My research goals for Los Angeles and southern California water quality included evaluating the capture, treatment, and reuse of stormwater through groundwater infiltration; assessing the costs of stormwater quality control; monitoring virus numbers in stormwater; and developing improved methods for measuring pollutant concentrations.
The cost benefit analysis indicated that the treatment of larger regions as one watershed reduces the initial cost to employ the stormwater best management practices, that willingness to pay and value of ecological improvements vary and are difficult to quantify. The new cost estimated for both structural and non-structural BMPs was $12.6 billion, and the total benefit of the BMPs and improvement to the environment was $21.3 billion, for a net benefit of $8.7 billion.
The virus study was less conclusive, finding rather uniform virus counts in the tens of millions per milliliter. Previous research found human viruses in significantly smaller concentrations (1-100 per mL), suggesting that the total counts may reflect high background concentrations of non-human viruses from sources that are not coincident with sources of pollution.
Using two passive samplers, polyethylene devices (PEDs) and solid phase microextraction (SPME) fibers, hydrophobic organic contaminants (HOCs) were quantified and the samplers were compared. PEDs were calibrated for 16 model HOCs (PCBs, PAHs, DDTs, and chlordanes) for both partitioning coefficients (KPEW) and exchange rate kinetics (k e). Triplicate PEDs and SPME fibers were exposed for 45 days to a concentration series of water spiked with nine model hydrophobic organic compounds. Model HOCs in SPME were higher than those in PEDs, with SPME measurements matching water concentrations more closely than PEDs for PCBs and chlorinated pesticides. For PAHs, PED and SPME measurements bracketed LLE water concentrations with no apparent bias. The number of detections using PEDs was greater for concentrations less than 0.1 ng/L, indicating that PEDs afford greater sensitivity than single SPME fibers. Researchers are continuing to investigate PEDs, including the use of pre-loaded reference compounds to quantify the "extent" of equilibrium vs. exposure time and possible variations due to polyethylene manufacturer and process.
|Commitee:||Henry, Ronald, Wilson, John|
|School:||University of Southern California|
|School Location:||United States -- California|
|Source:||DAI-B 70/08, Dissertation Abstracts International|
|Keywords:||Los Angeles, Organic contaminants, Passive samplers, Stormwater, TMDL|
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