Abstract
Polychlorinated biphenyl (PCBs) congeners were measured in (unwashed) whole-body field (deer) mice (Peromyscus maniculaltus) collected directly upgradient from a sediment retention structure (weir) within Los Alamos Canyon (LAC), Los Alamos National Laboratory (LANL), New Mexico, USA, from 2007 through 2013. Samples were also collected approximately 8 km downgradient of the retention structure in 2009 and 2013. LAC, a major drainage that crosses LANL lands, contains legacy waste, including PCBs, and occasionally discharges storm water and snowmelt flows to the Rio Grande approximately 8.8 km away from the weir. The Rio Grande is the major waterway that flows southward across the state. The weir was constructed across the channel on the northeastern boundary of LANL in late 2000 to help contain sediments mobilized by floodwaters as a result of a large wildfire in early 2000 that burned forest lands west and adjacent to LANL. Total PCBs in field mice directly upgradient of the sediment retention structure from 2007 through 2012 were significantly greater (p 0.05) than in field mice collected from background locations but decreased in concentration over time; by 2013 the levels were statistically similar (p > 0.05) to background. The highest mean total PCB concentration in field mice was below the levels that may negatively impact field mice population attributes. Total PCBs in field mice collected 8 km below the sediment retention structure in 2009 were lower than field mice collected from behind the weir and decreased over time; also by 2013, the amount of PCBs in field mice 8 km below the sediment retention structure were not significantly different (p > 0.05) from background. The rank order of concentrations of ICES 7 PCB congeners in upgradient and downgradient field mice were: No. 153 > 180 > 138 > 118 > 28 > 101 > 52 and No. 153 > 180 > 138 > 52 > 101 > 118 > 28, respectively. Based on the PCB homolog distribution, the major formulation detected in field mice was Aroclor-1260. Overall, the reduction of PCBs in whole-body field mice from both sites over time was attributed, in part, to sediment control practices.
Highlights
Polychlorinated biphenyls (PCBs) represent one of the most persistent and toxic groups of contaminants in the environment because of their stable properties and ubiquitous distribution [1]
Mean concentrations of Aroclor-1260 were detected in higher concentrations than Aroclor-1254 with the highest amount peaking in 2007; after that, concentrations of both PCB formulations gradually decrease to nondetectable amounts in the latter years
The ecological screening level is the total concentration of Aroclor-1260 in the soil that is not expected to produce any adverse effects on field mice that come into contact with the soil or ingest biota that live in or on the soil
Summary
Polychlorinated biphenyls (PCBs) represent one of the most persistent and toxic groups of contaminants in the environment because of their stable properties and ubiquitous distribution [1] They were manufactured in the United States between 1930 and 1976 [2] and were developed predominantly for use as coolants and lubricants because of their general chemical inertness and heat stability in electrical equipment such as capacitors and transformers [3]. A congener is a specific PCB compound with a certain number of chlorine atoms in certain positions around a biphenyl ring [4] With respect to their behavior in the environment, PCBs are hydrophobic, accumulate in sediment, lipophilic, and bioaccumulate and biomagnify along food chains [1,5,6]
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