Phytotoxicity in Bush Bean of Five Sulfur-Containing Gases Released from Advanced Fossil Energy Technologies1
- G. E. Taylor and
- W. J. Selvidge2
Sulfur-containing gases including sulfur dioxide (SO2), hydrogen sulfide (H2S), carbon disulfide (CS2), carbonyl sulfide (COS), and methyl mercaptan (CH3SH) are a major class of atmospheric emissions from advanced fossil energy technologies. Although phytotoxicity data for SO2 and H2S exist, the influence on vegetation of the remaining S gases is not known. This study was designed to address the comparative toxicity of the five gases in bush bean (Phaseolus vulgaris). Seedlings were exposed to each gas individually for 6 hr at a range of concentrations (6–82 µmol m−3) in an open gaseous exchange system, during which whole-plant net photosynthesis and transpiration were monitored. At the highest exposure levels, leaf necrosis was assessed 3 d after exposure. Transpiration did not respond consistently to any of the treatments. Neither CS2 nor CH3SH caused any change in photosynthesis or foliar necrosis. Based on the inhibition of photosynthesis and the development of leaf necrosis at equivalent volumetric concentrations in the atmosphere, the toxicity of the remaining three gases was SO2 > H2S > COS. The relationship between net photosynthesis and exposure dosage (concentration × time) for H2S, SO2, and COS was curvilinear and biphasic, exhibiting in each gas an enhancement of photosynthesis followed by inhibition as the dosage increased. For projected emission rates from advanced fossil energy facilities, the results suggest that releases of CH3SH and CS2 are not likely to influence vegetation. Since plant response to H2S, SO2, and COS is strongly dosage dependent, accurate estimates of field effects due to these three gases must await more adequate air quality modeling near commercial-scale facilities.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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