Treatment of Agriculture Runoff with Enzyme and Vegetation Removes Pesticides and Associated Toxicity
The coastal valleys of central California are considered the nation's salad bowl, forming the heart of the most productive vegetable producing region in the United States. This region contains year-round, intensively cultivated agricultural land supporting a nearly $5 billion/year industry producing most of the nation's salad greens, artichokes, and crucifer crops. Runoff from irrigated agriculture constitutes a significant portion of stream flow in the region during much of the year, and a number of studies have documented pesticide occurrence, toxicity, and biological impacts in the rivers and estuaries of several watersheds in the region. State and federal regulators rely on chemical and biological monitoring to track water quality in Californian watersheds. Biological monitoring in laboratory experiments includes toxicity testing, where invertebrates such as water fleas (Daphnia) and other shrimp-like organisms are exposed to field run-off in laboratory experiments to determine if the water is clean enough to support life. The term "toxicity" in this case refers to survival in an ambient water sample that is statistically lower than survival in a control sample. A growing body of evidence has shown that farm runoff in California is polluted with toxic levels of pesticides, and that these pesticides affect insect communities in watersheds throughout the state. Monitoring of urban runoff has shown similar results. Evidence of toxicity and other water quality impacts has motivated a diverse range of farmers, researchers, farm advisers, and water quality regulators to begin implementing farm management practices to reduce nutrients, pesticides, and toxicity in agricultural runoff. Based largely on the results of recent research showing effectiveness of grass-lined ditches and constructed wetlands at reducing pesticides in water, researchers have begun to emphasize these practices for use in Californian agriculture. Farm owners and managers have worked with technical specialists to design and construct ditch, wetland, and pond vegetated treatment systems (VTS) at a variety of locations in Central California.
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Document Type: Research Article
Publication date: 01 October 2011
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