Guangming Shi

Highly time-resolved characterization of water-soluble inorganic ions in PM2.5 in a humid and acidic mega city in Sichuan Basin, China.

To investigate the characteristics of water-soluble inorganic ions (WSIIs) in Chongqing, a well-known foggy and acid region in southwestern China, hourly real-time concentrations of five cations (Na+, K+, NH4+, Ca2+, and Mg2+) and six anions (F-, Cl-, NO2-, NO3-, PO43-, and SO42-) in PM2.5 during winter (from Dec. 18, 2015 to Mar. 20, 2016) in Chongqing were collected by applying In-situ Gas and Aerosol Compositions Monitor. The hourly total concentration of WSIIs was 38.5μg/m3 on average, accounting for 57% of PM2.5 mass concentration. Secondary inorganic aerosols (NH4+, NO3-, and SO42-) were dominant WSIIs, accounting for 91% of WSIIs mass. Compared to ten years ago, SO42- concentrations were decreased by 31% but NO3- levels were doubled, likely indicative of sharply enhanced contribution to fine particle pollution from mobile sources over stationary sources. NO3- originated from the current fluxes of NH3 and HNO3 onto sulfate particles and/or from in-cloud processes were critical pathways under humid conditions in the study area. Water content and/or RH might be important factors controlling nitrate formation. Trajectory analysis manifested that aerosol pollutions in Chongqing were mostly caused by local emissions.

Aerosol optical properties and chemical composition apportionment in Sichuan Basin, China

PM2.5 and its major chemical components, and light scattering (σscat) and absorption (σabs) coefficients were measured in Chengdu (CD) and Chongqing (CQ) in Sichuan Basin, from October 2014 to July 2015. Annual mean PM2.5, σscat and σabs were 67.0±43.4μgm-3, 421.4±290.1Mm-1 and 36.7±26.4Mm-1, respectively, in CD, and annual mean PM2.5 and σabs were 70.9±41.4μgm-3 and 45.4±24.5Mm-1, respectively, in CQ. PM2.5, σscat and σabs were all evidently higher in winter than in other seasons mainly due to the unfavorable meteorological conditions for dispersion of local pollutants. Diurnal patterns of σscat and σabs exhibited a peak value around 7:00-8:00 LT and a valley value around 17:00-18:00 LT. High levels of PM2.5 accompanied with low wind speed and high relative humidity conditions were the major causes of visibility impairment in Sichuan Basin. Both σscat and σabs were remarkably higher under calm wind condition, indicating that local emissions were largely responsible for the aerosol pollutions in this region. High relative humidity enhanced extinction coefficient (bext) by up to around 1.6 and 1.4 times in CD and CQ, respectively, due to the hygroscopic growth of water soluble components. On annual basis, (NH4)2SO4 contributed the most to bext, accounting for 34.4% and 31.5% in CD and CQ, respectively, followed by NH4NO3 and organic matter, 28.1% and 17.5%, respectively, in CD, and 20.1% and 26.8%, respectively, in CQ. EC contributed about 10% and the rest contributed to <12% at both urban sites. Therefore, reducing emissions of the precursor gases such as SO2, NOx, NH3 and VOCs systemically may be efficient to improve the air quality and visibility simultaneously in Sichuan Basin.

Mass Transport of Background Asian Dust Revealed by Balloon-Borne Measurement: Dust Particles Transported during Calm Periods by Westerly from Taklamakan Desert

The dust storm which is caused by low pressure activities in China and Mongolia has been investigated by many investigators, but very thin dust clouds, which can be frequently detected in every season (we call it background Asian dust here) by lidar in Japan, Korea, and China but not by satellite, have attracted very few investigators since detection of the cloud is not easy. It, however, has been suggested that the background Asian dust also plays an important role in the biogeochemical cycle of dust in east Asia and west Pacific regions through long range transport of dust particles by westerly winds, and information of outflow rate of background dust particles over the dust source areas is strongly desired since previous investigations were made mostly in the down wind regions (Iwasaka et al. 1988; Matsuki et al. 2002; Trochkine et al. 2002). According to the balloon-borne measurements made under the calm weather condition in 2001–2004 at Dunhuang (40°00′N, 94°30′E), China, mass flux of background Asian dust due to westerly wind was about 50 ton/km/day over the Taklamakan desert (about 4 to 6 km altitudes) and 1 Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Japan 2 Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan 3 Institute of Atmospheric Physics, Chinese Academy of Science, Beijing, China 4 Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto, Japan 5 Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Science, Lanzhou, China a Now: Institute of Environmental and Industrial Medicine, Hanyang University, Seoul, Korea b Now: Laboratorire de Meteorologie Physique, Universite Blaise Pascal, Aubie re CEDEX, France c Now: Institute for Water and Environmental Problems, Siberian Branch of Russian Academy of Science, Barnaul, Russia 121 Y.J. Kim and U. Platt (eds.), Advanced Environmental Monitoring, 121–135.

Wet-only deposition of atmospheric inorganic nitrogen and associated isotopic characteristics in a typical mountain area, southwestern China

To quantify and compare atmospheric nitrogen (N) deposition and its N isotopic ratio are critical for constraining N sources and effective reduction of reactive N emissions. In this study, a total of 223 rainwater samples were collected by wet-only auto-samplers, and wet-only deposition and isotopic composition (δ15N) of reduced (NH4+-N) and oxidized (NO3--N) N were measured at three typical mountain sites, including an urban (Wanzhou, WZ), a town (Gaoyang, GY) and a rural (Dade, DD) site in Chongqing, southwestern China in 2016. The wet-only inorganic N deposition (DIN, sum of NO3--N and NH4+-N) were 17.50, 8.63 and 12.16kgNha-1yr-1 at WZ, GY and DD site, respectively. Annual δ15N-NH4+ values of rainwaters were negative at the urban site (-3.12±3.21‰, WZ) and positive at both town and rural site (0.65±12.51‰, GY; 2.16±6.11‰, DD). Annual δ15N-NO3- values, on the contrary, were positive at the urban site (0.33±7.87‰, WZ) and negative at both town and rural site (-5.59±2.20‰, GY; -0.39±8.89‰, DD). These results reveal the urban site was wet-only DIN hotspot and had a different N source compared with the town-rural site in the mountain area. Moreover, precipitation DIN had a potentially negative risk on both aquatic and forest ecosystems.

Source characterization of urban particles from meat smoking activities in Chongqing, China using single particle aerosol mass spectrometry

A Single Particle Aerosol Mass Spectrometer (SPAMS) was deployed in the urban area of Chongqing to characterize the particles present during a severe particulate pollution event that occurred in winter 2014-2015. The measurements were made at a time when residents engaged in traditional outdoor meat smoking activities to preserve meat before the Chinese Spring Festival. The measurement period was predominantly characterized by stagnant weather conditions, highly elevated levels of PM2.5, and low visibility. Eleven major single particle types were identified, with over 92.5% of the particles attributed to biomass burning emissions. Most of the particle types showed appreciable signs of aging in the stagnant air conditions. To simulate the meat smoking activities, a series of controlled smoldering experiments was conducted using freshly cut pine and cypress branches, both with and without wood logs. SPAMS data obtained from these experiments revealed a number of biomass burning particle types, including an elemental and organic carbon (ECOC) type that proved to be the most suitable marker for meat smoking activities. The traditional activity of making preserved meat in southwestern China is shown here to be a major source of particulate pollution. Improved measures to reduce emissions from the smoking of meat should be introduced to improve air quality in regions where smoking meat activity prevails.

Characterization of water soluble inorganic ions and their evolution processes during PM2.5 pollution episodes in a small city in southwest China

PM2.5 samples were collected in four segregate one-month periods, each representing one season, for analyzing their contents of water soluble inorganic ions (WSIIs) in a small city inside Sichuan Basin. Daily PM2.5 concentrations ranged from 23.2 to 203.1 μg m-3 with an annual mean of 66.9 ± 33.6 μg m-3. Annual mean concentrations of WSIIs was 28.8 ± 20.3 μg m-3, accounting for 43.1% of PM2.5. Seasonal mean concentrations of WSIIs ranged from 17.5 ± 9.3 μg m-3 in summer to 46.5 ± 27.6 μg m-3 in winter. Annual mean mass ratio of NO3-/SO42- was 0.49, demonstrating predominant stationary sources for secondary inorganic aerosols (SNA, including SO42-, NH4+ and NO3-); whereas annual mean molar ratio of [NH4+]/[NO3-] was 3.5, suggesting dominant agriculture emissions contributing to the total nitrogen. During a severe and long-lasting (13 days) winter pollution period when mean PM2.5 concentration reached to 132.5 μg m-3, PM2.5 concentration was enhanced by a factor of 2.6 while that of SNA by a factor of 2.9 compared to those before the pollution event, and the fraction of SNA in PM2.5 only increased slightly (from 46.7% to 50.6%). Thus, local accumulation of pollutants under poor diffusion conditions played a major role causing the extremely high PM2.5 concentration, besides the contributions from the enhanced SNA formation under specific weather conditions.

Ice Cloud Formation Mechanisms Inferred from in situ Measurements of Particle Number-size Distribution

4 Institute of Atmospheric Physics, Chinese Academy of Science, Beijing 100029, China Abstract Ice crystals in cirrus clouds are formed via homogeneous or heterogeneous pathway. This work addresses in situ measurements of ice crystal concentrations in the region that is thought to be in a favorable condition for ice nucleation. Based on a series of measurements by a balloon-borne optical particle counter, possible scenarios of ice cloud formations will be discussed.