April 2010, Vol. 22, No.4
Pesticides Decline in Corn Belt
Declines in pesticide concentrations in waterways of the U.S. Corn Belt directly correspond to the amount of pesticides applied, according to a U.S. Geological Survey (USGS) news release. The Corn Belt is an area of intense agricultural activity that stretches across Illinois, Indiana, Iowa, Nebraska, and Ohio, as well as portions of adjoining states. From 1996 to 2006, the concentrations in rivers and streams of several commonly used pesticides declined or remained the same in this area. This change follows declines in annual applications of those compounds, a USGS study says.
The USGS study, conducted during two overlapping time periods (1996 to 2002 and 2000 to 2006), analyzed 11 herbicides and insecticides at 31 stream sites in the Corn Belt. This area has one of the highest levels of pesticide use in the nation — primarily from herbicides used to control weeds in corn and soybean fields. Runoff from cropland and urban areas is largely responsible for the widespread distribution of pesticides in the area’s waterways.
The study included many common pesticides — specifically, the herbicides atrazine, acetochlor, metolachlor, alachlor, cyanazine, s-ethyl dipropylthiocarbamate, simazine, metribuzin, and prometon, as well as the insecticides chlorpyrifos and diazinon.
Only concentrations of simazine, which is used for both agricultural and urban weed control, increased during the study. The release states that an increase in nonagricultural use of the herbicide is suspected, since concentrations were found to increase more sharply than its trend in agricultural use.
U.S. Environmental Protection Agency regulation of the herbicides cyanazine, alachlor, and metolachlor, as well as the phaseout of nonagricultural use of the insecticide diazinon, were found to correspond to the decline in the pesticides’ concentrations in waterways, the news release says.
Even though trends in concentration and use were closely related, concentrations of atrazine and metolachlor each declined in one stream more rapidly than their estimated use. This decline could be related to agricultural management practices that reduced the transportation of the pesticides, according to Skip Vecchia, senior author of the USGS report.
The report, Trends in Pesticide Concentrations in Corn-Belt Streams, 1996–2006, is accessible at http://pubs.usgs.gov/sir/2009/5132.
Discovery May Lead to Nanoparticle Removal From Wastewater
A new discovery could make it easier to manage nanoparticles. Scientists have identified a potential way to remove nanoparticles from wastewater during primary wastewater treatment.
Scientists from the Centre for Ecology and Hydrology (CEH; Wallingford, England) and the Science and Technology Facilities Council’s ISIS facility (Didcot, England), with assistance from King’s College London and Oxford University (England), studied how silica nanoparticles, commonly found in consumer products, behave in wastewater, according to a CEH news release. Researchers used the ISIS Neutron Source — technology that acts like a large microscope, enabling scientists to study objects 1000 times thinner than a human hair — to view the wastewater at the nanometer scale, the news release says.
The study simulated primary wastewater treatment to show that coating silica nanoparticles with a surfactant made the nanoparticles interact with components of the wastewater to form solid sludge, which can be separated from wastewater and disposed of, the news release says. Uncoated nanoparticles remained dispersed in the wastewater and were likely to pass through the treatment system unfettered.
Consumer products frequently contain silica nanoparticles. According to the release, a large proportion of these are washed into the wastewater system, making treatment plants a major gateway for nanoparticles to enter the aquatic environment.
“The research proves that the surface chemistry of nanoparticles influences their likely removal during primary sewage treatment,” said CEH’s Helen Jarvie, according to the release. “By adding a coating, which modifies that surface chemistry, it may be possible to reroute their journey through sewage treatment plants.” Jarvie explained that further work is planned to examine the behavior of a wider range of nanoparticles and different classes of surfactants in wastewater.
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