Environmental Engineering Reference
In-Depth Information
Table 9
Duration of exposures events in the focus watersheds for the 30-yr simulation period
Location of watershed
Georgia
Michigan
California
Event threshold μg L
−1
0.1
1.0
0.1
1.0
0.1
1.0
Duration of events for 28-d half-life
No. of events
0.0
0.0
0.0
0.0
10
4
Min. duration (d)
n/a
n/a
n/a
n/a
1
1
Max. duration (d)
n/a
n/a
n/a
n/a
11
2
Median duration (d)
n/a
n/a
n/a
n/a
1
1.5
Avg. duration (d)
n/a
n/a
n/a
n/a
2.9
1.5
Duration of events for 96-d half-life
No. of events
0.0
0.0
3
0.0
35
10
Min. duration (d)
n/a
n/a
1
n/a
1
1
Max. duration (d)
n/a
n/a
1
n/a
15
6
Median duration (d)
n/a
n/a
1
n/a
1
1
Avg. duration (d)
n/a
n/a
1
n/a
2.3
1.9
96-d half-life simulations. The maximum 96-h TWMCs in sediment were
0.064 μg kg
−1
and 0.067 μg kg
−1
in the 28-d and 96-d half-life simulations, respec-
tively. The Michigan watershed had a maximum 96-h TWMC of 0.028 μg L
−1
and
0.043 μg L
−1
in water for the 28-d and 96-d half-life simulations, respectively.
Maximum 96-h TWMCs in sediment were 0.047 μg kg
−1
and 0.074 μg kg
−1
in the
28-d and 96-d half-life simulations, respectively.
Event duration analysis
. Using RADAR, characterization of durations of exposure
events was conducted on each time series record by using concentration thresholds
of 0.1 and 1.0 μg L
−1
for the three watersheds. In Table
9
, we list each event that met
the respective criteria for the model simulations using both half-life assumptions.
Additional information on each event, including the maximum duration of the event,
average concentration during the event, and the date when the event began are pro-
vided in SI Appendix E.
There were no events exceeding the concentration threshold for the Georgia
watershed over the 30-yr simulation period with either the 28-d or 96-d half-life
values. For the Michigan watershed, no events were predicted with the 28-d
half-life and three events were predicted with the 96-d half-life. All three events
were limited to 1 d. California was predicted to have the greatest number of exceed-
ance events. At a 0.1 μg L
−1
threshold, 10 events were predicted to occur with the
28-d half-life life, while 35 occurred with the 96-d half-life. For the 96-d half-life
and the 0.1 μg L
−1
threshold, the median event duration was 1 d and the longest
duration was 15 d.
4
Discussion
CPY is not detected frequently or at large concentrations in surface waters of
the U.S. Monitoring data reported in the USGS, CDPR, and WDOE databases indi-
cate maximum water CPY concentrations ranging from 0.33 to 3.96 μg L
−1
. These
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