Yuesi Wang

Persistent sulfate formation from London Fog to Chinese haze

Significance Exceedingly high levels of fine particulate matter (PM) occur frequently in China, but the mechanism of severe haze formation remains unclear. From atmospheric measurements in two Chinese megacities and laboratory experiments, we show that the oxidation of SO2 by NO2 occurs efficiently in aqueous media under two polluted conditions: first, during the formation of the 1952 London Fog via in-cloud oxidation; and second, on fine PM with NH3 neutralization during severe haze in China. We suggest that effective haze mitigation is achievable by intervening in the sulfate formation process with NH3 and NO2 emission control measures. Hence, our results explain the outstanding sulfur problem during the historic London Fog formation and elucidate the chemical mechanism of severe haze in China. Sulfate aerosols exert profound impacts on human and ecosystem health, weather, and climate, but their formation mechanism remains uncertain. Atmospheric models consistently underpredict sulfate levels under diverse environmental conditions. From atmospheric measurements in two Chinese megacities and complementary laboratory experiments, we show that the aqueous oxidation of SO2 by NO2 is key to efficient sulfate formation but is only feasible under two atmospheric conditions: on fine aerosols with high relative humidity and NH3 neutralization or under cloud conditions. Under polluted environments, this SO2 oxidation process leads to large sulfate production rates and promotes formation of nitrate and organic matter on aqueous particles, exacerbating severe haze development. Effective haze mitigation is achievable by intervening in the sulfate formation process with enforced NH3 and NO2 control measures. In addition to explaining the polluted episodes currently occurring in China and during the 1952 London Fog, this sulfate production mechanism is widespread, and our results suggest a way to tackle this growing problem in China and much of the developing world.

Impacts of soil moisture on nitrous oxide emission from croplands: a case study on the rice-based agro-ecosystem in Southeast China

Abstract Based on the in situ measurement of soil moisture and nitrous oxide (N2O) emission from a rice–wheat rotation ecosystem of southeast China and on the simulated experiments in laboratory, the impact of soil moisture on N2O emission is investigated. By analyzing the experimental data in detail, some results could be outlined as follows: (a) It is soil moisture and temperature instead of N fertilization that determines the seasonal variation pattern of N2O emission from the rice-based crop rotation ecosystem of southeast China. (b) Soil moisture is the most sensitive factor to regulate N2O emission from croplands. (c) Explosive emission of N2O from the rice-based agro-ecosystem was found to happen at the soil moisture within (110±5)% soil water holding capacity or field capacity (SWHC) or (99±9)% water-filled pore space (WFPS). When soil moisture of the rice–wheat fields is less than 105% SWHC, the N2O emission was observed to increase exponentially vs. soil moisture. In contrast, N2O emission was found to decrease reciprocally vs. soil moisture more than 115% SWHC. (d) The response of the N2O emission rate from soils in fields to variations of soil moisture may be well described with a general empirical equation. For x⩽C0% SWHC, F=A e −B(x−C 0 ) 2 +D e Ex . For x⩾C0% SWHC, F=A e −B(x−C 0 ) 2 + e G x −H . The equation to describe the relationship between soil moisture and N2O emission rates from incubated soil is different from that for fitting data observed in fields. Reasons for the difference still remains uncertain.

Mineral dust and NOx promote the conversion of SO2 to sulfate in heavy pollution days

Haze in China has been increasing in frequency of occurrence as well as the area of the affected region. Here, we report on a new mechanism of haze formation, in which coexistence with NOx can reduce the environmental capacity for SO2, leading to rapid conversion of SO2 to sulfate because NO2 and SO2 have a synergistic effect when they react on the surface of mineral dust. Monitoring data from five severe haze episodes in January of 2013 in the Beijing-Tianjin-Hebei regions agreed very well with the laboratory simulation. The combined air pollution of motor vehicle exhaust and coal-fired flue gases greatly reduced the atmospheric environmental capacity for SO2, and the formation of sulfate was found to be a main reason for the growth of fine particles, which led to the occurrence of haze. These results indicate that the impact of motor vehicle exhaust on the atmospheric environment might be underestimated.

Aerosol optical depth (AOD) and Angstrom exponent of aerosols observed by the Chinese Sun Hazemeter Network from August 2004 to September 2005

500, and 650 nm were analyzed for the period of August 2004 to September 2005. The smallest mean AOD (0.15) was found in the Tibetan Plateau where a showed the largest range in value (0.06‐0.9). The remote northeast corner of China was the next cleanest region with AODs ranging from 0.19 to 0.21 and with the largest a (1.16‐1.79), indicating the presence of fine aerosol particles. The forested sites exhibited moderate values of AOD (0.19‐0.51) and a (0.97‐1.47). A surprising finding was that the AOD measured at a few desert sites in northern China were relatively low, ranging from 0.24 to 0.36, and that a ranged from 0.42 to 0.99, presumably because of several dustblowing episodes during the observation period. The AOD observed over agricultural areas ranges from 0.38 to 0.90; a ranges from 0.55 to 1.11. These values do not differ much from those observed at the inland urban and suburban sites where AOD ranges from 0.50 to 0.69 and a ranges from 0.90 to 1.48. Given the geographic heterogeneity and the rapid increase in urbanization in China, much longer and more extensive observations are required.

Size-resolved aerosol chemical analysis of extreme haze pollution events during early 2013 in urban Beijing, China

Using size-resolved filter sampling and chemical characterization, high concentrations of water-soluble ions, carbonaceous species and heavy metals were found in both fine (PM2.1) and coarse (PM2.1-9) particles in Beijing during haze events in early 2013. Even on clear days, average mass concentration of submicron particles (PM1.1) was several times higher than that previously measured in most of abroad urban areas. A high concentration of particulate matter on haze days weakens the incident solar radiation, which reduces the generation rate of secondary organic carbon in PM1.1. We show that the peak mass concentration of particles shifted from 0.43-0.65μm on clear days to 0.65-1.1μm on lightly polluted days and to 1.1-2.1μm on heavily polluted days. The peak shifts were also found for the following species: organic carbon, elemental carbon, NH4(+), SO4(2-), NO3(-), K, Cu, Zn, Cd and Pb. Our findings demonstrate that secondary inorganic aerosols (36%) and organic matter (26%) dominated the fine particle mass on heavily polluted days, while their contribution reduced to 29% and 18%, respectively, on clear days. Besides fine particles, anthropogenic chemical species also substantially accumulated in the coarse mode, which suggests that particles with aerodynamic diameter larger than 2.1μm cannot be neglected during severe haze events.

Health impacts and economic losses assessment of the 2013 severe haze event in Beijing area.

Haze is a serious air pollution problem in China, especially in Beijing and surrounding areas, affecting visibility, public health and regional climate. In this study, the Weather Research and Forecasting-Chemistry (WRF-Chem) model was used to simulate PM2.5 (particulate matters with aerodynamic diameter≤2.5 μm) concentrations during the 2013 severe haze event in Beijing, and health impacts and health-related economic losses were calculated based on model results. Compared with surface monitoring data, the model results reflected pollution concentrations accurately (correlation coefficients between simulated and measured PM2.5 were 0.7, 0.4, 0.5 and 0.6 in Beijing, Tianjin, Xianghe and Xinglong stations, respectively). Health impacts assessments show that the PM2.5 concentrations in January might cause 690 (95% confidence interval (CI): (490, 890)) premature deaths, 45,350 (95% CI: (21,640, 57,860)) acute bronchitis and 23,720 (95% CI: (17,090, 29,710)) asthma cases in Beijing area. Results of the economic losses assessments suggest that the haze in January 2013 might lead to 253.8 (95% CI: (170.2, 331.2)) million US

CHANGES OF ATMOSPHERIC COMPOSITION AND OPTICAL PROPERTIES OVER BEIJING—2008 Olympic Monitoring Campaign

losses, accounting for 0.08% (95% CI: (0.05%, 0.1%)) of the total 2013 annual gross domestic product (GDP) of Beijing.

Analysis of genetic heterogeneity among five gynogenetic clones of silver crucian carp, Carassius auratus gibelio Bloch, based on detection of RAPD molecular markers

Before and during the 2008 Beijing Olympics from June to September, ground-based and satellite monitoring were carried out over Beijing and its vicinity (BIV) in a campaign to quantify the outcomes of various emission control measures. These include hourly surface PM10 and PM2.5 and their fraction of black carbon (BC), organics, nitrate, sulfate, ammonium, and daily aerosol optical depth (AOD), together with hourly reactive gases, surface ozone, and daily columnar NO2 from satellite. The analyses, excluding the estimates from weather contributions, demonstrate that after the control measures, including banning ~300,000 “yellow-tag” vehicles from roads, the even–odd turn of motor vehicles on the roads, and emission reduction aiming at coal combustion, were implemented, air quality in Beijing improved substantially. The levels of NO, NO2, NOx, CO, SO2, BC, organics, and nitrate dropped by about 30%–60% and the ozone moderately increased by ~40% while the sulfate and ammonium exhibited different patterns dur...

The Campaign on Atmospheric Aerosol Research Network of China: CARE-China

The gynogenetic silver crucian carp, Carassius auratus gibelio, is a unique model system for studying evolutionary genetics and selective breeding, owing to its specific genetic background and reproductive modes. Five gynogenetic clones were analyzed by the random amplified polymorphic DNA (RAPD) technique, using 30 10-nucleotide-long primers. Twenty-six primers produced well-amplified DNA fragments with reproducible banding patterns, and 24 primers were polymorphic. Nearly identical banding patterns were observed among individuals within each clone, suggesting that each clone might possess a specific pattern owing to its gynogenesis. In contrast, the RAPD patterns of the five clones differed from each other. A phylogenetic tree was constructed using UPGMA cluster analysis based on a total of 3,744 distinguishable fragments (156 per individual). Average genetic distances within and among the five clones clearly indicated their intraclonal homogeneity, interclonal heterogeneity, and phylogenetic relationships. Clones A and P were the most closely related, whereas the most divergence was seen between clone D and clone E or F. A total of 88 polymorphic fragments were scored from 24 primers after excluding bands that were monomorphic for the five clones. Most primers corresponding to the polymorphic fragments amplified reproducible markers specific for one clone or that were shared by two, three, or four clones. Several primers (e.g., Opj-1, Opj-7, and Opp-10) produced abundant banding patterns that could be used to discriminate between the five clones. Markers specific for one or two clones were also identified. The RAPD markers identified in this study will likely benefit evolutionary genetics and selective breeding studies.

Haze insights and mitigation in China: An overview

AbstractBased on a network of field stations belonging to the Chinese Academy of Sciences (CAS), the Campaign on Atmospheric Aerosol Research network of China (CARE-China) was recently established as the country’s first monitoring network for the study of the spatiotemporal distribution of aerosol physical characteristics, chemical components, and optical properties, as well as aerosol gaseous precursors. The network comprises 36 stations in total and adopts a unified approach in terms of the instrumentation, experimental standards, and data specifications. This ongoing project is intended to provide an integrated research platform to monitor online PM2.5 concentrations, nine-size aerosol concentrations and chemical component distributions, nine-size secondary organic aerosol (SOA) component distributions, gaseous precursor concentrations (including SO2, NOx, CO, O3, and VOCs), and aerosol optical properties. The data will be used to identify the sources of regional aerosols, the relative contributions fr...