Gasoline Vehicle Emissions at High Altitude: An Exploratory STATIS Study in Guaranda, Ecuador

Vehicle emissions pose significant environmental challenges, particularly in high-altitude regions, where atmospheric conditions amplify pollutant concentrations. This study evaluates CO2 and hydrocarbon (HC) emissions from 79 gasoline-powered vehicles in Guaranda, Ecuador (2668 m.a.s.l.), by using STATIS, a multivariate statistical method. The vehicles were classified into six model year intervals and tested under idle and dynamic conditions, measuring idle CO2 and HC (ICD and IHC) and dynamic CO2 and HC (DCD and DHC). The results showed that vehicles manufactured before 2000 exhibited the highest emissions, with ICD of 3.18% vol. and IHC of 414 ppm, while vehicles produced after 2020 showed significantly lower values (ICD of 0.27% vol. and IHC of 101.44 ppm). Additionally, Chevrolet was the most represented brand, accounting for 41.78% of the analyzed sample, while 34.18% of the vehicles were from the 2010-2015 interval. The STATIS model revealed structural similarities among the 2000-2005, 2016-2019, and post-2020 models, whereas pre-2000 vehicles differed markedly from the 2010-2015 models. Outliers, including older vehicles with low emissions and newer models with unexpectedly high emissions, highlighted the role of maintenance and operational conditions. These findings demonstrate the effectiveness of STATIS in analyzing complex emission patterns and underscore the need for future studies that incorporate variables such as mileage and environmental factors to refine emission mitigation strategies.