HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Taylor, G. E. Articles by Selvidge, W. J. Search for Related Content PubMed Articles by Taylor, G. E., Jr. Articles by Selvidge, W. J. Agricola Articles by Taylor, G. E. Articles by Selvidge, W. J.

Atmosphere x Canopy Interactions of Nitric Acid Vapor in Loblolly Pine Grown in Open-Top Chambers

Biological Sciences Center, Desert Res. Inst., P.O. Box 60220, Reno, NV 89506, and Dep. of Environ. and Resour. Sci., Univ. of Nevada-Reno;

J. G. Owens, T. Grizzard and W. J. Selvidge

Environ. Sciences Division, Oak Ridge National Lab., P.O. Box 2008, Oak Ridge, TN 37831.

^* Corresponding author.

ABSTRACT

Many studies that address the impact of tropospheric O₃ on agricultural and forested ecosystems utilize the open-top chamber. During the production of O₃ using electrical discharge generators fed with dry air, there is an inadvertent addition of HNO₃ vapor, a highly reactive trace gas. While several studies have proposed that HNO₃ vapor introduces artifacts, none has measured concentrations of the odd-N₂ trace gas in the chamber or investigated the fate of the N in the context of whole-plant physiology and growth. These questions were investigated using open-top chambers containing seedlings of loblolly pine (Pinus taeda L.) during the 1988 growing season in Oak Ridge, TN. The O₃ treatments consisted of charcoal-filtered or subambient (0.96 µmol m^–3, 24-h mean), ambient (1.62 µmol m^–3, 24-h mean), and elevated (2.36 µmol m^–3, 24-h mean) concentrations, the last being accomplished by proportional O₃ addition over the diurnal period. Measurements of the HNO₃ vapor concentration during dry periods only (no rainfall or ground-level fog) averaged 28.6 nmol m^–3 (subambient), 55.4 nmol m^–3 (ambient air), and 240.0 nmol m^–3 (elevated O₃), an 8.4-fold range. For every 100 mol of O₃ added to the chamber, 28 mol of HNO₃ vapor were inadvertently added; this ratio is several times higher than that previously reported. This result, taken with published estimates of leaf conductance to HNO₃ vapor, indicates a maximum N deposition in the form of HNO₃ vapor ranging from 19.5 pmol N cm^–2 leaf area h^–1 (subambient O₃) to 171.9 pmol N cm^–2 h^–1 (elevated O₃). Given the nutrient content of the seedlings and knowledge of the fate of HNO₃ vapor on the leaf surface and leaf interior, the degree to which N deposition via HNO₃ vapor met the N requirements of the loblolly pine seedlings was estimated. Seedlings in the elevated O₃ treatment had an upper-limit estimate of 3.5% for the needles and 1.8% for the whole plant of N derived from HNO₃ vapor. The concentration of HNO₃ vapor in the chambers, site of HNO₃ vapor deposition, N requirements of the loblolly pine seedlings, and estimated threshold for phytotoxic effects of HNO₃ vapor indicate that the inadvertent production of this odd-N₂ trace gas is important in understanding the atmospheric chemistry within the chambers, but that the level of N loading in this study is unlikely to affect physiology or growth. However, we recommend that studies that employ higher O₃-exposure scenarios recognize the potential for inadvertent N deposition, particularly in trees grown in N-deficient substrate.

This article has been cited by other articles:

				D. K. Biswas, H. Xu, Y. G. Li, M. Z. Liu, Y. H. Chen, J. Z. Sun, and G. M. Jiang Assessing the genetic relatedness of higher ozone sensitivity of modern wheat to its wild and cultivated progenitors/relatives J. Exp. Bot., March 1, 2008; 59(4): 951 - 963. [Abstract] [Full Text] [PDF]