Atmospheric Mercury Species Research Articles

Intercomparison of methods for atmospheric reactive mercury observations: Evidences to interpret what we are actually measuring

Accurate measurements of atmospheric reactive mercury (RM or HgII) including gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM) are crucial to improving understanding of mercury (Hg) behavior in the ambient air and evaluating the effectiveness of the Minamata Convention. As part of the Speciation and Transformation of Atmospheric Mercury in a Polluted region (STAMP) campaign in eastern China, comparison of Tekran, the reactive mercury active system (RMAS) and the micro-orifice uniform deposit impactors (MOUDI) system for RM measurements was conducted in this study. The ratio of GOMTekran/GOMRMAS was found to be positively correlated with the ratio of PBM/GOM and the proportion of [-Br/Cl] in RM based on deconvolution of the RMAS thermal desorption profiles. HgII reduction by the aqueous HO2 radicals was found to be the most likely cause of GOM underestimation by denuder-based methods. PBM acting as a substitute for GOM in HgII reduction could limit the underestimation. High particulate matter (PM) environment could cause PBM breakthrough in RMAS sampling, resulting in PBM underestimation and GOM overestimation. The chemical compound characteristics of RM and HgII distribution on particles by size provide evidences for the sources of the discrepancies in PBM measurements by different methods. Particle-size-resolved compound profiles are useful approaches for accurate RM quantification.

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 Isotope Composition in Open Water Corals of South China Sea: Implication for Atmospheric Mercury Deposition Pathways Into Tropical Oceans

AbstractThe deposition of different atmospheric mercury (Hg) species into oceans determines the atmospheric Hg lifetime and the production of neurotoxin methylmercury. Yet, the relative contribution of atmospheric Hg(II) and Hg(0) is largely unconstrained. Here, we report the concentrations of total Hg and methylmercury, as well as Hg isotope composition in living corals collected from the tropical South China Sea (SCS). The results show that the Hg in corals is mainly present as inorganic Hg, exhibiting slightly negative δ202Hg and small yet significant Δ199Hg and Δ200Hg. These isotope features closely resemble those of pelagic waters, suggesting that shallow‐water corals that are widely distributed in oligotrophic waters could be used to trace atmospheric Hg deposition pathways. A mixture model based on coral Δ200Hg indicates that approximately 49% of the seawater Hg in the tropical SCS, a region characterized by high rainfall, originates from atmospheric gaseous Hg(0), much larger than previous estimates.

Spatiotemporal variation and inter-transport of atmospheric speciated mercury between Kaohsiung Harbor and neighboring urban areas

This study investigated the spatiotemporal variation, gas-particle partition, and source resolution of atmospheric speciation mercury (ASM) in Kaohsiung Harbor and neighboring Metro Kaohsiung. Four sampling sites were selected to determine the pollution characteristics and inter-transport of ASM between the port and urban areas. The yearly average GEM, GOM, and PBM concentrations were 7.13 ± 2.2 ng/m3, 331 ± 190 pg/m3, and 532 ± 301 pg/m3, respectively. Notably, GEM emerged as the predominant ASM species (85–94%), primarily originating from anthropogenic emissions from the harbor area and nearby industrial complex. The study revealed a distinct seasonal variation in ASM concentrations in the Kaohsiung Area in the following order: winter > fall > spring > summer. Concerning spatial distribution, ASM concentrations in the port areas were generally higher than those in the urban areas. This disparity was chiefly attributed to the influence of the prevailing winds, local sources, and atmospheric dispersion. Backward trajectory simulation revealed that polluted air masses blown from the northeast in winter and spring, moving along the western in-land part of Taiwan Island, were likely influenced by local sources and long-range transport (LRT). In summer, air pollutants originating from the south were likely transported from the coastal industrial sources. During fall, air masses blown from the western offshore waters transported air pollutants from Kaohsiung Harbor to neighboring Metro Kaohsiung. The results obtained from principle component analysis (PCA) indicated that primary sources in the port areas included ship emissions, vehicular exhausts, and nearby industrial complex, which align with the primary source factors identified by positive matrix factorization (PMF), which were mobile sources and coal-fired industrial boilers. Meanwhile, mobile sources and sulfur-containing fuel/waste combustion were identified as the primary sources in the urban areas.

Interaction of reactive mercury with surfaces and implications for atmospheric mercury speciation measurements

Accurate measurement of atmospheric reactive mercury (RM) presents analytical challenges due to its reactivity and ultra-trace concentrations. In the last decade, use of the University of Nevada, Reno – Reactive Mercury Active System (RMAS) for RM measurements has increased, since it has been shown to be more accurate than the industry standard, the Tekran 2537/1130/1135 system. However, RMAS measurements also have limitations, including long time resolution and sampling biases associated with membranes used for RM sampling. We therefore investigated the use of higher sampling flow rates to reduce sampling time and tested alternative membrane materials using both ambient air sampling and controlled laboratory experiments with a gaseous oxidized mercury (GOM) calibrator. Results indicated that increasing the RMAS sampling flow had a negative impact on determined RM concentrations. RM concentrations at 2 L min−1 were 10% and 30–50% lower than at 1 L min−1 in spring/summer and winter, respectively. However, the chemical composition of RM captured on membranes was not impacted by the increased flow rate. Membranes currently used in the RMAS performed better than numerous alternatives with similar composition, retaining Hg more efficiently. Both ambient air sampling and laboratory experiments revealed that membranes designed to retain only particulate-bound mercury (PBM) also retained significant amounts of GOM. PBM membranes based on borosilicate glass designs retained more than 70% of GOM.

The Interrelated Pollution Characteristics of Atmospheric Speciated Mercury and Water-Soluble Inorganic Ions in Ningbo, China

Atmospheric mercury and water-soluble inorganic ions (WSIIs) are commonly observable airborne pollutants in the atmosphere that may have similar emission sources. In this study, the interrelated pollution characteristics of atmospheric speciated mercury and WSIIs were studied using a Piper diagram, correlation analysis, pollution episode analysis and potential source contribution function (PSCF) techniques. Also, an empirical regression equation for predicting the temporal variation in gaseous elemental mercury (GEM) was constructed. The results showed that the concentrations of GEM and particle-bound mercury (PBM) roughly increased with the increasing percentage values of NH4+ in cationic normality, and exponentially increased with the decreasing percentage values of Na+ + Mg2+ in cationic normality. Correlation analysis revealed that the atmospheric speciated mercury was positively (p < 0.01) correlated with most water-soluble inorganic ions, especially for GEM, which was closely correlated with NO2, NOx, CO, PM2.5, NO3− SO42−, NH4+ and K+ (r > 0.5, p < 0.01), indicating that the emission sources of GEM were related to fossil fuel and biomass combustion, industrial activities, and traffic exhausts. Pollution episode analysis showed that PM2.5, WSIIs (including SO42−, NO3−, NH4+, K+ and Cl−), SO2 and NO2 generally exhibited synchronous variations with GEM and PBM, and positive correlations were observed between GEM and PM2.5, SO42−, NO3−, NH4+, K+, Cl−, SO2 and NO2 (r = 0.35–0.74, p-value < 0.01). In addition, the potential source region of GEM was similar to that of PM2.5, SO42−, NO3−, NH4+, K+ and Ca2+. Based on the above findings, a satisfactory empirical regression equation, with PM2.5, NOx, CO and the percentage value of Na+ + Mg2+ in cationic normality as independent variables for GEM simulation, was constructed. The result showed that the variation in GEM concentrations could be predicted well by these variables. This model could serve as a potential substitute tool for GEM measurement in the future.

Atmospheric mercury speciation and concentration at the urban and industrial sites in Taiwan over a three-year period

Mercury (Hg) is a toxic metal known to be detrimental to human health and wildlife survival due to its serious toxicity to the central nervous system. In this study, measurements of atmospheric mercury in Taiwan over three years suggested significantly higher total Hg concentrations (p < 0.001) during the dry season compared with the wet season for both urban and industrial sites, indicating that precipitation played a role through scavenging Hg. Total gaseous mercury (TGM) was the main component in air accounting for >90% of the total Hg, which included particulate mercury (Hgp). Furthermore, extreme Hg concentrations were observed at sites near cement works (TGM: 18 ng m−3; Hgp: 913 pg m−3) and iron-steel plants (TGM: 24.3 ng m−3; Hgp: 871 pg m−3), indicating a strong role for these two stationary emission sources to Hg concentrations in ambient air. This study contributes to improved understanding of atmospheric mercury speciation and concentrations near iron-steel plants and cement works.

Unexpectedly high concentrations of atmospheric mercury species in Lhasa, the largest city in the Tibetan Plateau

Abstract. The city of Lhasa is located in the central Tibetan Plateau and is the most densely populated area. As the first continuous monitoring of atmospheric mercury (Hg) species in a city in the Tibetan Plateau, our monitoring in Lhasa showed that the concentrations of gaseous elemental Hg (GEM), gaseous oxidized Hg (GOM), and particle-bound Hg (PBM) during the subsequent Indian summer monsoon (S-ISM) period were 2.73 ± 1.48 ng m−3, 38.4 ± 62.7 pg m−3, and 59.1 ± 181.0 pg m−3, respectively. During the westerly circulation (WEC) period, the GEM, GOM, and PBM concentrations were 2.11 ± 2.09 ng m−3, 35.8 ± 43.3 pg m−3, and 52.9 ± 90.1 pg m−3, respectively. The GOM and PBM concentrations were higher than those of previous monitoring in the Tibetan Plateau and other provincial capitals in China. Typical high-value occurrence processes were studied to investigate random events with high atmospheric Hg concentrations in Lhasa. Combustion events nearby or further away may be the main contributor of the high-concentration events. The lowest GEM concentrations occurred in the afternoon, and persistently high concentrations were observed at night. The changes in GEM concentrations were consistent with the trends of other pollutant concentrations and contradictory to those of the wind speed. The high GEM concentrations at night can be attributed to the lower boundary layer height and lower wind speed. For both GOM and PBM, higher GOM concentrations occurred during the day and PBM during the night. The results of the principal component analysis indicated that local sources and wind speed are important factors influencing atmospheric Hg concentrations in Lhasa. The trajectory simulation showed that the source of the GEM in Lhasa gradually shifted from the south to the west of Lhasa from the S-ISM to the WEC periods, while both the southern and western sources were important in the late WEC period. The concentrations and change patterns of Hg species in Lhasa were significantly different than those at other monitoring sites in the Tibetan Plateau. Monitoring Hg species in Lhasa shows the possible maximum anthropogenic influences in the Tibetan Plateau and demonstrates the dramatic effect of wind on changes in urban atmospheric Hg concentrations.

Long-range transport of atmospheric speciated mercury from the eastern waters of Taiwan Island to northern South China Sea

This study explored the temporospatial distribution, gas-particle partition, and pollution sources of atmospheric speciated mercury (ASM) from the eastern offshore waters of the Taiwan Island (TI) to the northern South China Sea (SCS). Both gaseous and particulate mercury were simultaneously sampled at three remote sites in four seasons. The average concentrations of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate bound mercury (PBM) were 2.05 ± 0.45 ng/m3, 19.17 ± 5.39 pg/m3, and 0.11 ± 0.06 ng/m3, respectively. The concentrations of GEM and PBM in the cold seasons were higher than those in the warm seasons, but those of GOM had an opposite trend. In terms of gas-solid partition, ASM was apportioned as 91.3–97.3% of GEM and 2.7–8.7% of GOM and PBM. The average concentrations of GEM, GOM, and PBM at the Green Island (GI) were 2.21 ± 0.47 ng/m3, 22.31 ± 5.35 pg/m3, and 0.12 ± 0.06 ng/m3; those at the Kenting Peninsula (KT) were 2.11 ± 0.43 ng/m3, 20.57 ± 4.38 pg/m3, and 0.11 ± 0.06 ng/m3; and those at the Dongsha Islands (DS) were 1.84 ± 0.40 ng/m3, 15.19 ± 3.58 pg/m3, and 0.08 ± 0.05 ng/m3, respectively. Overall, the spatial distribution of ASM concentrations showed the order as: GI > KT > DS. Air masses blown mainly from the West Pacific Ocean (WPO) and SCS in summer showed the lowest ASM concentrations. Oppositely, high ASM concentrations were commonly observed in spring and winter when polluted air masses were blown by Asian Northeastern Monsoons (ANMs). The transport routes of polluted air masses were originated mainly from North China, Central China, Northeast China, Korea and Japan, and mostly passed through the urban and industrial regions in the northeastern Asian countries.

A Review of Dry Deposition Schemes for Speciated Atmospheric Mercury

This study reviewed the existing framework of dry deposition schemes for speciated atmospheric mercury. As the most commonly used methods for mercury dry deposition estimation, the big-leaf resistance scheme for gaseous oxidized mercury (GOM), the size distribution regarded resistance scheme for particulate bound mercury (PBM), and the bidirectional air-surface exchange scheme for gaseous elemental mercury (GEM) were introduced in detail. Sensitivity analysis were conducted to quantitatively identify the key parameters for the estimation of speciated mercury dry deposition velocities. The dry deposition velocity of GOM was found to be sensitive to the wind speed and some land use related parameters. The chemical forms of GOM could have a significant impact on the dry deposition velocity. The dry deposition velocity of PBM is sensitive to the mass fraction of PBM in coarse particles, while that of GEM is most sensitive to air temperature. Future research needs were proposed accordingly.

Chemical significance of atmospheric mercury at fishing port compared to urban and suburb in an offshore island

This study explored the chemical significance, spatiotemporal variation, and source origins of atmospheric speciated mercury (ASM) at three contexts (urban, suburb, and fishing port) at the Penghu Islands in the Taiwan Strait. Continuous monitoring of 5-min total gaseous mercury (TGM) was used to determine its hourly, daily, and seasonal concentrations. Manual sampling of 12-h gaseous oxidixed mercury (GOM) and particulate bound mercury (PBM) was used to resolve their diurnal and seasonal variation. ASM further correlated with meteorological parameters and criteria air pollutants. Backward trajectories coped with regional fire maps to identify the potential sources of atmospheric mercury. The yearly mean TGM concentration was about 2.9 times higher than the background level (1.4 ng/m3) of Northern Hemisphere. The highest and lowest seasonal TGM concentration appeared in spring and summer, respectively. Asian continental outflows (ACOs) containing mercury-laden contaminants (MLCs) in spring, while polluted air masses were blown from southern Taiwan where heavily industrial complex had in summer, causing the second highest ASM level. In fall, MLCs emitted from the coastal industrial and urban areas were blown from the Korea Peninsula by Asian Northeastern Monsoons (ANMs). In terms of gas-particle partition, TGM was superior to PBM. Moreover, the highest TGM concentration was observed at the fishing port site, and followed by the suburb and urban sites. High TGM concentration peaks were regularly observed at the fishing port site due to the exhausts of fishing boats.

Elevated Gaseous Oxidized Mercury Revealed by a Newly Developed Speciated Atmospheric Mercury Monitoring System.

Gaseous oxidized mercury (Hg2+) monitoring is one of the largest challenges in the mercury research field, where existing methods cannot simultaneously satisfy the measurement requirements of both accuracy and time precision, especially in high-particulate environments. Here, we verified that dual-stage cation exchange membrane (CEM) sampler is incapable of gaseous elemental mercury (Hg0) uptake even if particulate matter is trapped on CEM, whereas the Hg2+ capture efficiency of the sampler is more than 90%. We then developed a Cation Exchange Membrane-Coupled Speciated Atmospheric Mercury Monitoring System (CSAMS) by coupling the dual-stage CEM sampler with the commercial Tekran 2537/1130/1135 system and configuring a new sampling and analysis procedure, so as to improve the monitoring accuracy of Hg2+ and ensure the simultaneous measurement of Hg0, Hg2+, and Hgp in 2 h time resolution. We deployed the CSAMS in urban Beijing in September 2021 and observed an unprecedented elevated Hg2+ during the daytime with an average amplitude of 510 pg m-3. Using a zero-dimensional box model, the elevated Hg2+ production rate was attributed to high atmospheric oxidant concentrations, Hg0 heterogeneous and interfacial oxidation processes on the surface of atmospheric particles, or potential unknown oxidants.

Seasonal variation and source identification of atmospheric speciated mercury in an industrial harbor area in East Asia

In this study, the pollution characteristics, spatiotemporal variation, and potential sources of atmospheric speciated mercury (ASM) in an industrial harbor area were explored. Gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle-bound mercury (PBM) were sampled by a self-designed manual system at three harbor sites in four seasons. The yearly average concentrations of GEM, GOM, and PBM were 6.7 ± 2.0 ng/m3, 244 ± 70 pg/m3, and 410 ± 105 pg/m3, respectively. The seasonal average ASM concentration was in the order of: winter > fall > spring > summer. In terms of species, GEM dominated ASM, while reactive mercury (RM = GOM + PBM) accounted for 6.0–15.7%of ASM, implying that ASM was governed by anthropogenic sources in the harbor area. The highest ASM concentrations were observed at Site Zhonghe (ZH), which is mainly influenced by both ship exhausts and industrial emissions, and positively correlated with CO, NOx, and SO2. In particular, GOM was positively correlated with O3, and negatively correlated with air temperature and relative humidity, showing high impact from atmospheric photochemical reactions. Air masses transporting westerly in spring were mainly from ship exhausts. In summer, air masses transporting from the south were from utility power plants and machinery exhausts. In fall and winter, air masses were transported mainly from the north, blowing by the long-range transport of polluted air masses originated from the north. Both principal component analysis and positive matrix factorization results indicate that coal burning, industrial emissions, and vehicular exhausts are the main contributors to ASM. Site Zhongdao (ZD) was close to the bulk carrier loading and unloading zones and was highly influenced by mobile sources, while Site ZH was mainly influenced by the neighboring industrial complex.

Temporal variation of speciated atmospheric Hg and characteristics of size-fractioned HgP at a suburban site in Shijiazhuang City, North China

Atmospheric mercury (Hg) species were determined at a suburban site near Shijiazhuang, China from May 2016 to January 2017 to ascertain their seasonal and diurnal patterns, to identify the relationship with other parameters, and furthermore to elucidate their potential sources areas. The gaseous elemental Hg (GEM) concentration (3.66 ± 2.62 ng m−3) was about 2 times higher than the background level in the Northern Hemisphere, and the fine particulate bound Hg (HgP2.5) concentration (92.4 ± 59.6 pg m−3) was comparable to those at urban sites, while the gaseous oxidized Hg (GOM) level was quite low (5.7 ± 5.6 pg m−3). GEM and HgP2.5 concentrations exhibit pronounced seasonal (January > May > October > August) and diurnal (nighttime > daytime) patterns. In contrast, the seasonal and diurnal patterns of GOM were just opposite to those of GEM and HgP2.5. The significant positive relationship among GEM, HgP, CO, SO2, and NO2 reveals that they have similar anthropogenic sources. Interestingly, the size distributions of HgP in PM10 were observed to be unimodal during the four study periods, and peaks were all located in the fine mode (0.7–2.1 μm), and fine HgP contributed ∼70% (38.2–81.5%) of HgP10, indicating that the fine mode was the dominant size. The potential source contribution function (PSCF) result suggests that GEM level at the sampling site was highly impacted by regional sources rather than the long-range transport, and the potential source areas were predominantly located in southern Hebei and western Shandong. The results of wind rose and cluster analyses were consistent with the PSCF results.

Behavior of KCl sorbent traps and KCl trapping solutions used for atmospheric mercury speciation: stability and specificity

Abstract. Atmospheric mercury speciation is of paramount importance for understanding the behavior of mercury once it is emitted into the atmosphere as gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM). GOM and PBM can also be formed in the atmosphere; their sampling is the most problematic step in the atmospheric mercury speciation. GOM sampling with speciation traps composed of KCl sorbent materials and KCl trapping solutions are commonly used sampling methods, although the research conducted with them at ambient air concentrations is limited. The results of the specificity test demonstrated that the KCl sorbent traps are highly specific when using new traps, while their specificity drops dramatically when they are reused. The results of the stability test indicated that the highest Hg2+ losses (up to 5.5 % of Hg2+ loss) occur when low amounts of Hg2+ (&lt; 1 ng) are loaded, due to a reduction of Hg2+ to Hg0. KCl trapping solutions have also been considered as a selective trapping media for GOM in atmospheric samples. A dimensionless Henry law constant was experimentally derived and was used to calculate the solubility of elemental Hg in KCl solution. The degree of GEM oxidation was established by purging elemental Hg calibration gas into a KCl solution and determining the GOM trapped using aqueous-phase propylation liquid–liquid extraction and gas chromatography–atomic fluorescence spectrometry (GC-AFS) measurement. A positive GOM bias was observed due to the solubility and oxidation of GEM in KCl trapping solutions, strongly suggesting that this approach is unsuitable for atmospheric mercury speciation measurements.

Spatial Distribution of Atmospheric Mercury Species in the Southern Ocean

AbstractAntarctica and the surrounding Southern Ocean act as an important sink in the global mercury cycle; however, corresponding studies of atmospheric mercury species in these regions are still scarce. Here, we report large‐scale observations of atmospheric gaseous elemental mercury (GEM) and gaseous oxidized mercury (GOM) in the Antarctic marine boundary layer (MBL) taken during a summer cruise. There is large variability in the spatial distribution of GOM, which is likely attributable to the diverse land surface types, including coastal Antarctica, sea‐ice region, and oceanic region, along the cruise route. In coastal Antarctica, the highest GOM level (56.23 ± 47.74 pg·m−3) might be attributed to the significant in‐situ oxidation there. Significant in‐situ oxidation of GEM could also occur in the sea‐ice region, causing the significant increase of GOM (up to 87.01 pg·m−3), while the uptake of the high content of sea‐salt aerosols in sea‐ice regions might efficiently eliminate GOM in the air, resulting in generally lower content of GOM (13.10 ± 14.48 pg·m−3) in the sea‐ice region. In the oceanic region, the lowest level of GOM (3.95 ± 4.69 pg·m−3) is due to both the uptake of sea‐salt aerosols and the seasonal melting of first‐year sea‐ice. This study provides insight to understand the mechanisms of the atmospheric mercury cycle in various land surface types in the Antarctic MBL.

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.

Long‐term ecosystem monitoring at Huntington Forest: Integrating hydrology, biogeochemistry and climatic controls on watershed processes

AbstractLocated in the Adirondack Mountains of northern New York State, Huntington Wildlife Forest (HWF) is a 6000‐ha research and education facility operated by SUNY ESF (State University of New York, College of Environmental Science and Forestry) with continuous long‐term monitoring (LTM) programs spanning over six decades. One of the ‘cradles’ of acid rain research in North America, HWF was in the first cohort of National Atmospheric Deposition Program (NADP) sites beginning in 1978. HWF is currently the only location (NY‐20) in New York with the full suite of NADP programs in operation, including atmospheric mercury speciation (AMNet), along with EPA CASTNET. Nearby to NY‐20 at HWF, Arbutus Lake and its forested watershed have been the focus of intensive LTM since installation of v‐notch weirs at the lake outlet and inlet in 1991 and 1994, respectively. Discharge at these locations has been monitored continuously at 15‐min intervals since 1999. Lake outlet water chemistry samples were collected starting in 1983. Weekly sampling of water chemistry at both weirs began in 1995 and was expanded to include two headwater streams and groundwater wells in 2007. More recently, LTM programs at HWF have been augmented by participation in the PhenoCam Network since 2008, collection of high‐resolution LiDAR in 2009, and installation of a precision NY Mesonet weather station in 2016. In 2018, we installed sensor networks that continuously monitor soil microclimate and snow depth. Lastly, we improved data access via a new website (www.adk-ltm.org) where users can create custom queries and visualize outputs.

Temporal variation and potential origins of atmospheric speciated mercury at a remote island in South China Sea based on two-year field measurement data

This study explored the temporal variation, gas-particle partition, and potential origins of atmospheric speciated mercury at a remote island in the South China Sea. Two-year data of three mercury species was measured at the Taiping Island. Air masses were clustered into five transport routes (A-E) to resolve the potential origins of atmospheric mercury. Field measurement showed that the concentration of gaseous elemental mercury (GEM) (1.33 ± 0.52 ng/m3) was close to the GEM background level of Northern Hemisphere, while those of GOM and PHg were 13.39 ± 3.58 and 94.33 ± 30.25 pg/m3, respectively. Both regular and intensive samplings concluded a consistent trend of higher mercury level in winter and spring than that in summer and fall. GEM dominated atmospheric mercury in all seasons (86.2–98.5%), while the highest partition of particle-bound mercury (PHg) was observed in winter (13.8%). The highest GEM concentrations were observed for Route A originating from central China and western Taiwan Island, and followed by Routes D and E from the Philippines, Malaysia, and Indonesia, while the lowest concentrations of GEM were observed for Routes B and C originating from North China, Korea, and Japan. Most importantly, high correlation of GEM versus levoglucosan and K+ in PM2.5 (r = 0.764 and 0.758, p < 0.01) confirmed that GEM was mainly emitted from biomass burning sources at the surrounding countries.

Exploratory investigation on spatiotemporal variation and source identification of atmospheric speciated mercury surrounding the Taiwan Strait

This pioneering study explored the spatiotemporal variation, gas-solid partition, and potential sources of atmospheric speciated mercury surrounding the Taiwan Strait. Total gaseous mercury (TGM) and particle bound mercury (Hgp) were sampled simultaneously at six coastal and island sites located on both sides and in the middle of the Taiwan Strait. Field measurement results showed that the campaign average concentrations of TGM and Hgp at all sites were 4.56 ± 0.35 and 0.17 ± 0.02 ng/m3, with the range of 3.22–5.84 and 0.06–0.25 ng/m3, indicating that TGM and Hgp partitioned as 96.09–97.02% and 2.98–3.91%, respectively, The spatial distribution results showed that the highest and lowest TGM and Hgp concentrations were mostly observed at Xiang-An site in the suburban of Xiamen City and at Sandiaojiao site in the remote coast of New Taipei City, respectively. The seasonal variation of TGM at six sampling sites was in the order as: spring > winter > fall > summer, while that of Hgp was in the order as: winter > spring > fall > summer. Regarding the levels of TGM and Hgp, they increased gradually and consistantly from late fall to early spring when polluted air masses were transported from the Northeast Asia to the Taiwan Strait by Asian Northeastern Monsoons (ANEMs). On the contrary, the lowest concentrations of TGM and Hgp were observed commonly in summer as clean marine air masses transported from the seas toward the Taiwan Strait. It was inferred that atmospheric speciated mercury surrounding the Taiwan Strait was mainly attributed from both local sources and long-range trasport (LRT) from the Northeast Asia.