DICHLORVOS BEHAVIOUR IN SOILS: APROACH TO LEACHING PROCESS

ANALIA IRIEL,; PARASKEYAS PARLAKIDIS; ALICIA FERNÁNDEZ CIRELLI; NAHUEL J BUSTOS; ZISIS VRIZAS

Conferencia; 14th International IUPAC Conference of Crop Protection; 2019

Agricultural soils are the principal receiver of pesticide residues used in crops and livestock. Their persistence depends on the following principal mechanisms; volatilization, adsorption, leaching, runoff, and degradation (biotic or abiotic). Dichlorvos (DDVP) is an organophosphorous pesticide mainly used in field, post-harvest treatments and animal production to control common pests. The study of DDVP mobility in agroecosystems helps to identify which environmental compartments are the most affected and thus, evaluate remediation and risk management strategies. DDVP mobility was studied trough column assays in two soils belonging to the main agriculture areas in Argentina (Pampa Plain). Selected soils were characterized as A) Clay loam, organic matter 4.57% and cationic exchange capacity 16.22 cmol Kg−1; and B) sandy loam, organic matter 1.55% and cationic exchange capacity 10.28 cmol Kg−1. Thus, a DDVP aqueous solution of 50 mg L-1 was passed through a soil column (length of 5 cm and 3 cm diameter) with a flux of 1.1 mL min-1 (equivalent to a rain of 86 mm). Effluent samples were collected during 2 h and DDVP concentrations were measured by using HPLC equipment. Results indicated that columns had piston flow behaviour in the studied conditions where adsorption capacities were 0.183 and 0.081 mg g-1 for A and B soils, respectively. Adsorption processes were properly described by the Thomas model where equilibrium adsorption amount (q0Th) and the Thomas model constant (KTH) parameters were calculated. Particularly q0Th were 7.437 mg g-1 and 4.977 mg g-1 for soils A and B, respectively and, KTH were 0.016 mL min-1g-1 and 0.074 mL min-1g-1 or soils A and B, respectively. Additionally, removal (%) for A and B soils were 36.44 and 9.73, respectively. These results are in agreement with the observed ones in preliminary batch experiments.