Mercury fluxes from volcanic and geothermal sources: an update

We review the state of knowledge on global volcanogenic Hg emissions to the atmosphere and present new data from seven active volcanoes (Poás, Rincón de la Vieja, Turrialba, Aso, Mutnovsky, Gorely and Etna) and two geothermal fields (Las Pailas and Las Hornillas). The variability of Hg contents (c. 4–125 ng m−3) measured in gaseous emissions reflects the dynamic nature of volcanic plumes, where the abundances of volatiles are determined by the physical nature of degassing and variable air dilution. Based on our dataset and previous work, we propose that an average Hg/SO2 plume mass ratio of c. 7.8×10−6 (±1.5×10−6; 1 SE, n=13) is best representative of open-conduit quiescent degassing. Taking into account the uncertainty in global SO2 emissions, we infer a global volcanic Hg flux from persistent degassing of c. 76±30 t a−1. Our data are derived from active volcanoes during non-eruptive periods and we do not have any direct constraint on the Hg flux during periods of elevated SO2 flux associated with large-scale effusive or explosive eruptions. This suggests that the time-averaged Hg flux from these volcanoes is even larger if the eruptive contribution is considered. Conversely, closed-conduit degassing and geothermal emissions contribute modest amounts of Hg.

The sea-air exchange of mercury (Hg) in the marine boundary layer of the Augusta basin (southern Italy): concentrations and evasion flux

The first attempt to systematically investigate the atmospheric mercury (Hg) in the MBL of the Augusta basin (SE Sicily, Italy) has been undertaken. In the past the basin was the receptor for Hg from an intense industrial activity which contaminated the bottom sediments of the Bay, making this area a potential source of pollution for the surrounding Mediterranean. Three oceanographic cruises have been thus performed in the basin during the winter and summer 2011/2012, where we estimated averaged Hgatm concentrations of about 1.5±0.4 (range 0.9-3.1) and 2.1±0.98 (range 1.1-3.1) ng m(-3) for the two seasons, respectively. These data are somewhat higher than the background Hg atm value measured over the land (range 1.1±0.3 ng m(-3)) at downtown Augusta, while are similar to those detected in other polluted regions elsewhere. Hg evasion fluxes estimated at the sea/air interface over the Bay range from 3.6±0.3 (unpolluted site) to 72±0.1 (polluted site of the basin) ng m(-2) h(-1). By extending these measurements to the entire area of the Augusta basin (~23.5 km(2)), we calculated a total sea-air Hg evasion flux of about 9.7±0.1 g d(-1) (~0.004 tyr(-1)), accounting for ~0.0002% of the global Hg oceanic evasion (2000 tyr(-1)). The new proposed data set offers a unique and original study on the potential outflow of Hg from the sea-air interface at the basin, and it represents an important step for a better comprehension of the processes occurring in the marine biogeochemical cycle of this element.

[RISKOFDERM: European research project for assessment of occupational skin exposure to chemicals]

OBJECTIVES

RISKOFDERM is a research project whose aim is to develop instruments to assess and manage occupational dermal exposure to chemical substances.

METHODS

The research, funded by the European Commission, involves 15 Institutes from 10 member countries; it is a continuation of the Dermal Exposure Network experience and consists of four interrelated parts. The first phase (Qualitative survey) assumed that dermal exposure can be extrapolated from one compound to another when it is task-based: therefore six Dermal Exposure Operation units (DEOu) were defined that lead back to the variety of occupational dermal exposure conditions and an extensive Questionnaire was developed for on-site surveys to perform standard observations in selected working situations (scenarios).

RESULTS

The Italian group, participating in the research, obtained a set of observations relating to two "scenarios" in different working sectors: asphalt, ceramic and pottery workers, spectacle decorators and paint production: the aim was to verify the validity of the methodology in assessing the risk of percutaneous absorption, time, frequency and extension of skin exposure.

CONCLUSIONS

From the observations made it was shown that the perception of risk was poor; it is necessary to rationalise work organization, and train and inform the employees on the correct use of personal protection devices.