1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 4: RISK CHARACTERIZATION
4.1.2.7 Seasonal Ponds
Aquatic Plants
Potential risks to aquatic plants were estimated through comparison to RTVs for terrestrial
plants (Table 4-1). Calculation of HQs indicate that potential risks are primarily as a result of
metals and PAHs. Nickel and selenium exceeded chronic NOECs for aquatic plants with
HQs of 10 and 11, respectively. Chemicals that exceeded chronic LOECs (possible risk –
Category B) included 12 inorganics and 2 organics. HQs ranged from 2.1 for molybdenum
to 160 for arsenic. Of those chemicals exceeding chronic LOECs, 4 were evaluated using an
exposure point concentration that was ½ the reporting limit for a non-detect.
Aquatic Invertebrates
Evaluation of potential toxicity for aquatic invertebrates showed that there was probable
risk (Category A) for 7 inorganic 12 organic chemicals based on exceedance of an acute RTV
(Table 4-3). Nickel and phenanthrene exceeded both the ER-M and LC 50 . For chemicals
exceeding either the ER-M or the LC 50 , all of the HQs were less than 10 with the exception of
phenanthrene which had a LC 50 HQ of 20.
Possible risk (Category B) was observed for 6 inorganic and 10 organic chemicals that
exceeded either the ER-L or the LC 20 . Zinc and chrysene exceeded both the ER-L and LC 20 ,
and the HQs were fairly comparable between the two RTVs. The HQs for comparisons to
the ER-L and LC 20 were all less than 10 with the exception of benzo(b)fluoranthene (11) and
dieldrin (160).
Some possible risk (Category C) was observed for cadmium, pyrene, and high MW PAHs
based on exceedance of a no-effect level, but not a low-effect level. The NOEC HQs for these
chemicals ranged from 4.3 to 32.
Several chemicals had uncertain risk (Category U) because they exceeded the no-effect level,
but did not have a low-effect level. The NOEC HQs for these chemicals ranged from
1.1 (total phthalate esters) to 710 (phenol). The no-effect level was based on the Nereis NOEC
which has some uncertainty because no toxicity was observed in the bioassays. As such, the
HQs for these chemicals may be overestimated.
Seven toxicity bioassays were conducted using the marine amphipod (Eohaustorius estuarius)
with sediment collected from the Seasonal Ponds (Table 3-14). One sample was tested for
Cells 2 and 12, and five samples were tested from Cell 11. The samples from Cells 2 and 12,
as well as two samples from Cell 11, were significantly different from controls for survival.
None was significantly different for reburial.
Four sediment bioaccumulation studies were conducted using the clam worm Nereis viriens.
None of the samples was significantly different from controls for survival, but the samples
were significantly different for 4,4’-DDE and nickel in sediments tested from Cell 11.
Semi-Aquatic Birds
Risk estimates for semi-aquatic birds indicated that metals and pesticides pose the highest
potential for adverse effects (Table 4-2). Terns were the most sensitive receptor for all
chemicals with the exception of arsenic for which the heron was more sensitive. This was
primarily due to the intake from corixids which accounted for over 90% of the total
exposure. Chemicals that showed possible risk (Category B) included arsenic for heron;
ERA REPORT 4-14 SAC/143368(004.DOC)
7/31/02