Gaseous Elemental Mercury Levels Research Articles

Long-Range Atmospheric Mercury Transport from Across East Asia to a Suburban Coastal Area in Southern Vietnam.

Exports of atmospheric mercury (Hg) from continental East Asia, a major Hg emitter in the globe, have been reported by several studies in neighboring countries such as Japan and Korea. Nonetheless, studies concerning this topic in Southeast Asia (SEA) countries are still limited. Accordingly, gaseous elemental mercury (GEM) has been measured from Can Thanh High School (CTHS), a suburban coastal site in southern Vietnam to study its characterization and discover the evidence of Hg trans-boundary transport from regional sources (e.g., East Asia). Data collected in July, August, and October 2022 were used in this study, and the overall GEM concentration was 1.61 ± 0.32 ng m-3. The GEM levels were higher in October than in July and August, potentially due to the discrepancy in air mass transport patterns induced by tropical monsoon and source origins of Hg. MERRA-2, backward trajectories, and CALIPSO images revealed the trans-boundary air pollution from continental East Asia to southern Vietnam, evidenced by significantly elevated (> 30%) atmospheric Hg concentrations as well as other air pollutants when the plume arrived at CTHS. Furthermore, our results also imply that atmospheric Hg exported from East Asia could influence large areas in SEA, suggesting the need for more studies in various SEA countries in the upcoming future. This study illustrated the influence of regional Hg emissions on local atmospheric Hg pollution and provided data to improve knowledge of the Hg biogeochemical cycle in SEA.

Declines of gaseous element mercury concentrations at an urban site in eastern China caused by reductions of anthropogenic emission

Long-term observations (June 2014 to June 2022) of atmospheric mercury (Hg) mass concentrations were conducted at an urban site in Nanjing, eastern China, together with other air pollutants. Throughout the sampling period, gaseous elemental mercury (GEM) exhibited a substantial decline from 5.41 ± 1.49 ng m−3 in 2014 to 2.17 ± 1.26 ng m−3 in 2022. The monthly mean concentrations of GEM displayed a significant downward trend, with a rate of 0.36 ng m−3 yr−1 (−7% yr−1). To identify the potential sources contributing to the observed GEM levels, positive matrix factorization (PMF) analysis was employed in conjunction with other relevant pollutants. The results revealed that the natural and anthropogenic emissions played comparable roles in shaping the measured GEM concentrations, with the reduction of coal combustion emissions being the primary driver behind the observed declines at this site. Furthermore, GEOS-Chem simulations suggested a substantial reduction of anthropogenic emissions in eastern China in recent years. This study highlights the decreasing trend of GEM concentrations in eastern China over the past decade, which is attributed to the combined efforts in air pollutant controls, resulting in the synergistic mitigation of Hg from the atmosphere.

Gaseous elemental mercury emissions from informal E-Waste recycling facilities in Pakistan

Detrimental effects of mercury (Hg) on ecosystems and human health have been well-documented. Whereas emissions of gaseous elemental mercury (GEM) from e-waste recycling have been reported in developed countries, much less is known about the situation in the Global South. Using a total of 132 passive air samplers, seasonally resolved concentrations of GEM in air were measured continuously at 32 informal e-waste recycling facilities and background location in Pakistan for a period of one year between September 2020 and December 2021. Annual average GEM concentrations at the studied locations ranged from 1.8 to 92 ng m−3. Among the studied cities, higher concentrations were measured in Karachi (mean ± s.d: 17 ± 22, range: 4.2–92 ng m−3), Lahore (16 ± 4.2, 8.2–22 ng m−3) and Peshawar (15 ± 17, 4.9–80 ng m−3), while lower levels were measured in Hyderabad (6.9 ± 6.2, 3.1–25 ng m−3), consistent with a higher rate of informal recycling activities in metropolitan areas. Seasonally, higher GEM levels occurred during autumn (15 ± 16: 3.3–92 ng m−3) and summer (13 ± 8.7: 1.8–80 ng m−3) than in winter (12 ± 8.4: 2.5–49 ng m−3) and spring (9.2 ± 7.3: 1.8–80 ng m−3), possibly reflecting enhanced volatilization at higher temperatures and/or varying magnitude of recycling operations in different seasons. Policies and strict regulations related to e-waste management should be developed and implemented urgently in the country.

Lichen transplants as indicators of gaseous elemental mercury concentrations

Lichens play an important role in the biogeochemical cycling of mercury (Hg) and are commonly used as indicators of Hg enrichment in remote and anthropogenically impacted environments. To assess their capacity for Hg uptake and accumulation, we determined the concentration of gaseous elemental mercury (GEM) in air and the concentration of total Hg (THg) in transplanted thalli of two lichen species. Lichen transplants and passive air samplers (PASs) were concurrently deployed, side by side, at 10 sites within an abandoned mining area, characterized by large gradients in atmospheric Hg contamination. Highly variable time-weighted GEM concentrations determined by the PASs, ranging from 17 to 4,200 ng/m3, were mirrored by generally high Hg concentrations in transplanted thalli of both Xanthoria parietina (174–8,800 ng/g) and Evernia prunastri (143–5,500 ng/g). Hg concentrations in the two species co-varied linearly indicating about 60% greater Hg accumulation in X. parietina than in E. prunastri. Whereas Hg uptake in the fruticose E. prunastri increased linearly with GEM, a power law equation with a fractional exponent described the uptake in the foliose X. parietina. Extrapolating the relationships observed here to higher GEM levels yielded concentrations in lichen that agree very well with those measured in an earlier fumigation experiment performed under laboratory-controlled conditions. The uptake model of X. parietina was further verified by correctly estimating GEM concentrations from the THg measured in autochthonous thalli collected from the urban area adjacent to the mine site. Passive sampling can effectively provide time-weighted data of suitable spatial resolution to quantitatively describe GEM assimilation by lichens. Therefore, the combined use of passive sampling and lichen transplants can contribute to a more comprehensive understanding of the role of lichens, and potentially also of other cryptogams, in the deposition of atmospheric Hg to terrestrial ecosystems.

First atmospheric mercury measurements at a coastal site in the Apulia region: seasonal variability and source analysis

In the framework of the Italian Special Network for Mercury (ISNM) “Reti Speciali”, a sampling campaign to monitor atmospheric mercury (Hg) was carried out at Monte Sant’Angelo (MSA). This is a coastal monitoring station in the Apulia region, representative of the Southern Adriatic area, within the Mediterranean basin. This work presents continuous Gaseous Elemental Mercury (GEM) measurements over about three years at MSA, using the Lumex RA-915AM mercury analyzer. The aim was to obtain a dataset suitable for the analysis of Hg concentrations in terms of source and transport variation. Diurnal cycles of GEM were evaluated to observe the influence of local atmospheric temperature and wind speed on potential re-emissions from surrounding sea and soil surfaces. Data were also analyzed in terms of long-range transport, using backward trajectory cluster analysis. The spatial distribution of potential sources, contributing to higher measured GEM values, was obtained employing Potential Source Contribution Function (PSCF) statistics. The influence of major Hg anthropogenic point sources, such as mining activities and coal-fuel power plants, both regionally and continentally, from mainland Europe, was observed. The role of the vegetation GEM uptake in modulating the seasonal GEM variability was also investigated. The potential of wildfire influence over the highest detected GEM levels was further examined using active fire data and the evaluation of the vegetation dryness index during the selected episodes.Graphical abstract

Spatial Distribution and Biomonitoring of Atmospheric Mercury Concentrations over a Contaminated Coastal Lagoon (Northern Adriatic, Italy)

The Marano and Grado Lagoon (Northern Adriatic Sea) has been affected by mercury (Hg) contamination coming from two sources, mining activity and discharges from a chlor-alkali plant (CAP). Sediments and water contamination have been previously well characterised, but little is known about the atmospheric compartment, where Hg is easily emitted and can persist for a long time as gaseous elemental mercury (GEM). In this work, atmospheric GEM levels and its spatial distribution over the lagoon were monitored at several sites by means of both continuous discrete instrumental measurements over several months and the determination of Hg bioaccumulated in lichens (Xanthoria parietina L.). Average GEM levels varied from 1.80 ± 0.74 to 3.04 ± 0.66 ng m−3, whereas Hg in lichens ranged between 0.06 to 0.40 mg kg−1. In both cases, the highest values were found downwind of the CAP, but excluding this point, spatial patterns of Hg in the atmosphere and lichens reflected the concentration of this metal in the sediments of the lagoon, showing a decrease moving westward. These results could indicate that the lagoon acts as a secondary source of Hg into the atmosphere: future work is needed to characterise the quantity of releases and depositions at different environments inside the lagoon.

Gaseous Elemental Mercury Concentrations along the Northern Gulf of Mexico Using Passive Air Sampling, with a Comparison to Active Sampling

Mercury is a toxic element that is dispersed globally through the atmosphere. Accurately measuring airborne mercury concentrations aids understanding of the pollutant’s sources, distribution, cycling, and trends. We deployed MerPAS® passive air samplers (PAS) for ~4 weeks during each season, from spring 2019 to winter 2020, to determine gaseous elemental mercury (GEM) levels at six locations along the northern Gulf of Mexico, where the pollutant is of particular concern due to high mercury wet deposition rates and high concentrations in local seafood. The objective was to (1) evaluate spatial and seasonal trends along the Mississippi and Alabama coast, and (2) compare active and passive sampling methods for GEM at Grand Bay National Estuarine Research Reserve, an Atmospheric Mercury Network site. We observed higher GEM levels (p < 0.05) in the winter (1.53 ± 0.03 ng m−3) compared to other seasons at all sites; with the general pattern being: winter > spring > summer ≈ fall. Average GEM levels (all deployment combined) were highest at Bay St. Louis (1.36 ± 0.05 ng m−3), the western-most site nearest the New Orleans metropolitan area, and lowest at Cedar Point (1.07 ± 0.09 ng m−3), a coastal marsh with extensive vegetation that can uptake GEM. The MerPAS units compared reasonably well with the established active monitoring system, but gave slightly lower concentrations, except in the winter when the two methods were statistically similar. Both the passive and active sampling methods showed the same seasonal trends and the difference between them for each season was <15%, acceptable for evaluating larger spatial and temporal trends. Overall, this work demonstrates that PASs can provide insight into GEM levels and the factors affecting them along coastal regions.

Spatial and Temporal Trends of Gaseous Elemental Mercury over a Highly Impacted Coastal Environment (Northern Adriatic, Italy)

Mercury (Hg) is a global pollutant, being highly persistent in the atmosphere, in particular gaseous elemental mercury (GEM), which can easily be emitted and then transported over long distances. In the Gulf of Trieste (northern Adriatic Sea, Italy), contamination by Hg is well characterised but little is known regarding the concentrations, sources and fate of GEM in the atmosphere. In this work, discrete measurements of GEM were recorded from several sites at different times of the year. The database is consistent with temporal night-day variations monitored using a continuous real-time device. The meteorological conditions were collected as ancillary parameters. GEM levels varied from <LOD (2.0 ng m−3) to 48.5 ng m−3 (mean 2.7 ng m−3), with no significant differences found among sites. A clear daily pattern emerged, with maximum values reached just after sunset. Air temperature, relative humidity, wind speed and direction were identified as the main micrometeorological factors influencing both the spatial and temporal variation of GEM. Our results show that average atmospheric GEM values are higher than the natural background of the Northern Hemisphere and will be useful in future selection regarding the most suitable sites to monitor atmospheric Hg depositions and fluxes from soil and water.

Influences of high-level atmospheric gaseous elemental mercury on methylmercury accumulation in maize (Zea mays L.)

Maize (Zea mays L.) leaves play an important role in stomatal uptake and surface adsorption of atmospheric mercury (Hg). However, the influence of atmospheric gaseous elemental mercury (GEM) on methylmercury (MeHg) accumulation in maize plants is poorly understood. In this study, we conducted a field open-top chambers (OTCs) experiment and a soil Hg-enriched experiment to investigate the response of MeHg accumulation in maize tissues to different GEM levels in the air. Maize upper leaves had a higher average MeHg concentration (0.21 ± 0.08 ng g−1) than bottom leaves (0.15 ± 0.05 ng g−1) in the OTCs experiment, which was inconsistent with that in the soil Hg-enriched experiment (maize upper leaves: 0.41 ± 0.07 ng g−1, maize bottom leaves: 0.60 ± 0.05 ng g−1). Additionally, significantly positive correlations were found between MeHg concentrations in maize leaves and air Hg levels, suggesting that elevated air Hg levels enhanced MeHg accumulation in maize leaves, which was possibly attributed to methylation of Hg on leaf surfaces. Mature maize grains from the OTCs experiment had low MeHg concentrations (0.12–0.23 ng g−1), suggesting a low accumulation capability of MeHg by maize grains. Approximately 93–96% of MeHg and 51–73% of total Hg in maize grains were lost from the grain-filling stage to the grain-ripening stage at all GEM level treatments, implying that self-detoxification in maize grains occurred. MeHg concentrations in maize roots showed a significant linear relationship (R2 = 0.98, p < 0.01) with soil Hg levels, confirming that MeHg in maize roots is primarily from soil. This study provides a new finding that elevated air GEM levels could enhance MeHg accumulation in maize leaves, and self-detoxification may occur in maize grains. Further studies are needed to clarify these mechanisms of Hg methylation on maize leaf surfaces and self-detoxification of Hg by maize grains.

Characteristics of mercury speciation in seawater and emission flux of gaseous mercury in the Bohai Sea and Yellow Sea

Four cruises were performed in the Bohai Sea (BS) and Yellow Sea (YS) to ascertain the levels and distributions of gaseous elemental mercury (GEM), dissolved gaseous mercury (DGM), methylmercury (MeHg), and total mercury (THg) during 2012 and 2014. Their concentrations and Hg0 flux exhibited clear spatial-temporal distributions. The GEM level over the BS in spring (2.71 ± 0.49 ng m−3) was significantly higher than that in fall (1.98 ± 0.91 ng m−3). Air masses with elevated GEM mainly originated from northern China. During the two cruises in 2012 over the BS, the mean DGM concentration in spring (35.7 ± 4.6 pg l−1) was comparable to that in fall (32.4 ± 4.6 pg l−1). During the spring cruise of 2014, the mean DGM concentration in the BS (52.8 ± 12.5 pg l−1) was comparable to that in the YS (52.4 ± 14.1 pg l−1), while during the fall cruise of 2014, it was significantly lower in the BS (26.7 ± 14.4 pg l−1) than in the YS (57.2 ± 17.9 pg l−1). DGM represents a small portion of unfiltered THg in the BS (3.95%) and YS (5.12%). The MeHg and MeHg% values were higher in nearshore areas than in open sea, indicating higher productivity in coastal regions. The Hg0 flux in the YS (4.56 ng m−2 h−1) was about twice that in the BS. The annual emission Hg0 fluxes from the BS and YS were 2.71 and 23.68 tons yr−1, respectively.

Can the MerPAS Passive Air Sampler Discriminate Landscape, Seasonal, and Elevation Effects on Atmospheric Mercury? A Feasibility Study in Mississippi, USA

Accurately measuring gaseous elemental mercury (GEM) concentrations in the atmosphere is important to understand its sources, cycling, distribution, and temporal trends. The MerPAS passive air sampler from Tekran Inc. (Toronto, ON, Canada) captures GEM on sulfur-impregnated activated carbon after it passes through a Radeillo diffusive barrier. Because they are small, relatively low in cost, and require no power, they can be deployed at multiple locations, yielding a much greater spatial resolution, albeit at coarser temporal resolution, compared to active sampling. In this study, we used the MerPAS to measure GEM concentration gradients at a mixed hardwood forest, wetland, pond, and a mowed (grass) field, all within close proximity (&lt;500 m) to each other. Vertical profiles (0.5, 3.0, 5.5 m) were assessed during summer and winter. The sorbent was analyzed using a direct mercury analyzer. The samplers were captured between 0.90 to 2.2 ng over 2 weeks, well above the mean blank of 0.14 ng. We observed differences between the landscapes, elevation, and seasons. Nearest to the surface, GEM concentrations were lowest in the wetland (both seasons), where there was dense vegetation, and highest in the mowed field (both seasons). Generally, GEM levels increased with the elevation above the ground, except for the forest where the trend was slightly reversed. This suggests a possible net GEM deposition from the atmosphere to surfaces for three of the four landscapes. GEM concentrations were slightly higher in the winter than the summer at 5.5 m height where air masses were unimpeded by vegetation. Overall, we conclude that the MerPAS is indeed capable of measuring GEM gradients between landscapes, elevations, and seasons, if given sufficient collection time, good analytical precision, and low blank levels.

Ship-Based Measurements of Atmospheric Mercury Concentrations over the Baltic Sea

Mercury is a toxic pollutant emitted from both natural sources and through human activities. A global interest in atmospheric mercury has risen ever since the discovery of the Minamata disease in 1956. Properties of gaseous elemental mercury enable long range transport, which can cause pollution even in pristine environments. Gaseous elemental mercury (GEM) was measured from winter 2016 to spring 2017 over the Baltic Sea. A Tekran 2357A mercury analyser was installed aboard the research and icebreaking vessel Oden for the purpose of continuous measurements of gaseous mercury in ambient air. Measurements were performed during a campaign along the Swedish east coast and in the Bothnian Bay near Lulea during the icebreaking season. Data was evaluated from Gothenburg using plotting software, and back trajectories for air masses were calculated. The GEM average of 1.36 ± 0.054 ng/m3 during winter and 1.29 ± 0.140 ng/m3 during spring was calculated as well as a total average of 1.36 ± 0.16 ng/m3. Back trajectories showed a possible correlation of anthropogenic sources elevating the mercury background level in some areas. There were also indications of depleted air, i.e., air with lower concentrations than average, being transported from the Arctic to northern Sweden, resulting in a drop in GEM levels.

Erratum to: Gaseous Elemental Mercury Level and Distribution in a Heavily Contaminated Site: the Ex-chlor Alkali Plant in Torviscosa (Northern Italy)

Mercury (Hg) poses environmental and health risks due to its global distribution and high toxicity exhibited in some of its chemical forms. Although Hg is naturally present in the environment, human activities have increased its cycling among the land, atmosphere and ocean by a factor of three to five comparing the pre-industrial period to the present day. The Torviscosa chlor-alkali plant (CAP), which operated since the beginning of twentieth century, was one of the most important Cl2 production capacity in the Northern Italy and was responsible for an uncontrolled discharge of Hg in the surrounding area. Previous studies reported the high degree of Hg pollution in soils, river sediments and surface waters of the area, but the Hg level in the atmospheric media was never taken into consideration. In this work, an integrated approach was applied with the aim to assess the level, distribution and dispersion of gaseous elemental mercury (GEM) close to the CAP area. GEM levels were monitored by means of four surveys conducted from September 2014 to July 2015, at fixed locations and covering an area of about 10 km2 (including CAP area, Torviscosa village and reclaimed land), accomplished to Hg bioaccumulation measurements in selected lichens. The results indicate that the CAP area currently represents the main source of GEM in the Friuli Venezia Giulia region. The highest levels were found close to the old factory’s buildings (more than 5000 ng m−3), whereas other sites are less impacted. The emission of GEM is not clearly related to the intensity of solar radiation (temperature) at the soil level; however, this latter influences the release from the old buildings employed in the past for the production activities. The most important factor driving the GEM dispersion is the wind, as confirmed by the map of lichens bioaccumulation. In this context, the GEM plume partially affects the nearby village of Torviscosa (about 1 km), but the values found were always well below the international thresholds for residential areas, thus excluding the risk of inhalation for local inhabitants.

Indoor and outdoor elemental mercury: a comparison of three different cases

Gaseous elemental mercury (GEM) concentrations were determined in three different indoor environments: an office in a building with no indoor sources of mercury (Bldg. I), an office affected by indoor mercury emissions from an adjacent laboratory (Bldg. II), and finally, an office where an outdoor mercury spill occurred accidentally (Bldg. III). The maximum recorded indoor GEM concentrations, with the largest variation in time, were observed in Bldg. II, with a continuous indoor mercury source (lower to upper quartile 15 to 62ngm-3). The lowest values were recorded in Bldg. I (lower to upper quartile 3 to 5ngm-3), where indoor GEM levels were affected mainly by the exhaust of vehicles in the parking lot of the building. The monitoring of GEM indoors (lower to upper quartile 15 to 42ngm-3), and outdoors (in several heights) of the Bldg. III, revealed that the cleaning up procedure that followed the spill was not adequate. Auxiliary measurements in the first two cases were the indoor microclimatic conditions, as well as the indoor CO2 concentrations, and in the third case the outdoor meteorological data. The exhaust of vehicles, the chemical reagents, and an outdoor mercury spill were found to mainly affect the observed indoor GEM levels. People in Bldg. II and people walking through the area, where Hg0 was spilled, were found to be exposed to concentrations above some guide values.

Gaseous Elemental Mercury Level and Distribution in a Heavily Contaminated Site: the Ex-chlor Alkali Plant in Torviscosa (Northern Italy)

Gaseous Elemental Mercury Level and Distribution in a Heavily Contaminated Site: the Ex-chlor Alkali Plant in Torviscosa (Northern Italy)

Time variations of gaseous and reactive mercury in the industrial area of Puertollano (south-central Spain). Temporal cycles with marked variations

Puertollano (48,086 inhabitants) is the largest industrial city in the Castilla-La Mancha region (South-Central Spain). The city is located some 250 km South of Madrid; it was an important coal mining site during the last century and today it is the location of one of the most important Spanish oil refineries and the only refinery located away from the coast. Nowadays the area (which mainly includes the Ojailen valley) has a large open pit coal mine (Encasur), two power plants (Eon and Elcogas) and a petrochemical complex (Repsol) located S and SE from the town. These industries give rise to a complex scenario in terms of mercury emissions to the atmosphere: Repsol, Elcogas and Eon act as discrete sources, while coal mine and dumps acts as a general, diffuse source.The mercury contents in Puertollano town and the related industrial area were characterized during 2010 and 2011 by acquiring stationary data of Gaseous Elemental Mercury (GEM), Reactive Gaseous Mercury (RGM), meteorological parameters and other atmospheric contaminants (NO, NO2, SO2, benzene, toluene, xylene, ozone and PM10). In addition, several Total Gaseous Mercury (TGM) mobile surveys were carried out covering the Ojailen valley.Total Gaseous Mercury (TGM) in the whole valley was in the range 0–24 ng m−3 in all surveys, while higher levels were found near to the coal mine and in the vicinity of a coal power plant that employs clean technology (Elcogas).Tekran data showed low GEM levels during 2010–2011 (1.81 ng m−3 on average), while lower GEM levels were measured during autumn and summer, and maximum levels in spring (7.32 ng m−3 on average). RGM measurements were 0.0088 ng m−3, i.e., significantly lower than background levels in the USA and Europe (0.04 ng m−3). Concentrations of these mercury species' were higher during summer (0.0117 ng m−3).Multiple regression analysis was carried out and good relationships between GEM levels, meteorological parameters and other pollutants were identified. The best GEM predictors were temperature, relative humidity and NO2, whereas the best predictors for RGM were GEM, temperature and ozone. RGM variations seem to be explained predominantly by photoxidation processes, with GEM availability and transport processes of secondary importance.

Air-sea exchange of gaseous mercury in the East China Sea

Two oceanographic cruises were carried out in the East China Sea (ECS) during the summer and fall of 2013. The main objectives of this study are to identify the spatial-temporal distributions of gaseous elemental mercury (GEM) in air and dissolved gaseous mercury (DGM) in surface seawater, and then to estimate the Hg0 flux. The GEM concentration was lower in summer (1.61 ± 0.32 ng m−3) than in fall (2.20 ± 0.58 ng m−3). The back-trajectory analysis revealed that the air masses with high GEM levels during fall largely originated from the land, while the air masses with low GEM levels during summer primarily originated from ocean. The spatial distribution patterns of total Hg (THg), fluorescence, and turbidity were consistent with the pattern of DGM with high levels in the nearshore area and low levels in the open sea. Additionally, the levels of percentage of DGM to THg (%DGM) were higher in the open sea than in the nearshore area, which was consistent with the previous studies. The THg concentration in fall was higher (1.47 ± 0.51 ng l−1) than those of other open oceans. The DGM concentration (60.1 ± 17.6 pg l−1) and Hg0 flux (4.6 ± 3.6 ng m−2 h−1) in summer were higher than those in fall (DGM: 49.6 ± 12.5 pg l−1 and Hg0 flux: 3.6 ± 2.8 ng m−2 h−1). The emission flux of Hg0 from the ECS was estimated to be 27.6 tons yr−1, accounting for ∼0.98% of the global Hg oceanic evasion though the ECS only accounts for ∼0.21% of global ocean area, indicating that the ECS plays an important role in the oceanic Hg cycle.

Passive air sampling of gaseous elemental mercury: a critical review

Abstract. Because gaseous elemental mercury (GEM) is distributed globally through the atmosphere, reliable means of measuring its concentrations in air are important. Passive air samplers (PASs), designed to be cheap, simple to operate, and to work without electricity, could provide an alternative to established active sampling techniques in applications such as (1) long-term monitoring of atmospheric GEM levels in remote regions and in developing countries, (2) atmospheric mercury source identification and characterization through finely resolved spatial mapping, and (3) the recording of personal exposure to GEM. An effective GEM PAS requires a tightly constrained sampling rate, a large and stable uptake capacity, and a sensitive analytical technique. None of the GEM PASs developed to date achieve levels of accuracy and precision sufficient for the reliable determination of background concentrations over extended deployments. This is due to (1) sampling rates that vary due to meteorological factors and manufacturing inconsistencies, and/or (2) an often low, irreproducible and/or unstable uptake capacity of the employed sorbents. While we identify shortcomings of existing GEM PAS, we also reveal potential routes to overcome those difficulties. Activated carbon and nanostructured metal surfaces hold promise as effective sorbents. Sampler designs incorporating diffusive barriers should be able to notably reduce the influence of wind on sampling rates.

Temporal variations in gaseous elemental mercury concentrations at a contaminated site: Main factors affecting nocturnal maxima in daily cycles

Abstract Mercury is considered to be a global pollutant and it has been globally transported as gaseous elemental mercury (GEM). International networks for the continuous monitoring of mercury, all of which are based on background sites, study the dispersion pattern of this metal and trends in its evolution in time and space. However, information about seasonal and daily cycling of polluted sites is scarce. The aim of the work described here was to cover this gap in knowledge. For this purpose, continuous (GEM) measurements were carried out in Almaden town from November 2011 to September 2013. Meteorological data were also collected during this time. GEM data show an average concentration during the sampling period (2011–2013) of 27.4 ng m−3, with a range of 0.8–686.9 ng m−3. The results highlighted seasonal and daily cycles of GEM in Almaden town, with seasonally higher levels in summer (686.9 ng m−3) and significantly daily higher levels during the night. A multiple linear regression model has established wind speed as the best GEM predictor in all seasons during the night, while the best predictor in winter is relative humidity, temperature in spring, solar radiation in summer and wind speed in autumn during the day. These results provide evidence that, in mining polluted sites like Almaden, photochemical reactions have a negligible impact on GEM levels during the daytime and that meteorological parameters are more relevant. Further studies on diurnal GEM cycling in polluted sites must be carried out to obtain a realistic local risk assessment, taking into account night GEM levels and their importance in each case study.

Atmospheric mercury deposition and its contribution of the regional atmospheric transport to mercury pollution at a national forest nature reserve, southwest China.

Atmospheric mercury deposition by wet and dry processes contributes to the transformation of mercury from atmosphere to terrestrial and aquatic systems. Factors influencing the amount of mercury deposited to subtropical forests were identified in this study. Throughfall and open field precipitation samples were collected in 2012 and 2013 using precipitation collectors from forest sites located across Mt. Jinyun in southwest China. Samples were collected approximately every 2 weeks and analyzed for total (THg) and methyl mercury (MeHg). Forest canopy was the primary factor on THg and MeHg deposition. Simultaneously, continuous measurements of atmospheric gaseous elemental mercury (GEM) were carried out from March 2012 to February 2013 at the summit of Mt. Jinyun. Atmospheric GEM concentrations averaged 3.8 ± 1.5 ng m(-3), which was elevated compared with global background values. Sources identification indicated that both regional industrial emissions and long-range transport of Hg from central, northeast, and southwest China were corresponded to the elevated GEM levels. Precipitation deposition fluxes of THg and MeHg in Mt. Jinyun were slightly higher than those reported in Europe and North America, whereas total fluxes of MeHg and THg under forest canopy on Mt. Jiuyun were 3 and 2.9 times of the fluxes of THg in wet deposition in the open. Highly elevated litterfall deposition fluxes suggest that even in remote forest areas of China, deposition of atmospheric Hg(0) via uptake by vegetation leaf may be a major pathway for the deposition of atmospheric Hg. The result illustrates that areas with greater atmospheric pollution can be expected to have greater fluxes of Hg to soils via throughfall and litterfall.