Geological controls on radon potential in Scotland

222Rn, a natural radioactive gas produced by the radioactive decay of 238U, accounts for about 50 % of the total radiation dose to the average person in the UK. Geology is the most important factor controlling the source and distribution of radon; which has been linked to an increased risk of lung cancer. In order to prevent the public receiving high exposures to radon, it is necessary to identify those areas most at risk. We present results of new mapping of radon potential for Scotland using a method that allows the spatial variation in radon potential to be delineated both within and between geological groupings. The main geological and geochemical associations with moderate to high radon potential areas are described. The highest radon potential values in Scotland are associated with U-rich, highly evolved Siluro-Devonian biotite granite intrusions, notably those clustered within a zone to the west of Aberdeen and at Helmsdale, in Caithness. U mineralisation plays a role in areas including the Helmsdale granite and the Middle Old Red Sandstone of the Orcadian Basin. Elevated radon potential is also associated with limestones - where fracture permeability is influential - and with Ordovician-Silurian greywackes. The radon potential of unconsolidated deposits, and how this affects the radon potential of the underlying bedrock, reflects both their permeabilities and their compositions

An interhemispheric comparison of the concentrations of bromine compounds in the atmosphere

At least seven organic bromine compounds have been positively identified in the atmosphere1,2 (CH3Br, CH2Br2, CHBr3, CH2BrCl, CF3Br, CF2BrCl and C2H4Br2) and others have been observed in coastal seawater samples (C2H5Br, C3H7Br and CHBr2Cl) (S. A. P. and R. A. Rasmussen, unpublished data). The atmospheric chemistry of bromine compounds has considerable consequence in the stratosphere, where bromine acts as a more efficient catalyst than chlorine in removing ozone3,4. Several bromine compounds also fulfil an important role in the geochemical cycling of the element through the troposphere5. Here we present measurements of four bromine compounds (CF3Br, CH3Br, CH2Br2 and CHBr3) over a large latitudinal range (40° N to 75° S). These data suggest that the major source of bromine in the atmosphere could be bromoform (CHBr3), probably emitted from the ocean and with a short lifetime due to photolysis. Our data also suggest that the major emission of methyl bromide (CH3Br), and hence most bromine entering the stratosphere, will be anthropogenic

Improvements to a flame photometric detector to allow measurement of sulphur gases in ambient air

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Measuring ammonia emission rates from livestock buildings and manure stores. Part 1: development and validation of external tracer ratio, internal tracer ratio and passive flux sampling methods

There is a need for robust methods for measuring ammonia emission rates from livestock buildings and manure stores, to guide efforts to abate emissions from livestock farming. This paper reports research to develop and validate three candidate measurement techniques: (a) An external tracer ratio method, where concentrations of ammonia and sulphur hexafluoride are measured downwind of an animal house or manure store. (b) An internal tracer ratio (ITR) method, suited to animal housings, where concentrations of ammonia and sulphur hexafluoride are measured just before air leaves the building. (c) A flux sampler method, which uses sets of passive flux sampling devices positioned so as to intersect all significant flows of air out of an animal house or manure store source. All three of the measurement techniques were validated at a building section simulating a naturally ventilated (space-boarded) cattle house, with the external tracer ratio method also being validated at a simulated slurry store. In the validation tests on the external tracer ratio method the derived ammonia emission rates from the slurry store and cattle house validation studies were 25% below and 43% above the measured release rate, respectively. These biases were shown by t-tests to be statistically highly significant, but no clear explanation could be found for the different signs and magnitudes in the two cases. For the ITR method, recovery rates of 78% and 101% of released NH3 were achieved, with low and high release rates, respectively. Validation tests conducted on the flux samplers gave an average of 66% (standard deviation 2.9%) ammonia recovery. The cause of this non-ideal level of recovery has not yet been identified. However, given the low standard deviation, it was concluded that these samplers could be used to measure ammonia emission rates from real farm buildings, provided that a correction factor for the non-ideal recovery was applie

The measurement of hydrocarbon concentrations in the atmosphere at Harwell during the period April 1986 to March 1987

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Measuring ammonia emission rates from livestock buildings and manure stores : part 2: Comparative demonstrations of three methods on the farm

Comparative demonstrations of three methods (flux sampling, external tracer ratio, and internal tracer ratio), were mounted in four real farm situations. A flux sampling method was demonstrated at a commercial dairy cow house (slurry-based), at a commercial piggery (straw-based), at a full-scale above-ground cylindrical slurry store (dairy cow slurry) and a full-scale earth-bank lagoon (pig slurry). An external tracer ratio method was demonstrated, in parallel with the flux sampling method, at the dairy cow house and at the above-ground slurry store. An internal tracer ratio method was demonstrated at the dairy cow house only. At the dairy cow house, the corrected emission rates from the flux sampling method and from the external tracer ratio method agreed to within the estimated experimental range, while the emission rate from the internal tracer ratio method was significantly lower. The overall conclusion of the study is that all three methods can have a useful role, the choice of which to deploy depending on the particular measurements needed in each case. The paper includes a table (No. 7) which indicates which is the recommended method when each of various considerations has top priority. (C) 2004 Elsevier Ltd. All rights reserved

Observation on Great Dun Fell of the pathways by which oxides of nitrgoen are converted to nitrate.

Two field experiments to investigate the formation of nitrate as an airstream passes through a hill cap cloud have been performed at the UMIST field station on Great Dun Fell. Techniques chosen for the measurement of various nitrogen species are described. The results of the second field experiment are discussed and compared with those of the first. Evidence is found in support of the hypothesis that under the range of conditions studied, the dominant pathway for nitrate production is the solution of N2O5 formed from the reaction of NOx with O3 upwind. The effectiveness of this pathway by night and by day is observed to be a function of the NOx mixing ratio. A surface reaction rate constant of around 300 cm3 cm−2 s−1 for the hydration of N2O5 is inferred from the observations. These results are shown to be consistent with recent laboratory measurements of the rates of reaction of nitrogen species. It is suggested that pathways other than via N2O5 may be significant sources of nitrate under certain conditions that merit further investigation