Wageningen University and Research Centre

Geo-engineering to clean up decades of phosphorus pollution in lakes

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Phosphorus is the biggest cause of water quality degradation worldwide, causing ‘dead zones’, toxic algal blooms, a loss of biodiversity and increased health risks for the plants, animals and humans. This threatens the loss of economic and social benefits from freshwaters. Miquel Lurling of the Aquatic Ecology group was lead author of a special issue of Water Research on the control of phosphorus pollution in lakes with geo-engineering.

After decades of run-off from agriculture, human sewage and industrial practices, phosphorus has been stock piled at an alarming rate in our lake bed sediments. The scale of the problem is daunting, and humans are still pumping about 10 million tonnes of extra phosphorus into our freshwaters every year. Long-term monitoring activities following the control of phosphorus sources to lakes show that plants and animals don’t recover for many years. This is because phosphorus stored in bed sediments is released back to the water column. Society then has to make a decision – either speed up recovery using geo-engineering to cap sediment phosphorus stores, or do nothing, and accept poor quality freshwaters for decades to come. Geo-engineering is contentious, costly, and the side effects are not well known. This special issue brings together 60 authors from 12 countries to present evidence on this approach.

Miquel Lurling explains that “The scale of this problem has driven the development of a vibrant green economy sector. Our special issue uncovered an alarming number of emerging materials being proposed for use in lakes. The potential for unintended side effects when using novel untested materials is high. A common conclusion of a number of papers was that it is essential to conduct comprehensive assessments of candidate lakes prior to any treatments. We reviewed these considerations in our editorial paper and stress the need to ensure the safe and effective use of this approach.”

With the recent introduction of water quality targets and deadlines for standing waters including the EU Water Framework Directive and the Clean Water Act in the USA, the need for approaches like geo-engineering is growing. About 40% of lakes in Europe are failing current water quality targets and combined economic losses in the USA associated with high phosphorus levels in freshwaters is estimated at $2.2 billion annually. There is a need to develop approaches that effectively control phosphorus pollution in freshwaters. This special issue draws on a wide range of laboratory and field scale experiments to produce the most comprehensive analysis of this approach for phosphorus management to date.

Geo-engineering in lakes is also being targeted at other environmental problems. Emerging approaches include the control of greenhouse gas emissions from lakes and the control of toxic cyanobacteria for human health. For example, geo-engineering approaches were utilized in the 2012 London Olympic Games, the 2014 Glasgow Commonwealth Games, and have been proposed for use in the upcoming 2016 Rio Olympic Games to ensure acceptable levels of health risk to athletes during open water events.

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