December 2006, Vol. 18, No.12

Research Notes

Research Notes 'Sound' Technology Used in Sediment Research

U.S. Agricultural Research Service (ARS; Washington, D.C.) scientists are researching a new method to study sediment movement: sound.

Hydraulic engineers Roger Kuhnle and Daniel Wren of the ARS National Sedimentation Laboratory in Oxford, Miss., and collaborators are using acoustics and automated sampling to assess how sediment affects waterways and dams. They are applying acoustic science to measuring the rate at which sand and gravel are transported in streams.

The resulting data can give insight about upstream erosion and — with help from computer modeling — fortify predictions about sediment’s impacts on waterbodies and related structures, according to an ARS news release.

This research, ARS states, is part of work by scientists in Oxford and at other ARS locations aimed at helping agriculture and waterways coexist in a cost-effective, environmentally friendly fashion. At the sedimentation lab, one research area focuses on how erosion, soil runoff, and urban and industrial activities affect water quality.

As part of this work, Wren and other collaborators are improving use of a core-drilling technique, called “vibracoring,” for gauging the impact of sediment on aging reservoirs. They are interested particularly in how vibracoring helps detect rates and patterns of sediment collection that affect reservoirs’ holding capacities.

Meanwhile, data collected from the Mississippi Delta region’s waterways is helping the scientists improve computer programs and models used to evaluate how different management practices can affect entire watersheds.

Agricultural engineer Ron Bingner is working with a water quality prediction technology called Annualized Agricultural Nonpoint Source to simulate environmental processes and evaluate their impact on downstream and adjacent watershed elements. Hydraulic engineer Eddy Langendoen is using field studies and a computer modeling technique he created called the Conservational Channel Evolution and Pollutant Transport System to assess the stability of specific channel reaches.

Read more about this research in the August issue of Agricultural Research magazine at www.ars.usda.gov/is/AR/archive.  

Edible Oil Could Aid Contaminant Cleanup

Oil and water don’t mix. This could explain why edible vegetable-based oil seems to keep the groundwater supply contaminant-free.

Clemson University (Clemson, S.C.) researchers, in conjunction with the Savannah River National Laboratory (SRNL; Aiken, S.C.), are testing vegetable oil as a way to prevent contaminants from getting into groundwater aquifers. In a university news release, researchers say the method has the potential to help clean up chlorinated solvents, which are among the most common groundwater contaminants caused by industry.

The study, being conducted at the U.S. Department of Energy’s Savannah River Site, is funded with a $35,000 grant from the South Carolina Universities Research and Education Foundation.

Clemson University geologist Larry Murdoch said the oil is injected through hydraulic fractures made 6 to 9 m (20 to 30 ft) deep in the ground. When injected, the vegetable oil draws in oil-based contaminants that have leaked from pipes or tanks. If mixed with water, the contaminants separate as droplets, with small amounts dissolving into the water and making it hazardous, the news release states. But if another oil is introduced, the contaminants steer clear of the water and are drawn instead toward the edible-oil source.

“Something else can happen to clean up the contaminants,” Murdoch said. “Some microbes in the ground subsurface will degrade solvents. The edible oils create the right conditions for those kinds of microbes to flourish, so they seek out the contaminants and break them down. We hope the oil will both trap and destroy contaminants underground.”

Since February, SRNL investigators have monitored levels of contaminant vapors and other indicators to determine whether the oil is attracting the contaminants at the test site. Murdoch said preliminary results are exciting, suggesting the process is working as anticipated.

Contact Murdoch at lmurdoc@clemson.edu for more information.  

Water Filtration Technique Removes Dangerous Freshwater Algae Toxins

 Not only is it green and icky, it’s toxic to humans. “It” is Microcystis, a blue-green alga native to U.S. freshwater lakes and rivers nationwide. It secretes toxins that can cause liver damage in animals, including humans. Worsening environmental pollution in Lake Erie during the last decade has caused algal blooms, the most recent of which began in August.

But now, a water filtration technique normally used to clean up agricultural chemicals has been found to be effective at removing a toxin secreted by algae found in lakes and rivers, according to an Ohio State University (OSU; Columbus) study. Engineers determined that the technique greatly outperformed other methods by removing at least 95% of a toxin secreted by the blue-green algae, an OSU news release states.

Some U.S. water filtration plants already use the technique, which couples activated carbon with membrane filters, said Hal Walker, associate professor of civil and environmental engineering and geodetic science at OSU.

Some 13 million people rely on Lake Erie for their water supply, so Microcystis is a growing concern there, Walker said. But dangerous algal blooms have occurred nationwide this summer, from Massachusetts to California, according to an OSU press release. While many water filtration plants are beginning to use high-tech ultrafiltration membranes with very fine holes, Microcystin toxins are small enough to slip through. For example, the toxin used in the study was microcystin-lr, a tiny molecule consisting of only seven amino acids.

The research findings will appear in the journal Environmental Science & Technology and have been published in advance on the journal’s Web site.

Rather than invent a new technology for filtering microcystin-lr, Walker and his colleagues decided to test whether combining activated carbon with membrane filters would do the trick. This technology already has proven effective in removing herbicides and pesticides from drinking water.

“This toxin is an organic molecule, and we knew that activated carbon is good at removing organics,” Walker said, “so we coupled the carbon with membranes. Together, they provide a way for water treatment plants to remove the toxin by basically upgrading the membrane system they already have.”
Water treatment plants that already have membranes in place could add carbon to their systems without purchasing new equipment, Walker added.

The engineers combined the active carbon with three different commercially available membrane filters to remove microcystin-lr from samples of Lake Erie drinking water. Each combination produced good results: One removed 95% of the toxin, one removed 97%, and the other removed 99%. Without the carbon, even the most effective ultrafiltration membrane removed only 78% of the toxin, OSU reports.
Contact Walker at walker.455@osu.edu.

Bringing Wetlands to the Farm

 Wetlands are a useful tool for farmers, helping filter impurities out of waterways, and helping keep excess crop nutrients and livestock waste out of rivers and streams. Unfortunately, according to the U.S. Agricultural Research Service (ARS), most farmers and ranchers aren’t located near wetlands, so scientists at ARS’ Coastal Plains Soil, Water and Plant Research Center in Florence, S.C., are exploring the use of constructed wetlands to bring these natural filters to farmers.

The Florence lab addresses a problem unique to its region: Soils in the southeast coastal plain are very sandy and hold very little water. This makes runoff from farms and livestock operations an especially big problem that has grown during the past decade as animal production has increased, ARS states.
In studies, ARS scientists Patrick Hunt, Ariel Szogi, Kenneth Stone, and other Florence researchers have found that constructed wetlands can remove about half of the total suspended solids and about 60% of the nitrogen from water.

According to Hunt, the keys to constructed wetlands systems are marsh plants, aeration, and drainage. The wetlands system must have a sloped bottom and shallow water at the entry point. The shallow water ensures crucial interaction with oxygen.

Read more about this research in the August issue of Agricultural Research magazine at www.ars.usda.gov/is/AR/archive.

Tomorrow’s Superstorms May Speed Erosion

Rainstorms 50 to 100 years from now may be more intense and more frequent than today’s, and may pack more soil-eroding power, according to a news release issued by the U.S. Agricultural Research Service (ARS).

Stormwaters running off landscapes — orchards, vineyards, even hilly backyards or parklands — could increase by 20% to 30% in some parts of the United States, ARS scientists estimate. In turn, the runoff might wash away 25% to 50% more soil, the researchers’ experiments suggest.

Scientists based the estimates on an array of factors, including the presumption that the U.S. climate trends of the past 100 years, as well as farming practices, will continue along the same lines, according to Mark A. Nearing, a soil scientist who heads the ARS Southwest Watershed Research Center in Tucson, Ariz. Researchers can use these findings and others to get a better idea of the possible soil-erosion consequences of global climate change. That foundation could lead to better ways to protect vulnerable topsoil from the erosive force of future thunderstorms.

Read more about the study in the September 2006 issue of Agricultural Research magazine at www.ars.usda.gov/is/AR/archive. Contact Nearing at mnearing@tucson.ars.ag.gov.