| In recent years,rapid industrial and urban development in China has endangered the environment and human health,thereby causing concern for China’s government and citizens.Among the major cities of China,Xi’an is located in the northern area and has become a rising environmental concern because of significant development in the last 20 years.Based on regional pollution assessment,air pollution in Xi’an comprises many pollutants such as O3,NOx,SO2,and atmospheric particulate matter(PM).Generally,the physicochemical properties of these pollutants and triggering higher toxicity are highly attributed to the source and meteorological characteristics of the concerning area.Therefore,the following studies were designed to understand accurate chemical compositions,toxicity,and potential sources of atmospheric PM in different time durations.(1)The impact of COVID-19 control on air quality has been prevalent for the past years,however,few studies have explored the toxicity of atmospheric particulate matter during the epidemic control.Therefore,this research highlights the characteristics and sources of oxidative potential(OP)and the new health risk substances environmentally persistent free radicals(EPFRs)in comparison to city lockdown(CLD)in the early days of 2019-2020.The results indicated that the average concentration of PM2.5 decreased by 48%during CLD.Concentrations of other air pollutants and components,such as PM10,NO2,SO2,WSIs,OC and EC were also decreased by 22%,19%,2%,17%,6%,and 4%respectively during the CLD,compared to the same period in 2019.Whereas only O3 increased by 30%during CLD.The concentrations of EPFRs in PM2.5 were considerably lower than in 2019,which decreased by 12%during CLD.However,the OP level was increased slightly during CLD.Moreover,both EPFRs/PM and DTTv/PM did not decrease or even increase significantly,manifesting that the toxicity of particulate matter has not been reduced by more gains during the CLD.Based on PMF analysis,during the epidemic period,the contribution of traffic emission was significantly reduced,while EPFRs and DTTv increased,which consisted of significant O3 and secondary aerosols.This research to able future research on human health effect of EPFRs and oxidative potential and can be also used to formulate the majors to control EPFRs and OP emissions,suggesting the need for further studies on the secondary processing of EPFRs and OP during the lockdown period in Xi’an.The COVID-19 lockdown had a significant impact on both social and economic aspects.The city lockdown,however,had a positive impact on the environment and improved air quality,no significant health benefits were observed in Xi’an,China.(2)The scientific community has expressed severe worry about the degradation of air quality caused by anthropogenic activity at night.Therefore,diurnal assessment in spring and winter of 2021 was conducted to investigate the direct hazardous effects of PM exposure as well as the contributions from diverse sources.The findings indicated that substantial OP/PM per unit mass,OP,and PM toxicity can occur at night due to PM chemical compositional variations and its sources(coal combustion,industrial emissions,and motor vehicle emissions),demonstrating significant exposure risk and oxidative toxicity.Further evidence that EPFRs promote the production of reactive oxygen species(ROS)includes greater EPFRs concentrations and their substantial connection with OP.Additionally,both children and adults received a methodical explanation and spatialization of the carcinogenic and noncarcinogenic dangers.This improved knowledge of PM diurnal production routes and harmful effects may help to direct policies to lessen PM toxicity and lessen illness brought on by polluted air.(3)Different anthropogenic activities and meteorological conditions in every season can have different influences on environmental pollution.Moreover,the diurnal based assessment of those seasons is also significantly important.Therefore,herein,the source pointed study was conducted to analytically explain the logic of triggered OP in summer and autumntime of 2021.The physiochemical alteration in examined samples verified enhanced OP,OP/PM unit mass and PM toxicity due to collaboration of several sources including secondary sulfate,atmospheric oxidation,dust sources,motor vehicle emissions and secondary nitrate.Additionally,the abundant concentration of carbonaceous contents(OC/EC)and WSIs(NO3-,SO42-,Ca2+,NH4+)in both PM10 and PM2.5 at nighttime of both seasons were attributed to primary source as largest contributor to atmosphere.Furthermore,the higher carbon-centered EPFRs concentration at nighttime due to haze was observed to have a stronger correlation with OP,causing ROS formation.Most importantly,this research laid a pathway for local governments to control the sources of air pollution to provide a pollutant-free environment.Collectively,these research chapters contribute to the novel understanding of air quality dynamics,emphasizing the relevance of assessing the environmental and health impacts of major events like CLD,the consequences of nighttime anthropogenic activities,and the seasonal variations in pollution sources.These findings have practical implications for policymakers and researchers,guiding efforts to improve air quality and public health in Xi’an and similar urban areas grappling with air pollution challenges. |
PDF Full Text Request