ASSESSMENT OF POLLUTANT GASES AND AIR BORNE PARTICULATE MATTERS IN SOME SELECTED CITIES OF DELTA STATE, NIGERIA

Abstract

Pollution interactions of ozone, nitrogen dioxide, sulphur dioxide, hydrogen sulphide, ammonia, total suspended particulate matter, respirable and inhalable fractions of the particulates were studied in some major cities in Delta State, including Warri, Ughelli and Sapele, while Ugbenu village, a remote area was used as control. Concentration of the trace metals in total suspended particulate matter, inhalable and respirable fractions in the study areas were also analyzed. These were done with the aim of assessing the levels and possible health implications of the measured airborne pollutants on lives within and around the study areas. Hand-held environmental sensors; Environmental Sensor, Z700 – Z1300) were used to monitor NO2, SO2, ozone, ammonia and hydrogen sulphide, while Casella MicroDust Pro Aerosol Monitoring System was used to measure total suspended particulate matter. Different pore sizes polyurethane foam filter (PUF) fitted into a gravimetric adapter in the Casella was used to provide size-selective sampling for PM10 and PM2.5 fractions of the airborne suspended particulate matter. Glass fibre filters and polyurethane foam filters (PUF) were used to collect the dust particles which were extracted for trace metals analysis. Twenty nine (29) elements including Li, Be, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Mo, Cd, Sn, Sb, Te, Cs, Ba, La, W, Pt, Hg, Tl, Pb, Bi and U were analysed using Inductively Coupled Plasma Mass Spectroscopy (ICP- MS). Meteorological parameters were measured accordingly during sampling. The results showed that averagely, NO2 concentrations (0.12 ± 0.04 ppm) exceeded the regulatory limits of National Ambient Air Quality Standard (NAAQS) of 0.05 ppm and Federal Ministry of Environment (FMEnv) standard of 0.04 ppm – 0.06 ppm, while SO2 (0.023 ± 0.01 ppm), H2S (0.073 ± 0.01 ppm) in all the locations fall within the threshold limits of NAAQS and FMEnv. Ammonia (NH3) concentrations ranged from (0.002 ppm – 0.074 ppm) within the limit 25 ppm set by Occupational Safety and Health Administration (OSHA). The mean concentration of ground level ozone (O3) (0.136 ± 0.05 ppm) in dry season exceeded the regulatory limits of NAAQS, while the mean concentration in wet season (0.059 ± 0.02 ppm) fell within the regulatory limit. Concentrations of these pollutant gases measured at the control station were below their detection limits. Higher concentrations of the pollutant gases were measured in dry season than the wet season. The mean concentration of TSP measured in the dry season for all the sampling sites was 5.97 ± 0.28 mg/m3 while wet season recorded 4.09 ± 0.23 mg/m3, far higher than the regulatory limit of FMEnv (0.25 mg/m3).The mean concentration of inhalable particulate matter (PM10) measured in dry season was 2.52 ± 0.09 mg/m3 while the wet season recorded 1.74 ± 0.20 mg/m3 exceeding the regulatory limits of United state NAAQS (0.150 mg/m3) for PM10. The mean concentration of respirable particulate matter (PM2.5) measured in dry season for all the sampling sites was 2.69 mg/m3 while the wet season recorded 1.65 mg/m3, exceeding the regulatory limit of NAAQS (0.035 mg/m3) for PM2.5, hence, posing great threats to health of the inhabitants within the study areas. The results obtained from elemental characterization of the pollutants revealed that among the twenty-nine metals studied, Hg (26 ± 1.00 ppb), Ni (96.23 ±0.02 ppb), Cu (466 ±1.00 ppb), Cr (83.60 ± 0.10 ppb), Mn (429 ± 1.00 ppb), Ti (464 ± 1.00 ppb), Zn (5379 ± 0.00 ppb), Se (30.85 ± 0.01 ppb), Ba (2952.5 ± 1.50 ppb) and U (6.56 ± 0.01 ppb) were of great threat while Be (0.63 ± 0.01 ppb), V (41.60 ± 0.01 ppb) and Sr (278 ± 1.00 ppb) were less likely to cause damage. The levels of these gaseous and particulate matter pollutants as measured in the study areas are attributable to fuel combustion from motor vehicles, power generation and industrial facilities among others.