Considerable researches have documented the negative effects of ozone on woody species in North America and Europe; however, little is known about how woody tree species respond to elevated O3 in subtropical China, and most of the previous studies were conducted using pot experiment. In the present study, Machilus ichangensis Rehd. et Wils (M. ichangensis) and Taxus chinensis (Pilger) Rehd. (T. chinensis), evergreen tree species in subtropical China, were exposed to non-filtered air (NF), 100 nmol mol?1 O3 (E1) and 150 nmol mol?1 O3 (E2), in open-top chambers under field conditions from 21st March to 2nd November 2015. In this study, O3 fumigation significantly reduced net photosynthesis rate (Pn) in M. ichangensis in the three measurements and in T. chinensis in the last measurement. Also, non-stomatal factors should be primarily responsible for the decreased Pn. O3 fumigation-induced increase in malondialdehyde, superoxide dismutase, and reduced ascorbic acid levels indicated that antioxidant defense mechanism had been stimulated to prevent O3 stress and repair the oxidative damage. Yet, the increase of antioxidant ability was not enough to counteract the harm of O3 fumigation. Because of the decrease in CO2 assimilation, the growth of the two tree species was restrained ultimately. The sensitivity of the two tree species to O3 can be determined: M. ichangensis > T. chinensis. It suggests a close link between the rising O3 concentrations and the health risk of some tree species in subtropics in the near future. 相似文献
A series of Co-La catalysts were prepared using the wet impregnation method and the synthesis of catalysts were modified by controlling pH with the addition of ammonium hydroxide or oxalic solution. All the catalysts were systematically investigated for NO oxidation and SO2 resistance in a fixed bed reactor and were characterized by Brunanuer–Emmett–Teller (BET) method, Fourier Transform infrared spectroscopy (FTIR), X–ray diffraction (XRD), Thermogravimetric (TG) and Ion Chromatography (IC). Among the catalysts, the one synthesized at pH = 1 exhibited the maximum NO conversion of 43% at 180°C. The activity of the catalyst was significantly suppressed by the existence of SO2 (300 ppm) at 220°C. Deactivation may have been associated with the generation of cobalt sulfate, and the SO2 adsorption quantity of the catalyst might also have effected sulfur resistance. In the case of the compact selective catalytic reduction (SCR), the activity increased from 74% to 91% at the highest gas hourly space velocity (GHSV) of 300000 h–1 when the NO catalyst maintained the highest activity, in excess of 50% more than that of the standard SCR.
