RESUMO
This paper presents a study on ground-level ozone (O3), nitrogen oxides (NOx = NO + NO2) concentrations, and their variabilities in the ambient air of three sites of a tropical archipelago that is moderately urbanized. Statistical analysis was performed on a quite complete (>80%) set of 5 years of measurements (2008-2012). There are few studies on those pollutants and their seasonal behavior in the Caribbean area, where pollution level and cities configuration are different from megacities. Analyses are focused on pollutant variations at the scale of the day, the week, and the seasons, using hourly data. The observations show that NOx concentrations are more elevated during the wet season, whereas O3 concentrations are higher in the dry season. Amplitudes of ozone cycles are strongly influenced by meteorological conditions (temperature, global radiation, and wind speed) and prevailing levels of NOx. An ozone weekend effect is detected with the highest amplitude in the city, where anthropogenic activity is the lowest during the weekend. Due to the nature and the origin of pollutants, NOx shows higher variability than O3 in the time series. Our results evince the need for continuous measurements of volatile organic compounds (VOCs) in order to better quantify their contribution in O3 formation in an insular context where numerous natural sources have been identified. Implications: Statistical analyses of observed NOx and O3 concentrations for 5 years for a typical low industrialized site of the Caribbean area have been done. Air quality for those components is correct based on the standards of the World Health Orgaization, pollutant source spatial distributions, and level of industrialization. Observations show the same patterns as in megacities but also a strong impact of weather conditions and road traffic. Behaviors of O3 cannot be fully explained without VOCs monitoring. Localization and type of AQS should be reconsidered to improve the accuracy of concentrations of the pollutant and better understand their behaviors.
Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/análise , Monitoramento Ambiental/métodos , Óxidos de Nitrogênio/análise , Ozônio/análise , Guadalupe , Estações do Ano , Tempo (Meteorologia)RESUMO
This study outlines an experimental method for landfill volatile organic compounds (VOCs) characterization by means of a portable time-of-flight mass spectrometer in an insular tropical environment. The concentrations of six VOCs, three aromatic and three chlorinated compounds, frequently identified in landfill gas plume were determined in the main municipal solid waste of Guadeloupe archipelago and its surrounding areas (in the Leeward Islands). Measurements were carried out for various stages of waste degradation. Without mechanical forcing on the waste piles, the results for aromatic and chlorinated compounds showed much higher concentrations at covered waste. Benzene, toluene and ethylbenzene were easily detected by the portable mass spectrometer in the air matrix with concentrations significantly greater than the equipment limit of detection (LOD) estimates. Trichloroethylene is not often measured by the mass spectrometer and very few calculated concentrations reach the instrument LOD. For sites near the landfill, using the sum trichloroethylene + tetrachlororethylene as tracer, it was observed that the most affected locations are under the wind of the landfill plume. Moreover, under certain atmospheric conditions, most of the surrounding area, downwind and upwind, can undergo an increase of the tracer concentration levels, as shown in the paper during a dust outbreak.