Global Aquatic Passive Sampling (AQUA-GAPS): using passive samplers to monitor POPs in the waters of the world.

The Stockholm Convention (SC) on persistent organic pollutants (POPs) has highlighted the global risk(s) posed by organic contaminants that are persistent, bioaccumulate, are prone to long-range transport, and have the potential to cause adverse effects in humans and wildlife (1). As a result of the SC, monitoring programs are underway to record concentrations of POPs across the globe over time, with atmospheric sampling and human milk as the recommended media (2). The global atmospheric passive sampling (GAPS) program, which utilizes passive air sampling devices at monitoring sites on all continents, mostly in remote regions, has demonstrated the potential for global coverage (3, 4). While data from GAPS addresses the atmospheric compartment and potentially plants and soils exchanging with air, it does not readily address prevailing concentrations or trends in aquatic environments. A major concern with POPs is their biomagnification with top predators that rely on aquatic food webs, including humans, polar bears, seabirds, toothed whales, and seals (2, 5, 6). Often, the consumption of fish, and of marine mammals, is one of the main routes of exposure for humans (7). Hence, being able to sample the presence and longerterm trends of POPs in the water column would provide invaluable information related to long-term (human and aquatic wildlife) exposure. Additionally, monitoring POPs in water would provide vital information on whether reductions in primary emissions of POPs result in reduced concentrations of POPs in receiving waters, and ultimately in global ocean waters and aquatic foodchains. Conversely, as air concentrations of POPs are reduced due to bans and controls on use, oceans could become a major source of POPs to the air-this has been inferred from Arctic and Great Lakes air and water monitoring data (8–10). Deploying passive samplers at these sites coupled with matching air sampling (e.g., (11)) would enable a direct estimation of the direction of air-water exchange fluxes as a response to changing atmospheric concentrations. Concentrations of POPs in receiving surface waters reflect the balance between emissions delivered via rivers and those via atmospheric deposition, rerelease from POPs accumulated in sediments, and volatilization (12). Tracking POPs in water thus provides an important, unique perspective on the effectiveness of reducing emissions and lowering of exposure. Concentrations of POPs in surface water are directly linked to their bioaccumulation in the foodchain (13, 14); hence, knowing dissolved concentrations in the water enables a direct prediction of concentrations in aquatic species using bioaccumulation factors or lipid-water partitioning and food web (trophic) models (15, 16). In several parts of the world, bivalve molluscs are being used as sentinel organisms to reflect on water quality (e.g., “mussel watch”, refs 2, 17–19). Using bivalves for (bio)monitoring has the advantages of directly obtaining data on species consumed by humans, and information on bioaccumulation and bioavailability of POPs under field conditions. However, working with live organisms has several drawbacks that render their global use difficult at best. For example, there is no single species that could be used across the entire world. Purchasing, deploying, and analyzing bivalves is costly and requires trained personnel. Bivalves are generally deployed 1 Editor’s Note: This manuscript was submitted prior to ES&T changing its manuscript parameters for Viewpoints. For the new format, please read the details at http://pubs.acs.org/doi/abs/ 10.1021/es903081n. RA IN ER LO HM AN N /A CS DO I1 0.1 02 1/ ES 80 05 18 G Environ. Sci. Technol. 44, 860–864