Dt. Waite et al., ATMOSPHERIC DEPOSITION OF PESTICIDES IN A SMALL SOUTHERN SASKATCHEWANWATERSHED, Environmental toxicology and chemistry, 14(7), 1995, pp. 1171-1175
Weekly atmospheric deposition samples were collected from early May to
early September during 1984 to 1987 in a small agricultural watershed
near Regina, Saskatchewan, an area in the midst of extensive agricult
ural pesticide use in the Canadian prairies. ''Bulk'' deposition sampl
es were collected weekly in duplicate and analyzed for six herbicides
(bromoxynil, 2,4-D, dicamba, diclofop, triallate, and trifluralin) and
five insecticides (carbaryl, carbofuran, chlorpyrifos, deltamethrin,
and dimethoate). In general, no significant differences were found amo
ng the duplicate samples. Over the 4-year period, the frequency of wee
kly detection of herbicides during the growing seasons was 0, 32, 39,
53, 58, and 67% for trifluralin, bromoxynil, triallate, diclofop, dica
mba, and 2,4-D, respectively. For insecticides, only carbaryl and carb
ofuran were detected in one to two samples in the years for which the
insecticides were analyzed. This infrequent detection reflected the re
latively high detection limits set for the insecticides as compared to
those for the herbicides. The seasonal herbicide atmospheric deposits
during the growing period over the 4-year period (mg ha(-1)) ranged f
rom 90 to 234 (bromoxynil), 386 to 1,374 (2,4-D), 20 to 219 (dicamba),
43 to 338 (diclofop), and 9 to 260 (triallate). Highest deposition ra
tes were measured during and immediately following the spraying period
s, with lesser, but significant, amounts also being detected during th
e harvest operations in August.