Washington, Nov.22: An international team, led by researchers from the University College London and the US Environmental Protection Agency (EPA), has demonstrated that the stained brown colour of lakes and streams in remote parts of the UK, southern Scandinavia and eastern North America, is indicative of their return to a more natural, pre-industrial state following a decline in the level of acid rain.

“A huge amount of carbon is stored in the form of organic deposits in soils, and particularly in the peat lands that surround many of our remote surface waters. In the past two decades an increasing amount of this carbon has been dissolving into our rivers and lakes, turning the water brown,” said Don Monteith, Senior Research Fellow at the UCL Environmental Change Research Centre.

John Stoddard of the EPA says: “By analysing water chemistry records from over 500 sites across the northern hemisphere we’ve found that the dominant factor in the whole process is not global warming. The most important driver has actually been the major reduction in acid rain since the 1970s.”

“In some ways we’re seeing waters returning to their natural, pre-industrial state. However, more research is needed into the implications for freshwaters. The environmental pathways of heavy metals like aluminium and mercury, for
example, are closely tied to dissolved organic carbon, and it’s too early to know how increasing organic matter will affect these toxic compounds,” said Chris Evans, from the UK Centre for Ecology and Hydrology.

Data for this study was drawn from nationally funded monitoring programs in the UK, USA, Canada, Norway, Sweden and Finland.

The study, which has been published in The Nature, is the largest of its kind and the data represents the main source of high quality, long-term information about the condition of our headwater systems. (ANI)