Average Total Gaseous Mercury Concentration Research Articles

Characteristics of total gaseous mercury at a tropical megacity in Vietnam and influence of tropical cyclones

Southeast Asia (SEA) has been suggested as a hotspot of mercury (Hg) emission worldwide but research on atmospheric Hg remains scarce in this region. This study reported monitoring data of total gaseous mercury (TGM) at Ho Chi Minh City (HCMC), a tropical megacity in SEA. TGM was measured over a 6-month period (June–November) in 2022 during two distinct monsoon seasons in HCMC. The average TGM concentration at HCMC was 1.89 ± 0.55 ng m−3 being comparatively lower than other sites in East Asia. For seasonal variation, changes in air mass origins resulted in a nearly 50% more elevated TGM concentration during October–November (2.47 ± 0.56 ng m−3) as compared to June–September (1.71 ± 0.40 ng m−3). Meanwhile, planetary boundary height and anthropogenic activities were responsible for TGM diurnal variation. Both backward trajectory and PSCF analysis revealed East Asian outflow as an important factor contributing to higher TGM levels at the sampling site. This study identified two instances of tropical cyclones affecting HCMC. For the event in July, TGM concentrations decreased due to the increases in atmospheric disturbances and the contribution of marine air masses. On the other hand, for the event in October, the increase in TGM concentration was possibly due to the enhancement export of polluted air mass from continental East Asia, induced by the tropical cyclone. This study provided valuable atmospheric Hg data in SEA, propose further insight into regional Hg understanding and suggest the impact of monsoon influence on local and regional Hg pollution.

Atmospheric mercury in an eastern Chinese metropolis (Jinan)

Urban emissions are a major contributor to atmospheric Hg budgets. Continuous measurements of total gaseous mercury (TGM) and particulate-bound mercury (PHg) in PM2.5 were conducted from October 2015 to July 2016 in a metropolis, Jinan, in eastern China. Average TGM and PHg concentrations were 4.91±3.66ngm-3 and 451.9±433.4pgm-3, respectively, in the entire study period. During the winter heating period (HP), mean concentrations of TGM and PHg were 5.79ngm-3 and 598.7pgm-3, respectively, twice higher than those during the non-heating periods (NHPs). During the HP, TGM exhibited a distinct diurnal pattern with a peak in the morning and a minimum in the afternoon on less polluted days but a singular peak at midday on heavily polluted days. The diurnal variation of TGM during the NHPs was predominantly influenced by the variation in boundary layer height while during the HP by anthropogenic emissions. The ratio of PHg/PM2.5 in Jinan was one to two orders of magnitude larger than those elsewhere worldwide and those in soil and coal, which suggested the high enrichment of PHg in PM2.5 in Jinan. Correlation and principle component analysis results suggested that PHg and TGM had common combustion sources during the HP, whereas PHg resulted mainly from biomass burning and meteorological variations during the NHPs. High Hg concentrations in Jinan were mostly caused by emissions from coal-fired power plants, especially for those situated east of the sampling site. In addition, TGM and PHg concentrations significantly increased during haze and fog episodes, but decreased during a dust episode due possibly to strong ventilation conditions combined with partitioning of Hg between adsorption to PM2.5 and coarse dust particles.

Effects of Brownfield Remediation on Total Gaseous Mercury Concentrations in an Urban Landscape.

In order to obtain a better perspective of the impacts of brownfields on the land–atmosphere exchange of mercury in urban areas, total gaseous mercury (TGM) was measured at two heights (1.8 m and 42.7 m) prior to 2011–2012 and after 2015–2016 for the remediation of a brownfield and installation of a parking lot adjacent to the Syracuse Center of Excellence in Syracuse, NY, USA. Prior to brownfield remediation, the annual average TGM concentrations were 1.6 ± 0.6 and 1.4 ± 0.4 at the ground and upper heights, respectively. After brownfield remediation, the annual average TGM concentrations decreased by 32% and 22% at the ground and the upper height, respectively. Mercury soil flux measurements during summer after remediation showed net TGM deposition of 1.7 suggesting that the site transitioned from a mercury source to a net mercury sink. Measurements from the Atmospheric Mercury Network (AMNet) indicate that there was no regional decrease in TGM concentrations during the study period. This study demonstrates that evasion from mercury-contaminated soil significantly increased local TGM concentrations, which was subsequently mitigated after soil restoration. Considering the large number of brownfields, they may be an important source of mercury emissions source to local urban ecosystems and warrant future study at additional locations.

Seasonal variations of ambient air mercury species nearby an airport

This study focuses on the collection of ambient air mercury species (total gaseous mercury (TGM), reactive gaseous mercury (RGM), gaseous element mercury (GEM) and particulate bound mercury (PBM) pollutants at airport nearby sampling site during the year of Apr. 2016 to Mar. 2017 by using Four-stage gold amalgamation and denuder. The results indicated that the average TGM, RGM and GEM concentrations were 5.04±2.43ng/m3, 29.58±80.54pg/m3, 4.70±2.63ng/m3, respectively during the year of Apr. 2016 to Mar. 2017 (n=49) period at this airport sampling site nearby. In addition, the results also indicated that the average PBM concentrations in TSP and PM2.5 were 0.35±0.08ng/m3 and 0.09±0.03ng/m3, respectively. And the average PBM in TSP concentrations order follows as summer>autumn>spring>winter, while the average PBM in PM2.5 concentrations order follows as spring>summer>winter>autumn. Moreover, the average TGM, RGM and GEM concentrations order follow as spring>summer>autumn>winter. Finally, the Asian continent has the highest average mercury species concentrations (TGM, RGM, GEM and PBM) when compared with the American and European continents, and the average mercury species concentrations (TGM, RGM, GEM and PBM) displayed declined trends for North America (United States and Canada) and Europe (Spain, Sweden and Southern Baltic) during the years of 2004–2014. Also noteworthy is that the average mercury species concentrations (TGM, RGM, GEM) displayed increasing trends in China and Taiwan during the years of 2008–2016. Japan and Korea are the only two exceptions. Those above two countries mercury species concentrations displayed decreasing trends during years of 2008–2015.

Characteristics and Sources of Speciated Atmospheric Mercury at a Coastal Site in the East China Sea Region

ABSTRACTAtmospheric mercury is a global concern due to its ability of long-range transport. In order to understand the characteristics and sources of speciated mercury in the East China Sea region, a coastal monitoring site was established on Chongming Island in Shanghai, China. Total gaseous mercury (TGM), reactive gaseous mercury (RGM) and particulate-bound mercury (PHg) were monitored during 2009–2012. The overall average TGM, RGM and PHg concentrations were 2.65 ± 1.73 ng m–3, 8.0 ± 8.8 pg m–3 and 21.5 ± 25.4 pg m–3, respectively. TGM has a sharp increase at 5:00 in the morning and reaches peak at about 8:00, which is probably caused by the downward mixing of enhanced TGM aloft originated from regional sources. Wind roses suggest that urban Shanghai area has a considerable contribution to TGM in Chongming. Repartitioning of reactive mercury from particles to the air under the influence of air temperature could be one major source of RGM. Four heavy mercury pollution episodes were selected for source analysis. Mercury pollution in the summer event is mainly from the southwest direction with high ∆TGM/∆CO ratio and has the most influence on the North China Plain (NCP) region. The winter event is mainly under the influence of industrial pollution from the NCP region. The autumn event is contributed by both industrial pollution and biomass burning in North and Northeast China exhibiting a lower slope of ∆PHg/∆TGM. Springtime Asian long-range transport (ALRT) is crucial to the mercury background of North America. However, in the spring event identified in this study the mercury outflow from low altitude through East China mostly ascended to high altitude during the transpacific airmass transport. This provides an important incentive for future studies to focus on the way of mercury outflow from East Asia.

Field Measurement of Total Gaseous Mercury and Its Correlation with Meteorological Parameters and Criteria Air Pollutants at a Coastal Site of the Penghu Islands

This study investigated the seasonal and daily variations of the total gaseous mercury (TGM) concentration in the ambient atmosphere, the correlation of TGM concentration with meteorological parameters (e.g., temperature, humidity, and wind speed) and criteria air pollutant concentrations (e.g., SO2, NOx, CO, O3, PM10, and PM2.5), as well as the transportation routes, at the Penghu Islands. The field measurement results showed that the average TGM concentration during the monitoring period was 3.17 ± 1.17 ng/m3, within the range of 1.17–8.63 ng/m3, with the highest concentration being observed in spring, while the TGM concentration typically increased in the morning, reached its peak concentration, and then started to decrease at nightfall. Moreover, the lowest average TGM concentration of 1.81 ± 0.15 ng/m3 was observed in summer, and this figure is close to the background TGM concentration of the Northern Hemisphere (1.6–1.8 ng/m3). The correlation analysis indicated that TGM concentration correlated positively with SO2, NOx, CO, O3, PM10, and PM2.5 and negatively with ambient temperature, relative humidity, and wind speed. In addition, the transportation route analysis showed that elevated TGM concentrations could be transported from either North China, East China, or South China to the Penghu Islands, while those originating from the South China Sea had the lowest contribution to the TGM levels at the Penghu Islands. Therefore, local sources and open burning might be mainly influenced by the long-range transportation of air masses, as the prevailing wind direction and air mass transportation routes potentially play critical roles in the variation of TGM concentration at the Penghu Islands.

Analytical performances of nanostructured gold supported on metal oxide sorbents for the determination of gaseous mercury.

Nanostructured gold supported TiO2, ZnO, and Al2O3 materials (1% w/w Au) were tested as sorbents for gaseous mercury (Hg) trapping and preconcentration. Their analytical performances were first compared with the one of traditional gold wool trap for the quantification of Hg standards injected into the argon flow followed by thermal desorption at 600°C and CVAFS detection. Good linearity and reproducibility were obtained, especially for Au/TiO2 material (R 2 = 0.995; slope: 1.39) in the volume range of 10 to 60 µL (132–778 pg Hg). This latter even showed a better performance compared to pure Au in the volume range of 10 to 100 µL (132–1329 pg Hg) when the carrier gas flow was increased from 60 to 100 mL min−1. The method detection limit (MDL) obtained with Au/TiO2 trap (0.10 pg Hg0 L−1) was suitable for total gaseous mercury (TGM) determination. Au/TiO2 was, therefore, used in trapping and determining TGM in collected air samples. TGM values in the samples ranged from 6 to 10 ng m−3. Similar results were obtained with the commercial gold-coated sand trap which showed an average TGM concentration of 7.8 ± 0.9 ng m−3.

Total Gaseous Mercury Concentration Measurements at Fort McMurray, Alberta, Canada

Observations are described from total gaseous mercury (TGM) concentrations measured at the Wood Buffalo Environmental Association (WBEA) Fort McMurray—Patricia McInnes air quality monitoring station—from 21 October 2010 through 31 May 2013, inclusively. Fort McMurray is approximately 380 km north-northeast of Edmonton, Alberta, and approximately 30 km south of major Canadian oil sands developments. The average TGM concentration over the period of this study was 1.45 ± 0.18 ng∙m−3. Principal component analysis suggests that observed TGM concentrations are correlated with meteorological conditions including temperature, relative humidity, and solar radiation, and also ozone concentration. There is no significant correlation between ambient concentrations of TGM and anthropogenic pollutants, such as nitrogen oxides (NOX) and sulphur dioxide (SO2). Principal component analysis also shows that the highest TGM concentrations observed are a result of forest fire smoke near the monitoring station. Back trajectory analysis highlights the importance of long-range transport, indicating that unseasonably high TGM concentrations are generally associated with air from the southeast and west, while unseasonably low TGM concentrations are a result of arctic air moving over the monitoring station. In general, TGM concentration appears to be driven by diel and seasonal trends superimposed over a combination of long-range transport and regional surface-air flux of gaseous mercury.

Mercury emission from coal seam fire at Wuda, Inner Mongolia, China

The underground coal seam fire in the Wuda, Inner Mongolia of china is one of the most serious coal fires in the world with a history over 50 years and endangers the neighboring downwind urban area. To investigate the potential mercury emission and migration from the coal seam fire, in situ real-time measurement of total gaseous mercury (TGM) concentration using Lumex RA-915 + mercury analyzer were implemented on the fire zone and the urban area. The results show an average TGM concentration of 464 ng m−3 in the fumes released from surface vents and cracks on the fire zone, which leads to an elevated TGM concentration of 257 ng m−3 (211–375 ng m−3) in the near-surface air at the fire zone and 89 ng m−3 (23–211 ng m−3) at the peripheral area. The average TGM concentration in the adjoining downwind urban area of Wuda is 33 ng m−3. This result suggests that the coal seam fire may not only contribute to the global mercury inventory but also be a novel source for mercury pollution in the urban areas. The scenario of urban areas being adjacent to coal seam fires is not limited to Wuda but relatively common in northern China and elsewhere. Whether there are other cities under influence of coal seam fires merits further investigation.

Variation trends and influencing factors of total gaseous mercury in the Pearl River Delta—A highly industrialised region in South China influenced by seasonal monsoons

Studies on atmospheric mercury in the Pearl River Delta (PRD) region are important because of the economic relevance of this region to China, because of its economic developmental pattern and because it is a highly industrialised area influenced by the strong seasonal monsoons. Total gaseous mercury (TGM), meteorological parameters and criteria pollutant concentrations were measured at Mt. Dinghu (DH, a regional monitoring site) and Guangzhou (GZ, an urban monitoring site) in the PRD region from October 2009 to April 2010 and from November 2010 to November 2011, respectively. The ranges of daily average TGM concentrations at the DH and GZ sites were 1.87–29.9 ng m−3 (5.07 ± 2.89 ng m−3) and 2.66–11.1 ng m−3 (4.60 ± 1.36 ng m−3), respectively, which were far more significant than the background values in the Northern Hemisphere (1.5–1.7 ng m−3), suggesting that the atmosphere in the PRD has suffered from mercury pollution. Similar TGM seasonal distributions at the two sites were observed, with a descending order of spring, winter, autumn and summer. The different seasonal monsoons were the dominant factor controlling the seasonal variability of the TGM, with variations in the boundary layer and oxidation also possibly partially contributing. Different diurnal patterns of the TGM at two sites were observed. TGM levels during the daytime were higher than those during the nighttime and were predominantly influenced by mountain and valley winds at the DH site, whereas the opposite trend was evident at the GZ site, which was primarily influenced by the boundary-layer height and O3 concentration. During the monitoring period, the correlations between the daily TGM levels and the SO2 and NO2 levels at the DH site were significant (r = 0.36, p < 0.001; r = 0.29, p < 0.001), suggesting that coal-fired emission is an important source of mercury for this regional monitoring site. At the GZ site, the correlations between the daily TGM level and the NO, NO2, CO levels were significant (r = 0.501, p < 0.001; r = 0.579, p < 0.001; r = 0.358, p < 0.001). However, TGM was partially correlated with SO2, suggesting that the combined vehicle emissions and coal combustion were the dominant mercury sources for this urban monitoring site. The TGM distribution figure, which related to the wind-rose pattern and the distribution figure of emission sources, indicated significant contributions from anthropogenic emission sources.

Characteristics of atmospheric Total Gaseous Mercury (TGM) observed in urban Nanjing, China

Abstract. Long-term continuous measurements of total gaseous mercury (TGM = gaseous elemental mercury (GEM) + reactive gaseous mercury (RGM)) were conducted simultaneously along with meteorological variables and a suite of trace gases at an urban site in Nanjing, China from 18 January to 31 December 2011. Measurements were conducted using a high resolution mercury vapor analyzer (Tekran 2537B) with 5-min time resolution. The average concentration of TGM was 7.9 ± 7.0 ng m−3 with a range of 0.8–180 ng m−3 over the study period. TGM concentrations followed a typical lognormal pattern dominated by a range of 3–7 ng m−3, which was significantly higher than the continental background values (~1.5 ng m−3) in Northern Hemisphere. The mean seasonal TGM concentrations decreased in the following order: summer, spring, fall, and winter. This seasonal pattern was quite different from measurements at most other sites around the world. We attributed high monthly average concentrations to the re-volatilization of deposited mercury during the warm season due to high temperatures and greater solar radiation. Previous modeling studies suggested that Nanjing and the surrounding region have the largest Chinese natural emissions during the summer. Positive correlations between temperature, solar radiation, and TGM concentration combined with no correlation between CO and TGM in summer provide a strong indication that natural sources are important in Nanjing while most sharp peaks were caused by anthropogenic sources. TGM concentrations in Nanjing exhibited a noticeable diurnal pattern with a sharp increase after sunrise and peak of greater than 8 ng m−3 during 7–10 a.m. local time. Further, seasonally averaged diurnal cycles of TGM exhibited considerably different patterns with the largest variation in spring and insignificant fluctuations in winter. Using HYSPLIT backwards trajectories from six clusters, it was indicated that the highest TGM concentrations, 11.9 ng m−3, was derived from local air masses. The cleanest air masses, with an average TGM concentration of 4.7 and 5.9 ng m−3, were advected from the north via fast transport facilitated by sweeping synoptic flows.

Total Mercury and Particulate-Bound Mercury Concentrations and Content in Ambient Air in Central Taiwan

Total gaseous mercury (TGM) concentration in ambient air, particulate-bound mercury concentrations and particulate-bound mercury contents in total suspended particles (TSP) from locations in Central Taiwan were measured and discussed relative to their ranges and potential sources. Meteorological conditions in terms of average temperature, wind direction, wind speed, and humidity were also monitored at a traffic sampling site in Sha-Lu central Taiwan from July 2011 to November 2011. The results revealed that the average concentrations of total gaseous mercury (TGM) and particulate-bound mercury in TSP were 8.73±5.53 (ng/m3) and 0.000164±0.00007 (ng/m3), respectively. The monthly average TGM concentrations were highest in July (17.50±4.79 ng/m3) and lowest in November (4.10±0.72 ng/m3). The monthly average particulate-bound mercury concentrations were highest in July (0.000293±0.00021 ng/m3) and lowest in November (0.000109±0.00002 ng/m3). The average particulate-bound mercury Hg(p) contents were 0.15 (ng/g), while the monthly average particulate-bound mercury contents were highest in July (0.26 ng/g) and lowest in November (0.11 ng/g). In summer, industrial activities, especially smelting activities, were an important source of atmospheric Hg (Fu et al., 2009). Therefore, high mercury concentrations were observed in July and August. Several main sources of Hg emissions have also been identified in the study area.

Hybrid receptor model을 이용한 대기 중 총 가스상 수은의 오염원 위치 추정 연구

The objectives of this study were to measure ambient total gaseous mercury (TGM) concentrations in Seoul, to analyze the characteristics of TGM concentration, and to identify of possible source areas for TGM using back-trajectory based hybrid receptor models like PSCF (Potential Source Contribution Function) and RTWC (Residence Time Weighted Concentration). Ambient TGM concentrations were measured at the roof of Graduate School of Public Health building in Seoul for a period of January to October 2004. Average TGM concentration was 3.43±1.17 ng/㎥. TGM had no notable pattern according to season and meteorological phenomena such as rainfall, Asian dust, relative humidity and so on. Hybrid receptor models incorporating backward trajectories including potential source contribution function (PSCF) and residence time weighted concentration (RTWC) were performed to identify source areas of TGM. Before hybrid receptor models were applied for TGM, we analysed sensitivities of starting height for HYSPLIT model and critical value for PSCF. According to result of sensitivity analysis, trajectories were calculated an arrival height of 1000 m was used at the receptor location and PSCF was applied using average concentration as criterion value for TGM. Using PSCF and RTWC, central and eastern Chinese industrial areas and the west coast of Korea were determined as important source areas. Statistical analysis between TGM and GEIA grided emission bolsters the evidence that these models could be effective tools to identify possible source area and source contribution.

Identification of potential regional sources of atmospheric total gaseous mercury in Windsor, Ontario, Canada using hybrid receptor modeling

Abstract. Windsor (Ontario, Canada) experiences trans-boundary air pollution as it is located on the border immediately downwind of industrialized regions of the United States of America. A study was conducted in 2007 to identify the potential regional sources of total gaseous mercury (TGM) and investigate the effects of regional sources and other factors on seasonal variability of TGM concentrations in Windsor. TGM concentration was measured at the University of Windsor campus using a Tekran® 2537A Hg vapour analyzer. An annual mean of 2.02±1.63 ng/m3 was observed in 2007. The average TGM concentration was high in the summer (2.48±2.68 ng/m3) and winter (2.17±2.01 ng/m3), compared to spring (1.88±0.78 ng/m3) and fall (1.76±0.58 ng/m3). Hybrid receptor modeling potential source contribution function (PSCF) was used by incorporating 72-h backward trajectories and measurements of TGM in Windsor. The results of PSCF were analyzed in conjunction with the Hg emissions inventory of North America (by state/province) to identify regions affecting Windsor. In addition to annual modeling, seasonal PSCF modeling was also conducted. The potential source region was identified between 24–61° N and 51–143° W. Annual PSCF modeling identified major sources southwest of Windsor, stretching from Ohio to Texas. The emissions inventory also supported the findings, as Hg emissions were high in those regions. Results of seasonal PSCF modeling were analyzed to find the combined effects of regional sources, meteorological conditions, and surface re-emissions, on seasonal variability of Hg concentrations. It was found that the summer and winter highs of atmospheric Hg can be attributed to areas where large numbers of coal fired power plants are located in the USA. Weak atmospheric dispersion due to low winds and high re-emission from surfaces due to higher temperatures also contributed to high concentrations in the summer. In the winter, the atmospheric removal of Hg was slow, but strong winds led to more dispersion, resulting in lower concentrations than the summer. Future studies could use smaller grid sizes and refined emission inventories, for more accurate analysis of source-receptor relationship of atmospheric Hg.

Aerosol trace metals, particle morphology and total gaseous mercury in the atmosphere of Oxford, UK

An investigation of atmospheric trace metals was conducted in Oxford, UK, a small city ∼60 miles northwest of London, in 2007 and 2008. Concentrations of Sr, Mo, Cd, Pb, V, Cr, Mn, Fe, Co, Ni, Cu and Zn in aerosol were measured in bulk and size segregated samples. In addition, total gaseous mercury (TGM) concentrations were monitored semi-continuously by cold vapour-atomic fluorescence spectroscopy. Metal concentrations in Oxford were intermediate between previously reported levels of UK rural and urban areas for most metals studied and levels of Cd, Ni and Pb were within European guidelines. Metal concentrations appeared to be influenced by higher traffic volume on a timescale of hours. The influence of traffic on the aerosols was also suggested by the observation of carbonaceous particles via scanning electron microscopy (SEM). Air mass back trajectories suggest air masses arriving in Oxford from London and mainland Europe contained the highest metal concentrations. Aerosol samples collected over Bonfire Weekend, a period of intense firework use and lighting of bonfires in the UK, showed metal concentrations 6–46 times higher than at other times. Strontium, a tracer of firework release, was present at higher concentrations and showed a change in its size distribution from the coarse to fine mode over Bonfire Weekend. The presence of an abundance of spherical Sr particles was also confirmed in SEM images. The average TGM concentration in Oxford was 3.17 ng m −3 (st. dev. 1.59) with values recorded between 1.32 and 23.2 ng m −3. This is a higher average value than reported from nearby rural locations, although during periods when air was arriving from the west, similar concentrations to these rural areas were seen in Oxford. Comparison to meteorological data suggests that TGM in Oxford's air is highest when wind is arriving from the east/southeast. This may be due to emissions from London/mainland Europe with a possible contribution from emissions from a local crematorium situated 4 miles east of the sampling site. A diurnal pattern was also observed in the TGM data with a minimum concentration during the day when mercury may have been diluted by thermal mixing of the atmospheric boundary layer. Additionally, this diurnal pattern may reflect variations in a local source of TGM.

Atmospheric mercury cycles in northern Wisconsin

Total gaseous mercury (TGM) in the lower atmosphere of northern Wisconsin exhibits strong annual and diurnal cycles similar to those previously reported for other rural monitoring sites across mid-latitude North America. Annually, TGM was highest in late winter and then gradually declined until late summer. During 2002–04, the average TGM concentration was 1.4 ± 0.2 (SD) ng m −3, and the amplitude of the annual cycle was 0.4 ng m −3 (∼30% of the long-term mean). The diurnal cycle was characterized by increasing TGM concentrations during the morning followed by decreases during the afternoon and night. The diurnal amplitude was variable but it was largest in spring and summer, when daily TGM oscillations of 20–40% were not uncommon. Notably, we also observed a diurnal cycle for TGM indoors in a room ventilated through an open window. Even though TGM concentrations were an order of magnitude higher indoors, (presumably due to historical practices within the building: e.g. latex paint, fluorescent lamps, thermometers), the diurnal cycle was remarkably similar to that observed outdoors. The indoor cycle was not directly attributable to human activity, the metabolic activity of vegetation or diurnal atmospheric dynamics; but it was related to changes in temperature and oxidants in outdoor air that infiltrated the room. Although there was an obvious difference in the proximal source of indoor and outdoor TGM, similarities in behavior suggest that common TGM cycles may be driven largely by adsorption/desorption reactions involving solid surfaces, such as leaves, snow, dust and walls. Such behavior would imply a short residence time for Hg in the lower atmosphere and intense recycling – consistent with the “ping-pong ball” or “multi-hop” conceptual models proposed by others.

Characteristics of atmospheric speciated mercury concentrations (TGM, Hg(II) and Hg(p)) in Seoul, Korea

Ambient speciated mercury concentrations including total gaseous mercury (TGM), gaseous divalent mercury (Hg(II)), and particulate mercury (Hg(p)) were measured on the roof of the Graduate School of Public Health building in Seoul, Korea from February 2005 to February 2006. The average concentrations were 3.22 ± 2.10 ng m −3, 27.2 ± 19.3 pg m −3, and 23.9 ± 19.6 pg m −3 for TGM, Hg(II), and Hg(p), respectively. Hg(II) and Hg(p) concentrations were higher during the daytime than during the nighttime, probably because of high photochemical activity. Hg 0 concentrations were not significantly correlated with ozone however a positive correlation between ozone and Hg(II) was found during periods of high humidity. Eighteen days were characterized as pollution events with 24 h average PM 2.5 concentrations >65 μg m −3. The average concentrations of TGM and Hg(p) during these events were 1.4–2 times higher than those during non-pollution events. In order to identify the contribution of long-range transported mercury to the enhanced mercury concentrations in Korea, an episode was defined as a period with hourly average TGM and CO concentrations higher than the monthly average TGM and CO concentrations and with significant enhancement of both TGM and CO concentrations for at least 10 h. A total of 70 episodes were identified during the sampling period: 36 local episodes and 34 long-range transport episodes. The mean ΔTGM/ΔCO slope for all episodes was 0.0063 ng m −3 ppbv −1 which agreed well with the slope (0.0036–0.0074 ng m −3 ppbv −1) found in previous studies that identified long-range transport of TGM from China. The mean slope during non-events was 0.0011 ng m −3 ppbv −1. Back-trajectory analysis showed that during episodes, air parcels arrived mostly from the major industrial areas in China ( n = 25, 73%), followed by Japan ( n = 4, 12%), Yellow Sea ( n = 3, 9%), and Russia ( n = 2, 6%).

Exchange fluxes of Hg between surfaces and atmosphere in the eastern flank of Mount Gongga, Sichuan province, southwestern China

In situ total gaseous mercury (TGM) concentrations and mercury exchange fluxes from 17 sampling sites of three representative landscapes (agriculture, grassland, and forest) were intensively measured in the eastern flank of Mount Gongga area, Sichuan province, southwestern China, from October 2005 to September 2006. Average TGM concentrations in ambient air ranged from 1.60 to 5.10 ng m−3 in warm season, while the values were highly elevated in cold season with the highest mean TGM concentration of 7.65 ng m−3. Hg fluxes from agriculture and grassland sampling sites showed clearly seasonal distribution pattern with net depositions observed in cold season and net emissions observed in warm season. Mean Hg fluxes at agriculture and grassland field fell in the range from −4.1 to 132.0 ng m−2 h−1 and from −18.7 to 13.4 ng m−2 h−1, respectively, while mean Hg fluxes from forest sites varied from 0.5 to 9.3 ng m−2 h−1. Notable diurnal pattern of Hg fluxes were observed from all sampling sites, with the maximum Hg fluxes observed at midday and the minimum values observed during the nighttime. TGM concentrations in cold season significantly negatively correlated with Hg flux, suggesting that highly elevated TGM concentration could inhibit Hg emission even cause significant deposition. Vegetation acted as a great sink of air Hg in cold season, while in warm season, it could significantly inhibit Hg emission from surfaces.

Characteristics of mercury exchange flux between soil and air in the heavily air-polluted area, eastern Guizhou, China

To investigate the characteristics of mercury exchange between soil and air in the heavily air-polluted area, total gaseous mercury (TGM) concentration in air and Hg exchange flux were measured in Wanshan Hg mining area (WMMA) in November, 2002 and July–August, 2004. The results showed that the average TGM concentrations in the ambient air (17.8–1101.8 ng m −3), average Hg emission flux (162–27827 ng m −2 h −1) and average Hg dry deposition flux (0–9434 ng m −2 h −1) in WMMA were 1–4 orders of magnitude higher than those in the background area. It is said that mercury-enriched soil is a significant Hg source of the atmosphere in WMMA. It was also found that widely distributed roasted cinnabar banks are net Hg sources of the atmosphere in WMMA. Relationships between mercury exchange flux and environmental parameters were investigated. The results indicated that the rate of mercury emission from soil could be accelerated by high total soil mercury concentration and solar irradiation. Whereas, highly elevated TGM concentrations in the ambient air can restrain Hg emission from soil and even lead to strongly atmospheric Hg deposition to soil surface. A great amount of gaseous mercury in the heavily polluted atmosphere may cycle between soil and air quickly and locally. Vegetation can inhibit mercury emission from soil and are important sinks of atmospheric mercury in heavily air-polluted area.

Biomonitoring of airborne mercury with perennial ryegrass cultures

A biomonitoring network with grass cultures was established near a chlor-alkali plant and the mercury concentration in the cultures were compared with the average atmospheric total gaseous mercury (TGM). Biomonitoring techniques based on different exposure periods were carried out. When comparing the mercury concentration in the grass cultures, both the average atmospheric TGM concentration during exposure and the exposure time determined to a large extent the accumulation rate of TGM. The maximum tolerable level of mercury in grass (≅110 μg kg −1 DM) corresponds with an average TGM concentration of 11 ng m −3 for 28 days exposure. The background concentrations in grass were on an average 15 μg kg −1 DM and the effect detection limit (EDL) was 30 μg kg −1 DM. This value corresponds with an average TGM concentration of 3.2 and 4.2 ng m −3 for 28 and 14 days exposure, respectively, which is in turn the biological detection limit (BDL) of ambient TGM. Exposures for 7 days were less appropriate for biomonitoring.