长江三角洲区域本底大气中致酸气体体积分数变化特征

利用2003-12—2004-11浙江临安区域大气本底站大气NOx、SO2体积分数的连续观测资料,分析其季节变化和日变化特征。结果表明：长江三角洲区域本底大气中致酸气体NOx、SO2体积分数值均为冬季最高,分别为23.81×10^-9和37.3×10^-9,主要受来自东北方向宁、沪区域城市群的相对高浓度污染物随气团传输影响;夏季最低,主要是局地源的贡献。降水对SO2去除作用明显,对NOx去除效果不大。NOx体积分数值冬季的日变化最为明显,呈现出一低一高的双峰型,09：00出现较高体积分数值,18：00出现最高体积分数值;而夏季为单峰型日变化,07：00出现最高体积分数值。SO2冬、春季的日变化明显,最高体积分数值出现在06：00左右,最低体积分数值出现在15：00左右。该区域NO2全年空气质量达到《环境空气质量标准》（GB 30952—1996）一级标准,SO2冬、春季超标较多,受到人类活动影响较明显。NO2和SO2空气污染指数在12月最大,分别为50和93。该区域NO2和SO2并未出现“周末效应”。

Features of Acidic Gases in Background Air of Yangtze River Delta

Based on the observations at Lin＇an regional background station in Zhejiang Province from December 2003 to November 2004, the seasonal and diurnal variations of NOX and SO2 concentrations are analyzed. Result shows that the winter background concentrations of acidic gases NOx and SO2in the Yangtze River Delta region are the highest with 23. 81× 10^-9and 37. 3 × 10^- 9 （volume fraction） ,respectively, mainly affected by the relatively high concentration contamination transportation from the urban agglomeration of Shanghai-Nanjing area to the northeast of Lin＇an. The concentrations of acidic gases are the lowest in summer, mainly contributed by the local emission sources. Rainfall can obviously scavenge SO2, but it has low effect on NOx. The diurnal variation of NOx concentration presents a typical bimodal pattern with the higher value at 09：00 BST and the maximum at 18：00 BST in winter, while the variation is an unimodal pattern with the maximum at 07：00 BST in summer. The diurnal variation of SO2 concentration is remarkable in winter and spring with the maximum around 06：00 BST and the minimum around 15：00 BST. The air quality of annual regional NO2 conforms to the primary standard of GB 30952--1996 （Ambient Air Quality Standard）, but SO2 concentration exceeds the allowable limit notably in winter and spring for the obvious influence of human activity. Air pollution in-dexes of NO2 and SO2 reach the maximums 50 and 93 in December ,respectively. The weekend effect of NO2 and SO2 does not happen in this region.