Forest organic runoff breaks down faster than agricultural, urban runoff

Apr 15, 2013

Dissolved organic matter in streams and rivers can be broken down by sunlight or bacteria, providing a fuel source for aquatic ecosystems and affecting carbon dioxide and carbon monoxide concentrations as the organic matter is mineralized. Researchers know that the amount of organic matter in streams fed by forest landscapes and those fed by watersheds affected by human activity, such as croplands, pasture, or urban environments, can differ greatly. What is less well known is how the organic matter from these various environments evolves as it flows downstream.

Taking water samples from the heads of seven Virginia rivers, Lu et al. studied how bacterial and photochemical reactions changed the concentration, , and fluorescent properties of dissolved organic compounds. The authors find that the organic matter stemming from forested environments is more susceptible to degradation by sunlight than that from landscapes affected by human activity. This differing rate of photochemical degradation means that for streams affected by farm and urban runoff the organic loads remain at higher levels longer, resulting in greater organic content at the river outlet and an increased potential for driving hypoxic conditions in downstream waterways.

The authors suggest that the higher persistence of anthropogenic dissolved organic compounds could help explain an observed long-term increase in river organic compound concentrations in Europe and North America. The authors also suggest that the forest-derived dissolved organic compounds may be more photoreactive because they haven't been exposed to as much light as those from landscapes affected by human activity, or because the produced by plants rather than bear varied . They note, however, that more research is needed to determine the exact cause.

Explore further: 'Shocking' underground water loss in US drought

More information: Photochemical and Microbial Alteration of Dissolved Organic Matter in Temperate Headwater Streams Associated with Different Land Use, Journal of Geophysical Research-Biogeosciences, doi:10.1002/jgrg.20048, 2013 . http://onlinelibrary.wiley.com/doi/10.1002/jgrg.20048/abstract

add to favorites email to friend print save as pdf

Related Stories

Dams impact carbon dynamics in U.S. rivers

Aug 08, 2012

Dissolved organic carbon (DOC)—which leaches into freshwater systems from plants, soils, and sediments, and from other detritus present in the water itself—is the major food supplement for microorganisms and plays ...

Glacial organic matter and carbon cycling

Sep 17, 2012

An international collaboration led by Tom Battin from the Department of Limnology of the University of Vienna unravels the role of Alpine glaciers for carbon cycling. The scientists uncover the unexpected ...

Hurricane Irene polluted Catskills watershed

Sep 26, 2012

(Phys.org)—The water quality of lakes and coastal systems will be altered if hurricanes intensify in a warming world, according to a Yale study in Geophysical Research Letters.

Optical water quality assessment

Dec 14, 2010

Scientists at the U.S. Geological Survey (USGS) have proven that measuring fluorescence could improve source water monitoring during a study of the McKenzie River in Oregon. The study was designed to assess ...

Recommended for you

'Shocking' underground water loss in US drought

8 hours ago

A major drought across the western United States has sapped underground water resources, posing a greater threat to the water supply than previously understood, scientists said Thursday.

User comments : 0