Sorption and movement of pesticides on thin layer plates of Brazilian soils.

The sorption from aqueous solution (Table II), and movement in water on thin layers plates (Figure 1) of 7 soils (Table 1) of 3 organochlorine, 2 organophosphorus and 1 carbamate insecticide was determined in the laboratory. Generally, all substances were sorbed most and moved least on soils richest in organic matter. However, sorption was not a function of organic matter content alone (Table III). Aldrin and DDT were most strongly sorbed and did not move from the point of application on the thin layer plates of any soil. On all 7 soils, carbaryl was the least strongly sorbed insecticide. On 5 soils, lindane, parathion and malathion were increasingly strongly sorbed, but on the other 2 soils lindane was mostly strongly sorbed. The apparent greater mobility of 14C-labelled malathion on thin layers of soils repeatedly leached could be explained by the formation of more polar substances.