嘉善前体物与气象因子对臭氧生成的影响及臭氧潜在源区分析

Impacts of Precursors and Meteorological Factors on Ozone Pollution and Its Potential Sources in Jiashan

利用2017年嘉善善西超级站臭氧(O3)及其前体物(NOx和VOCs)以及气象因子(温度、湿度、风速)逐小时数据,分析了2017年全年NOx和O3的变化特征以及春季(4—5月)、夏季(7—8月)NOx和气象因子对O3生成的影响,利用O3生成潜势(OFP)评估了VOCs大气化学反应活性,并通过潜在源区贡献(PSCF)和浓度权重轨迹(CWT)方法分析了嘉善春、夏季O3潜在源区贡献特征。研究发现:O3日变化特征为单峰结构,NOx为弱双峰结构。O3浓度在3—9月较高,春、夏季O3浓度峰值分别出现在15:00和14:00,春、夏季的NOx、O3日变化与2017年全年日变化趋势基本一致。NOx对O3存在滴定作用,且低湿高温有利于O3浓度的升高。春、夏季O3生成潜势贡献均表现为烯烃>芳香烃>烷烃,由于烯烃光化学活性较高,夏季烯烃浓度升高导致其贡献较春季增长约18.1个百分点,且夏季VOCs平均最大O3增量反应活性高于春季。PSCF和CWT分析结果表明,嘉善春季的潜在源区主要为本地、西南方向和东南方向,夏季的潜在源区主要为本地、西北方向、西南方向以及东南方向。

Based on the hourly data of ozone precursors(NOx and VOCs),ozone(O3)and meteorology(temperature,humidity,wind speed)at Shanxi Super Station in 2017,the variation characteristics of NOx and O3 in the whole year of 2017 and the effects of NOx and meteorological elements on the formation of O3 in spring and summer were analyzed,the atmospheric chemical reactivity of VOCs was evaluated using OzoneFormation Potential(OFP),and Potential Source Contribution Function(PSCF)and Concentration-Weighted Trajectory(CWT)methods combined with weight factors were applied to study the potential source regions of O3.It was found that the diurnal variation of O3 was single-peak distribution,and the diurnal variation of NOx was weak bimodal structure.The concentration of O3 was higher from March to September,and the peak of O3 in spring(from April to May)and summer(from July to August)occured at 15:00 and 14:00 respectively.The diurnal variation trend of NOx and O3 in spring and summer was basically consistent with that of the whole year in 2017.The higher the concentration of NOx,the more inhibited the formation of ozone,and low humidity and high temperature were beneficial to the increase of ozone concentration.The contribution of OFP in spring and summer appeared as olefin>aromatics>alkanes.The olefin photochemical activity was relatively high,which contribution increased about 18.1 percentage points in summer.PSCF and CWT analysis showed that the potential sources of Jiashan in spring were mainly local,southwest and southeast,and in summer,the potential sources mainly were local,northwest,southwest and southeast.