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New study reveals new pathway for river pollution

Scientists from the School of Biological and Chemical Sciences at Queen Mary University of London (QMUL) have discovered new ways how rivers convert excess nitrogen, which can have damaging impacts on the environment, to harmless nitrogen in a new study published in the journal Nature Geoscience.

30 March 2016

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Rivers play an important role by converting 40 per cent of excess nitrogen from polluting sources such as sewage and burning fossil fuels to benign nitrogen and return it to the atmosphere.

Writing in the journal Nature Geoscience, the team found a link between processes that remove excess nitrogen that operate without oxygen and another process that requires oxygen where that link strength depends on river type.

Lead author Professor Mark Trimmer from the School of Biological and Chemical Sciences, said: “Rivers carry human and natural waste towards the sea but they are far more than simple ‘pipes’ draining the landscape, as they have a large capacity to process and remove some of that waste for us en route.

“To date, rivers have been thought to remove this nitrogen waste through one microbiological pathway, namely denitrification. Here we show that a new microbiological pathway, known as anammox, helps by removing up to 50% in sandy and gravel riverbeds despite them being rich in oxygen.”

People may value rivers as nice places to walk, fish or row but they actually provide society with important, yet little appreciated, ecological ‘goods and services’. If we can harness their power to efficiently remove excess nitrogen by understanding just how anammox works in these rivers then, in the future, we might be able to build even more efficient sewage and waste water treatment works – removing the burden of man’s excess nitrogen on these precious resources.

The team used cutting edge laboratory techniques such as molecular analysis of microbes in clay, sand and chalk riverbeds and real life studies with tracers in the river Avon in Hampshire in southern England to examine the process of anammox.

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