Eugenio Sanhueza

Hydroxyl radical rate constants and photolysis rates of .alpha.-dicarbonyls

38, 811. (37) Matthess, G.; Pekdeger, A. GWF, GasWasserfach: WasserlAbwasser 1980, 121, 214. (38) Davis, J. In “Contaminants and Sediments”: Baker, R. A,, Ed.; Ann Arbor Science: Ann Arbor, MI 1980; p 279. (39) Hansch, C.; Leo, A. In “Substituent Constants for Correlation Analysis in Chemistry and Biology”; Elsevier: Amsterdam, 1979. (40) Tute, M. S. Adv. Drug. Res. 1971, 6 , 1. (41) Mackay, D.; Bobra, A,; Shin, W. Y.; Yalkowsky, S. H.

Field measurement evidence for an atmospheric chemical source of formic and acetic acids in the tropic

The simultaneous measurements of atmospheric HCOOH, CH3COOH H2O2, organic peroxides, HCHO, CH3CHO and isoprene made in the Venezuelan savannah region, in the wet season (September, 1993) and during the period of high solar irradiation is reported. The average concentrations (in ppbv) between 10:00 and 16:00 were: HCOOH 0.75±0.32, CH3COOH 0.56±0.28, H2O2 1.37±0.48, the total peroxides 1.83±0.60, HCHO 1.38± .43, CH3CHO 0.35±0.15, and isoprene 2.18±0.78. A good correlation was observed between the concentrations (15 min averages) of both acids. The acids also correlate with isoprene (the most abundant olefin in the savannah atmosphere), H2O2 and the total peroxides. HCOOH also correlates well with HCHO and CH3CHO. These results support the hypothesis that significant amount of formic and acetic acids are produced in the tropical atmosphere as a result of the oxidation of reactive hydrocarbons.

Positive interference of nitrous acid in the determination of gaseous HNO3 by the NOx chemiluminescence-nylon cartridge method: Applications to measurements of ppb levels of HONO in air

Abstract Gaseous nitrous acid in air has been simultaneously monitored in environmental chambers by an absolute method, differential optical absorption spectroscopy, and by a nylon cartridge-chemiluminescence NO x technique originally developed by Spicer and co-workers for gaseous HNO 3 . In the absence of HNO 3 , the latter technique proved to be a simple and accurate method for measuring ppb levels of HONO in air. However, the positive interference by HONO in the nylon cartridge-chemiluminescence technique may have important ramifications due to possible artifacts in measurements of gaseous HNO 3 by removal on nylon surfaces. Thus, previous observations in night-time atmospheres or environmental chambers attributed entirely to gaseous HNO 3 may have been, at least in part, due to the presence of gaseous HONO.

Elemental analysis of the total suspended matter in the air in downtown Caracas

Abstract The concentrations of 11 elements in suspended particulates samples in downtown Caracas were measured. The samples were analyzed by neutron activation or X-ray fluorescence techniques. The annual geometric means found for the period March 1977–March 1978 were (μg m −3 ) 1.47 (Na), 1.14 (Al), 3.76 (Cl), 0.0076 (V), 1.66 (Fe), 0.69 (Zn), 0.62 (Br), E.F. ) obtained with respect to the earths crust show Caracas air to be heavily polluted with compounds containing Cl, Br, Zn or Pb. Possible sources for the observed atmospheric levels are discussed.

Airborne particles in the Venezuelan savannah during burning and non-burning periods

Abstract Atmospheric concentrations and size distribution of suspended particles at 1.5 or 3.9 m height were determined at five Venezuelan savannah sites. The results show a bimodal distribution in both the vegetation burning and non-burning periods, with significantly higher concentration of particles of all sizes during the burning period. During vegetation fires the concentration of fine particles ( 1.5 μm), producing an MMD that ranges from 0.60 to 0.95 μm. The MMD in the non-burning period range from 1.3 to 3.3 μm. Possible sources of particles of various sizes in both periods are discussed.

Incidence of secondary components in the suspended particles of the caracas air

Abstract Atmospheric suspended particles from downtown Caracas were analyzed for their sulfate, nitrate, halide and benzene soluble organic particles content. From the auto emission pattern, the enrichment factors with respect to the soil dust and the concentrations relative to a near-urban, relatively nonpolluted atmosphere, it is concluded that sulfates and nitrates are produced photochemically as secondary pollutants in the downtown Caracas atmosphere. The accumulation of the secondary particles shows that the dispersion of pollutants in the Caracas Valley is not as efficient as normally thought for its geographical location. The lack of ozone reported previously cannot be explained by dispersion mechanisms.

Forest Fires: An Important Source of Benzo(a)Pyrene in the Caracas Valley

The levels of benzo(a)pyrene (BaP) were determined in downtown Caracas in order to have a first approach to the problem related to polycyclic aromatic hydrocarbons in this city. Caracas, the capital city of Venezuela is located 10.30° N and 66.77°E in a valley at an altitude of 996 m above sea level with an average temperature ranging from 18° to 23°C, and two distinctive climatic regimes, a dry and a wet season. The population is approximately 2.5 million with a car density of approximately 1000 vehicles/km2 and no industry. The valley is surrounded by mountains, the Avila National Park at the northern edge of the city with peaks of around 2200 m being the most important contribution to the green belt that has been preserved. As far as we know no other studies to determine the levels of BaP have been made in a populated urban area located near the equator.