Assessing pesticide leaching and desorption in soils...

GONZALEZ MARIANA; MIGLIORANZA, K.; AIZPUN DE MORENO, J.; ISLA; PEÑA, ARANZAZU

CHEMOSPHERE

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2010 vol. 74 p. 1 - 12

0045-6535

Pesticide distribution in the soil profile depends on soil and pesticide properties as well as on the com-position of irrigation water. Water containing surfactants, acids or solvents, may alter pesticide desorp-tion from soil. The distribution of organochlorine pesticides (OCPs) in two Argentinean agricultural areas,Pampa and Patagonia, was evaluated. Furthermore, pesticide desorption from aged and freshly spikedsoils was performed by the batch technique, using solutions of sodium oxalate and citrate, dissolvedorganic  carbon  (DOC),  wastewater  and  surfactants.  Patagonian  soil  showed  the  highest  OCP  levels(46.5?38.1 lg g 1 OC) from 0 to 30 cm depth and the predominance of p,p0-DDE residues reflected anextensive and past use of DDT. Pampean soil with lower levels (0.039?0.07 lg g 1 OC) was mainly pol-luted by the currently used insecticide endosulfan. Sodium citrate and oxalate, at levels usually exudedby plant roots, effectively enhanced desorption of p,p0-DDT, p,p0-DDE and a-cypermethrin, while noeffects  were  observed  for  a-endosulfan  and  endosulfan  sulfate.  The  non-ionic  surfactant  Tween  80behaved similarly to the acids, whereas the anionic sodium dodecyl sulfate enhanced desorption of allpesticides. Increased desorption of the hydrophobic pesticides also occurred when DOC from humic acidsbut not from sewage sludge or wastewater were used. Soil profile distribution of pesticides was in accor-dance with results from desorption studies. Data suggest pesticide leaching in Pampean and Patagoniansoils, with risk of endosulfan to reach groundwater and that some organic components of wastewatersmay enhance the solubilisation and leaching of recalcitrant compounds such as p,p0-DDT and p,p0-DDE.