Assessment and Mapping of Black Carbon and PM2.5 Variability: A Case Study in Nairobi city
Abstract
Airborne particulate matter is of great concern in the global environment due to associated
negative effects on human health and environment, and its contribution to climate change.
Reported here is carried out evaluation and mapping of PM2.5 mass concentration and Black
Carbon (BC) in Nairobi city. Air sampling was conducted at nine selected sites within Nairobi
city between 17/05/2016 to 22/06/2016. Sampling was done for 8 hours and samples analyzed at
the Institute of Nuclear Science laboratory for Particulate Matter (PM2.5) and trace elements (Pb,
Mn, Zn, Zr, Fe and Cu). BC was analyzed at Gothenburg University, Sweden.
The mean 8-h PM2.5 concentrations in the nine sampling sites selected for the study ranged
between 147 ± 89 μg m-3 and 52 ± 4 μg m-3. Mean BC concentration for the nine sampling sites
ranged from 8.6 ± 3.3 μg m-3 to 2.1 ± 1.2 μg m-3. OLS dispersive models were further used to
map out the pollution levels across the city. Elemental content of the sampled fine particulates
included Cu, Mn, Zn, Fe, Pb, and Zr which were found to be above 50, 1210, 470, 200, 30 and
480 ng m-3 which was their respective detection limits. The detected trace elements accounted
for 15 % of the species in PM2.5, while BC accounted for 8 %. The highest mean concentration
was recorded for Fe, followed by Mn and Cu at 2800 ± 3800 ng m-3, 2600 ± 42 ng m-3, and 2200
± 38 ng m-3, respectively.
The WHO health guideline for 24-h mean PM2.5 concentrations is 25 μg m-3. This study
represents an eight hour mean hence it was not possible to directly compare the concentrations
with the WHO guidelines. However, it is evident that the values are very high if we consider the
low activity hours of the night. This means that the population like those driving in jam, traffic
police, pedestrians, or individuals living in apartments near the roadways, are all constantly
being exposed to high pollution levels. Long-term exposure to these pollutants can have
negative effects on public health such as respiratory and cardiovascular ailments, hence there is
need for intervention measures.
Publisher
University of Nairobi
Rights
Attribution-NonCommercial-NoDerivs 3.0 United StatesUsage Rights
http://creativecommons.org/licenses/by-nc-nd/3.0/us/Collections
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