Evaluating the optimal configuration of the air quality monitoring network for two combined-cycle natural gas (CCNG) Plants of similar characteristics

A study was conducted to assess the impact of two neighbouring combined cycle natural gas (CCNG) units of similar characteristics on the surrounding area. The pollutants ozone, nitrogen dioxide, PM10 particles and sulphur dioxide were evaluated. The main goal of the study was to assess the optimal configuration for the units' existing air quality monitoring network (AQMN). The current network comprises a total of six stations measuring ozone, NO/NO2, PM10/PM25 particles, CO and SO2 with one of them also housing a meteorological station measuring wind speed and direction, solar radiation, temperature, relative humidity and atmospheric pressure. The network was originally designed to monitor the impact of the emissions from fuel-oil power plants, that were operating in the site but were dismantled a few years ago, plus the modelled maximum impact from the two CCNG units that were at the time in construction. The study shows that the emissions from the two CCNG units impacts mostly the closest areas to the plants and is very limited, especially for sulphur dioxide and particles due to the negligible emissions of those pollutants from the units. For ozone and NO2 the impact is also moderate when compared to the air quality limit values for those pollutants. A final optimal configuration comprising a reduced number of stations is proposed based on the results of the study. This study highlights the need to reassess the AQMNs for other large stationary sources around the country that have undergone significant retrofits and improvements to comply with air quality regulations and may no longer require the same level of monitoring.