SoilSoc Research

Research projects Thesis abstracts

The effect of electrical cable insulating oil on selected biological features of two Icelandic volcanic soils

Institute / Organisation / Unit: Agricultural University of Iceland (, University of Iceland ( and Reykjavík Energy (

Research director / Project Leader / Student Supervision: Dr. Rannveig Anna Guicharnaud Agricultural University of Iceland and Dr. Bergur Sigfússon Reykjavík Energy.

M.Sc. Student responsible: Taru Lehtinen ( (completed in summer 2007)

Discription: Soils are one of the natural sinks for contamination in the environment, one of the most common pollutants being organic compounds such as oil. There are 395 km of electrical cables with mineral cable insulating oil in the capital area of Iceland run by Reykjavik Energy and therefore the risk of leakage from the cables to the surrounding soil environment is significant. Prolonged leakage of the oil can possibly pose a threat to the surrounding ecosystems. In this study the effect of mineral cable insulating oil on the soil properties have been investigated. Two different soil types, Brown Andosol and Histic Andosol, were treated with 0 %, 1 %, 5 % or 10 % of mineral cable insulating oil by dry weight to assess the impacts of the oil on various soil functions. A laboratory microcosm experiment was set up and various physical, chemical and biological measurements were carried out. The main emphasis was on the biological functions of the soil such as total soil microbial biomass carbon, basal respiration as well as dehydrogenase and arylphosphatase activity. There was a difference between the soil types in the biological parameters that were measured throughout the experiment; in general there was a higher activity in the more organic Histic Andosol. The mineral cable oil increased the total soil microbial biomass carbon and dehydrogenase activity but decreased the arylphosphatase activity. Lack of oil degradation was indicated by stable soil pH throughout the experiment as well as insignificant differences in the cumulative respiration between the different pollution levels. Biomass correlated with dehydrogenase and arylphosphatase activity. Soil dissolved organic correlated with dehydrogenase and arylphosphatase activity. The results of this study indicated that changes in arylphosphatase activity could be used to identify potential concerns in Icelandic soil quality. Therefore the use of this enzyme for quantification of soil degradation in Icelandic soils could be suggested. Further long-term laboratory study as well study of the fate of oil that is continuously leaked into the soil environment is needed in order to understand the complexity of long-term and in-situ effects.