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A novel semiautomatic dissolved elemental mercury analyzer (DEMA) was developed for investigating dissolved elemental Hg (DEM) in natural waters. This on-line setup couples the main analytical steps from sample introduction, gas-liquid separation, and Au amalgamation/separation to final detection/data acquisition using flow injection techniques. This approach provides ease of operation and high analytical performance and is suitable for shipboard use. The analyzer can be fully automated and also be modified to examine other Hg species (e.g., reactive and total Hg and monomethyl-Hg). Here, we present the results of laboratory performance tests and make a comparison with a traditional manual method. DEM measured by both manual and the DEMA show good agreement. Representative field DEM data from spring and summer 1999 in Long Island Sound, U.S.A. (LIS) are presented. Spatial and temporal DEM variations were evident. Rapid and accurate determinations of DEM are necessary to observe its distribution dynamics, evaluate emissions, and assess its role in the aquatic biogeochemical cycling of Hg.

Aqueous production and water-air exchange of elemental mercury (Hg0) are important features of the environmental cycling of Hg. We investigated Hg0 cycling in ten Arctic Alaskan lakes that spanned a wide range in physicochemical characteristics. Dissolved gaseous Hg (DGM, dominated by Hg0) varied from 40 to 430 fM and averaged 200 fM. All surface waters were supersaturated relative to the atmosphere. DGM averaged 3 ± 2% of dissolved (i.e., filter passing) dissolved total mercury (DTM) and 15 ± 6% of dissolved labile Hg (DLM). In-lake DGM profiles generally followed the vertical distribution of light, indicating photoreduction of Hg(II) complexes as a source of Hg0. Additionally, DGM correlated linearly with DLM (r2 = 0.82, p < 0.0001) in the lake surface, signifying that Hg complexes (mostly organic Hg associations) in dissolved phase are photoreducible and contribute to production of DGM. Further, a positive relation between DGM/DTM and both Ka (light attenuation coefficient; r2 = 0.73, p < 0.02) and DOC (r2 = 0.60, p = 0.02) suggests that solar radiation and dissolved organic matter control DGM production and its cycling. An average rate of DGM formation (0.6 ± 0.2% of DTM d−1; range, 0.20.8) was estimated by assuming steady state with the evasional rate. In-lake DGM formation occurs at lower rates in waters with greater suspended particulate matter and dissolved organic carbon (DOC), pointing to the significant role of organic matter plays in controlling DGM formation in these aquatic systems. Estimated evasional fluxes of Hg0 (average, 140 ± 50 pmol m−2 d−1; range, 60–200) were comparable to those of temperate lakes (e.g., Wisconsin, Michigan). In arctic lakes, the rate of evasion during ice-free periods (7 ± 3 nmol m−2 yr−1) is similar to the atmospheric input of Hg (wet + dry) to the lakes based on levels in summertime precipitation but not including additional sources, e.g., springtime depletion. [Copyright &y& Elsevier]

Contaminants in the marine environment are widespread, but ship-based sampling routines are much narrower. We evaluated the utility of seabirds, highly-mobile marine predators, as broad samplers of contaminants throughout three tropical ocean regions. Our aim was to fill a knowledge gap in the distributions of, and processes that contribute to, tropical marine contaminants; and explore how species-specific foraging ecologies could inform or bias our understanding of contaminant distributions. Mercury and persistent organic pollutant (POPs) concentrations were measured in adults of five seabird species from four colonies in the central Pacific (Laysan and Tern Islands, Hawaii; Palmyra Atoll) and the eastern Caribbean (Barbuda). Blood-based total mercury (THg) and 89 POPs were measured in two seabird families: surface-foraging frigatebirds (Fregata spp.) and plunge-diving boobies (Sula spp.). Overall, largescale contaminant differences between colonies were more informative of contaminant distributions than inter-specific foraging ecology. Model selection results indicated that proximity to human populations was the best predictor of THg and POPs. Regional differences in contaminants were distinct: Barbudan Magnificent Frigatebirds had more compounds (n = 52/89 POP detected) and higher concentrations (geometric mean THg = 0.97 μg g−1; mean ΣPOP 53 = 26.6 ng mL−1) than the remote colonies (34–42/89 POP detected; range of THg geometric means = 0.33–0.93 μg g−1; range of mean ΣPOP 53 :7.3–17.0 ng mL−1) and had the most recently-synthesized POPs. Moderate differences in foraging ecologies were somewhat informative of inter-specific differences in contaminant types and concentrations between nearshore and offshore foragers. Across species, contaminant concentrations were higher in frigatebirds (THg = 0.87 μg g−1; ΣPOP 53 = 17.5 ng mL−1) compared to boobies (THg = 0.48 μg g−1; ΣPOP 53 = 9.8). Ocean currents and contaminants' physiochemical properties provided additional insight into the scales of spatial and temporal contaminant exposure. Seabirds are excellent, broad samplers with which we can understand contaminant distributions in the marine environment. This is especially important for tropical remote regions that are under-sampled. Unlabelled Image • Seabirds are excellent samplers of broadscale marine contaminant patterns. • Contaminants and foraging ecology assessed in 5 seabird species in Pacific, Caribbean. • Mercury and persistent organic pollutants (POP) were detected in all samples. • Proximity to human populations was the best predictor of contaminant concentrations. [ABSTRACT FROM AUTHOR]

• Hg is ubiquitous; could act as a foraging ecology tracer in marine predators' diet. • Well-documented adverse effects of Hg could also be an indicator of wildlife health. • Measured foraging ecology via stable isotopes; endocrine effect via prolactin hormone. • Two seabird species had different Hg, isotopes; reflected diverse foraging strategies. • No relationship between Hg, prolactin detected; Hg not indicator of breeding health. Marine predators are frequently exposed to contaminants through diet, and thus contaminants like mercury have the potential to be used as tracers of foraging ecology. Mercury's neurotoxic and endocrine-disrupting effects can have far-ranging consequences for both individuals and populations, and thus mercury concentrations could also be indicative of wildlife health. Because blood samples are relatively non-invasive and easy to obtain in seabird colonies, we investigated whether blood-based mercury concentrations were representative of foraging ecology and breeding hormone concentrations in seabirds. Blood-based mercury carbon and nitrogen stable isotopes, and the reproductive hormone, prolactin, were sampled from two seabird species that exhibit different foraging strategies in Western Australia: Great-winged Petrels (Pterodroma macroptera) are pelagic squid-specialists whose populations are under-studied; Flesh-footed Shearwaters (Ardenna carneipes) are coastal foragers that associate with fishing vessels, and are a species listed as Vulnerable in Western Australia. Mercury was six times higher in Great-winged Petrels (geometric mean ± SE: 3.360 ± 0.180 μg g−1 ww, n = 15) than Flesh-footed Shearwaters (0.554 ± 0.109 μg g−1 ww, n = 12). There was a significant difference in δ 15N between species, and within-species variation in δ 13C mirrored variation in mercury concentrations, supporting the view that foraging ecology plays a central role in mercury exposure. Furthermore, Great-winged Petrels' mercury concentrations are among the highest reported in seabirds. However, no relationship between mercury and prolactin concentrations was detected. Overall, these results demonstrate that mercury can be used as a foraging ecology tracer in these populations but may not be a good indicator of seabirds' breeding hormones like prolactin, though mercury may affect other aspects of reproduction that we did not measure. These results may aid in future assessment of population trends in these, and other, species. [ABSTRACT FROM AUTHOR]

As part of the ISCAT-2000 field study, aerosol particle samples were collected over ∼24 hr intervals at the South Pole (SP), and they were analyzed for trace elements and for selected ions important for Antarctic sulfur and nitrogen chemistry. This paper focuses on lead and mercury while a companion paper in this issue presents the results of the aerosol ion studies. The results showed that most trace metals were below their limits of detection. Two that were not were Pb and Hg. Lead was only quantified in 15 of 53 samples, and based on those data, the mean concentration of Pb would be <0.032 ng m-3. This is substantially lower than the aerosol Pb concentrations reported for the SP in the early to mid-1970s, suggesting that the decrease may be related to controls on pollution emissions; however, contamination of the earlier samples also would explain the difference. The arithmetic mean concentration of filterable Hg was 0.04 ng m-3; thus approaching levels reported for the Arctic. In contrast to the Arctic, however, filterable Hg at the SP was not associated with low ozone mixing ratios; rather the reactions driving the cycling of Hg at the SP appear to involve HOx radicals, reactive nitrogen, and more than likely other substances through complex and not fully understood pathways. [Copyright &y& Elsevier]