Behaviour of 14C-Malathion in North African Soils

Abstract

The degradation, movement and dissipation of malathion in a clay loamy soil from Bouchaoui (soil B) and a sandy soil from Staouali (soil S) were investigated under laboratory conditions using ¹⁴ C-labelled malathion. Data for soils spiked with ¹⁴ C-malathion indicated a good recovery that ranged from 83 to 90.5%. Degradation was more significant in the organic matter rich clay loamy soil (soil B) than the low organic matter sandy soil (soil S). After 80 d, the amount of ¹⁴ CO ₂ produced in non-sterile soil B was 33.05%, and 10.92 and 3.57%, respectively, for irradiated (1 Mrad) and autoclaved soil B. The activity of ¹⁴ CO ₂ in non-sterile soil S was 80%, and 23.3 and 23.4%, respectively, irradiated (1 Mrad) and autoclaved soil S. The movement of most of the applied dose in both soils remained in the upper 0–4 cm of the soil columns and radioscanning of TLC plates of extracts showed three degradation products. The bioavailability of ¹⁴ C-residues to wheat plants was also investigated. Within a few days, the uptake of radioactivity by the plants was 3.2 and 5.7% of the applied dose for Bouchaoui and Staouali soils, respectively. Ammonium nitrate partially inhibited the degradation of malathion with a more significant effect in Bouchaoui soil. Superphosphate triple had a stimulating effect on the degradation of malathion, particularly for Staouali soil.