RESEARCH WATCH
AIR HAP variability Additional data are needed on the temporal and spatial variations in hazardous air pollutants (HAPs) in urban areas to improve monitoring and sampling of these compounds. C. W. Spicer and colleagues report on field measurements and procedures to characterize such variability. They measured 50 volatile organic compounds, 8 carbonyl compounds, 16 trace elements, peroxyacetyl nitrate, and particle-bound extractable organics in Columbus, Ohio. Measurements were taken simultaneously at six sites up to 12 km apart. The spatial component represented 20% or less of the overall variability; temporal variability was the major contributor to HAP variability for 19 of 38 frequently detected chemicals. {Atmos. Environ. 1996, 30, 3443-50)
Herbicide TCA sources The detection of trichloroacetic acid (TCA) in rain, surface waters, and conifer needles in European countries has raised questions about TCA's environmental sources. TCA is banned as an herbicide, but it still has many industrial uses. S. R. Muller and colleagues analyzed TCA in environmental samples using GC with electron capture detection and concluded that atmospheric washout and wastewater are the main sources. They estimated that atmospheric conversion of methyl chloroform and perchloroethene to TCA could lead to steady-state rainwater concentrations of 20-70 ng/L. The figure is well below the 300 ng/L mean concentration of TCA in rainwater, suggesting an unknown source of TCA to the atmosphere. (Environ. Toxicol. Chem. 1996, 15, 1470-78)
Indoor VOC sources Indoor exposure to volatile organic compounds (VOCs) has been sug-
A nation's dioxin burden The United Kingdom recently inventoried primary polychlorinated dibenzo-p-dioxin and furan (PCDD/Fs) emissions in the atmosphere. R. Duarte-Davidson and colleagues examined the relationship between primary emissions of PCDD/Fs (such as combustion) and potential secondary emissions (remobilized and recycled). They also studied the balance between atmospheric emissions and deposition and the total U.K. burden of PCDD/Fs. Roughly 1 kg of dioxin toxicity equivalents is emitted annually, mainly from combustion. Nationwide, these emission rates match deposition rates calculated from monitoring studies. Although emissions have declined since the mid-1970s, substantial amounts of dioxins have accumulated in soils. The authors cite uncertainties in determining the sources and fate of dioxins and suggest areas for additional research. (Environ. Sci. Technol., this issue, pp. 1-11)
gested as the cause of health complaints termed "sick building syndrome." But relatively little information is available on typical background VOC levels in commercial buildings. H. C. Shields and colleagues measured VOC levels in 70 offices in three building types. At each location, the sum of all VOCs measured indoors was greater than the outdoor VOC sum. Buildings with higher ventilation rates had lower levels of VOCs. Some VOCs were associated with building materials and paints, but others probably came from building occupants. These included siloxanes, probably from deodorants and antiperspirants, 12C through 16C n-alkanes from body creams and soaps, limonene from soap and shampoo scent, and tetrachloroethylene from drycleaned clothing. {Indoor Air 1996, 6(1), 2-17)
Phenol biofiltration Many industrial and commercial processes emit phenols into the air. M. Zilli and co-workers describe theoretical and experimental studies on removing phenol from a synthetic exhaust gas. Their technique uses two identical laboratory-scale biological filter bed columns filled with a mixture of peat and glass beads. After sterilization, the mixture was inoculated with Pseudomonas putida bacteria. After varying the inlet phenol concentrations and the superfi-
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cial gas flow rates, the authors concluded that phenol removal rates were consistent with a biofilm model. Such a model could be usee in developing full-scale biofiltratior systems, according to the authors. They also identified the deodorization capacity of the biofilter at various gas flow rates. {Biotechnol. Bioeng. 1996, 49, 391-98)
Urban trees and ozone Communities have expressed increased interest in urban tree-plant ing programs to improve air quality reduce air conditioning costs, and enhance aesthetics. These program fail to consider that trees may emit biogenic hydrocarbons that contrib ute to ozone formation. H. Taha used meteorological and air quality models to simulate the effect of increased urban vegetation on ozone concentrations in California's South Coast Air Basin. Simulations included altered chemical reaction rates and decreased temperaturedependent biogenic hydrocarbon emissions associated with lower temperatures and other effects related to increased vegetation. The simulations indicate a net decrease in ozone concentrations, provided the planted tree species emit low amounts (< 2 pg isoprene and < 1 pg monoterpenes per gram dry leaf mass per hour) of hydrocarbons. (Atmos. Environ. 1996, 30, 3423-30)
0013-936X/97/0931-6A$14.00/0 © 1996 American Chemical Society
