中国超大城市不透水面扩张对对流层NO_2柱浓度的影响

Impact of impervious surface expansion on tropospheric NO_2 column density in Chinese megacities

基于Aura卫星的臭氧检测仪(OMI)数据及Landsat卫星影像,分别分析了中国7座超大城市2005—2017年的对流层NO_2柱浓度(TroNO_2浓度)时空变化规律和不透水面扩张模式,并探讨了二者之间的联系,结果表明:①7座城市总体表现为TroNO_2浓度先升高后降低、高值区域先扩大后收缩甚至消失的趋势.变化存在显著的周期性,冬季浓度远高于夏季.②各城市不透水面面积分别扩张至120%～200%,扩张模式多表现为由中心向四周辐射式扩张,不透水面的空间分布和扩张趋势与TroNO_2浓度高度相关.③各城市市辖区TroNO_2浓度与不透水面覆盖率(ISC)呈高度正相关,二者冷热点空间分布规律一致,松散型、紧凑型、密集型、高度密集型市辖区的TroNO_2浓度均值依次增加,发生不透水面扩张的区域标准化TroNO_2指数呈上升趋势.④自然条件、经济产业结构、机动车尾气排放、重大赛会的举办及相关政策等因素均与TroNO_2浓度密切相关.

We used Ozone monitoring instrument(OMI)data to generate the tropospheric NO2 column density(TroNO2)of 7 Chinese megacities from 2015 to 2007 and analyzed the characteristics of spatial and temporal distribution of TroNO2.We also explored the correlation between TroNO2 and the impervious surface of megacities.The results showed that:①Tropospheric NO2 column density of all 7 megacities increased first and then decreased,whose region with high value expanded firstly and then contracted or disappeared.There are significant cyclical changes in the concentration of each cityduring the year.And density of TroNO2 in winter is always higher than that in summer.②Comparing with 2005,Impervious surface area of each megacity in 2017 expanded 1.2~2 times,and the expansion appeared from city center to the periphery.While the spatial distribution and expansion trend of impervious surface are highly correlated with the density of TroNO2.③Tropospheric NO2 column density were highly positively correlated with the impervious surface coverage(ISC),and the distribution of cold and hot spots were consistent.The tropospheric NO2 column density of unstressed,stressed,impacted and degraded municipality increased in turn.The normalized TroNO2 index showed an upward trend on the region where impervious surface expansion happened.④Natural conditions,economic industrial structure,exhaust emission,major games and related policies were closely related to the tropospheric NO2 column density.