Reduction of atmospheric emissions due to switching from fuel oil to natural gas at a power plant in a critical area in Central Mexico

A case study was conducted to evaluate the SO(2)emission reduction in a power plant in Central Mexico, as a result of the shifting of fuel oil to natural gas. Emissions of criteria pollutants, greenhouse gases, organic and inorganic toxics were estimated based on a 2010 report of hourly fuel oil consumption at the "Francisco Perez Rios" power plant in Tula, Mexico. For SO2, the dispersion of these emissions was assessed with the CALPUFF dispersion model. Emissions reductions of > 99% for SO2, PM and Pb, as well as reductions >50% for organic and inorganic toxics were observed when simulating the use of natural gas. Maximum annual (993 mu g/m(3)) and monthly average SO(2)concentrations were simulated during the cold-dry period (152-1063 mu g/m(3)), and warm-dry period (239-432 mu g/m(3)). Dispersion model results and those from Mexico City's air quality forecasting system showed that SO(2)emissions from the power plant affect the north of Mexico City in the cold-dry period. The evaluation of model estimates with 24 hr SO(2)measured concentrations at Tepeji del Rio suggests that the combination of observations and dispersion models are useful in assessing the reduction of SO(2)emissions due to shifting in fuels. Being SO(2)a major precursor of acid rain, high transported sulfate concentrations are of concern and low pH values have been reported in the south of Mexico City, indicating that secondary SO(2)products emitted in the power plant can be transported to Mexico City under specific atmospheric conditions. Implications: Although the surroundings of a power plant located north of Mexico City receives most of the direct SO(2)impact from fuel oil emissions, the plume is dispersed and advected to the Mexico City metropolitan area, where its secondary products may cause acid rain. The use of cleaner fuels may assure significant SO(2)reductions in the plant emissions and consequent acid rain presence in nearby populated cities and should be compulsory in critical areas to comply with annual emission limits and health standards.