Effects of Experimental Hydrogen Sulphide Deposition on Dominant Plants Around Geothermal Power Plants in Kenya and Iceland

Abstract

Previous studies show that plants close to geothermal power plants can accumulate sulphur from emitted H2S gas, but the responses in terms of growth and physiology are not well described. We carried out two separate controlled experiments on dominant plants around geothermal power plants in Kenya and Iceland, i.e. the shrub Tarchonathus camphoratus (using seedlings) and the moss Racomitrium lanuginosum, respectively. We tested the hypothesis that sulphur concentration and accumulation in plant tissues would increase with increasing concentrations of wet hydrogen sulphide deposition, with consequences for plant growth and health. We irrigated the plants with 0, 30, 100 and 300 µg /L hydrogen sulphide gas dissolved in distilled water, for 6.5 (shrub) and 13 (moss) weeks, and measured plant responses in terms of sulphur concentrations (and calculated accumulation), foliar damage, growth, chlorophyll concentrations and contents (total amount). Due to lack of roots and their sensitivity to atmospheric depositions, we expected mosses to respond more strongly than the shrub. The treatments did not affect sulphur concentrations and accumulation in shrub leaves, nor did they affect foliar damage or chlorophyll concentrations and content of seedlings. However, stem height increase was greatest at intermediate H2S exposure. The treatments had no effect on sulphur concentration and accumulation, biomass increase or chlorophyll concentrations/contents of moss shoots, but shoot length was reduced at high H2S concentration exposures. We thus conclude that short-term exposure to moderate levels of H2S (watering with 30 µg/L H2S solution) is not harmful to either of the two plants and may even stimulate shrub growth while high levels may reduce moss growth.