Contrasting Nitrogen Fate in Watersheds Using Agricultural and Water Quality Information
Contrasting Nitrogen Fate in Watersheds Using Agricultural and Water Quality Information
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DOI：
10.2134/jeq2016.02.0071
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发表时间：
2016-09-01
影响因子：
2.4
通讯作者：
McCarthy, Kathleen A.
中科院分区：
文献类型：
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作者：
Essaid, Hedeff I.;Baker, Nancy T.;McCarthy, Kathleen A.
利用剩余氮(N)估算、主成分分析（PCA）和端元混合分析（EMMA）对不同农业流域氮的命运进行了多地点比较。我们在印第安纳州、爱荷华州、马里兰州、内布拉斯加州、密西西比州和华盛顿州的10个流域应用了PCA-EMMA，面积从5到1254公里(2)不等，其中有4个嵌套流域。流域剩余氮是通过从1987年至2004年期间大气沉降、植物固定、肥料和粪便的氮输入估计值中减去作物吸收和挥发的估计值来确定的。流域平均剩余氮为11 ~ 52公斤N公顷（-1），占氮输入的9% ~ 32%。在PCA-EMMA过程中，利用河流、地表径流、排水、地下水（GW）、河床和非饱和带中的溶质浓度来确定影响观察到的河流浓度变化的独立成分，以及影响河流流量和NO3负荷的端元。末端成员包括稀释径流、农业径流、底栖处理、瓷砖排水以及氧化和缺氧GW。在土壤渗透性较强的流域（华盛顿、内布拉斯加州和马里兰州），剩余氮更大，允许更大的渗透，氧化GW是NO3负荷的主要来源。这些流域NO3的地下运输导致了反硝化作用对部分剩余氮的去除。在渗透性较差的流域（爱荷华州、印第安纳州和密西西比州），NO3通过排水和径流迅速输送到河流中，几乎没有被清除。在较大的流域中观察到底栖硅藻对河床NO3去除的证据。
Surplus nitrogen (N) estimates, principal component analysis (PCA), and end-member mixing analysis (EMMA) were used in a multisite comparison contrasting the fate of N in diverse agricultural watersheds. We applied PCA-EMMA in 10 watersheds located in Indiana, Iowa, Maryland, Nebraska, Mississippi, and Washington ranging in size from 5 to 1254 km(2) with four nested watersheds. Watershed Surplus N was determined by subtracting estimates of crop uptake and volatilization from estimates of N input from atmospheric deposition, plant fixation, fertilizer, and manure for the period from 1987 to 2004. Watershed average Surplus N ranged from 11 to 52 kg N ha(-1) and from 9 to 32% of N input. Solute concentrations in streams, overland runoff, tile drainage, groundwater (GW), streambeds, and the unsaturated zone were used in the PCA-EMMA procedure to identify independent components contributing to observed stream concentration variability and the end-members contributing to streamflow and NO3 load. End-members included dilute runoff, agricultural runoff, benthic-processing, tile drainage, and oxic and anoxic GW. Surplus N was larger in watersheds with more permeable soils (Washington, Nebraska, and Maryland) that allowed greater infiltration, and oxic GW was the primary source of NO3 load. Subsurface transport of NO3 in these watersheds resulted in some removal of Surplus N by denitrification. In less permeable watersheds (Iowa, Indiana, and Mississippi), NO3 was rapidly transported to the stream by tile drainage and runoff with little removal. Evidence of streambed removal of NO3 by benthic diatoms was observed in the larger watersheds.