Visibility as a proxy for air quality in East Africa
Visibility as a proxy for air quality in East Africa
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DOI：
10.1088/1748-9326/ab8b12
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发表时间：
2020-04
影响因子：
6.7
通讯作者：
Ajit Singh;W. Avis;F. Pope
中科院分区：
文献类型：
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作者：
Ajit Singh;W. Avis;F. Pope
非洲的许多城市地区没有足够的监测方案来了解其空气质量。这项研究使用能见度作为PM污染的代表，以了解1974年至2018年三个东非城市的PM空气污染：阿迪斯，内罗毕和坎帕拉。总体而言，自20世纪70年代以来，东非能见度显著下降，其中内罗毕损失最大（60%），而坎帕拉（56%）和阿迪斯（34%）。这些变化可能是由于人为PM排放量增加。相应地，自20世纪70年代至今，坎帕拉、内罗毕和阿迪斯的PM污染水平估计分别增加了162%、182%和62%。观测到能见度的季节性变化，这在很大程度上是通过改变雨季和旱季的PM源和汇来解释的。通过比较不同RH条件下的平均湿度来研究平均PM吸湿性。据观察，PM吸湿性随着时间的推移在所有三个城市，这是一致的吸湿性低于环境背景的PM排放量增加。观测到PM的大的城市增量，当风从人口稠密的城市地区带来空气时，通常会出现能见度差。为了研究污染增加、人口和经济增长之间的交叉点，将污染的变化与现有的人口增长和GDP统计数据进行比较。在所有三个研究城市中，PM增加与国家GDP（和城市人口）之间存在显着的正相关关系。在研究期间，这些城市经历了人口和国家GDP增长的快速增长（主要由研究城市的经济驱动）。这导致了全市范围内燃料使用和机动化率的增加，这与PM排放增加以及能见度下降有直接联系。该研究表明，社会经济预测可能有助于预测未来的空气质量。
Many urban areas in Africa do not have sufficient monitoring programs to understand their air quality. This study uses visibility as a proxy for PM pollution to provide insight into PM air pollution in three East African cities: Addis Ababa, Nairobi and Kampala, from 1974 to 2018. Overall, a significant loss in East African visibility was observed since the 1970s, where Nairobi shows the greatest loss (60%), as compared to Kampala (56%) and Addis Ababa (34%). These changes are likely due to increased anthropogenic PM emissions. Correspondingly, PM pollution levels, in Kampala, Nairobi and Addis Ababa, are estimated to have increased by 162, 182 and 62%, respectively, since the 1970s to the current period. Distinct variations in seasonal visibility are observed, which are largely explained by changing PM sources and sinks in rainy and dry seasons. Average PM hygroscopicity is investigated by comparing average visibilities under different RH conditions. It is observed that PM hygroscopicity has decreased over time in all three cities, which is consistent with increasing emissions of PM with hygroscopicity lower than the ambient background. A large urban increment in PM is observed, with poor visibility typically occurring when the wind brings air from densely populated urban areas. To investigate the intersection between increasing pollution, population and economic growth, changes in pollution are compared to available population growth and GDP statistics. Significant positive correlations between increasing PM and national GDP (and city population) were found for all three study cities. These cities have undergone rapid increases in population and national GDP growth (driven predominantly by study cities’ economies) during the study period. This has resulted in increased rates of citywide fuel use and motorization, which provides a direct link to increased PM emissions and thus visibility loss. The study suggests that socio-economic forecasts may enable future air quality projections.