Leaching of aged DDTs and current use pesticide residues in undisturbed soil columns: non-ionic surfactant and carboxylic acids effects

GONZALEZ, MARIANA; MITTON, FRANCESCA; GRONDONA, SEBASTIAN; PEÑA, ARANCHA; MIGLIORANZA, KARINA

Congreso; 6th SETAC World Congress/SETAC Europe 22nd Annual Meeting; 2012

Soil pollution by Persistent Organic Pollutants such as DDTs (p´p´-DDT and its metabolites p´p´-DDE and p´p´-DDD) represents a continuous source to the environment. As a consequence of their high persistence DDTs occur up to 60 cm on agricultural soils. The Current Use Pesticide (CUP) endosulfan is characterized by its high lixiviation potential due to its relatively low Kow value. Introduction of riverine water on polluted soils during irrigation or flooding events as well as plant growing may modify pesticide availability and leaching. Surface waters receive discharges from industrial, urban and agricultural uses that will account for a variety of compounds such as surfactants, colloids and dissolved organic carbon. This work studies the vertical distribution and movement of aged DDTs and endosulfan in undistrurbed soil columns irrigated with: 1-control (riverine water), 2-Tw-80 (riverine water + Tween 80 0.5 cmc), and 3-acids (riverine water + sodium citrate and sodium oxalate, 0.05 M). Experiments were carried out with 13 cm x 30 cm soil columns taken from Aridisol soils from a fruit field in Patagonian, Argentina. Columns were saturated with distilled water and solutions (4L) were added under saturated condition. One L leachates (n=4) were collected for pesticide residues analysis. After elution, columns were dried (24 h), opened and sampling on 5 cm sections. Pesticide desorption was performed by batch technique and residues analysis on soil and water by GC-ECD. p´p´-DDE>p´p´-DDT>α- endosulfan>β-endosulfan pattern was found in all soil sections. p´p´-DDE levels ranged between 7-250, 8-70, and 13-200 ng g -1 dry weight in control, Tw-80 and Acids, respectively. Under all conditions pesticide levels decreased concomitantly with depth and sand increase. In control and Acids, p´p´-DDE and p´p´-DDT desorption from soil was correlated with their levels in soil (r>0.8 pAcids>Control. Under control or Acids, α-endosulfan was the main compound on the first elution volume and p´p´-DDE started to lixiviate after 2 L while for Tw-80, DDE represents the main residue in all elution waters. Lixiviation of aged p´p´-DDT residues or endosulfan effectively occurs under irrigation with riverine water and is increased by adding non-ionic surfactant or carboxylic acids. Tw-80 had a washing effect of pesticides leading to lower levels on soil while carboxylic acids enhance pesticides availability.