Professional Assessment of Air Pollution Levels and Chemical Characterisation of Particulate Matter in Kaduna Metropolis

Air quality in Kaduna metropolis, North West Nigeria, is degraded by emissions from industrial facilities, vehicular traffic, open biomass burning, and dust resuspension, yet comprehensive chemical characterisation of ambient particulate matter remains limited. This study conducted a professional assessment of air pollution levels and chemical composition of PM2.5 and PM10 particulate matter sampled at six monitoring stations in Kaduna metropolis representing industrial, commercial, residential, and peri-urban environments. High-volume air samplers collected particulate matter on pre-weighed filter papers over 24-hour periods at weekly intervals for three months. Gravimetric mass concentrations were determined. Filter extracts were analysed by inductively coupled plasma spectroscopy for metals including lead, chromium, nickel, arsenic, cadmium, and copper. Water-soluble inorganic ions including sulphate, nitrate, chloride, ammonium, and potassium were quantified by ion chromatography. Organic and elemental carbon fractions were determined by thermal-optical reflectance. PM2.5 concentrations at industrial sites reached 187 micrograms per cubic metre, far exceeding the WHO air quality guideline of 15 micrograms per cubic metre for 24-hour averages. Lead concentrations in PM2.5 were elevated near the industrial zone at 0.42 micrograms per cubic metre. Biomass burning markers including potassium and levoglucosan were prominent at residential sites. Secondary inorganic aerosol constituents dominated fine particulate chemistry at commercial stations. This comprehensive dataset provides an important foundation for evidence-based air quality management planning in Kaduna metropolis.

Keywords: particulate matter, air quality, chemical characterisation, Kaduna metropolis, PM2.5