Assessment of pesticide availability in soil fractions after the incorporation of winery-distillery vermicomposts J.D. Ferna ´ndez-Bayo a, * , E. Romero a , F. Schnitzler b , P. Burauel b a Department of Environmental Protection, Estacio ´n Experimental del Zaidı ´n (CSIC), C/Profesor Albareda 1, 18008 Granada, Spain b Agrosphere Institute, ICG 4, Forschungszentrum Ju ¨lich, Ju ¨lich, Germany Received 8 August 2007; received in revised form 26 September 2007; accepted 6 October 2007 Winery vermicomposts as organic amendments to reduce pesticide pollution. Abstract The influence of two vermicomposts from winery and distillery wastes on the distribution of diuron in agricultural soil was studied. Physical soil fractionations at 0, 9, 27, 49 and 77 days, allowed the quantification of pesticide residues in different particle-size fractions, coarse waste (WF), sand-sized (SF), silt-sized (SiF), clay-sized (CF) and dissolved organic matter-sized fraction (DOM). The SiF made a greater contribution to the formation of non-extractable residues in unamended soil, but when vermicomposts were added, new sorption sites in WF appeared, being higher for the more humified vermicompost V2. The dissolved organic carbon (DOC) increased with the addition of vermicompost, but the con- centration of the desorbed 14 C-radiochemical did not increase. Non-significant increment was observed with time for the non-extractable fraction with amendments. Diuron was transformed in all samples, although less than 0.5% was mineralized. The main effect caused by vermicomposts was a reduction in the availability of diuron in soil. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Physical fractionation; Vermicompost; Diuron; Sorption; Dissolved organic carbon 1. Introduction Pesticides are necessary in crop production systems. How- ever, they become a problem when their residues move freely, as they impair water quality and pose a risk to human health and the ecosystem. This potential risk can be minimized and even avoided by various agricultural practices depending on the type of agricultural soil. Once a pesticide reaches the soil surface, it undergoes pro- cesses of sorption-desorption and diffusion that result in a distri- bution of the parent or its metabolites in different soil fractions (Wanner et al., 2005): a) non-extractable or bound, through covalent bonding, sequestration.; b) adsorbed, through Van der Waals forces, weak electrostatic interaction.; c) free, in the soil solution that can be degraded by microorganisms from the soil solution; and finally d) incorporated in microor- ganisms for metabolization and mineralization processes. The higher the sorption of pesticide residues and the longer the con- tact time with the soil matrix, the more strongly the compound is associated with soil components (ageing effect). The distri- bution of these residues in different soil fractions and the move- ment of the pesticide through soils are mainly related to: (i) soil properties which control water movement; (ii) pesticide-soil in- teractions, where organic carbon content is the most relevant characteristic; and (iii) weather patterns which controls the tim- ing of major leaching events (Walker et al., 2005). Thus, the ad- dition of exogenous organic matter (EOM) must contribute to the spatial distribution of pesticides encountered in different soil fractions (Se ´quaris et al., 2005), and consequently affect * Corresponding author. Department of Environmental Protection, Estacio ´n Experimental del Zaidin, CSIC, C/Profesor Albareda, 1, P.O. Box 419, 18008 Granada, Spain. Tel.: þ34 958 181 600x126; fax: þ34 958 129 600. E-mail address: jesus.bayo@eez.csic.es (J.D. Ferna ´ndez-Bayo). 0269-7491/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2007.10.002 Available online at www.sciencedirect.com Environmental Pollution 154 (2008) 330e337 www.elsevier.com/locate/envpol