Fate of PM2.5-bound PAHs in Xiangyang, central China during 2018 Chinese spring festival: Influence of fireworks burning and air-mass transport

Variations of levels,possible source and air mass transmission were investigated for 16 USEPA priority-controlled PAHs in PM2.5 during 2018 Chinese Spring Festival(CSF)in Xiangyang City,central China which is the North-South pollutant airmass transport channel of China.Totally 37 samples were collected.Mass concentrations of 16 PAHs for the Pre–CSF day(Pre–CSFD),during the CSF day(CSFD)and after the CSF day(Af–CSFD)are 33.78±17.68 ng/m3,22.98±6.49 ng/m3,and 8.99±4.44 ng/m3,respectively.High resolution samples showed that 16 PAHs are higher in the morning(06:00–11:00)or afternoon(11:30–16:30),than those in the evening(17:00–22:00)and at night(22:30–05:30),whereas the result is reversed during the CSFD.Fireworks burning can obviously increase the mass concentration of PAHs.Air mass trajectory indicated that Xiangyang is a sink area of pollutants for northwest and southeast,and the sources of the northeast and southwest.The air mass only can be transmitted out through northeast and southwest.It is effective for improvement of air quality in Wuhan and Hunan to control fireworks emission in Henan and local areas.Fireworks burning was an important source for PAHs during CSFD,biomass,coal combustion,and traffic emission were the main sources of PAHs for Pre–CSFD and Af–CSFD periods.The health risk on the CSFD was higher than the acceptable levels,especially during the intensive fireworks burning,the risk value far exceed 1.0×10^-4,controlling burning fireworks is required.

Estimating emissions from crop residue open burning in China based on statistics and MODIS fire products

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 resolution of1 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.

Typical atmospheric haze during crop harvest season in northeastern China：A case in the Changchun region

This study presents the mass concentrations of PM（2.5）,O3,SO2 and NOxat one urban,one suburban and two rural locations in the Changchun region from September 25 to October 272013. Major chemical components of PM（2.5）at the four sites were daily sampled and analyzed. Most of daily concentrations of SO2（7–82 μg/m^3）,O3（27–171 μg/m^3） and NOx（14–213 μg/m^3） were below the limits of the National Ambient Air Quality Standard（NAAQS）in China. However,PM（2.5）concentrations（143–168 μg/m^3） were 2-fold higher than NAAQS.Higher PM（2.5）concentrations（~ 150 μg/m^3） were measured during the pre-harvest and harvest at the urban site,while PM（2.5）concentrations significantly increased from 250 to400 μg m^（-3） at suburban and rural sites with widespread biomass burning. At all sites,PM（2.5）components were dominated by organic carbon（OC） and followed by soluble component sulfate（SO4^（2-））,ammonium（NH4~＋） and nitrate（NO3^-）. Compared with rural sites,urban site had a higher mineral contribution and lower potassium（K~＋and K） contribution to PM（2.5）.Severe atmospheric haze events that occurred from October 21 to 23 were attributed to strong source emissions（e.g.,biomass burning） and unfavorable air diffusion conditions.Furthermore,coal burning originating from winter heating supply beginning on October 18 increased the atmospheric pollutant emissions. For entire crop harvest period,the Positive Matrix Factorization（PMF） analysis indicated five important emission contributors in the Changchun region,as follows： secondary aerosol（39%）,biomass burning（20%）,supply heating（18%）,soil/road dust（14%） and traffic（9%）.