Atmospheric Environment (v.123, #PB)

Characteristics and seasonal variation of organic matter in PM2.5 at a regional background site of the Yangtze River Delta region, China by Jialiang Feng; Junchao Hu; Binhua Xu; Xiaoling Hu; Peng Sun; Wenliang Han; Zeping Gu; Xiangming Yu; Minghong Wu (288-297).
One hundred and ten seasonal PM2.5 samples were collected at Lin'an (LA), a regional background site in the Yangtze River Delta (YRD) region of China, to study the chemical composition, seasonal variation and sources of carbonaceous aerosols in the YRD region. Concentrations of organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC) and composition of solvent-extractable organic compounds (SEOC) including n-alkanes, hopanes, PAHs, n-fatty acids and levoglucosan were analyzed. Back trajectory and potential source contribution function (PSCF) analysis were conducted to identify the possible source areas of PM2.5 at LA. PM2.5 concentration at LA ranged from 15.7 μg m−3 to 182.1 μg m−3, with an annual average of 59.7 μg m−3. A large part of the total carbon (OC + EC, 11.8 μg m−3) was water-soluble (42% in winter and spring, 56% in summer and 49% in autumn). SEOC concentration showed distinct seasonal variation of higher in winter and lower in summer. The average concentrations of n-alkanes and PAHs in winter (105 ng m−3 and 55 ng m−3 respectively) were 5 and 8 times of that in summer. Diagnostic ratios of PAHs and PSCF analysis suggested that vehicle emission was not the main source of PAHs at LA. Based on the levoglucosan concentration (annual average of 136 ng m−3), more than 15% of the OC at LA was from biomass burning. This data set provides useful information for the understanding of the characteristics of PM2.5 in the YRD region.
Keywords: PM2.5; Carbonaceous aerosol; Organic tracer; Lin'an; Yangtze River Delta; PSCF;

PM2.5 pollution episode and its contributors from 2011 to 2013 in urban Shanghai, China by H.L. Wang; L.P. Qiao; S.R. Lou; M. Zhou; J.M. Chen; Q. Wang; S.K. Tao; C.H. Chen; H.Y. Huang; L. Li; C. Huang (298-305).
Shanghai has suffered from severe fine particle (PM2.5) pollution in recent years. The characterization and formation mechanism of PM2.5 pollution episodes were investigated in the present study based on 3-year on-line measurements of PM2.5 chemical compositions with the temporal resolution of 1 h from 2011 to 2013 in Shanghai. Pollution episodes with PM2.5 mass higher than 75 μg/m3 occurred ∼1400 h annually, which inserted the annual extra PM2.5 mass of 14 μg/m3 into the level of 33 μg/m3 without pollution episodes taken into account. Three kinds of typical episodes were identified as biomass burning events, suspended dust events, and fireworks events, which extra contributed ∼1.5 μg/m3 relative to PM2.5 mass of clean periods. Most of pollution episodes were attributed to multiple and complex mechanisms, characterized by high contribution of the secondary inorganic components (e.g. nitrate, sulfate and ammonium) and carbonaceous matters, which dominated the monthly variations of PM2.5 mass. During the complex episodes, the increasing contribution of nitrate mass concentration to PM2.5 burden was observed. The present study highlighted the necessity to pay more attention to the secondary pollution. The reduction of precursor gases emissions was essential to mediate the severe PM2.5 pollution in Shanghai megacity.
Keywords: PM2.5 pollution episode; Chemical characterization; Formation mechanism; Contribution; Shanghai;

A year-long PM1 samples were collected at ECUST campus from April 2013 to February 2014 in urban Shanghai, China. Annual PM1 was (49.8 ± 31.8) μgm−3, comprising of water soluble organic carbon (WSOC), humic-like substances-carbon (Hulis-C), total water soluble inorganic ions (WSIIs) and liquid water content (LWC). Corresponding values were (5.51 ± 3.72) μgm−3, (2.20 ± 1.71) μgm−3, (22.52 ± 15.22) μgm−3 and (19.0 ± 19.2) μgm−3, respectively. Seasonal variation of PM1 was winter > spring > autumn > summer, while WSOC, Hulis-C, total WSIIs and LWC were highest in winter, with insignificant differences between spring, summer and autumn. Hulis-C and WSOC in PM1 on the serious haze day were found to be 4.4 and 2.5 times higher than those on the clear days, implying that Hulis might be very important for haze pollution. Among total WSIIs, sulfate was more abundant than nitrate on clear days while nitrate eventually surpassed sulfate in haze episodes. LWC in aerosol was significantly negative correlated with visibility and had strong relationship with nitrate and sulfate. It should be noted that LWC is four times sensitive to nitrate than sulfate, hence higher nitrate on haze days in Shanghai might facilitate the hygroscopic growth of aerosol.
Keywords: PM1; Water soluble organic carbon (WSOC); Humic like substances (Hulis); Water soluble inorganic ions (WSIIs); Liquid water content (LWC); Haze episodes;

Seasonal variation and difference of aerosol optical properties in columnar and surface atmospheres over Shanghai by Tiantao Cheng; Chen Xu; Junyan Duan; Yifan Wang; Chunpeng Leng; Jun Tao; Huizheng Che; Qianshan He; Yunfei Wu; Renjian Zhang; Xiang Li; Jianmin Chen; Lingdong Kong; Xingna Yu (315-326).
Aerosol optical properties in columnar and surface atmospheres were measured at an urban station of Shanghai from December 2010 to October 2012, and their seasonal variations and differences were examined. Aerosol optical thickness (AOT) at 500 nm is on average about 0.72 over the entire campaign, relatively higher in spring and summer and lower in autumn and winter. Ångström wavelength exponent (Alfa) mainly distributes in 1.1–1.6 (72%) with an obvious uni-peak pattern, implying that fine particles are primary in the aerosol group. Aerosol single scattering albedo of columnar atmosphere (SSA) at 440 nm experiences a weak seasonal variation with an average of 0.91, indicating that aerosols are mainly composed of particles with relatively higher scattering efficiency. The aerosol volume size distribution shows one fine mode and another coarse mode, with peak radii of 0.15 μm and 3.0 μm, respectively. The volume of fine mode particles is minimum in spring and maximum in summer, while the volume of coarse mode particles is minimum in autumn and maximum in winter. The scattering coefficient (Sc) of aerosols in surface atmosphere is relatively higher in winter and spring, the absorptive coefficient (Ab) is higher in autumn and summer. The SSA of surface atmosphere (SSA-surf) at 532 nm varies weakly over time with a lower deviation, mostly scattering in the range of 0.8–0.95 (82%). Although the disconnection of aerosol properties between columnar and surface atmospheres exists, AOT and Alfa are correlated to some extent with PM2.5 and visibility. However, the difference of SSA and SSA-surf is remarkable about 0.1. Overall, fine particles are dominant in aerosols and contribute to AOT significantly in this city, and their difference between surface and columnar atmospheres is unignored.
Keywords: Aerosol; Optical property; Columnar atmosphere; Surface atmosphere;

Tethered balloon-based black carbon profiles within the lower troposphere of Shanghai in the 2013 East China smog by Juan Li; Qingyan Fu; Juntao Huo; Dongfang Wang; Wen Yang; Qinggen Bian; Yusen Duan; Yihua Zhang; Jun Pan; Yanfen Lin; Kan Huang; Zhipeng Bai; Sheng-Hsiang Wang; Joshua S. Fu; Peter K.K. Louie (327-338).
A Tethered balloon-based field campaign was launched for the vertical observation of air pollutants within the lower troposphere of 1000 m for the first time over a Chinese megacity, Shanghai in December of 2013. A custom-designed instrumentation platform for tethered balloon observation and ground-based observation synchronously operated for the measurement of same meteorological parameters and typical air pollutants. One episodic event (December 13) was selected with specific focus on particulate black carbon, a short-lived climate forcer with strong warming effect. Diurnal variation of the mixing layer height showed very shallow boundary of less than 300 m in early morning and night due to nocturnal inversion while extended boundary of more than 1000 m from noon to afternoon. Wind profiles showed relatively stagnant synoptic condition in the morning, frequent shifts between upward and downward motion at noon and in the afternoon, and dominant downward motion with sea breeze in the evening. Characteristics of black carbon vertical profiles during four different periods of a day were analyzed and compared. In the morning, surface BC concentration averaged as high as 20 μg/m3 due to intense traffic emissions from the morning rush hours and unfavorable meteorological conditions. A strong gradient of BC concentrations with altitude was observed from the ground to the top of boundary layer at around 250–370 m. BC gradients turned much smaller above the boundary layer. BC profiles measured during noon and afternoon were the least dependent on heights. The largely extended boundary layer with strong vertical convection was responsible for a well mixing of BC particles in the whole measured column. BC profiles were similar between the early-evening and late-evening phases. The lower troposphere was divided into two stratified air layers with contrasted BC vertical distributions. Profiles at night showed strong gradients from the relatively high surface concentrations to low concentrations near the top of the boundary layer around 200 m. Above the boundary layer, BC increased with altitudes and reached a maximum at the top of 1000 m. Prevailing sea breeze within the boundary layer was mainly responsible for the quick cleanup of BC in the lower altitudes. In contrast, continental outflow via regional transport was the major cause of the enhanced BC aloft. This study provides a first insight of the black carbon vertical profiles over Eastern China, which will have significant implications for narrowing the gaps between the source emissions and observations as well as improving estimations of BC radiative forcing and regional climate.
Keywords: Black carbon; Vertical profile; Tethered balloon; Haze; Shanghai;

Chemical composition, sources and evolution processes of aerosol at an urban site in Yangtze River Delta, China during wintertime by Yunjiang Zhang; Lili Tang; Hongxia Yu; Zhuang Wang; Yele Sun; Wei Qin; Wentai Chen; Changhong Chen; Aijun Ding; Jing Wu; Shun Ge; Cheng Chen; Hong-cang Zhou (339-349).
To investigate the composition, sources and evolution processes of submicron aerosol during wintertime, a field experiment was conducted during December 1–31, 2013 in urban Nanjing, a megacity in Yangtze River Delta of China. Non-refractory submicron aerosol (NR-PM1) species were measured with an Aerodyne Aerosol Chemical Speciation Monitor. NR-PM1 is dominated by secondary inorganic aerosol (55%) and organic aerosol (OA, 42%) during haze periods. Six OA components were identified by positive matrix factorization of the OA mass spectra. The hydrocarbon-like OA and cooking-related OA represent the local traffic and cooking sources, respectively. A highly oxidized factor related to biomass burning OA accounted for 15% of the total OA mass during haze periods. Three types of oxygenated OA (OOA), i.e., a less-oxidized OOA (LO-OOA), a more-oxidized OOA (MO-OOA), and a low-volatility OOA (LV-OOA), were identified. LO-OOA is likely associated with fresh urban secondary OA. MO-OOA likely represents photochemical products showing a similar diurnal cycle to nitrate with a pronounced noon peak. LV-OOA appears to be a more oxidized factor with a pronounced noon peak. The OA composition is dominated by secondary species, especially during haze events. LO-OOA, MO-OOA and LV-OOA on average account for 11%, (18%), 24% (21%) and 23% (18%) of the total OA mass for the haze (clean) periods respectively. Analysis of meteorological influence suggested that regional transport from the northern and southeastern areas of the city is responsible for large secondary and low-volatility aerosol formation.
Keywords: Haze; PM1; Components; Sources; Evolution processes; YRD;

Observed aerosol optical depth and angstrom exponent in urban area of Nanjing, China by Shu Li; Tijian Wang; Min Xie; Yong Han; Bingliang Zhuang (350-356).
Aerosol optical properties at Gulou station in Nanjing, China were measured and analyzed from April 2011 to April 2012. The annual median of aerosol optical depth (hereafter called as AOD) at 440 nm was 0.73 and the corresponding annual median of angstrom exponent (hereafter called as AE) between 440 nm and 870 nm was 1.28. The monthly median of AOD440nm presented a seasonal variation, which revealed a maximum in August (1.22) and a minimum in February (0.51), while the monthly median of AE showed a minimum in May (0.79) and a maximum in December (1.42). AOD and AE accumulated mainly between 0.40–0.90 (68%) and 1.20–1.50 (68%) respectively in Nanjing. The observation data showed that high AODs (>1.00) were clustered in the fine mode growth wing and the coarse mode. Comparison was made between two typical cases under different weather conditions and the results showed that Nanjing is influenced by the dust aerosol from Northwest China and Mongolia under dust weather in spring and the anthropogenic aerosol from local emission and surrounding industrialization region under haze weather.
Keywords: Aerosol optical depth; Angstrom exponent; Urban; China;

Measurements of the vertical distribution of air pollutant concentrations can provide essential information for accurate estimates of the dispersion mechanism of local pollutants between boundary layer and troposphere. This paper reports unique measurements using an unmanned aerial vehicle (UAV) with mobile sensors to collect three-dimensional fine particulate matter (PM2.5) mass concentration data on sixteen flights within 1000 m altitude from August, 2014 to December, 2014 in Hangzhou, China.The study demonstrates the feasibility of UAV with mobile monitoring devices as an effective and flexible means to collect three-dimensional air pollutant concentration data, particularly for monitoring the vertical profile of air pollutants. The experimental results show that in general, the PM2.5 concentrations decrease as height increases, with an exception when the air temperature inversion layer appears, and the decrease rate of PM2.5 concentrations is larger in the morning than in the afternoon flights. This is a result of the accumulated pollutant emission of human activities during the day and the varied meteorological conditions. At the same horizontal layer, there are fluctuations in PM2.5 concentrations during different time periods of the day. The vertical fluctuations of PM2.5 concentrations become nearly uniform in two afternoon flights, which is directly related with the extent of atmospheric mixture. Seen from the multiple regression models, the distribution of relative PM2.5 concentrations between vertical and ground observations is well characterized and the regression coefficients of four measured factors (i.e., air temperature, relative humidity, air pressure and height) effectively explain their impacts on the vertical distribution patterns. Air temperature and relative humidity are the most influential factors that affect the vertical distribution of PM2.5 concentrations.
Keywords: Fine particulate matter; Vertical distribution; Meteorological parameters; Unmanned aerial vehicle;

In order to investigate the regional variations of water-soluble ions (WSIs), size-resolved measurement of aerosol particles and WSIs was conducted by using Anderson Sampler and Ion Chromatography at five sites (Nanjing, Suzhou, Lin'an, Hangzhou and Ningbo) in the Yangtze River Delta (YRD) region, China in the Autumn of 2012 and Winter, Spring and Summer of 2013. WSIs exhibited obvious seasonal variations due to the monsoon conversion, with the highest level in winter and lowest level in summer. The aerosol mass concentrations and WSIs in different size segments varied with four seasons. The dominant ions concentrations in PM2.1 ranked in the order of SO 4 2 −  >  NO 3 −  >  NH 4 +  > Cl > K+ > Ca2+, and the dominant ions concentrations in PM2.1–10 ranked in the order of Ca2+ >  NO 3 −  >  SO 4 2 −  > Cl >  NH 4 +  > Na+. The size spectra of mass and WSIs concentration peaked mostly at 0.43–0.65 μm in four seasons. The concentration discrepancies of WSIs in different cities were caused by the geographic locations and emission source. It's belonged to ammonium-rich distribution in PM2.1 and ammonium-poor distribution in PM2.1–10 in the YRD region. The impact of temperature on mass concentrations of NO 3 − and NH 4 + in PM2.1 were stronger than those in PM2.1−10. PCA analysis shows that the sources of WSIs dominant by anthropogenic sources, soil particles or falling dust, sea salt and burning process.
Keywords: The Yangtze River Delta; Water-soluble ions; Seasonal distribution; Size distribution; Sources;

Characteristics and source apportionment of PM2.5 during a fall heavy haze episode in the Yangtze River Delta of China by Yang Hua; Zhen Cheng; Shuxiao Wang; Jingkun Jiang; Daren Chen; Siyi Cai; Xiao Fu; Qingyan Fu; Changhong Chen; Bingye Xu; Jianqiao Yu (380-391).
Joint field observations were conducted from October to November in 2011 to observe haze pollution in the Yangtze River Delta (YRD), China. Samples of particulate matter with diameter less than 2.5 μm (PM2.5) and less than 10 μm (PM10), gaseous pollutants and meteorology data were collected in five cities – Shanghai, Suzhou, Nanjing, Ningbo and Hangzhou – in the YRD. The chemical composition of PM2.5 was analyzed and the light extinction resulting from each chemical species was calculated using the IMPROVE algorithm. A typical heavy haze episode was selected and the chemical mass balance (CMB) model was applied to identify the sources of PM2.5. The average PM2.5 and PM10 mass concentrations during the haze episode were 100 ± 24 μg/m3 and 164 ± 19 μg/m3, respectively; visibility decreased to 1 km. Organic matter (OM), sulfate, nitrate, and ammonium were the dominant components of PM2.5, accounting for 33%, 19%, 17% and 11% of PM2.5 mass, respectively. Sulfate, OM and nitrate had the highest impact on light extinction, contributing 30%, 28% and 19%, respectively. The source apportionment indicate that PM2.5 is primarily from secondary pollutants and primary emissions from vehicles and biomass burning. A polluted air mass from north Jiangsu Province and stagnant meteorology further aggravated the haze pollution. The five cities had similar characteristics and pollution sources.
Keywords: Haze; PM2.5; Source apportionment; Yangtze River Delta;

Climatic analysis of satellite aerosol data on variations of submicron aerosols over East China by Chenghao Tan; Tianliang Zhao; Xiaofeng Xu; Jane Liu; Lei Zhang; Lili Tang (392-398).
Recently, haze events frequently occurred in East China. To assess the impacts of aerosols on air quality over the region, we investigate the interannual variations of the total aerosols and the submicron aerosols, in terms of the aerosol mass concentration (AMC) and Fine Mode Fraction (FMF), respectively, using the Moderate Resolution Imaging Spectrometer (MODIS) aerosol products, which can be used for regional air quality assessment, from 2003 to 2013. On average, the AMC distributes as “northern high and southern low”, whereas the FMF shows a “northern low and southern high” pattern. High FMF occurs in the warm seasons, but low FMF appears in the cool seasons. During the 10 years, the AMC shows increasing trend in northern and decreasing trend in southeastern parts of the region, whereas an increasing trend in the FMF is observed over the entire East China, likely related to elevated submicron aerosols from anthropogenic sources. The East Asian summer monsoon impacts the submicron aerosols more than the total aerosols. The enhanced submicron aerosols are responsible for rapid deterioration of air quality in East China in recent years.
Keywords: Aerosols; Interannual variation; Submicron particles; MODIS; The East Asian monsoon;

Emission characteristics of carbonaceous particles and trace gases from open burning of crop residues in China by Haiyan Ni; Yongming Han; Junji Cao; L.-W. Antony Chen; Jie Tian; Xiaoliang Wang; Judith C. Chow; John G. Watson; Qiyuan Wang; Ping Wang; Hua Li; Ru-Jin Huang (399-406).
Open burning of crop residue is an important source of carbonaceous pollutants, and has a large impact on the regional environment and global climate change. Laboratory burn tests were conducted using a custom-made combustion chamber to determine pollutants (i.e. CO2, CO, PM2.5, organic carbon (OC) and elemental carbon (EC)) emission factors (EFs) of wheat straw, rice straw and corn stalk; the three major agricultural crop residues in China. The average EFs were estimated to be 1351 ± 147 g kg−1 for CO2, 52.0 ± 18.9 g kg−1 for CO, 10.6 ± 5.6 g kg−1 for PM2.5, 4.8 ± 3.1 g kg−1 for OC and 0.24 ± 0.12 g kg−1 for EC. In addition, the effect of fuel moisture was investigated through the controlled burning of wheat straw. Increasing the moisture content decreased the CO2 EF, and increased the EFs of CO, PM2.5 and OC. Based on measurements from this study and nationwide statistics in crop type and area, pollutants emission inventories for crop residue combustion with 1° × 1° resolution were compiled for 2008. Total emissions were 120 Tg CO2, 4.6 Tg CO, 0.88 Tg PM2.5, 0.39 Tg OC and 0.02 Tg EC.
Keywords: Crop residue; Open burning; Emission factor; Combustion chamber;

Thermal desorption single particle mass spectrometry of ambient aerosol in Shanghai by Jinghao Zhai; Xinning Wang; Jingyan Li; Tingting Xu; Hong Chen; Xin Yang; Jianmin Chen (407-414).
Submicron aerosol volatility, chemical composition, and mixing state were simultaneously measured using a thermodenuder (TD) in-line with a single particle aerosol mass spectrometry (SPAMS) during Nov.12 to Dec. 11 of 2014 in Shanghai. By heating up to 250 °C, the signals of refractory species such as elemental carbon, metallic compounds, and mineral dust in aerosols were enhanced in the mass spectra. At 250 °C, the main particle types present in the size range of 0.2–1.0 μm were biomass burning (37% by number) and elemental carbon (20%). From 1.0 to 2.0 μm, biomass burning (30%), dust (19%) and metal-rich (18%) were the primary particle types. CN signal remained in the mass spectra of the heated biomass burning particles suggests the existence of some extremely low-volatility nitrogen-containing organics. Laboratory experiments were conducted by burning rice straws, the main source material of biomass burning particles in Southern China, to confirm the less volatile composition contributed by biomass burning. Strong CN with relative area >0.21 was observed in most of the laboratory-made biomass burning particles when heated above 200 °C and was selected as a new marker to identify the biomass burning particles in the field. The TD-SPAMS measured the size-resolved chemical composition of the individual particle residues at different temperatures and offered more information on the aging processes of primary particles and their sources.
Keywords: Aerosol volatility; Mixing state; Thermal desorption; SPAMS;

Source apportionment of fine particles and its chemical components over the Yangtze River Delta, China during a heavy haze pollution episode by L. Li; J.Y. An; M. Zhou; R.S. Yan; C. Huang; Q. Lu; L. Lin; Y.J. Wang; S.K. Tao; L.P. Qiao; S.H. Zhu; C.H. Chen (415-429).
An extremely high PM2.5 pollution episode occurred over the eastern China in January 2013. In this paper, the particulate matter source apportionment technology (PSAT) method coupled within the Comprehensive air quality model with extensions (CAMx) is applied to study the source contributions to PM2.5 and its major components at six receptors (Urban Shanghai, Chongming, Dianshan Lake, Urban Suzhou, Hangzhou and Zhoushan) in the Yangtze River Delta (YRD) region. Contributions from 4 source areas (including Shanghai, South Jiangsu, North Zhejiang and Super-region) and 9 emission sectors (including power plants, industrial boilers and kilns, industrial processing, mobile source, residential, volatile emissions, dust, agriculture and biogenic emissions) to PM2.5 and its major components (sulfate, nitrate, ammonia, organic carbon and elemental carbon) at the six receptors in the YRD region are quantified. Results show that accumulation of local pollution was the largest contributor during this air pollution episode in urban Shanghai (55%) and Suzhou (46%), followed by long-range transport (37% contribution to Shanghai and 44% to Suzhou). Super-regional emissions play an important role in PM2.5 formation at Hangzhou (48%) and Zhoushan site (68%). Among the emission sectors contributing to the high pollution episode, the major source categories include industrial processing (with contributions ranging between 12.7 and 38.7% at different receptors), combustion source (21.7–37.3%), mobile source (7.5–17.7%) and fugitive dust (8.4–27.3%). Agricultural contribution is also very significant at Zhoushan site (24.5%). In terms of the PM2.5 major components, it is found that industrial boilers and kilns are the major source contributor to sulfate and nitrate. Volatile emission source and agriculture are the major contributors to ammonia; transport is the largest contributor to elemental carbon. Industrial processing, volatile emissions and mobile source are the most significant contributors to organic carbon. Results show that the Yangtze River Delta region should focus on the joint pollution control of industrial processing, combustion emissions, mobile source emissions, and fugitive dust. Regional transport of air pollution among the cities are prominent, and the implementation of regional joint prevention and control of air pollution will help to alleviate fine particulate matter concentrations under heavy pollution case significantly.
Keywords: Fine particulate matter; Particulate matter source apportionment technology; Yangtze River Delta; CAMx;

Seasonal variation and four-year trend of black carbon in the Mid-west China: The analysis of the ambient measurement and WRF-Chem modeling by Shuyu Zhao; Xuexi Tie; Junji Cao; Nan Li; Guohui Li; Qiang Zhang; Chongshu Zhu; Xin Long; Jiandong Li; Tian Feng; Xiaoli Su (430-439).
In-situ measurement of black carbon (BC) concentration from September 2003 to August 2007 in the Xi'an City at the Guanzhong Basin located in the mid-western China (the Guanzhong Basin) was analyzed. A regional dynamics and aerosol model (WRF-Chem) was used to quantify the impacts of local emission, meteorological conditions, and regional atmospheric transport on seasonal variation of BC concentration at the Guanzhong Basin. The results show that the regional prevailing winds at the Guanzhong Basin were unfavorable for the horizontal transport. The mean wind speeds ranged from 1.0 m/s to 1.9 m/s. During winter, the wind at the Guanzhong Basin was very weak (∼1.0 m/s). During spring and autumn, there was a wind convergent zone at the Guanzhong Basin, constraining the BC concentrations inside the Guanzhong Basin. As a result, the BC concentrations were persistently high at the Guanzhong Basin. In addition to the high background concentrations, there was a strong seasonal variation, with a maximum in winter (winter maximum) and a minimum in summer (summer minimum), with the maximum of the mean concentration of 30 μg m−3 in 2003–2004 winter, and the minimum of 5 μg m−3 in 2004 summer. The model sensitivity study shows that the seasonal variation of BC concentration was largely due to the seasonal variation of BC emission, especially during winter with the maximum of BC emission. A strong annual decrease trend of the BC concentration was found from 2004 to 2007. It is interesting to note that the decrease of the BC concentration only occurred in winter. For example, the winter maximum was 20 μg m−3 in 2003, and reduced to 11 μg m−3 in 2006, with about 50% decrease. In contrast, the summer minimum was 10 μg m−3 in 2004 and 9 μg m−3 in 2007, with only 10% decrease. This study suggests that the rapid decrease in the winter maximum was mainly due to the reduction of the BC emission in winter, implying the effective winter emission control at the Guanzhong Basin.
Keywords: Black carbon; Seasonal variation; WRF-Chem model; Emission; Xi'an city; Guanzhong basin;

Assessment of short-term PM2.5-related mortality due to different emission sources in the Yangtze River Delta, China by Jiandong Wang; Shuxiao Wang; A. Scott Voorhees; Bin Zhao; Carey Jang; Jingkun Jiang; Joshua S. Fu; Dian Ding; Yun Zhu; Jiming Hao (440-448).
Air pollution is a major environmental risk to health. In this study, short-term premature mortality due to particulate matter equal to or less than 2.5 μm in aerodynamic diameter (PM2.5) in the Yangtze River Delta (YRD) is estimated by using a PC-based human health benefits software. The economic loss is assessed by using the willingness to pay (WTP) method. The contributions of each region, sector and gaseous precursor are also determined by employing brute-force method. The results show that, in the YRD in 2010, the short-term premature deaths caused by PM2.5 are estimated to be 13,162 (95% confidence interval (CI): 10,761-15,554), while the economic loss is 22.1 (95% CI: 18.1–26.1) billion Chinese Yuan. The industrial and residential sectors contributed the most, accounting for more than 50% of the total economic loss. Emissions of primary PM2.5 and NH3 are major contributors to the health-related loss in winter, while the contribution of gaseous precursors such as SO2 and NOx is higher than primary PM2.5 in summer.Display Omitted
Keywords: PM2.5; Mortality; Economic loss; Source apportionment; Yangtze River Delta;

Indoor air quality at five site museums of Yangtze River civilization by Tafeng Hu; Wenting Jia; Junji Cao; Rujin Huang; Hua Li; Suixin Liu; Tao Ma; Yuqing Zhu (449-454).
The Yangtze River civilization, dating back to more than 7 thousand years ago, is one of the most historic culture aggregates in China. For long-term conservation of archaeological artifacts and historical ruins along the Yangtze River, indoor air quality at five site museums were investigated during summer and winter. Unstable microclimate conditions were observed at all five museums. The maximal seasonal variations in temperature and relative humidity were 25.7 °C and 40.0%, respectively. The mass concentration of PM2.5 inside the museums remained at high levels, ranging from 33.9 to 79.6 μg/m3 in winter and from 52.8 to 113.0 μg/m3 in summer. Organic matter (OM) constituted a major fraction (39.3%–53.9% in summer, 22.1%–27.8% in winter) of total PM2.5. The results showed that besides short-term fluctuation and seasonal variation in microclimate conditions, infiltration of gaseous and particulate air pollutants should be of increasing concern at museums in Southern China.
Keywords: Site museum; Indoor air quality; Microclimate; Air pollution; Particulate matter;