School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK.
School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK.
Sci Total Environ. 2016 Nov 1;569-570:1330-1340. doi: 10.1016/j.scitotenv.2016.06.211. Epub 2016 Jul 12.
Two lowland catchments in the U.K. were sampled throughout 2010-11 to investigate the dominant controls on dissolved organic matter quantity and composition. The catchments had marked differences in terms of nutrient status, land cover and contrasting lithologies resulting in differences in the dominant flow pathways (groundwater vs. surface water dominated). The Upper Wylye is a chalk stream with a baseflow index of 0.98, draining a catchment dominated by intensive agricultural production. Millersford Brook is a lowland peat catchment with a baseflow index of 0.43, draining a semi-natural catchment with heather moorland and coniferous forest. Samples were collected weekly between October 2010 and September 2011 from eleven sampling locations. Samples were analysed to determine dissolved organic carbon, nitrogen and phosphorus fractions with DOM composition evaluated via the DOC:DON ratio, DOC:DOP ratio, specific UV absorption at 254nm, absorbance ratio (a250:a365) and the spectral slope parameter between 350 and 400nm (S350-400). Significant differences were observed in all determinands between the catchments, over time, and spatially along nutrient enrichment and geoclimatic gradients. Seasonal variation in preferential flow pathways mobilising groundwater-derived DOM were identified as likely controls on the delivery of DOM in the permeable chalk dominated catchment. Steeper S350-400 values and elevated a250:a365 ratios in this catchment suggest material of a lower bulk aromatic C content and molecular weight delivered during the winter months when compared to the summer. DOC:DON ratios were markedly lower in the chalk catchment than the peatland catchment, reflecting the paucity of organic matter within the mineral soils of the chalk landscape, and higher fertiliser application rates. This manuscript highlights that DOM composition varies according to catchment landscape character and hydrological function.
2010 年至 2011 年期间，对英国的两个低地流域进行了采样，以研究控制溶解有机物质数量和组成的主要因素。这些流域在营养状况、土地覆盖和对比的岩性方面存在显著差异，导致主要的水流路径（地下水主导或地表水主导）存在差异。上怀利是一条白垩溪流，基流指数为 0.98，流域主要由集约化农业生产主导。米勒斯福德溪是一个低地泥炭流域，基流指数为 0.43，流域主要由石南荒地和针叶林组成。2010 年 10 月至 2011 年 9 月期间，每周从 11 个采样点采集样本。对样品进行了分析，以确定溶解有机碳、氮和磷的分数，通过 DOC:DON 比、DOC:DOP 比、254nm 处的特定紫外吸光度、吸光度比（a250:a365）和 350nm 至 400nm 之间的光谱斜率参数（S350-400）评估 DOM 组成。在所有的测定值中，在不同的流域之间、随时间变化以及在营养富化和地理气候梯度上的空间分布都观察到了显著的差异。在可渗透的白垩岩主导的流域中，优先流动途径移动地下水来源的 DOM 的季节性变化被认为是 DOM 输送的可能控制因素。在这个流域中，S350-400 值较高，a250:a365 比值较高，表明冬季输送的物质的整体芳香 C 含量和分子量较低，与夏季相比。白垩质流域的 DOC:DON 比值明显低于泥炭地流域，反映了白垩地貌的矿物质土壤中有机质的匮乏，以及更高的肥料施用量。本研究表明，DOM 组成根据流域景观特征和水文功能而变化。
