咸阳市区夏季挥发性有机物污染特征及来源解析

Pollution characteristics and source apportionment of VOCs in urban areas of Xianyang in summer

挥发性有机物(VOCs)是臭氧(O_(3))生成的重要前体物,对其来源进行解析具有重要意义.本研究于2021年夏季采集了咸阳市市区3个点位的VOCs并分析其浓度特征,利用正定矩阵因子分解法(PMF)、最大增量反应活性系数法(MIR)和气溶胶生成系数法(FAC)等方法对VOCs进行了来源和环境影响分析.结果表明,2021年夏季咸阳市区VOCs的平均浓度为(51.96±21.50)μg·m^(-3),烷烃占比(43.22μg·m^(-3),84.81%)最大,其次为芳香烃(6.37%)、烯烃(5.62%)和炔烃(3.20%),烷烃浓度显著高于汾渭平原其他城市;咸阳市区VOCs浓度呈双峰的日变化特征,峰值分别出现在11:00和23:00.通过PMF解析出VOCs排放源依次为机动车源(33.15%)、油气挥发源(24.18%)、工业源(17.82%)、燃烧源(16.80%)和植物源(8.05%),其中,机动车源(47.39%)对实验中学VOCs贡献最大.VOCs的臭氧生成潜势(OFP)为83.16μg·m^(-3),烷烃贡献(54.45%)最大,机动车排放和油气挥发对市区O_(3)生成贡献较大,其中,实验中学OFP最大(102.89μg·m^(-3)).芳香烃对VOCs的二次有机气溶胶生成潜势(SOAp)贡献(77.70%)最大,工业源(44.48%)对市区SOAp贡献较大.控制机动车、油气挥发源及燃烧源是减少咸阳市区夏季O_(3)和SOA生成的关键.

Volatile organic compounds (VOCs) has been considered as the important precursors for ozone (O_(3)) formation,so it is of great significance to analyze VOCs sources.In this study,VOCs were collected and analyzed in three sampling sites of Xianyang during summer.Meanwhile,the sources and environmental impact of VOCs were analyzed used positive definite matrix factorization (PMF),maximum incremental reactivity coefficient (MIR) and aerosol generation coefficient (FAC),respectively.The average VOCs concentrations in Xianyang was (51.96±21.50)μg·m^(-3),and alkane contributed most (43.22μg·m^(-3),84.81%),followed by aromatics (6.37%),alkenes (5.62%) and alkynes (3.20%).The concentrations of alkane in Xianyang were significantly higher than those of other cities in Fen-Wei Plain.The diurnal variation of VOCs exhibited the bimodal trend,with the peak value appearing at 11:00 and 23:00,respectively.The results of PMF exhibited that vehicle emissions (33.15%),gasoline evaporation emissions(24.18%),industrial emissions (17.82%),combustion emissions (16.80%) and biogenic emissions (8.05%) were the main sources of VOCs.And the site of Shiyan Middle School had the largest vehicle emissions contribution(47.39%).The ozone formation potential(OFP) of VOCs was 83.16μg·m^(-3),with the high contribution from alkanes (54.45%),which was higher than other cities in the Fen-Wei Plain.Vehicle emissions and gasoline evaporation emissions contributed most to the formation of O_(3).The site of Shiyan Middle School had the largest OFP value (102.89μg·m^(-3)).Aromatic contributed the most (77.70%) to secondary organic aerosol formation potential (SOAp),and industrial emissions (44.48%) contributed most to SOAp in Xianyang.Therefore,the control of vehicle emissions,gasoline evaporation emissions and combustion emissions were the key point to reduce the formation of O_(3) and SOA in Xianyang during summer.