Long-Distance Transport of 2,4-D

Ambient 2,4-D herbicide concentrations in south-central Washington's grape growing areas can reach damaging levels due to aerial 2,4-D applications to wheat fields tens of miles removed from the affected areas. An atmospheric 2,4-D sampling study was conducted by WSU during the spring months of 1973 and 1974. Eight 2,4-D sampler sites were operated on a more or less continuous basis from April through mid-June. Meteorological conditions accompanying day-to-day concentration patterns were analyzed. Results showed that weak frontal systems characterized by mid-level cloudiness and light prefrontal southerly surface winds accompanied higher concentration periods. Conversely, lower concentration periods were accompanied by quasi-stationary high-pressure systems or weak thermally induced low-pressure system.