Diurnal and intra-urban particle concentrations in relation to windspeed and stability during the dry season in three African cities
Diurnal and intra-urban particle concentrations in relation to windspeed and stability during the dry season in three African cities
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DOI：
10.1007/s10661-008-0399-y
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发表时间：
2009-07-01
影响因子：
3
通讯作者：
Holmer, B.
中科院分区：
文献类型：
--
作者：
Eliasson, I.;Jonsson, P.;Holmer, B.
利用便携式颗粒物计数器研究了非洲三个不同规模城市(达累斯萨拉姆、瓦加杜古和哈博罗内)PM2.5、PM10和TSP的时空变化。在每个城市中指定了三个不同的区域(市中心、绿色住宅区和传统住宅区)和一个参照点，以检测城市内部和时间上的变异性。在市区进行了上午、中午和夜间的测量，而在现场期间连续在参照站进行了观测。内陆的哈博罗内和瓦加杜古的颗粒物浓度有明显的日变化规律，其中早高峰和夜间高峰最高。然而，在沿海的达累斯萨拉姆，由于空气延迟稳定，夜间高峰几乎没有出现。瓦加杜古参考站的颗粒物浓度非常高。由于PM2.5/PM10的比率很低(0.1-0.3)，车辆排放的直接贡献是次要的。大部分颗粒被认为是土壤颗粒，白天风速很高，夜间随着空气稳定和风速降低而下沉，土壤颗粒被卷进空气中。然而，在这三个城市，再悬浮都很重要，因为有未铺设道路网络的地区显示出悬浮颗粒的最高浓度。总体而言，中央商务区的颗粒物浓度最低。
The spatial and temporal variations of PM2.5, PM10 and TSP in three African cities of different sizes (Dar es Salaam, Ouagadougou and Gaborone) were investigated using portable particle counters. Three different areas (downtown, green residential and traditional residential) and a reference site were designated in each of the cities in order to detect intra-urban and temporal variability. Morning, noon and night measurements were conducted in the urban areas while observations at reference stations were made continuously over the field periods. A clear diurnal pattern in particle concentrations was found in inland Gaborone and Ouagadougou, with morning and night peaks where the latter was the highest. However, in coastal Dar es Salaam the night peak was almost absent due to delayed stabilisation of the air. Particle concentrations at the Ouagadougou reference station were extreme. The direct contribution of vehicle emissions are of secondary importance since the PM2.5/PM10 ratios are low (0.1-0.3). Much of the particles are supposed to be soil particles that are entrained in the air by daytime high windspeeds followed by nighttime subsidence as the air is stabilised and windspeed decreases. However, in all three cities, resuspension are important as areas with a network of unpaved roads showed the highest concentrations of suspended particles. Generally, the central business district had the lowest concentrations of particulate matter.