Measurements of Ambient Air Fine and Coarse Particulate Matter in tenSouth-East Nigerian cities

摘要

This study monitored fine particulate matter (PM) load with aerodynamic diameter ten micrometer or less (PM10) and twoand half micrometer or less (PM2.5) in ten urban centres in South-Eastern Nigeria in the dry and wet seasons fromDecember, 2008 to September, 2009 using photometric laser-based particle counter instrument. The results showed that theseasonal mean varied in the range of 55.81-17.09 to 921.34-532.60 -g.m-3 for the PM10 in the dry season and 14.38-3.01 to266.06-129.79 -g.m-3 for the wet season. The seasonal mean of (PM2.5) ranged from 21.69-9.93 to 122.88-33.90 and3.31-2.36 to 11.44-4.57 -g.m-3 for the dry and wet seasons respectively. Comparatively, the cities- PM10 load in the dryseason followed the order: Onitsha > Aba > Umuahia > Owerri > Enugu > Nsukka >Abakaliki > Afikpo > Orlu > Nnewi,while the order for dry season means of PM2.5 followed: Onitsha> Aba > Owerri > Umuahia > Abakaliki > Afikpo > Orlu >Enugu > Nsukka. The dry seasonal mean of PM10 and PM2.5 levels in all the cities exceeded the US annual National AmbientAir Quality Standard (NAAQS) of 50 -g.m-3 and 15 -g.m-3 respectively. The student t-test statistics revealed significantdifference between the dry and wet seasonal means of PM10 and PM2.5 (p<0.05) while correlation matrix showed that thePM10 and PM2.5 seasonal mean concentrations correlated positively (p<0.05). The study concluded that having 100% ofthese cities in the dry season for PM10 and PM2.5 and 60 % for PM10 in wet season exceeding the recommended annualguideline limit, portends public health risk particularly to people dwelling in the affected cities.