| With the progress of economy and technology,the production of electronic products is increasing year by year,and the life cycle is gradually shortened.These lead to the rapid increase of electronic waste（e-waste）production,which has become an increasingly concerned problem in the world.During the E-waste dismantling process,a series of pollution would be produced,which affects the regional environment and endangers human health.At present,the researches on the pollution related to e-waste are mainly concentrated in the fields of heavy metals and organic flame retardants,but less attention is paid to the research of volatile organic compounds（VOCs）.However,e-waste dismantling will emit a large number of VOCs,which will not only lead to ozone pollution and particulate matter pollution,but also may have a direct toxic effect on human body.Therefore,it is necessary to systematically study the pollution characteristics of VOCs in e-waste dismantling area for a long time.In addition,the potential respiratory human health risk of typical VOCs should be carried out.In this thesis,a typical e-waste dismantling area in South China was selected as the research area.Sampling points were set in the e-waste dismantling area by using grid sampling method.The collection of VOCs in the air was carried out at 81 sites in the four seasons of2015 and the autumn of 2016 to 2018.To deeply know the pollution profiles of VOCs in the e-waste centralized dismantling park,besides the 81 sites,extra 9 sampling points were set up in this dismantling park in 2019 for four seasons.The pollution characteristics of VOCs in the atmosphere of e-waste dismantling area were systematically analyzed.Furthermore,the source contribution,atmospheric reactivity and health risk assessment of typical VOCs were evaluated.On the basis of pollution characteristics and health risk assessment of VOCs,the possible actual impact of e-waste emission pollution on human health was explored through the detection of respiratory gas of e-waste dismantling workers（before and after work）,local ordinary residents and control group.The main results are as follows:First,the temporal and spatial pollution characteristics of VOCs in different functional areas of e-waste dismantling town were studied.According to the statistics,in the whole region,the concentrations of isopentane,n-pentane,BTEX（benzene,toluene,ethylbenzene,xylene）,chlorofluorocarbons（HCFCs,trichlorofluoromethane,difluoro-dichloromethane）,1,2-dichloroethane（1,2-DCA）and 1,2-dichloropropane（1,2-DCP）were the highest.In each functional area,the concentrations of all substances were higher in autumn or winter.It is found that e-waste dismantling park is the hot spot of BTEX,1,2-DCP and 1,2-DCA,indicating that these substances may be the characteristic pollutants of e-waste emission.By PMF orthogonal matrix analysis,we found automobile exhaust（28%～56%）was the main sources of VOCs outside the e-waste dismantling park.At the same time,it was found that electronic waste（20%）is an important source of VOCs in e-waste dismantling park.Further,the cancer risks of the nine selected VOCs were assessed.The results showed that the health risk of 1,2-DCA,1,2-DCP,1,3-butadiene,benzene,ethylbenzene and chloroform in the e-waste dismantling park have possible cancer risk;the health risks of 1,2-DCA,1,2-DCP and1,3-butadiene outside the e-waste dismantling park have possible cancer risk.The non-carcinogenic risks of 23 kinds of VOCs were assessed,and the non-carcinogenic risk of all VOCs was lower than the safety threshold.Then,this thesis selected BTEX as a typical e-waste related VOCs to study the multi-year evolution process of VOC composition,concentration,spatial distribution,spatial correlation,atmospheric activity and health risk in e-waste dismantling area.In the four seasons of 2015,the median concentrations of BTEX were 19.07,8.07,3.73 and 5.92μg m-3,which decreased significantly.From autumn 2015 to autumn 2018,the concentration of BTEX showed no obvious trend.The BTEX spatial distribution showed an obvious evolution process in 2015,the BTEX concentration was higher in e-waste dismantling area in spring,higher in traffic area in summer,higher in plastic recycling area and residential area in autumn,and higher in residential area in winter.There was no of BTEX spatial distribution from 2016 to2018,when the BTEX concentration was higher in traffic area.Spatial correlation analysis found that the spatial correlation coefficient of BTEX pollution sources increased year by year from 2015 to 2018,indicating that the types of BTEX pollution sources in e-waste dismantling area were simplified year by year.Comparing the changes of toluene/benzene（T/B）ratio,it is found that the median value of T/B reached 6.5 in spring 2015,which may be affected by e-waste.In other sampling periods,the T/B value was between 1-2,which is in the characteristic range of traffic pollution.The photochemical activity of BTEX decreased significantly in 2015.The median values of secondary organic aerosol formation potential（SOAFP）from spring to winter were 81.41,41.12,13.85 and 41.12μg m-3,respectively.The median ozone formation potential was 66.87,33.10,10.53 and 21.16μg m-3,respectively.There was no significant change in photochemical activity between autumn 2016 and autumn 2018,the median values of SOAFP were 11.68,26.30 and 8.10μg m-3,respectively,and the median values of OFP were 9.11,21.33 and 6.87μg m-3,respectively.Health risk analysis showed that the carcinogenic risk of benzene in all years and seasons showed no carcinogenic risk.In the non-carcinogenic risk assessment results,the non-carcinogenic risk of all substances in BTEX at each sampling was less than 1,indicating no carcinogenic risk.The multi-year evolution of BTEX pollution in e-waste dismantling area shows that the concentration,composition and spatial distribution of regional BTEX pollution change significantly during the period of e-waste centralized dismantling and reconstruction,and there is no obvious inter-annual variation trend after centralized dismantling.Finally,this thesis selected the typical exposed population in the e-waste dismantling area and took students or residents in Guangzhou as the control population.The VOCs of exhaled air were detected by PTR-TOF-MS（proton transfer time of flight mass spectrometry）online to study the VOCs exposure characteristics and metabolic characteristics of the typical exposed population in the e-waste dismantling area.Results showed that smoking and background concentration were the main factors interfering with the detection of VOCs in exhaled breath..The average background concentrations of C6～C9 benzene series were 0.69,0.70,0.72 and 0.69 times higher than those before work,but the average concentrations in exhalation were 1.59,1.45,1.27 and 1.03 times higher than those before work,which proved that the e-waste workers had a certain absorption of benzene series during their work period.The exhaled methanol and isoprene of e-waste dismantling workers after work was significantly lower than that of workers before work,tricycles drivers,local residents and control group,indicating that e-waste dismantling may interfere with human metabolism,and this interference has been eliminated before work.Through the comparison of heat map,we found that the composition of VOC in the exhaled breath of local residents was less different from that of the control group,and the difference between the tricycle drivers and workers after work and the control group was more obvious.Finally,through PCA analysis,we found that the difference of breath composition between the local residents and the control group was the smallest,while the difference between the tricycle driver and the control group was the largest.The difference between the e-waste dismantling workers after work and the control group was greater than that before work.The above results show that the residents in the e-waste dismantling area are less affected by e-waste,while the e-waste dismantling workers inhale benzene series during work,and the natural metabolism of e-waste dismantling workers may be disturbed by e-waste.To sum up,this paper analyzes the seasonal and spatial and temporal pollution characteristics of VOCs in typical e-waste disposal areas and the spatial and temporal evolution characteristics over the years,determines the sources of regional VOCs pollution and health risks,and preliminarily discusses the metabolic characteristics of expiratory VOCs in typical exposed people,which provides theoretical support for scientific management of e-waste.Moreover,the application of expiratory VOCs diagnosis in the field of environmental health was expanded. |
PDF Full Text Request