Research Areas > Contaminants > In situ Measurements of Toxic Organic Compounds in Sediment Porewater

Project: In-situ Measurements of Toxic Organic Compounds in Sediment Porewater Using Passive Samplers

Background and Objective

Passive samplers collect and accumulate contaminants of interest from air or water without using external energy sources such as batteries or electricity. Because they are simple and inexpensive to use, passive samplers are becoming increasingly popular for regulatory applications (e.g., for monitoring of chemical constituents in natural or receiving waters). By measuring the bioavailable fraction of metal and organic contaminants, for example, passive sampler measurements are directly related to biological effects. SCCWRP’s contaminant research utilizes passive sampling technology to help quantify the bioavailability of sediment-associated hydrophobic organic contaminants (HOCs), estimate loading and source contributions of regulated organic contaminants in impaired waterways, and document the occurrence and levels of emerging contaminants of concern.

The freely dissolved or “bioavailable” fraction of hydrophobic organic contaminants (HOCs) in sediment pore water is a direct measure of the contaminant pool that can impact biological organisms. However, direct quantification of this fraction with current technology is extremely difficult. Passive sampling technologies that measure freely dissolved HOCs offer clear advantages over traditional ex situ techniques like bulk sediment analysis. Passive sampling technology more accurately reflects the degree of direct HOC exposure for sediment dwelling organisms, improving the relevance of sediment quality assessment and the efficacy of contaminated site remediation. The goal of this study was to develop and test an in situ sediment pore water sampler based on SCCWRP’s solid phase microextraction (SPME) water column sampler.

Status

This study was initiated in 2006 and completed in 2010.

Methods

• A prototype sampler was adapted from a previous water column design. Bench-scale SPME fiber calibration, kinetic and equilibrium experiments for regulated HOCs were carried out.

• SPME samplers and live benthic invertebrates were co-exposed for 28 days in aquaria containing spiked and field collected sediments (Figure 1).

• SPME samplers were deployed in the field for several weeks using simple, rugged fixtures (Figure 2)

Findings

The compact prototype (Figure 1) was capable of Method Detection Limits (MDLs) as low as 0.01 parts per trillion for equilibration times ranging from days to several weeks. Sampler measurements correlated well with tissue concentrations of co-exposed benthic invertebrates in spiked sediment 28-day bioassays and under field conditions, indicating its potential utility as a surrogate measurement for bulk chemistry in sediment quality assessments. The time to equilibrium for precalibrated samplers ranged from 14 to 110 days, with 30 days being a sufficient deployment period for more than half the target HOCs.

Partners

Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Tijuana River National Estuarine Research Reserve, U.S. Environmental Protection Agency, Texas A&M University, Space and Naval Warfare Command

Presentation

K Maruya, D Tsukada, W Lao, E Zeng, D Greenstein, and S Bay. February 2009. A SPME-based sampler for in situ assessment of sediment-associated organic contaminants: comparison with invertebrate body burdens. Presented at Fifth International Conference on Remediation of Contaminated Sediments, Jacksonville, FL.

Poster

K Maruya, W Lao, D Tsukada, D Greenstein, S Bay and E Zeng. November 2008. Correlation between SPME-measured sediment porewater and benthic invertebrate concentrations of hydrophobic organic contaminants (HOCs). Presented at Society of Environmental Toxicology and Chemistry (SETAC) 29th Annual Meeting.