Source availability and hydrological connectivity determined nitrate-discharge relationships during rainfall events in karst catchment as revealed by high-frequency nitrate sensing.
Source availability and hydrological connectivity determined nitrate-discharge relationships during rainfall events in karst catchment as revealed by high-frequency nitrate sensing.
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DOI：
10.1016/j.watres.2023.119616
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发表时间：
2023-01
期刊：
影响因子：
12.8
通讯作者：
F. Yue;Si‐Liang Li;S. Waldron;D. Oliver;Xi Chen;Pan Li;Tao Peng;Cong-Qiang Liu
中科院分区：
文献类型：
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作者：
F. Yue;Si‐Liang Li;S. Waldron;D. Oliver;Xi Chen;Pan Li;Tao Peng;Cong-Qiang Liu
喀斯特地形的季节性季风降雨往往与高浓度的硝酸盐-N在流排水农田。如此高的浓度会对环境和人类健康造成问题。然而，降雨事件，动员硝酸盐和由此产生的硝酸盐出口之间的关系仍然知之甚少，在喀斯特地形。为了更好地了解降雨过程中硝酸盐动力学的驱动过程，使用传感器技术分析了单个降雨事件的特征。38个降雨事件分离的高频数据集跨越19个月的岩溶泉网站。结果表明，硝态氮排放（N-Q）滞后在79%的降雨事件中表现出反循环滞后环模式，表明硝态氮输出从长距离在短事件周期。岩溶水文连通性和水源有效性是影响N-Q滞后的两个主要因素。强降雨期水文连通性的逐渐增强加速了岩溶含水层系统对硝酸盐的运移。4个主成分（包括前期条件PC 1和3和降雨特征PC 2和4）对降雨事件的累积方差贡献率为82%。4个主成分的多元线性回归解释了降雨过程中硝态氮负荷和幅度的50%以上的变化，但对硝态氮浓度和水化学参数的描述较差，可能受到其他因素的影响，例如，硝态氮转化、施肥时间和水-岩相互作用。虽然事件流过程中的氮浓度变化是明显的，占前期条件和降雨因素可以帮助预测降雨事件过程中的降雨事件氮负荷。岩溶集水区的污染发生了冲洗的硝酸盐输入以下降雨事件，因此，前期和降雨条件的水质管理考虑的重要因素。在类似的喀斯特地区，在雨季减少源的可用性可能有助于减少氮负荷。
Karst terrain seasonal monsoonal rainfall is often associated with high concentrations of nitrate-N in streams draining agricultural land. Such high concentrations can pose problems for environmental and human health. However, the relationship between rainfall events that mobilize nitrate and resulting nitrate export remains poorly understood in karst terrain. To better understand the processes that drive nitrate dynamics during rainfall events, the characteristics of individual rainfall events were analyzed using sensor technology. Thirty-eight rainfall events were separated from the high-frequency dataset spanning 19 months at a karst spring site. The results revealed that nitrate-discharge (N-Q) hysteresis in 79% of rainfall events showed anticlockwise hysteresis loop patterns, indicating nitrate export from long distances within short event periods. Karstic hydrological connectivity and source availability were considered two major determining factors of N-Q hysteresis. Gradual increase in hydrological connectivity during intensive rainfall period accelerated nitrate transportation by karst aquifer systems. Four principal components (PCs, including antecedent conditions PC1&3 and rainfall characteristics PC2&4 explained 82% of the cumulative variance contribution to the rainfall events. Multiple linear regression of four PCs explained more than 50% of the variation of nitrate loading and amplitude during rainfall events, but poorly described nitrate concentrations and hydro-chemistry parameters, which may be influenced by other factors, e.g., nitrate transformation, fertilization time and water-rock interaction. Although variation of N concentration during event flow is evident, accounting for antecedent conditions and rainfall factors can help to predict rainfall event N loading during rainfall events. Pollution of the karstic catchment occurred by a flush of nitrate input following rainfall events; antecedent and rainfall conditions are therefore important factors to consider for the water quality management. Reducing source availability during the wet season may facilitate to reduction of nitrogen loading in similar karst areas.