PhD defence by Thecla Munanie Mutia
On Friday the 9th of September Thecla Munanie Mutia will defend her PhD thesis in Environment and Natural Resources from the University of Iceland in the Askja building, room 132 at 13:00.
The thesis is titled:
The impacts of geothermal power plant emissions on terrestrial ecosystems in contrasting bio-climatic zones
Opponents are dr. Filippo Bussotti, Professor at Università degli Studi di Firenze, Dept. of Agri-Food Production and Environmental Sciences, Section of Plant and Soil Sciences, and dr. Bergur Sigfússon, specialist in geothermal research at OR (Reykjavík Energy).
Supervisors are dr. Ingibjörg Svala Jónsdóttir, Professor at the Faculty of Life and Environmental Sciences at the University of Iceland, and dr. Þráinn Friðriksson, geochemist at ÍSOR and energy specialist within ESMAP at the World Bank. The doctoral committee also includes dr. Sigurður H. Magnússon, Plant Ecologist at the Icelandic Institute of Natural History.
The ceremony will be chaired by dr. Snæbjörn Pálsson, Professor and the Vice Head of the Faculty of Life and Environmental Sciences at the University of Iceland.
Everyone is welcome to attend
Abstract
Very little is known about the ecosystem impacts of emissions from geothermal power plants. The emissions, comprising mainly non-condensable gases (NCGs) i.e. carbon dioxide, hydrogen sulphide, methane and trace elements such as arsenic, boron, antimony and mercury, have the potential to deposit and accumulate in ecosystems. At elevated levels, some NCGs can cause ecosystem stress, especially H2S and the trace elements. The aim of this thesis is to assess the effects of these elements on terrestrial ecosystems around two geothermal areas in contrasting biomes i.e. Kenya and Iceland.
Dominant plant species around each geothermal study area, Tarchonanthus camphoratus shrub in Kenya and Racomitrium lanuginosum moss in Iceland, were used as bio-indicators and concentrations of sulphur, arsenic, boron, antimony and mercury were mapped in their tissues and soils at increasing distances from the power plants along the prevailing wind direction in field surveys. Patterns of plant growth and health along the same distances and wind direction gradients were also studied to assess any potential effects related to the power plants. Controlled experiments were thereafter carried out on the same plant species to assess in detail the effects of the most abundant phytotoxic NCGs, i.e. H2S gas, on plant growth and health.
Results of the field surveys and experiments indicated that the main geothermally emitted component, H2S gas, deposits and accumulates in plants and soils. The measured trace element concentrations in plants and soils (from the field surveys): arsenic, boron, antimony and mercury, did not show patterns attributable to the geothermal power plant emissions. Further, results of the surveys in relation to geothermal power plant emissions showed weak indications of effects on Tarchonanthus camphoratus shrub growth and health around the Olkaria geothermal power plants in Kenya, while in Iceland, the growth of Racomitrium lanuginosum moss was reduced around the Hengill geothermal power plants. Additionally, the experiments showed that, 30 µg/L aqueous H2S (10.96 ppm in air) may be a tolerable limit for plants around geothermal power plants in Kenya and Iceland. These findings serve as important baseline data towards environmental monitoring and management around both geothermal power plant areas in Kenya and Iceland; this information is also of utmost importance in advising the public and decision makers in Kenya and Iceland on the ecosystem (terrestrial) impacts of geothermal power plant emissions.