| Abstrakt: |
Natural springs provide an opportunistic subject for assessing aquifer contamination. To determine the frequency and level of aquifer contamination by herbicides in the Canadian prairie, a study of natural springs draining small surficial aquifers a few hectares in area was carried out in southern Saskatchewan. All but one of the aquifers investigated received herbicide applications either for agricultural purposes or brush control. Elevated tritium isotope activities (10-60 TU) confirmed recent recharge of these aquifers. No wells were present on these aquifers. Therefore, the possibility of contamination by direct entry down wells was eliminated from the study. Large volume extraction technology permitted defections of herbicides at ng L-1levels. This is the first study of herbicides in natural springs in Canada. Herbicides were detected in 23% of samples collected. The most frequently detected analytes being atrazine (6-chloro-N2-ethyl-N4-(isopr opyl)-1,3,5-triazine-2,4-diamine), picloram (4-amino-3,5,6-trichloropicolinic acid) and 2,4-U ((2,4-dichlorophenoxy)acetic acid), with defections in 12, 7, and 7% of samples collected, respectively. The results show that shallow aquifer contamination occurs in the absence of wells. However, the levels detected were in the ng L-1 (ppt) range, which is much less than levels commonly reported in most well surveys. None of the herbicide concentrations exceeded any guidelines for drinking water, livestock, irrigation, and aquatic life including Canadian, Provincial, World Health Organization, and USEPA guidelines. [ABSTRACT FROM AUTHOR] |
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