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Abstract. A number of recent studies have documented elevated concentrations of mercury (Hg) in fish caught in remote lakes and a pattem of increased concentrations of Hg in fish tissue with decreasing water column pH. Because of the potentiallinkage between fish Hg and surface water acidification, factors regulating water column concentrations and bioavailability of Hg were investigated in Adiroodack lakes through a field study and application of the Mercury Cycling Model (MCM). Concentrations of total Hg and total MeHg were highly variable, with concentrations of total MeHg about 10% of total Hg in lakes which did not show anoxic conditions. In lakes exhibiting anoxic conditions in the hypolimnion during summer stratification, concentrations of total MeHg were elevated. Concentrations of total Hg and total MeHg increased with decreasing pH in remote Adirondack lakes. However, more importantly, concentrations of total Hg and total MeHg increased with increasing concentrations of dissolved organic carbon (DOC) and percent near-shore wetlands in the drainage basin. Mercury concentrations in muscle tissue of yellow perch from Adirondack lakes were elevated above the U.S. FDA action Ievel (1 pg/g Hg) in 7% of the fish sampled or in one or more individual fish from 9 of the 16 lakes sampled. Fi~h Hg concentrations generally increased with increasing fish length, weight and age. Patterns of increasing Hg concentration with age likely reflect shifts in prey of yellow perch and the bioconcentration of Hg along the food chain. For age 3 to 5 perch, concentrations of Hg increased with increasing concentrations of DOC and percent near-shore wetlands in the drainage basin. However, for a Iake with very high DOC concentrations, fish concentrations of Hg declined. Calculations with the MCM also show that concentrations of Hg species increase with increasing DOC due to complexation reactions. Increases in DOC result in increasing concentrations of Hg in biota but decreases in the bioconcentration factor of Hg in fish tissue. This research suggests that DOC is important in the transport of Hg to Iake systems. High concentrations of DOC may complex MeHg, diminishing its bioavailability. At high concentrations of monomeric Al, the complexation of MeHg with DOC apparently decreases, enhancing the bioavailability of MeHg.

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h i g h l i g h t sThe removal efficiencies for CAP in water by PS activated by Fe 2+ and ZVI were studied.CAP was effectively removed by the ZVI-PS system at a broad pH range of 3-10. CAP removal was significantly influenced by operational parameters.The ZVI-PS system shows potential prospects in wastewater or even concentrated wastewater treatment. An oxidation pathway was proposed for CAP removal by the ZVI-PS system. a r t i c l e i n f o , and HA significantly inhibited CAP decomposition. Up to 92.8%, 94.7%, and 75.7% of CAP were removed from the filtrate, permeate, and retentate phases of wastewater, respectively. This result indicated that the ZVI-PS system can significantly remove CAP from wastewater and even concentrated wastewater. The intermediate products during oxidation were identified, and the degradation pathways of CAP were tentatively proposed.