Antecedent conditions, hydrological connectivity and anthropogenic inputs: Factors affecting nitrate and phosphorus transfers to agricultural headwater streams.
Antecedent conditions, hydrological connectivity and anthropogenic inputs: Factors affecting nitrate and phosphorus transfers to agricultural headwater streams.
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DOI：
10.1016/j.scitotenv.2015.12.025
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发表时间：
2016-03
期刊：
影响因子：
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通讯作者：
F. Outram;R. Cooper;Gisela Sünnenberg;K. Hiscock;A. Lovett
中科院分区：
文献类型：
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作者：
F. Outram;R. Cooper;Gisela Sünnenberg;K. Hiscock;A. Lovett
本文研究了3个水文年（2012-2014）耕地水源集水区降雨径流、集水区连通性、前期水分条件和肥料施用与硝态氮和总磷（TP）通量之间的关系。年降水总量在不同年份之间变化不大，但降雨时间强烈影响径流生成以及随后的硝态氮和全磷通量。最大的硝酸盐-N通量（> 250 kg N day - 1）和总磷通量（> 10 kg TP day - 1）仅发生在浅层地下水距离地表0.6 m以内且径流系数大于0.1时。与2013年（15.1 kg N ha - 1; 0.21 kg P ha - 1）相比，2012年干旱恢复导致年度硝酸盐-N （7.4 kg N ha - 1）和全磷（0.12 kg P ha - 1）通量降低，因此达到这些阈值的频率较低。2013年冬季潮湿，浅层地下水位升高，导致地下通道和排水流量更频繁地激活。在整个时期，干燥的前期条件对TP负荷的升高有暂时的影响。连续暴雨事件后TP源枯竭的证据可归因于通过不透水路面与河网临时连接的关键源区域的重复枯竭。由于各农场轮作方式的不同，化肥的施用在三年内变化很大，每年氮肥和磷肥的投入分别变化高达21%和41%。在次集水口未观察到年河流硝酸盐n和总磷负荷的比例减少，因为负荷在很大程度上受年径流的影响。施磷肥期间硝态氮负荷量略高，但施磷肥与河流全磷负荷量关系不大。这些数据表明，这种集约化的耕地集水区可能处于生物地球化学稳定状态，因此，遗留的营养物质储存可以缓冲当代营养物质输入的变化。
This paper examines relationships between rainfall–runoff, catchment connectivity, antecedent moisture conditions and fertiliser application with nitrate-N and total phosphorus (TP) fluxes in an arable headwater catchment over three hydrological years (2012–2014). Annual precipitation totals did not vary substantially between years, yet the timing of rainfall strongly influenced runoff generation and subsequent nitrate-N and TP fluxes. The greatest nitrate-N (> 250 kg N day− 1) and TP (> 10 kg TP day− 1) fluxes only occurred when shallow groundwater was within 0.6 m of the ground surface and runoff coefficients were greater than 0.1. These thresholds were reached less frequently in 2012 due to drought recovery resulting in lower annual nitrate-N (7.4 kg N ha− 1) and TP (0.12 kg P ha− 1) fluxes in comparison with 2013 (15.1 kg N ha− 1; 0.21 kg P ha− 1). The wet winter of 2013 with elevated shallow groundwater levels led to more frequent activation of sub-surface pathways and tile drain flow. Throughout the period, dry antecedent conditions had a temporary effect in elevating TP loads. Evidence of TP source exhaustion after consecutive storm events can be attributed to the repeated depletion of temporarily connected critical source areas to the river network via impermeable road surfaces. Fertiliser application varied considerably across three years due to differences in crop rotation between farms, with annual N and P fertiliser inputs varying by up to 21% and 41%, respectively. Proportional reductions in annual riverine nitrate-N and TP loadings were not observed at the sub-catchment outlet as loadings were largely influenced by annual runoff. Nitrate loadings were slightly higher during fertiliser application, but there was little relationship between P fertiliser application and riverine TP load. These data indicate that this intensive arable catchment may be in a state of biogeochemical stationarity, whereby legacy stores of nutrients buffer against changes in contemporary nutrient inputs.