Reductive dechlorination rate data for 4,4'-DDE in sediments of the Palos Verdes Shelf, CA (1981-2010)

Dates

Publication Date: 2017-09-27
Start Date: 1981
End Date: 2010

Citation

Eganhouse, R.P., Sherwood, C.R., Pontolillo, James, Edwards, B.D., and Dickhudt, P.J., 2017, Reductive dechlorination rate data for 4,4'-DDE in sediments of the Palos Verdes Shelf, CA (1981-2010): U.S. Geological Survey data release, http://doi.org/10.5066/F7ZC81SV.

Summary

Wastes from the world’s largest manufacturer of DDT were released into the Los Angeles County municipal sewer system from 1947 to 1971. Following primary treatment, the effluent was discharged from a submarine outfall system whereupon a portion of the DDT and associated degradation products were deposited in sediments of the Palos Verdes Shelf (PVS). Parent DDT is present only in trace amounts in the sediments today, the vast majority having been transformed to DDE shortly following deposition. Previously believed to be inert, DDE is slowly being converted to DDMU and DDMU to DDNU via microbially-mediated reductive dechlorination (RDC). Kinetic and compositional data suggest that this process began sometime in the mid- to late 1970s. [...]

Summary

Wastes from the world’s largest manufacturer of DDT were released into the Los Angeles County municipal sewer system from 1947 to 1971. Following primary treatment, the effluent was discharged from a submarine outfall system whereupon a portion of the DDT and associated degradation products were deposited in sediments of the Palos Verdes Shelf (PVS). Parent DDT is present only in trace amounts in the sediments today, the vast majority having been transformed to DDE shortly following deposition. Previously believed to be inert, DDE is slowly being converted to DDMU and DDMU to DDNU via microbially-mediated reductive dechlorination (RDC). Kinetic and compositional data suggest that this process began sometime in the mid- to late 1970s. Rates of DDE RDC in shelf sediments are spatially variable and have proven difficult to determine accurately. This limits our ability to understand the factors controlling RDC rates and to predict the course of natural recovery. In the present study, concentrations of ten DDT compounds and twelve PCB (polychlorinated biphenyl) congeners were determined in cores collected at two locations on the PVS (stations 3C, 6C, ~7 km and ~2 km downcurrent from the outfalls, respectively). DDE inventories, normalized to those of non-degrading PCB congeners having similar physico-chemical properties, were modeled to yield first-order RDC rates for the period 1981-2010. Average rates at the two sites were 0.044 ± 0.004 (3C) and 0.008 ± 0.002 yr-1 (6C), respectively, with depth-dependent RDC rates at station 3C (1992-2003) ranging from 0.0025 to 0.102 yr-1. Comparison of RDC and total loss (i.e., RDC + physical loss) rates suggests that the average per cent loss of DDE due to RDC is ~90% at station 3C (1981-2010) and ~57% at station 6C (1992-2010). Trajectories of adjusted molar inventories of DDE, DDMU, and DDNU were forecast using a first-order multi-step reaction series model. The results for DDE are consistent with the normalization procedure, RDC rates at stations 3C and 6C were 0.036 ± 0.002 yr-1 and 0.010 ± 0.001 yr-1, respectively. At station 6C, the DDE to DDMU transformation appears to be the rate limiting step in the reaction sequence, DDE (k_1 ) ⃗ DDMU (k_2 ) ⃗ DDNU (k_3 ) ⃗ unidentified compound(s), whereas at station 3C RDC rates for DDE and DDMU are roughly equivalent. At both locations the transformation rate of DDNU is 7-20 times that of the other steps. Estimated half-lives of DDE at stations 3C and 6C based on the M-SRS model results are ~19 and 72 years, respectively.

Contacts

Point of Contact :: Robert P Eganhouse
Originator :: Robert P Eganhouse, Christopher R Sherwood, James Pontolillo, Brian D Edwards, Patrick Dickhudt
Metadata Contact :: Robert P Eganhouse
publisher :: U.S. Geological Survey
Distributor :: GS ScienceBase
USGS Mission Area :: Water Resources
SDC Data Owner :: National Research Program

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RDC rates data PV Shelf (1981-2010).xml Original FGDC Metadata	View	100.46 KB	application/fgdc+xml
Data file for RDC rates-FINALx.xlsx		81.53 KB	application/vnd.openxmlformats-officedocument.spreadsheetml.sheet

Purpose

Data were collected in order to calculate reductive dechlorination rates for 4,4'-DDE in sediments of the Palos Verdes Shelf (CA) in support of the U.S. Environmental Protection Agency's Palos Verdes Site Remediation Plan.

Reductive dechlorination rate data for 4,4'-DDE in sediments of the Palos Verdes Shelf, CA (1981-2010)

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