Pollution Characteristics And Health Risk Assessment Of Polycyclic Aromatic Hydrocarbons In PM_2.5 In Guangzhou

Objective: To study the pollution characteristics and identify the main source of atmospheric polycyclic aromatic hydrocarbons（PAHs）in PM_2.5 in Guangzhou,and to assess the health risk assessment of the population so as to provide the scientific basis for the environmental management departments in making relevant control policies and taking measures.Methods: The PM_2.5 samples were collected from three sampling points(the Tianhe District West Village（hereinafter referred to as "Tianhe District"）,Yuexiu District Dongfeng West Road(hereinafter referred to as "Yuexiu District",Baiyun District Shatai South Road（hereinafter referred to as "Baiyun District"）in Guangzhou in 2015 by using two paralleled intelligent large airflow samplers with PM_2.5 cutting head at each site.The concentrations of sixteen PAHs were detected by gas chromatography-mass spectrometry and using ratio method and principal component analysis method to identify its main source.Health risk assessment of PAHs in PM_2.5 via respiration exposure in adults and children by using the BaP toxicity equivalent factor and the health riskassessment models recommended by EPA.Results:（1）The total concentration of the sixteen PAHs（∑16PAHs）ranged from1.35 to 43.13 ng/m3 with a geometric mean of 6.58 ng/m3 during the sampling period in Guangzhou and the Baiyun District site had the highest average concentration of ∑16PAHs,follow by the Tianhe District site,Yuexiu District site.BghiP、BbF、IcdP、BaP、Chr、BkF、Flu、Pyr were the more content of the monomers and the sum of their mass concentration was 88.81% in ∑16PAHs,which was 88.15%、86.86% and 88.81% in Tianhe District、Yuexiu District and Baiyun District,respectively;BaP concentration varied from 0.09 to 5.44 ng/m3 and the annual geometric mean was 0.67 ng/m3,of which the Baiyun District site was close to the national average annual standard limit of 1.0 ng/m3.5 6rings PAHs had the highest percentage,follow by the decreasing order of 4 rings,3 rings,2 rings,however,there was no obvious difference between sampling points.（2）The total mass concentration of PAHs in Guangzhou has obvious seasonal variation characteristics,namely,winter > autumn > summer > spring,while the seasonal variation of Tianhe District and Yuexiu District were winter >autumn > spring > summer.Flu、Pyr、BaA and Chr had higher seasonal variation than other monomers and the period of BaP concentrations exceeded the national standard limit mainly concentrated in the winter（above 60%）.There was no obvious seasonal changes in 5 rings PAHs content,while the PAHs content of 4 rings was higher in winter and lower in summer or autumn,and 6rings PAHs were higher in summer or autumn than in winter.（3）The results of the source analysis showed that the main sources of PAHs in PM_2.5 in Guangzhou are the emission ratio of motor vehicle exhaust,coalsource and combustion source（firewood and so on）,which winter have higher coal source and combustion source than other seasons.There was no significant difference in the source of PAHs at the three sampling sites.（4）The BEQ of PAHs varied between 0.33ng/m3 and 12.21ng/m3 in Guangzhou with a geometric mean of 1.80 ng/m3.There were 72% of PM_2.5samples had a BEQ value exceeding the WHO BaP equivalent concentration threshold of 1.2 ng/m3,of which the outflow rate of the Baiyun District was93.62%,indicating a higher risk of cancer.（5）The average daily dose（ADD）by respiratory exposure for children,adult male and adult female in Guangzhou were 1.36E-07 mg/（kg·d）,2.07E-07mg/（kg·d）,1.97E-07 mg/（kg·d）during the study period,respectively;the annual average life-long carcinogenic excess risk（R）were 4.27×10-7,6.51×10-7,6.19×10-7,respectively;both ADD and R were adult male > adult female >Children,winter > autumn > summer > spring,Baiyun District > Tianhe District > Yuexiu District.And the average annual cancer risk for adults in Baiyun District site was 1.09×10-6 for male and 1.04×10-6 for female,respectively,which were slightly higher than the lowest acceptable level of 10-6and should be notice.（6）The annual average life expectancy loss for children,adult male and adult female in Guangzhou were 2.65 min,4.05 min and 3.85 min,respectively.The average loss of life expectancy in the winter for the population was higher than in other seasons and the difference between sampling points was not obvious.Conclusion:（1）PAHs in the atmosphere PM_2.5 in Guangzhou were in the relatively low pollution level in the domestic,among which the pollution degree of the BaiyunDistrict site Shatai South Road area was higher and it may be related to its sourrounding more factories and the construction of the campus;there were obvious seasonal variation characteristics and the most serious pollution of PAHs appeared in winter;the source of PAHs in PM_2.5 mainly from the motor vehicle exhaust emissions,coal source,source of combustion.In order to reduce the atmospheric PAHs in Guangzhou,it is of great significance to optimize the management of motor vehicles.（2）The average cancer risk of PAHs through the respiratory exposure pathway in PM_2.5 in 2015 within the acceptable level to the general population in Guangzhou,and it was at a low level in the domestic.However,the risk of carcinogenesis in winter is higher,especially in the Baiyun District Shatai South Road area,which should be attracted considerable attention.