Characterization and remediation of PCB-contaminated sediments

GGI utilizes geomorphology, dendrochronology, and stratigraphic description of sediment deposits for characterization and remediation of PCB-contaminated sediments at Los Alamos National Laboratory (LANL), New Mexico, USA.

GGI collaborated with Dr. Steven Reneau and Ms. Beckey Coel-Roback of LANL to characterize PCB-contaminated sediments at a site in Los Alamos Canyon, a watershed that drains the Pajarito Plateau and is tributary to the Rio Grande in New Mexico. GGI utilized geomorphic mapping, dendrochronology, and measurement of thickness and stratigraphy of sediment deposits to determine the horizontal and vertical extent of PCB-contaminated sediments. Contaminated sediments were excavated, and GGI conducted confirmatory sampling to verify the removal of PCBs from the site. The chemical analysis and fingerprinting of PCBs at this site can also be used to determine if PCBs have been transported downstream from this site to the Rio Grande (see related Blog “GGI completes Sediment Sampling in Los Alamos Canyon“).

Geomorphic characterization at LA‐SMA‐2, the site with the highest concentrations of PCBs in the Los Alamos Canyon watershed. Tree was buried by 43 cm of sediment after it began growing in 1985. Note bend in tree caused by damage by a flood in ca 1998.

Graph showing distinctive chemical signature of PCB’s at site in Los Alamos Canyon.

Soil samples collected from base of excavation to remove PCB‐contaminated sediment at LA‐SMA‐2, December 2009 (upper Los Alamos Canyon)

If you want to know more about sediment sampling and contaminant transport or want to discuss your geomorphology projects please contact me at drakos@glorietageo.com or at 505 983 5446 Ext. 108.

About GGI:
Founded in 1979 in Santa Fe, NM, GGI has been providing quality professional consulting services in groundwater development, water rights, geomorphology, dairy regulatory compliance, alternative energy and environmental sciences. GGI serves federal, state, and municipal entities, tribal governments, private corporations, and individuals. We pride ourselves in our ability to listen to our clients’ goals and help turn these goals into successes.

For more information please visit our website at www.glorietageo.com

Evaluation of PCBs in the Rio Grande

Utilization of Geomorphology and Analysis of Recent Sediment Deposits for Evaluation of PCBs in the Rio Grande Near Los Alamos National Laboratory, New Mexico.

Glorieta Geoscience, Inc. (GGI) in collaboration with Dr. Steven Reneau at Los Alamos National Laboratory (LANL), has completed the initial phase of a geomorphology investigation evaluating concentrations of Polychlorinated biphenyls (PCBs) in Rio Grande sediments in northern New Mexico. PCBs are a class of organic chemicals that had widespread use in electrical transformers and other industrial applications. Although production of PCBs in the U.S. was stopped in 1977 because of environmental concerns, PCBs are persistent in the environment and present risks to human health and ecosystems in many areas. PCBs have distinctive chemical signatures that can allow for source identification, and this study utilized the “chemical fingerprinting” of PCB’s to evaluate relative PCB contributions from different source areas.

In 2008 and 2009, GGI sampled recent sediment deposits along the Rio Grande upriver and downriver from Los Alamos Canyon and other canyons draining LANL and portions of the Pajarito Plateau to help evaluate sources and concentrations of PCBs in the river. These samples were collected during November-December low-water conditions, and included a range of particle size and geomorphic settings in each sample area (e.g., high-water deposits from snowmelt runoff and slackwater deposits representing late-season flows).

Sediment samples were also collected from four areas within the Los Alamos Canyon watershed, which includes the primary potential LANL sources of PCBs reaching the Rio Grande, to allow comparison with PCB signatures along the river. The sediment samples from the Rio Grande show that the chemical signatures in each area vary between sampled layers, indicating variability in the sources of sediment and associated PCBs in each depositional event.

Data on PCB concentrations in sediment were compared with estimates of sediment flux to estimate average annual PCB flux in the Rio Grande and in lower Los Alamos Canyon. Based on the average PCB concentration and annual suspended sediment flux along the Rio Grande at Otowi Bridge, an estimated PCB flux of 0.16 kg/yr was calculated. In lower Los Alamos Canyon, we utilized the average PCB concentration determined from this investigation, combined with the estimated average suspended sediment flux to calculate a PCB flux of 0.005 kg/yr, or 3% of the total in the Rio Grande. These flux estimates, although preliminary, support the interpretation based on chemical signatures that Los Alamos Canyon is a minor contributor to PCBs in the Rio Grande.

For additional information, see Reneau, S. L., Drakos, P.G., and Schultz-Fellenz, E. S, Use of Congener Homologs to Evaluate PCBs in the Rio Grande Near Los Alamos National Laboratory, New Mexico [Abstract] and [Poster]; See related blog on PCB site investigation and remediation.

If you want to know more about sediment sampling and contaminant transport or want to discuss your geomorphology projects please contact me at drakos@glorietageo.com or at 505 983 5446 Ext. 108.

About GGI:
Founded in 1979 in Santa Fe, NM, GGI has been providing quality professional consulting services in groundwater development, water rights, geomorphology, dairy regulatory compliance, alternative energy and environmental sciences. GGI serves federal, state, and municipal entities, tribal governments, private corporations, and individuals. We pride ourselves in our ability to listen to our clients’ goals and help turn these goals into successes.

For more information please visit our website at www.glorietageo.com