Nitrate in Groundwater of the United States, 1991-2003
Nitrate in Groundwater of the United States, 1991-2003
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DOI：
10.1021/es100546y
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发表时间：
2010-07-01
影响因子：
11.4
通讯作者：
Dubrovsky, Neil M.
中科院分区：
文献类型：
--
作者：
Burow, Karen R.;Nolan, Bernard T.;Dubrovsky, Neil M.
一项对美国地下水中硝酸盐浓度的评估表明，在氮投入高的地区下方的浅层有毒地下水中，硝酸盐浓度最高。1991-2003年间，作为美国地质调查局国家水质评估(NAWOA)计划的一部分，在全美51个研究地区对5101口井进行了采样。水井网络反映了主要含水层的国内水井所代表的现有已用资源(主要含水层研究)，以及最近在主要陆面活动下补给的地下水(土地利用研究)。在排水良好的土壤和好氧的地球化学条件下，农业用地下浅层地下水中的硝酸盐浓度最高。在深层地下水中，硝酸盐浓度最低，在那里地下水减少，或者在地下水较老的地方，因此浓度反映了历史上低的氮肥施用量。使用分类和回归树分析来确定N输入、生物地球化学过程和含水层物理属性在解释地下水中硝酸盐浓度方面的相对重要性。按平方和递减排序的因素表明，地下水硝酸盐浓度变化的主要原因是溶解铁浓度，其次是锰、钙、农田氮肥投入、排水良好的土壤百分比和溶解氧。总体而言，地下水中的硝酸盐浓度受氧化还原条件的影响最大，其次是非点源N输入。其他水质指标和物理变量对硝酸盐浓度也有次要影响。
An assessment of nitrate concentrations in groundwater in the United States indicates that concentrations are highest in shallow, oxic groundwater beneath areas with high N inputs. During 1991-2003, 5101 wells were sampled in 51 study areas throughout the U.S. as part of the U.S. Geological Survey National Water-Quality Assessment (NAWOA) program. The well networks reflect the existing used resource represented by domestic wells in major aquifers (major aquifer studies), and recently recharged groundwater beneath dominant land-surface activities (land-use studies). Nitrate concentrations were highest in shallow groundwater beneath agricultural land use in areas with well-drained soils and oxic geochemical conditions. Nitrate concentrations were lowest in deep groundwater where groundwater is reduced, or where groundwater is older and hence concentrations reflect historically low N application rates. Classification and regression tree analysis was used to identify the relative importance of N inputs, biogeochemical processes, and physical aquifer properties in explaining nitrate concentrations in groundwater. Factors ranked by reduction in sum of squares indicate that dissolved iron concentrations explained most of the variation in groundwater nitrate concentration, followed by manganese, calcium, farm N fertilizer inputs, percent well-drained soils, and dissolved oxygen. Overall, nitrate concentrations in groundwater are most significantly affected by redox conditions, followed by nonpoint-source N inputs. Other water-quality indicators and physical variables had a secondary influence on nitrate concentrations.