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首页> 外文期刊>Journal of Contaminant Hydrology >Role of the riparian zone in controlling the distribution and fate of agricultural nitrogen near a small stream in southern Ontario
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Role of the riparian zone in controlling the distribution and fate of agricultural nitrogen near a small stream in southern Ontario

机译：河岸带在控制安大略省南部一条小溪附近的农业氮素的分布和命运方面的作用

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摘要

Uncultivated riparian areas can play an important role in reducing nutrient loading to streams in agricultural watersheds. Groundwater flow and geochemistry were monitored in the riparian zone of a small agricultural watershed in southern Ontario. Hydraulic and geochemical measure- ments were taken along a transect of monitoring wells extending across the riparian area into an agricultural field. Chloride and nitrate concentrations in groundwater samples collected from the agricultural field were much higher than in samples from the riparian area. A sharp decline in both nitrate and chloride concentrations was observed near the field--riparian zone boundary. It appears that increased recharge within the riparian zone, as compared to the artificially drained field, caused nitrate-rich groundwater from the field to be diverted downward beneath the riparian zone, thus limiting the input of agrochemicals to the riparian area and consequently protecting the stream from potential contamination. Geochemical data also indicated that nitrate was attenuated in the downward moving groundwater. Patterns of dissolved oxygen concentrations and redox potential in the subsurface coincided with the pattern defined by groundwater nitrate. These patterns indicated that conditions Within the riparian zone and at depth near the field-riparian zone boundary were conducive to denitrification. A linear relation between the δ~15N and δ~18O values of nitrate from the monitored transect also supported denitrification as the primary nitrate removal mechanism. This study provides a new conceptual model of how riparian zones may prevent nitrate contamination of streams, and highlights the need for a complete understanding of both groundwater flow and geochemistry in riparian environments.
机译：未耕作的河岸地区在减少农业流域中养分流中的营养含量方面可以发挥重要作用。在安大略省南部一个小型农业流域的河岸带监测了地下水流和地球化学。水力和地球化学测量是沿监测井的横断面进行的，该监测井横跨河岸地区并进入农田。从农业领域收集的地下水样品中的氯化物和硝酸盐浓度远高于沿河地区的样品。在田野-河岸带边界附近观察到硝酸盐和氯化物浓度均急剧下降。与人工流失的农田相比，河岸带内补给的增加似乎导致田间富含硝酸盐的地下水在河岸带下方向下转移，从而限制了农药向河岸带的输入，从而保护了河流免受潜在的污染。地球化学数据还表明，硝酸盐在向下移动的地下水中被减弱。地下溶解氧浓度和氧化还原电势的模式与地下水硝酸盐定义的模式一致。这些模式表明，在河岸带区域内和田野-河岸带边界附近的深度条件有利于反硝化作用。监测断面硝酸盐的δ〜15N和δ〜18O值之间的线性关系也支持反硝化作用作为主要的硝酸盐去除机理。这项研究提供了一个新的概念模型，说明河岸带区域如何防止硝酸盐污染河流，并强调需要全面了解河岸带环境中的地下水流量和地球化学。

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