[Quantification of Ozone Pollution Transport Based on Four-dimensional Flux Method in Foshan, China].

Quantifying the contribution of transport processes to air pollution events has been a prominent challenge and an important need in regional air pollution prevention and control. The WRF-Chem model was used to simulate a typical regional ozone (O3) pollution event in Foshan, and the four-dimensional flux method was applied to quantify the transport fluxes of ozone and its precursors from the surrounding areas to Foshan and to clarify the contributions of the direct transport of ozone and transport of precursors. The average ozone flux from the surrounding areas to Foshan was 120.3 t·h-1, the volatile organic compound (VOCs) flux was 30.2 t·h-1, and the corresponding ozone formation potential (OFP) was 114.8 t·h-1. By counting the transport fluxes of each ozone pollution event, it was found that the city with the largest ozone flux into Foshan during the pollution period was Guangzhou (contributed 44%); the city with the largest input VOCs flux was Zhaoqing (contributed 48%). The analysis of ozone generation potential due to transported VOCs emissions found that oxygenated volatile organic compounds (OVOCs) contributed the most to OFP, accounting for 47% of the "maximum input events." OVOCs and aromatic hydrocarbons such as formaldehyde, xylenes, aldehydes, acetone, and phenols were the top five species contributing to the OFP, contributing more than 50% of the total OFP, mainly from industrial solvent sources.

Long-term trends of chemical characteristics and sources of fine particle in Foshan City, Pearl River Delta: 2008-2014.

Foshan is a major international ceramic center and the most polluted city in the Pearl River Delta (PRD). Here we present the results of the first long-term PM2.5 (particles <2.5µm) sampling and chemical characterization study of the city. A total of 2774 samples were collected at six sites from 2008 to 2014, and analyzed for water soluble species, elements and carbonaceous species. The major constituents of PM2.5 were sulfate, OC (Organic Carbon), nitrate, ammonium and EC (Elemental Carbon), which accounted for 50%-88% of PM2.5. PM2.5 and the most abundant chemical species decreased from 2008 to 2011, but rebounded in 2012-2013. After 2008, the chemical composition of PM2.5 changed dramatically due to the implementation of pollution control measures. From 2008 to 2011, SO4(2-) and NO3(-) were the two largest components; subsequently, however, OC was the largest component. The respective contributions of SO4(2-), NO3(-) and OC to the sum of water soluble species and carbonaceous species were 30.5%, 22.9% and 19.9% in 2008; and 20.2%, 16.5% and 30.2% in 2014. Distinct differences in nitrate and sulfate, and in mass ratio [NO3(-)]/[SO4(2-)] imply that mobile sources tended to more important in Foshan during 2012-2014. The results indicate that pollution control measures implemented during 2008-2014 had a large effect on anthropogenic elements (Pb, As, Cd, Zn and Cu) and water soluble species, but little influence on crustal elements (V, Mn, Ti, Ba and Fe) and carbonaceous species. The PMF method was used for source apportionment of PM2.5. Industry (including the ceramic industry and coal combustion), vehicles and dust were the three most important sources and comprised 39.2%, 20.0% and 18.4% of PM2.5 in 2008, respectively. However, secondary aerosols, vehicles and industry were the three most important sources and comprised 29.5%, 22.4% and 20.4% of PM2.5 in 2014, respectively. During the seven year study interval, the contributions of primary sources (industry and dust) decreased significantly, but secondary sources increased dramatically. Industry, dust and vehicles contributed 36.6µgm(-3), 13.9µgm(-3), and 9.2µgm(-3) to the reduction of PM2.5, respectively.

[Pollution Characteristics of Non-methane Hydrocarbons During Winter and Summer in Foshan City].

Thirty non-methane hydrocarbons(NMHCs) samples were collected and analyzed in Foshan City during winter 2014 and summer 2015. The concentrations of NMHCs during the sampling period were 122.30 µg·m-3 and 56.22 µg·m-3 in winter and summer, respectively. The five highest concentration species of NMHCs in winter and summer were in the following order: toluene (25.12 µg·m-3), m/p-xylene (13.76 µg·m-3), propane (9.17 µg·m-3), ethylbenzene (7.25 µg·m-3), ethylene (6.77 µg·m-3) and toluene (6.18 µg·m-3), m/p-xylene (5.21 µg·m-3), o-xylene (4.15 µg·m-3), ß-pinene(3.75 µg·m-3), propane (3.29 µg·m-3). Compared to 2008, the concentrations of NMHCs have dropped significantly. The proportions of aromatics, alkanes, alkenes and alkynes in NMHCs were 51.20%, 34.70%, 10.04%, 4.05% and 43.93%, 33.99%, 19.20%, 2.88% during winter and summer, respectively. The ratios of NMHCs/NOx were 0.90 and 1.88, indicating that the peak ozone concentrations in Foshan City were controlled by NMHCs during the sampling period, and the emissions of NMHCs should be further strengthened. The propylene equivalent concentration and ozone formation potential were 45.09 µg·m-3 and 40.64 µg·m-3, 392.77 µg·m-3 and 207.77 µg·m-3 in winter and summer. The m/p-xylene; toluene and m/p-xylene; isoprene had a very important influence on ozone formation potential. The ratios of Benzene/Toluene were 0.15 and 0.20 indicated that industrial process was the main source of NMHCs in Foshan City. Relative to 2008, isopentane didn't belong to the highest concentration of five pollutants for Foshan's NMHCs in this research, indicating the measures to prevent volatile gasoline impact on the environmental quality have achieved remarkable results.