近日，英国一个研究团队在最新一期的《水资源研究》杂志上发表了他们研究成果"Nitrate pollution in intensively farmed regions: What are the prospects for sustaining high-quality groundwater"，研究人员对泰晤士河140多年来的水质监测数据进行分析后指出，现代农耕技术虽然确保了粮食供应，但也对河水资源造成了长期的氮污染。
在英国，对泰晤士河水质的监测已持续了140多年，这是世界上持续时间最长的河流水质不间断监测记录。英国布里斯托尔大学等机构的研究人员以这些数据为基础展开了相关研究。
报告说，100多年来泰晤士河水的氮浓度基本呈上升势头，其中，第二次世界大战期间及此后一段时期氮浓度大幅上升，达到此前的两倍，随后在上世纪70年代再次大幅上升。
报告显示，其中的原因可能是英国在战时需要生产更多粮食，在泰晤士河流域开展农业耕作，不但把大片草地开垦为农田，还施用大量氮肥。农耕作业导致释放到土壤中的氮元素大幅增加，最终在70年代流入泰晤士河中。这种状况长期持续，虽然从70年代到现在，泰晤士河流域释放到土壤中的氮元素已逐渐下降，但泰晤士河水体中的氮浓度从那时起一直维持在高水平。
领导这项研究的尼古拉斯·豪登博士说，分析结果说明农业耕作对水体的氮污染影响可能需要几十年时间才会显现，虽然开辟耕地生产粮食很重要，但从长远来看，人们可能需要考虑粮食生产和水资源可持续利用之间的平衡。
氮元素是农业上常用的氮肥主要成分，土壤中一些有机质降解时也会释放出氮元素。如果水体中氮元素过多，会造成富营养化污染。（生物谷Bioon.com）
doi:10.1029/2011WR010843
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Nitrate pollution in intensively farmed regions: What are the prospects for sustaining high-quality groundwater?
Nicholas J. K. Howden,Tim P. Burt,Fred Worrall,Simon Mathias,Mick J. Whelan
Widespread pollution of groundwater by nutrients due to 20th century agricultural intensification has been of major concern in the developed world for several decades. This paper considers the River Thames catchment (UK), where water-quality monitoring at Hampton (just upstream of London) has produced continuous records for nitrate for the last 140 years, the longest continuous record of water chemistry anywhere in the world. For the same period, data are available to characterize changes in both land use and land management at an annual scale. A modeling approach is used that combines two elements: an estimate of nitrate available for leaching due to land use and land management; and, an algorithm to route this leachable nitrate through to surface or groundwaters. Prior to agricultural intensification at the start of World War II, annual average inputs were around 50 kg ha?1, and river concentrations were stable at 1 to 2 mg l?1, suggesting in-stream denitrification capable of removing 35 (±15) kt N yr?1. Postintensification data suggest an accumulation of 100 (±40) kt N yr?1 in the catchment, most of which is stored in the aquifer. This build up of reactive N species within the catchments means that restoration of surface nitrate concentrations typical of the preintensification period would require massive basin-wide changes in land use and management that would compromise food security and take decades to be effective. Policy solutions need to embrace long-term management strategies as an urgent priority.
