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First Measurements of PM2.5 in Kinshasa, Democratic Republic of Congo (DRC)
CELESTE MCFARLANE, V. Faye McNeill, Daniel Westervelt, Columbia University
Abstract Number: 239
Working Group: Aerosol Exposure
Abstract
With an estimated annual count of 780,000 premature deaths linked to air pollution in Africa, there is a great need for improved air pollution monitoring efforts to motivate the policy changes necessary to improve health outcomes. Kinshasa, DRC is a megacity with over 11 million inhabitants and no reference grade air pollution monitors, leading to much concern for air quality. Recently, a few reference grade monitors have been deployed elsewhere in Africa, including Kampala, Uganda. Reference grade air quality monitors can serve as an important basis for the correction and calibration of low cost sensors (LCS) for air quality monitoring. While LCS offer a path to remedy the lack of air pollution data in Africa, they are affected by environmental factors such as temperature and humidity, leaving a need for a correction factor to establish high quality data.
We present the first ever in-field calibration of LCS against reference grade monitors in Kampala, Uganda. A Purple Air PM2.5 monitor was colocated next to the Kampala US Embassy BAM-1020 in August 2019. Raw Purple Air data is strongly correlated with BAM (r = 0.94), but has a mean absolute error of approximately 12 μg/m3. Two calibration models, multiple linear regression and a random forest machine learning approach show that the mean absolute error decreased to less than 0.01 from 12 μg/m3 with the correlation improved to r = 0.96. We then apply the colocated in-field correction factors to four Purple Air sensors in Kinshasa, DRC and one in neighboring Brazzaville, collecting data from as far back as April 2018. This results in a high quality sensor network data set. Data shows peaks from June-September, when rain is infrequent, with a trend of decreasing peak size every calendar year (approx. 80 μg/m3 in 2018, 55 μg/m3 in 2019 and 38 μg/m3 in 2020) . Regionally averaged diurnal trends show a peak of approximately 48 μg/m3 at 6 pm GMT (7 PM WAT). Comparing data from the COVID lockdown period of 2020 to that of 2019 shows a reduction in PM2.5 concentrations from 45 μg/m3 in April of 2019 to approximately 10 μg/m3 in April of 2020. All of the pre-COVID values are well above the US EPA national air quality annual mean standard for PM2.5 of 12 μg/m3 , suggesting a need for air quality policy reform in Kinshasa, DRC.