Archives of Environmental Contamination and Toxicology, v.33, no. 4, p. 357-368.
Samples of resident biota and bed sediments were collected in 1992
from 18 sites on or near the floor of the San Joaquin Valley, California,
for analysis of 33 organochlorine compounds. The sites were divided into
five groups on the basis of physiographic region and land use. Ten compounds
were detected in tissue, and 15 compounds were detected in bed sediment.
The most frequently detected compound in both media was p,p' -DDE.
Concentrations of [the sum of]DDT (sum of o,p'- and p,p'
forms of DDD, DDE, and DDT) were statistically different among groups of
sites for both tissue and sediment (Kruskal-Wallis, p<0.05).Concentrations
in both media were highest in streams draining the west side of the valley.
Concentrations of [the sum of]DDT in tissue were significantly correlated
with specific conductance, pH, and total alkalinity (p<0.05), which
are indicators of the proportion of irrigation return flows in stream discharge.
Concentrations in sediment on a dry-weight basis were not correlated with
these water-quality parameters, but total organic carbon (TOC) normalized
concentrations were significantly correlated with specific conductance
and pH (p<0.05). Regressions of the concentration of [the sum of]DDT
in tissue, as a function of [the sum of]DDT in bed sediment, were significant
and explained up to 76% of the variance in the data. The concentration
of [the sum of] DDT in sediment may be related to mechanisms of soil transport
to surface water with bioavailability of compounds related to the concentration
of TOC in sediment. The results of the study did not indicate any clear
advantage to using either bed sediment or tissues in studies of organochlorine
chemicals in the environment. Some guidelines for protection of fish and
wildlife were exceeded. Concentrations of organochlorine chemicals in biota,
and perhaps sediment. have declined from concentrations measured in the
1970s and 1980s, but remain high compared to other regions of the United