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with weekly monitoring from March through October each year (WDOE
2012
). As
with the CA-SWD, the WA-EIM monitoring data were not suitable for trend analy-
sis, but comparisons to the data sets of Martin et al. (
2011
) and CA-SWD (CDPR
2012a
) could be made. From 2002 to 2011, percent detections in the WA-EIM data-
base ranged from 4.9 to 32%, rates similar to those observed by Martin et al. (
2011
)
and CA-SWD (CDPR
2012a
). The 95th centile concentrations ranged from 0.033 to
0.3 μg L
−1
, and maximum concentrations ranged from 0.35 to 0.59 μg L
−1
. In gen-
eral, CPY concentrations in the EIM dataset were greater than those reported by
Martin et al. (
2011
), but less than those reported by CA-SWD (CDPR
2012a
).
Another source of information on concentrations of CPY in surface water used
in this assessment was compiled by the tributary monitoring program operated by
the National Center for Water Quality Research (NCWQR) at Heidelberg University
(NCWQR
2012
). Concentrations of nutrients, sediment, and pesticide were included
in the NCWQR monitoring program database. Concentrations of CPY were reported
for 6,301 samples from ten stations within the Lake Erie Basin and Ohio from 2002
to 2011. CPY was detected in 6 samples (<1%), with concentrations ranging from
0.02 to 0.37 μg L
−1
. The percent of detections was less in the NCWQR dataset than
in the other datasets.
Overall, the database with the greatest number of samples (more than 10,000)
and broadest geographical representation (Martin et al.
2011
) shows that CPY was
detected in 9% of samples analyzed between 2002 and 2010 and that 95% of the
samples contained CYP at less than 0.007 μg L
−1
, and the maximum was 0.33 μg L
−1
.
The regional databases, which were more focused on areas of pesticide use than the
USGS database, had more frequent detections (13-17%) and greater concentrations
(95th centiles 0.010-0.3 μg L
−1
). Even in the WA-EIM database, less than 1% of
samples analyzed since 2007 exceeded 0.1 μg L
−1
.
2.2
Chlorpyrifos in Sediment
The NAWQA (NAWQA
2012
), CA-SWD (CDPR
2012a
), and WA-EIM (WDOE
2012
) databases also contained data on concentrations of CPY in sediments. The
NAWQA database included results of 76 analyses for CPY in sediments between
2007 and 2010 (NAWQA
2012
). CPY was detected in two sediments (detection rate
of 2.6%). One sediment sample had an estimated concentration of 1 μg kg
−1
and the
other had a measured concentration of 58.6 μg kg
−1
. The LOD was 2 μg kg
−1
for all
samples. Data for sediment from the CA-SWD (CDPR
2012a
) were only available
from one study that was conducted in 2004 (Weston et al.
2005
). Of 24 sediments
analyzed, CPY was detected in nine, or a detection rate of 37.5%. Concentrations
ranged from 1.5 to 19 μg kg
−1
and the limit of quantitation (LOQ) was 1 μg kg
−1
for
all samples. The WA-EIM database (WDOE
2012
) had only one detection for CPY
in 23 sediment samples (detection rate of 4.4%) post-2001; the estimated concentra-
tion was 1 μg kg
−1
.
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