This paper applies CALPUFF model to simulate the spatial distribution of sulfur dioxide in Urumqi and analyzes the source contribution to areas where the SO2 concentration is high. The result shows that annual mean concentration is highest in the middle of Saybagh and with the value of 44 μg/m3. The maximum 24-h averaged SO2 concentration is highest in the junction area of the middle-west of Saybagh and the north of Urumqi county, and the highest value is 467 μg/m3. The spatial distribution of SO2 in January is similar to that in October, and April is similar to that in July. National monitoring stations are dense in the middle of city where the concentration is low and can't reflect the spatial distribution effectively. Baosteel group contributes most to the Saybagh high concentration area (37 μg/m3/a); China National Petroleum Corporation Urumqi petrochemical company contributes most to the Midong high concentration area (5.3 μg/m3/a); Houxia power plant contributes most to the Houxia high concentration area (33 μg/m3/a).

With the objective of reducing the large uncertainties in the estimations of emissions from crop residue open burning, an improved method for establishing emission inventories of crop residue open burning at a high spatial resolution of 0.25° × 0.25° and a temporal resolutionof 1 month was established based on the moderate resolution imaging spectroradiometer(MODIS) Thermal Anomalies/Fire Daily Level3 Global Product (MOD/MYD14A1). Agriculture mechanization ratios and regional crop-specific grain-to-straw ratios were introduced to improve the accuracy of related activity data. Locally observed emission factors were used to calculate the primary pollutant emissions. MODIS satellite data were modified by combining them with county-level agricultural statistical data, which reduced the influence of missing fire counts caused by their small size and cloud cover. The annual emissions of CO2, CO, CH4, nonmethane volatile organic compounds (NMVOCs), N2O, NOx, NH3, SO2, fine particles (PM2.5), organic carbon (OC), and black carbon (BC) were 150.40, 6.70, 0.51, 0.88, 0.01, 0.13, 0.07, 0.43, 1.09, 0.34, and 0.06 Tg, respectively, in 2012. Crop residue open burning emissions displayed typical seasonal and spatial variation. The highest emission regions were the Yellow-Huai River and Yangtse-Huai River areas, and the monthly emissions were highest in June (37%). Uncertainties in the emission estimates, measured as 95% confidence intervals, range from a low of within ± 126% for N2O to a high of within ± 169% for NH3.

108 ambient volatile organic compounds (VOCs) were measured continuously at a time resolution of an hour using an online gas chromatography–frame ionization detector/mass spectrometry (GC–FID/MS) in October 2014 in Beijing, and positive matrix factorization (PMF) was performed with online data. The evolution process and causes for high levels of VOCs during a haze event were investigated through comprehensive analysis. Results show that mixing ratios of VOCs during the haze event (89.29 ppbv) were 2 to 5 times as that in non-haze days, There was a distinct accumulation process of VOCs at the beginning of the haze event, and the mixing ratios of VOCs maintained at the high levels until to the end of pollution when the mixing ratios of ambient VOCs recovered to the normal concentration levels in a few hours. Some reactive and toxic species increased remarkably as well, which indicates a potential health risk to the public in terms of VOCs. Eight sources were resolved by PMF, and results revealed gasoline exhaust was the largest contributor (32–46%) to the ambient VOCs in Beijing. Emissions of gasoline exhaust surged from 13.46 to 40.36 ppbv, with a similar variation pattern to total VOCs, indicating that high levels of VOCs were largely driven to by expanded vehicular emissions. Emissions of biomass burning also increased noticeably (from 2.32 to 11.12 ppbv), and backward trajectories analysis indicated regional transport of biomass burning emissions. Our findings suggested that extremely high levels of VOCs during the haze event was primarily attributed to vehicular emissions, biomass burning and regional transport, as well as stationary synoptic conditions.

High-resolution historical emission inventories of crop residue burning in fields in China were developed for the period 1990–2013. More accurate time-varying statistical data and locally observed emission factors were utilized to estimate crop residue open burning emissions at provincial level. Then pollutants emissions were allocated to a high spatial resolution of 10 km × 10 km and a high temporal resolution of 1 day based on the Moderate Resolution Imaging Spectroradiometer (MODIS) Fire Product (MOD/MYD14A1). Results show that China’s CO emissions have increased by 5.67 times at an annual average rate of 24% from 1.06 Tg in 1990 to 7.06 Tg in 2013; the emissions of CO2, CH4, NMVOCs, N2O, NOx, NH3, SO2, PM2.5, OC, and BC have increased by 595%, 500%, 608%, 584%, 600%, 600%, 543%, 571%, 775%, and 500%, respectively, over the past 24 years. Spatially, the regions with high emissions had been notable expanding over the years, especially in the central eastern districts, the Northeastern of China, and the Sichuan Basin. Strong temporal pattern were observed with the highest emissions in June, followed by March to May and October. This work provides a better understanding of the spatiotemporal representation of agricultural fire emissions in China and can benefit both air quality modeling and management with improved accuracy.