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

GONZALEZ, MARIANA; MITTON, FRANCESCA MARIA; GRONDONA, SEBASTIÁN; PEÑA, ARANZAZU; MIGLIORANZA, KARINA SILVIA BEATRIZ

Berlin

Congreso; 6th Society of Environmental Toxicology and Chemistry World Congress; 2012

SETAC

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 works study the vertical distribution and movement of aged DDTs and endosulfan in undistrurbed soil columns under: a. control (riverine water), b. Tw-80 (riverine water + Tween 80 0.5 cmc), and c. 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 Aridisols soil from a fruit field in Patagonian, Argentina. Columns were saturated with distilled water and 4 L of solutions were added under this condition. One L lechates (n= 4) were collected for pesticides 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>a-endosulfan>b-endosulfan pattern was found in all soil sections. 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 decrease concomitantly with depth and sand increase. Total pesticide levels in elution waters followed the order Tw-80>Acids>Control. Under control or Acids a-endosulfan was the main compound on the first elution volume and p´p´-DDE started to lixiviate after 2 liters while for Tw-80 DDE represents the main residue in all elution waters. In control and Acids, p´p´-DDE and p´p´-DDT desorption from soil was correlated with their levels in soil (r>0.8 p