基于双维度校验的珠三角区域臭氧生成机制长期时空演化特征识别

Identification of Ozone Formation Mechanism Long-term Spatio-temporal Evolutions in PRD Based on Two-dimensional Mutual Verification

臭氧(O_(3))污染已经成为我国主要城市区域大气环境的首要污染物,由于其生成与前体物之间呈现高度非线性的关系,O_(3)生成机制的识别对前体物的减排具有基础性的重要作用.针对常规方法难以较好对机制的长期演化特征进行识别问题,基于常规观测数据(O_(3)、NO_(2))和温度(T)与挥发性有机物活性(VOCR)之间的关系,从NO_(2)和T两个维度对珠三角区域O_(3)的生成机制进行了识别并做校验,分析了2006~2020年期间O_(3)的趋势变化规律和原因,研究了机制的长期演化特征.结果表明,O_(3)浓度随NO_(2)和T水平的升高呈现升高、稳定、下降和再次升高的趋势变化规律,当ρ(NO_(2))处于0~35、35~45、>45μg·m^(-3)和T处于>30、25~30、<25℃时,机制分别处于NO_(x)控制区、过渡区和VOCR控制区.不同时间段,随着T升高VOCR随之升高,推动了O_(3)浓度上升.由于前体物排放趋势变化和O_(3)生成机制状况不同,O_(3)浓度在不同时间段和T条件下的趋势变化规律不同.整体上,珠三角区域西部偏VOCR控制区,东部偏过渡区,两个维度机制的识别结果具有较高一致性.随时间变化,西部区域的过渡区向VOCR控制区转变,东部区域的VOCR控制区向NO_(x)控制区转变.在不同时间段,随着T升高O_(3)生成对NO_(x)的敏感性增强,随时间变化,高温和低温条件下O_(3)生成分别对NO_(x)和VOCR的敏感性增强.

Ozone(O_(3))pollution has become the primary pollutant in the atmospheric environment of major urban areas in China.Due to the highly nonlinear relationship between O_(3) and its precursors,the identification of the O_(3) formation mechanism(OFM)is fundamental to emission restraining.An overview of previous related investigations indicated that it is rather difficult to ideally recognize OFM long-term evolutions with conventional methods.In this study,based on the relationship between ambient temperature and volatile organic compound activity(VOCR)and O_(3) and NO_(2) conventional observation data from 2006 to 2020 in the Pearl River Delta(PRD),OFM was identified from the two dimensions of NO_(2) and temperature.Then,OFM was verified to ensure accuracy.Afterward,O_(3) concentration and OFM in different periods and temperature levels were analyzed.The results showed that O_(3) concentration presented a trend of increasing,stabilizing,decreasing,and increasing again with the increase in NO_(2) and temperature levels.Overall,NO_(x)-limited,transitional,and VOCR-limited corresponded to NO_(2) in 0-35μg·m^(-3),35-45μg·m^(-3),and greater than 45μg·m^(-3),and temperature ranged from higher than 30℃,25-30℃,and lower than 25℃,respectively.VOCR increased with the increase in temperature during different time periods,which promoted O_(3) to a higher level.O_(3) concentration in different time periods and temperature levels varied with precursor emission fluctuations in different OFM.On average,during 2006 to 2020,VOCR-limited and transitional were in the west and east of PRD,respectively,and OFM identified from NO_(2) and temperature dimension were consistent.The transitional tended toward the VOCR-limited in the west,and VOCR-limited in the east of PRD tended toward the NO_(x)-limited with time.O_(3) formation was more related to NO_(x) as temperature increased,and it became more sensitive to NO_(x) and VOCR at high and low temperatures,correspondingly.