Source Apportionment of Fine and Coarse Particulate Matter in Industrial Areas of Kaduna, Northern Nigeria

This study was conducted to investigate the sources of fine and coarse airborne particulate matter in an urban environment in Nigeria. A total of 278 samples were collected over a twelve-month period from two industrial areas (Kudenda agricultural processing AP and Refinery industries NNPC) in Kaduna, Northern Nigeria for PM2.5 and PM2.5-10 on nuclepore polycarbonate filters using a Gent sampler. Elemental concentrations and black carbon analyses were performed using X-Ray fluorescence (XRF) and optical transmissometry respectively. The annual average concentrations for PM2.5 at each site (Kudenda and NNPC) were 135.7 mu g m(-3) and 37.2 mu g m(-3) and for PM2.5-10, concentrations were 269.2 mu g m(-3) and 97.4 mu g m(-3), respectively. These values exceeded the Nigerian Annual National Ambient Air Quality Standard (NAAQS) of 15 mu g m(-3) for PM2.5 and 60 mu g m(-3) for PM10. Positive matrix factorization (PMF) was used to identify sources and quantify their contribution to pollutants at the sampling sites in one of the most industrialized cities in Nigeria. Four sources were resolved for both PM2.5 and PM2.5-10 and were identified as: Residual oil 49% (17.16 +/- 0.04 mu g m(-3)), Soil 29% (10.36 +/- 0.26 mu g m(-3)), Continental dust 18% (6.20 +/- 0.18 mu g m(-3)), and Motor vehicles emissions 4% (1.56 +/- 0.02 mu g m(-3)) for PM2.5 while that for PM2.5-10 were Soil 50% (27.37 +/- 1.03 mu g m(-3)), Continental dust 21% (11.55 +/- 0.26 mu g m(-3)), Vehicular emissions 18% (9.87 +/- 0.03 mu g m(-3)), and Petrochemical 11% (6.23 +/- 0.02 mu g m(-3)). About 82% and 79% were attributed to anthropogenic sources for both fine and coarse samples, respectively. Continental dust was associated with northwesterly and northerly regional transport. Residual oil combustion was the predominant fine PM source and was attributed to fuel oil combustion for power generation and process energy within the local industrial areas. Although transported continental dust is an important source, the majority of the airborne PM in this industrial area was the result of local emissions.