Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2005
Publication Date: 1/5/2006
Citation: Shinde, D., Nkedi-Kizza, P., Savabi, M.R., Ouyang, Y., Nieves, L. 2006. Sorption kinetics and equilibria of organic pesticides in calcareous soils from south Florida. J. Environmental Quality. 35:268-276. Interpretive Summary: Surface and groundwater contamination resulting from application of agricutural chemicals is a national concern. In a nationwide survey of pesticide loading to coastal regions, Miami-Dade County in south Florida ranked second in agricultural application when adjusted for amount and toxicity of current-use pesticides. The Miami-Dade County agricultural area is of importance due to its proximity to the Everglades National Park (ENP) and Florida Bay. Concern in Miami-Dade County is shallow soil depth (15-60 cm) of major agricultural soils. Very little data are available in the literature for the sorption kinetics and equilibria parameters of herbicides for South Florida calcareous (carbonatic) soils. Application practices for the herbicides, combined with the high annual rainfall in this region, could result in significant amounts reaching non-target sites in the environment
Technical Abstract: Sorption kinetics and equilibria parameters play an important role in determining the fate and transport of organic chemicals in the environment. A batch reactor was used to determine sorption kinetic parameters (k2 and F) and the equilibrium sorption coefficient (K) for two pesticides (atrazine and diuron) in three calcareous soils from south Florida (Chekika, Perrine, and Krome) and one non-calcareous soil from Iowa (Webster) and one organic soil (Lauderhill) from Florida. Diruon, with higher Koc value, had higher sorption kinetics in the soils tested compared to atrazine. The Lauderhill soil (peat) which has almost OC of 45 % shows most kinetics for sorption of both pesticides tested. This determine that soil organic carbon content generally correlates well with pesticide adsorption. All sorption equilibrium isotherms were linear. The sorbate (for all soils) initial concentration did not have an effect on the sorption kinetics of atrazine and diuron. Sorption is initially very fast up to about 3 hours and then slowly reaches equilibrium. All soil-chemical combinations reached sorption equilibrium after 24 hours.