高速路机动车尾气与森林排放挥发性有机物对区域大气臭氧的综合影响研究

Tropospheric ozone is formed through the photochemical reactions between volatile organic compounds (VOCs) and nitrogen oxides (NOx).VOCs and NOx are the major precursors of the tropospheric ozone and they are the key materials of city photochemical smoke..Nowadays much attention has been focused on to the city photochemical smoke but few attention is paid to ozone formation of forest far from cities, with a great amount of vehicular emission from the highways across the forest. The contact region between highways and forest exists a large of vehicles NOx and biogenic VOCs emissions, which implies there is a strong potential for ozone formation. High ozone level is a potential threat for the neighboring and the region forest ecological system..The contact region of highway-forest in the atmospheric environment is the research object of this proposal, and the mechanism and related factors of ozone formation referring to the emissions of highway vehicular exhaust and forest are planned to do detailed researches. The research contents include: (1) Through the observation the concentrations of atmospheric nitrogen oxides, volatile organic compounds and ozone on the contact region of highway-forest, analysis the contribution of vehicle exhaust emission and sensitivity of ozone formation, the sensitivity will determine which precursor (NOx or VOC) emission reduction will be more effective for decreasing the ozone formation; (2) To study the influence of meteorological factors (sun radiation intensity, pressure, temperature, humidity, wind speed) on ozone formation and transmission. .The purpose of the proposal is to know the spatial and temportal variations of ozone and the sensitivity of ozone formation influenced by vehicle exhaust on the contact region of highway-forest, analyze the contribution of vehicle exhaust on ozone formation in the contact region. This study can provide some scientific basis for reasonable control ozone pollution.

大气中氮氧化物和挥发性有机物，是城市臭氧的主要前体物和光化学烟雾形成的关键物质。穿越森林的高速公路周边存在大量植物排放的挥发性有机物和来自机动车尾气的氮氧化物，具有较强的臭氧生成潜势，对周边森林生态环境可能构成严重威胁，但目前尚无系统研究。本项目以高速路-森林接触带大气环境为研究对象，对高速路机动车尾气和森林挥发性有机物排放生成臭氧的机制及相关影响因素进行研究。研究内容包括：（1）通过观测高速路-森林接触带大气氮氧化物、挥发性有机物和臭氧浓度，分析机动车尾气氮氧化物排放对臭氧生成的贡献及其敏感性；（2）研究高速路-森林接触带气象因素（太阳辐射强度、气压、湿度、温度、风速）对臭氧生成及传输的影响。本项目旨在认识受机动车尾气排放影响的森林区域大气臭氧的时空特征及生成的敏感性，明确机动车尾气对森林区域臭氧生成的贡献率，为合理控制臭氧污染提供科学依据

本项目基于大气氮氧化物(NOx)和挥发性有机化合物(VOCs)在太阳辐射条件下生成大气臭氧(O3)这一反应原理，选取云贵高原地区高速路-森林接触带大气环境为研究对象,并另取昆明和玉溪两地大气臭氧污染特征为对照，采集大气臭氧、氮氧化物及挥发性有机物样品，对高速路-森林接触带大气污染物浓度时空分布特征及受气象条件的影响、臭氧生成敏感性进行分析。结果发现：（1）高速公路穿越森林生态系统中，光化学反应现象明显。夏季，光化学反应最为剧烈，其次分别是春季、秋季、冬季；昆明市中心东风东路，O3光化学反应春季＞秋季＞夏季＞冬季；玉溪市监测点，O3光化学反应夏季＞春季＞秋季＞冬季。(2) 在高速路-森林接触带区域，大气温度和紫外指数对污染物的浓度有重要影响，它们与O3、NOx显著正相关，与VOCs显著负相关;（3）高速路-森林接触带区域的VOCs/NOx呈现出早晚高午间低的特征，臭氧生成敏感性表现为：清晨至中午，O3生成对NOx浓度敏感；午后至傍晚，O3生成对VOCs浓度敏感。昆明市中心东风东路和玉溪市监测点臭氧生成对VOCs浓度比较敏感。(4) 利用臭氧生成潜势法分析了高速路-森林接触带区域大气VOCs生成臭氧的能力，结果表明对臭氧生成能力贡献最高的是烯烃;在夏季森林区域排放了大量异戊二烯，其对臭氧生成潜力的贡献远高于东风东路和玉溪市监测点。本项目认识了受机动车尾气排放影响的森林区域大气臭氧的时空特征及生成的敏感性，明确了机动车尾气对森林区域臭氧生成有重要影响，为合理控制臭氧污染提供了科学依据。