Passive Sampling Methods for Assessing the Bioaccumulation of Heavy Metals in Sediments

Heavy metal contamination in sediments has been a great concern around the world due to their potential toxic effects on ecological predators and on human health. Accumulation of heavy metals in benthic organisms is often observed in spite of their low bioavailability in sediments. Direct measurement of bioaccumulation levels using whole organism or tissue samples is probably the most reliable measure for bioaccumulation. However, the whole process of sample preparation and analysis for this is costly and time-consuming and can suffer from experimental artifacts; hence, passive sampling techniques have been successfully used as surrogates for assessing bioaccumulation in sediments. The present work aims to review state-of-the-art passive sampling methods (PSMs) for assessing the bioaccumulation of heavy metals to benthic organisms in sediments. The reviews are divided into four categories: PSMs for biogeochemistry and sediment quality studies, PSMs for bioaccumulation studies, PSMs for bioturbation studies, and PSMs for remediation performance assessment studies. Based on the availability of references on the different PSMs discussed in this paper, the diffusive gradient in thin film (DGT) technique is the most widely used because of its ability to measure the bioavailable fraction of contaminants in sediment. Use of PSMs, coupled with direct measurements from biological samples, can be a robust approach as they can provide a better understanding of the bioaccumulation and the different biogeochemical factors that can affect the uptake of heavy metals by benthic organisms.