There is no systematic attempt to evaluate the air quality of any settlement in the Niger Delta region over a long period. Records of air quality data for this study were generated through secondary sources from impact assessment of facilities aimed at implementing air quality regulations on the environment. Suspended particulate matter in the region's atmosphere ranged from 40 µg/m 3 in Brass to 98 µg/m 3 in Port Harcourt. Carbon monoxide concentrations were highest in Mbiama (191 µg/m 3). Nitrogen dioxide concentration was highest in Bonny (187 µg/m 3), and sulphur dioxide concentrations ranged from 19 µg/m 3 in Ukwugba to 90 µg/m 3 in Port Harcourt. Total hydrocarbon ranged from 78 µg/m 3 in Odukpani to 192 µg/m 3 in Nchia. Carbon dioxide ranged from 400 ppm in Buguma to 450 ppm in Port Harcourt. The most abundant of the VOCs is benzene and toluene. Ethylene was detected only in one station at concentration of 0.1 µg/m 3 which was negligible. The most abundant of the metals was zinc, which was present at above 2 µg/m 3 in most of the study settlements. In remote settlements like Buguma and Emuoha, some of the metals were not detected at all. In some instances, short-term limits for the pollutants exceeded WHO standards. The need for stakeholders in the region to articulate initiatives that support quality environmental practices was emphasized as laws pertaining to air quality regulations which are weak and less enforceable.

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The Bonny Island axis of the Niger Delta, Nigeria, is one of the most industrialized belts of Nigeria. Among the significant industries in the locality is the Nigerian natural gas liquefying plants. The plant complex generates emissions which are propagated by meteorological agents. An atmospheric dispersion model was used to model the emissions using a computer programme. A statistical analysis of meteorological parameters was also carried out to determine the pollutants dispersion in the atmosphere. The analysis shows that wind speed is moderate and the predominance of southerly winds will move plumes toward human settlements in the north and northeastern directions from the plant. From the diffusion model, the compounds likely to be emitted in the largest quantity from the plant in the order of magnitude were CO 2 , NO x , CO, PM 10 and SO x. There is evidence that pollutants concentration would be highest for receptors at about 10 km from the emission sources even under unstable atmospheric conditions. The concentration of all the pollutants were well within the set ambient limits for the averaging period considered (i.e., 1 hour). It is recommended that the LNG plants continue to use natural gas as their major fuel as it will help in reducing pollutants like CO, PM 10 and SO x. Also, due to the large CO 2 gas emitted, afforestation and conservation projects should be initiated in Bonny Island so as to earn carbon credit.

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The ISCST-3 model has been used to study the ground level concentrations of carbon monoxide (CO), oxides of nitrogen (NO X), particulate matter less than 10.0 microns in diameter (PM 10) and sulphur dioxide (SO 2). The purpose was to predict air quality effects from an integrated oil and gas project (IOGP) proposed for the Niger Delta, Nigeria. The emissions of 12 elevated point sources for criteria air pollutants were considered with eight different scenarios. Both natural gas-fired and diesel (AGO) fired equipment were considered for the identified emission sources. Five years of hourly meteorological observations were used in the prediction of the ground level concentration of the pollutants. The model outputs show a general maximum ground level concentration between 0.5-3.5 km, with easterly and north-easterly receptors having the greatest concentration. The pollutants emitted in the greatest concentration in their order of magnitude were CO, NO x and PM 10. Maximum ground level concentration for 1, 8 and 24-hr periods for CO were below regulatory standards (less than 10 %) for scenarios 1-4 when the fuel is natural gas. The 8-hr ground level concentrations were about 1.3 folds of the World Bank Standard in scenarios 5-8 when the fuel sources are switched to AGO. However in these scenarios, the Nigerian environment and petroleum ministries' emission limits were not breached for all the averaging periods. Modelled NO X concentrations were significant in all the scenarios except 3 and 4. Though NO X concentrations were within the standards for all the averaging periods in scenarios 1-4, except the 1-hr limit that was breached in scenarios 1 and 2, these concentrations were about 1.1-2.8 folds in all the averaging periods of all the standards in scenarios 5-8. The predicted PM 10 and SO 2 concentrations are all below the guideline limits. If the use of AGO is completely avoided in the entire life of the proposed IOGP, the air quality of its immediate vicinity can be protected. Furthermore, the declaration of a radius 1.75 km natural forest buffer around the plant and continuous monitoring of ground level concentrations of CO, NO X , PM 10 , and SO 2 may further assist in guaranteeing the safety of people in terms of air quality. The study shows the need for policy formulation that will integrate comprehensive cumulative impacts assessment of air quality in the environmental laws regulating the gas development projects in Nigeria. 331

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