Modelling Environmental Impacts of Cesium-137 Under a Hypothetical Release of Radioactive Waste.

Waste tanks at the nuclear facility located at Sellafield, UK, represent a nuclear source which could release radionuclides to the atmosphere. A model chain which combines atmospheric transport, deposition as well as riverine transport to sea has been developed to predict the riverine activity concentrations of 137Cs. The source term was estimated to be 9 × 104 TBq of 137Cs, or 1% of the assumed total 137Cs inventory of the HAL (Highly Active Liquid) storage tanks. Air dispersion modelling predicted 137Cs deposition reaching 127 kBq m-2 at the Vikedal catchment in Western Norway. Thus, the riverine transport model predicted that the activity concentration of 137Cs in water at the river outlet could reach 9000 Bq m-3 in the aqueous phase and 1000 Bq kg-1 in solid phase at peak level. The lake and river reaches showed different transport patterns due to the buffering effects caused by dilution and slowing down of water velocity.

Quantification of the effect of environmental changes on the brownification of Lake Kukkia in southern Finland.

The browning of surface waters due to the increased terrestrial loading of dissolved organic carbon is observed across the northern hemisphere. Brownification is often explained by changes in large-scale anthropogenic pressures (including acidification, and climate and land-use changes). We quantified the effect of environmental changes on the brownification of an important lake for birds, Kukkia in southern Finland. We studied the past trends of organic carbon loading from catchments based on observations taken since the 1990s. We created hindcasting scenarios for deposition, climate and land-use change in order to simulate their quantitative effect on brownification by using process-based models. Changes in forest cuttings were shown to be the primary reason for the brownification. According to the simulations, a decrease in deposition has resulted in a slightly lower leaching of total organic carbon (TOC). In addition, runoff and TOC leaching from terrestrial areas to the lake was smaller than it would have been without the observed increasing trend in temperature by 2 °C in 25 years.