Geochemical conditions in groundwater systems: Implications for the attenuation of agricultural nitrate
Geochemical conditions in groundwater systems: Implications for the attenuation of agricultural nitrate
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DOI：
10.1016/j.agwat.2007.09.003
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发表时间：
2008-02
影响因子：
6.7
通讯作者：
T. Thayalakumaran;K. Bristow;P. Charlesworth;T. Fass
中科院分区：
文献类型：
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作者：
T. Thayalakumaran;K. Bristow;P. Charlesworth;T. Fass
农业氮肥产生的硝酸盐是浅层地下水的一种广泛污染物，对人类、动物和生态系统健康造成不利影响。为了评估地下水硝酸盐污染的全面程度，以及它如何可能随着时间的推移而演变，必须了解对含水层同化能力的控制。这种理解水平也将有助于更好地制定旨在控制进入下游水系统的硝酸盐数量的政策和激励措施。地下水中硝酸盐衰减的潜力进行了评估，通过检查的浓度和分布模式的电子供体，如溶解有机碳（DOC），亚铁，和氧化还原指标，如溶解氧（DO）和Eh在57个监测孔在较低的Burdekin沿海洪泛区，昆士兰州和澳大利亚的总理灌溉区之一。硝酸盐浓度范围为0.1至14.4mg/L NO3-N，但在靠近海岸的钻孔中大多无法检测到。地下水年龄数据表明，虽然某些地区存在硝酸盐“热点”，但部分或大部分硝酸盐在流向海洋的途中被消耗。低硝酸盐浓度与高亚铁浓度相结合。在55%的钻孔中发现的低DO浓度（<2 mg/L）和高亚铁浓度表明氧化还原条件适合于通过反硝化或异化硝酸盐还原为铵来衰减硝酸盐。还原环境可能与这些地下水中发现的高DOC浓度（高达82 mgC/L）有关。此外，在艾尔地区发现的亚铁含量高，结合DOC广泛的地理分布，表明这些地区具有很高的潜力，可持续的地球化学过程，降低硝酸盐水平。地球化学指标的分布也表明，地下水系统的浅层（<15 m）比深层具有更大的硝酸盐还原潜力。该地图确定了布尔德金下游最有可能进行脱氮的区域，这是帮助了解和管理进入地下水的硝酸盐命运的有价值的第一步。
Nitrate resulting from nitrogen fertilisers used in Agriculture is a widespread contaminant of shallow groundwater and causes adverse effects on human, animal and ecosystem health. In order to evaluate the full extent of groundwater nitrate contamination, and how it might evolve in time, it is essential to understand controls on aquifer assimilative capacity. This level of understanding will also help to better target policies and incentives aimed at controlling the amount of nitrate entering downstream water systems. The potential for nitrate attenuation in groundwater was assessed by examining the concentration and distribution pattern of electron donors such as dissolved organic carbon (DOC), ferrous iron, and redox indicators such as dissolved oxygen (DO) and Eh in 57 monitoring bores on the lower Burdekin coastal floodplain, one of Queensland's and Australia's premier irrigation districts. Nitrate concentrations ranged from 0.1 to 14.4mg/L NO3-N but were mostly undetectable in bores close to the coast. Groundwater age dates suggest that while there are nitrate ‘hot spots’ in certain areas, some or most of the nitrate is being consumed on its way to the ocean. Low nitrate concentrations were coupled with high ferrous concentrations. The low DO concentrations (<2mg/L) and high ferrous concentrations found in 55% of the bores indicate that redox conditions are suitable for nitrate attenuation by either denitrification or dissimilatory nitrate reduction to ammonium. The reducing environment may be associated with the high DOC concentrations (up to 82mgC/L) found in these groundwaters. Furthermore, high levels of ferrous iron found in the Ayr area combined with the wide spread geographical distribution of DOC indicate that these areas have a high potential for sustaining geochemical processes that reduces nitrate levels. The distribution of geochemical indicators also suggests that the shallower depths (<15m) of the groundwater systems have more potential for nitrate reduction than the deeper depths. The map identifying areas within the lower Burdekin with most potential for denitrification is a valuable first step in helping to understand and manage the fate of nitrate entering the groundwater.