Leiming Zhang - Academia.edu (original) (raw)

Papers by Leiming Zhang

Environmental Reviews

Atmospheric dry and wet deposition of particulate matter controls its lifetime in air and contrib... more Atmospheric dry and wet deposition of particulate matter controls its lifetime in air and contributes to the environmental burden of toxic pollutants and thus has important implications on human and ecosystem health. This synthesis review focuses on atmospheric wet deposition of particulate elements and analyzed their scavenging ratios (i.e., ratio of concentration in precipitation to that in ambient air), solubility, and wet deposition flux measurements based on published studies in the literature, aiming to gather updated knowledge that can be used for modeling their wet deposition. Our analysis finds that scavenging ratios of a specific element have a narrow range. Overall, elemental scavenging ratios for snow are approximately three times higher than those for rain. Elements that are bound to coarse (PM2.5–10) particles have larger scavenging ratios than those bound to fine (PM2.5) particles, except for Fe and Si. Solubility of elements in rainwater ranges from 8% (Fe) to 94% (C...

. Mercury (Hg) is a global toxic pollutant that can be released into the atmosphere through anthr... more . Mercury (Hg) is a global toxic pollutant that can be released into the atmosphere through anthropogenic and natural sources. The uncertainties in the estimated emission amounts are much larger from natural than anthropogenic sources. A method was developed in the present study to quantify the contributions of natural surface mercury emissions to ambient gaseous elemental mercury (GEM) concentrations through application of positive matrix factorization (PMF) analysis with temperature, O3, and NH3 as indicators of GEM emissions from natural surfaces. GEM concentrations were continuously monitored at a 2-hourly resolution at a regional background site in the Yangtze River Delta in Eastern China during 2015–2018. Annual average GEM concentrations were in the range of 2.03–3.01 ng/m3, with a strong decreasing trend at a rate of −0.32 ± 0.07 ng m−3 yr−1 from 2015 to 2018, which was mostly caused by reduced anthropogenic emissions since 2013. The estimated contributions from natural surface emissions of mercury to the ambient GEM concentrations were in the range of 0.90–1.01 ng/m3 on annual average with insignificant interannual changes, but the relative contribution increased significantly from 36 % in 2015 to 53 % in 2018, gradually surpassing those from anthropogenic sources.

ACS Omega

Decadal trends of atmospheric ammonia (NH 3) and their potential causes were explored through the... more Decadal trends of atmospheric ammonia (NH 3) and their potential causes were explored through the analysis of monitored data collected at 15 sites in the United States and 7 sites in Canada. Large percentage increases in the annual average concentration of atmospheric NH 3 , for example, >100% at 6 sites and 40−100% at 10 sites, were observed over the most recent 8−13 year period. In contrast, a decrease or a narrow variation in NH 3 emissions was reported at the state or provincial level in both countries during the same period. Decreased emissions of SO 2 and NO x across North America in the past decade would have reduced the chemical loss of atmospheric NH 3 to form particulate NH 4 +. Such a chemical mechanism was verified through regression analysis at about half of the monitored sites, where the increasing trends in atmospheric NH 3 were partially explained by the reduced NH 4 +. Excluding the reduced contribution from this chemical loss to generate the adjusted annual NH 3 concentration through two approaches, no decreasing trends can be obtained to align those in emissions at most sites, implying that other factors also contributed to the increase in the annual NH 3 concentration. Correlation analysis results implied that enhanced drought conditions and increased ambient temperatures also likely contributed to the increasing trend in the annual NH 3 concentration at some sites. The large percentage increases in the annual NH 3 concentration cannot be fully explained by all the identified causes, leading to oppugning the reality of the decrease in NH 3 emissions reported across North America in the recent decade.

Interactive comment on "A review of current knowledge concerning PM 2.5 chemical composition, aer... more Interactive comment on "A review of current knowledge concerning PM 2.5 chemical composition, aerosol optical properties, and their relationships across China" by Jun Tao et al. Jun Tao et al.

Atmospheric Chemistry and Physics

To grasp the key factors affecting particle mass scattering efficiency (MSE), particle mass and n... more To grasp the key factors affecting particle mass scattering efficiency (MSE), particle mass and number size distribution, PM 2.5 and PM 10 and their major chemical compositions, and the particle scattering coefficient (b sp) under dry conditions were measured at an urban site in Guangzhou, southern China, during 2015-2016. On an annual average, 10 ± 2 %, 48 ± 7 % and 42 ± 8 % of PM 10 mass were in the condensation, droplet and coarse modes, respectively, with mass mean aerodynamic diameters (MMADs) of 0.78±0.07 in the droplet mode and 4.57 ± 0.42 µm in the coarse mode. The identified chemical species mass concentrations can explain 79 ± 3 %, 82 ± 6 % and 57 ± 6 % of the total particle mass in the condensation, droplet and coarse mode, respectively. Organic matter (OM) and elemental carbon (EC) in the condensation mode, OM, (NH 4) 2 SO 4 , NH 4 NO 3 , and crustal element oxides in the droplet mode, and crustal element oxides, OM, and CaSO 4 in the coarse mode, were the dominant chemical species in their respective modes. The measured b sp can be reconstructed to the level of 91±10 % using Mie theory with input of the estimated chemically resolved number concentrations of NaCl, NaNO 3 , Na 2 SO 4 , NH 4 NO 3 , (NH 4) 2 SO 4 , K 2 SO 4 , CaSO 4 , Ca(NO 3) 2 , OM, EC, crustal element oxides and unidentified fraction. MSEs of particle and individual chemical species were underestimated by less than 13 % in any season based on the estimated b sp and chemical species mass concentrations. Seasonal average MSEs varied in the range of 3.5 ± 0.1 to 3.9 ± 0.2 m 2 g −1 for fine particles (aerodynamic diameter smaller than 2.1 µm), which was mainly caused by seasonal variations in the mass fractions and MSEs of the dominant chemical species (OM, NH 4 NO 3 , (NH 4) 2 SO 4) in the droplet mode. MSEs of the dominant chemical species were determined by their lognormal sizedistribution parameters, including MMADs and standard deviation (σ) in the droplet mode.

Atmospheric Chemistry and Physics Discussions

Long-term trends of wet deposition of inorganic ions are affected by multiple factors, among whic... more Long-term trends of wet deposition of inorganic ions are affected by multiple factors, among which emission changes and climate conditions are dominant ones. To assess the effectiveness of emission reductions on the wet deposition of pollutants of interest, contributions from these factors to the long-term trends of wet deposition must be isolated. For this purpose, a two-step approach for preprocessing wet deposition data is presented herein. This new approach aims to reduce the impact of climate anomalies on the trend analysis so that the impact of emission reductions on the wet deposition can be revealed. This approach is applied to a two-decade wet deposition dataset of sulfate (SO4 2-), nitrate (NO3-) and ammonium (NH4 +) at rural Canadian sites. Analysis results show that the approach allows for robustly identifying inflection points on decreasing trends in the wet deposition fluxes of SO4 2and NO3in northern Ontario and Québec. The inflection points match well with the three-phase mitigation of SO2 emissions and two-phase mitigation of NOx emissions in Ontario. Improved correlations between the wet deposition of ions and their precursors' emissions were obtained after reducing the impact from climate anomalies. Furthermore, decadal climate anomalies were identified as dominating the decreasing trends in the wet deposition fluxes of SO4 2and NO3at a western coastal site. Longterm variations in NH4 + wet deposition showed no clear trends due to the compensating effects between NH3 emissions, climate anomalies, and chemistry associated with the emission changes of sulfur and nitrogen.

Atmospheric Chemistry and Physics Discussions

To grasp the key factors affecting particle mass scattering efficiency (MSE), particle mass and n... more To grasp the key factors affecting particle mass scattering efficiency (MSE), particle mass and number size distribution, bulk PM 2.5 and PM 10 and their major chemical compositions, and particle scattering coefficient (b sp) under dry condition were measured at an urban site in Guangzhou, south China during 2015-2016. On annual average, 10±2%, 48±7% and 42±8% of PM 10 mass were in the condensation, droplet and coarse modes, with mass median aerodynamic diameters (MMADs) of 0.21±0.00, 0.78±0.07 and 4.57±0.42 µm, respectively. The identified chemical species mass concentrations can explain 79±3%, 82±6% and 57±6% of the total particle mass in the condensation, droplet and coarse mode, respectively. Organic matter (OM) and elemental carbon (EC) in the condensation mode, OM, (NH 4) 2 SO 4 , NH 4 NO 3 and crustal element oxides in the droplet mode, and crustal element oxides, OM and CaSO 4 in the coarse mode were the dominant chemical species in their respective modes. The measured b sp can be reconstructed to the level of 91±10% using Mie theory with input of the estimated chemically-resolved number concentrations of NaCl, NaNO 3 , Na 2 SO 4 , NH 4 NO 3 , (NH 4) 2 SO 4 , K 2 SO 4 , CaSO 4 , Ca(NO 3) 2 , OM, EC, crustal element oxides and unidentified fraction. MSEs of bulk particle and individual chemical species were underestimated by less than 13 % in any season based on the estimated b sp and chemical species mass concentrations. Seasonal average MSEs varied in a small range of 3.5±0.1 to 3.9±0.2 m 2 g-1 for fine particles, which was mainly caused by seasonal variations of the mass fractions and MSEs of OM in the droplet mode.

Atmospheric Chemistry and Physics Discussions

Amine-containing particles were characterized in an urban area of Chongqing during both summer an... more Amine-containing particles were characterized in an urban area of Chongqing during both summer and winter using a single particle aerosol mass spectrometer (SPAMS). Among the collected ambient particles, 12.7% were amine-containing in winter and 8.3% in summer. Amines were observed to internally mix with elemental carbon (EC), organic carbon (OC), sulfate, and nitrate. Diethylamine (DEA) was the most abundant in both number and peak area among amine-containing particles. Wintertime amine-containing particles were mainly from the northwest direction where a forest park was located; in summer, they were from the northwest and southwest (traffic hub) directions. These origins suggest that vegetation and traffic were the primary sources of particulate amines. The average relative peak area of DEA depended strongly on humidity, indicating that the enhancement of DEA was possibly due to increasing aerosol water content and aerosol acidity. Using an adaptive resonance theory neural network (ART-2a) algorithm, four major types of amine-containing particles were clustered including amine-organic-carbon (A-OC), A-OCEC, DEA-OC, and A-OCEC-aged. The identified particle types imply that amine was uptaken by particles produced from traffic and biomass burning. Knowledge gained in this study is helpful to understand the atmospheric processing, origin, and sources of amine-containing particles in the urban area of Chongqing.

Journal of Advances in Modeling Earth Systems

To quantify differences between dry deposition algorithms commonly used in North America, five mo... more To quantify differences between dry deposition algorithms commonly used in North America, five models were selected to calculate dry deposition velocity (V d) for O 3 and SO 2 over a temperate mixed forest in southern Ontario, Canada, where a 5-year flux database had previously been developed. The models performed better in summer than in winter with correlation coefficients for hourly V d between models and measurements being approximately 0.6 and 0.3, respectively. Differences in mean V d values between models were on the order of a factor of 2 in both summer and winter. All models produced lower V d values than the measurements of O 3 in summer and SO 2 in summer and winter, although the measured V d may be biased. There was not a consistent tendency in the models to overpredict or underpredict for O 3 in winter. Several models produced magnitudes of the diel variation of V d (O 3) comparable to the measurements, while all models produced slightly smaller diel variations than the measurements of V d (SO 2) in summer. A few models produced larger diel variations than the measurements of V d for O 3 and SO 2 in winter. Model differences were mainly due to different surface resistance parameterizations for stomatal and nonstomatal uptake pathways, while differences in aerodynamic and quasi-laminar resistances played only a minor role. It is recommended to use ensemble modeling results for ecosystem impact assessment studies, which provides mean values of all the used models and thus can avoid too much overestimations or underestimations.

Atmospheric Chemistry and Physics

Two speciated and spatially resolved emissions databases for polycyclic aromatic compounds (PACs)... more Two speciated and spatially resolved emissions databases for polycyclic aromatic compounds (PACs) in the Athabasca oil sands region (AOSR) were developed. The first database was derived from volatile organic compound (VOC) emissions data provided by the Cumulative Environmental Management Association (CEMA) and the second database was derived from additional data collected within the Joint Canada-Alberta Oil Sands Monitoring (JOSM) program. CALPUFF modelling results for atmospheric polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, and dibenzothiophenes (DBTs), obtained using each of the emissions databases, are presented and compared with measurements from a passive air monitoring network. The JOSMderived emissions resulted in better model-measurement agreement in the total PAH concentrations and for most PAH species concentrations compared to results using CEMAderived emissions. At local sites near oil sands mines, the percent error of the model compared to observations decreased from 30 % using the CEMA-derived emissions to 17 % using the JOSM-derived emissions. The improvement at local sites was likely attributed to the inclusion of updated tailings pond emissions estimated from JOSM activities. In either the CEMA-derived or JOSM-derived emissions scenario, the model underestimated PAH concentrations by a factor of 3 at remote locations. Potential reasons for the disagreement include forest fire emissions, re-emissions of previously deposited PAHs, and long-range transport not considered in the model. Alkylated PAH and DBT concentrations were also significantly underestimated. The CALPUFF model is expected to predict higher concentrations because of the limited chemistry and deposition modelling. Thus the model underestimation of PACs is likely due to gaps in the emissions database for these compounds and uncertainties in the methodology for estimating the emissions. Future work is required that focuses on improving the PAC emissions estimation and speciation methodologies and reducing the uncertainties in VOC emissions which are subsequently used in PAC emissions estimation. 1 Introduction Polycyclic aromatic compounds (PACs) include not only unsubstituted polycyclic aromatic hydrocarbons (PAHs), which have been the focus of previous scientific investigations (Timoney and Lee, 2011; Jautzy et al., 2013; Galarneau et al., 2014a, b; Hsu et al., 2015), but also alkylated PAHs, unsubstituted and alkylated dibenzothiophenes (DBTs), and other heterocyclic aromatic compounds containing nitrogen, sulfur, or oxygen (

Atmospheric Chemistry and Physics

Environmental Science & Technology

Environmental Pollution

Six different approaches are applied in the present study to apportion the sources of precipitati... more Six different approaches are applied in the present study to apportion the sources of precipitation nitrogen making use of precipitation data of dissolved inorganic nitrogen (DIN, including NO and NH), dissolved organic nitrogen (DON) and δN signatures of DIN collected at six sampling sites in the mountain region of Southwest China. These approaches include one quantitative approach running a Bayesian isotope mixing model (SIAR model) and five qualitative approaches based on in-situ survey (ISS), ratio of NH/NO (R), principal component analysis (PCA), canonical-correlation analysis (CCA) and stable isotope approach (SIA). Biomass burning, coal combustion and mobile exhausts in the mountain region are identified as major sources for precipitation DIN while biomass burning and volatilization sources such as animal husbandries are major ones for DON. SIAR model results suggest that mobile exhausts, biomass burning and coal combustion contributed 25.1 ± 14.0%, 26.0 ± 14.1% and 27.0 ± 12.6%, respectively, to NO on the regional scale. Higher contributions of both biomass burning and coal combustion appeared at rural and urban sites with a significant difference between Houba (rural) and the wetland site (p < 0.05). The R method fails to properly identify sources of DIN, the ISS and SIA approach only respectively identifies DON and DIN sources, the PCA only tracks source types for precipitation N, while the CCA identify sources of both DIN and DON in precipitation. SIAR quantified the contributions of major sources to precipitation NO but failed for precipitation NH and DON. It is recommended to use ISS and SIAR in combination with one or more approaches from PCA, CCA and SIA to apportion precipitation NO sources. As for apportioning precipitation NH sources, more knowledge is needed for local N databases of NH and DON and N fractional mechanisms among gaseous, liquid and particulate surfaces in this mountain region and similar environments.

The Science of the total environment, Jan 28, 2018

Urban fugitive (road and construction) dust PM samples were collected in 21 cities of seven regio... more Urban fugitive (road and construction) dust PM samples were collected in 21 cities of seven regions in China. Seven water-soluble ions, eight sub-fractions of carbonaceous components, and 19 elements were determined to investigate the chemical profiles of urban fugitive dust. Among the analyzed chemical compositions and on regional average, the elemental compositions showed the highest proportion (12.5-28.9% in road dust (RD) and 13.1-38.0% in construction dust (CD)), followed by water-soluble ions (5.1-19.0% in RD and 4.2-16.4% in CD) and carbonaceous fractions (5.4-9.6% in RD and 4.9-9.3% in CD). Chemical compositions measured in CD were all slightly lower than those in RD although statistically insignificant (p > 0.05). Soil dust, which was estimated from Fe concentration, was proved to be the biggest contributor to urban fugitive dust PM mass. While, it showed a higher contribution in Northern China (71.5%) than in Southern China (52.1%). Higher enrichment factors were found ...

Environmental pollution (Barking, Essex : 1987), Jan 2, 2017

Precipitation samples were collected at five rural and one urban sites in the Three Gorges Reserv... more Precipitation samples were collected at five rural and one urban sites in the Three Gorges Reservoir Region (TGR), China from March 2014 to February 2016. The inorganic reactive nitrogen (Nr) contents were analysed to investigate their wet deposition flux, budget, and sources in the area. Annual Nr wet deposition varied from 7.1 to 23.4 kg N ha(-1) yr(-1) over the six sites during the two-year study campaign. The six-site average Nr wet deposition flux was 17.1 and 11.7 kg N ha(-1) yr(-1) in 2014 and 2015, respectively, with 71% from NH4(+) and 29% from NO3(-). Dry deposition flux was estimated using the inferential method, which combined the measured ambient concentrations and modelled dry deposition velocities. The total (dry + wet) Nr deposition fluxes were estimated to be 21.4 kg N ha(-1) yr(-1) in 2014 and 16.0 kg N ha(-1) yr(-1) in 2015 at rural sites, and 31.4 and 25.3 kg N ha(-1) yr(-1) at the urban site. Annual average volume weighted mean (VWM) concentrations in precipitat...

Atmospheric Chemistry and Physics Discussions

Interannual variabilities in atmospheric ammonia (NH₃) during the most rec... more Interannual variabilities in atmospheric ammonia (NH₃) during the most recent seven to eleven years were investigated at fourteen sites across North America using the monitored data obtained from NAPS, CAPMoN and AMoN networks. The long-term average of atmospheric NH3 ranged from 0.8 to 2.6 ppb, depending on location, at four urban and two rural/agriculture sites in Canada. The annual average at these sites did not show any deceasing trend with largely decreasing anthropogenic NH₃ emission. An increasing trend was actually identified from 2003 to 2014 at the downtown Toronto site using either the Mann-Kendall or the Ensemble Empirical Mode Decomposition method, but “no” or “stable” trends were identified at other sites. The ~20 % increase during the 11-year period at the site was likely caused by changes in NH₄⁺/NH₃ partitioning and/or air-surface exchange process as a ...

Atmospheric Chemistry and Physics Discussions

Athabasca oil sands industry in northern Alberta, Canada is a possible source of polycyclic aroma... more Athabasca oil sands industry in northern Alberta, Canada is a possible source of polycyclic aromatic compounds (PACs). Monitored PACs, including polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, and dibenzothiophenes, in precipitation and in air at three near-source sites in the Fort MacKay and Fort McMurray area during May 2011 to August 2012 were analyzed to generate a database of scavenging (or washout) ratios (<i>W</i>_t) for PACs scavenged by both snow and rain. Median precipitation and air concentrations of parent PAHs over the May 2011 to August 2012 period ranged from 0.3–184.9 (chrysene) ng L⁻¹ and 0.01–3.9 (naphthalene) ng m⁻³, respectively, which were comparable to literature values. Higher concentrations in precipitation and air were observed for alkylated PAHs and dibenzothiophenes. The median precipitation and air concentrations were 11.3–646.7 (C3-fluoranthene/pyrene) ng...

Environmental Reviews

Atmospheric dry and wet deposition of particulate matter controls its lifetime in air and contrib... more Atmospheric dry and wet deposition of particulate matter controls its lifetime in air and contributes to the environmental burden of toxic pollutants and thus has important implications on human and ecosystem health. This synthesis review focuses on atmospheric wet deposition of particulate elements and analyzed their scavenging ratios (i.e., ratio of concentration in precipitation to that in ambient air), solubility, and wet deposition flux measurements based on published studies in the literature, aiming to gather updated knowledge that can be used for modeling their wet deposition. Our analysis finds that scavenging ratios of a specific element have a narrow range. Overall, elemental scavenging ratios for snow are approximately three times higher than those for rain. Elements that are bound to coarse (PM2.5–10) particles have larger scavenging ratios than those bound to fine (PM2.5) particles, except for Fe and Si. Solubility of elements in rainwater ranges from 8% (Fe) to 94% (C...

. Mercury (Hg) is a global toxic pollutant that can be released into the atmosphere through anthr... more . Mercury (Hg) is a global toxic pollutant that can be released into the atmosphere through anthropogenic and natural sources. The uncertainties in the estimated emission amounts are much larger from natural than anthropogenic sources. A method was developed in the present study to quantify the contributions of natural surface mercury emissions to ambient gaseous elemental mercury (GEM) concentrations through application of positive matrix factorization (PMF) analysis with temperature, O3, and NH3 as indicators of GEM emissions from natural surfaces. GEM concentrations were continuously monitored at a 2-hourly resolution at a regional background site in the Yangtze River Delta in Eastern China during 2015–2018. Annual average GEM concentrations were in the range of 2.03–3.01 ng/m3, with a strong decreasing trend at a rate of −0.32 ± 0.07 ng m−3 yr−1 from 2015 to 2018, which was mostly caused by reduced anthropogenic emissions since 2013. The estimated contributions from natural surface emissions of mercury to the ambient GEM concentrations were in the range of 0.90–1.01 ng/m3 on annual average with insignificant interannual changes, but the relative contribution increased significantly from 36 % in 2015 to 53 % in 2018, gradually surpassing those from anthropogenic sources.

ACS Omega

Decadal trends of atmospheric ammonia (NH 3) and their potential causes were explored through the... more Decadal trends of atmospheric ammonia (NH 3) and their potential causes were explored through the analysis of monitored data collected at 15 sites in the United States and 7 sites in Canada. Large percentage increases in the annual average concentration of atmospheric NH 3 , for example, >100% at 6 sites and 40−100% at 10 sites, were observed over the most recent 8−13 year period. In contrast, a decrease or a narrow variation in NH 3 emissions was reported at the state or provincial level in both countries during the same period. Decreased emissions of SO 2 and NO x across North America in the past decade would have reduced the chemical loss of atmospheric NH 3 to form particulate NH 4 +. Such a chemical mechanism was verified through regression analysis at about half of the monitored sites, where the increasing trends in atmospheric NH 3 were partially explained by the reduced NH 4 +. Excluding the reduced contribution from this chemical loss to generate the adjusted annual NH 3 concentration through two approaches, no decreasing trends can be obtained to align those in emissions at most sites, implying that other factors also contributed to the increase in the annual NH 3 concentration. Correlation analysis results implied that enhanced drought conditions and increased ambient temperatures also likely contributed to the increasing trend in the annual NH 3 concentration at some sites. The large percentage increases in the annual NH 3 concentration cannot be fully explained by all the identified causes, leading to oppugning the reality of the decrease in NH 3 emissions reported across North America in the recent decade.

Interactive comment on "A review of current knowledge concerning PM 2.5 chemical composition, aer... more Interactive comment on "A review of current knowledge concerning PM 2.5 chemical composition, aerosol optical properties, and their relationships across China" by Jun Tao et al. Jun Tao et al.

Atmospheric Chemistry and Physics

To grasp the key factors affecting particle mass scattering efficiency (MSE), particle mass and n... more To grasp the key factors affecting particle mass scattering efficiency (MSE), particle mass and number size distribution, PM 2.5 and PM 10 and their major chemical compositions, and the particle scattering coefficient (b sp) under dry conditions were measured at an urban site in Guangzhou, southern China, during 2015-2016. On an annual average, 10 ± 2 %, 48 ± 7 % and 42 ± 8 % of PM 10 mass were in the condensation, droplet and coarse modes, respectively, with mass mean aerodynamic diameters (MMADs) of 0.78±0.07 in the droplet mode and 4.57 ± 0.42 µm in the coarse mode. The identified chemical species mass concentrations can explain 79 ± 3 %, 82 ± 6 % and 57 ± 6 % of the total particle mass in the condensation, droplet and coarse mode, respectively. Organic matter (OM) and elemental carbon (EC) in the condensation mode, OM, (NH 4) 2 SO 4 , NH 4 NO 3 , and crustal element oxides in the droplet mode, and crustal element oxides, OM, and CaSO 4 in the coarse mode, were the dominant chemical species in their respective modes. The measured b sp can be reconstructed to the level of 91±10 % using Mie theory with input of the estimated chemically resolved number concentrations of NaCl, NaNO 3 , Na 2 SO 4 , NH 4 NO 3 , (NH 4) 2 SO 4 , K 2 SO 4 , CaSO 4 , Ca(NO 3) 2 , OM, EC, crustal element oxides and unidentified fraction. MSEs of particle and individual chemical species were underestimated by less than 13 % in any season based on the estimated b sp and chemical species mass concentrations. Seasonal average MSEs varied in the range of 3.5 ± 0.1 to 3.9 ± 0.2 m 2 g −1 for fine particles (aerodynamic diameter smaller than 2.1 µm), which was mainly caused by seasonal variations in the mass fractions and MSEs of the dominant chemical species (OM, NH 4 NO 3 , (NH 4) 2 SO 4) in the droplet mode. MSEs of the dominant chemical species were determined by their lognormal sizedistribution parameters, including MMADs and standard deviation (σ) in the droplet mode.

Atmospheric Chemistry and Physics Discussions

Long-term trends of wet deposition of inorganic ions are affected by multiple factors, among whic... more Long-term trends of wet deposition of inorganic ions are affected by multiple factors, among which emission changes and climate conditions are dominant ones. To assess the effectiveness of emission reductions on the wet deposition of pollutants of interest, contributions from these factors to the long-term trends of wet deposition must be isolated. For this purpose, a two-step approach for preprocessing wet deposition data is presented herein. This new approach aims to reduce the impact of climate anomalies on the trend analysis so that the impact of emission reductions on the wet deposition can be revealed. This approach is applied to a two-decade wet deposition dataset of sulfate (SO4 2-), nitrate (NO3-) and ammonium (NH4 +) at rural Canadian sites. Analysis results show that the approach allows for robustly identifying inflection points on decreasing trends in the wet deposition fluxes of SO4 2and NO3in northern Ontario and Québec. The inflection points match well with the three-phase mitigation of SO2 emissions and two-phase mitigation of NOx emissions in Ontario. Improved correlations between the wet deposition of ions and their precursors' emissions were obtained after reducing the impact from climate anomalies. Furthermore, decadal climate anomalies were identified as dominating the decreasing trends in the wet deposition fluxes of SO4 2and NO3at a western coastal site. Longterm variations in NH4 + wet deposition showed no clear trends due to the compensating effects between NH3 emissions, climate anomalies, and chemistry associated with the emission changes of sulfur and nitrogen.

Atmospheric Chemistry and Physics Discussions

To grasp the key factors affecting particle mass scattering efficiency (MSE), particle mass and n... more To grasp the key factors affecting particle mass scattering efficiency (MSE), particle mass and number size distribution, bulk PM 2.5 and PM 10 and their major chemical compositions, and particle scattering coefficient (b sp) under dry condition were measured at an urban site in Guangzhou, south China during 2015-2016. On annual average, 10±2%, 48±7% and 42±8% of PM 10 mass were in the condensation, droplet and coarse modes, with mass median aerodynamic diameters (MMADs) of 0.21±0.00, 0.78±0.07 and 4.57±0.42 µm, respectively. The identified chemical species mass concentrations can explain 79±3%, 82±6% and 57±6% of the total particle mass in the condensation, droplet and coarse mode, respectively. Organic matter (OM) and elemental carbon (EC) in the condensation mode, OM, (NH 4) 2 SO 4 , NH 4 NO 3 and crustal element oxides in the droplet mode, and crustal element oxides, OM and CaSO 4 in the coarse mode were the dominant chemical species in their respective modes. The measured b sp can be reconstructed to the level of 91±10% using Mie theory with input of the estimated chemically-resolved number concentrations of NaCl, NaNO 3 , Na 2 SO 4 , NH 4 NO 3 , (NH 4) 2 SO 4 , K 2 SO 4 , CaSO 4 , Ca(NO 3) 2 , OM, EC, crustal element oxides and unidentified fraction. MSEs of bulk particle and individual chemical species were underestimated by less than 13 % in any season based on the estimated b sp and chemical species mass concentrations. Seasonal average MSEs varied in a small range of 3.5±0.1 to 3.9±0.2 m 2 g-1 for fine particles, which was mainly caused by seasonal variations of the mass fractions and MSEs of OM in the droplet mode.

Atmospheric Chemistry and Physics Discussions

Amine-containing particles were characterized in an urban area of Chongqing during both summer an... more Amine-containing particles were characterized in an urban area of Chongqing during both summer and winter using a single particle aerosol mass spectrometer (SPAMS). Among the collected ambient particles, 12.7% were amine-containing in winter and 8.3% in summer. Amines were observed to internally mix with elemental carbon (EC), organic carbon (OC), sulfate, and nitrate. Diethylamine (DEA) was the most abundant in both number and peak area among amine-containing particles. Wintertime amine-containing particles were mainly from the northwest direction where a forest park was located; in summer, they were from the northwest and southwest (traffic hub) directions. These origins suggest that vegetation and traffic were the primary sources of particulate amines. The average relative peak area of DEA depended strongly on humidity, indicating that the enhancement of DEA was possibly due to increasing aerosol water content and aerosol acidity. Using an adaptive resonance theory neural network (ART-2a) algorithm, four major types of amine-containing particles were clustered including amine-organic-carbon (A-OC), A-OCEC, DEA-OC, and A-OCEC-aged. The identified particle types imply that amine was uptaken by particles produced from traffic and biomass burning. Knowledge gained in this study is helpful to understand the atmospheric processing, origin, and sources of amine-containing particles in the urban area of Chongqing.

Journal of Advances in Modeling Earth Systems

To quantify differences between dry deposition algorithms commonly used in North America, five mo... more To quantify differences between dry deposition algorithms commonly used in North America, five models were selected to calculate dry deposition velocity (V d) for O 3 and SO 2 over a temperate mixed forest in southern Ontario, Canada, where a 5-year flux database had previously been developed. The models performed better in summer than in winter with correlation coefficients for hourly V d between models and measurements being approximately 0.6 and 0.3, respectively. Differences in mean V d values between models were on the order of a factor of 2 in both summer and winter. All models produced lower V d values than the measurements of O 3 in summer and SO 2 in summer and winter, although the measured V d may be biased. There was not a consistent tendency in the models to overpredict or underpredict for O 3 in winter. Several models produced magnitudes of the diel variation of V d (O 3) comparable to the measurements, while all models produced slightly smaller diel variations than the measurements of V d (SO 2) in summer. A few models produced larger diel variations than the measurements of V d for O 3 and SO 2 in winter. Model differences were mainly due to different surface resistance parameterizations for stomatal and nonstomatal uptake pathways, while differences in aerodynamic and quasi-laminar resistances played only a minor role. It is recommended to use ensemble modeling results for ecosystem impact assessment studies, which provides mean values of all the used models and thus can avoid too much overestimations or underestimations.

Atmospheric Chemistry and Physics

Two speciated and spatially resolved emissions databases for polycyclic aromatic compounds (PACs)... more Two speciated and spatially resolved emissions databases for polycyclic aromatic compounds (PACs) in the Athabasca oil sands region (AOSR) were developed. The first database was derived from volatile organic compound (VOC) emissions data provided by the Cumulative Environmental Management Association (CEMA) and the second database was derived from additional data collected within the Joint Canada-Alberta Oil Sands Monitoring (JOSM) program. CALPUFF modelling results for atmospheric polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, and dibenzothiophenes (DBTs), obtained using each of the emissions databases, are presented and compared with measurements from a passive air monitoring network. The JOSMderived emissions resulted in better model-measurement agreement in the total PAH concentrations and for most PAH species concentrations compared to results using CEMAderived emissions. At local sites near oil sands mines, the percent error of the model compared to observations decreased from 30 % using the CEMA-derived emissions to 17 % using the JOSM-derived emissions. The improvement at local sites was likely attributed to the inclusion of updated tailings pond emissions estimated from JOSM activities. In either the CEMA-derived or JOSM-derived emissions scenario, the model underestimated PAH concentrations by a factor of 3 at remote locations. Potential reasons for the disagreement include forest fire emissions, re-emissions of previously deposited PAHs, and long-range transport not considered in the model. Alkylated PAH and DBT concentrations were also significantly underestimated. The CALPUFF model is expected to predict higher concentrations because of the limited chemistry and deposition modelling. Thus the model underestimation of PACs is likely due to gaps in the emissions database for these compounds and uncertainties in the methodology for estimating the emissions. Future work is required that focuses on improving the PAC emissions estimation and speciation methodologies and reducing the uncertainties in VOC emissions which are subsequently used in PAC emissions estimation. 1 Introduction Polycyclic aromatic compounds (PACs) include not only unsubstituted polycyclic aromatic hydrocarbons (PAHs), which have been the focus of previous scientific investigations (Timoney and Lee, 2011; Jautzy et al., 2013; Galarneau et al., 2014a, b; Hsu et al., 2015), but also alkylated PAHs, unsubstituted and alkylated dibenzothiophenes (DBTs), and other heterocyclic aromatic compounds containing nitrogen, sulfur, or oxygen (

Atmospheric Chemistry and Physics

Environmental Science & Technology

Environmental Pollution

Six different approaches are applied in the present study to apportion the sources of precipitati... more Six different approaches are applied in the present study to apportion the sources of precipitation nitrogen making use of precipitation data of dissolved inorganic nitrogen (DIN, including NO and NH), dissolved organic nitrogen (DON) and δN signatures of DIN collected at six sampling sites in the mountain region of Southwest China. These approaches include one quantitative approach running a Bayesian isotope mixing model (SIAR model) and five qualitative approaches based on in-situ survey (ISS), ratio of NH/NO (R), principal component analysis (PCA), canonical-correlation analysis (CCA) and stable isotope approach (SIA). Biomass burning, coal combustion and mobile exhausts in the mountain region are identified as major sources for precipitation DIN while biomass burning and volatilization sources such as animal husbandries are major ones for DON. SIAR model results suggest that mobile exhausts, biomass burning and coal combustion contributed 25.1 ± 14.0%, 26.0 ± 14.1% and 27.0 ± 12.6%, respectively, to NO on the regional scale. Higher contributions of both biomass burning and coal combustion appeared at rural and urban sites with a significant difference between Houba (rural) and the wetland site (p &amp;amp;amp;amp;lt; 0.05). The R method fails to properly identify sources of DIN, the ISS and SIA approach only respectively identifies DON and DIN sources, the PCA only tracks source types for precipitation N, while the CCA identify sources of both DIN and DON in precipitation. SIAR quantified the contributions of major sources to precipitation NO but failed for precipitation NH and DON. It is recommended to use ISS and SIAR in combination with one or more approaches from PCA, CCA and SIA to apportion precipitation NO sources. As for apportioning precipitation NH sources, more knowledge is needed for local N databases of NH and DON and N fractional mechanisms among gaseous, liquid and particulate surfaces in this mountain region and similar environments.

The Science of the total environment, Jan 28, 2018

Urban fugitive (road and construction) dust PM samples were collected in 21 cities of seven regio... more Urban fugitive (road and construction) dust PM samples were collected in 21 cities of seven regions in China. Seven water-soluble ions, eight sub-fractions of carbonaceous components, and 19 elements were determined to investigate the chemical profiles of urban fugitive dust. Among the analyzed chemical compositions and on regional average, the elemental compositions showed the highest proportion (12.5-28.9% in road dust (RD) and 13.1-38.0% in construction dust (CD)), followed by water-soluble ions (5.1-19.0% in RD and 4.2-16.4% in CD) and carbonaceous fractions (5.4-9.6% in RD and 4.9-9.3% in CD). Chemical compositions measured in CD were all slightly lower than those in RD although statistically insignificant (p > 0.05). Soil dust, which was estimated from Fe concentration, was proved to be the biggest contributor to urban fugitive dust PM mass. While, it showed a higher contribution in Northern China (71.5%) than in Southern China (52.1%). Higher enrichment factors were found ...

Environmental pollution (Barking, Essex : 1987), Jan 2, 2017

Precipitation samples were collected at five rural and one urban sites in the Three Gorges Reserv... more Precipitation samples were collected at five rural and one urban sites in the Three Gorges Reservoir Region (TGR), China from March 2014 to February 2016. The inorganic reactive nitrogen (Nr) contents were analysed to investigate their wet deposition flux, budget, and sources in the area. Annual Nr wet deposition varied from 7.1 to 23.4 kg N ha(-1) yr(-1) over the six sites during the two-year study campaign. The six-site average Nr wet deposition flux was 17.1 and 11.7 kg N ha(-1) yr(-1) in 2014 and 2015, respectively, with 71% from NH4(+) and 29% from NO3(-). Dry deposition flux was estimated using the inferential method, which combined the measured ambient concentrations and modelled dry deposition velocities. The total (dry + wet) Nr deposition fluxes were estimated to be 21.4 kg N ha(-1) yr(-1) in 2014 and 16.0 kg N ha(-1) yr(-1) in 2015 at rural sites, and 31.4 and 25.3 kg N ha(-1) yr(-1) at the urban site. Annual average volume weighted mean (VWM) concentrations in precipitat...

Atmospheric Chemistry and Physics Discussions

Interannual variabilities in atmospheric ammonia (NH₃) during the most rec... more Interannual variabilities in atmospheric ammonia (NH₃) during the most recent seven to eleven years were investigated at fourteen sites across North America using the monitored data obtained from NAPS, CAPMoN and AMoN networks. The long-term average of atmospheric NH3 ranged from 0.8 to 2.6 ppb, depending on location, at four urban and two rural/agriculture sites in Canada. The annual average at these sites did not show any deceasing trend with largely decreasing anthropogenic NH₃ emission. An increasing trend was actually identified from 2003 to 2014 at the downtown Toronto site using either the Mann-Kendall or the Ensemble Empirical Mode Decomposition method, but “no” or “stable” trends were identified at other sites. The ~20 % increase during the 11-year period at the site was likely caused by changes in NH₄⁺/NH₃ partitioning and/or air-surface exchange process as a ...

Atmospheric Chemistry and Physics Discussions

Athabasca oil sands industry in northern Alberta, Canada is a possible source of polycyclic aroma... more Athabasca oil sands industry in northern Alberta, Canada is a possible source of polycyclic aromatic compounds (PACs). Monitored PACs, including polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, and dibenzothiophenes, in precipitation and in air at three near-source sites in the Fort MacKay and Fort McMurray area during May 2011 to August 2012 were analyzed to generate a database of scavenging (or washout) ratios (<i>W</i>_t) for PACs scavenged by both snow and rain. Median precipitation and air concentrations of parent PAHs over the May 2011 to August 2012 period ranged from 0.3–184.9 (chrysene) ng L⁻¹ and 0.01–3.9 (naphthalene) ng m⁻³, respectively, which were comparable to literature values. Higher concentrations in precipitation and air were observed for alkylated PAHs and dibenzothiophenes. The median precipitation and air concentrations were 11.3–646.7 (C3-fluoranthene/pyrene) ng...