Brenda K. Lasorsa

The Methylmercury to Total Mercury Ratio in Selected Marine, Freshwater, and Terrestrial Organisms

Total and methylmercury concentrations were determined in muscle and organ tissue from a wide variety of marine and terrestrial organisms spanning several trophic levels. Sediment and water samples from many of the tissue sampling sites were also analyzed to assess the degree of mercury contamination to which the animals were exposed. The methylmercury to total mercury ratios were examined to determine whether this ratio is indicative of elevated exposure to organic or inorganic mercury and how it varies relative to tissue type and position in the food chain. As an ancillary study, a subset of these tissues was analyzed as 1) wet tissue, and 2) freeze-dried, ball-milled tissue to determine whether the form of sample preparation can adversely affect mercury analysis. Results indicate that the methylmercury to total mercury ratios generally approach unity only in muscle tissue of higher food chain carnivorous fish residing in waters that are relatively uncontaminated with respect to inorganic mercury species. Herbivorous terrestrial mammals and low food chain marine organisms tend to have very low methylmercury to total mercury ratios. Marine animals placed higher on the food chain, such as crabs and lobsters, exhibit somewhat higher methylmercury to total mercury ratios and can exhibit a large variation in this ratio between, organ tissue and muscle tissue of the same animal. The samples analyzed as both wet and freeze-dried, ball-milled tissue indicate that freezedrying and ball-milling in no way result in mercury loss or contamination and, in fact, result in better replicate analyses and create a sample sufficiently stable to be archived for several years without refrigeration.

Heavy metal contamination in the Taimyr Peninsula, Siberian Arctic

The Taimyr Peninsula is directly north of the worlds largest heavy metal smelting complex (Norilsk, Russia). Despite this proximity, there has been little research to examine the extent of contamination of the Taimyr Peninsula. We analyzed heavy metal concentrations in lichen (Cetraria cucullata), moss (Hylocomium splendens), soils, lake sediment, freshwater fish (Salvelinus alpinus, Lota lota and Coregonus spp.) and collared lemming (Dicrostonyx torquatus) from 13 sites between 30 and 300 km from Norilsk. Element concentrations were low in both C. cucullata and H. splendens, although concentrations of Al, Fe, Cu, Ni and Pb were significantly higher than those in Arctic Alaska, probably due to natural differences in the geochemical environments. Inorganic surface soils had significantly higher concentrations of Cd, Zn, Pb and Mg than inorganic soils at depth, although a lake sediment core from the eastern Taimyr Peninsula indicated no recent enrichment by atmospherically transported elements. Tissue concentrations of heavy metals in fish and lemming were not elevated relative to other Arctic sites. Our results show that the impact of the Norilsk smelting complex is primarily localized rather than regional, and does not extend northward beyond 100 km.

A comparison of sample handling and analytical methods for determination of acid volatile sulfides in sediment

Proper sample storage and analytical techniques are required when analyzing anoxic sediment for acid volatile sulfide (AVS), because a change in redox state may alter sediment parameters. The goal of this study was to determine the optimum sample handling, storage, and analytical techniques to adopt when determining AVS concentrations in sediment. To determine the correct handling and storage protocols for use with anoxic sediment, samples of three different AVS levels were manipulated under a combination of the following handling and storage plans: handled on benchtop or under nitrogen atmosphere; preserved with zinc acetate (ZnAc) or not preserved, and stored at 4 °C or frozen (< − 20 °C). The data indicate that sulfide levels are best maintained when samples are handled under a nitrogen atmosphere, stored at 4 °C or frozen, and analyzed within 2 weeks of collection. To determine the best analytical procedure for the determination of AVS in sediment, the following methods were compared: colorimetric, gravimetric, ion-selective electrode, and photoionization detection. The colorimetric method was preferred.

Changes in mercury speciation and the release of methyl mercury as a result of marine sediment dredging activities.

Abstract During the dredging of a moderately contaminated marine waterway (Lavaca Bay, Texas, USA), high concentrations of total mercury (THg, 75–1533 ng/l) and methyl mercury (MHg, 5–70 ng/l) were observed in the decant water from an upland dredge spoils settling basin. By comparison, the water column of the bay contains 7–200 ng/l THg and 0.05–0.8 ng/l MHg. The Hg concentrations observed in the decant water were higher than could be accounted for by the release of sediment pore water, which contained elevated MHg (2–200 ng/l) in the surface 3 cm of the sediments, but diminished exponentially with depth. Laboratory mixing experiments showed that approximately 5% of the sediment bound MHg, and less than 1% of the total mercury was released upon shaking with seawater. Although significant MHg releases could occur from the upper 0–5 cm of the sediments, when integrated over the entire dredged volume, this source is insufficient to account for the levels found in the settling basin decant water. The settling basin became very biologically active, containing algal blooms and releasing hydrogen sulfide to the air, suggesting that increased methylation in the disturbed sediment was responsible for the releases. A laboratory mesocosm study was performed to simulate the findings in the settling pond, but no obvious increase in biological activity occurred, and MHg concentrations increased only to 0.6 ng/l. The implications of these observations may be significant for the local region approximately a dredging site, although crude mass balance considerations show that the MHg flux from this source is trivial compared to bay-wide processes.

Inorganic contaminants in Arctic Alaskan ecosystems: long-range atmospheric transport or local point sources?

The moss monitoring technique (Hylocomium splendens) for tracking environmental concentrations of atmospheric contaminants is applied to arctic Alaska. Median 1990–1992 concentrations of Pb, Cd, Cu, V, and Zn are ≤ median 1990 concentrations in northernmost parts of the Nordic/European monitoring network. Extremely low Pb concentrations (median, 0.6 μg/g) indicate that long-range atmospheric transport (LRTAP) of Pb to arctic Alaskan ecosystems is neglible. However, samples taken adjacent to a local source point (the Dalton Highway) have elevated Pb, V, and Cu. Site-specific watershed studies indicate that natural within- and between-site variability does not affect the interpretation of our Alaskan data relative to the Nordic/European network for Pb, V and Cu. Variability is greater relative to regional data for Cd and Zn, but neither LRTAP nor the Dalton Highway appear to be significant contributors to local concentrations of Cd and Zn. Pilot studies of blueberries and other selected wildlife forage foods indicate that concentrations inH. splendens are generally comparable to those in a common carbou forage lichen, but thatH. splendens may underestimate Cu and overestimate Pb, Hg, and in some cases Cd, relative to selected forage fruits. More studies of contaminants in arctic Alaskan forage foods are needed to characterize potential exposure of human and wildlife populations to airborne contaminants in this region.

The rates of accumulation and chronologies of atmospherically derived pollutants in Arctic Alaska, USA

Abstract Anthropogenically derived pollutants (e.g. trace metals, organochlorines, radionuclides) are deposited upon arctic ecosystems. To determine the range of probable biotic effects of these pollutants, one must know the rate at which they enter and are retained within an ecosystem. However, unknown deposition mechanisms and the complexity of quantifying atmospheric concentrations of constituents of interest make direct measurements of pollutant flux to arctic terrestrial and aquatic ecosystems difficult and/or impractical. Methods of indirectly measuring rates of pollutant accumulation, such as lake sediment stratigraphic analyses, can fill this void. Present in the sediment of two Alaskan lakes sampled in April 1991 were quantifiable concentrations of numerous organochlorine compounds, including DDT and its metabolites (Sum, 0.05-0.60 ng/g), PCBs (Sum, 0.20–30 ng/g), and lindane (0.20-0.80 ng/g). These surface concentrations correspond to estimated deposition rates of 2–6 ng/m2/year ( ∑DDT + metabolites), 10–300 ng/m2/year ( ∑PCBs), and 8–10 ng/m2/year (lindane). The rates and chronologies of accumulation of these pollutants and others are discussed with regard to the process of long-range atmospheric transport.

Mercury methylation at mercury mines in the Humboldt River Basin, Nevada, USA

Total Hg and methylmercury concentrations were measured in mine-waste calcines (retorted ore), sediment, and water samples collected in and around abandoned mercury mines in western Nevada to evaluate Hg methylation at the mines and in the Humboldt River Basin. Mine-waste calcines contain total Hg concentrations as high as 14 000 μg g−1. Stream-sediment samples collected within 1 km of the mercury mines contain total Hg concentrations as high as 170 μg g−1, whereas stream sediments collected at a distance >5 km from the mines, and those collected from the Humboldt River and regional baseline sites, contain total Hg concentrations <0.5 μg g−1. Similarly, methylmercury concentrations in mine-waste calcines are locally as high as 96 ng g−1, but methylmercury contents in stream sediments collected downstream from the mines and from the Humboldt River are lower, ranging from <0.05 to 0.95 ng g−1. Stream-water samples collected downstream from two mines studied contain total Hg concentrations ranging from 6 to 2000 ng l−1, whereas total Hg in Humboldt River water was generally lower, ranging from 2.1 to 9.0 ng l−1. Methylmercury concentrations in the Humboldt River water were the lowest in this study (<0.02–0.27 ng l−1). Although total Hg and methylmercury concentrations are locally high in mine-waste calcines, there is significant dilution of Hg and there is also lower Hg methylation down gradient from the mines, especially in the sediments and water collected from the Humboldt River, which is >8 km from the nearest mercury mines. Our data indicate little transference of Hg and methylmercury from the sediment to the water column due to the lack of mine runoff in this desert climate.

Elevated mercury levels in a wintering population of common eiders (Somateria mollissima) in the northeastern United States

In North America and Europe, sea ducks are important indicators of ecological health and inshore marine pollution. To explore spatial variation in mercury accumulation in common eiders in the northeastern United States, we compared concentrations of total mercury in common eider blood at several New England locations between 1998 and 2013. Eider food items (mollusks) were collected and analyzed to determine if mercury concentrations in eider blood were indicative of local mercury bioavailability. Eiders from Plum Island Sound, MA had a significantly higher mean blood mercury concentration (0.83 μg/g) than those in other locations. Mean mercury levels in this population were also nearly three times higher than any blood mercury concentrations reported for common eiders in published literature. We observed consistent patterns in eider blood mercury and blue mussel mercury concentrations between sites, suggesting a tentative predictive quality between the two species.

Elemental composition and mineralogical characteristics of coastal marine sediments of Tutuila, American Samoa.

Surface sediment samples were collected from 5 pristine coastal areas and 1 potentially contaminated coastal site on Tutuila, the main island of American Samoa, an isolated island group in the South Pacific Ocean. Samples were analysed for total element analysis (15 elements) and mineralogy. The results indicated no evidence of trace element contamination at any site, including Pago Pago Harbour. Inter-site variations could be explained assuming the sediments consisted predominantly of coralline sand and rubble with varying quantities of basaltic materials derived from local catchments.

Mercury concentrations in Pacific lamprey (Entosphenus tridentatus) and sediments in the Columbia River basin

The accumulation of mercury was investigated in Pacific lamprey and stream sediments in the Columbia River basin. Mercury concentrations in larval lamprey differed significantly among sample locations (p < 0.001) and were correlated with concentrations in sediments (r2  = 0.83). Adult concentrations were highly variable (range, 0.1-9.5 μg/g) and unrelated to holding time after collection. The results suggest that Pacific lamprey in the Columbia River basin may be exposed to mercury levels that have adverse ecological effects. Environ Toxicol Chem 2016;35:2571-2576.