Variation of plant p,p'-ddt uptake and its dissipation with age, temperature and soil type

Abstract

The extent to which insecticides may be absorbed and translocated from 14C_p,p'_ DDT contaminated soils into cowpeas plant tissues and the variation of uptake of p,p'- DDT by the plants in relation with the dissipation of p.p' -DDT in the soils was studied for three months (90 days) using a radio-nuclide tracer technique. Sampling was done biweekly and the residue levels were determined per dryweight of the plants and soil samples. Substantial absorption and accumulation of residue was observed for the cowpens grown in two different sites namely,in the coastal province, Mornbasa, Mtwapa, and highland region, Nairobi.chirorno campus. The degree of uptake also varied with soil type and growing conditions. A total residue level ranging from 0.945±O.040 pg/g to 7.765±O.211 !(g/g were obtained for 2 weeks old to 12 weeks old Mornbasa plants, respectively. For the Nairobi plants, the corresponding values fell in the range of 1.136±O.03R I'g/g to 3.239±O.007 I'g/g. The extractable and non-extractable (bound) residue levels in the plants and soil samples with respect to time were also determined for the two sites. The Mornbasa plants gave a range of residue levels from O.ROO±O.065 pg/g to 6.11O±O.038 11g/g and O.OR4±O.OOl I'g/g to 1.390±O.003 Ilg/g for extractable and non-extractable residue, respectively. The corresponding values for Nairobi samples were 1.034±O.Oll !1g/g to 2.241±O.014 !.lg/g and O.080~O.0021Ig/g to 0.411±O.007 l.lg/g, respectively. According to an experiment carried out for one Mornbasa plant sample which has been analysed for the residue accumulation in different parts of the plant namely, the