Yuanhang Zhang

Peking University, Peping, Beijing, China

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Publications (95)296.56 Total impact

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    ABSTRACT: Size distributions and chemical components of particles are crucial in assessing the environmental effects of aerosol. Size-resolved aerosol samples were collected by MOUDI in four seasons in 2007 in Beijing. The PM10 and PM1.8 mass concentrations were 166.0 ± 120.5 and 91.6 ± 69.7 μg/m3, respectively, throughout the measurement, with striking seasonal variation: nearly two times higher in autumn than in summer and spring. Serious fine particle pollution occurred in winter with the PM1.8/PM10 ratio of 0.63, which was higher than other seasons. The size distribution of PM showed obvious seasonal and diurnal variation, with a smaller fine mode peak in spring and in the daytime. OM (organic matter = 1.6 × OC (organic carbon)) and SIA (secondary inorganic aerosol) were major components of fine particles, while OM, SIA and Ca2 + were major components in coarse particles. Moreover, secondary components, mainly SOA (secondary organic aerosol) and SIA, accounted for 46%–96% of each size bin in fine particles, which meant that secondary pollution existed all year. Sulfates and nitrates, primarily in the form of (NH4)2SO4, NH4NO3, CaSO4, Na2SO4 and K2SO4, calculated by the model ISORROPIA II, were major components of the solid phase in fine particles. The PM concentration and size distribution were similar in the four seasons on non-haze days, while large differences occurred on haze days, which indicated seasonal variation of PM concentration and size distribution were dominated by haze days. The SIA concentrations and fractions of nearly all size bins were higher on haze days than on non-haze days, which was attributed to heterogeneous aqueous reactions on haze days in the four seasons.
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    ABSTRACT: In recent years, fine particulate matter (PM) pollution and visibility degradation have become severe air quality issues in China. In this study, PM2.5 pollution over the Pearl River Delta (PRD) region during January, April, August, and November 2009 was simulated using the Community Multiscale Air Quality (CMAQ) model. An in-depth diagnostic analysis, focused on November 2009, was also conducted to reveal the patterns of sulfate and nitrate distribution, and to identify the main factors that influence the formation of sulfate and nitrate under typical meteorological conditions. The CMAQ model reasonably reproduced the observed concentrations, but showed better performance for January and November than it did for April and August, for which there was light-moderate underestimation of SO2, NOx, O3, PM10, and PM2.5 concentrations, and slight overestimation of daily 8-hr maximum concentrations of O3. Utilizing a sulfate tracking technique, it was found that on nearly 20 days in November 2009, characterized by northeasterly winds, cross-boundary transport contributed to >75% of the total sulfate budget, while local gas phase oxidation and primary emissions averaged 10% and 8%, respectively. Aqueous sulfate typically contributed less than 1% of the total sulfate budget, except when the winds were directed from the sea and high humidity favored aqueous oxidation, and the percentage contribution reached up to 46%. NH3 was generally sufficient to fully neutralize H2SO4; however, the formation of nitrate over the PRD was limited by the availability of NH3.
    Atmospheric Environment 04/2015; 112. DOI:10.1016/j.atmosenv.2015.04.027 · 3.06 Impact Factor
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    ABSTRACT: It is not known whether exposure to air pollutants causes systemic oxidative stress in children. We investigated the association between exposure to air pollution and biomarkers of oxidative stress in relation to a governmental air quality intervention implemented during the 2008 Beijing Olympic Games. We studied 36 schoolchildren during 5 time periods before and during the Olympic Games in Beijing (June 2007-September 2008). The oxidative stress biomarkers 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and malondialdehyde were measured in urine samples collected daily during each period. Generalized estimating equations were used to examine the relationship between repeated biomarker measurements and ambient air pollutant levels. During the Olympic intervention period, substantial reductions in air pollution (-19% to -72%), urinary 8-oxodG concentrations (-37.4%; 95% confidence interval: -53.5, -15.7), and urinary malondialdehyde concentrations (-25.3%; 95% confidence interval: -34.3, -15.1) were found. Malondialdehyde and 8-oxodG were significantly associated with concentrations of black carbon, fine particulate matter with an aerodynamic with diameter less than 2.5 μm, sulfur dioxide, nitrogen dioxide, and carbon monoxide. Biomarker changes per each interquartile-range increase in pollutants were largest at lag 0 or lag 1. In a 2-pollutant model, the most robust associations were for black carbon. These findings suggest that exposure to black carbon leads to systemic oxidative stress in children. © The Author 2015. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
    American Journal of Epidemiology 03/2015; 181(8). DOI:10.1093/aje/kwu327 · 4.98 Impact Factor
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    ABSTRACT: A field experiment from 18 August to 8 September 2006 in Beijing, China, was carried out to study the role of secondary aerosols in haze formation in the megacity. A hazy day was defined as visibility < l0 km and RH (relative humidity) < 90%. Four haze episodes, which accounted for ~ 60% of the time during the whole campaign, were characterized by increases of SNA (sulfate, nitrate, and ammonium) and SOA (secondary organic aerosol) concentrations. The average values with standard deviation of SO42 −, NO3−, NH4+ and SOA were 49.8 (± 31.6), 31.4 (± 22.3), 25.8 (± 16.6) and 8.9 (± 4.1) μg/m3, respectively, during the haze episodes, which were 4.3, 3.4, 4.1, and 1.7 times those in the non-haze days. The SO42 −, NO3−, NH4+, and SOA accounted for 15.8%, 8.8%, 7.3%, and 6.0% of the total mass concentration of PM10 during the non-haze days. The respective contributions of SNA species to PM10 rose to about 27.2%, 15.9%, and 13.9% during the haze days, while the contributions of SOA maintained the same level with a slight decrease to about 4.9%. The observed mass concentrations of SNA and SOA increased with the increase of PM10 mass concentration, however, the rate of increase of SNA was much faster than that of the SOA. The SOR (sulfur oxidation ratio) and NOR (nitrogen oxidation ratio) increased from non-haze days to hazy days, and increased with the increase of RH. High concentrations of aerosols and water vapor favored the conversion of SO2 to SO42 − and NO2 to NO3−, which accelerated the accumulation of the aerosols and resulted in the formation of haze in Beijing.
    Journal of Environmental Sciences 03/2015; 31. DOI:10.1016/j.jes.2014.08.026 · 1.92 Impact Factor
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    ABSTRACT: Marine aerosols over the East China Seas are heavily polluted by continental sources. During the Chinese Comprehensive Ocean Experiment in November 2012, size and mass spectra of individual atmospheric particles in the size range from 0.2 to 2.0μm were measured on board by a single particle aerosol mass spectrometer (SPAMS). The average hourly particle number (PN) was around 4560±3240 in the South Yellow Sea (SYS), 2900±3970 in the North Yellow Sea (NYS), and 1700±2220 in the Bohai Sea (BS). PN in NYS and BS varied greatly over 3 orders of magnitude, while that in SYS varied slightly. The size distributions were fitted with two log-normal modes. Accumulation mode dominated in NYS and BS, especially during episodic periods. Coarse mode particles played an important role in SYS. Particles were classified using an adaptive resonance theory based neural network algorithm (ART-2a). Six particle types were identified with secondary-containing, aged sea-salt, soot-like, biomass burning, fresh sea-salt, and lead-containing particles accounting for 32%, 21%, 18%, 16%, 4%, and 3% of total PN, respectively. Aerosols in BS were relatively enriched in particles from anthropogenic sources compared to SYS, probably due to emissions from more developed upwind regions and indicating stronger influence of continental outflow on marine environment. Variation of source types depended mainly on origins of transported air masses. This study examined rapid changes in PN, size distribution and source types of fine particles in marine atmospheres. It also demonstrated the effectiveness of high-time-resolution source apportionment by ART-2a. Copyright © 2015. Published by Elsevier B.V.
    Journal of Environmental Sciences 01/2015; 29. DOI:10.1016/j.jes.2014.09.031 · 1.92 Impact Factor
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    Chinese Journal 01/2015; 60(2):109. DOI:10.1360/N972014-00975
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    ABSTRACT: Size-resolved aerosols were continuously collected by a Nano Sampler for 13 days at an urban site in Beijing during winter 2012 to measure the chemical composition of ambient aerosol particles. Data collected by the Nano Sampler and an ACSM (Aerodyne Aerosol Chemical Speciation Monitor) were compared. Between the data sets, similar trends and strong correlations were observed, demonstrating the validity of the Nano Sampler. PM10 and PM2.5 concentrations during the measurement were 150.5 ± 96.0 μg/m3 (mean ± standard variation) and 106.9 ± 71.6 μg/m3, respectively. The PM2.5/PM10 ratio was 0.70 ± 0.10, indicating that PM2.5 dominated PM10. The aerosol size distributions showed that three size bins of 0.5–1, 1–2.5 and 2.5–10 μm contributed 21.8%, 23.3% and 26.0% to the total mass concentration (TMC), respectively. OM (organic matter) and SIA (secondary ionic aerosol, mainly SO42 −, NO3− and NH4+) were major components of PM2.5. Secondary compounds (SIA and secondary organic carbon) accounted for half of TMC (about 49.8%) in PM2.5, and suggested that secondary aerosols significantly contributed to the serious particulate matter pollution observed in winter. Coal burning, biomass combustion, vehicle emissions and SIA were found to be the main sources of PM2.5. Mass concentrations of water-soluble ions and undetected materials, as well as their fractions in TMC, strikingly increased with deteriorating particle pollution conditions, while OM and EC (elemental carbon) exhibited different variations, with mass concentrations slightly increasing but fractions in TMC decreasing.
    Journal of Environmental Sciences 08/2014; 26(8). DOI:10.1016/j.jes.2014.06.004 · 1.92 Impact Factor
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    ABSTRACT: The removal of trace gases from the troposphere is, in most cases, initialized by reactions with hydroxyl radicals, and the products of these reactions are eventually deposited on the Earth's surface. The concentration of these hydroxyl radicals is therefore a measure of atmospheric self-cleansing. In theory, hydroxyl-radical concentrations can be enhanced by the recycling of some of the reaction products. The only known efficient recycling process involves nitrogen oxide and leads to production of ozone, yet observations in regions with high hydrocarbon and low nitrogen oxide concentrations show substantially elevated hydroxyl-radical concentrations, up to ten times higher than expected. If we normalize observed hydroxyl-radical concentrations to the maximum achievable in model calculations with variable nitrogen oxide concentrations, this photochemical coordinate system uncovers a common feature in almost all of these observations: even in the presence of inadequate amounts of nitrogen oxides, hydroxyl-radical concentrations are enhanced to the theoretical maximum obtainable at very much higher nitrogen oxide concentrations. This means that this important part of the self-cleansing capability of the atmosphere is working at maximum efficiency even in regions with a high burden of biogenic hydrocarbons and low nitrogen oxide concentration. Since these processes do not involve nitrogen oxides, tropospheric ozone production is greatly reduced compared with the expectation from current theory.
    Nature Geoscience 07/2014; 7(8):559-563. DOI:10.1038/ngeo2199 · 11.67 Impact Factor
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    ABSTRACT: Nitrous acid (HONO), as a primary precursor of OH radicals, has been considered one of the most important nitrogen-containing species in the atmosphere. Up to 30% of primary OH radical production is attributed to the photolysis of HONO. However, the major HONO formation mechanisms are still under discussion. During the Campaigns of Air Quality Research in Beijing and Surrounding Region (CAREBeijing2006) campaign, comprehensive measurements were carried out in the megacity Beijing, where the chemical budget of HONO was fully constrained. The average diurnal HONO concentration varied from 0.33 to 1.2 ppbv. The net OH production rate from HONO, P OH(HONO)net, was on average (from 05:00 to 19:00 h) 7.1 × 106 molecule/(cm3 s), 2.7 times higher than from O3 photolysis. This production rate demonstrates the important role of HONO in the atmospheric chemistry of megacity Beijing. An unknown HONO source (P unknown) with an average of 7.3 × 106 molecule/(cm3 s) was derived from the budget analysis during daytime. P unknown provided four times more HONO than the reaction of NO with OH did. The diurnal variation of P unknown showed an apparent photo-enhanced feature with a maximum around 12:00 h, which was consistent with previous studies at forest and rural sites. Laboratory studies proposed new mechanisms to recruit NO2 and J(NO2) in order to explain a photo-enhancement of of P unknown. In this study, these mechanisms were validated against the observation-constraint P unknown. The reaction of exited NO2 accounted for only 6% of P unknown, and P unknown poorly correlated with [NO2] (R = 0.26) and J(NO2)[NO2] (R = 0.35). These results challenged the role of NO2 as a major precursor of the missing HONO source.
    Science China-Chemistry 07/2014; 57(7):1032-1042. DOI:10.1007/s11426-013-5044-0 · 1.52 Impact Factor
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    ABSTRACT: With rapid economic development and the acceleration of urbanization, air pollution has become a serious problem in the mega-city Guangzhou, China. A field campaign to sample and analyze particulate matter (PM) chemical components was performed from July 6, 2006 to July 26, 2006, in Guangzhou. During the campaign, the average mass concentration of PM10 was 89.0 ± 46.6 μg m− 3 (the error represents one standard deviation). The PM10, sulfate, nitrate, ammonium, organic carbon (OC), and elemental carbon (EC) mass frequency distributions were analyzed. The [NO3−]/[SO42 −] mass ratio varied from 0.1 to 0.3, with an average of 0.2. A Pearson correlation analysis between [SO42 −] and [NH4+] and between [NO3−] and [Na+] showed that SO42 − existed as (NH4)2SO4 and NO3− existed as NH4NO3 and NaNO3. Sulfate, nitrate, ammonium, EC and POM (particulate organic matter) accounted for 24.4%, 4.9%, 5.7%, 5.7% and 21.0%, respectively, of the PM10 mass concentration during clean days and 25.7%, 3.9%, 7.9%, 5.4% and 20.8%, respectively, on hazy days. Among these species, SNA (sulfate, nitrate, and ammonium) were the most abundant, accounting for 35.0% and 37.5% of the PM10 during clean and hazy days, respectively. The sum of POM and EC accounted for 26.7% and 26.2% of PM10 in Guangzhou during clean and hazy days, respectively. There was no apparent difference in the chemical composition of PM10 between clean and haze days.
    Atmospheric Research 02/2014; 137:25–34. DOI:10.1016/j.atmosres.2013.10.004 · 2.42 Impact Factor
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    ABSTRACT: This study was conceived to evaluate the global scientific output of secondary organic aerosol (SOA) research and to assess the characteristics of the research patterns, tendencies, and methods in the papers. Data were based on the online version of Science Citation Index Expanded from 1990 to 2013. Publications referring to SOA were assessed by distribution of the number of publications and times cited, source journals, h-index, and the most cited publications in these years. By synthetic analysis of author keywords, KeyWords Plus, titles, and abstracts, it was concluded that modeling is currently and will at least over the next decade continue to be the predominant research method to validate state-of-the-art knowledge of SOA, and that the foci of SOA research will be the key precursors terpenes, isoprene, and dicarbonyls; the mechanisms of oxidation and aqueous-phase reactions; emission inventories; and chemical composition. Recent years show growing interest for research on health effects.
    Pure and Applied Chemistry 01/2014; 86(7):1169-75. DOI:10.1515/pac-2014-0204 · 3.11 Impact Factor
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    ABSTRACT: Based on the observation by a Regional Air Quality Monitoring Network including 16 monitoring stations, temporal and spatial variations of ozone (O3), NO2 and total oxidant (Ox) were analyzed by both linear regression and cluster analysis. A fast increase of regional O3 concentrations of 0.86 ppbV/yr was found for the annual averaged values from 2006 to 2011 in Guangdong, China. Such fast O3 increase is accompanied by a correspondingly fast NOx reduction as indicated by a fast NO2 reduction rate of 0.61 ppbV/yr. Based on a cluster analysis, the monitoring stations were classified into two major categories – rural stations (non-urban) and suburban/urban stations. The O3 concentrations at rural stations were relatively conserved while those at suburban/urban stations showed a fast increase rate of 2.0 ppbV/yr accompanied by a NO2 reduction rate of 1.2 ppbV/yr. Moreover, a rapid increase of the averaged O3 concentrations in springtime (13%/yr referred to 2006 level) was observed, which may result from the increase of solar duration, reduction of precipitation in Guangdong and transport from Eastern Central China. Application of smog production algorithm showed that the photochemical O3 production is mainly volatile organic compounds (VOC)-controlled. However, the photochemical O3 production is sensitive to both NOx and VOC for O3 pollution episode. Accordingly, it is expected that a combined NOx and VOC reduction will be helpful for the reduction of the O3 pollution episodes in Pearl River Delta while stringent VOC emission control is in general required for the regional O3 pollution control.
    01/2014; 26(1-1):23-36. DOI:10.1016/S1001-0742(13)60377-0
  • Qi Wang, Qiaoling Liu, Min Shao, Yuanhang Zhang
    Energy & Environment 12/2013; 24(7):1373-1392. DOI:10.1260/0958-305X.24.7-8.1373 · 0.15 Impact Factor
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    ABSTRACT: In situ measurements of size-resolved aerosol chemical compositions and its optical properties were concurrently carried out at an urban site in mega-city Beijing from October 24 to November 9, 2007. The main objective was to quantitatively study the relationship between aerosol chemical compositions and its hygroscopic properties, to estimate the influence of relative humidity (RH) on aerosol scattering coefficient and to quantitatively investigate visibility impairment due to particle hygroscopic growth. The hygroscopic factor of aerosol scattering coefficient (f(RH)), which is defined as the ratio of aerosol scattering coefficient at wet condition to that at dry condition (RH ≤ 30%), was calculated with the measured aerosol optical properties at dry and ambient conditions. The relationship between f(RH) and RH was fitted by empirical equation and the fitting parameters were calculated. Meanwhile, f(RH) for externally mixed aerosols or internally mixed aerosols was modeled based on size segregated particulate chemical composition. The modeled f(RH) agreed well with the measured f(RH). Empirical formula for atmospheric visibility based on mass concentration of PM2.5 and f(RH) was proposed. The result of this study is not only proven that RH, in addition to the mass concentration of PM2.5, played an important role on visibility impairment, but also provide practical aid for air quality control to improve the visibility in the megacity region of Beijing.
    Atmospheric Research 10/2013; s 132–133:91–101. DOI:10.1016/j.atmosres.2013.04.007 · 2.42 Impact Factor
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    ABSTRACT: PM2.5 is the key pollutant in atmospheric pollution in China. With new national air quality standards taking effect, PM2.5 has become a major issue for future pollution control. To effectively prevent and control PM2.5, its emission sources must be precisely and thoroughly understood. However, there are few publications reporting comprehensive and systematic results of PM2.5 source apportionment in the country. Based on PM2.5 sampling during 2009 in Shenzhen and follow-up investigation, positive matrix factorization (PMF) analysis has been carried out to understand the major sources and their temporal and spatial variations. The results show that in urban Shenzhen (University Town site), annual mean PM2.5 concentration was 42.2 μg m−3, with secondary sulfate, vehicular emission, biomass burning and secondary nitrate as major sources; these contributed 30.0%, 26.9%, 9.8% and 9.3% to total PM2.5, respectively. Other sources included high chloride, heavy oil combustion, sea salt, dust and the metallurgical industry, with contributions between 2%–4%. Spatiotemporal variations of various sources show that vehicular emission was mainly a local source, whereas secondary sulfate and biomass burning were mostly regional. Secondary nitrate had both local and regional sources. Identification of secondary organic aerosol (SOA) has always been difficult in aerosol source apportionment. In this study, the PMF model and organic carbon/elemental carbon (OC/EC) ratio method were combined to estimate SOA in PM2.5. The results show that in urban Shenzhen, annual SOA mass concentration was 7.5 μg m−3, accounting for 57% of total organic matter, with precursors emitted from vehicles as the major source. This work can serve as a case study for further in-depth research on PM2.5 pollution and source apportionment in China.
    Science China Earth Science 06/2013; 57(6):1352-1362. DOI:10.1007/s11430-013-4686-2 · 1.34 Impact Factor
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    ABSTRACT: A new instrument for measuring atmospheric nitrous acid (HONO) was developed, consisting of a double-wall glass stripping coil sampler coupled with ion chromatography (SC-IC). SC-IC is featured by small size (50 x 35 x 25 cm) and modular construction, including three independent parts: the sampling unit, the transfer and supporting unit, and the detection unit. High collection efficiency (> 99%) was achieved with 25 micromol/L Na2CO3 as absorption solution even in the presence of highly acidic compounds. This instrument has a detection limit of 8 pptv at 15 min time resolution, with a measurement uncertainty of 7%. Potential interferences from NO(x), NO2+SO2, NO2+VOCs, HONO+O3, HNO3, peroxyacetyl nitrite (PAN) and particle nitrite were quantified in laboratory studies and were found to be insignificant under typical atmospheric conditions. Within the framework of the 3C-STAR project, inter-comparison between the SC-IC and LOPAP (long path liquid absorption photometer) was conducted at a rural site in the Pearl River Delta. Good agreement was achieved between the two instruments over three weeks. Both instruments determined a clear diurnal profile of ambient HONO concentrations from 0.1 to 2.5 ppbv. However, deviations were found for low ambient HONO concentrations (i.e. < 0.3 ppbv), which cannot be explained by previous investigated interference species. To accurately determine the HONO budget under illuminated conditions, more intercomparison of HONO measurement techniques is still needed in future studies, especially at low HONO concentrations.
    Journal of Environmental Sciences 05/2013; 25(5):895-907. DOI:10.1016/S1001-0742(12)60251-4 · 1.92 Impact Factor
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    Pure and Applied Chemistry 01/2013; 85(6):1241-55. DOI:10.1351/PAC-REP-12-08-09 · 3.11 Impact Factor
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    ABSTRACT: This study was conceived to evaluate the global scientific output of secondary organic aerosol (SOA) research over the past 20 years and to assess the characteristics of the research patterns, tendencies, and methods in the papers. Data were based on the online version of Science Citation Index Expanded from 1992 to 2011. Publications referring to SOAs were assessed by distribution of the number of publications and times cited, source categories, source journals, author keywords, KeyWords Plus, and the most cited publications in these years. By synthetic analysis of author keywords, KeyWords Plus, titles, and abstracts, it was concluded that modeling is currently and will at least over the next decade continue to be the predominant research method to validate state-of-the-art knowledge of SOAs, and that the foci of SOA research will be the key precursors terpenes and isoprene, the mechanisms of oxidation and gas-phase reactions, and emission inventories.
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    ABSTRACT: The objective of this study is to quantify the relation of aerosol chemical compositions and optical properties, and to assess the impact of relative humidity (RH) on atmospheric visibility and aerosol direct radiative forcing (ADRF). Mass concentration and size distribution of aerosol chemical compositions as well as aerosol optical properties were concurrently measured at Guangzhou urban site during the PRD (Pearl River Delta) campaign from 1 to 31 July, 2006. Gaseous pollutant NO2 and meteorological parameter were simultaneously monitored. Compared with its dry condition, atmospheric ambient extinction coefficient σext(RH) averagely increased about 51% and atmospheric visibility deceased about 35%, among which RH played an important role on the optical properties of water soluble inorganic salts. (NH4)2SO4 is the most important component responsible for visibility degradation at Guangzhou. In addition, the asymmetry factor g increased from 0.64 to 0.74 with the up-scatter fraction β decreasing from 0.24 to 0.19 when RH increasing from 40% to 90%. At 80% RH, the ADRF increased about 280% compared to that at dry condition and it averagely increased about 100% during the campaign under ambient conditions. It can be inferred that aerosol water content is a key factor and could not be ignored in assessing the role of aerosols in visibility impairment and radiative forcing, especially in the regions with high RH.
    Atmospheric Environment 12/2012; 60:59–67. DOI:10.1016/j.atmosenv.2012.06.016 · 3.06 Impact Factor