Research On No_x Pollution In Xiangtan City Area

With the number of vehicles continuous increasing and the growth of energy consumption, NOx pollution in Xiangtan City is worsening, and affects the normal life and health of citizen. In order to control NOx pollution, we not only need to understand air quality characteristics and meteorological conditions effect in Xiangtan City, but also should determine the specific source of NOx and the concentration contribution of pollutant. So we can take effective measures to control the total emission of NOx and make the concentration of NOx within safe limit. This study is based on air quality characteristics and meteorological conditions effect in Xiangtan City, establishing NOx emission inventory, using CALPUFF atmospheric dispersion model for numerical simulation of NOx in the region, the following conclusions:(1) The ambient air of Xiangtan City shows complex pollution, the main pollutants are PM2.5 and PM10, followed by eight hours of O3, NO2 and SO2, the annual air quality compliance rate is 54%. The characteristics of NO2 pollution: Annual average concentration of four monitoring sites including Monitoring Station, Science and Technology University, Yuetang and Bantang exceed the standard, maximum in Yue tong, minimum in Bantang; winter is generally high concentration, summer is low; Week variation showed multimodal substantially, there is a peak on Tuesday, Thursday and Saturday; Daily average concentration in Yuetang exceeds the standard the most severely, followed by Zhaoshan, Bantang, Jianglu, Science and Technology University, Monitoring Station.; There are two peaks in sooner and later of hour average concentration, the two peaks at around 9:00 and 22:00, the lowest value at around 15:00.(2) The concentration of NO2 changing with the wind direction, when the wind comes from east-northeast, NO2 concentration is maximum, followed by the east and northeast, while southerly winds, NO2 concentration is generally small. Then NO2 concentration increasing with the wind power decreasing, and rising with the atmospheric stability enhancing.(3) The total emission of NOx in the Xiangtan City for the year 2013 is about 43144.26 t. The major survey industrial pollution shares the largest contribution of NOx, accounting for 84.70% of total emission. Followed by the main road vehicle pollution, small street vehicle pollution, and non-major survey industrial pollution, sharing 10.42%, 2.30% and 1.86% of total emission, respectively. The proportion of urban living pollution is least, and responsible for 0.72% of total emission.(4) By comparing the simulated and measured values, indicating that the CALPUFF model has good simulation result. The result shows that NO2 concentration exceeding the standard concentrates in the northeast region, including Yuetong, Monitoring Station, around Zhaoshan and along the Beijing-Zhuhai highway, Beijing-Zhuhai highway which is NO2 concentration along for the most concentrated area of high values, then low values of NO2 are mainly distributed in west of old city region and the edge of simulation area. The main contribution source of NO2 concentration is main road vehicle pollution, and high values are mainly concentrated along Beijing-Zhuhai and Shanghai-Kunming highway and interchanges in the eastern of simulation area.