developed countries. Australia's Commonwealth Science Council has suggested that 9 of 10 deaths due to indoor air are experienced by the developing world ( Brennan and Withgott, 2005 ). Ozone (O 3 ), a photochemical oxidant with a redox potential of +2.07 V
Heather L. Papinchak, E. Jay Holcomb, Teodora Orendovici Best, and Dennis R. Decoteau
Thomas Graham, Ping Zhang, Youbin Zheng, and Michael A. Dixon
benign fashion are an important component of future greenhouse and nursery management strategies. Aqueous ozone [O 3(aq) ] technology can eliminate pathogens and many chemical contaminants in a wide range of water and wastewater streams without leaving
W.A. Retzlaff, L.E. Williams, and T.M. DeJong
Abbreviations: A, ambient; C, charcoal-filtered; N, nonchamber; Pn, net CO 2 assimilation rate; T, ambient + ozone. This study was funded in part by a grant from the California State Air Resources Board. The statements and conclusions of this
Alyssa J. DeVincentis, Robin G. Brumfield, Paul Gottlieb, and James R. Johnson
, chlorine gas, ozone, and copper require strategic implementation to work effectively. For example, although copper is an essential element for plant growth, an excessive amount is toxic and requires careful monitoring ( Zheng et al., 2004 ). The costs and
Thomas Graham and Michael A. Dixon
segment of the pot. The cost of hand removal and the impacts that the practice has on substrate structure and root vigor necessitates continued effort to develop alternative control strategies. Dissolving highly reactive ozone (O 3 ) gas in irrigation
Doug Findley, Gary J. Keever, Arthur H. Chappelka, Charles H. Gilliam, and D. Joseph Eakes
Five cultivars of buddleia, Buddleia davidii, were exposed to subambient, ambient, and twice-ambient levels of ozone in open-top chambers for 8 weeks during 1995. Plants were evaluated for foliar injury, growth index, and inflorescence characteristics during and following the exposure period. Destructive harvests were conducted at the end of the exposure period to determine the dry weight of both above- and below-ground plant components. All cultivars showed signs of visible injury in the twice-ambient treatment at both 3 and 8 weeks after treatment initiation (WAT). At 3 WAT, `Pink Delight' was the most severely injured, followed by `Opera'. The other three cultivars had similar lower levels of foliar injury. Reductions in growth index as well as dry weight were found for all cultivars in the twice-ambient treatment. The number of developing floral buds and inflorescences was reduced in the twice-ambient treatment for all cultivars. Differences among the cultivars was due to normal differences in growth habit and not due to elevated ozone levels. These data indicate that Buddleia cultivars are sensitive to levels of ozone similar to those found in urban areas of the southeastern United States.
D.A Grantz, W.A. Retzlaff, L.E. Williams, and T.M. DeJong
Models indicate that ozone inhibits carbon assimilation largely in the upper canopy, due to light and ozone gradients. We document yield reductions and ozone gradients in Casselman plum in open-top ozone fumigation chambers. Ambient air (12 hr mean ozone = 0.050 ppm), charcoal filtered air (0.034 ppm) and ambient air plus added ozone (0.094 ppm) were circulated in the chambers. Additional trees grew outside the chambers (0.058 ppm). Outside the chambers large vertical and horizontal gradients in ozone within the canopy were documented, but these were absent in the chambers. Ozone decreased leaf photosynthesis by 31% and 58%, and fruit yield by 20% and 66%, in the ambient and ozone enriched relative to filtered chambers. Despite altered gradients, yield and photosynthesis of exposed leaves were similar inside and outside the chambers in ambient air. Compensatory changes in leaf function may be involved.
William A. Retzlaff, Ted M. DeJong, and Larry E. Williams
Uniform nursery stock of five almond cultivars (Prunus dulcis Mill., cv Nonpareil, Mission, Carmel, Butte, and Sonora) propagated on peach (P. domestica L. Batsch.) rootstock were planted in open-top fumigation chambers on 19 April 1989 at the University of California's Kearney Ag Center located in the San Joaquin Valley of California. The trees were exposed to three atmospheric ozone partial pressures (charcoal filtered air, ambient air, or ambient air+ozone) from 1 June to 2 November 1989. The mean 12-h (0800-2000 h) ozone partial pressure measured in the open-top chambers during the experimental period averaged 0.038, 0.060, and 0.112 μPa Pa-1 ozone in the charcoal filtered, ambient, and ambient+ ozone treatments, respectively. Leaf net CO2 assimilation and cross-sectional area growth of Nonpareil trees were reduced by increasing atmospheric ozone partial pressures, but Mission trees were unaffected. Foliage of Nonpareil almond abscised prematurely in the ambient and ambient+ozone treatments. The susceptibility of the Butte, Carmel, and Sonora almond cultivars to ozone was intermediate between the Nonpareil and Mission cultivars.
Kirsten L. Lloyd, Donald D. Davis, Richard P. Marini, and Dennis R. Decoteau
Across the globe, tropospheric ozone harms human and environmental health ( World Health Organization, 2006 ), while also reducing crop yields ( Ashmore, 2005 ). In the United States, the U.S. Environmental Protection Agency (USEPA) regulates O 3
C.H. Crisosto, W.A. Retzlaff, L.E. William, T.M. DeJong, and J.P. Zoffoli
Abbreviations: AA, ambient air: AA + O, ambient air plus ozone; CFA. charcoal-filtered air: LM, light microscopy: SEM, scanning electron microscopy: SSC, soluble solids concentration; TA, titratable acidity. 1 Assistant Professor. 2 Postdoctoral