scholarly journals An assessment of atmospheric mercury in the Community Multiscale Air Quality (CMAQ) model at an urban site and a rural site in the Great Lakes Region of North America

2012 ◽  
Vol 12 (15) ◽  
pp. 7117-7133 ◽  
Author(s):  
T. Holloway ◽  
C. Voigt ◽  
J. Morton ◽  
S. N. Spak ◽  
A. P. Rutter ◽  
...  
Keyword(s):  
Air Quality ◽  
Great Lakes ◽  
Numerical Models ◽  
Atmospheric Mercury ◽  
Rural Site ◽  
Urban Site ◽  
Base Case ◽  
Mercury Species ◽  
Great Lakes Region ◽  
Local Emissions

Abstract. Quantitative analysis of three atmospheric mercury species – gaseous elemental mercury (Hg0), reactive gaseous mercury (RGHg) and particulate mercury (PHg) – has been limited to date by lack of ambient measurement data as well as by uncertainties in numerical models and emission inventories. This study employs the Community Multiscale Air Quality Model version 4.6 with mercury chemistry (CMAQ-Hg), to examine how local emissions, meteorology, atmospheric chemistry, and deposition affect mercury concentration and deposition the Great Lakes Region (GLR), and two sites in Wisconsin in particular: the rural Devil's Lake site and the urban Milwaukee site. Ambient mercury exhibits significant biases at both sites. Hg0 is too low in CMAQ-Hg, with the model showing a 6% low bias at the rural site and 36% low bias at the urban site. Reactive mercury (RHg = RGHg + PHg) is over-predicted by the model, with annual average biases >250%. Performance metrics for RHg are much worse than for mercury wet deposition, ozone (O3), nitrogen dioxide (NO2), or sulfur dioxide (SO2). Sensitivity simulations to isolate background inflow from regional emissions suggests that oxidation of imported Hg0 dominates model estimates of RHg at the rural study site (91% of base case value), and contributes 55% to the RHg at the urban site (local emissions contribute 45%).

scholarly journals An assessment of atmospheric mercury in the Community Multiscale Air Quality (CMAQ) model

2012 ◽  
Vol 12 (1) ◽  
pp. 2131-2166 ◽  
Author(s):  
T. Holloway ◽  
C. Voigt ◽  
J. Morton ◽  
S. N. Spak ◽  
A. P. Rutter ◽  
...  
Keyword(s):  
Air Quality ◽  
Performance Metrics ◽  
Numerical Models ◽  
Measurement Data ◽  
Atmospheric Mercury ◽  
Rural Site ◽  
Urban Site ◽  
Base Case ◽  
Mercury Species ◽  
Local Emissions

Abstract. Quantitative analysis of three atmospheric mercury species – gaseous elemental mercury (Hg0), reactive gaseous mercury (RGHg) and particulate mercury (PHg) – has been limited to date by lack of ambient measurement data as well as by uncertainties in numerical models and emission inventories. This study employs the Community Multiscale Air Quality Model version 4.6 with mercury chemistry (CMAQ-Hg), to examine how local emissions, meteorology, atmospheric chemistry, and deposition affect mercury concentration and deposition the Great Lakes Region (GLR), and two sites in Wisconsin in particular: the rural Devil's Lake site and the urban Milwaukee site. Ambient mercury exhibits significant biases at both sites. Hg0 is too low in CMAQ-Hg, with the model showing a 6% low bias at the rural site and 36% low bias at the urban site. Reactive mercury (RHg = RGHg + PHg) is over-predicted by the model, with annual average biases >250%. Performance metrics for RHg are much worse than for mercury wet deposition, ozone (O3), nitrogen dioxide (NO2), or sulfur dioxide (SO2). Sensitivity simulations to isolate background inflow from regional emissions suggests that oxidation of imported Hg0 dominates model estimates of RHg at the rural study site (91% of base case value), and contributes 55% to the RHg at the urban site (local emissions contribute 45%). Limited evidence on the lifetime of RHg transported to the rural site suggests that modeled dry deposition rates are too high, possibly compensating for the erroneously high RHg values.

scholarly journals Overview of the LADCO winter nitrate study: hourly ammonia, nitric acid and PM<sub>2.5</sub> composition at an urban and rural site pair during PM<sub>2.5</sub> episodes in the US Great Lakes region

2012 ◽  
Vol 12 (22) ◽  
pp. 11037-11056 ◽  
Author(s):  
C. Stanier ◽  
A. Singh ◽  
W. Adamski ◽  
J. Baek ◽  
M. Caughey ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitric Acid ◽  
Great Lakes ◽  
Ammonium Nitrate ◽  
Rural Site ◽  
Substantial Contribution ◽  
Urban Site ◽  
Great Lakes Region ◽  
Nitrate Production ◽  
The Us

Abstract. An overview of the LADCO (Lake Michigan Air Directors Consortium) Winter Nitrate Study (WNS) is presented. Sampling was conducted at ground level at an urban-rural pair of sites during January–March 2009 in eastern Wisconsin, toward the western edge of the US Great Lakes region. Areas surrounding these sites experience multiday episodes of wintertime PM2.5 pollution characterized by high fractions of ammonium nitrate in PM, low wind speeds, and air mass stagnation. Hourly surface monitoring of inorganic gases and aerosols supplemented long-term 24-h aerosol chemistry monitoring at these locations. The urban site (Milwaukee, WI) experienced 13 PM2.5 episodes, defined as periods where the seven-hour moving average PM2.5 concentration exceeded 27 μg m−3 for at least four consecutive hours. The rural site experienced seven episodes by the same metric, and all rural episodes coincided with urban episodes. Episodes were characterized by low pressure systems, shallow/stable boundary layer, light winds, and increased temperature and relative humidity relative to climatological mean conditions. They often occurred in the presence of regional snow cover at temperatures near freezing, when snow melt and sublimation could generate fog and strengthen the boundary layer inversion. Substantial contribution to nitrate production from nighttime chemistry of ozone and NO2 to N2O5 and nitric acid is likely and requires further investigation. Pollutant-specific urban excess during episode and non-episode conditions is presented. The largest remaining uncertainties in the conceptual model of the wintertime episodes are the variability from episode-to-episode in ammonia emissions, the balance of daytime and nighttime nitrate production, the relationship between ammonia controls, NOx controls and ammonium nitrate reductions, and the extent to which snow and fog are causal (either through meteorological or chemical processes) rather than just correlated with episodes because of similar synoptic meteorology.

scholarly journals Overview of the LADCO winter nitrate study: hourly ammonia, nitric acid and PM<sub>2.5</sub> composition at an urban and rural site pair during PM<sub>2.5</sub> episodes in the US Great Lakes region

2012 ◽  
Vol 12 (6) ◽  
pp. 14115-14167 ◽  
Author(s):  
C. O. Stanier ◽  
A. Singh ◽  
W. Adamski ◽  
J. Baek ◽  
M. Caughey ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitric Acid ◽  
Great Lakes ◽  
Ammonium Nitrate ◽  
Rural Site ◽  
Substantial Contribution ◽  
Urban Site ◽  
Great Lakes Region ◽  
Nitrate Production ◽  
The Us

Abstract. An overview of the LADCO (Lake Michigan Air Directors Consortium) Winter Nitrate Study (WNS) is presented. Sampling was conducted at ground level at an urban-rural pair of sites during January–March 2009 in eastern Wisconsin, toward the Western edge of the US Great Lakes region. Areas surrounding these sites experience multiday episodes of wintertime PM2.5 pollution characterized by high fractions of ammonium nitrate in PM, low wind speeds, and air mass stagnation. Hourly surface monitoring of inorganic gases and aerosols supplemented long-term 24-h aerosol chemistry monitoring at these locations. The urban site (Milwaukee, WI) experienced 13 PM2.5 episodes, defined as periods where the seven-hour moving average PM2.5 concentration exceeded 27 μg m−3 for at least four consecutive hours. The rural site experienced seven episodes by the same metric, and all rural episodes coincided with urban episodes. Episodes were characterized by low pressure systems, shallow/stable boundary layer, light winds, and increased temperature and relative humidity relative to climatological mean conditions. They often occurred in the presence of regional snow cover at temperatures near freezing, when snow melt and sublimation could generate fog and strengthen the boundary layer inversion. Substantial contribution to nitrate production from nighttime chemistry of ozone and NO2 to N2O5 and nitric acid is likely and requires further investigation. Pollutant-specific urban excess during episode and non-episode conditions is presented. The largest remaining uncertainties in the conceptual model of the wintertime episodes are the variability from episode-to-episode in ammonia emissions, the balance of daytime and nighttime nitrate production, the relationship between ammonia controls, NOx controls and ammonium nitrate reductions, and the extent to which snow and fog are causal (either through meteorological or chemical processes) rather than just correlated with episodes because of similar synoptic meteorology.

scholarly journals In situ measurements of speciated atmospheric mercury and the identification of source regions in the Mexico City Metropolitan Area

2009 ◽  
Vol 9 (1) ◽  
pp. 207-220 ◽  
Author(s):  
A. P. Rutter ◽  
D. C. Snyder ◽  
E. A. Stone ◽  
J. J. Schauer ◽  
R. Gonzalez-Abraham ◽  
...  
Keyword(s):  
Point Source ◽  
Mexico City ◽  
Metropolitan Area ◽  
Atmospheric Mercury ◽  
Point Sources ◽  
Rural Site ◽  
Urban Site ◽  
Trajectory Data ◽  
Source Regions ◽  
Rural Sites

Abstract. In order to expand the currently limited understanding of atmospheric mercury source-receptor relationships in the Mexico City Metropolitan Area, real time measurements of atmospheric mercury were made at a downtown urban site, and a rural site on the outskirts of Mexico City, during March 2006. Numerous short-lived increases in particulate mercury (PHg) and reactive gaseous mercury (RGM) concentrations were observed at the urban site during the 17 day study, and less frequent increases in gaseous elemental mercury (GEM) concentrations were measured at both the urban and rural sites. The episodic increases observed were attributed to plume impacts from industrial point source emissions in and around Mexico City. Average concentrations and standard deviations measured during the study were as follows: i) urban site; PHg=187±300 pg m−3, RGM=62±64 pg m−3, GEM=7.2±4.8 ng m−3, and; ii) rural site; GEM=5.0±2.8 ng m−3. Several source regions of atmospheric mercury to the urban and rural sites were determined using Concentration Field Analysis, in which atmospheric mercury measurements were combined with back trajectory data to determine source regions. Only some source regions correlated to mercury emission sources listed in the Federal Pollutant Release and Transfer Register, leaving the rest unaccounted for. Contributions of anthropogenic mercury point sources in and around Mexico City to concentration averages measured at the urban site during the study were estimated to be: 93±3% of reactive mercury (PHg and RGM), and; 81±0.4% of GEM. Point source contributions to GEM measured at the rural site were 72±1%. GEM and reactive mercury (PHg+RGM) were not found to correlate with biomass burning at either of the measurement sites.

scholarly journals The impact of biomass burning and aqueous-phase processing on air quality: a multi-year source apportionment study in the Po Valley, Italy

2019 ◽  
Author(s):  
Marco Paglione ◽  
Stefania Gilardoni ◽  
Matteo Rinaldi ◽  
Stefano Decesari ◽  
Nicola Zanca ◽  
...  
Keyword(s):  
Air Quality ◽  
Source Apportionment ◽  
Biomass Burning ◽  
Organic Aerosol ◽  
Cold Season ◽  
World Health ◽  
Rural Site ◽  
Urban Site ◽  
Urban Background ◽  
Po Valley

Abstract. The Po Valley (Italy) is a well-known air quality hotspot characterized by Particulate Matter (PM) levels well above the limit set by the European Air Quality Directive and by the World Health Organization, especially during the colder season. In the framework of the Emilia-Romagna regional project SUPERSITO, the southern Po Valley submicron aerosol chemical composition was characterized by means of High-Resolution Aerosol Mass Spectroscopy (HR-AMS) with the specific aim of organic aerosol (OA) characterization and source apportionment. Eight intensive observation periods (IOPs) were carried out over four years (from 2011 to 2014) at two different sites (Bologna, BO, urban background and San Pietro Capofiume, SPC, rural background), to characterize the spatial variability and seasonality of the OA sources, with a special focus on the cold season. On the multi-year basis of the study, the AMS observations show that OA accounts for an average 45 ± 8 % (ranging 33–58 %) and 46 ± 7 % (ranging 36–50 %) of the total non-refractory submicron particle mass (PM1-NR) at the urban and at the rural site, respectively. Primary organic aerosol (POA) comprises biomass burning (23 ± 13 % of OA) and fossil fuel (12 ± 7 %) contributions with a marked seasonality in concentration. As expected, the biomass burning contribution to POA is more significant at the rural site (urban/rural concentrations ratio of 0.67), but it is also an important source of POA at the urban site during the cold season, with contributions ranging from 14 to 38 % of the total OA mass. Secondary organic aerosol (SOA) contribute to OA mass to a much larger extent than POA at both sites throughout the year (69 ± 16 % and 83 ± 16 % at urban and rural, respectively), with important implications for public health. Within the secondary fraction of OA, the measurements highlight the importance of biomass burning ageing products during the cold season, even at the urban background site. This biomass burning SOA fraction represents 14–44 % of the total OA mass in the cold season, indicating that in this region a major contribution of combustion sources to PM mass is mediated by environmental conditions and atmospheric reactivity. Among the environmental factors controlling the formation of SOA in the Po Valley, the availability of liquid water in the aerosol was shown to play a key role in the cold season. We estimate that organic fraction originating from aqueous reactions of biomass burning products (bb-aqSOA) represents 21 % (14–28 %) and 25 % (14–35 %) of the total OA mass and 44 % (32–56 %) and 61 % (21–100 %) of the SOA mass at the urban and rural sites, respectively.

scholarly journals The impact of biomass burning and aqueous-phase processing on air quality: a multi-year source apportionment study in the Po Valley, Italy

2020 ◽  
Vol 20 (3) ◽  
pp. 1233-1254 ◽  
Author(s):  
Marco Paglione ◽  
Stefania Gilardoni ◽  
Matteo Rinaldi ◽  
Stefano Decesari ◽  
Nicola Zanca ◽  
...  
Keyword(s):  
Air Quality ◽  
Source Apportionment ◽  
Biomass Burning ◽  
Organic Aerosol ◽  
Cold Season ◽  
Rural Site ◽  
Urban Site ◽  
Urban Background ◽  
Po Valley ◽  
Rural Sites

Abstract. The Po Valley (Italy) is a well-known air quality hotspot characterized by particulate matter (PM) levels well above the limit set by the European Air Quality Directive and by the World Health Organization, especially during the colder season. In the framework of Emilia-Romagna regional project “Supersito”, the southern Po Valley submicron aerosol chemical composition was characterized by means of high-resolution aerosol mass spectroscopy (HR-AMS) with the specific aim of organic aerosol (OA) characterization and source apportionment. Eight intensive observation periods (IOPs) were carried out over 4 years (from 2011 to 2014) at two different sites (Bologna, BO, urban background, and San Pietro Capofiume, SPC, rural background), to characterize the spatial variability and seasonality of the OA sources, with a special focus on the cold season. On the multi-year basis of the study, the AMS observations show that OA accounts for averages of 45±8 % (ranging from 33 % to 58 %) and 46±7 % (ranging from 36 % to 50 %) of the total non-refractory submicron particle mass (PM1-NR) at the urban and rural sites, respectively. Primary organic aerosol (POA) comprises biomass burning (23±13 % of OA) and fossil fuel (12±7 %) contributions with a marked seasonality in concentration. As expected, the biomass burning contribution to POA is more significant at the rural site (urban / rural concentration ratio of 0.67), but it is also an important source of POA at the urban site during the cold season, with contributions ranging from 14 % to 38 % of the total OA mass. Secondary organic aerosol (SOA) contributes to OA mass to a much larger extent than POA at both sites throughout the year (69±16 % and 83±16 % at the urban and rural sites, respectively), with important implications for public health. Within the secondary fraction of OA, the measurements highlight the importance of biomass burning aging products during the cold season, even at the urban background site. This biomass burning SOA fraction represents 14 %–44 % of the total OA mass in the cold season, indicating that in this region a major contribution of combustion sources to PM mass is mediated by environmental conditions and atmospheric reactivity. Among the environmental factors controlling the formation of SOA in the Po Valley, the availability of liquid water in the aerosol was shown to play a key role in the cold season. We estimate that the organic fraction originating from aqueous reactions of biomass burning products (“bb-aqSOA”) represents 21 % (14 %–28 %) and 25 % (14 %–35 %) of the total OA mass and 44 % (32 %–56 %) and 61 % (21 %–100 %) of the SOA mass at the urban and rural sites, respectively.

scholarly journals Impact of model grid spacing on regional- and urban-scale air quality predictions of organic aerosol

2010 ◽  
Vol 10 (12) ◽  
pp. 30347-30379 ◽  
Author(s):  
C. A. Stroud ◽  
P. A. Makar ◽  
M. D. Moran ◽  
W. Gong ◽  
S. Gong ◽  
...  
Keyword(s):  
Air Quality ◽  
Great Lakes ◽  
Secondary Organic Aerosol ◽  
Chemical Transport ◽  
Organic Aerosol ◽  
Great Lakes Region ◽  
Grid Spacing ◽  
Aerosol Composition ◽  
Resolution Model ◽  
Bear Creek

Abstract. Regional-scale chemical transport model predictions of urban organic aerosol to date tend to be biased low relative to observations, a limitation with important implications for applying such models to human exposure health studies. We used a nested version of Environment Canada's AURAMS model (42-to-15-to-2.5 km nested grid spacing) to predict organic aerosol concentrations for a temporal and spatial domain corresponding to the Border Air Quality and Meteorology Study (BAQS-Met), an air-quality field study that took place in the southern Great Lakes region in the summer of 2007. The use of three different horizontal grid spacings allowed the influence of this parameter to be examined. A domain-wide average for the 2.5 km domain and a matching 15 km subdomain yielded very similar organic aerosol averages (4.8 vs. 4.3 μg m−3, respectively). On regional scales, secondary organic aerosol dominated the organic aerosol composition and was adequately resolved by the 15 km model simulation. However, the shape of the organic aerosol concentration histogram for the Windsor urban station improved for the 2.5 km simulation relative to those from the 42 and 15 km simulations. The model histograms for the Bear Creek and Harrow rural stations were also improved in the high concentration "tail" region. As well the highest-resolution model results captured the midday 4 July organic-aerosol plume at Bear Creek with very good temporal correlation. These results suggest that accurate simulation of urban and large industrial plumes in the Great Lakes region requires the use of a high-resolution model in order to represent urban primary organic aerosol emissions, urban VOC emissions, and the secondary organic aerosol production rates properly. The positive feedback between the secondary organic aerosol production rate and existing organic mass concentration is also represented more accurately with the highest-resolution model. Not being able to capture these finer-scale features may partly explain the consistent negative bias reported in the literature when urban-scale organic aerosol evaluations are made using coarser-scale chemical transport models.

scholarly journals Lake breezes in the southern Great Lakes region and their influence during BAQS-Met 2007

2011 ◽  
Vol 11 (2) ◽  
pp. 3579-3626 ◽  
Author(s):  
D. M. L. Sills ◽  
J. R. Brook ◽  
I. Levy ◽  
P. A. Makar ◽  
J. Zhang ◽  
...  
Keyword(s):  
Air Quality ◽  
Great Lakes ◽  
Weather Prediction ◽  
Great Lakes Region ◽  
Lake Breeze ◽  
Moist Convection ◽  
Study Region ◽  
Synoptic Wind ◽  
Lake Breezes ◽  
Deep Moist Convection

Abstract. Mesoscale observations from the BAQS-Met field experiment during the summer of 2007 were integrated and manually analyzed in order to identify and characterize lake breezes in the southern Great Lakes region of North America, and assess their potential impact on air quality. Lake breezes were found to occur on 90% of study days, often occurring in conditions previously thought to impede their development. They affected all parts of the study region, including southwestern Ontario and nearby portions of southeast Michigan and northern Ohio, occasionally penetrating inland from 100 km to over 200 km. Occurrence rates and penetration distances were found to be higher than previously reported in the literature. This more accurate depiction of observed lake breezes allows a better understanding of their influence on the production and transport of pollutants in this region. The observational analyses were compared with output from subsequent runs of a high-resolution numerical weather prediction model. The model accurately predicted lake breeze occurrence in a variety of synoptic wind regimes, but selected cases showed substantial differences in the detailed timing and location of lake-breeze fronts, and with the initiation of deep moist convection. Knowledge of such strengths and weaknesses will assist with interpretation of results from air quality modelling driven by this meteorological model.

scholarly journals Lake breezes in the southern Great Lakes region and their influence during BAQS-Met 2007

2011 ◽  
Vol 11 (15) ◽  
pp. 7955-7973 ◽  
Author(s):  
D. M. L. Sills ◽  
J. R. Brook ◽  
I. Levy ◽  
P. A. Makar ◽  
J. Zhang ◽  
...  
Keyword(s):  
Air Quality ◽  
Great Lakes ◽  
Weather Prediction ◽  
Great Lakes Region ◽  
Lake Breeze ◽  
Moist Convection ◽  
Study Region ◽  
Synoptic Wind ◽  
Lake Breezes ◽  
Deep Moist Convection

Abstract. Meteorological observations from the BAQS-Met field experiment during the summer months of 2007 were integrated and manually analyzed in order to identify and characterize lake breezes in the southern Great Lakes region of North America, and assess their potential impact on air quality. Lake breezes occurred frequently, with one or more lake breezes identified on 90 % of study days. They affected all parts of the study region, including southwestern Ontario and nearby portions of southeast Lower Michigan and northern Ohio, with lake-breeze fronts occasionally penetrating from 100 km to over 200 km inland. Occurrence rates and penetration distances were found to be higher than previously reported in the literature. This comprehensive depiction of observed lake breezes allows an improved understanding of their influence on the transport, dispersion, and production of pollutants in this region. The observational analyses were compared with output from subsequent runs of a high-resolution numerical weather prediction model. The model accurately predicted lake breeze occurrence and type in a variety of synoptic wind regimes, but selected cases showed substantial differences in the detailed timing and location of lake-breeze fronts, and with the initiation of deep moist convection. Knowledge of such strengths and weaknesses aids in the interpretation of results from air quality models driven by this meteorological model.

scholarly journals Comparison of Atmospheric Mercury Speciation at a Coastal and an Urban Site in Southeastern Texas, USA

Atmosphere ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 73 ◽  
Author(s):  
Travis Griggs ◽  
Lei Liu ◽  
Robert W. Talbot ◽  
Azucena Torres ◽  
Xin Lan
Keyword(s):  
Northern Hemisphere ◽  
Background Level ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Urban Site ◽  
Mercury Species ◽  
Mixing Ratio ◽  
Coastal Site ◽  
Mixing Ratios ◽  
The Relationship

Sixteen months of continuous measurements and the analysis of atmospheric mercury (gaseous elemental mercury GEM, gaseous oxidized mercury GOM, and particulate bound mercury PBM) under urban and coastal settings were conducted in Southeastern Texas. At the urban site, the GEM mean mixing ratio was 185 ppqv, 5%–10% higher than the Northern Hemisphere GEM background level. GOM and PBM mixing ratios were as much as six times higher than their background level. The coastal site GEM mean mixing ratio was 165 ppqv, higher than other coastal sites located in the Northern Hemisphere. GOM and PBM mean mixing ratios at the coastal site were 0.75 ppqv and 0.58 ppqv. The urban site had a higher frequency of high mercury events (>300 ppqv) compared to the coastal site. The diurnal patterns were found for both sites: In the urban environment, GEM accumulated to the maximum mixing ratio just after sunrise and decreased to the minimum mixing ratio in late afternoon. In the coastal environment, GEM decreased at night reaching its minimum mixing ratio before sunrise. The relationship between atmospheric mercury species and meteorological parameters was investigated. An examination of the relationship between atmospheric mercury species and key trace gases was conducted as well, showing that the concurrence of GEM, CO2, CO, CH4, and SO2 maximum mixing ratios was notable and provided evidence they may originate from the same emission source. The coastal site was at times influenced by polluted air from urban Houston and the cleaner Gulf of Mexico marine air at other times.

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