Chloride source delineation in an urban‐agricultural watershed: Deicing agents versus agricultural contributions
Chloride source delineation in an urban‐agricultural watershed: Deicing agents versus agricultural contributions
复制标题
城市农业流域中的氯离子源划分：除冰剂与农业贡献
作者：
Andrew H. Oberhelman;E. Peterson
在城市农业流域（10% 城市/不透水，87% 农业）中对溪流水、瓦排水和地下水中的氯化物 (Cl−)、溴化物 (Br−)、硝酸盐氮 (NO3-N)、钠 (Na+)、钙 (Ca2+) 和钾 (K+) 进行分析 (n = 525)，以探索源自城市来源与农业来源的 Cl− 特征的潜在差异。仅在冬季补给事件期间，测得的 Cl− 浓度才超过 230mg/L 的慢性阈值。在基流下，几乎所有地表水和瓷砖水样的 Cl− 浓度均高于计算出的背景阈值 18 mg/L。 Mann-Whitney U 测试显示，城市和农业水域中 Cl− 与 Br− (p = .045)、NO3-N (p < .0001)、Ca2+ (p < .0001) 和 Na+ (p < .0001) 的比率存在显着差异。虽然 Cl− 比率表明道路盐是流域 Cl− 的主要来源，但氯化钾肥料是重要的次要来源。城市土地利用最少的流域的除冰对 Cl− 动态产生了深远的影响；然而，农业实践全年都贡献了 Cl−，使河流基流 Cl− 浓度升高至背景水平以上。
Analyses (n = 525) of chloride (Cl−), bromide (Br−), nitrate as nitrogen (NO3‐N), sodium (Na+), calcium (Ca2+) and potassium (K+) in stream water, tile‐drain water and groundwater were conducted in an urban‐agricultural watershed (10% urban/impervious, 87% agriculture) to explore potential differences in the signature of Cl− originating from an urban source as compared with an agricultural source. Only during winter recharge events did measured Cl− concentrations exceed the 230 mg/L chronic threshold. At base flow, nearly all surface water and tile water samples had Cl− concentrations above the calculated background threshold of 18 mg/L. Mann–Whitney U tests revealed ratios of Cl− to Br− (p = .045), to NO3‐N (p < .0001), to Ca2+ (p < .0001), and to Na+ (p < .0001) to be significantly different between urban and agricultural waters. While Cl− ratios indicate that road salt was the dominant source of Cl− in the watershed, potassium chloride fertilizer contributed as an important secondary source. Deicing in watersheds where urban land use is minimal had a profound impact on Cl− dynamics; however, agricultural practices contributed Cl− year‐round, elevating stream base flow Cl− concentrations above the background level.