【摘要】 为探讨2013—2019年京津冀及周边地区"2+26"城市PM_2.5重污染时空演变特征,对"2+26"城市7年间的大气环境监测网数据进行了统计分析。在年际变化上,重污染过程次数逐年下降,发生时长和强度分3个阶段大幅降低。相比2013年,2014—2016年重污染小时数、天数和峰值浓度均降低了一半左右,2017—2019年则下降了约80%。目前,区域重污染过程以持续1～2 d的较短过程为主。在季节分布上,全年重污染集中于秋冬季,其中冬季占比从60%升至80%,尤其是1月的重污染占比最高且有逐年增加趋势。在空间分布上,区域差异明显缩小,呈相对均匀化趋势,区域污染中心有所南移,南部的冀南豫北区域在区域重污染中的占比呈上升趋势。在污染成因基本类型上,污染排放导致的积累型为主要类型,占比约90%;沙尘型及烟花爆竹燃放型的总占比约为10%,虽然其占比较低,但近年的比重较稳定,未有明显下降趋势。更多还原

【Abstract】 This study summarizes the temporal and spatial evolution characteristics of severe PM_2.5 pollutions over the “2+26” cities in Beijing-Tianjin-Hebei and surrounding areas during 2013-2019. From the inter-annual perspective,the number of the severe pollution events decreased year by year,with the substantial reductions in both the duration and intensity of the pollution events by three phases. Relative to 2013,the number of hours,number of days,and the maximum concentrations of the severe pollution episodes were declined by approximately 50% during 2014-2016 and 80% during 2017-2019. At present,in the 70% area of the region,the severe pollution episodes last only for one to two days. Seasonally,the severe pollutions primarily occurred in autumn and winter,with the proportion of winter increased from 60% to 80%,and especially in January the proportion showed an increasing tendency. Spatially,the regional differences of the pollution degree became smaller,with a tendency of homogeneous distribution. The hotspot of the pollutions moved southward from southern Hebei to northern Henan. We classified the type of causes of the severe pollutions and found that the accumulation-mode caused by pollution discharge was dominated,accounting for about 90%,while dust and fireworks types accounted for 10% annually and kept the similar contribution in the total severe pollutions from 2013 to 2019.更多还原