scholarly journals Potential sources and processes affecting speciated atmospheric mercury at Kejimkujik National Park, Canada

2016 ◽  
Author(s):  
Xiaohong Xu ◽  
Yanying Liao ◽  
Irene Cheng ◽  
Leiming Zhang
Keyword(s):  
Air Pollutants ◽  
National Park ◽  
Treatment Options ◽  
Model Performance ◽  
Principal Component ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Strong Impact ◽  
Good For ◽  
Kejimkujik National Park

Abstract. Source apportionment analysis was conducted with Positive Matrix Factorization (PMF) and Principal Component Analysis (PCA) methods using concentrations of speciated mercury (Hg), i.e., gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM), and other air pollutants collected at Kejimkujik National Park, Nova Scotia, Canada in 2009 and 2010. The results were largely consistent between the two years for both methods. The same four source factors were identified in each year using PMF method. In both years, factor Photochemistry and Re-emission had the largest contributions to atmospheric Hg, while the contributions of Combustion Emission and Industrial Sulfur varied slightly between the two years. Four components were extracted with air pollutants only in each year using PCA method. Consistency between the results of PMF and PCA include, 1) most or all PMF factors overlapped with PCA components, 2) both methods suggest strong impact of photochemistry, but little association between ambient Hg and sea salt, 3) shifting of PMF source profiles and source contributions from one year to another was echoed in PCA. Inclusion of meteorological parameters led to identification of an additional component – Hg Wet Deposition in PCA, while it did not affect the identification of other components. The PMF model performance was comparable in 2009 and 2010. Among the three Hg forms, the agreement between predicted and observed annual mean concentrations were excellent for GEM, very good for PBM and acceptable for GOM. However, on daily basis, the agreement was very good for GEM, but poor for GOM and PBM. Sensitivity tests suggest that increasing sample size by imputation is not effective in improving model performance, while reducing the fraction of concentrations below method detection limit, by either scaling GOM and PBM to higher concentrations or combining them to reactive mercury, is effective. Most of the data treatment options considered had little impact on the source identification/contribution.

scholarly journals Potential sources and processes affecting speciated atmospheric mercury at Kejimkujik National Park, Canada: comparison of receptor models and data treatment methods

2017 ◽  
Vol 17 (2) ◽  
pp. 1381-1400 ◽  
Author(s):  
Xiaohong Xu ◽  
Yanyin Liao ◽  
Irene Cheng ◽  
Leiming Zhang
Keyword(s):  
Air Pollutants ◽  
National Park ◽  
Treatment Options ◽  
Model Performance ◽  
Principal Component ◽  
Atmospheric Mercury ◽  
Strong Impact ◽  
Data Treatment ◽  
Good For ◽  
Kejimkujik National Park

Abstract. Source apportionment analysis was conducted with positive matrix factorization (PMF) and principal component analysis (PCA) methods using concentrations of speciated mercury (Hg), i.e., gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM), and other air pollutants collected at Kejimkujik National Park, Nova Scotia, Canada, in 2009 and 2010. The results were largely consistent between the 2 years for both methods. The same four source factors were identified in each year using PMF method. In both years, factor photochemistry and re-emission had the largest contributions to atmospheric Hg, while the contributions of combustion emission and industrial sulfur varied slightly between the 2 years. Four components were extracted with air pollutants only in each year using PCA method. Consistencies between the results of PMF and PCA include (1) most or all PMF factors overlapped with PCA components, (2) both methods suggest strong impact of photochemistry but little association between ambient Hg and sea salt, and (3) shifting of PMF source profiles and source contributions from one year to another was echoed in PCA. Inclusion of meteorological parameters led to identification of an additional component, Hg wet deposition in PCA, while it did not affect the identification of other components. The PMF model performance was comparable in 2009 and 2010. Among the three Hg forms, the agreements between model-reproduced and observed annual mean concentrations were excellent for GEM, very good for PBM, and acceptable for GOM. However, on a daily basis, the agreement was very good for GEM but poor for GOM and PBM. Sensitivity tests suggest that increasing sample size by imputation is not effective in improving model performance, while reducing the fraction of concentrations below method detection limit, by either scaling GOM and PBM to higher concentrations or combining them to reactive mercury, is effective. Most of the data treatment options considered had little impact on the source identification or contribution.

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

2016 ◽  
Author(s):  
Hui Zhang ◽  
Xuewu Fu ◽  
Che-Jen Lin ◽  
Lihai Shang ◽  
Yiping Zhang ◽  
...  
Keyword(s):  
Southeast Asia ◽  
Summer Monsoon ◽  
Source Region ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Southwestern China ◽  
Anthropogenic Source ◽  
Strong Impact ◽  
Gaseous Elemental Mercury ◽  
South And Southeast Asia

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 (± standard deviation) for TGM, GOM and PBM were 2.09 ± 0.63 ng m−3, 2.2 ± 2.3 pg m−3 and 31.3 ± 28.4 pg m−3, respectively. TGM showed a monsoonal distribution pattern with relatively higher concentrations (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 in the non-ISM period. Similarly, GOM and PBM concentrations were higher in the ISM period than in 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. Consequently, southwestern China is an important anthropogenic source region of ALS during the ISM period. The biomass burning in Southeast Asia and anthropogenic Hg emissions from South Asia should be the source of atmospheric Hg in remote areas of southwestern China during the non-ISM period.

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.

scholarly journals Observed decrease in atmospheric mercury explained by global decline in anthropogenic emissions

2016 ◽  
Vol 113 (3) ◽  
pp. 526-531 ◽  
Author(s):  
Yanxu Zhang ◽  
Daniel J. Jacob ◽  
Hannah M. Horowitz ◽  
Long Chen ◽  
Helen M. Amos ◽  
...  
Keyword(s):  
North America ◽  
Large Scale ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Small Scale ◽  
Commercial Products ◽  
Earth Observing System ◽  
Global Emission ◽  
Emission Controls ◽  
Phase Out

Observations of elemental mercury (Hg0) at sites in North America and Europe show large decreases (∼1–2% y−1) from 1990 to present. Observations in background northern hemisphere air, including Mauna Loa Observatory (Hawaii) and CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) aircraft flights, show weaker decreases (<1% y−1). These decreases are inconsistent with current global emission inventories indicating flat or increasing emissions over that period. However, the inventories have three major flaws: (i) they do not account for the decline in atmospheric release of Hg from commercial products; (ii) they are biased in their estimate of artisanal and small-scale gold mining emissions; and (iii) they do not properly account for the change in Hg0/HgII speciation of emissions from coal-fired utilities after implementation of emission controls targeted at SO2 and NOx. We construct an improved global emission inventory for the period 1990 to 2010 accounting for the above factors and find a 20% decrease in total Hg emissions and a 30% decrease in anthropogenic Hg0 emissions, with much larger decreases in North America and Europe offsetting the effect of increasing emissions in Asia. Implementation of our inventory in a global 3D atmospheric Hg simulation [GEOS-Chem (Goddard Earth Observing System-Chemistry)] coupled to land and ocean reservoirs reproduces the observed large-scale trends in atmospheric Hg0 concentrations and in HgII wet deposition. The large trends observed in North America and Europe reflect the phase-out of Hg from commercial products as well as the cobenefit from SO2 and NOx emission controls on coal-fired utilities.

scholarly journals Ensemble Predictions of Air Pollutants in China in 2013 for Health Effects Studies Using WRF/CMAQ Modeling System with Four Emission Inventories

2017 ◽  
Author(s):  
Jianlin Hu ◽  
Xun Li ◽  
Lin Huang ◽  
Qi Ying ◽  
Qiang Zhang ◽  
...  
Keyword(s):  
Air Quality ◽  
Health Effects ◽  
Air Pollutants ◽  
Emission Inventory ◽  
Model Performance ◽  
Observation Data ◽  
Emission Inventories ◽  
Air Quality Model ◽  
Quality Model ◽  
Future Health

Abstract. Accurate exposure estimates are required for health effects analyses of severe air pollution in China. Chemical transport models (CTMs) are widely used tools to provide detailed information of spatial distribution, chemical composition, particle size fractions, and source origins of pollutants. The accuracy of CTMs' predictions in China is largely affected by the uncertainties of public available emission inventories. The Community Multi-scale Air Quality model (CMAQ) with meteorological inputs from the Weather Research and Forecasting model (WRF) were used in this study to simulate air quality in China in 2013. Four sets of simulations were conducted with four different anthropogenic emission inventories, including the Multi-resolution Emission Inventory for China (MEIC), the Emission Inventory for China by School of Environment at Tsinghua University (SOE), the Emissions Database for Global Atmospheric Research (EDGAR), and the Regional Emission inventory in Asia version 2 (REAS2). Model performance was evaluated against available observation data from 422 sites in 60 cities across China. Model predictions of O3 and PM2.5 with the four inventories generally meet the criteria of model performance, but difference exists in different pollutants and different regions among the inventories. Ensemble predictions were calculated by linearly combining the results from different inventories under the constraint that sum of the squared errors between the ensemble results and the observations from all the cities was minimized. The ensemble annual concentrations show improved agreement with observations in most cities. The mean fractional bias (MFB) and mean fractional errors (MFE) of the ensemble predicted annual PM2.5 at the 60 cities are −0.11 and 0.24, respectively, which are better than the MFB (−0.25–−0.16) and MFE (0.26–0.31) of individual simulations. The ensemble annual 1-hour peak O3 (O3-1 h) concentrations are also improved, with mean normalized bias (MNB) of 0.03 and mean normalized errors (MNE) of 0.14, compared to MNB of 0.06–0.19 and MNE of 0.16–0.22 of the individual predictions. The ensemble predictions agree better with observations with daily, monthly, and annual averaging times in all regions of China for both PM2.5 and O3-1 h. The study demonstrates that ensemble predictions by combining predictions from individual emission inventories can improve the accuracy of predicted temporal and spatial distributions of air pollutants. This study is the first ensemble model study in China using multiple emission inventories and the results are publicly available for future health effects studies.

scholarly journals Simulation of atmospheric mercury depletion events (AMDEs) during polar springtime using the MECCA box model

2008 ◽  
Vol 8 (23) ◽  
pp. 7165-7180 ◽  
Author(s):  
Z.-Q. Xie ◽  
R. Sander ◽  
U. Pöschl ◽  
F. Slemr
Keyword(s):  
Aqueous Phase ◽  
Ozone Depletion ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Box Model ◽  
Rate Coefficients ◽  
Mercury Species ◽  
Phase Reaction ◽  
Gaseous Elemental Mercury ◽  
Sea Salt Aerosol

Abstract. Atmospheric mercury depletion events (AMDEs) during polar springtime are closely correlated with bromine-catalyzed tropospheric ozone depletion events (ODEs). To study gas- and aqueous-phase reaction kinetics and speciation of mercury during AMDEs, we have included mercury chemistry into the box model MECCA (Module Efficiently Calculating the Chemistry of the Atmosphere), which enables dynamic simulation of bromine activation and ODEs. We found that the reaction of Hg with Br atoms dominates the loss of gaseous elemental mercury (GEM). To explain the experimentally observed synchronous depletion of GEM and O3, the reaction rate of Hg+BrO has to be much lower than that of Hg+Br. The synchronicity is best reproduced with rate coefficients at the lower limit of the literature values for both reactions, i.e. kHg+Br≈3×10−13 and kHg+BrO≤1×10−15 cm3 molecule−1 s−1, respectively. Throughout the simulated AMDEs, BrHgOBr was the most abundant reactive mercury species, both in the gas phase and in the aqueous phase. The aqueous-phase concentrations of BrHgOBr, HgBr2, and HgCl2 were several orders of magnitude larger than that of Hg(SO3)22−. Considering chlorine chemistry outside depletion events (i.e. without bromine activation), the concentration of total divalent mercury in sea-salt aerosol particles (mostly HgCl42−) was much higher than in dilute aqueous droplets (mostly Hg(SO3)22−), and did not exhibit a diurnal cycle (no correlation with HO2 radicals).

Are Methylmercury Concentrations in the Wetlands of Kejimkujik National Park, Nova Scotia, Canada, Dependent on Geology?

2003 ◽  
Vol 32 (6) ◽  
pp. 2085-2094 ◽  
Author(s):  
Steven D. Siciliano ◽  
Al Sangster ◽  
Chris J. Daughney ◽  
Lisa Loseto ◽  
James J. Germida ◽  
...  
Keyword(s):  
Nova Scotia ◽  
National Park ◽  
Kejimkujik National Park

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.

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