ABSTRACT The screening of certain chemical markers associated with the burning of fuels (gasoline, diesel, firewood, pellets, and kerosene) is carried out. The studied markers correspond to phenolic compounds present in emitted gases. Identification and quantification were performed by solid phase extraction followed by high-performance liquid chromatography with diode-array detection (HPLC-DAD). The volatile phenolic derivatives detected and quantified in these experiments were phenol (Ph), 2-nitrophenol (2-NPh), 4-nitrophenol (4-NPh), o-hydroxyphenol (2-HPh), 2-methoxyphenol (2-MetPh), 4-methoxyphenol(4-MetPh) and 2,4-dinitrophenol. The emissions from firewood- and pellet-burning heaters contain mainly o-hydroxyphenol, 4-methoxyphenol, and Ph. In the emissions from gasoline-powered vehicles, only Ph was detected, and in those of diesel-powered vehicles, only 2-NPh and 4-NPh were detected. Kerosene-burning heaters did not exhibit measurable amounts of phenolic compounds in their emissions. The controlled irradiation of the emissions from the burning of firewood and pellets using a photochemical camera showed high degrees of stability of these compounds. The studied phenolic derivatives did not photolyse or were not formed by the photochemical pathway; therefore, their origin is clearly primary, which allows their use as combustion tracers in a particular atmosphere. The presence of Ph derivatives in the Santiago atmosphere indicates the existence of mobile sources (daytime) and the use of firewood (night-time). The presence of 2-NPh and 4-NPh derivatives in the air would be strongly associated with the use of mobile sources that use diesel. In contrast, catechol is associated with the burning of wood for heating.

ABSTRACT The total elemental composition and the water-soluble fraction of PM10 from three different urban areas in Santiago, Chile, from downtown to the suburbs, were investigated. PM10 samples collected during the month of May (mid-autumn in the Southern Hemisphere) in 2006, 2008, 2009, and 2010 were analyzed for major and trace metals, and the partitioning between the insoluble and soluble fractions was determined for most of them. PM10 average concentrations ranged from 71 µg m-3 (Cerrillos) to 128 µg m-3 (La Pintana), which are within the seasonal ranges observed in Santiago. Twenty five major and trace elements (Fe, Al, Ca, K, Mg, P, Pb, S, Ti, Mn, Cu, Zn, Ba, Zr, Cr, As, Sn, Sb, Ni, V, Li, Co, Cd, La, and Rb) were determined in the present study. Ba, Sb, Cd, As, and Zn, with proportions in the soluble fraction varying from 50% to 98%, were the most soluble elements. On the contrary, the less soluble trace elements were Ti, Sn, Pb, and Cr. Most of the high-solubility trace metals are strongly linked to non-exhaust traffic emissions, as well as to certain industrial sources. Our results evidence the significant amount of soluble trace elements in Santiago’s urban atmosphere classified as toxic and/or carcinogenic, thus suggesting a non-negligible health impact.

RESUMEN Se investigó la composición elemental total y la fracción soluble en agua de PM10 en tres áreas urbanas diferentes de Santiago de Chile, del centro a los suburbios. Las muestras de PM10 recogidas durante el mes de mayo (mediados del otoño en el hemisferio sur) en 2006, 2008, 2009 y 2010 fueron analizadas para metales mayores y trazas, y la partición entre fracciones insolubles y solubles se determinó para la mayoría de ellos. Las concentraciones medias de PM10 variaron de 71 µg m-3 (Cerrillos) a 128 µg m-3 (La Pintana), valores que se encuentran dentro de los rangos estacionales observados en Santiago. Se cuantificaron 25 elementos principales y trazas (Fe, Al, Ca, K, Mg, P, Pb, S, Ti, Mn, Cu, Zn, Ba, Zr, Cr, As, Sn, Sb, Ni, V, Li Co, Cd, La y Rb) en el presente estudio. Ba, Sb, Cd, As y Zn fueron los elementos más solubles, con proporciones que varían de 50% a 98% de solubilidad. Por el contrario, los oligoelementos menos solubles fueron Ti, Sn, Pb y Cr. La mayor parte de los metales traza de alta solubilidad no están solamente fuertemente ligados a la emisión de tubos de escape vehiculares, sino a emisiones vehiculares como el sistema de frenos o a ciertas fuentes industriales. Nuestros resultados evidencian la cantidad significativa de oligoelementos solubles en la atmósfera urbana de Santiago clasificados como tóxicos y/o carcinógenos, lo que sugiere un impacto no despreciable en la salud.

Composites based on nanosized particles of magnetite and natural microsized zeolite were prepared and their efficiency to adsorb arsenate from aqueous systems was evaluated through kinetic data and adsorption isotherms, considering the proportion of magnetic iron oxide, composite:solution ratio and zeolite particle size. A well-crystallized nanomagnetite with an averaged particle size of 50 nm when supported on zeolite was obtained; the nanomagnetite enhances the arsenate adsorption of zeolite. The composite prepared with a nanomagnetite:zeolite mass ratio of 0.43:1 and 0.30:1 presented on zeolite milled 20 and 120 min, respectively, showed a similar adsorption capacity as that observed for pure magnetite. Supported nanomagnetite prevents risks of the nanoparticles contamination. The smaller the mean particle size of zeolite the lower the mass proportion of nanomagnetite in the composite required to reach the maximum adsorptive efficiency. Acidic conditions improve arsenate remotion, in agreement with the development of positive surface charge in the composite.

Ozone concentrations in the urban air of Santiago de Chile frequently surpass the air quality standard in summertime, particularly in the eastern part of the city (Las Condes). The main parameter that determines ozone episodes is the ground level daily maximum temperature. In the present work we propose that this single parameter can be employed as a simple predictor of the expected ozone levels. In particular, it is found that high ozone episodes takes place in Las Condes when the maximum daily temperature is higher than 30 °C. This single criterion applies during all the summer period (from December to March) and for weekdays and weekends. On the other hand, ozone episodes in downtown take place only when the maximum daily temperature reaches values higher than 32.5 °C. These simple relationships imply that weather forecast could be employed by the citizens to estimate the risk associated to carry out outdoors activities.

Samples of sediment from Estero Rungue, north of Santiago, were analyzed during January 2007. The studied zone is affected by acid contamination. Analysis of the sediment by XRD detected the presence of rozenite (FeSO4-4H2O) and gypsum (CaSO4-2H2O). The experiments were carried out according to the criterion estabhshed for the first Step of the sequential extraction proposed by the SMT, using Ca, Cu, Fe, Ni and Zn sulfates in the form of MxSO4áH2O as a model sediment. The results suggest that it is possible to extract up to -99% of the sulfates because of the low pH (~3). Analysis of the sediment by XRD before and after the first Step of the sequential extraction showed that the sulfates disappear after the treatment, extending the interpretation of the first Step of the sequential extraction to elements that are interchangeable, adsorbed on carbonates, and present as sulfates.