Disappearance and persistence of aldrin after five annual applications
Investigation was initiated in 1965 to ascertain the disappearance rate of aldrin applied on loam soils at the recommended level of 1.5 lb per acre from 1960 through 1964. There was no further application of pesticides. Sampling began in 1965 and extended into 1970. Data from gas chromatographic analyses of soil and earthworm samples, collected spring and fall, showed that more than 95 percent of the pesticide had disappeared before the study began. There was no significant (P > 0.05) reduction in aldrin plus dieldrin residues throughout 6 years of study. Similarly, residues in earthworms ( Allolobophora caligimosa ) failed to decline during the 6 years. Average combined residues for 11 semi-annual collection periods was 0.11 ppm in soils, 0.61 ppm in earthworms, wet-weight bases. Results showed that high levels of pesticide did not accumulate and remain in the soil as a result of annual applications and that a large part of applied aldrin had disappeared within 1 year. Earthworms contained 4 to 15 times (average 5.6) as much aldrin plus dieldrin as was found in soils.