Acidic Gases and Nitrate and Sulfate Particles in the Atmosphere in the City of Guadalajara, México

Abstract

Atmospheric concentrations of nitrous acid, nitric acid, nitrate and sulfate particles were obtained in this study from April to June 2008 in the center of the city of Guadalajara, while concentrations of ozone, sulfur dioxide, nitrogen dioxide and meteorological parameters (temperature and relative humidity), were acquired by the Secretaría del Medio Ambiente para el Desarrollo Sustentable del Estado de Jalisco (SEMADES). The results showed that nitric acid (2.7 μg m(-3)) was 2.7 times higher than nitrous acid (1.0 μg m(-3)). The sulfur dioxide (SO(2)) concentration indicated an opposite trend to sulfate (SO(4) (2-)), with the average concentration of SO(2) (6.9 μg m(-3)) higher in almost the entire period of study. The sulfur conversion ratio (Fs, 24.9%) and nitrogen conversion ratio (Fn, 6.2%), were revealed to be similar to that reported in other urban areas during warm seasons. It is also noted that ozone is not the main oxidizer of nitrogen dioxide and sulfur dioxide. This determination was made by taking into account the slightly positively correlation determined for Fn (r(2) = 0.084) and Fs (r(2) = 0.092) with ozone that perhaps suggests there are other oxidizing species such as the radical OH, which are playing an important role in the processes of atmospheric oxidation in this area.

Polycyclic Aromatic Hydrocarbons (PAHs) Associated with PM2.5 in Guadalajara, Mexico: Environmental Levels, Health Risks and Possible Sources

“…In the organic fraction of PM 2.5 , the polycyclic aromatic hydrocarbons (PAHs) are one of the most widely studied groups of organic compounds, since 16 PAHs have been listed as priority pollutants by the U.S. Environmental Protection Agency [8] because they are considered as possible or probable human carcinogens [9,10]. They are also mutagenic and can undergo atmospheric photochemical reaction in the gas phase and on particle surfaces [11,12] and can be photo-chemically transformed into highly toxic compounds such as nitrated (nitro-PAHs) and oxygenated PAHs (oxy-PAHs).…”

“…Deterioration of air quality, mainly in dry seasons, may be a consequence of the rapid industrial growth and high vehicular traffic in this area; it was also suggested that atmospheric conditions might favour photochemical oxidants and the blockage of pollutants [15]. Although there is an atmospheric monitoring network and studies on trace metals and inorganic ions in PM 2.5 [15,16], it is still necessary to undertake organic chemical characterization of breathable particulate matter to identify sources and to provide support to local government in the design of viable strategies with benefits to the population. A recent study found that naphthalene, phenanthrene, anthracene and chrysene likely undergo photochemical transformation to their quinones compounds, which were found in PM 2.5 at three urban locations within the Metropolitan Zone of Guadalajara during the dry and rainy season in 2012 [17].…”