| The problem of atmospheric ozone pollution in our country is becoming more and more severe.Ozone pollution not only affects the environment,but also endangers human health and causes large social and economic losses.Therefore,The study of the characteristics of regional atmospheric ozone pollution and ozone generation sensitivity is able to provide scientific control measures for regional ozone pollution prevention and control.In this study,we analyzed the characteristics of ozone pollution and the causes of ozone pollution based on typical pollution process which was based on monitoring data of the Jiulong River Estuary from 2015 to 2019.And we developed EKMA curves based on air quality models to identify the sensitivity of ozone production to precursors.That can provide effective measures for local ozone pollution control.The main components and results are as follows.This paper analyzed the spatial and temporal distribution characteristics of ozone and its precursors based on monitoring data of ozone,nitrogen oxides(NOx)and volatile organic compounds(VOCs)from eight stations in the Jiulong River Estuary from 2015 to 2019.The results show that ozone which has replaced particulate matter as the primary pollutant is increasing rapidly at a rate of 8.2±2μg/m~3 per year from2015-2019 in Jiulong River Estuary.Statistical analysis found that ozone concentration is higher in April,May,September and October,showing a seasonal pattern of high in spring and autumn and low in summer and winter,and the average daily concentration often exceeds the standard,with the most serious in 2018,with 118 days of exceedance.Ozone concentration always peaks in the afternoon from 14:00-16:00 due to intense afternoon light.Through Arcgis spatial interpolation analysis,it was found that the ozone concentration in the Jiulong River estuary was highest in the eastern region,and the high values in the central and western regions were spatially characterized by point-like distribution.The annual average concentration of NOx showed slight fluctuation.The monthly average concentration of NOx was higher in January-March,November and December,and the hourly concentration showed high values in the morning and evening,which was due to the morning and evening rush hours.The annual average concentration of VOCs was 77.69 ppb.Among them,alkanes and halogenated hydrocarbons accounted for a relatively high proportion of 32.1%and 32.0%respectively,while aromatic hydrocarbons,olefins and other categories accounted for14.5%,5.7%and 14.4%respectively,and the lowest was alkynes,which accounted for only 2.2%.The analysis of ozone generation potential(OFP)method found that olefins and aromatic hydrocarbons have high OFP values.The typical pollution processes of ozone pollution in the Jiulong River estuary in spring 2018 and autumn 2019 were selected to explore the relationship between ozone and precursor concentrations and meteorological conditions from the perspective of photochemical production and transport contributions of ozone.The results showed that the concentrations of NO2 increased significantly during the spring pollution process,and high temperature and low humidity meteorological conditions were observed.At the same time,the nighttime ozone concentration increased significantly compared with the daytime.Combining the backward trajectory and model simulation results,it was found that this spring pollution was mainly caused by the contribution of ozone transport from the Yangtze River Delta region and superimposed on the local photochemical generation.During the autumn pollution process,the analysis of the500hpa high altitude weather situation and the ground meteorological conditions reveals that the whole pollution process was in a high temperature and low humidity static and stable environment,which was very favorable for photochemical generation.Using backward trajectory and air quality model simulations,it was concluded that the pollution process in autumn was dominated by local photochemical generation with the contribution of high-altitude transport.External transmission was prone to ozone pollution,strengthening regional joint prevention and control of ozone pollution prevention and control was very important.The high ozone pollution months in the Jiulong River estuary in 2018 were selected as the study period,and the chemical activity of VOCs species and the pollution sources of VOCs were explored using the ozone generation latent potential method and PMF source analysis model.Two ratio methods,VOCs/NOx from monitoring data and HCHO/NO2 from satellite inversion data,were used to qualitatively analyzed the ozone sensitivity in the Jiulong River estuary.The results showed that olefins were the most active among VOCs in the Jiulong River estuary,and the PMF model resolved eight types of sources,among which motor vehicle emission sources contributed the most to VOCs.The Jiulong River estuary was mainly in VOCs-limited.Non-polluted and polluted days in April and October 2018 were selected for the study,and the air quality model was used to simulate the variation of ozone generation from precursors NOx and VOCs at different input ratios.The results showed that the greatest reduction in ozone generation occurred on pollution days when the percentage reduction of VOCs was in the range of 25%-75%.Therefore,the control of road mobile sources should be strengthened,and VOCs source emissions,especially olefins,should be strictly monitored.In terms of control objects,VOCs should be prioritized with NOx,and the best effect should be achieved when the reduction ratio of VOCs is in the range of 25%-75%. |
