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 plants, animals and humans that come in contact with polluted waters. This threatens the loss of economic and social benefits from freshwaters upon which society relies. Now, in a series of studies published in a new special issue of Water Research, leading scientists assess how geo-engineering in lakes can control phosphorus pollution.
After decades of run-off from agriculture, human sewage and industrial practices, phosphorus has been stockpiled at an alarming rate in lake bed sediments. The scale of the problem is daunting, and humans are still pumping about 10 million tonnes of extra phosphorus into freshwaters every year.
Photo: Geo-engineering applications of a modified zeolite product called Aqual-P at Lake Ōkaro, New Zealand. Image courtesy of Andy Bruere, Bay of Plenty Regional Council, New Zealand.
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.
With the introduction in many countries of water quality targets and deadlines for standing waters, the need is growing for approaches like geo-engineering to effectively control phosphorus pollution in freshwaters. The special issue of Water Research 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 is contentious, costly, and the side effects are not well known. The new issue brings together 60 authors from 12 countries to present evidence on the approach.
Bryan Spears, a Freshwater Ecologist at the Centre for Ecology & Hydrology, was a lead author and guest editor of the special issue. He said, “Our papers assessed the ecological and chemical responses across more than 100 lake treatments from around the world. It’s safe to say the approach is widespread and global. Most case studies used either aluminium salts or lanthanum-modified bentonite additions to control phosphorus. The responses were highly variable across the lakes.
"In some cases dramatic and sudden improvements were reported in chemical and ecological quality, in others nothing really happened, or the responses were short-lived. To improve confidence in the use of the approach a series of papers presented models to predict responses in candidate lakes. One key conclusion is that although this mitigation approach is promising when used correctly and in combination with catchment management, it should not simply be used to off-set the effects of poor environmental behavior.”
"One key conclusion is that although this mitigation approach is promising when used correctly and in combination with catchment management, it should not simply be used to off-set the effects of poor environmental behavior.” Dr Bryan Spears, Centre for Ecology & Hydrology.
Miquel Lürling, Freshwater Ecologist at the University of Wageningen, the Netherlands and another guest editor, said, “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.”
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 used 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.
The special issue of Water Research was led by the University of Wageningen (The Netherlands), The Centre for Ecology & Hydrology (UK), and the University of Southern Denmark (Denmark).
The featured articles are:
- “Editorial – A critical perspective on geo-engineering for eutrophication management in lakes” by M Lurling, E Mackay, K Reitzel, B M Spears. Water Research 2016. doi:10.1016/j.watres.2016.03.035.
- “A meta-analysis of water quality and aquatic macrophyte responses in 18 lakes treated with lanthanum modified bentonite (Phoslock®)” by B M Spears, E B Mackay, S Yasseri, I D M Gunn, K E Waters, C Andrews, S Cole, M De Ville, A Kelly, S Meis, A L Moore, G K Nürnberg, F van Oosterhout, J A Pitt, G Madgwick, H J Woods, M Lürling. Water Research. 2016. doi:10.1016/j.watres.2015.08.020.
- “Longevity and effectiveness of aluminum addition to reduce sediment phosphorus release and restore water quality,” by B J Huser, S Egemose, H Harper, M Hupfer, H Jensen, K M Pilgrim, K Reitzel, E Rydin, M N Futter. Water Research. 2016. doi:10.1016/j.watres.2015.06.051.
Water Research is a joint publication of Elsevier and the International Water Association (IWA). It is the top scientific journal in the field of science and technology of water quality, water technology and water management worldwide.