2.1. Soil
Soils representative of the Argentinean Pampa (association of typical argiudols and udifluvent) were sampled from a soybean field near La Dulce village in the Río Quequen Grande watershed (S
38 11.70 2900 W 59 08.80 3600). Surface soils had a total pesticide
level (endosulfan, DDTs, HCHs, heptachlors, dieldrin and chlordanes)
lower than 2 106 mg g1, and comprised 1.9% organic
carbon, 60.7% sand, 31.8% silt and 7.3% clay (Gonzalez et al., 2010).
The soil samples were air-dried until constant weight, ground to
obtain a homogeneous matrix and maintained at 4 C before conducting
the experiment. Each soil sample was spiked by adding
technical endosulfan (Master R, Chemiplant S.A. 35%) dissolved in
acetone to achieve a final concentration of 10 mg g1. After the
solvent evaporated, the spiked soil was shaken for 30 days until a
homogeneous distribution of pesticides was achieved. Then, the
sample was maintained for one week at room temperature