Total Gaseous Mercury Research Articles

Long-term monitoring of trace metals in PM10 and total gaseous mercury in the atmosphere of Porto, Portugal

As part of a monitoring programme conducted by the Institute of Environment and Development (IDAD) and supported by the regional municipal solid waste (MSW) management authorities, an extensive database of trace metals (TMs) concentrations in ambient air was collected in two sites, Leça do Balio (LB) and Vila Nova da Telha (VNT), located in Porto's metropolitan area, north of Portugal. Since 2004, concentrations of As, Cd, Pb, Cu, Cr, Mn, Hg, Ni and Zn were measured in PM10. In addition, total gaseous mercury (TGM) was monitored since 2008. These measurements were used to assess long-term trends of concentrations. Statistical analysis was used to search for the possible origin of the TMs.During the monitoring period, the mean TMs concentrations followed the order: Zn > Cu > Pb > Mn > Cr > Ni > As ≈ Hg > Cd, and have not exceeded the current air quality guidelines values. Concentrations of As, Cd, Pb, Mn, and Hg have slightly decreased during the measurement period despite already being at historically low levels. The concentrations range of Zn, Cd, Pb and As suggests a seasonal variability for these elements in ambient air, for both sites. Average TGM levels were 1.93 and 1.35 ng m−3, for LB and VNT respectively. In terms of seasonality, a statistical difference was found in TGM concentrations between winter and summer for LB. A daily pattern was also observed in TGM with minimum concentrations during the night and early morning.

Monsoon-facilitated characteristics and transport of atmospheric mercury at a high-altitude background site in southwestern China

Abstract. To better understand the influence of monsoonal climate and transport of atmospheric mercury (Hg) in southwestern China, measurements of total gaseous mercury (TGM, defined as the sum of gaseous elemental mercury, GEM, and gaseous oxidized mercury, GOM), particulate bound mercury (PBM) and GOM were carried out at Ailaoshan Station (ALS, 2450 m a.s.l.) in southwestern China from May 2011 to May 2012. The mean concentrations (± SD) for TGM, GOM and PBM were 2.09 ± 0.63, 2.2 ± 2.3 and 31.3 ± 28.4 pg m−3, respectively. TGM showed a monsoonal distribution pattern with relatively higher concentrations (2.22 ± 0.58 ng m−3, p = 0.021) during the Indian summer monsoon (ISM, from May to September) and the east Asia summer monsoon (EASM, from May to September) periods than that (1.99 ± 0.66 ng m−3) in the non-ISM period. Similarly, GOM and PBM concentrations were higher during the ISM period than during the non-ISM period. This study suggests that the ISM and the EASM have a strong impact on long-range and transboundary transport of Hg between southwestern China and south and southeast Asia. Several high TGM events were accompanied by the occurrence of northern wind during the ISM period, indicating anthropogenic Hg emissions from inland China could rapidly increase TGM levels at ALS due to strengthening of the EASM. Most of the TGM and PBM events occurred at ALS during the non-ISM period. Meanwhile, high CO concentrations were also observed at ALS, indicating that a strong south tributary of westerlies could have transported Hg from south and southeast Asia to southwestern China during the non-ISM period. The biomass burning in southeast Asia and anthropogenic Hg emissions from south Asia are thought to be the source of atmospheric Hg in remote areas of southwestern China during the non-ISM period.

Current understanding of the driving mechanisms for spatiotemporal variations of atmospheric speciated mercury: a review

Abstract. Atmospheric mercury (Hg) is a global pollutant and thought to be the main source of mercury in oceanic and remote terrestrial systems, where it becomes methylated and bioavailable; hence, atmospheric mercury pollution has global consequences for both human and ecosystem health. Understanding of spatial and temporal variations of atmospheric speciated mercury can advance our knowledge of mercury cycling in various environments. This review summarized spatiotemporal variations of total gaseous mercury or gaseous elemental mercury (TGM/GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM) in various environments including oceans, continents, high elevation, the free troposphere, and low to high latitudes. In the marine boundary layer (MBL), the oxidation of GEM was generally thought to drive the diurnal and seasonal variations of TGM/GEM and GOM in most oceanic regions, leading to lower GEM and higher GOM from noon to afternoon and higher GEM during winter and higher GOM during spring–summer. At continental sites, the driving mechanisms of TGM/GEM diurnal patterns included surface and local emissions, boundary layer dynamics, GEM oxidation, and for high-elevation sites mountain–valley winds, while oxidation of GEM and entrainment of free tropospheric air appeared to control the diurnal patterns of GOM. No pronounced diurnal variation was found for Tekran measured PBM at MBL and continental sites. Seasonal variations in TGM/GEM at continental sites were attributed to increased winter combustion and summertime surface emissions, and monsoons in Asia, while those in GOM were controlled by GEM oxidation, free tropospheric transport, anthropogenic emissions, and wet deposition. Increased PBM at continental sites during winter was primarily due to local/regional coal and wood combustion emissions. Long-term TGM measurements from the MBL and continental sites indicated an overall declining trend. Limited measurements suggested TGM/GEM increasing from the Southern Hemisphere (SH) to the Northern Hemisphere (NH) due largely to the vast majority of mercury emissions in the NH, and the latitudinal gradient was insignificant in summer probably as a result of stronger meridional mixing. Aircraft measurements showed no significant vertical variation in GEM over the field campaign regions; however, depletion of GEM was observed in stratospherically influenced air masses. In examining the remaining questions and issues, recommendations for future research needs were provided, and among them is the most imminent need for GOM speciation measurements and fundamental understanding of multiphase redox kinetics.

Total Gaseous Mercury and Mercury Emission from Natural Surface at One Typical Agricultural Region in Three Gorges Reservoir

In situ measurement of total gaseous mercury (TGM) and mercury exchange fluxes between soil with different utilization patterns and atmosphere was conducted at one typical agricultural region in Three Gorges Reservoir. The TGM concentration ranged from 2.67 to 75.5 ng·m-3 with the average of (6.26±8.11) ng·m-3, higher than the global background value. An obvious seasonal variation of TGM was observed, and the TGM values in spring and winter were significantly higher than those in summer and autumn. It was found that the mercury fluxes varied from different landscapes with the emission fluxes at three land use types following the trend:rainfed cropland >paddy field >forest land. Seasonal variations of mercury emission were obvious with highest fluxes in summer and lowest in winter, while the highest daily mercury emission fluxes appeared at midday. Mercury emission fluxes in our study region were mainly controlled by air and soil temperature, humidity, light and ultraviolet, and the air temperature and ultraviolet were regarded as the main factors. The influence of Hg level in soil on Hg emission was not obvious in the presence of environmental factors and agricultural activity.

Temporal variability of atmospheric Total Gaseous Mercury and its correlation with meteorological parameters at a high-altitude station of the South India

Diurnal and seasonal variation of atmospheric Total Gaseous Mercury (TGM) were studied for the first time in a high altitude station, Kodaikanal, India. To achieve this, an automated continuous mercury vapour analyzer was used in the study area between November, 2012 and September, 2013. In this pilot study the annual mean atmospheric TGM concentration was found to be 1.53 ng/m3, with a range from 0.83 to 3.25 ng/m3 and with a lognormal frequency distribution pattern. The mean seasonal concentration of TGM was found to be in the following order: summer > winter > northeast monsoon > southwest monsoon. Significant temporal differences in the TGM concentrations indicated strong environmental control regulated by seasonal changes in this high altitude rural area. The study further revealed that the day time TGM concentration was strongly modified by solar radiation, evaporation and rainfall. Moreover, this is the first study in the Indian subcontinent with continuous monitoring of the temporal changes of TGM and its relation to other micrometeorological factors.

Mercury flux over West Antarctic Seas during winter, spring and summer

For the first time elemental mercury in air and surface seawater was measured continuously in the remote seas of western Antarctica. A major contributor to atmospheric emissions of the toxic and globally dispersed pollutant mercury is the re-evasion from water surfaces, due to a supersaturation of dissolved gaseous mercury (DGM) in surface water. In this study the degree of saturation and mercury flux at the air-sea surface interface have been estimated from continuous measurements of gaseous elemental mercury (GEM) or total gaseous mercury (TGM) in air, DGM in surface water and meteorological parameters. The measurements were performed during winter and spring (2013) in the Weddell Sea and during summer (2010/2011) in the Bellingshausen, Amundsen and Ross Seas, and show spatial and seasonal variations. The average DGM concentration in surface water in open sea was highest during spring (12 +/- 7pg L-1) and lowest during summer (7 +/- 6.8 pg L-1), resulting in a net evasion of mercury during spring (1.1 +/- 1.6 ng m(-2)h(-1)) and a net deposition during summer (-0.2 +/- 1.3 ng m(-2)h(-1)). In open sea, higher average concentrations of GEM (or TGM) and DGM were found close to the Drake Passage compared to in the Bellingshausen and Weddell Seas. Emission sources from the South American continent, identified with back trajectories, were suggested to explain the observed variations. The yearly mercury evasion from open sea surfaces in the Southern Ocean was estimated to 30 ( -450-1700) tons, using the average (and min and max) flux rates obtained in this study. Higher DGM was measured under sea ice (19-62 pg L-1 compared to in open sea due to a capsuling effect, resulting in a theoretical prevented evasion of 520 (0-3400) tons per year. Diminishing sea ice and higher water temperatures in polar regions could result in increased mercury evasion to the atmosphere. However, the contribution of the Southern Ocean to the global modeled annual emissions of mercury from sea surfaces would probably only be a few percent.

Isotopic Composition of Atmospheric Mercury in China: New Evidence for Sources and Transformation Processes in Air and in Vegetation.

The isotopic composition of atmospheric total gaseous mercury (TGM) and particle-bound mercury (PBM) and mercury (Hg) in litterfall samples have been determined at urban/industrialized and rural sites distributed over mainland China for identifying Hg sources and transformation processes. TGM and PBM near anthropogenic emission sources display negative δ(202)Hg and near-zero Δ(199)Hg in contrast to relatively positive δ(202)Hg and negative Δ(199)Hg observed in remote regions, suggesting that different sources and atmospheric processes force the mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) in the air samples. Both MDF and MIF occur during the uptake of atmospheric Hg by plants, resulting in negative δ(202)Hg and Δ(199)Hg observed in litter-bound Hg. The linear regression resulting from the scatter plot relating the δ(202)Hg to Δ(199)Hg data in the TGM samples indicates distinct anthropogenic or natural influences at the three study sites. A similar trend was also observed for Hg accumulated in broadleaved deciduous forest foliage grown in areas influenced by anthropogenic emissions. The relatively negative MIF in litter-bound Hg compared to TGM is likely a result of the photochemical reactions of Hg(2+) in foliage. This study demonstrates the diagnostic stable Hg isotopic composition characteristics for separating atmospheric Hg of different source origins in China and provides the isotopic fractionation clues for the study of Hg bioaccumulation.

Characteristics of total gaseous mercury (TGM) concentrations in an industrial complex in South Korea: impacts from local sources

Abstract. Total gaseous mercury (TGM) concentrations were measured every 5 min in Pohang, Gyeongsangbuk-do, Korea, during summer (17–23 August 2012), fall (9–17 October 2012), winter (22–29 January 2013), and spring (26 March–3 April 2013) to (1) characterize the hourly and seasonal variations of atmospheric TGM concentrations; (2) identify the relationships between TGM and co-pollutants; and (3) identify likely source directions and locations of TGM using the conditional probability function (CPF), conditional bivariate probability function (CBPF) and total potential source contribution function (TPSCF). The TGM concentration was statistically significantly highest in fall (6.7 ± 6.4 ng m−3), followed by spring (4.8 ± 4.0 ng m−3), winter (4.5 ± 3.2 ng m−3) and summer (3.8 ± 3.9 ng m−3). There was a weak but statistically significant negative correlation between the TGM concentration and ambient air temperature (r = −0.08, p<0.05). Although the daytime temperature (14.7 ± 10.0 °C) was statistically significantly higher than that in the nighttime (13.0 ± 9.8 °C) (p<0.05), the daytime TGM concentration (5.3 ± 4.7 ng m−3) was statistically significantly higher than that in the nighttime (4.7 ± 4.7 ng m−3) (p<0.01), possibly due to local emissions related to industrial activities and activation of local surface emission sources. The observed ΔTGM ∕ ΔCO was significantly lower than that of Asian long-range transport, but similar to that of local sources in Korea and in US industrial events, suggesting that local sources are more important than those of long-range transport. CPF, CBPF and TPSCF indicated that the main sources of TGM were iron and manufacturing facilities, the hazardous waste incinerators and the coastal areas.

Total gaseous mercury along a transect from coastal to central Antarctic: Spatial and diurnal variations

Total gaseous mercury (TGM) in the atmospheric boundary layer was investigated along a transect from coastal (Zhongshan Station; 69°22′25″S, 76°22′14″E) to central (Kunlun Station; 80°25′2″S, 77°6′47″E) Antarctic from December 16, 2012 to February 6, 2013. TGM varied considerably from 0.32 to 2.34ngm−3 with a mean value of 0.91ngm−3. Spatially, relatively high values occurred near the coastal region and on the central plateau with altitude higher than 3000m above sea level. This distribution pattern cannot be accounted for simply by the influence of mercury emission from the ocean. Changes in TGM were also found to be related to the topography. TGM was higher in the inland flat region (290–800km from the coast) than in the inland transition zones with steep slopes (800–1000km from the coast). Temporally, diurnal cycling of TGM was clearly observed at Kunlun Station, with the lowest value occurring typically at midnight, and the peak value at midday. This diurnal pattern was attributed to the reemission of gaseous elemental mercury (GEM) from the snow pack, the oxidization of GEM and convective mixing.

Global Mercury Observatory System (GMOS): measurements of atmospheric mercury in Celestun, Yucatan, Mexico during 2012

Within the Global Mercury Observation System (GMOS) project, long-term continuous measurements of total gaseous mercury (TGM) were carried out by a monitoring station located at Celestun, Yucatan, Mexico, a coastal site along the Gulf of Mexico. The measurements covered the period from January 28th to October 17th, 2012. TGM data, at the Celestun site, were obtained using a high-resolution mercury vapor analyzer. TGM data show values from 0.50 to 2.82ng/m(3) with an annual average concentration of 1.047 ± 0.271ng/m(3). Multivariate analyses of TGM and meteorological variables suggest that TGM is correlated with the vertical air mass distribution in the atmosphere, which is influenced by diurnal variations in temperature and relative humidity. Diurnal variation is characterized by higher nighttime mercury concentrations, which might be influenced by convection currents between sea and land. The back trajectory analysis confirmed that local sources do not significantly influence TGM variations. This study shows that TGM monitoring at the Celestun site fulfills GMOS goals for a background site.

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.

Tropospheric mercury vertical profiles between 500 and 10 000 m in central Europe

Abstract. The knowledge of the vertical distribution of atmospheric mercury (Hg) plays an important role in determining the transport and cycling of mercury. However, measurements of the vertical distribution are rare, because airborne measurements are expensive and labour intensive. Consequently, only a few vertical Hg profile measurements have been reported since the 1970s. Besides the Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container (CARIBIC) observations, the latest vertical profile over Europe was measured in 1996. Within the Global Mercury Observation System (GMOS) project, four vertical profiles were taken on board research aircraft (CASA-212) in August 2013 in background air over different locations in Slovenia and Germany. Each vertical profile consists of at least seven 5 min horizontal flight sections from 500 m above ground to 3000 m a.s.l. Gaseous elemental mercury (GEM) and total gaseous mercury (TGM) were measured with Tekran 2537X and Tekran 2537B analysers. In addition to the mercury measurements, SO2, CO, O3, NO, and NO2, basic meteorological parameters (pressure, temperature, relative humidity) have been measured. Additional ground-based mercury measurements at the GMOS master site in Waldhof, Germany and measurements onboard the CARIBIC passenger aircraft were used to extend the profile to the ground and upper troposphere respectively. No vertical gradient was found inside the well-mixed boundary layer (variation of less than 0.1 ng m−3) at different sites, with GEM varying from location to location between 1.4 and 1.6 ng m−3 (standard temperature and pressure, STP: T = 273.15 K, p = 1013.25 hPa). At all locations GEM dropped to 1.3 ng m−3 (STP) when entering the free troposphere and remained constant at higher altitudes. The combination of the vertical profile, measured on 21 August 2013 over Leipzig, Germany, with the CARIBIC measurements during ascent and descent to Frankfurt Airport, Germany, taken at approximately the same time, provide a unique central European vertical profile from inside the boundary layer (550 m a.s.l) to the upper free troposphere (10 500 m a.s.l.) and show a fairly constant free-tropospheric TGM concentration of 1.3 ng m−3 (STP).

Atmospheric speciated mercury concentrations on an island between China and Korea: sources and transport pathways

Abstract. As a global pollutant, mercury (Hg) is of particular concern in East Asia, where anthropogenic emissions are the largest. In this study, speciated Hg concentrations were measured on Yongheung Island, the westernmost island in Korea, located between China and the Korean mainland to identify the importance of local and regional Hg sources. Various tools including correlations with other pollutants, conditional probability function, and back-trajectory-based analysis consistently indicated that Korean sources were important for gaseous oxidized mercury (GOM) whereas, for total gaseous mercury (TGM) and particulate bound mercury (PBM), regional transport was also important. A trajectory cluster based approach, considering both Hg concentration and the fraction of time each cluster was impacting the site, was developed to quantify the effect of Korean sources and out-of-Korean sources. This analysis suggests that contributions from out-of-Korean sources were similar to Korean sources for TGM whereas Korean sources contributed slightly more to the concentration variations of GOM and PBM compared to out-of-Korean sources. The ratio of GOM/PBM decreased when the site was impacted by regional transport, suggesting that this ratio may be a useful tool for identifying the relative significance of local sources vs. regional transport. The secondary formation of PBM through gas-particle partitioning with GOM was found to be important at low temperatures and high relative humidity.

Characteristics of atmospheric particulate mercury in size-fractionated particles during haze days in Shanghai

Atmospheric particulate mercury (PHg) is recognized as a global pollutant that requires regulation because of its significant impacts on both human health and wildlife. The haze episodes that occur frequently in China could influence the transport and fate of PHg. To examine the characteristics of PHg during haze and non-haze days, size-fractioned particles were collected using thirteen-stage Nano-MOUDI samplers (10 nm–18 μm) during a severe haze episode (from December 2013 to January 2014) in Shanghai. The PHg concentration on haze days (4.11 ± 0.53 ng m−3) was three times higher than on non-haze days (1.34 ± 0.15 ng m−3). The ratio of the PHg concentration to total gaseous mercury (TGM) ranged from 0.42 during haze days to 0.21 during non-haze days, which was possibly due to the elevated concentration of particles for gaseous elemental mercury (GEM) adsorption, elevated sulfate and nitrate contributing to GEM oxidation, and the catalytic effect of elevated water-soluble inorganic metal ions. PHg/PM10 during haze days (0.019 ± 0.004 ng/μg) was lower than during non-haze days (0.024 ± 0.002 ng/μg), and PHg/PM10 was significantly reduced with an increasing concentration of PM10, which implied a relatively lower growth velocity of mercury than other compositions on particles during haze days, especially in the diameter range of 0.018–0.032 μm.During haze days, each size-fractioned PHg concentration was higher than the corresponding fraction on non-haze days, and the dominant particle size was in the accumulation mode, with constant accumulation to a particle size of 0.56–1.0 μm. The mass size distribution of PHg was bimodal with peaks at 0.32–0.56 μm and 3.1–6.2 μm on non-haze days, and 0.56–1.0 μm and 3.1–6.2 μm on haze days. There was a clear trend that the dominant size for PHg in the fine modes shifted from 0.32–0.56 μm during non-haze days to 0.56–1.0 μm on haze days, which revealed the higher growth velocity of PHg on haze days due to the condensation and accumulation of Hg in particles. Traffic emissions and coal combustion may contribute to the high concentrations of Hg, because PHg of every size was found to correlate positively with SO2, NO2, and CO. A correlation was found between every mode of PHg and relative humidity, which affected the gas-particle partitioning of semi-volatile organic compounds, resulting in effective partitioning into aerosols. The strong correlations between Hg and water-soluble ions implied the oxidation of elemental Hg was the main gas-to-particle chemical transformation process.

Atmospheric mercury at an urban station in Korea across three decades

The concentrations of total gaseous mercury (TGM) over three decades (1987–2013) were monitored at an urban station at Yan San (YS), Seoul, Korea. The results were examined by considering the prominent patterns in observed concentrations during periods where data were available: [1] period I (P1) = Sep. 1987 to Oct. 1988, [2] period II (P2) = Sep. 1999 to Jul. 2000, [3] period III (P3) = Jan. 2004 to Dec. 2011, and [4] period IV (P4) = Jan. 2012 to Dec. 2013. The data in this study indicate that the concentrations of TGM decreased abruptly from P1 (∼15 ng m−3) to P2 (∼5 ng m−3). Then, during the most of P3 (i.e., from 2004 to 2011), the annual mean values were nearly constant and their concentrations were in the range 3–4 ng m−3. The mean values then decreased to ∼2 ng m−3 in P4. Hg levels in the late 1980s reflect the dominant role of major man-made source processes (e.g., unabated combustion of much dirtier fossil fuels). Unlike the earlier Hg monitoring data, the concentrations of Hg in recent periods could be attributed to a shift from coal to kerosene and natural gas in urban areas and to more stringent emissions regulations and cleaner fuels. It is unclear currently whether the latest and lowest concentrations measured during in P4 will be maintained during upcoming years, although they seem to reflect the direct impact of air quality control efforts since the 1980s.

Mercury in terrestrial forested systems with highly elevated mercury deposition in southwestern China: The risk to insects and potential release from wildfires

Forests are considered a pool of mercury in the global mercury cycle. However, few studies have investigated the distribution of mercury in the forested systems in China. Tieshanping forest catchment in southwest China was impacted by mercury emissions from industrial activities and coal combustions. Our work studied mercury content in atmosphere, soil, vegetation and insect with a view to estimating the potential for mercury release during forest fires. Results of the present study showed that total gaseous mercury (TGM) was highly elevated and the annual mean concentration was 3.51 ± 1.39 ng m−2. Of the vegetation tissues, the mercury concentration follows the order of leaf/needle > root > bark > branch > bole wood for each species. Total ecosystem mercury pool was 103.5 mg m−2 and about 99.4% of the mercury resides in soil layers (0–40 cm). The remaining 0.6% (0.50 mg m−2) of mercury was stored in biomass. The large mercury stocks in the forest ecosystem pose a serious threat for large pluses to the atmospheric mercury during potential wildfires and additional ecological stress to forest insect: dung beetles, cicada and longicorn, with mercury concentration of 1983 ± 446, 49 ± 38 and 7 ± 5 ng g−1, respectively. Hence, the results obtained in the present study has implications for global estimates of mercury storage in forests, risks to forest insect and potential release to the atmosphere during wildfires.

Seasonal Variations of Total Gaseous Mercury at a French Coastal Mediterranean Site

The seasonal variation and spatial distribution of atmospheric particles at three islands in the Taiwan Strait were investigated. Atmospheric particles (PM10) were collected at three offshore islands (i.e., Kinmen islands, Matsu islands, and Penghu Islands) and two coastal regions (i.e., Xiamen and Fuzhou) in the years of 2008–2012. Field sampling results indicated that the average PM10 concentrations at the Kinmen islands were generally higher than other sampling sites, suggesting that a superimposition phenomenon was regularly observed during the air pollution episodes at Kinmen Islands and Xiamen region. PM10 samples were analyzed for their chemical composition, including water-soluble ions, metallic elements, and carbonaceous content. The most abundant water-soluble ionic species of PM10 were recognized as SO42–, NO3–, and NH4+, indicating that PM10 was mainly composed of secondary inorganic aerosols. Although natural crustal elements dominated the metallic content of PM10, the most abundant anthropogenic metals of PM10 were Zn and Pb. Enrichment factor calculations showed that Ni, Cr, and Zn were the enriched elements emitted mainly from anthropogenic sources. Moreover, the OC concentration of PM10 was always higher than that of EC at all sampling sites. High OC/EC ratios of PM10 were commonly observed at the sampling sites on the Matsu Islands, the Fuzhou region, and the Penghu Islands. Source apportionment results indicated that vehicular exhausts were the main source of PM10, and followed by industrial boilers, secondary aerosols, soil dusts, biomass burning, petrochemical plants, steel plants, oceanic spray, and cement plants at the island and coastal sampling sites in the Taiwan Strait. Highlights ► Investigation of 2 years of TGM at a French coastal Mediterranean site. ► Daily variations of TGM are observed, due to local industrial or urban activities. ► Seasonal variations are due to the dispersion of pollutants in the troposphere. ► High TGM concentrations are due to air masses coming from local or regional sources.

Boundary layer new particle formation over East Antarctic sea ice – possible Hg-driven nucleation?

Abstract. Aerosol observations above the Southern Ocean and Antarctic sea ice are scarce. Measurements of aerosols and atmospheric composition were made in East Antarctic pack ice on board the Australian icebreaker Aurora Australis during the spring of 2012. One particle formation event was observed during the 32 days of observations. This event occurred on the only day to exhibit extended periods of global irradiance in excess of 600 W m−2. Within the single air mass influencing the measurements, number concentrations of particles larger than 3 nm (CN3) reached almost 7700 cm−3 within a few hours of clouds clearing, and grew at rates of 5.6 nm h−1. Formation rates of 3 nm particles were in the range of those measured at other Antarctic locations at 0.2–1.1 ± 0.1 cm−3 s−1. Our investigations into the nucleation chemistry found that there were insufficient precursor concentrations for known halogen or organic chemistry to explain the nucleation event. Modelling studies utilising known sulfuric acid nucleation schemes could not simultaneously reproduce both particle formation or growth rates. Surprising correlations with total gaseous mercury (TGM) were found that, together with other data, suggest a mercury-driven photochemical nucleation mechanism may be responsible for aerosol nucleation. Given the very low vapour pressures of the mercury species involved, this nucleation chemistry is likely only possible where pre-existing aerosol concentrations are low and both TGM concentrations and solar radiation levels are relatively high (∼ 1.5 ng m−3 and ≥ 600 W m−2, respectively), such as those observed in the Antarctic sea ice boundary layer in this study or in the global free troposphere, particularly in the Northern Hemisphere.

Investigation of factors affecting mercury emission from subtropical forest soil: A field controlled study in southwestern China

Recent studies demonstrated that subtropical forest in China was considered as a large pool of atmospheric mercury and soils of forested watershed is a large reservoir of atmospherically deposited mercury. However, forest ecosystems not only act as sinks but also as sources of previously deposited mercury emitted back to the atmosphere. In this study a field controlled method was performed in Tieshanping National Forest Park (TNFP) to identify the effects of the most important parameters that controlled mercury emissions from soil surfaces, including chamber flushing flow turnover times (TOTs), soil water content and watering, total gaseous mercury (TGM) in air and understory. Flushing flow rates significantly affected the calculation of mercury flux and the optimal TOTs were 0.94min in the forest. TGM in atmosphere was significantly inhibited mercury emission from soils, and the deposited mercury was not absorbed firmly by the soils in a short time and emitted back to atmosphere rapidly when TGM concentration decreased. Higher soil moisture reduced the emission of mercury and initial watering produces a spike in the mercury emissions due to the interstitial soil gas mercury displaced by infiltrating water physically. However, subsequent watering was reducing the fluxes, because surface soil was saturated and soil pores were blocked by water film and inhibited the soil mercury emission. Soils under the understory had a higher mercury concentrations and deep organic layers. However, the fluxes of soil under the understory significantly were inhibited in daytime because solar radiation was blocked by the understory and the higher litter layer.

Total gaseous mercury levels over the Northwestern Pacific Ocean and around Iceland: Oceanic, volcanic and geothermal influences

Total gaseous mercury levels over the Northwestern Pacific Ocean and around Iceland: Oceanic, volcanic and geothermal influences