A recent study conducted by ocean scientists from Florida State University, USA, provides evidence of the greater role of atmospheric nitrogen, rather than of ground sources, in controlling the nitrogen levels of rivers (Environmental Science & Technology, Vol 28, No 2).
It was widely believed that ground sources such as fertiliser runoffs from farmland and municipal waste streams contributed to the variation of nitrogen levels in rivers. But the Florida team, led by John Winchester, combined and analysed the data from 2 sources -- the acid rain measurements of the National Atmospheric Deposition Program and the river chemistry studies of the US Geological Survey -- to conclude that the atmospheric deposition of nitrogen plays a major role in water quality. Says Winchester, "Acid rain is the most important source of nitrogen."
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