Abstract: Spatial and temporal variation of PM₁₀and SO₂over Beijing area is obtained by analysis of monitoring data in 1999 and 2000. Random walk simulations are carried out to reveal impact of the urban emission to whole simulation domain. Accumulation effect of air pollutants in this area is also discussed. Results show that 1) Spatial distribution of PM₁₀and SO₂concentration is centered to urban area of Beijing and characterized by distinct diurnal and seasonal variation. 2) Diurnal variation of air pollutant concentration in urban area differs o bviously from that in clean station Dingling (background site). The former peaks twice in a day while the latter has a single peak. 3) Conditional statistics of monitoring data with the support of the random walk simulations show evident in fluence of urban emission to the clean station, Dingling. 4) Air pollutants may accumulate essentially over the simulation domain in winter, with a time scale 2-5 days approximately. The advection-diffusion factor plays a crucial role in the local accumulation process of air pollutants.

Key words: air pollution, temporal and spatial variation, accumulation, Beijing area

摘要： 用1999年和2000年的监测资料结合随机游走大气扩散模式分析北京地区PM₁₀和SO₂浓度的时空变化、城区污染排放对整个区域的作用和影响、以及污染物在区域内的累积效应。结果表明：(1) 北京地区污染物浓度具有以城区为中心的空间分布特点和季、日变化规律。(2) 城区和清洁对照点的污染物浓度平均日变化具有显著差异，城区基本呈双峰分布，清洁对照点定陵则基本为单峰分布。(3) 由扩散模拟的情况对定陵站的监测浓度进行条件性统计分析，结果明确反映了城区污染扩散对定陵站浓度的影响。(4) 北京冬季从城区排放的污染物在当地累积的情况明显，累积的时间周期大致为2～5d；输送扩散因子在污染物局地累积的过程中起着关键性的作用。

关键词: 大气污染, 时空分布, 累积效应, 北京地区