Abstract. The purpose of this study is to develop an emission inventory for major anthropogenic air pollutants and VOC species in the Yangtze River Delta (YRD) region for the year 2007. A "bottom-up" methodology was adopted to compile the inventory based on major emission sources in the sixteen cities of this region. Results show that the emissions of SO 2 , NO x , CO, PM 10 , PM 2.5 , VOCs, and NH 3 in the YRD region for the year 2007 are 2392 kt, 2293 kt, 6697 kt, 3116 kt, 1511 kt, 2767 kt, and 459 kt, respectively. Ethylene, mp-xylene, o-xylene, toluene, 1,2,4-trimethylbenzene, 2,4-dimethylpentane, ethyl benzene, propylene, 1-pentene, and isoprene are the key species contributing 77 % to the total ozone formation potential (OFP). The spatial distribution of the emissions shows the emissions and OFPs are mainly concentrated in the urban and industrial areas along the Yangtze River and around Hangzhou Bay. The industrial sources, including power plants other fuel combustion facilities, and non-combustion processes contribute about 97 %, 86 %, 89 %, 91 %, and 69 % of the total SO 2 , NO x , PM 10 , PM 2.5 , and VOC emissions. Vehicles take up 12.3 % and 12.4 % of the NO x and VOC emissions, respectively. Regarding OFPs, the chemical industry, domestic use of paint & printing, and gasoline vehicles contribute 38 %, 24 %, and 12 % to the ozone formation in the YRD region.

Abstract. Regional trans-boundary air pollution has become an important issue in the field of air pollution modeling. This paper presents the results of the implementation of the MM5-CMAQ modeling system in the Yangtze River Delta (YRD) for the months of January and July of 2004. The meteorological parameters are obtained by using the MM5 model. A new regional emission inventory with spatial and temporal allocations based on local statistical data has been developed to provide input emissions data to the MM5-CMAQ modeling system. The pollutant concentrations obtained from the MM5-CMAQ modeling system have been compared with observational data from the national air pollution monitoring network. It is found that air quality in winter in the YRD is generally worse than in summer, due mainly to unfavorable meteorological dispersion conditions. In winter, the pollution transport from Northern China to the YRD reinforces the pollution caused by large local emissions. The monthly average concentration of SO 2 in the YRD is 0.026 ± 0.011 mg m −3 in January and 0.017 ± 0.009 mg m −3 in July. Monthly average concentrations of NO 2 in the YRD in January and July are 0.021 ± 0.009 mg m −3 , and 0.014 ± 0.008 mg m −3 , respectively. The monthly average concentration of PM 10 in the YRD is 0.080 ± 0.028 mg m −3 in January and 0.025 ± 0.015 mg m −3 in July. Visibility is also a problem, with average deciview values of 26.4 ± 2.95 dcv in winter and 17.6 ± 3.3 dcv in summer. The ozone concentration in the downtown area of a city like Correspondence to: C. H. Chen (chench@saes.sh.cn) Zhoushan can be very high, with the highest simulated value reaching 0.24 mg m −3 . In January, the monthly average concentration of O 3 in the YRD is 0.052 ± 0.011 mg m −3 , and 0.054 ± 0.008 mg m −3 in July. Our results show that ozone and haze have become extremely important issues in the regional air quality. Thus, regional air pollution control is urgently needed to improve air quality in the YRD.

Nitrite (NO 2 − ) and its conjugate acid, nitrous acid (HNO 2 ), have long been recognized as a ubiquitous atmospheric pollutant as well as an important photochemical source of hydroxyl radicals (•OH) and reactive nitrogen species (•NO, • NO 2 , •N 2 O 3 , etc.) in both the gas phase and aqueous phase. Although NO 2 − /HNO 2 plays an important role in atmospheric chemistry, our understanding on its role in the chemical evolution of organic components in atmospheric waters is rather incomplete and is still in dispute. In this study, the nitrite-mediated photooxidation of vanillin (VL), a phenolic compound abundant in biomass burning emissions, was investigated under pH conditions relevant for atmospheric waters. The influence of solution pH, dissolved oxygen, and •OH scavengers on the nitrite-mediated photooxidation of VL was discussed in detail. Our study reveals that the molecular composition of the products is dependent on the molar ratio of NO 2 − /VL in the solution and that nitrophenols are the major reaction products. We also found that the light absorbance of the oxidative products increases with increasing pH in the visible region, which can be attributed to the deprotonation of the nitrophenols formed. These results contribute to a better understanding of methoxyphenol photooxidation mediated by nitrite as a source of toxic nitrophenols and climatically important brown carbon in atmospheric waters.

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In this study, nanoparticle (NP, diameter \ 100 nm) and respirable particles measurements were conducted at three different nanopowder workplaces, including the mixing area of a nano-SiO 2epoxy molding compound plant (primary diameter: 15 nm), bagging areas of a nano-carbon black (nano-CB) (primary diameter: 32 nm) and a nano-CaCO 3 (primary diameter: 94 nm) manufacturing plant. Chemical analysis of respirable particle mass (RPM) and NPs was performed to quantify the content of manufactured nanoparticles in the collected samples. Nanopowder products obtained from the plants were used in the laboratory dustiness testing using a rotating drum tester to obtain particle mass and number distributions. The obtained laboratory data were then used to elucidate the field data. Both field and laboratory data showed that NP number and mass concentrations of manufactured materials were close to the background level. Number concentration was elevated only for particles with the electrical mobility diameter [100 nm during bagging or feeding processes, unless there were combustionrelated incidental sources existed. Large fraction of nanomaterials was found in the RPM due to agglomeration of nanomaterials or attachment of nanomaterials to the larger particles. From this study, it is concluded that RPM concentration measurements are necessary for the exposure assessment of nanoparticles in workplaces.

Molecular markers in ambient organic aerosol (OA) provide highly specific source information. Their traditional quantification is based on offline analysis of filter samples, and the coarse time resolution and labor-intensive nature hugely limit the utility of the tracer data. In this study, hourly organic molecular markers in fine particulate matter were measured using a recently commercialized thermal desorption aerosol gas chromatography− mass spectrometry (TAG) technique at an urban location in Shanghai, China during a three-week campaign from 9 November to 3 December, 2018. Selected primary OA molecular markers, including anhydrosugars, fatty acids, aromatic acids, and polycyclic aromatic hydrocarbons (PAHs), were examined in detail. Their diurnal variations showed characteristic features representing the corresponding emission source activities. For example, stearic acid showed a clear peak around 7 pm, in accordance with the enhanced cooking activities during mealtime. Diagnostic ratios of related makers of different reactivities provided unique information in uncovering the source information and tracking evolution of the OA in the atmosphere, for example, ratios of levoglucosan to its isomers and K + identified crop residue burning as the major form of biomass burning (BB). Ratios of unsaturated and saturated fatty acids gave unambiguous indication of atmospheric degradation of unsaturated fatty acids after emissions. Oleic acid to stearic acid ratios in ambient data (0.83 ± 0.54) were lower than those in the source profiles (1.2−6.5). Furthermore, the oleic acid to stearic acid ratio was found to be highly correlated with O/C ratios (R p : −0.66), suggesting the possible utility of oleic acid as a model compound to examine the heterogeneous reaction of cooking-related OA. PAH ratio−ratio plots helped identify varying influences of major combustion sources associated with air masses of different origins, revealing that BB and coal combustion were dominant under the influence of long-range transport air mass, while vehicle emissions were dominant under local/median-range air mass influence. This study demonstrated the utility of high time-resolution organic markers in capturing the dynamic change of source emissions and atmospheric aging, providing observational evidence to support their use in source apportionment.

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