He Shengjia, Lu Jun
School of Environmental and Resource Sciences, Zhejiang A & F University, Lin'an, Hangzhou, 311300, China.
China Ministry of Education Key Laboratory of Environment Remediation and Ecological Health, Zhejiang University, Hangzhou, 310058, China.
Environ Sci Pollut Res Int. 2021 Feb 25. doi: 10.1007/s11356-021-12802-3.
Inputs of phosphorus (P) during baseflow period usually come from groundwater, bed sediments, and some other sources. Baseflow P can have critical effects on nutrient enrichment of surface waters in some intensively cultivated agricultural watersheds. This study was conducted to estimate the baseflow dissolved phosphorus (DP) export in a typical rainy agricultural watershed of eastern China using a recursive tracing source algorithm (RTSA) and reveal the rules and trends of baseflow DP loads and concentrations. Results indicated that RTSA provided a satisfactory prediction for baseflow DP load (Nash-Sutcliffe efficiency (NSE) = 0.72, R = 0.74). From 2003 to 2012, the annual baseflow DP loads ranged from 0.159 (2004) to 0.771 (2012) kg/ha which contributed about 64.3% of the mean total annual DP export in stream (0.597 kg/ha). The annual flow-weighted DP concentrations in streamflow (0.076-0.125 mg/L) and baseflow (0.076-0.137 mg/L) far exceeded the eutrophication threshold of DP (0.01 mg/L). Significantly increasing trends were obtained in the streamflow and baseflow DP loads and the flow-weighted concentrations (Mann-Kendall test, Z > 2.56, p < 0.01) because of the changes of hydro-meteorological conditions. This indicates that, in the context of global climate change, baseflow DP export would be one of key issues for nonpoint source pollution control in the intensive agricultural watershed.
基流期磷（P）的输入通常来自地下水、河床沉积物和其他一些来源。在一些集约化种植的农业流域，基流磷会对地表水的养分富集产生关键影响。本研究利用递归溯源算法（RTSA）估算了中国东部一个典型多雨农业流域的基流溶解磷（DP）输出，并揭示了基流DP负荷和浓度的规律及趋势。结果表明，RTSA对基流DP负荷提供了令人满意的预测（纳什-萨特克利夫效率（NSE）=0.72，R=0.74）。2003年至2012年，年基流DP负荷范围为0.159（2004年）至0.771（2012年）kg/ha，约占河流中年平均总DP输出量（0.597 kg/ha）的64.3%。河流径流（0.076 - 0.125 mg/L）和基流（0.076 - 0.137 mg/L）的年流量加权DP浓度远超过DP的富营养化阈值（0.01 mg/L）。由于水文气象条件的变化，河流径流和基流DP负荷以及流量加权浓度呈现出显著增加的趋势（曼-肯德尔检验，Z>2.56，p<0.01）。这表明，在全球气候变化的背景下，基流DP输出将是集约化农业流域非点源污染控制的关键问题之一。
