Don't judge a brook by its color -- brown waters are more natural

Over the last 20 years lakes and streams in remote parts of the UK, southern Scandinavia and eastern North America have been increasingly stained brown by dissolved organic matter. In this week’s Nature journal (22 November) an international team, led by researchers from UCL (University College London) and the US Environmental Protection Agency (EPA), demonstrates that the colour change is indicative of a return to a more natural, pre-industrial state following a decline in the level of acid rain.

Don Monteith, Senior Research Fellow at the UCL Environmental Change Research Centre, says: “A huge amount of carbon is stored in the form of organic deposits in soils, and particularly in the peatlands 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.

“There have been numerous attempts to explain what’s happening, with everything from global warming to changing land-use cited as the cause. Some studies have suggested that we’re seeing an unprecedented phenomenon as soils destabilise with unpredictable consequences for the global carbon cycle.”

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. As acidity and pollutant concentrations in the soil fall, carbon becomes more soluble, which means more of it moves into our lakes and rivers and more can be exported to the oceans.

“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.

Chris Evans, from the UK Centre for Ecology and Hydrology, adds: “The suggestion that waters are returning to more natural conditions may be of little consolation to water supply companies as they are faced with the increasingly difficult - and expensive – task of removing the colour from drinking water using treatment facilities that were designed to deal with the lower concentrations experienced in previous years.”

Data for this study was drawn from nationally funded monitoring programs in the UK, USA, Canada, Norway, Sweden and Finland. Trends in dissolved organic carbon, air temperatures and a suite of other chemical variables were assessed using data from 1990-2004. The study 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.

Ironically many of the study sites, including those in the UK, are under threat of imminent closure or scaling back due to cuts in government funding. This comes despite increasing recognition of the urgent need to monitor the response of natural environments to climate change and other man-made pressures, and the obvious value of these records for increasing our understanding of environmental processes.

Source: University College London

Related stories:

New Study Finds Increasing Acidification of Pacific Ocean’s Continental Shelf
An international team of scientists surveying the waters of the continental shelf off the West Coast of North America has discovered for the first time high levels of acidified ocean water within 20 miles of the shoreline, raising concern for marine ecosystems from Canada to Mexico.
Novel enzyme inhibitor paves way for new cancer drug
Combining natural organic atoms with metal complexes, scientists at The Wistar Institute have developed a new type of enzyme inhibitor capable of blocking a biochemical pathway that plays a key role in cancer development.
Addressing the 'nitrogen cascade'
While human-caused global climate change has long been a concern for environmental scientists and is a well-known public policy issue, the problem of excessive reactive nitrogen in the environment is little-known beyond a growing circle of environmental scientists who study how the element cycles through the environment and negatively alters local and global ecosystems and potentially harms human health.
Ponds found to take up carbon like world's oceans
Research led by Iowa State University limnologist, or lake scientist, John Downing finds that ponds around the globe could absorb as much carbon as the world's oceans.
65-million-year-old asteroid impact triggered a global hail of carbon beads
The asteroid presumed to have wiped out the dinosaurs struck the Earth with such force that carbon deep in the Earth's crust liquefied, rocketed skyward, and formed tiny airborne beads that blanketed the planet, say scientists from the U.S., U.K., Italy, and New Zealand in this month's Geology.
Environmental fate of nanoparticles depends on properties of water carrying them
The fate of carbon-based nanoparticles spilled into groundwater – and the ability of municipal filtration systems to remove the nanoparticles from drinking water – depend on subtle differences in the solution properties of the water carrying the particles, a new study has found.
Wakame waste
Bacteria that feed on seaweed could help in the disposal of pollutants in the world's oceans, according to a new study by researchers in China and Japan. The discovery is reported in the International Journal of Biotechnology.
Scientists say biodiversity is crucial to ecosystem productivity
In the first experiment involving a natural environment, scientists at Brown University have shown that richer plant diversity significantly enhances an ecosystem's productivity. The finding underscores the benefits of biodiversity, such as capturing carbon dioxide, a main contributor to global warming.

News discussion:

Space & Earth science news