Degradation of 14C-atrazine bound residues in brown soil and rendzina fractions

The remobilization and the fate of 14C-ring labeled atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) bound residues was examined in relation with the turnover of natural soil organic matter. Soil fractions of a brown soil and a rendzina were incubated under controled laboratory conditions. The mineralization of natural organic matter and atrazine-bound residues was respectively estimated by the amounts of CO2 and 14CO2 evolved during the incubation. The remobilization and distribution of 14C residues among the soil organic fractions were achieved after physical-chemical extractions of the samples. Comparisons of samples in abiotic and biotic conditions allowed us to assess the influence of microbial activity on the fate of atrazine-bound residues. The mineralization curves showed that natural organic matter and atrazine-bound residues had similar decomposition patterns. After 100 d of incubation, 0.8 to 3.6% of total organic C was evolved as CO2, while only 0.1% of the initial radioactivity was mineralized as CO2, and 7 to 15% was becoming extractable with water and methanol. Few differences were observed in the distribution of residues within organic compounds for both fractions of the rendzina, except a decrease of the 14C radioactivity of the 50- to 5000-microm fraction and a slight increase of that of humin. For the 0- to 5000-microm brown soil fraction, increased radioactivity in humin at the expense of humic (HA) and fulvic (FA) acids was detected after incubation, while for the 0- to 50-microm fraction more radioactivity was recovered with FA.     

The environment and Britain's aid programme

Summary Some of the environmental and developmental activities assisted by Britain's Programme of Overseas Aid are outlined. In particular, the article draws attention to a new booklet published by the Overseas Development Administration to mark the European Year of the Environment which, in the Minister's words, shows how through British aid, programme improvements are possible by a combination of sound scientific research and a sensitivity to people's needs.Mr Christopher Patten, Member of Parliament for Bath, is the UK's current Minister for Overseas Development. He also serves as Minister of State for Foreign and Commonwealth Affairs. The Minister may be contacted through the offices of the Overseas Development Administration, Eland House, Stag Place, London SW1E 5DH, UK.