Details

Autor(en) / Beteiligte

• Helling, C.S
• Engelke, B.F
• Doherty, M.A

Titel

DDT dissipation in Hawaiian in-situ soil columns

Ist Teil von

• Journal of environmental science and health. Part B, Pesticides, food contaminants, and agricultural wastes, 1994, Vol.29 (1), p.103-119

Ort / Verlag

Taylor & Francis Group

Erscheinungsjahr

1994

Beschreibungen/Notizen

• [ 14 C]DDT persistence and movement was monitored for 25 months after treatment of in-situ soil columns in Hawaii, USA. This was part of an international collaborative protocol coordinated by the International Atomic Energy Agency and carried out at 13 tropical locations. DDT metabolite DDE, and herbicide tebuthiuron, were included in the Hawaiian test for comparison with DDT. Persistence based on overall loss of radioactivity was described by first-order and two-compartment models: half-dissipation times were 53 and 25 weeks, respectively. The second model represented more accurately the rapid loss of 14 C during the first month after treatment. Time to 50% loss based on analysis of methanol-extractable 14 C was 66-68 weeks (both models), or somewhat shorter (40-53 weeks) when 14 C was measured in the final hexane solution before gas chromatographic (GC) analysis. Direct GC analysis of that solution gave 24 weeks (first-order) and 13 weeks (two-compartment) for DDT alone, and 30 weeks and 27 weeks, respectively, for the sum of DDT + DDE + DDD residues. After 10 months, further dissipation of either radioactivity or of DDT itself was very slow; the two-compartment model predicted 90% loss of methanol-extractable 14 C in 11 years and of DDT, in 3 years. Within 18 weeks post-DDT-treatment, metabolite DDE had reached a stable concentration of ca. 7% of added DDT. No DDD accumulated. Bound residue content was 10-15% by 2 years. [ 14 C]DDT and other radioactivity moved below the 10-cm leaching column by 3-4 months. By 25 months, 3% of the originally applied 14 C occurred deeper than 10 cm, or about 8% of the total 14 C then recovered. Little or no radioactivity migrated below 17.5 cm. Rainfall at the site averaged ca. 2500 mm y -1 . Tebuthiuron was less persistent than DDT; estimated half-life was ca. 12 weeks and the herbicide was much more mobile.