Mobilisation or dilution? Nitrate response of karst springs to high rainfall events
Mobilisation or dilution? Nitrate response of karst springs to high rainfall events
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DOI：
10.5194/hess-18-4423-2014
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发表时间：
2014-01-01
影响因子：
6.3
通讯作者：
Blum, P.
中科院分区：
文献类型：
--
作者：
Huebsch, M.;Fenton, O.;Blum, P.
与农业活动有关的地下水硝酸盐(NO3-)污染是许多国家主要关注的问题。在农业、稀薄的自由排水土壤和岩溶含水层重合的地方，地下水极易受到硝酸盐污染。由于这种系统的停留时间和反硝化潜力通常很低，硝酸盐可以有增无减地排放到地表水中。然而，这类系统对旨在改善水质的农业管理变化的反应也最快。作为对风暴事件的响应，硝酸盐浓度可能会发生显著变化，即浓度迅速降低或增加。目前的研究利用高分辨率硝酸盐和流量数据以及农场钻孔地下水波动数据，研究了位于南爱尔兰草原农场的一个特定岩溶泉水对降雨事件的反应。具体地说，这项研究的目的是对风暴期间与硝酸盐反应有关的可能情景提出一个科学假设，并使用文献中的其他案例研究来验证这一假设。这阐明了在风暴期间导致硝酸盐浓度被动员和/或稀释的控制关键因素。这些因素包括土地利用、水文条件和岩溶作用，这些因素结合在一起可以导致对流动和/或稀释的硝酸盐浓度的不同反应。此外，结果表明，硝酸盐在喀斯特的响应强烈依赖于营养源、是否发生动员和/或稀释以及所采取的途径。这将对向地表水受体输送硝酸盐产生影响。目前的研究提高了我们对岩溶系统中硝酸盐响应的理解，因此可以指导环境建模人员、政策制定者和饮用水管理者遵守欧洲联盟(EU)水框架指令(WFD)的规定。今后，更多的研究应把重点放在对岩溶含水层的高分辨率监测上，以捕捉水化学过程的高度可变性，这些过程以几小时到几天的时间间隔发生。
Nitrate (NO3-) contamination of groundwater associated with agronomic activity is of major concern in many countries. Where agriculture, thin free draining soils and karst aquifers coincide, groundwater is highly vulnerable to nitrate contamination. As residence times and denitrification potential in such systems are typically low, nitrate can discharge to surface waters unabated. However, such systems also react quickest to agricultural management changes that aim to improve water quality. In response to storm events, nitrate concentrations can alter significantly, i.e. rapidly decreasing or increasing concentrations. The current study examines the response of a specific karst spring situated on a grassland farm in South Ireland to rainfall events utilising high-resolution nitrate and discharge data together with on-farm borehole groundwater fluctuation data. Specifically, the objectives of the study are to formulate a scientific hypothesis of possible scenarios relating to nitrate responses during storm events, and to verify this hypothesis using additional case studies from the literature. This elucidates the controlling key factors that lead to mobilisation and/or dilution of nitrate concentrations during storm events. These were land use, hydrological condition and karstification, which in combination can lead to differential responses of mobilised and/or diluted nitrate concentrations. Furthermore, the results indicate that nitrate response in karst is strongly dependent on nutrient source, whether mobilisation and/or dilution occur and on the pathway taken. This will have consequences for the delivery of nitrate to a surface water receptor. The current study improves our understanding of nitrate responses in karst systems and therefore can guide environmental modellers, policy makers and drinking water managers with respect to the regulations of the European Union (EU) Water Framework Directive (WFD). In future, more research should focus on the high-resolution monitoring of karst aquifers to capture the high variability of hydrochemical processes, which occur at time intervals of hours to days.