Bioavailable organochlorine pesticides in a semi-arid region of Eastern Oregon, USA, as determined by gas chromatography with electron-capture detection
Ka. Anderson et E. Johnson, Bioavailable organochlorine pesticides in a semi-arid region of Eastern Oregon, USA, as determined by gas chromatography with electron-capture detection, J AOAC INT, 84(5), 2001, pp. 1371-1382
A group of dissolved-bioavailable organochlorine (OC) pesticides and inorga
nic anions in water and total OC pesticides in sediments were measured in t
he Malheur Watershed, a semi-arid region in the western United States, over
a 2-year period. OC pesticide levels were compared with those from a 1990
study of the lower section of the river, the most recent data available. Af
ter calculating the dissolved fraction from the 1990, study it seems that D
DD and dieldrin levels have decreased in the water by 50-70%, while DDE and
DDT have changed little. Although banned nearly 30 years ago, DDT is still
persistent throughout the Malheur River basin/watershed because it was fou
nd in all water samples tested. All of the OC pesticides tested during the
2-year study are well below the criterion continuous concentration for aqua
tic community exposure as defined by the U.S. Environmental Protection Agen
cy (EPA). OC pesticides appear to be decreasing, however, at lower Ontario
there remains a human health risk (EPA Human Health Risk Water Quality Crit
eria) for DDT, because this criteria includes daily consumption of water an
d fish from the river. Overall, although the upper forest watershed sites h
ave lower OC pesticide concentrations, they represent an important contribu
tion to the total DDT load to this watershed, a source not previously ackno
wledged. The large increase in DDT and Sigma DDT between the Ontario sites
may indicate a possible historical point source of contamination or histori
cal preferential deposition of contamination. Normalized sediment (Sigma DD
T/organic carbon) strongly correlates with dissolved water Sigma DDT.