| Popis: |
DDT translocation in the environment by resuspension and volatilization processes was measured after the spraying of a Pacific Northwest forest with DDT to control a tussock moth infestation. The objective of this study was to determine a resuspension rate from a forested area by sampling airborne DDT. Airborne DDT was sampled by a Cessna 411 aircraft-mounted, high-volume sampler on tour consecutive days. The aircraft sample collector consisted of a Gelman type A glass-fiber filter for DDT particulate and a back-up filter consisting of cylindrical polyurethane foam for DDT vapor. Sample flow rates varied between 2 and 3 m3 min−1. Air samples contained significant amounts of p,p'-DDT, o,p'-DDT, and p,p'-DDE except for background samples taken upwind of the spray areas, and some of the high altitude samples. Maximum total DDT concentration observed was 19 ng m−3 which was collected about 2 h after spray operation at about 150 m above the trees. Concentrations were 2 ng m−3 or less after 26 h. Particulate DDT concentrations were generally larger than vapor DDT concentrations. Valley-slope winds, convection and convective turbulence were predominant mechanisms for DDT translocation. Resuspension rates for DDT were from 10−7 to 10−8 fraction resuspended per second. Airborne DDT levels had decreased to background levels within 86 days after spraying. |
