乌鲁木齐大气污染特征及气象条件的影响

The Air Pollution Characteristics and the Impact of Meteorological Conditions in Urumqi

乌鲁木齐市一直是世界上污染最严重的城市之一。该文选取2004-2006年乌鲁木齐市3个环境监测站逐时的PM10、SO2、NO2浓度数据以及乌鲁木齐市气象站、米泉气象站同期逐时的13类气象要素进行分析。结果表明,乌鲁木齐市PM10、SO2浓度冬季均达到轻微污染水平,其它3个季节属于优良级别,NO2四季都属优良级别;这三类大气污染物四季日变化基本呈现双峰型结构。冬季PM10、SO2浓度峰值出现在12:00-14:00时,最小值则分别出现在凌晨7:00时、傍晚19:00时,其它季节最大值(最小值)多出现在早晨(傍晚/凌晨);三类污染物的空间分布各有不同,PM10、SO2都是南部城区浓度较大,NO2浓度则是北部城区居首;各类气象要素与SO2浓度的相关性普遍高于与颗粒物PM10的相关性。全年与热力因素有关的气象要素与PM10、SO2浓度的相关性非常突出,冬季则是云量、降水等因素的影响明显提高;受蒙古高压和天山山脉地形的双重影响,乌鲁木齐冬季盛行偏南风和偏北风,山谷风交替现象明显;PM10浓度随乌鲁木齐市气象站、米泉气象站风速的增加均是先下降后上升,风速拐点分别是5 m/s、3 m/s,东南风对于污染物的远距离输送贡献较大;无论市区、还是北部城区,在偏北风和东南风的情形下,市区颗粒物浓度都比较大。

Urumqi has been the one of cities where the air pollution is the most severe in the world. To understand the characteristics of atmospheric pollutants and the impact of meteorology conditions on pollutants in Urumqi, hourly concentration of PM10, SO2 and NO2at three environmental monitoring stations in Urumqi and 13 hourly meteorological elements in Urumqi and Miquan during 2004-2006 were analyzed. The results showed that the air quality characterized by PM10 and SO2had minor pollution in winter while that of other three seasons was good; the air quality characterized by NO2 was good in the four seasons. The daily trend of PM10, SO2 and NO2showed bimodal structure. The max value of PM10 and SO2in winter occurred during 12:00-14:00 and the min value of that existed at 7:00 and 19:00, while the max or min value of the other seasons occurred in the morning or evening. The concentration of PM10 and SO2in south part of the city were higher while that of NO2 in north part of the city was higher. The correlation relationship between meteorological elements and the concentration of SO2 are larger than that of NO2. The correlations of the meteorological elements related to atmospheric thermal factors and PM10 and SO2were obvious during the whole year, while the impact of cloud faction and precipitation on atmospheric pollutants in winter became larger. Winter prevailing winds in Urumqi were north and south wind due to the influences by the Mongolian high pressure and Tianshan Mountain. The PM10 concentration in Urumqi was shown'U'trend(decreased first and then increased) with the increase of wind speed in Urumqi and Miquan( the point of transition of the wind speeds 5 m/s and 3 m/s).Southeast winds were contributed more in the long distance transport of atmospheric pollutants. The PM10 concentrations were large under the north and southeast winds at the whole city.