DDT in forest streams.

Water was sampled from a tributary of the Miramichi River of New Brunswick before, during, and up to two years after the final operational application of DDT to this area of forest. Gas chromatographic analysis of petroleum ether extracts of the water showed that only during and for a few hours after actual spray application did the DDT concentration in the stream exceed a steady background level of 0.5 ppb. pp 'DDT (<17 ppb.), and this DDT flush occurred mainly as a surface film associated with the formulating oil. Bottom sediments, extracted with hexane-acetone (2/1) for chromatographic analysis, showed a downstream dilution gradient of DDT residue from tributary to estuary, and these averaged only 12.5 per cent of the DDT concentration found in the soils of surrounding forests. Much of the pp' DDT applied in the original technical spray was decomposed to DDE and DDD in the bottom sediments of forest streams.