Abstract
This study evaluated the effects of total and dissolved organic matter produced from two swine wastewater treatment systems, a biodigester and a manure lagoon, on the adsorption, desorption, and leaching of alachlor (2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide) in soil. It was used the batch equilibrium method to test adsorption and desorption, and the results are presented in Freundlich isotherms. It also used disturbed soil columns to evaluate the miscible displacement of alachlor in soil treated with total and dissolved organic matter. This assay was used to monitor the concentration of alachlor in the leached material, the amount of total organic carbon, and the pH. The addition of swine wastewater promoted greater adsorption and desorption of alachlor compared with the control. The dissolved organic matter promoted less soil adsorption of alachlor compared with the total organic matter and also interacted with the alachlor and/or competed with the exchangeable cation sites in the soil, resulting in greater leaching. The total organic matter contributed to the emergence of new sorption sites in the soil column, and the solids present in the composition may have blocked pesticide passage, resulting in lower loss of alachlor due to leaching.
Highlights
It is increasingly common to detect significant concentrations of pesticides and their metabolites in surface water (VECCHIA et al, 2009), underground water (POSTIGO et al, 2010), food, and soil (ABRANTES et al, 2010).Swine-cultivating areas stand out in this regard due to their intense cultivation of corn, which is produced for animal feed
The treatments were assigned as follows: Control (no addition of swine wastewater (SWW)), TOM-B, Dissolved organic matter (DOM)-B, TOM-L, and DOM-L
Other authors have observed this behavior with chloroacetamide pesticides and with different methods of adding organic carbon to soil (ARCHANGELO et al, 2004)
Summary
It is increasingly common to detect significant concentrations of pesticides and their metabolites in surface water (VECCHIA et al, 2009), underground water (POSTIGO et al, 2010), food, and soil (ABRANTES et al, 2010). Swine-cultivating areas stand out in this regard due to their intense cultivation of corn, which is produced for (among other purposes) animal feed. Various herbicides are used in the cultivation of crops. One of these is alachlor, a pre-emergence herbicide used to control weeds that affect cotton, soybean, peanut, coffee, sugarcane, corn, and rice crops. According to Li et al (2005), when applied to the soil, pesticides can be adsorbed by plants, volatilized into the atmosphere, photodegraded by the sun, adsorbed into soil particles, leached, lost by surface runoff, erosion, drainage or lateral subsurface flow
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