OCCURRENCE AND ACCUMULATION OF PESTICIDES AND ORGANIC CONTAMINANTS INRIVER SEDIMENT, WATER AND CLAM TISSUES FROM THE SAN-JOAQUIN RIVER ANDTRIBUTARIES, CALIFORNIA
We. Pereira et al., OCCURRENCE AND ACCUMULATION OF PESTICIDES AND ORGANIC CONTAMINANTS INRIVER SEDIMENT, WATER AND CLAM TISSUES FROM THE SAN-JOAQUIN RIVER ANDTRIBUTARIES, CALIFORNIA, Environmental toxicology and chemistry, 15(2), 1996, pp. 172-180
A study was conducted in 1992 to assess the effects of anthropogenic a
ctivities and land use on the water quality of the San Joaquin River a
nd its major tributaries. This study focused on pesticides and organic
contaminants, looking at distributions of contaminants in water, bed
and suspended sediment, and the bivalve Corbicula fluminea. Results in
dicated that this river system is affected by agricultural practices a
nd urban runoff. Sediments from Dry Creek contained elevated concentra
tions of polycyclic aromatic hydrocarbons (PAHs), possibly derived fro
m urban runoff from the city of Modesto; suspended sediments contained
elevated amounts of chlordane. Trace levels of triazine herbicides at
razine and simazine were present in water at most sites. Sediments, wa
ter, and bivalves from Orestimba Creek, a westside tributary draining
agricultural areas, contained the greatest levels of DDT (1,1,1-trichl
oro-2,2-bis[p-chlorophenyl]ethane) and its degradates DDD (1,1-dichlor
o-2,2-bis[p-chlorophenyl]ethylene) and DDE(1, 1-dichloro-2,2-bis[p-chl
orophenyl]ethyle). Sediment adsorption coefficients (K-alpha, and bioc
oncentration factors (BCF) in Corbicula of DDT, DDD, and DDE at Oresti
mba Creek were greater than predicted values. Streams of the western S
an Joaquin Valley can potentially transport significant amounts of chl
orinated pesticides to the San Joaquin River, the delta, and San Franc
isco Bay. Organochlorine compounds accumulate in bivalves and sediment
and may pose a problem to other biotic species in this watershed.