DDT residues in forest floor and soil after aerial spraying, Oregon--1965-68
Tarrant, R.F.; Moore, D.G.; Bollen, W.B.; Loper, B.R.
Pesticides Monitoring Journal 6(1): 65-72
1972
ISSN/ISBN: 0031-6156 PMID: 5056441 Document Number: 49746
One month after DDT had been applied from aircraft at the rate of 12 oz/acre to a forest in eastern Oregon, the residues of DDT, its isomers and its metabolites DDD, DDE, and o,p'DDT detected in the forest floor amounted to 3 oz/acre; three years later, this amount had decreased by more than 50% and there was no leaching into the surface mineral soil. At the time of spraying, water from two streams draining the sprayed area had a total DDT content of about 0.3 parts/109. This low concentration decreased rapidly to levels below the limits of analytical detection. No effect of spraying was noted on soil microbial populations, nitrification rate, or the amount of nitrate nitrogen in the soil. Of the 12 oz of DDT applied, about 26% reached the ground immediately, and, during the next 36 months, a further 6% was brought to the ground in litterfall. Thus, about one third of the spray applied reached the forest floor. The need for more efficient methods of application is evident.