| The emission of volatile organic compounds（VOCs）from industrial sources is extremely complex and remains challenging in the China’s actions on air pollution control.VOCs are not only key precursors to PM2.5 and ozone,but also have toxic and carcinogenic effects to human health.Understanding of source apportionment,atmospheric chemistry,and environmental impact of industrial VOCs is being one of key research areas in China’s complex air pollution.Here,we systematically compared and unveiled the pollution characteristics of VOCs and odorous VOCs in typical industrial areas,as well as their chemical transformations and potential environmental risks.A high time-resolution single photon ionization mass spectrometer（SPI-MS 3000）was used to conduct field observations of atmospheric VOC pollution at the surrounding areas of the chemical industrial parks in Pukou and Jiangning districts in Nanjing,Jiangsu Province.Main pollution characteristics such as the sources,contribution to secondary pollution,and health risks of VOCs were investigated and clarified.In addition,we focused on the odorous pollution characteristics of industrial VOCs,which has become the most strongly complained about by urban residents.Measurements and determinations of key odor-causing factors about speciation,odor thresholds,and strong irritation were made at the Xiangshui chemical industrial park in Yancheng,Jiangsu Province.On the basis of the SPI-MS full-survey spectra along with meteorological parameters,concentration variations,and odor thresholds,the emission characteristics containing distribution of risking sources from different industries,odor-causing factors,and migrations were identified.Next,the hazard index（HI）was employed to investigate the risk assessment of odorous VOCs.Overall,this study is anticipated to develop the research foundation for characterizing and identifying VOC pollution characteristics and odorous factors from industrial emission.Most importantly,this study will provide some insights into formulating effective VOC control measures,improving regional air quality and protecting public health.The main conclusions of this thesis are abstracted as follows:（1）This study investigated the levels of volatile organic compounds（VOCs）in the atmospheric environment of Pukou District（44.59±49.95 ppb）and Jiangning District（18.79±8.11 ppb）in Nanjing.Meteorological parameters and conventional pollutant observations showed that the wind speed at the Jiangning observation site was similar to that at the Pukou observation site,but the temperature was lower and the relative humidity was higher.The concentrations of six conventional pollutants were slightly higher in Jiangning District than in Pukou District,except for O3.Additionally,the diurnal variation patterns of VOCs detected at both observation sites were similar,with a decrease in concentration at noon and an increase in concentration in the early morning and evening.The high-value components of VOCs in the atmosphere of Pukou District were n-hexane（11.08±1.57 ppb）and trichloroethane（10.11±37.56 ppb）,while those in Jiangning District were trimethylbenzene（2.58±0.06 ppb）and n-tridecane（1.54±0.68 ppb）.The high-value components of secondary pollution contribution in Pukou District were trimethylbenzene,with ozone formation potential（OFP）and secondary organic aerosol formation potential（SOAFP）values of 74.05±15.7μg/m3 and0.73±0.16μg/m3,respectively,while those in Jiangning District were also trimethylbenzene,with OFP and SOAFP values of 92.62±2.37μg/m3 and 0.91±0.02μg/m3,respectively.The results of VOCs and NOX sensitivity analysis showed that the region belongs to a VOCs control zone,and controlling VOCs emissions in this region will effectively alleviate ozone pollution.（2）The positive matrix factorization（PMF）model identified four emission factors at the two study sites.In Pukou District,the highest proportion was industrial production+solvent use at 43.3%,followed by traffic emissions at 28.2%,trichloroethane industrial emissions at17.5%,and solvent use at 11.0%.In Jiangning District,the two dominant composite factors were traffic emissions+solvent use and industrial production+solvent use,accounting for31.0%and 27.4%,respectively,oil and gas volatilization accounted for 21.1%,and traffic emissions accounted for 20.5%.The results of the hybrid single-particle lagrangian integrated trajectory model（HYSPLIT）combined with concentration-weighted trajectory（CWT）analysis showed that there were potential VOCs pollution sources in Lishui District of Nanjing,Changzhou,Suzhou,and Nanchang from July to August 2022.From August to September 2021,there were potential VOCs pollution sources in Xuzhou,Nanjing,Suzhou,Shanghai,Hefei,and Hangzhou.The health risk assessment results showed that acrolein detected at both observation sites in Pukou District and Jiangning District was the main non-carcinogenic chronic risk substance,especially at the Jiangning observation site.The main risk substances at both sites included trichloroethane,hexachloro-1,3-butadiene,acrolein,and dichloropropene.（3）The results of a 48-hour mobile observation in Xiangshui Chemical Industrial Park showed that the TVOC concentration levels on September 9th and 10th were not significantly different,but an extreme high-value point appeared on September 10th,indicating that unorganized VOCs emissions at this point should be given extra attention.The detected VOCs mainly included toluene,aniline,diethylbenzene,nonane,trimethylbenzene,dibromomethane,1,1-dichloroethylene,hexene,methylcyclopentene,pentene and dichlorobenzene.The analysis of abnormal points showed that there were total volatile organic compounds（TVOC）pollution sources near some chemical enterprises,which may have been caused by the organic emissions from the relevant workshops of these enterprises.The health risk assessment results of related species showed that there were several substances with chronic carcinogenic risks（dominated by 1,2-dibromoethane,1,1,2,2-tetrachloroethane and 1,3-butadiene）in the study area.The HI values were all higher than the safety threshold,indicating that there was a chronic non-carcinogenic risk（dominated by aniline and 1,2,4-trichlorobenzene）in the area.By assigning graded values to odorous substances and screening out the top ten substances that can be perceived by the human body（mainly mercaptans and benzene compounds）,and combining with the meteorological conditions at that time,the sources of odorous pollutants were traced.（4）Offline supplementary analysis was conducted on VOCs in the atmosphere of Jiangning urban area in Nanjing,and the results showed that the average TVOC concentration was 29.04±14.89 ppb,which was lower than the measured results in other cities.Aromatic hydrocarbons were the most important VOC component in OFP values,indicating that prioritizing the control of aromatic hydrocarbons would be beneficial in reducing ozone pollution.By estimating the LCR and NCR of VOCs,which were consistent with online observations,some NCR and LCR values of substances such as acrolein and trichloroethylene exceeded the recommended threshold,while the overall health risk of other species was low except for a few compounds.In addition,PMF analysis identified 5 potential VOC emission sources,with traffic emissions contributing the most,followed by solvent use,biogenic emissions,oil and gas evaporation,and industrial emissions.However,in the afternoon,the contribution of traffic emissions and solvent use was low,while biogenic emissions became the largest contributor.PMF-MLR analysis successfully allocated the NCR of VOCs to 5 potential emission sources resolved by the PMF model,of which biogenic emissions were the most important source of NCR and contributed more than the sum of all other sources to afternoon samples. |
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