Larry G. Anderson

Sources and sinks of formaldehyde and acetaldehyde : An analysis of Denver's ambient concentration data

Four-hour average concentration data for formaldehyde and acetaldehyde have been collected in downtown Denver for each winter since December 1987, and on a year-round basis since October 1991. Carbon monoxide measurements have also been made at the same site since October 1991. These data have been analyzed in an attempt to identify the important sources and sinks for these carbonyl compounds in downtown Denver. We have found that motor vehicle emissions are a major source of these compounds all year. Although we do not find evidence for significant net photochemical production, we do find evidence for photochemical sources and sinks of both compounds. We have applied statistical techniques to ambient concentration data that can extract useful information about these atmospheric sources, sinks and processes, in spite of the large day-to-day variability in the data. Formaldehyde concentrations were found to have increased significantly during three recent winters when at least 2.6% oxygen-content fuel was required compared to two earlier winters when at least 2.0% oxygen-content fuel was required. The increase in formaldehyde concentration coincides with the increase in oxygenate content required in the fuel, but may be due to other causes.

Ethanol fuel use in Brazil: air quality impacts

Brazil has a long history in the development of ethanol for use as a liquid fuel for vehicles. They have developed one of most efficient and economical systems for producing ethanol in the world. Brazil provides an example that many other countries would like to emulate. Using ethanol as a vehicle fuel has significant potential air quality impacts. This paper will review the available air quality and vehicle emissions data in Brazil, specifically focusing on vehicle related pollutants that may be impacted by the use of large quantities of ethanol in the fuel. The atmospheric concentrations of acetaldehyde (CH3CHO) and ethanol in Brazil are much higher than those in other areas of the world, while the concentrations of the single ring aromatic compounds and small carboxylic acids are more typical of observations elsewhere. Acetaldehyde and ethanol increase in vehicle emissions and nitrogen oxides (NOx) may increase when ethanol fuels are used. Both CH3CHO and NOx are very important contributors to photochemical air pollution and ozone (O3) formation. There are very significant O3 air quality problems in Brazil, most studied in the larger cities of Sao Paulo and Rio de Janeiro. These are issues that must be evaluated for other areas of the world that are considering the use of high ethanol content vehicle fuels.

Investigation of the Photocatalytic Oxidation of Low-Level Carbonyl Compounds

Though the bulk of research involving photocatalytic oxidation (PCO) of volatile organic compounds (VOCs) has involved the remediation of pollutants at high inlet concentrations, there has been some implication that PCO can be used to reduce exposure to low concentrations of VOCs and improve the quality of indoor air. The high conversion rates previously reported for PCO of VOCs in the parts-per-million (ppm) range may not, however, be applicable to concentrations in the parts-per-billion (ppb) range that are more typical of indoor air quality (IAQ) issues. This paper reports on an examination of the operational characteristics of four PCO reactor designs used for the oxidation of VOCs in the ppb concentration range. Reactor efficiency is examined for three low molecular weight carbonyl compounds commonly associated with IAQ issues: formaldehyde, acetaldehyde, and acetone. The measured response is the destruction of carbonyl reac-tants. Variables include flow stream velocity and reactor residence time. Oxidation of carbonyl compounds is also examined as a function of ultraviolet (UV) radiation intensity. PCO of the formaldehyde and acetone was nearly 100% for all reactor designs. To assist comparison of the reactor designs, oxidation efficiency of trichloroethylene (TCE) was evaluated at inlet concentration in the parts-per-million by volume (ppmv) range.

Nitric acid, particulate nitrate and ammonium profiles at the bayerischer wald: evidence for large deposition rates of total nitrate

Abstract Chemical measurements at five levels within and above a predominantly spruce forest at the Bayerischer Wald (Bavarian forest) National Park, Germany, site show that particulate nitrate, as well as nitric acid, is rapidly removed to the forest canopy. The rate of dry removal to the forest canopy for particulate nitrate was nearly as large as that for nitric acid. Cascade impactor data indicate a major reason for the large particulate nitrate deposition rates may have been its 2–2.5 μm mean diameter. Dry removal of total nitrate may be sufficient to cause nitrogen saturation at this forest site. In combination with nitrogen wet deposition, the nitrogen available for biotic demand appears to be in sufficient supply to cause ammonia emission from this spruce forest canopy. At some other European forest sites, where ambient air nitrate concentrations are higher, the dry plus wet removal of total nitrate may be sufficient to cause nitrogen availability to be substantially greater than its biotic demand.