PHg Concentrations Research Articles

Pollution status and source resolution of atmospheric mercury in the intersectional region of Northern Philippines, southern Taiwan, and northern South China Sea

A four-season sampling of speciated atmospheric mercury (SAM) was employed in East Asia. Three mercury species including gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate mercury (PHg) were measured at three background sites. This study explored the temporal variation, spatial distribution, gas-solid partition, transport routes, and source resolution of SAM. The yearly average concentrations of GEM, GOM, and PHg were 2.76 ± 0.36 ng/m3, 23.14 ± 8.67 pg/m3, and 0.23 ± 0.058 ng/m3. The highest GEM and PHg concentrations occurred at Laoag (northern Philippines) in spring, while that of GOM was observed at Laoag but in summer. The lowest GEM and PHg concentrations always occurred at Dongsha Islands (northern South China Sea) in summer, while that of GOM was also observed at Dongsha Islands but in fall. SAM was partition as showed 92.64–96.72% of total gas-phase mercury (TGM) and 3.28–7.36% of solid phase mercury. Eight clustered transport routes were resolved by a HYSPLIT model with polluted air parcels originating from Central/North China. Routes from Indochina Peninsula and South China showed the highest GEM concentration. Moreover, air parcels transported from West Pacific Ocean and South China Sea (SCS) had the lowest concentration of GEM. High concentrations of SAM in the region were mainly attributed to long-range transport (LRT) from Asian continental outflows (ACOs). We further revealed that GEM was positively correlated to SO2, CO, NOx, and PM2.5, but negatively correlated to O3. GOM was positively correlated to SO2, O3, NOx, and PM2.5, but negatively correlated to CO, While, PHg was positively correlated to SO2, CO, O3, NOx, and PM2.5.

Mercury contamination in the water and sediments of a typical inland river – Lake basin in China: Occurrence, sources, migration and risk assessment

In the area affected by non-ferrous metal mining activities, mercury (Hg) contamination in the water and sediments posed potential risks to ecology and human health. In this study, river water and sediment samples were collected in the Zijiang river - South Dongting Lake basin to analyze Hg residues, identify potential Hg sources and evaluate the ecological and health risks posed by Hg contamination. In this study, the average concentrations of THg, PHg, DHg and DMeHg in river water were 38.05 ± 27.13 ng/L, 25.18 ± 26.83 ng/L, 12.88 ± 9.64 ng/L and 0.29 ± 0.07 ng/L, respectively. The THg and MeHg contents in sediments were 234.24 ± 152.93 µg/kg and 0.48 ± 0.16 µg/kg, respectively. The more enrichment of Hg in sediments was observed in the Zijiang River than in the South Dongting Lake, especially in the upstream and midstream regions. Two potential Hg sources in the basin were identified by correlation matrix, principal component analysis (PCA) and positive matrix factorization (PMF) model. The comparable Hg flux with other rivers worldwide was found in the Zijiang River (0.53 Mg/y). Furthermore, it was found by the delayed geochemical hazard (DGH) model that the ecological risk of Hg was more significant in the Zijiang River with more frequent transformation pathways. For different populations, the health risk values caused by Hg were all lower than the USEPA’s guideline value. This study provided sound evidence for further control of Hg contamination.

Sources of riverine mercury across the Mackenzie River Basin; inferences from a combined Hg[sbnd]C isotopes and optical properties approach

The Arctic environment harbors a complex mosaic of mercury (Hg) and carbon (C) reservoirs, some of which are rapidly destabilizing in response to climate warming. The sources of riverine Hg across the Mackenzie River basin (MRB) are uncertain, which leads to a poor understanding of potential future release. Measurements of dissolved and particulate mercury (DHg, PHg) and carbon (DOC, POC) concentration were performed, along with analyses of Hg stable isotope ratios (incl. ∆199Hg, δ202Hg), radiocarbon content (∆14C) and optical properties of DOC of river water. Isotopic ratios of Hg revealed a closer association to terrestrial Hg reservoirs for the particulate fraction, while the dissolved fraction was more closely associated with atmospheric deposition sources of shorter turnover time. There was a positive correlation between the ∆14C-OC and riverine Hg concentration for both particulate and dissolved fractions, indicating that waters transporting older-OC (14C-depleted) also contained higher levels of Hg. In the dissolved fraction, older DOC was also associated with higher molecular weight, aromaticity and humic content, which are likely associated with higher Hg-binding potential. Riverine PHg concentration increased with turbidity and SO4 concentration. There were large contrasts in Hg concentration and OC age and quality among the mountain and lowland sectors of the MRB, which likely reflect the spatial distribution of various terrestrial Hg and OC reservoirs, including weathering of sulfate minerals, erosion and extraction of coal deposits, thawing permafrost, forest fires, peatlands, and forests. Results revealed major differences in the sources of particulate and dissolved riverine Hg, but nonetheless a common positive association with older riverine OC. These findings reveal that a complex mixture of Hg sources, supplied across the MRB, will contribute to future trends in Hg export to the Arctic Ocean under rapid environmental changes.

Concentration and speciation of mercury in atmospheric particulates in the Wuda coal fire area, Inner Mongolia, China.

Coal-seam fire is a source of atmospheric mercury that is difficult to control. The Wuda Coalfield in Inner Mongolia, China, is one of the most severe coal fire disaster areas worldwide and has been burning for more than 50 years. To investigate atmospheric mercury pollution from the Wuda coal fire, gaseous elemental mercury (GEM) concentrations and atmospheric particulate mercury (PHg) speciation were measured using a RA-915+ mercury analyzer and the temperature-programmed desorption method. Near-surface GEM concentrations in the Wuda Coalfield and adjacent urban area were 80 ng m-3 (65-90 ng m-3) and 52 ng m-3 (25-95 ng m-3), respectively, which are far higher than the local background value (22 ng m-3). PHg concentrations in the coalfield and urban area also reached significantly high levels, 33 ng m-3 (25-45 ng m-3) and 22 ng m-3 (14-29 ng m-3), respectively (p < 0.05). There is no clear evidence that PHg combines with organic carbon or elemental carbon, but PHg concentration appears to be controlled by air acidity. PHg mainly exists in inorganic forms, such as HgCl2, HgS, HgO, and Hg(NO3)2·H2O. This work can provide references for the speciation analysis of atmospheric PHg and the safety assessment of environmental mercury.

Seasonal Evolution of Size-Segregated Particulate Mercury in the Atmospheric Aerosol Over Terra Nova Bay, Antarctica.

Size-fractionated particulate mercury (PHg) measurements were performed from November 2017 to January 2018 at Terra Nova Bay (Antarctica) for the first time. Samples were collected every 10 days by a six-stage high-volume cascade impactor with size classes between 10 μm and 0.49 μm. Total PHg concentrations were maxima (87 ± 8 pg m−3) in November, then decreased to values ~40% lower and remained almost constant until the end of the sampling period (~30 pg m−3). The trimodal aerosol mass distribution reveals that from 30% to 90% of the total PHg came in the size > 1.0 μm. Hg in the two coarse fractions was probably produced by the adsorption of oxidized Hg species transported by air masses from the Antarctic plateau or produced locally by sea ice edges. PHg in accumulation mode seemed to be related to gas–particle partitioning with sea salt aerosol. Finally, average dry deposition fluxes of PHg were calculated to be 0.36 ± 0.21 ng m−2 d−1 in the accumulation mode, 47 ± 44 ng m−2 d−1 in the first coarse mode, and 37 ± 31 ng m−2 d−1 in the second coarse mode. The present work contributed to the comprehension of the Hg biogeochemical cycle, but further research studies are needed.

Seasonal Variation of Mercury and Its Isotopes in Atmospheric Particles at the Coastal Zhongshan Station, Eastern Antarctica.

Mercury (Hg) is a globally spread trace metal due to its long atmospheric residence time. Yet, our understanding of atmospheric processes (e.g., redox reactions and deposition) driving Hg cycling is still limited, especially in polar regions. The Antarctic continent, by virtue of its remoteness, is the perfect location to investigate Hg atmospheric processes in the absence of significant local anthropogenic impact. Here, we present the first 2 year record (2016-2017) of total suspended particulate mercury (PHg) concentrations along with a year-round determination of an Hg stable isotopic composition in particles collected at Zhongshan Station (ZSS), eastern Antarctic coast. The mean PHg concentration is 21.8 ± 32.1 pg/m3, ranging from 0.9 to 195.6 pg/m3, and peaks in spring and summer. The negative mass-independent fractionation of odd Hg isotopes (odd-MIF, average -0.38 ± 0.12‰ for Δ199Hg) and the slope of Δ199Hg/Δ201Hg with 0.91 ± 0.12 suggest that the springtime isotope variation of PHg is likely caused by in situ photo-oxidation and reduction reactions. On the other hand, the increase of PHg concentrations and the observed odd-MIF values in summer are attributed to the transport by katabatic winds of divalent species derived from the oxidation of elemental Hg in the inland Antarctic Plateau.

Spatiotemporal distribution and long-range transport of atmospheric speciated mercury at three remote islands in Taiwan Strait and South China Sea

This study investigated the spatiotemporal distribution and long-range transport of atmospheric speciated mercury at three remote islands in the Taiwan Strait and the South China Sea. The field measured speciated mercury in the atmosphere was then correlated with criteria air pollutants and meteorological parameters. Air mass trajectory simulation and global fire map were further used to explore potential source regions. Field measurement results showed that the yearly average concentration of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate mercury (PHg) in the target seas were 2.09±0.61 ng/m3, 20.93±7.81 pg/m3, and 150±70 pg/m3, respectively. The highest GEM, GOM, and PHg concentrations were always observed at the Penghu Islands in all seasons. Total gaseous mercury (TGM = GEM+GOM) was the dominant mercury species in the atmosphere, apportioned as 92.46– 96.17% TGM and 3.83– 8.70% PHg, respectively. The seasonal variation of GEM and PHg concentrations were ordered as: spring>winter>fall>summer, while GOM showed different seasonal trends. The lowest concentration of total atmospheric mercury (TAM) was observed in summer since clean air masses were blown mainly from the Pacific Ocean and the Philippines Islands. Air masses came mainly from Central China, North China, and Japan/Korea with the TAM concentrations of 2.90 ± 0.63, 2.68 ± 0.65, and 2.16 ± 0.45 ng/m3, and the frequencies of 19.3%, 18.3%, and 14.3%, respectively. Atmospheric speciated mercury positively correlated to O3, PM2.5, SO2, and NOx, implying that they were consistently emitted from anthropogenic sources in the upwind polluted regions. Overall, the concentrations of atmospheric speciated mercury measured at the three remote islands in the Taiwan Strait and the South China Sea were commonly higher than those in the United States and European countries, but lower than those in Asian countries, with the exception of Japan.

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.

Levels and Sources of Atmospheric Particle-Bound Mercury in Atmospheric Particulate Matter (PM10) at Several Sites of an Atlantic Coastal European Region

Atmospheric particle-bound mercury (PHg) quantification, at a pg m−3 level, has been assessed in particulate matter samples (PM10) at several sites (industrial, urban and sub-urban sites) of Atlantic coastal European region during 13 months by using a direct thermo-desorption method. Analytical method validation was assessed using 1648a and ERM CZ120 reference materials. The limits of detection and quantification were 0.25 pg m−3 and 0.43 pg m−3, respectively. Repeatability of the method was generally below 12.6%. PHg concentrations varied between 1.5–30.8, 1.5–75.3 and 2.27–33.7 pg m−3 at urban, sub-urban and industrial sites, respectively. PHg concentration varied from 7.2 pg m−3 (urban site) to 16.3 pg m−3 (suburban site) during winter season, while PHg concentrations varied from 9.9 pg m−3 (urban site) to 19.3 pg m−3 (suburban site) during the summer. Other trace elements, major ions, black carbon (BC) and UV-absorbing particulate matter (UV PM) was also assessed at several sites. Average concentrations for trace metals (Al, As, Bi, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Si, Sr, V and Zn) ranged from 0.08 ng m−3 (Bi) at suburban site to 1.11 µg m−3 (Fe) at industrial site. Average concentrations for major ions (including Na+, K+, Ca2+, NH4+, Mg2+, Cl−, NO3− and SO42−) ranged from 200 ng m−3 (K+) to 5332 ng m−3 (SO42−) at urban site, 166 ng m−3 (Mg2+) to 4425 ng m−3 (SO42−) at suburban site and 592 ng m−3 (K+) to 5853 ng m−3 (Cl−) at industrial site. Results of univariate analysis and principal component analysis (PCA) suggested crustal, marine and anthropogenic sources of PHg in PM10 at several sites studied. Toxicity prediction of PHg, by using hazard quotient, suggested no non-carcinogenic risk for adults.

Distribution and sources of particulate mercury and other trace elements in PM2.5 and PM10 atop Mount Tai, China

The concentrations of particulate mercury (PHg) and other trace elements in PM2.5 and PM10 in the atmosphere were measured at the summit of Mount Tai during the time period of 15 June – 11 August 2015. The average PHg concentrations were 83.33 ± 119.1 pg/m3 for PM2.5 and 174.92 ± 210.5 pg/m3 for PM10. Average concentrations for other trace elements, including Al, Ca, Fe, K, Mg, Na, Pb, As, Se, Cu, Cd, Cr, V, Mo, Co, Ag, Ba, Mn, Zn and Ni ranged from 0.06 ng/m3 (Ag) to 354.33 ng/m3 (Ca) in PM2.5 and 0.11 ng/m3 (Co) to 592.66 ng/m3 (Ca) in PM10. The average concentrations of PHg were higher than those at other domestic mountain sites and cities in other counties, lower than those at domestic city sites. Other trace elements showed concentrations lower than those at the domestic mountain sites. Due possibly to increased control of emissions and the proportion of new energy, the PHg and trace element concentrations decreased, but the PHg showed concentrations higher than those at the Mountain sites, this showed that the reasons was not only severely affected by anthropogenic emissions, but also associated with other sources. The concentration changed trend of the main trace elements indicated that PHg, trace elements and particle matters present positive correlation and fine particulate matter has a greater surface area which was conductive to adsorption of Hg and trace elements to particles. On June 19, June 27 and July 6, according to the peak of mercury and trace elements, we can predict the potential sources of these three days. The results of principal component analysis (PCA) suggested that, crustal dust, coal combustion, and vehicle emissions were the main emission sources of PHg and other trace elements in Mount Tai. The 24-h backward trajectories and potential source contribution function (PSCF) analysis revealed that air masses arriving at Mount Tai were mainly affected by Shandong province. Mount Tai was subjected to five main airflow trajectories. Clusters 1, 2, 3, and 5 represented four pathways for local and regional sources and cluster 4 originated long-distance transportation. Central Shandong was the main source regions of PHg, Pb, Se, As, Cu and Cd. Southeastern and northwestern Shandong province and northern Jiangsu province were the most polluted source regions of Mn, Zn, and Ni. The crustal elements Fe and Ca had similar distributions of potential source regions, suggested by the highest PSCF values in southeastern Shandong and northern Jiangsu.

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.

How incense and joss paper burning during the worship activities influences ambient mercury concentrations in indoor and outdoor environments of an Asian temple?

This study firstly investigated the species, concentration variation, and emission factors of mercury emitted from the burning of incenses and joss papers in an Asian temple. Both indoor and outdoor speciated mercury (GEM, GOM, and PHg) were sampled by manual samplers, while ambient GEM at an indoor site was in-situ monitored by a continuous GEM monitor. Field measurement results showed that the total atmospheric mercury (TAM) concentrations in indoor and outdoor environments were in the range of 8.03–35.72 and 6.03–31.35 ng/m3, respectively. The indoor and outdoor ratios (I/O) of TAM in the daytime and at nighttime were in the range of 0.64–0.90 and 1.50–2.04, respectively. The concentrations of GEM, GOM, and PHg during the holiday periods were approximately 1–4 times higher than those during the non-holiday periods. GEM was the dominant mercury species in the indoor and outdoor environments and accounted for 63–81% of TAM, while the oxidized mercury accounted for 19–37% of TAM. Burning incenses and joss papers in a combustion chamber showed that the concentration of GEM from joss paper burning ranged from 4.07 to 11.62 μg/m3, or about 13.97 times higher than that of incense burning, while the concentration of PHg from incense burning ranged from 95.91 to 135.07 ng/m3, or about 3.29 times higher than that of joss paper burning. The emission factors of incense burning were 10.39 ng/g of GEM and 1.40 ng/g of PHg, while those of joss paper burning were 12.65 ng/g of GEM and 1.27 ng/g of PHg, respectively. This study revealed that speciated mercury emitted from worship activities had significant influence on the indoor and outdoor mercury concentrations in an Asian temple. Higher intensity of worship activities during holidays resulted in a higher concentration of speciated mercury in indoor and outdoor air, which might cause health threats to worshipers, staffs, and surrounding inhabitants through long-term exposure.

Characteristics and potential sources of atmospheric particulate mercury in Jinan, China

Measurements of atmospheric particulate mercury (PHg) were conducted at a suburban site in Jinan, China from June 2014 to December 2015. The average PHg concentration was 508.5±402.7pgm−3, and the average Hg content in PM2.5 (particles with a diameter of 2.5μm or less) was 6.60±5.82μgg−1. Both PHg and Hg content in PM2.5 aerosols were comparable to levels in some cities in China and were much higher than in cities in North America and Europe. Weak correlations were found between PHg and meteorological parameters. The correlations between PHg and other pollutants in ambient air, including SO2, CO and NOχ, together with their wind dependence were used for source analysis, which suggested coal-fired industries, cement plants and traffic emissions as potential local sources for the site. Cluster analysis of 36-h backward trajectories suggested that the regional transport from southwestern Shandong Province also contributed to PHg in Jinan.

Seasonal variation of atmospheric particulate mercury over the East China Sea, an outflow region of anthropogenic pollutants to the open Pacific Ocean

In this study, PM2.5 and total suspended particulate (TSP) aerosol samples were collected to investigate atmospheric mercury pollution on a pristine island in the East China Sea (ECS) from October 2011 to August 2012. The sampling site is located in the downwind path of the outflow of anthropogenic pollutants from East Asia to the Pacific Ocean, driven by the East Asian monsoon. Average concentrations of particulate mercury (PHg, in pg/m3) were 16.6 for PM2.5 and 24.2 for TSP. Particulate mercury was mainly present in the fine mode, with 68.5% of the total PHg being present in PM2.5. Obvious seasonal variations were observed for both PM2.5 and TSP. The dry deposition flux of PHg over the ECS was estimated to be 1.69 μg m−2 yr−1. Three episodes of high PHg concentrations were observed during the sampling period. An episode in fall (84.1 pg/m3 in TSP) was induced by biomass burning in East China, and PHg was more concentrated in the fine mode (PM2.5/TSP = 0.91). An episode in winter was triggered by serious anthropogenic emissions in northern China, with PHg levels reaching 132.7 pg/m3 in TSP. An episode in spring was attributed to the long-range transport of Asian dust mixed with anthropogenic aerosols, with increased levels of PHg in the coarse mode (PM2.5/TSP = 0.61). Principal component analysis (PCA) indicated that fossil fuel combustion and biomass burning from the Asian mainland were the two major sources of atmospheric PHg over the ECS.

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.

Mercury concentration in fine atmospheric particles during haze and non-haze days in Shanghai, China

Concentrations of fine particulate mercury (PHg), particulate matter ≤2.5 μm (PM2.5), and particulate matter ≤10 μm (PM10) were monitored for the whole year of 2013 in Shanghai, China. The average concentrations of PHg were 1270 ± 716 pg/m3 and 341 ± 187 pg/m3 during haze and non-haze days respectively. The average PHg concentration throughout the whole year 2013 was 642 ± 616pg/m3. It was observed that PHg concentrations on haze days were 3 times higher than on non-haze days. The concentration of PHg on non-haze days in 2013 varied from 0.25 to 0.48 ng/m3. The mean monthly PHg concentration was highest in December (1.92 ng/m3), while the minimum mean concentration was observed in February and August (0.80 ng/m3), and there was a clear seasonal variation: winter (1.67 ng/m3), autumn (1.08 ng/m3), spring (1.02 ng/m3), and summer (1.00 ng/m3) during haze days. The correlation between PHg and PM2.5 was strong (r = 0.96 on haze days; r = 0.90 on non-haze days), while the correlation between PHg and PM10 was weaker (r = 0.85 on haze days; r = 0.57 on non-haze days). The PHg concentration on haze days was always higher than on non-haze days, indicating that haze conditions were accelerating the formation of PHg. The result also indicated that PHg was inclined to combine with fine particles. The existence of strong correlations between the concentrations of PM2.5, PM10, and PHg indicated the commonality of the contributing sources, such as traffic, industrial emissions, and the combustion of coal.

Change characteristic of atmospheric particulate mercury during dust weather of spring in Qingdao, China

Atmospheric aerosol samples were collected during dust weather of spring from 2008 to 2011 in Qingdao, in which the concentrations of atmospheric particulate mercury (PHg) were measured to analyze its distribution characteristics and source. PHg concentration during the study ranged from 0.050 ng m−3 to 0.788 ng m−3 with the average 0.292 ng m−3 in dust day, while 0.085 ng m−3 to 0.444 ng m−3 with the average 0.188 ng m−3 in non-dust day. PHg concentration in dust day is far higher than that in some cities of South Korea and Japan and comparable to some cities in China. There was a statistically power function between PHg/TSP and TSP concentrations, which meant that intense dust (high TSP) brought particles with low mercury content. The estimated dry deposition flux of PHg is 0.9–14.2 ng m−2 h−1 with the mean 5.26 ng m−2 h−1 in dust day. The mercury deposition flux in a dust day accounts for almost 1% annual flux, which should be paid attention in the regional and global cycle of mercury. The trajectories are categorized into 4 sectors. Cluster 1 and cluster 4 were the main routes of dust to Qingdao, coming from Kazakhstan and north of Mongolia individually. There is higher TSP, and lower PHg/TSP in dust of cluster 4 compared with cluster 1, because of longer transport distance and faster movement speed. There is highest PHg/TSP in cluster 2 because of passing polluted East China. The slow transport speed, long stay at polluted developed region caused pollutants to accumulate in the aerosols. Differences of transport route, movement speed affects the mercury content significantly.

Atmospheric mercury speciation and mercury in snow over time at Alert, Canada

Abstract. Ten years of atmospheric mercury speciation data and 14 years of mercury in snow data from Alert, Nunavut, Canada, are examined. The speciation data, collected from 2002 to 2011, includes gaseous elemental mercury (GEM), particulate mercury (PHg) and reactive gaseous mercury (RGM). During the winter-spring period of atmospheric mercury depletion events (AMDEs), when GEM is close to being completely depleted from the air, the concentration of both PHg and RGM rise significantly. During this period, the median concentrations for PHg is 28.2 pgm−3 and RGM is 23.9 pgm−3, from March to June, in comparison to the annual median concentrations of 11.3 and 3.2 pgm−3 for PHg and RGM, respectively. In each of the ten years of sampling, the concentration of PHg increases steadily from January through March and is higher than the concentration of RGM. This pattern begins to change in April when the levels of PHg peak and RGM begin to increase. In May, the high PHg and low RGM concentration regime observed in the early spring undergoes a transition to a regime with higher RGM and much lower PHg concentrations. The higher RGM concentration continues into June. The transition is driven by the atmospheric conditions of air temperature and particle availability. Firstly, a high ratio of the concentrations of PHg to RGM is reported at low temperatures which suggests that oxidized gaseous mercury partitions to available particles to form PHg. Prior to the transition, the median air temperature is −24.8 °C and after the transition the median air temperature is −5.8 °C. Secondly, the high PHg concentrations occur in the spring when high particle concentrations are present. The high particle concentrations are principally due to Arctic haze and sea salts. In the snow, the concentrations of mercury peak in May for all years. Springtime deposition of total mercury to the snow at Alert peaks in May when atmospheric conditions favour higher levels of RGM. Therefore, the conditions in the atmosphere directly impact when the highest amount of mercury will be deposited to the snow during the Arctic spring.

Characterization of mercury in atmospheric particulate matter in the southeast coastal cities of China

Although present in a low concentration in the atmosphere, mercury in particulate matter (PHg) plays an important role in the biogeochemical process of mercury. In this study, the mercury concentrations in three size fractions of airborne particulate matters collected from 14 sites (12 urban sites, 1 rural site and 1 remote site) in the southeast coastal cities of China during different seasons in 2010–2011 were investigated. Most of PHg (46.8–71.9%) was concentrated in the finer particles, i.e. PM2.5 (particulate matter ≤2.5 µm in aerodynamic diameter). The average mercury concentrations in PM2.5 were 141.2±128.1 (range of 7.6–956.5), 37.0±19.2 (5.6–89.4), and 24.0±14.6 (3.2– 59.9) pg m–3 at urban, rural, and remote sites during the whole sampling period, respectively. The PHg concentrations were almost at the same level in spring, autumn, and winter, approximately two times of that in summer. PHg concentrations in the atmosphere displayed a significant spatial variation with far higher values in urban areas than those at rural and remote sites. The dry deposition fluxes of total PHg estimated by a theoretical model were 38.3, 47.7, and 58.7 µg m–2 y–1 at Ji’an (JA), Jimei (JM), and Longwen (LW), respectively. The backward air trajectory analysis revealed that the atmospheric PHg concentrations were mainly influenced by air masses from ocean sources that diluted PHg in summer and on contrary from continental sources in other seasons.

Atmospheric mercury over sea ice during the OASIS-2009 campaign

Abstract. Measurements of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (PHg) were collected on the Beaufort Sea ice near Barrow, Alaska, in March 2009 as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) and OASIS-Canada International Polar Year programmes. These results represent the first atmospheric mercury speciation measurements collected on the sea ice. Concentrations of PHg averaged 393.5 pg m−3 (range 47.1–900.1 pg m−3) and RGM concentrations averaged 30.1 pg m−3 (range 3.5–105.4 pg m−3) during the two-week-long study. The mean concentration of GEM during the study was 0.59 ng m−3 (range 0.01–1.51 ng m−3) and was depleted compared to annual Arctic ambient boundary layer concentrations. It is shown that when ozone (O3) and bromine oxide (BrO) chemistry were active there is a positive linear relationship between GEM and O3, a negative one between PHg and O3, a positive correlation between RGM and BrO, and none between RGM and O3. For the first time, GEM was measured simultaneously over the tundra and the sea ice. The results show a significant difference in the magnitude of the emission of GEM from the two locations, with significantly higher emission over the tundra. Elevated chloride levels in snow over sea ice are proposed to be the cause of lower GEM emissions over the sea ice because chloride has been shown to suppress photoreduction processes of RGM to GEM in snow. Since the snowpack on sea ice retains more mercury than inland snow, current models of the Arctic mercury cycle may greatly underestimate atmospheric deposition fluxes because they are based predominantly on land-based measurements. Land-based measurements of atmospheric mercury deposition may also underestimate the impacts of sea ice changes on the mercury cycle in the Arctic. The predicted changes in sea ice conditions and a more saline future snowpack in the Arctic could enhance retention of atmospherically deposited mercury and increase the amount of mercury entering the Arctic Ocean and coastal ecosystems.