187
mg k -1 respectively. Most surface sediments show copper levels in excess of the baseline, with greatest concentrations near the river channel. Zinc shows a similar distribution to copper and is also clearly contributed to the lake from the river. Lead levels however remain reasonably consistent across the lake, and the element is not significantly contributed by the river sediment load. Such a distribution is typical of lead which displays a low mobility in the surface environment.
This study demonstrates that although Lake Daviumbu is lateral to the Fly River, it is clear from the sedimentary geochemistry that it is the river sediments not the surrounding land which is the dominant source for allochthonous material. The data provided by this study will be valuable baseline for future environmental monitoring of the impact of the copper-gold mine on the lateral lakes of the Fly River.
Relative abundance of radon-222 and radon-220 in soil gas in Northamptonshire and a preliminary assessment of indoor radon risk potential G.Sharman Geology Department, University of Leicester, England Emanometry is a rapid technique for measuring radon in soils, used here on sedimentary rocks of Northamptonshire. Radon-222 and Rn-220 can be differentiated in one soil gas sample by three consecutive one-minute counts. When low numbers of disintegrations per minute are found counting error can become important. This can be calculated and is about + 2 Bq L -1. The mean Rn-222 found on M i d d l e L i a s M a r l s t o n e R o c k B e d and Northampton Sand Ironstone is 25 Bq L -1 and 22 B q L -1. Rn-220 is 30 Bq L -1 and 34 Bq L -1 respectively. Seasonal variations over rocks with a high radon count are greater than over rocks with a low count. Typically values in Lower Lias Clay during summer are found to be four times the winter average. There is little difference between summer and winter values in rocks of the Great Oolite. On all rock types measured, the seasonal variation in Rn-220 is greater than in Rn-222. When mapping
radon to assess the potential risk for buildings, winter should be avoided because soil beneath buildings resembles outdoor summer conditions. The focus of soil gas radon measurements is their disputed suitability to predict indoor values. In Northamptonshire, where measurements have been made in soils subjacent to properties with known average indoor values, admittedly poor correlation is found. This is however partly attributable to differences in building construction, heating and ventilation. The ability of radon to escape from soils of different permeabilities at different rates should be recognised. A soil gas radon value capable of producing the indoor Action Level can be calculated for each rock type from the average indoor and soil gas radon values. A good correlation is found between the percentage of soil gas values exceeding this calculated figure, and the percentage of indoor values exceeding 200 Bq m -3.
mg k -1 respectively. Most surface sediments show copper levels in excess of the baseline, with greatest concentrations near the river channel. Zinc shows a similar distribution to copper and is also clearly contributed to the lake from the river. Lead levels however remain reasonably consistent across the lake, and the element is not significantly contributed by the river sediment load. Such a distribution is typical of lead which displays a low mobility in the surface environment.
This study demonstrates that although Lake Daviumbu is lateral to the Fly River, it is clear from the sedimentary geochemistry that it is the river sediments not the surrounding land which is the dominant source for allochthonous material. The data provided by this study will be valuable baseline for future environmental monitoring of the impact of the copper-gold mine on the lateral lakes of the Fly River.
Relative abundance of radon-222 and radon-220 in soil gas in Northamptonshire and a preliminary assessment of indoor radon risk potential G.Sharman Geology Department, University of Leicester, England Emanometry is a rapid technique for measuring radon in soils, used here on sedimentary rocks of Northamptonshire. Radon-222 and Rn-220 can be differentiated in one soil gas sample by three consecutive one-minute counts. When low numbers of disintegrations per minute are found counting error can become important. This can be calculated and is about + 2 Bq L -1. The mean Rn-222 found on M i d d l e L i a s M a r l s t o n e R o c k B e d and Northampton Sand Ironstone is 25 Bq L -1 and 22 B q L -1. Rn-220 is 30 Bq L -1 and 34 Bq L -1 respectively. Seasonal variations over rocks with a high radon count are greater than over rocks with a low count. Typically values in Lower Lias Clay during summer are found to be four times the winter average. There is little difference between summer and winter values in rocks of the Great Oolite. On all rock types measured, the seasonal variation in Rn-220 is greater than in Rn-222. When mapping
radon to assess the potential risk for buildings, winter should be avoided because soil beneath buildings resembles outdoor summer conditions. The focus of soil gas radon measurements is their disputed suitability to predict indoor values. In Northamptonshire, where measurements have been made in soils subjacent to properties with known average indoor values, admittedly poor correlation is found. This is however partly attributable to differences in building construction, heating and ventilation. The ability of radon to escape from soils of different permeabilities at different rates should be recognised. A soil gas radon value capable of producing the indoor Action Level can be calculated for each rock type from the average indoor and soil gas radon values. A good correlation is found between the percentage of soil gas values exceeding this calculated figure, and the percentage of indoor values exceeding 200 Bq m -3.
