Abstract. A number of campaigns have been
carried out to establish the emission factors of pollutants from fuel
combustion in West Africa, as part of work package 2 (“Air Pollution and
Health”) of the DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in
West Africa) FP7 program. Emission sources considered here include wood
(hevea and iroko) and charcoal burning, charcoal making, open trash burning,
and vehicle emissions, including trucks, cars, buses and two-wheeled
vehicles. Emission factors of total particulate matter (TPM), elemental
carbon (EC), primary organic carbon (OC) and volatile organic compounds
(VOCs) have been established. In addition, emission factor measurements were
performed in combustion chambers in order to reproduce field burning
conditions for a tropical hardwood (hevea), and obtain particulate emission
factors by size (PM0.25, PM1, PM2.5 and PM10). Particle
samples were collected on quartz fiber filters and analyzed using gravimetric
method for TPM and thermal methods for EC and OC. The emission factors of 58
VOC species were determined using offline sampling on a sorbent tube.
Emission factor results for two species of tropical hardwood burning of EC,
OC and TPM are 0.98 ± 0.46 g kg−1 of fuel burned (g kg−1),
11.05 ± 4.55 and 41.12 ± 24.62 g kg−1, respectively. For
traffic sources, the highest emission factors among particulate species are
found for the two-wheeled vehicles with two-stroke engines
(2.74 g kg−1 fuel for EC, 65.11 g kg−1 fuel for OC and
496 g kg−1 fuel for TPM). The largest VOC emissions are observed for
two-stroke two-wheeled vehicles, which are up to 3 times higher than
emissions from light-duty and heavy-duty vehicles. Isoprene and monoterpenes,
which are usually associated with biogenic emissions, are present in almost
all anthropogenic sources investigated during this work and could be as
significant as aromatic emissions in wood burning (1 g kg−1 fuel). EC
is primarily emitted in the ultrafine fraction, with 77 % of the total mass
being emitted as particles smaller than 0.25 µm. The particles and
VOC emission factors obtained in this study are generally higher than those
in the literature whose values are discussed in this paper. This study
underlines the important role of in situ measurements in deriving realistic
and representative emission factors.
Particle and VOC emission factor measurements for anthropogenic sources in West Africa