Assessing the potential for a novel Composite Integrative Passive Sampler (CIPS) to investigate transboundary movement of organic chemicals in the Tijuana River Estuary

Nearly all environmental monitoring and research of chemical exposure in the aquatic environment relies on grab sampling of water and/or sediment providing only a snapshot in time. Passive sampling of water provides a more representative estimate of exposure compared to grab sampling, but current passive samplers have a limited working range of chemical properties. We tested a novel Composite Integrative Passive Sampler (CIPS) that simultaneously accumulates both hydrophobic and hydrophilic chemicals in water in the Tijuana River Estuary (TRE) on the U.S.-Mexico border. Quantitative targeted analysis detected 169 of the 193 targeted chemicals, and 128 of them were detected in all samples. These included polycyclic aromatic hydrocarbons, current-use and legacy organochlorine pesticides, polychlorinated biphenyls, plasticizers, pharmaceuticals, consumer product chemicals, stimulants, steroid hormones, haloacetic acids, and fecal sterols. The detected chemicals had a range of log K_OW values from 0.2 to 8, by far the largest range ever reported for a passive sampler, and included both legacy chemicals and chemicals of emerging concern. Our findings are in stark contrast to previous work in the TRE, where very few organic pollutants were detected. We conclude the reason for this discrepancy is the ability of the CIPS to preconcentrate a very large range of chemicals in situ during deployment. The highest contaminant concentrations were closest to the U.S.-Mexico border. This work is the first demonstration of a passive sampler that can accumulate such a wide range of chemicals and strong evidence for transboundary movement of chemicals from Tijuana, Mexico to the US.