Harjung A, Schweichhart J, Rasch G, Griebler C
University of Vienna, Department of Functional & Evolutionary Ecology, Division Limnology, Djerassiplatz 1, 1030 Vienna, Austria.
Biology Centre CAS, SoWa, Ceské Budejovice, Czechia.
Sci Total Environ. 2023 Jan 1;854:158542. doi: 10.1016/j.scitotenv.2022.158542. Epub 2022 Sep 8.
Dissolved organic matter (DOM) in terrestrial groundwater is generally low in concentration compared to inland surface waters. However, the overall amount of groundwater DOM is huge, as there is 100 times more fresh groundwater than fresh surface water. To date, research on groundwater DOM has merely focused on specific threats to humans such as e.g. DOM and heavy metal complexations and DOM from hydrocarbon contamination. A comprehensive, large-scale study of groundwater is still missing. Here, we examine DOM properties in a large-scale approach with regards to surface characteristics such as land use and altitude, aquifer characteristics as well as microbial features. We analyzed 1600 water samples from 100 groundwater bodies all over Austria with regards to their DOM quantity, quality and bacterial abundance (BA). DOM quality was evaluated with self-organizing maps on fluorescence excitation-emission-matrices (EEMs) combined with Ward clustering and subsequent parallel factor analysis to describe DOM properties of each cluster. We evaluated how these clusters differed among each other, based on DOC and nitrate concentrations, BA and selected environmental characteristics. Our results show that fluorescence components in groundwater resemble components found in other groundwater studies, in studies from forest streams, the dark ocean, agricultural catchments and wastewater treatment plants. The latter fluorescence components were associated with a cluster that is characterized by agricultural and urban land use, as well as by high nitrate concentrations. Clusters with an increased abundance of high-molecular weight and humic components, commonly associated with vascular plant and soil origin, correlated with a higher bacterial abundance. This observation provides evidence that elevated numbers of suspended bacteria mainly originate from the surface. Our study shows that DOM fluorescence can be a fast monitoring tool to identify aquifers under anthropogenic stress and delineate sensitive recharge areas with high surface-groundwater interaction.
与内陆地表水相比，陆地地下水中的溶解有机物（DOM）浓度通常较低。然而，地下水DOM的总量巨大，因为新鲜地下水的量是新鲜地表水的100倍。迄今为止，对地下水DOM的研究仅关注对人类的特定威胁，例如DOM与重金属的络合以及来自碳氢化合物污染的DOM。目前仍缺乏对地下水的全面、大规模研究。在此，我们采用大规模方法研究DOM特性，涉及土地利用和海拔等地表特征、含水层特征以及微生物特征。我们分析了来自奥地利各地100个地下水体的1600个水样，检测其DOM数量、质量和细菌丰度（BA）。通过荧光激发 - 发射矩阵（EEMs）的自组织映射结合沃德聚类和随后的平行因子分析来评估DOM质量，以描述每个聚类的DOM特性。我们根据溶解有机碳（DOC）和硝酸盐浓度、BA以及选定的环境特征，评估这些聚类之间的差异。我们的结果表明，地下水中的荧光成分与其他地下水研究、森林溪流研究、黑暗海洋研究、农业集水区研究和污水处理厂研究中发现的成分相似。后一种荧光成分与一个以农业和城市土地利用以及高硝酸盐浓度为特征的聚类相关。高分子量和腐殖质成分含量增加的聚类，通常与维管植物和土壤来源相关，与较高的细菌丰度相关。这一观察结果证明，悬浮细菌数量的增加主要源于地表。我们的研究表明，DOM荧光可以作为一种快速监测工具，用于识别受人为压力影响的含水层，并划定具有高地表水 - 地下水相互作用的敏感补给区。
