reveals that DOM comprises three major components, one microbial humic-like component (C1) and two terrestrial humic-like components (C2 and C3). Abundant terrestrially-derived humic-like components were observed during monsoon while more microbially-derived DOM occurred in groundwater during non-monsoon season. These seasonal DOM variations are found to be related to groundwater-surface water (GW-SW) interactions, which is evidenced by stable H and O isotopes and Cl/Br mass ratios. During monsoon season, groundwater is recharged from dilute rainwater, evaporated surface water, and polluted surface water. More terrestrial humic-like components are introduced by precipitation and local agricultural activities (e.g. irrigation, paddy cultivation) during monsoon. The fluorescence spectroscopy and stable carbon isotopes (δ13CDIC and δ13CDOC) results indicate that seasonal As variations are affected by seasonal DOM dynamics. Smaller Δδ13C values (defined as δ13CDIC – δ13CDOC) with higher As concentrations are found during non-monsoon while larger Δδ13C values with relatively lower As concentrations are observed during monsoon season. The strong correlation between DOC and Fe(II) concentrations (r = 0.64, p

中文翻译:

高砷浅层地下水系统中溶解有机质的季节动态

摘要 溶解有机质 (DOM) 在地下水系统中砷的生物地球化学中起着至关重要的作用。为了表征地下水 DOM 的时空变化及其对砷动力学的影响,在长江流域中部江汉平原季风和非季风期间收集了两个不同深度的地表水和浅层地下水。三维荧光激发-发射矩阵 (EEM) 的平行因子分析 (PARAFAC) 表明,DOM 包含三个主要成分,一种微生物类腐殖质成分 (C1) 和两种陆地类腐殖质成分 (C2 和 C3)。在季风期间观察到丰富的陆源类腐殖质成分,而在非季风季节地下水中出现更多微生物来源的 DOM。发现这些季节性 DOM 变化与地下水-地表水 (GW-SW) 相互作用有关,这可以通过稳定的 H 和 O 同位素以及 Cl/Br 质量比来证明。在季风季节,地下水由稀释的雨水、蒸发的地表水和污染的地表水补给。季风期间降水和当地农业活动(例如灌溉、水稻种植)引入了更多的陆地腐殖质类成分。荧光光谱和稳定碳同位素(δ13CDIC 和 δ13CDOC)结果表明季节性 As 变化受季节性 DOM 动态影响。在非季风期间发现具有较高砷浓度的较小 Δδ13C 值(定义为 δ13CDIC – δ13CDOC),而在季风季节观察到较大的 Δδ13C 值和相对较低的砷浓度。
更新日期:2020-10-01
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