近日，英國一個研究團(tuán)隊在最新一期的《水資源研究》雜志上發(fā)表了他們研究成果"Nitrate pollution in intensively farmed regions: What are the prospects for sustaining high-quality groundwater",，研究人員對泰晤士河140多年來的水質(zhì)監(jiān)測數(shù)據(jù)進(jìn)行分析后指出,，現(xiàn)代農(nóng)耕技術(shù)雖然確保了糧食供應(yīng),，但也對河水資源造成了長期的氮污染。
在英國,，對泰晤士河水質(zhì)的監(jiān)測已持續(xù)了140多年,，這是世界上持續(xù)時間最長的河流水質(zhì)不間斷監(jiān)測記錄。英國布里斯托爾大學(xué)等機(jī)構(gòu)的研究人員以這些數(shù)據(jù)為基礎(chǔ)展開了相關(guān)研究,。
報告說,，100多年來泰晤士河水的氮濃度基本呈上升勢頭，其中,，第二次世界大戰(zhàn)期間及此后一段時期氮濃度大幅上升,，達(dá)到此前的兩倍,，隨后在上世紀(jì)70年代再次大幅上升。
報告顯示,，其中的原因可能是英國在戰(zhàn)時需要生產(chǎn)更多糧食,，在泰晤士河流域開展農(nóng)業(yè)耕作，不但把大片草地開墾為農(nóng)田,，還施用大量氮肥,。農(nóng)耕作業(yè)導(dǎo)致釋放到土壤中的氮元素大幅增加，最終在70年代流入泰晤士河中,。這種狀況長期持續(xù),，雖然從70年代到現(xiàn)在，泰晤士河流域釋放到土壤中的氮元素已逐漸下降,，但泰晤士河水體中的氮濃度從那時起一直維持在高水平,。
領(lǐng)導(dǎo)這項研究的尼古拉斯·豪登博士說，分析結(jié)果說明農(nóng)業(yè)耕作對水體的氮污染影響可能需要幾十年時間才會顯現(xiàn),，雖然開辟耕地生產(chǎn)糧食很重要,，但從長遠(yuǎn)來看，人們可能需要考慮糧食生產(chǎn)和水資源可持續(xù)利用之間的平衡,。
氮元素是農(nóng)業(yè)上常用的氮肥主要成分,，土壤中一些有機(jī)質(zhì)降解時也會釋放出氮元素。如果水體中氮元素過多,，會造成富營養(yǎng)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.
