scholarly journals Characteristics of PM2.5 Chemical Compositions and Their Effect on Atmospheric Visibility in Urban Beijing, China during the Heating Season

2018 ◽  
Vol 15 (9) ◽  
pp. 1924 ◽  
Author(s):  
Xing Li ◽  
Shanshan Li ◽  
Qiulin Xiong ◽  
Xingchuan Yang ◽  
Mengxi Qi ◽  
...  
Keyword(s):  
Fine Particles ◽  
Inorganic Ions ◽  
Water Soluble ◽  
Motor Vehicles ◽  
Urban Site ◽  
Chemical Compositions ◽  
Heating Season ◽  
Atmospheric Visibility ◽  
Visibility Impairment ◽  
Mass Concentrations

Beijing, which is the capital of China, suffers from severe Fine Particles (PM2.5) pollution during the heating season. In order to take measures to control the PM2.5 pollution and improve the atmospheric environmental quality, daily PM2.5 samples were collected at an urban site from 15 November to 31 December 2016, characteristics of PM2.5 chemical compositions and their effect on atmospheric visibility were analyzed. It was found that the daily average mass concentrations of PM2.5 ranged from 7.64 to 383.00 μg m−3, with an average concentration of 114.17 μg m−3. On average, the Organic Carbon (OC) and Elemental Carbon (EC) contributed 21.39% and 5.21% to PM2.5, respectively. Secondary inorganic ions (SNA: SO42− + NO3− + NH4+) dominated the Water-Soluble Inorganic Ions (WSIIs) and they accounted for 47.09% of PM2.5. The mass concentrations of NH4+, NO3− and SO42− during the highly polluted period were 8.08, 8.88 and 6.85 times greater, respectively, than during the clean period, which contributed most to the serious PM2.5 pollution through the secondary transformation of NO2, SO2 and NH3. During the highly polluted period, NH4NO3 contributed most to the reconstruction extinction coefficient (b′ext), accounting for 35.7%, followed by (NH4)2SO4 (34.44%) and Organic Matter (OM: 15.24%). The acidity of PM2.5 in Beijing was weakly acid. Acidity of PM2.5 and relatively high humidity could aggravate PM2.5 pollution and visibility impairment by promoting the generation of secondary aerosol. Local motor vehicles contributed the most to NO3−, OC, and visibility impairment in urban Beijing. Other sources of pollution in the area surrounding urban Beijing, including coal burning, agricultural sources, and industrial sources in the Hebei, Shandong, and Henan provinces, released large amounts of SO2, NH3, and NO2. These, which were transformed into SO42−, NH4+, and NO3− during the transmission process, respectively, and had a great impact on atmospheric visibility impairment.

scholarly journals Dominant Contributions of Secondary Aerosols and Vehicle Emissions to Water-Soluble Inorganic Ions of PM2.5 in an Urban Site in the Metropolitan Hangzhou, China

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1529
Author(s):  
Chun Xiong ◽  
Shaocai Yu ◽  
Xue Chen ◽  
Zhen Li ◽  
Yibo Zhang ◽  
...  
Keyword(s):  
Vehicle Emissions ◽  
Inorganic Ions ◽  
Water Soluble ◽  
Urban Site ◽  
Online Systems ◽  
Seasonal Characteristics ◽  
Water Soluble Inorganic Ions ◽  
Secondary Aerosols ◽  
The Mean ◽  
Mass Concentrations

Water soluble inorganic ions (WSIIs) are important components in PM2.5 and could strongly affect the acidity and hygroscopicity of PM2.5. In order to achieve the seasonal characteristics and determine the potential sources of WSIIs in PM2.5 in Hangzhou, online systems were used to measure hourly mass concentrations of WSIIs (SO42–, NO3–, NH4+, Cl–, Na+, K+, Ca2+ and Mg2+) as well as PM2.5, NO2 and SO2 at an urban site for one month each season (May, August, October, December) in 2017. Results showed that the hourly mass concentrations of PM2.5 during the whole campaign varied from 1 to 292 μg·m−3 with the mean of 56.03 μg·m−3. The mean mass concentration of WSIIs was 26.49 ± 20.78 μg·m−3, which contributed 48.28% to averaged PM2.5 mass. SNA (SO42–, NO3– and NH4+) were the most abundant ions in PM2.5 and on average, they comprised 41.57% of PM2.5 mass. PM2.5, NO2, SO2 and WSIIs showed higher mass concentrations in December, possibly due to higher energy consumption emissions, unfavorable meteorological factors (e.g., lower wind speed and temperature) and regional transport. Results from PCA models showed that secondary aerosols and vehicle emissions were the dominant sources of WSIIs in the observations. Our findings highlight the importance of stronger controls on precursor (e.g., SO2 and NO2) emissions in Hangzhou, and show that industrial areas should be controlled at local and regional scales in the future.

scholarly journals Size Distributions of Water-Soluble Inorganic Ions in Atmospheric Aerosols During the Meiyu Period in the Yangtze River Delta, China

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhaoye Wu ◽  
Duanyang Liu ◽  
Tianliang Zhao ◽  
Yan Su ◽  
Bin Zhou
Keyword(s):  
Particle Size ◽  
Fine Particles ◽  
Inorganic Ions ◽  
Bimodal Distribution ◽  
Yangtze River Delta ◽  
Water Soluble ◽  
The North ◽  
Water Soluble Inorganic Ions ◽  
Oxidation Ratio ◽  
Mass Concentrations

In order to investigate the chemical composition distributions and pollution characteristics of Total water-soluble inorganic ions (TWSII) in the rain period (Meiyu) in the East Asian summer monsoon season, including the impact of Meiyu on air pollution in the Yangtze River Delta, East China, the gaseous pollutant concentrations, the 9 sizes segregated particles, and water-soluble inorganic ions of aerosols were measured on the north shore of Taihu Lake from June 4 to July 5, 2016. Results show that the mass concentrations of atmospheric particulate matters (PM2.5 and PM10) and main gaseous pollutants (SO2, NO2, CO, and O3) decrease during the Meiyu period, with the largest decline in PM10 and the smallest in CO. TWSII in atmospheric particles are mainly concentrated in fine particles during the Meiyu period. The values of ρ (TWSII) for PM1.1, PM1.1–2.1, and PM2.1–10 before the Meiyu onset are generally greater than those during the Meiyu period. During the first pollution process, the ρ(TWSII) for PM1.1 and PM1.1–2.1 first increase to the peak values, and then decrease during the moderate rainfall period, when the ρ(TWSII) in PM2.1–10 increase to its maximum before the Meiyu onset. The mass concentrations for anions, cations, and total ions at different particle-size sections all exhibit bimodal distributions before and after the Meiyu onset. The mass concentration peaks at a particle size of 1.1–2.1 μm for fine particles, while at 5.8–9.0 μm (before the Meiyu onset) and 9.0–10.0 μm (during the Meiyu period) for coarse particles, respectively. The peak particle size for mass concentration of coarse particles moves toward larger sizes during the Meiyu period. The mass concentrations of SO42− at different particle-size sections show a bimodal distribution before the Meiyu onset and a multi-modal distribution during the Meiyu period. The mass concentrations of NO3− at different particle-size sections show a bimodal distribution before the Meiyu onset and a unimodal distribution during the Meiyu period. The mass concentrations of NH4+ at different particle-size sections present a bimodal distribution before and after the Meiyu onset, with the particle-size for peak concentrations distributing in 1.1–2.1 and 5.8–9.0 μm before the Meiyu onset, and 9.0–10.0 μm during the Meiyu period. The mean value of nitrogen oxidation ratio (NOR) is higher before the Meiyu onset than after, indicating that the secondary conversion of NO2 before the Meiyu onset is enhanced. The sulfur oxidation ratio (SOR) values are greater than NOR values, but the concentrations of NO2 in the same period during the Meiyu period are higher than those of SO2, which indicates that the secondary conversion of SO2 during the Meiyu period on the north bank of Taihu Lake is stronger than that of NO2. During the whole observation, the contribution of stationary sources mainly contributed to the atmospheric particulate matters during the Meiyu period. The contributions of vehicle exhaust and coal combustion to fine particles are more obviously affected by the changes in meteorological conditions during the Meiyu period, and the vehicle emissions contribute more to PM1.1–2.1 than to PM1.1.

scholarly journals Characteristics of aerosol pollution during heavy haze events in Suzhou, China

2016 ◽  
Vol 16 (11) ◽  
pp. 7357-7371 ◽  
Author(s):  
Mi Tian ◽  
Huanbo Wang ◽  
Yang Chen ◽  
Fumo Yang ◽  
Xiaohua Zhang ◽  
...  
Keyword(s):  
Gas Phase ◽  
Inorganic Ions ◽  
Weather Conditions ◽  
Water Soluble ◽  
Chemical Components ◽  
Formation Mechanisms ◽  
Visibility Impairment ◽  
Aerosol Pollution ◽  
Haze Formation ◽  
High Concentrations

Abstract. Extremely severe haze weather events occurred in many cities in China, especially in the east part of the country, in January 2013. Comprehensive measurements including hourly concentrations of PM2.5 and its major chemical components (water-soluble inorganic ions, organic carbon (OC), and elemental carbon (EC)) and related gas-phase precursors were conducted via an online monitoring system in Suzhou, a medium-sized city in Jiangsu province, just east of Shanghai. PM2.5 (particulate matter with an aerodynamic diameter of 2.5 µm or less) frequently exceeded 150 µg m−3 on hazy days, with the maximum reaching 324 µg m−3 on 14 January 2013. Unfavorable weather conditions (high relative humidity (RH), and low rainfall, wind speed, and atmospheric pressure) were conducive to haze formation. High concentrations of secondary aerosol species (including SO42−, NO3−, NH4+, and SOC) and gaseous precursors were observed during the first two haze events, while elevated primary carbonaceous species emissions were found during the third haze period, pointing to different haze formation mechanisms. Organic matter (OM), (NH4)2SO4, and NH4NO3 were found to be the major contributors to visibility impairment. High concentrations of sulfate and nitrate might be explained by homogeneous gas-phase reactions under low RH conditions and by heterogeneous processes under relatively high RH conditions. Analysis of air mass trajectory clustering and potential source contribution function showed that aerosol pollution in the studied areas was mainly caused by local activities and surrounding sources transported from nearby cities.

scholarly journals Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes

2019 ◽  
Vol 19 (1) ◽  
pp. 219-232 ◽  
Author(s):  
Xiaole Pan ◽  
Baozhu Ge ◽  
Zhe Wang ◽  
Yu Tian ◽  
Hang Liu ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Synergistic Effect ◽  
Mineral Dust ◽  
Water Soluble ◽  
Dust Particles ◽  
Urban Site ◽  
Chemical Compositions ◽  
Aerodynamic Diameter ◽  
Soluble Species ◽  
Pollution Episodes

Abstract. Depolarization ratio (δ) of backscattered light is an applicable parameter for distinguishing the sphericity of particles in real time, which has been widely adopted by ground-based lidar observation systems. In this study, δ values of particles and chemical compositions in both PM2.5 (aerodynamic diameter less than 2.5 µm) and PM10 (aerodynamic diameter less than 10 µm) were concurrently measured on the basis of a bench-top optical particle counter with a polarization detection module (POPC) and a continuous dichotomous aerosol chemical speciation analyzer (ACSA-14) from November 2016 to February 2017 at an urban site in Beijing megacity. In general, measured δ values depended on both size and sphericity of the particles. During the observation period, mass concentrations of NO3- in PM2.5 (fNO3) were about an order of magnitude higher than that in PM2.5−10 (cNO3) with a mean fNO3∕cNO3 ratio of 14±10. A relatively low fNO3∕cNO3 ratio (∼5) was also observed under higher relative humidity conditions, mostly due to heterogeneous processes and particles in the coarse mode. We found that δ values of ambient particles in both PM2.5 and PM2.5−10 obviously decreased as mass concentration of water-soluble species increased at unfavorable meteorological conditions. This indicated that the morphology of particles was changed as a result of water-absorbing processes. The particles with optical size (Dp) of Dp = 5 µm were used to represent mineral dust particles, and its δ values (δDp=5) decreased by 50 % as the mass fraction of cNO3 increased from 2 % to 8 % and ambient relative humidity increased up to 80 %, suggesting that mineral dust particles were likely to be spherical during humid pollution episodes. During the observation, relative humidity inside the POPC measuring chamber was stable at 34±2 %, lower than the ambient condition. Its influence on the morphology was estimated to be limited and did not change our major conclusion. This study highlights the evident alteration of non-sphericity of mineral dust particles during their transport owing to a synergistic effect of both pollutant coatings and hygroscopic processes, which plays an important role in the evaluation of its environmental effect.

scholarly journals Source apportionment of fine organic aerosol in Mexico City during the MILAGRO experiment 2006

2008 ◽  
Vol 8 (5) ◽  
pp. 1249-1259 ◽  
Author(s):  
E. A. Stone ◽  
D. C. Snyder ◽  
R. J. Sheesley ◽  
A. P. Sullivan ◽  
R. J. Weber ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Mexico City ◽  
Large Fraction ◽  
Optical Filter ◽  
Soxhlet Extraction ◽  
Water Soluble ◽  
Motor Vehicles ◽  
Balance Model ◽  
Urban Site ◽  
Peripheral Site

Abstract. Organic carbon (OC) comprises a large fraction of fine particulate matter (PM2.5) in Mexico City. Daily and select 12-h PM2.5 samples were collected in urban and peripheral sites in Mexico City from 17–30 March 2006. Samples were analyzed for OC and elemental carbon (EC) using thermal-optical filter-based methods. Real-time water-soluble organic carbon (WSOC) was collected at the peripheral site. Organic compounds, particularly molecular markers, were quantified by soxhlet extraction with methanol and dichloromethane, derivitization, and gas chromatography with mass spectrometric detection (GCMS). A chemical mass balance model (CMB) based on molecular marker species was used to determine the relative contribution of major sources to ambient OC. Motor vehicles, including diesel and gasoline, consistently accounted for 49% of OC in the urban area and 32% on the periphery. The daily contribution of biomass burning to OC was highly variable, and ranged from 5–26% at the urban site and 7–39% at the peripheral site. The remaining OC unapportioned to primary sources showed a strong correlation with WSOC and was considered to be secondary in nature. Comparison of temporally resolved OC showed that contributions from primary aerosol sources during daylight hours were not significantly different from nighttime. This study provides quantitative understanding of the important sources of OC during the MILAGRO 2006 field campaign.

scholarly journals Size-resolved particulate water-soluble organic compounds in the urban, mountain and marine atmosphere

2010 ◽  
Vol 10 (7) ◽  
pp. 17467-17490
Author(s):  
G. Wang ◽  
K. Kawamura ◽  
M. Xie ◽  
S. Hu ◽  
B. Zhou ◽  
...  
Keyword(s):  
Size Distribution ◽  
Organic Compounds ◽  
Fine Particles ◽  
Geometric Mean ◽  
Inversion Layer ◽  
Water Soluble ◽  
Urban Site ◽  
Marine Atmosphere ◽  
Marine Aerosols ◽  
Sugar Alcohols

Abstract. Primary (i.e., sugars and sugar alcohols) and secondary water-soluble organic compounds (WSOCs) (i.e., dicarboxylic acids and aromatic acids) were characterised on a molecular level in size-segregated aerosols from the urban and mountain atmosphere of China and from the marine atmosphere in the outflow region of East Asia. Levoglucosan is the most abundant WSOCs in the urban and mountain atmosphere, whose accumulated concentrations in all stages are 1–3 orders of magnitude higher than those of marine aerosols. In contrast, malic, succinic and phthalic acids are dominant in the marine aerosols, which are 3–6 times more abundant than levoglucosan. This suggests that a continuous formation of secondary organic aerosols is occurring in the marine atmosphere during the long-range transport of air mass from inland China to the North Pacific. Sugars and sugar-alcohols, except for levoglucosan, gave a bimodal size distribution in the urban and mountain areas, peaking at 0.7–1.1 μm and >3.3 μm, and a unimodal distribution in the marine region, peaking at >3.3 μm. In contrast, levoglucosan and all the secondary WSOCs, except for benzoic and azelaic acids, showed a unimodal size distribution with a peak at 0.7–1.1 μm. Geometric mean diameters (GMDs) of the WSOCs in fine particles (<2.1 μm) at the urban site are larger in winter than in spring, due to an enhanced coagulation effect under the development of an inversion layer. However, GMDs of levoglucosan and most of the secondary WSOCs in the coarse mode are larger in the mountain and marine air and smaller in the urban air. This is most likely caused by an enhanced hygroscopic growth due to the high humidity of the mountain and marine atmosphere.

scholarly journals Size-resolved aerosol water-soluble ionic compositions in the summer of Beijing: implication of regional secondary formation

2009 ◽  
Vol 9 (6) ◽  
pp. 23955-23986 ◽  
Author(s):  
S. Guo ◽  
M. Hu ◽  
Z. B. Wang ◽  
J. Slanina ◽  
Y. L. Zhao
Keyword(s):  
Fine Particles ◽  
Secondary Compounds ◽  
Water Soluble ◽  
Rural Site ◽  
Urban Site ◽  
Condensation Process ◽  
Pmf Model ◽  
Secondary Formation ◽  
Aerosol Pollution ◽  
Peking University

Abstract. To characterize aerosol pollution in Beijing, size-resolved aerosols were collected by MOUDIs during CAREBEIJING-2006 field campaign at Peking University (urban site) and Yufa (upwind rural site). Fine particle concentrations (PM1.8 by MOUDI) were 99.8±77.4 μg/m3 and 78.2±58.4 μg/m3, with PM1.8/PM10 ratios of 0.64±0.08 and 0.76±0.08 at PKU and Yufa, respectively, and secondary compounds accounted for more than 50% in fine particles. PMF model was used to resolve the particle modes. Three modes were resolved at Yufa, representing condensation, droplet and coarse mode. However, one more droplet mode with bigger size was resolved, which was considered probably from regional transport. Condensation mode accounted for 10%–60% of the total mass at both sites, indicating it must be taken into account in summer. The formation of sulfate was mainly attributed to in-cloud or aerosol droplet process (PKU 80%, Yufa 70%) and gas condensation process (PKU 14%, Yufa 22%). According to the thermodynamic instability of NH4NO3, size distributions of nitrate were classified as three categories by RH. The existence of Ca(NO3)2 in droplet mode indicated the reaction of HNO3 with crustal particles was also important in fine particles. Linear regression gave a rough estimation that 69% of the PM10 and 87% of the PM1.8 at PKU were regional contributions. Sulfate, ammonium and oxalate were formed regionally, with the regional contributions of 90%, 87% and 95% to PM1.8. Nitrate formation was local dominant. In summary regional secondary formation led to aerosol pollution in the summer of Beijing.

scholarly journals Source apportionment of carbonaceous aerosols in Beijing with radiocarbon and organic tracers: insight into the differences between urban and rural sites

2021 ◽  
Vol 21 (10) ◽  
pp. 8273-8292
Author(s):  
Siqi Hou ◽  
Di Liu ◽  
Jingsha Xu ◽  
Tuan V. Vu ◽  
Xuefang Wu ◽  
...  
Keyword(s):  
Source Apportionment ◽  
Biomass Burning ◽  
Fine Particles ◽  
Water Soluble ◽  
Carbonaceous Aerosol ◽  
Balance Model ◽  
Gas Chromatography Mass Spectrometry ◽  
Urban Site ◽  
Carbonaceous Aerosols ◽  
Carbonaceous Particles

Abstract. Carbonaceous aerosol is a dominant component of fine particles in Beijing. However, it is challenging to apportion its sources. Here, we applied a newly developed method which combined radiocarbon (14C) with organic tracers to apportion the sources of fine carbonaceous particles at an urban (IAP) and a rural (PG) site of Beijing. PM2.5 filter samples (24 h) were collected at both sites from 10 November to 11 December 2016 and from 22 May to 24 June 2017. 14C was determined in 25 aerosol samples (13 at IAP and 12 at PG) representing low pollution to haze conditions. Biomass burning tracers (levoglucosan, mannosan, and galactosan) in the samples were also determined using gas chromatography–mass spectrometry (GC-MS). Higher contributions of fossil-derived OC (OCf) were found at the urban site. The OCf / OC ratio decreased in the summer samples (IAP: 67.8 ± 4.0 % in winter and 54.2 ± 11.7 % in summer; PG: 59.3 ± 5.7 % in winter and 50.0 ± 9.0 % in summer) due to less consumption of coal in the warm season. A novel extended Gelencsér (EG) method incorporating the 14C and organic tracer data was developed to estimate the fossil and non-fossil sources of primary and secondary OC (POC and SOC). It showed that fossil-derived POC was the largest contributor to OC (35.8 ± 10.5 % and 34.1 ± 8.7 % in wintertime for IAP and PG, 28.9 ± 7.4 % and 29.1 ± 9.4 % in summer), regardless of season. SOC contributed 50.0 ± 12.3 % and 47.2 ± 15.5 % at IAP and 42.0 ± 11.7 % and 43.0 ± 13.4 % at PG in the winter and summer sampling periods, respectively, within which the fossil-derived SOC was predominant and contributed more in winter. The non-fossil fractions of SOC increased in summer due to a larger biogenic component. Concentrations of biomass burning OC (OCbb) are resolved by the extended Gelencsér method, with average contributions (to total OC) of 10.6 ± 1.7 % and 10.4 ± 1.5 % in winter at IAP and PG and 6.5 ± 5.2 % and 17.9 ± 3.5 % in summer, respectively. Correlations of water-insoluble OC (WINSOC) and water-soluble OC (WSOC) with POC and SOC showed that although WINSOC was the major contributor to POC, a non-negligible fraction of WINSOC was found in SOC for both fossil and non-fossil sources, especially during winter. In summer, a greater proportion of WSOC from non-fossil sources was found in SOC. Comparisons of the source apportionment results with those obtained from a chemical mass balance model were generally good, except for the cooking aerosol.

scholarly journals Source apportionment of fine organic carbon at an urban site of Beijing using a chemical mass balance model

2021 ◽  
Vol 21 (9) ◽  
pp. 7321-7341
Author(s):  
Jingsha Xu ◽  
Di Liu ◽  
Xuefang Wu ◽  
Tuan V. Vu ◽  
Yanli Zhang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Mass Balance ◽  
Source Apportionment ◽  
Biomass Burning ◽  
Coal Combustion ◽  
Fine Particles ◽  
Inorganic Ions ◽  
Balance Model ◽  
Urban Site ◽  
Chemical Mass Balance

Abstract. Fine particles were sampled from 9 November to 11 December 2016 and 22 May to 24 June 2017 as part of the Atmospheric Pollution and Human Health in a Chinese Megacity (APHH-China) field campaigns in urban Beijing, China. Inorganic ions, trace elements, organic carbon (OC), elemental carbon (EC), and organic compounds, including biomarkers, hopanes, polycyclic aromatic hydrocarbons (PAHs), n-alkanes, and fatty acids, were determined for source apportionment in this study. Carbonaceous components contributed on average 47.2 % and 35.2 % of total reconstructed PM2.5 during the winter and summer campaigns, respectively. Secondary inorganic ions (sulfate, nitrate, ammonium; SNA) accounted for 35.0 % and 45.2 % of total PM2.5 in winter and summer. Other components including inorganic ions (K+, Na+, Cl−), geological minerals, and trace metals only contributed 13.2 % and 12.4 % of PM2.5 during the winter and summer campaigns. Fine OC was explained by seven primary sources (industrial and residential coal burning, biomass burning, gasoline and diesel vehicles, cooking, and vegetative detritus) based on a chemical mass balance (CMB) receptor model. It explained an average of 75.7 % and 56.1 % of fine OC in winter and summer, respectively. Other (unexplained) OC was compared with the secondary OC (SOC) estimated by the EC-tracer method, with correlation coefficients (R2) of 0.58 and 0.73 and slopes of 1.16 and 0.80 in winter and summer, respectively. This suggests that the unexplained OC by the CMB model was mostly associated with SOC. PM2.5 apportioned by the CMB model showed that the SNA and secondary organic matter were the two highest contributors to PM2.5. After these, coal combustion and biomass burning were also significant sources of PM2.5 in winter. The CMB results were also compared with results from the positive matrix factorization (PMF) analysis of co-located aerosol mass spectrometer (AMS) data. The CMB model was found to resolve more primary organic aerosol (OA) sources than AMS-PMF, but the latter could apportion secondary OA sources. The AMS-PMF results for major components, such as coal combustion OC and oxidized OC, correlated well with the results from the CMB model. However, discrepancies and poor agreements were found for other OC sources, such as biomass burning and cooking, some of which were not identified in AMS-PMF factors.

scholarly journals Impact of particle number and mass size distributions of major chemical components on particle mass scattering efficiency in urban Guangzhou in southern China

2019 ◽  
Vol 19 (13) ◽  
pp. 8471-8490 ◽  
Author(s):  
Jun Tao ◽  
Zhisheng Zhang ◽  
Yunfei Wu ◽  
Leiming Zhang ◽  
Zhijun Wu ◽  
...  
Keyword(s):  
Size Distribution ◽  
Southern China ◽  
Chemical Species ◽  
Particle Mass ◽  
Urban Site ◽  
Chemical Compositions ◽  
Scattering Efficiency ◽  
Coarse Mode ◽  
Major Chemical ◽  
Mass Concentrations

Abstract. To grasp the key factors affecting particle mass scattering efficiency (MSE), particle mass and number size distribution, PM2.5 and PM10 and their major chemical compositions, and the particle scattering coefficient (bsp) 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 PM10 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, (NH4)2SO4, NH4NO3, and crustal element oxides in the droplet mode, and crustal element oxides, OM, and CaSO4 in the coarse mode, were the dominant chemical species in their respective modes. The measured bsp can be reconstructed to the level of 91±10 % using Mie theory with input of the estimated chemically resolved number concentrations of NaCl, NaNO3, Na2SO4, NH4NO3, (NH4)2SO4, K2SO4, CaSO4, Ca(NO3)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 bsp and chemical species mass concentrations. Seasonal average MSEs varied in the range of 3.5±0.1 to 3.9±0.2 m2 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, NH4NO3, (NH4)2SO4) in the droplet mode. MSEs of the dominant chemical species were determined by their lognormal size-distribution parameters, including MMADs and standard deviation (σ) in the droplet mode.

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