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Movement and persistence of 2,4,5‐trichlorophenoxyacetic acid in a forest watershed in the Eastern United States
Author(s) -
Norris Logan A.,
Loper B. R.,
Montgomery M. L.,
Kochenderfer J. N.
Publication year - 1984
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620030404
Subject(s) - throughfall , forest floor , zoology , watershed , litter , precipitation , chemistry , environmental science , hydrology (agriculture) , ecology , biology , soil water , geology , geography , machine learning , computer science , meteorology , geotechnical engineering
Approximately 98% of a 22‐ha forest watershed in West Virginia was treated with 2,4,5‐trichlorophenoxyacetic acid (2,4,5‐T) at a rate of 2.24 kg/ha. The average herbicide residue in the foliage and tips of four species of vegetation was 151 mg/kg immediately after application, 61 mg/kg after 1 week, and 24, 7.9, 4.6, 0.07 and less than 0.01 mg/kg after 1, 3, 6, 12 and 24 months. Residues in the forest floor decreased from 31 mg/m 2 (0.31 kg/ha) immediately after application to 2 mg/m 2 after 12 months and 1.6 mg/m 2 after 24 months. The concentration in 0 to 15 cm soil decreased by 90% in 1 month and then remained relatively constant. No 2,4,5‐T (<0.01 mg/kg) was found deeper than 15 cm after 3 months. Throughfall precipitation transferred 34 mg/m 2 to the forest floor, with 80% occurring the first 2 weeks after application, during which time there was 16.9 cm precipitation. About 6 mg/m 2 was transferred to the forest floor in freshfall litter. The highest concentration of 2,4,5‐T in stream water during application was 0.012 mg/L, and the highest concentration during more than 2 years of measurement was 0.05 mg/L, measured 5 h after beginning application and about 1 h after 0.18 cm precipitation. No 2,4,5‐T was found in stream water more than 13 d after application. A total of 8.4 g (0.017% of the amount applied) 2,4,5‐T was discharged from the watershed in streamflow. The concentrations of 2,4,5‐T in this forest are substantially below those likely to cause any adverse effects in animals.