Use of diffusive gradient in thin-films (DGTs) to advance environmental mercury research: Development, growth, and tomorrow

An understanding of global environmental pollution requires sensitive high-resolution analytical methods to detect contaminants at trace level concentrations (≤ppb), to accurately assess potential effects associated with chronic low-level exposure. Additionally, the focus of environmental risk assessments has evolved to consider not only total concentrations but also bioavailable fractions. Diffusive gradient in thin-film passive samplers (DGTs) can be deployed in a variety of matrices to accumulate contaminants through diffusion. Due to their simple design, DGTs can be manipulated and adjusted to fit the experimental or monitoring purpose and contaminant of interest. Mercury (Hg) is a ubiquitous trace element of global concern that accumulates in biota and concentrates through the food chain as organic methylmercury. Existing reviews on environmental Hg research mention DGTs as a promising and successful tool to quantify the flux of labile species over a broad range of environmental matrices. This is the first comprehensive review of current literature describing the development and environmental deployment of mercury specific DGTs. Given the multi-facetted nature of this research, this review discusses the impact of DGT configuration and Hg speciation on the interpretation of analytical data and addresses the application of DGT passive samplers in bioavailability studies.