scholarly journals Speciated atmospheric mercury on haze and non-haze days in an inland city in China

2016 ◽  
Vol 16 (21) ◽  
pp. 13807-13821 ◽  
Author(s):  
Qianqian Hong ◽  
Zhouqing Xie ◽  
Cheng Liu ◽  
Feiyue Wang ◽  
Pinhua Xie ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Central China ◽  
Photochemical Oxidation ◽  
Model Calculations ◽  
Enhanced Production ◽  
Haze Pollution ◽  
The Mean ◽  
Haze Days

Abstract. Long-term continuous measurements of speciated atmospheric mercury were conducted from July 2013 to June 2014 in Hefei, a midlatitude inland city in eastern central China that experiences frequent haze pollution. The mean concentrations (±standard deviation) of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particle-bound mercury (PBM) were 3.95 ± 1.93 ng m−3, 2.49 ± 2.41 and 23.3 ± 90.8 pg m−3, respectively, on non-haze days, and 4.74 ± 1.62 ng m−3, 4.32 ± 8.36 and 60.2 ± 131.4 pg m−3, respectively, on haze days. Potential source contribution function (PSCF) analysis suggested that atmospheric mercury pollution on haze days was caused primarily by local emissions, instead of via long-range transport. The poorer mixing conditions on haze days also favored the accumulation of atmospheric mercury. Compared to GEM and GOM, PBM was especially sensitive to haze pollution. The mean PBM concentration on haze days was 2.5 times that on non-haze days due to elevated concentrations of particulate matter. PBM also showed a clear seasonal trend; its concentration was the highest in fall and winter, decreased rapidly in spring and was the lowest in summer, following the same order in the frequency of haze days in different seasons. On both non-haze and haze days, GOM concentrations remained low at night, but increased rapidly just before sunrise, which could be due to diurnal variation in air exchange between the boundary layer and free troposphere. However, non-haze and haze days showed different trends in daytime GEM and GOM concentrations. On non-haze days, GEM and GOM declined synchronously through the afternoon, probably due to the retreat of the free tropospheric air as the height of the atmospheric boundary layer increases. In contrast, on haze days, GOM and GEM showed opposite trends with the highest GOM and lowest GEM observed in the afternoon, suggesting the occurrence of photochemical oxidation. This is supported by simple box-model calculations, which showed that oxidation of GEM to GOM does occur and that the transport of free tropospheric GOM alone is not large enough to account for the observed increase in daytime GOM. Our results further postulate that NO2 aggregation with the HgOH intermediate may be a potential mechanism for the enhanced production of GOM during daytime.

scholarly journals Speciated Atmospheric Mercury during Haze and Non-haze Days in an Inland City in China

2016 ◽  
Author(s):  
Qianqian Hong ◽  
Zhouqing Xie ◽  
Cheng Liu ◽  
Feiyue Wang ◽  
Pinhua Xie ◽  
...  
Keyword(s):  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Central China ◽  
Mercury Emissions ◽  
Gaseous Elemental Mercury ◽  
Enhanced Production ◽  
Mercury Transport ◽  
Haze Pollution ◽  
The Mean ◽  
Haze Days

Abstract. Long-term continuous measurements of speciated atmospheric mercury were conducted at Hefei, a mid-latitude inland city in east central China, from July 2013 to June 2014. The mean concentrations (± standard deviation) of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particle-bound mercury (PBM) were 3.95 ± 1.93 ng m−3, 2.49 ± 2.41 pg m−3 and 23.3 ± 90.8 pg m−3, respectively, during non-haze days, and 4.74 ± 1.62 ng m−3, 4.32 ± 8.36 pg m−3 and 60.2 ± 131.4 pg m−3, respectively, during haze days. Potential source contribution function (PSCF) analysis suggested that the atmospheric mercury pollution during haze days was caused primarily by local mercury emissions, instead of via long-range mercury transport. In addition, the disadvantageous diffussion during haze days will also enhance the level of atmospheric mercury. Compared to the GEM and RGM, change in PBM was more sensitive to the haze pollution. The mean PBM concentration during haze days was 2.5 times that during non-haze days due to elevated concentrations of particulate matter. A remarkable seasonal trend in PBM was observed with concentration decreasing in the following order in response to the frequency of haze days: autumn, winter, spring, summer. A distinct diurnal relationship was found between GEM and RGM during haze days, with the peak values of RGM coinciding with the decline in GEM. Using HgOH as an intermediate product during GEM oxidation, our results suggest that NO2 aggregation with HgOH could explain the enhanced production of RGM during the daytime in haze days. Increasing level of NOx will potentially accelerate the oxidation of GEM despite the decrease of solar radiation.

scholarly journals Enhanced production of oxidised mercury over the tropical Pacific Ocean: a key missing oxidation pathway

2013 ◽  
Vol 13 (8) ◽  
pp. 21541-21572
Author(s):  
F. Wang ◽  
A. Saiz-Lopez ◽  
A. S. Mahajan ◽  
J. C. Gómez Martín ◽  
D. Armstrong ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Thermal Dissociation ◽  
Oxidation Mechanism ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Mercury Oxidation ◽  
Enhanced Production ◽  
Daily Variability

Abstract. Mercury is a contaminant of global concern. It is transported in the atmosphere primarily as gaseous elemental mercury, but its reactivity and deposition to the surface environment, through which it enters the aquatic food chain, is greatly enhanced following oxidation. Measurements of oxidised mercury in the polar to sub-tropical marine boundary layer have suggested that photolytically produced bromine atoms are the primary oxidant of mercury. We report year-round measurements of elemental and oxidised mercury, along with ozone, halogen oxides (IO and BrO) and nitrogen oxides (NO2), in the marine boundary layer over the Galápagos Islands in the Equatorial Pacific. Elemental mercury concentration remained low throughout the year, while considerable concentrations of oxidised mercury occurred around midday. Our results show that the production of oxidised mercury in the tropical marine boundary layer cannot be accounted for by only bromine oxidation, or by the inclusion of ozone and hydroxyl. A two-step oxidation mechanism where the HgBr intermediate is further oxidised to Hg(II) depends critically on the stability of HgBr. If the current paradigm is considered, another oxidant is needed to explain more than 50% of the observed oxidised mercury. We show that atomic iodine could play the role of the missing oxidant, explaining not only the Hg(II) levels observed, but also the daily variability. However, more recent theoretical calculations indicate that the thermal dissociation rate of HgBr is much faster, by an order of magnitude, than previously reported, which implies that only trace gases at relatively high mixing ratios forming stable complexes with HgBr (such as HO2 and NO2) could compete to generate levels of Hg(II) similar to those observed in our study. Nevertheless, the daily variability of oxidised mercury is not well accounted for by using these new theoretically estimated rates. Furthermore, correlation analysis does not support a major role of NO2 or HO2. We conclude that the key pathway that significantly enhances atmospheric mercury oxidation and deposition to the tropical oceans is missing from the current understanding of atmospheric mercury oxidation.

scholarly journals Observation and analysis of speciated atmospheric mercury in Shangri-La, Tibetan Plateau, China

2015 ◽  
Vol 15 (2) ◽  
pp. 653-665 ◽  
Author(s):  
H. Zhang ◽  
X. W. Fu ◽  
C.-J. Lin ◽  
X. Wang ◽  
X. B. Feng
Keyword(s):  
Tibetan Plateau ◽  
Atmospheric Transport ◽  
Seasonal Pattern ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Back Trajectories ◽  
Gaseous Elemental Mercury ◽  
Northern India ◽  
Wet Scavenging ◽  
The Mean

Abstract. This study reports the concentrations and potential sources of speciated atmospheric mercury at the Shangri-La Atmosphere Watch Regional Station (SAWRS), a pristine high-altitude site (3580 m a.s.l.) in Tibetan Plateau, China. Total gaseous mercury (TGM, defined as the sum of gaseous elemental mercury, GEM, and gaseous oxidized mercury, GOM), GOM and particulate-bound mercury (PBM) were monitored from November 2009 to November 2010 to investigate the characteristics and potential influence of the Indian summer monsoon (ISM) and the Westerlies on atmospheric transport of mercury. The mean concentrations (± standard deviation) of TGM, PBM and GOM were 2.55 ± 0.73 ng m−3, 38.82 ± 31.26 pg m−3 and 8.22 ± 7.90 pg m−3, respectively. A notable seasonal pattern of TGM concentrations was observed with higher concentrations at the beginning and the end of the ISM season. High TGM concentrations (> 2.5 ng m−3) were associated with the transport of dry air that carried regional anthropogenic emissions from both Chinese domestic and foreign (e.g., Myanmar, Bay of Bengal, and northern India) sources based on analysis of HYSPLIT4 back trajectories. Somewhat lower PBM and GOM levels during the ISM period were attributed to the enhanced wet scavenging. The high GOM and PBM were likely caused by local photo-chemical transformation under low RH and the domestic biofuel burning in cold seasons.

scholarly journals Oxidation pathways and emission sources of atmospheric particulate nitrate in Seoul: based on δ<sup>15</sup>N and Δ <sup>17</sup>O of PM<sub>2.5</sub>

2021 ◽  
Author(s):  
Saehee Lim ◽  
Meehye Lee ◽  
Joel Savarino ◽  
Paolo Laj
Keyword(s):  
Critical Role ◽  
Liquid Water Content ◽  
Nox Emission ◽  
Photochemical Oxidation ◽  
Biomass Combustion ◽  
Emission Sources ◽  
Relative Contribution ◽  
Haze Pollution ◽  
The Mean ◽  
Oxidation Ratio

Abstract. PM2.5 haze pollution driven by secondary inorganic NO3− has been a great concern in East Asia. It is, therefore, imperative to identify its sources and oxidation processes, for which nitrogen and oxygen stable isotopes are powerful tracers. Here, we determined the δ15N (NO3−) and Δ17O (NO3−) of PM2.5 in Seoul from 2018 to 2019, and estimated quantitatively the relative contribution of oxidation pathways for particulate NO3− and major NOx emission sources. In the range of PM2.5 mass concentration from 7.5 g m−3 (summer) to 139.0 g m−3 (winter), the mean δ15N was −0.7 ± 3.3 ‰ and 3.8 ± 3.7 ‰, and the mean Δ17O was 23.2 ± 2.2 ‰ and 27.7 ± 2.2 ‰ in the summer and winter, respectively. While OH oxidation was the dominant pathway for NO3− during the summer (87 %), nighttime formation via N2O5 and NO3 was more important (38 %) during the winter, when aerosol liquid water content (AWLC) and nitrogen oxidation ratio (NOR) were higher. Interestingly, the highest Δ17O was coupled with the lowest δ 15N and highest NOR in record-breaking winter PM2.5 episodes, revealing the critical role of photochemical oxidation process in severe winter haze development. For NOx sources, vehicle emissions were confirmed as a main contributor, followed by biomass combustion from various activities. The contribution from biogenic soil and coal combustion was slightly increased in summer and winter, respectively. Our results built on multiple-isotope approach provide the first explicit evidence for NO3− formation processes and major NOx emission sources in Seoul megacity and suggest an effective mitigation measure to improve PM2.5 pollution.

Long-term Observations of Atmospheric Speciated Mercury at a Coastal Site in the Northern Gulf of Mexico during 2007–2018

2020 ◽  
Author(s):  
Xinrong Ren ◽  
Winston Luke ◽  
Paul Kelley ◽  
Mark Cohen ◽  
Mark Olson ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Gulf Of Mexico ◽  
Wet Deposition ◽  
Elemental Mercury ◽  
Early Summer ◽  
Atmospheric Mercury ◽  
Photochemical Oxidation ◽  
Mercury Species ◽  
Monitoring Site ◽  
Northern Coast

&lt;p&gt;Atmospheric mercury species (including gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM)), trace pollutants (including O&lt;sub&gt;3&lt;/sub&gt;, SO&lt;sub&gt;2&lt;/sub&gt;, CO, NO, NO&lt;sub&gt;Y&lt;/sub&gt; and black carbon), and meteorological parameters have been continuously monitored since 2007 at an Atmospheric Mercury Network (AMNet) site located on the northern coast of the Gulf of Mexico at the Grand Bay National Estuarine Research Reserve (NERR) in Moss Point, Mississippi. For the data collected between 2007 and 2018, the average concentrations and standard deviations were 1.39 &amp;#177; 0.22 ng m&lt;sup&gt;-3&lt;/sup&gt; for GEM, 5.1 &amp;#177; 10.2 pg m&lt;sup&gt;-3&lt;/sup&gt; for GOM, 5.9 &amp;#177; 13.0 pg m&lt;sup&gt;-3&lt;/sup&gt; for PBM, and 309 &amp;#177; 407 ng m&lt;sup&gt;-2&lt;/sup&gt; wk&lt;sup&gt;-1&lt;/sup&gt; for mercury wet deposition, with interannual trends of -0.009 ng m&lt;sup&gt;-3&lt;/sup&gt; yr&lt;sup&gt;-1&lt;/sup&gt; for GEM, -0.36 pg m&lt;sup&gt;-3&lt;/sup&gt; yr&lt;sup&gt;-1&lt;/sup&gt; for GOM, 0.18 pg m&lt;sup&gt;-3&lt;/sup&gt; yr&lt;sup&gt;-1&lt;/sup&gt; for PBM, and 2.8 ng m&lt;sup&gt;-2&lt;/sup&gt; wk&lt;sup&gt;-1&lt;/sup&gt; yr&lt;sup&gt;-1&lt;/sup&gt; for mercury wet deposition. The trends are statistically significant for GEM and GOM, but not statistically significant for PBM and mercury wet deposition. Diurnal variation of GEM shows lower concentrations in the early morning due to GEM depletion likely due to plant uptake in high humidity events and slight elevation during the day likely due to downward mixing of higher concentrations of GEM in the air aloft to the surface. Seasonal variation of GEM shows higher levels in winter and spring and lower levels in summer and fall. Diurnal variations of both GOM and PBM show broad peaks in the afternoon likely due to photochemical oxidation of GEM. Seasonally, PBM measurements exhibit higher levels in winter and early spring and lower levels in summer, while GOM measurements show high levels in late spring/early summer and late fall and low levels in winter. The seasonal variation of mercury wet deposition shows higher values in summer and lower values in winter due to higher precipitation amounts in summer than in winter. As expected, anticorrelation between Hg wet deposition and the sum of GOM and PBM but positive correlation between Hg wet deposition and rainfall were observed. Correlation among GOM, ozone, and SO&lt;sub&gt;2&lt;/sub&gt; suggests two possible GOM sources: direct emissions and photochemical oxidation of GEM with the possible influence of boundary dynamics and seasonal variability. This study indicates that the monitoring site, which is located in a coastal environment of the Gulf of Mexico, might experience impacts from mercury sources that are both local and regional in nature.&lt;/p&gt;

scholarly journals Gaseous elemental mercury depletion events observed at Cape Point during 2007–2008

2010 ◽  
Vol 10 (3) ◽  
pp. 1121-1131 ◽  
Author(s):  
E.-G. Brunke ◽  
C. Labuschagne ◽  
R. Ebinghaus ◽  
H. H. Kock ◽  
F. Slemr
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Chemical Mechanism ◽  
Polar Regions ◽  
Gaseous Elemental Mercury ◽  
Transport Distance ◽  
Gaseous Mercury ◽  
Urban Emissions

Abstract. Gaseous mercury in the marine boundary layer has been measured with a 15 min temporal resolution at the Global Atmosphere Watch station Cape Point since March 2007. The most prominent features of the data until July 2008 are the frequent occurrences of pollution (PEs) and depletion events (DEs). Both types of events originate mostly within a short transport distance (up to about 100 km), which are embedded in air masses ranging from marine background to continental. The Hg/CO emission ratios observed during the PEs are within the range reported for biomass burning and industrial/urban emissions. The depletion of gaseous mercury during the DEs is in many cases almost complete and suggests an atmospheric residence time of elemental mercury as short as a few dozens of hours, which is in contrast to the commonly used estimate of approximately 1 year. The DEs observed at Cape Point are not accompanied by simultaneous depletion of ozone which distinguishes them from the halogen driven atmospheric mercury depletion events (AMDEs) observed in Polar Regions. Nonetheless, DEs similar to those observed at Cape Point have also been observed at other places in the marine boundary layer. Additional measurements of mercury speciation and of possible mercury oxidants are hence called for to reveal the chemical mechanism of the newly observed DEs and to assess its importance on larger scales.

scholarly journals Enhanced production of oxidised mercury over the tropical Pacific Ocean: a key missing oxidation pathway

2014 ◽  
Vol 14 (3) ◽  
pp. 1323-1335 ◽  
Author(s):  
F. Wang ◽  
A. Saiz-Lopez ◽  
A. S. Mahajan ◽  
J. C. Gómez Martín ◽  
D. Armstrong ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Oxidation Mechanism ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Mercury Oxidation ◽  
Gaseous Elemental Mercury ◽  
Enhanced Production ◽  
Modelling Studies ◽  
Aquatic Food ◽  
The Stability

Abstract. Mercury is a contaminant of global concern. It is transported in the atmosphere primarily as gaseous elemental mercury, but its reactivity and deposition to the surface environment, through which it enters the aquatic food chain, is greatly enhanced following oxidation. Measurements and modelling studies of oxidised mercury in the polar to sub-tropical marine boundary layer (MBL) have suggested that photolytically produced bromine atoms are the primary oxidant of mercury. We report year-round measurements of elemental and oxidised mercury, along with ozone, halogen oxides (IO and BrO) and nitrogen oxides (NO2), in the MBL over the Galápagos Islands in the equatorial Pacific. Elemental mercury concentration remained low throughout the year, while higher than expected levels of oxidised mercury occurred around midday. Our results show that the production of oxidised mercury in the tropical MBL cannot be accounted for by bromine oxidation only, or by the inclusion of ozone and hydroxyl. As a two-step oxidation mechanism, where the HgBr intermediate is further oxidised to Hg(II), depends critically on the stability of HgBr, an additional oxidant is needed to react with HgBr to explain more than 50% of the observed oxidised mercury. Based on best available thermodynamic data, we show that atomic iodine, NO2, or HO2 could all play the potential role of the missing oxidant, though their relative importance cannot be determined explicitly at this time due to the uncertainties associated with mercury oxidation kinetics. We conclude that the key pathway that significantly enhances atmospheric mercury oxidation and deposition to the tropical oceans is missing from the current understanding of atmospheric mercury oxidation.

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

2015 ◽  
Vol 15 (20) ◽  
pp. 28217-28247 ◽  
Author(s):  
A. Weigelt ◽  
R. Ebinghaus ◽  
N. Pirrone ◽  
J. Bieser ◽  
J. Bödewadt ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vertical Profile ◽  
Mixed Boundary ◽  
Elemental Mercury ◽  
Vertical Gradient ◽  
Atmospheric Mercury ◽  
Observation System ◽  
Vertical Profiles ◽  
Free Troposphere ◽  
Airborne Measurements

Abstract. Measurements of the vertical distribution of atmospheric mercury (Hg) are rare, because airborne measurements are expensive and labour intensive. Consequently, only a few vertical Hg profile measurements have been reported since the 1970s. Besides the CARIBIC passenger aircraft observations, the latest vertical profile over Europe was measured in 1996. Within the Global Mercury Observation System (GMOS) project four vertical profiles were taken on board research aircraft (CASA-212) in August 2013 in background air over different locations in Slovenia and Germany. Each vertical profile consists of at least seven 5 min horizontal flight sections from 500 m above ground to 3000 m a.s.l. Gaseous elemental mercury (GEM) was measured with a Tekran 2537X analyser and a Lumex RA-915-AM. Total gaseous mercury (TGM) was measured using a Tekran 2537B analyser and gaseous oxidized mercury (GOM) was sampled onto 8 denuders for post flight analysis (one for each profile, three during the transfer flights, and two blanks). In addition to the mercury measurements, SO2, CO, O3, NO, NO2, as well as basic meteorological parameters (pressure, temperature, relative humidity) have been measured. Additional ground based speciated mercury measurements at the GMOS master site in Waldhof (Germany) were used to extend the profile to the ground. No vertical gradient was found inside the well mixed boundary layer (variation by less than 0.1 ng m-3) at different sites with GEM varying from location to location between 1.4 and 1.6 ng m-3 (STP; standard conditions: p = 1013.25 hPa, T = 273.15 K). At all locations GEM dropped to 1.3 ng m-3 (STP) when entering the free troposphere and remained constant at higher altitudes. The combination of the vertical profile, measured on 21 August 2013, over Leipzig (Germany) with the CARIBIC measurements during ascent and descent to Frankfurt airport (Germany) at approximately the same time provide a unique central European vertical profile from inside the boundary layer (550 m a.s.l.) to the upper free troposphere (10 500 m a.s.l.) and shows a fairly constant free tropospheric TGM concentration of 1.3 ng m-3 (STP). The highest GOM concentrations of up to 60 pg m-3 (STP, denuder samples) were found above the boundary layer during the transfer flights.

scholarly journals Closing the Dimethyl Sulfide Budget in the Tropical Marine Boundary Layer during the Pacific Atmospheric Sulfur Experiment

2009 ◽  
Vol 9 (4) ◽  
pp. 17265-17296 ◽  
Author(s):  
S. A. Conley ◽  
I. Faloona ◽  
G. H. Miller ◽  
B. Blomquist ◽  
D. Lenschow ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Mole Fraction ◽  
Loss Rate ◽  
Marine Boundary Layer ◽  
Photochemical Oxidation ◽  
Flux Divergence ◽  
Horizontal Advection ◽  
The Pacific ◽  
The Mean ◽  
Atmospheric Sulfur

Abstract. Fourteen research flights were conducted with the National Center for Atmospheric Research (NCAR) C-130 near Christmas Island (2° N, 157° W) during the summer of 2007 as part of the Pacific Atmospheric Sulfur Experiment (PASE). In order to tightly constrain the scalar budget of DMS, fluxes were measured at various levels in the marine boundary layer (MBL) from near the surface (30 m) to the top of the mixed layer (500 m) providing greater accuracy of the flux divergence calculation in the DMS budget. The observed mean mole fraction of DMS in the MBL exhibited the well known diurnal cycle, ranging from 50 pptv in the daytime to 110 pptv at night. Contributions from horizontal advection are included using a multivariate regression of all DMS flight data from within the MBL to estimate the mean gradients and trends. With this technique we consider the residual term in the DMS budget as an estimate of overall photochemical oxidation. Error analysis of the various terms in the DMS budget indicate that chemical losses acting on time scales of up to 110 h can be inferred with this technique. On average, photochemistry accounted for 7.3 ppt hr−1 loss rate for the seven daytime flights, with an estimated error of 0.6 ppt/hr. The loss rate due to expected OH oxidation is sufficient to explain the net DMS destruction without invoking the action of additional oxidants (e.g. reactive halogens.) The observed ocean flux of DMS averaged 3.1 (±1.5)μmol m−2 d−1, and generally decreased throughout the sunlit hours. The average entrainment flux at the top of the MBL was 2.5 μmol m−2 d−1; therefore the flux divergence term in the budget equation only contributed an average increase of 1.3 ppt hr−1 to the mean MBL mole fraction. Over the entire mission, the horizontal advection contribution to the overall budget was 0.2 ppt hr−1, indicating a mean atmospheric DMS gradient nearly perpendicular to the east-southeasterly trade winds and the chlorophyll gradient in the equatorial upwelling ocean. Nonetheless, horizontal advection was a significant term in the budget of any given flight, ranging from −1.5 to 2.3 ppt hr−1, indicating a patchy and random seawater DMS distribution, and thus needs to be accounted for in budget studies.

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

2016 ◽  
Vol 16 (20) ◽  
pp. 13131-13148 ◽  
Author(s):  
Hui Zhang ◽  
Xuewu Fu ◽  
Che-Jen Lin ◽  
Lihai Shang ◽  
Yiping Zhang ◽  
...  
Keyword(s):  
Southeast Asia ◽  
Summer Monsoon ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Southwestern China ◽  
Strong Impact ◽  
Gaseous Elemental Mercury ◽  
South And Southeast Asia ◽  
Transboundary Transport ◽  
The Mean

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

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