EPA Research Partner Support Story: Arsenic bioavailability in contaminated creek sediment

Partner: Florida Department of Environmental Protection, City of Jacksonville
Challenge: Assess the fraction of arsenic that is bioavailable in contaminated creek sediment
Resource: Validation of EPA method to assess arsenic bioavailability in aquatic environments and investigation of bacterial communities in sediment as potential indicators of bioaccessibility
Project Period: 2018 ‒ 2020

Heavy metal contamination of soils is a pervasive problem that is a source of significant human health and ecological risk. Bioaccessibility describes the portion of a heavy metal in contaminated media (soil/sediment, water, air) available to be taken up by the ecosystem. It is an important consideration when assessing ecological risk of contaminated sites. Methods to measure the bioaccessibility of arsenic (As), which was widely used in the past as a wood preservative, do not take into account aquatic sediments. This research was undertaken to determine 1) if EPA Method 1340, an in vitro bioaccessibility assay (IVBA) developed for lead (Pb) and arsenic (As) in soils, can be used to assess As in creek sediments and 2) if there is a relationship between bioaccessible As and sediment bacterial communities that would be useful for risk assessments.

“The Fairfax St. Wood Treaters Superfund Site is a great example of partners working together successfully. It was a collaborative effort in all aspects of the cleanup, including review of the sediment sampling data for Moncrief Creek.”
– Florida DEP Project Manager Miranda McClure

EPA ORD, in collaboration with EPA Region 4 (Southeast), collected As-contaminated sediments from the on-site retention pond and along a creek near the Fairfax Street Wood Treaters facility, which had become a Superfund site. Elevated levels of As in the pond and creek were detected. Once detected, the pond and creek sediments were subjected to the IVBA, a Hyalella azteca sediment toxicity test, and analysis of bacterial community composition using molecular biological and statistical methods.  

Total As ranged from 2 – 52 ppm, with 29 – 95% being bioaccessible. Arsenic bioaccessibility appeared inversely related to total As concentration. There was no statistically significant difference in percent bioaccessible As whether the sediments were dried, as prescribed for the soil IVBA, or left wet—suggesting the soil IVBA Method 1340 is suitable for sediment analyses. The results showed that an IVBA for As in sediments and bacterial community analyses could both be developed for ecological risk assessments. The results from sampling Moncrief Creek helped also helped to show As in the sediments did not pose an ecological risk.