2015~2018年桂林市空气污染特征分析

Air Pollution Characteristics Analysis in Guilin from 2015~2018

摘要: 根据桂林市2015~2018年大气主要污染物和气象数据的在线监测数据，分析了各污染物的浓度水平、季节变化、后向轨迹特征及气象条件影响。结果表明，2015~2018年桂林市的主要污染浓度为PM_2.5、PM₁₀和O₃，其中各污染物浓度呈现逐年下降的趋势，PM_2.5、PM₁₀浓度存在明显的冬高夏低的季节特征，而O₃则表现出秋高冬低的季节特征。桂林市主要大气污染物的月度变化，PM_2.5、PM₁₀、NO₂、SO₂以及CO的月均浓度变化趋势大致相似，均呈“U”型，最高值出现在1月、2月和12月，最低值出现在6月、7月和8月，1~5月污染物质量浓度开始下降，6~7月趋于平稳，8~12月呈上升趋势；O₃的变化趋势呈双峰结构，第一个峰值出现在4月和5月，第二个峰值出现在9月和10月。AQI月均值先减小后增大，冬季总体数值最大，将污染天数与桂林市周边监测点相比较，得出与桂林市的污染天数相似的周边监测点有永州、邵阳、郴州、衡阳、清远、来宾、和柳州。桂林市2015~2018年的中度污染、重度污染和严重污染的后向轨迹分析中，冬季桂林高空气团的污染来源在500 m、1000 m、1500 m上的气团轨迹主要来自西南方向，其次为东北方向，研究得出后向轨迹气团的轨迹方向与风向存在显著关系。

Abstract: Based on the online monitoring data of the main atmospheric pollutants and meteorological data in Guilin from 2015 to 2018, we analyzed the concentration levels, seasonal changes, backward trajectory characteristics and the influence of meteorological conditions for each pollutant. The results show that the main pollution concentrations in Guilin from 2015 to 2018 were PM_2.5, PM₁₀ and O₃, in which the concentration of each pollutant showed a decreasing trend year by year, with PM_2.5 and PM₁₀ concentrations having obvious seasonal characteristics of high winter and low summer, while O₃ showed seasonal characteristics of high autumn and low winter. The monthly changes of the main air pollutants in Guilin, PM_2.5, PM₁₀, NO₂, SO₂ and CO have similar monthly average concentration trends, all in a “U” shape. The highest values appear in January, February and December, and the lowest values appear in June, July and August; the quality concentration of pollutants begins to decline from January to May, tends to stabilize from June to July, and shows an upward trend from August to December. The trend of O₃ showed a bimodal structure, with the first peak occurring in April and May and the second peak in September and October. The monthly average value of AQI first decreases and then increases, with the largest overall value in winter. Comparing the number of polluted days with the surrounding monitoring points in Guilin, it is concluded that the surrounding monitoring points with similar number of polluted days in Guilin are Yongzhou, Shaoyang, Chenzhou, Hengyang, Qingyuan, Laibin, and Liuzhou. In the backward trajectory analysis of moderate, heavy and severe pollution in Guilin from 2015 to 2018, the pol-lution sources of Guilin high altitude air masses on 500 m, 1000 m and 1500 m in winter were mainly from the southwest direction followed by the northeast direction, and the study concluded that there was a significant relationship between the trajectory direction of backward trajectory air masses and wind direction.