Study On Photo Chemical Ozone Formation Mechanism In Highway-Forest Contact Zone Of Plateau

This paper is based on the atmospheric O3 is generated by NOx and VOCs under the solar radiation, selection of Yunnan-Guizhou plateau highway-forest ecosystems research on atmospheric ozone pollution characteristic and generation mechanism, and in contrast to the characteristics of atmospheric ozone pollution in the city of Kunming. Collection of atmospheric ozone, nitrogen oxides and volatile organic sample in highway-forest contact contact zone, analysis temporal and spatial distribution of air pollutant concentrations and the influence of weather conditions, gives this region affect sensitive pollutant ozone formation. The results as follow:1. In the highway-forest contact zone, photochemical reaction of ozone was obviously, NOx and VOCs showed a regular impact in O3 concentration in the conditiong of solar radiation, as follows:sunrise to noon, ozone concentrations continue to rise; afternoon to sunset, ozone concentrations continued to decline. In fine weather phenomenon is more prominent. In summer, the contact with the most violent photochemical reaction, followed by spring, autumn and winter. Average season concentrations of O3 meet the national standard (160μg/m3).2. Studies have shown that soil microbial emissions from large scale forest areas and vehicle exhaust were the main reason for high concentration of NOx features in highway-forest area, soil microbial emissions were also contribution to nitrogen oxides, but far below the vehicle exhaust emissions. VOCs were mainly from the forest vegetation emission, motor vehicle exhaust was less affected on concentration curve.3. Studies have shown that in the summer, highway-forest contact zone with O3 concentration was greater than the urban. In spring and autumn, VOCs concentrations were less than highway-forest contact zone in urban. Each season, NOx concentration and O3 generation were the largest in highway-forest contact zone4. In the highway-forest contact zone. temperature and UV index had significant impact on the concentration of pollutants, showed positively correlated with O3, NOx significantly and negatively correlated with VOCs. Air mass Source Research showed that air mass trajectory primarily throμgh mountains, forest areas, less affected by the surrounding urban transport affected.5. In the highway-forest contact zone, ratios of volatile organic compounds and nitrogen oxides showed higher at midday, lower in the morning and evening, VOCs/NOx were 0.36 (spring),0.25 (summer),0.35 (autumn) and 0.39 (winter), respectively. Far less than the critical ratios of urban atmospheric conditions typical 5.5. The sensitivity of ozone formation was:in the morning until noon, O3 was NOx sensitivity; afternoon to early evening, O3 was VOCs sensitivity.