Gavin K Gillmore

Radon in the Creswell Crags permian limestone caves

An investigation of radon levels in the caves of Creswell Crags, Derbyshire, an important Site of Special Scientific Interest (SSSI) shows that the Lower Magnesian Limestone (Permian) caves have moderate to raised radon gas levels (27-7800 Bq m(-3)) which generally increase with increasing distance into the caves from the entrance regions. This feature is partly explained in terms of cave ventilation and topography. While these levels are generally below the Action Level in the workplace (400 Bq m(-3) in the UK), they are above the Action Level for domestic properties (200 Bq m(-3)). Creswell Crags has approximately 40,000 visitors per year and therefore a quantification of effective dose is important for both visitors and guides to the Robin Hood show cave. Due to short exposure times the dose received by visitors is low (0.0016 mSv/visit) and regulations concerning exposure are not contravened. Similarly, the dose received by guides is fairly low (0.4 mSv/annum) due in part to current working practice. However, the risk to researchers entering the more inaccessible areas of the cave system is higher (0.06 mSv/visit). This survey also investigated the effect of seasonal variations on recorded radon concentration. From this work summer to winter ratios of between 1.1 and 9.51 were determined for different locations within the largest cave system.

Tidal synchronicity of built-environment radon levels in the UK

In our recent work on radon in UK homes the authors have observed tidal-periodic variations in built-environment radon levels and here report results from our ongoing investigations. These tidal variations have been quantified using a variety of analytical techniques, including a novel correlation technique developed as part of this investigation. The observed variations are cyclic at the 14-15 day tidal period and lag new/full moons by varying periods of days, the magnitude of the variation and lag being dependent on factors such as location, underlying geology and rock/soil hydration. As well as quantification and discussion of tidal effects on radon levels, the potential effects of such phenomena on the reliability of short-term radon measurements are discussed.

Cretaceous-tertiary palaeo-bathymetry in the northern north sea; integration of palaeo-water depth estimates obtained by structural restoration and micropalaeontological analysis

Temporal and spatial variations in palaeo-water depth are crucial parameters in basin analysis since changes in palaeo-bathymetry detail the amount of sediment underfill during basin evolution. By carefully integrating seismic-stratigraphic observations with palaeo-water depth estimates from structural restoration and micropalaeontological data, changes in accommodation space throughout the Cretaceous-Tertiary post-rift interval are documented on a regional scale in the northern North Sea. Since it is not possible to determine the palaeo-water depth exactly, we have focused on determining most likely water depth figures, and identifying the principal shallowing and deepening trends. The inferred trends from the investigated wells are generally in good agreement with each other on a regional scale, especially when the tectonic position within the basin is taken into account. The inferred general trends are: (1) general shallowing superimposed on several transgressive/regressive events during the Early Cretaceous; (2) deepening from the early Cenomanian to mid-Campanian; (3) shallowing from the mid-Campanian to latest Maastrichtian; (4) deepening in the Early to Late Paleocene; (5) shallowing from the Late Eocene to Late Miocene; (6) deepening from the Late Miocene to Early Pliocene; (7) shallowing during Pliocene time. Early Cenomanian to latest Maastrichtian and the late Eocene to Pliocene events correspond with changes in eustatic sea level, but the deepening/shallowing trends were probably amplified by tectono-thermal effects. The events in the Early Cretaceous, Early to Late Paleocene, and Late Miocene to Early Pliocene cannot be explained by the eustatic sea-level curve, and therefore need to be explained by purely tectono-thermal events.

A critical comparison of the cost-effectiveness of domestic radon remediation programmes in three counties of England

Radon remediation programmes in domestic dwellings were carried out in five areas, from three counties of England, and the total costs obtained. A single company, which abided by the Code of Practice of the Radon Council of Great Britain, carried out the remediation. The dose savings from the programmes were calculated and used to estimate the number of lung cancers averted. The data obtained allowed the cost-effectiveness of the remediation programmes in each area to be calculated. The remediation programmes in three areas (Northants 2, 3 and North Oxfordshire) were cost-effective whereas those in two areas (Northants 1 and North Somerset) were not. To be cost-effective, the Northants I and North Somerset areas would need to increase the number of householders that carried out remediation, if they were over the UK Action Level. Health policy makers should concentrate their resources on communities in areas where there is a significant proportion of dwellings above the UK Action Level and where the number of properties being remediated is low.

Structural restoration of Cretaceous-Cenozoic (post-rift) palaeobathymetry in the northern North Sea

Palaeobathymetric variations and palaeobasin shape are important for recognition of tectonic phases and distribution of sediment. We present an approach for restoring palaeobathymetry from interpreted, depth-converted seismic sections. The method involves section balancing/restoration techniques for extensional regimes and seismic sequence stratigraphy. The method is based on regional profiles that cover the entire basin using fixed water-depth points such as coal layers, shallow marine sand and subaerial unconformities, which are used to calibrate areas along the profile. Geometric information in the under- and overlying seismic sequences is used to shape the palaeobasin. The palaeowater-depths and basin gradients of the Cretaceous and Tertiary post-rift interval in the northern North Sea have been restored. The results show a highly segmented basin with high gradients and locally large water-depths in the earliest Cretaceous. A shallowing and a lowering of the basin gradients occurred in the early Cretaceous. A deepening and widening of the basin was initiated in the middle Cretaceous. During the late Cretaceous the water-depth and the basin gradients decreased. A deepening occurred in the Palaeogene resulting in high gradients on the flanks of the basin. The basin became shallower and the relief became smaller in the early Neogene. The basin deepened in the late Neogene and then became shallower to the present day. The palaeobathymetric trends correlate well with results obtained from micropalaeontological analysis of palaeowater-depth in the same area.

A new method of imaging particle tracks in solid state nuclear track detectors.

Solid state nuclear track detectors are used to determine the concentration of α particles in the environment. The standard method for assessing exposed detectors involves 2D image analysis. However 3D imaging has the potential to provide additional information relating to angle as well as to differentiate clustered hit sequences and possibly energy of α particles but this could be time consuming. Here we describe a new method for rapid high‐resolution 3D imaging of solid state nuclear track detectors. A ‘LEXT’ OLS3100 confocal laser scanning microscope (Olympus Corporation, Tokyo, Japan) was used in confocal mode to successfully obtain 3D image data on four CR‐39 plastic detectors. Three‐dimensional visualization and image analysis enabled characterization of track features. This method may provide a means of rapid and detailed 3D analysis of solid state nuclear track detectors.

Radon and 'King Solomon's Miners': Faynan Orefield, Jordanian Desert.

Concentrations of 222Rn were measured in ancient copper mines which exploited the Faynan Orefield in the South-Western Jordanian Desert. The concentrations of radon gas detected indicate that the ancient metal workers would have been exposed to a significant health risk and indicate that any future attempt to exploit the copper ores must deal with the hazard identified. Seasonal variations in radon concentrations are noted and these are linked to the ventilation of the mines. These modern data are used to explore the differential exposure to radon and the health of ancient mining communities.

The reconstruction and analysis of palaeowater depths: a new approach and test of micropalaeontological approaches in the post-rift (cretaceous to quaternary) interval of the northern North Sea

This paper explores and tests a new ecelectic approach to micropalaeontological data which are used to reconstruct palaeowater depths in the Norwegian North Sea in the period from the Cretaceous to Quaternary. These new ideas and evidence presented here promote a greater understanding of palaeobathymetry and basin evolution. This account focuses in particular upon Cretaceous to Cenozoic sediments in this region although the new approach has general applicability. Such information is important because palaeobathymetric variations and palaeobasin shape are essential for the recognition of tectonic phases, and understanding the distribution of sediments and source rocks. Palaeobathymetric curves with upper and lower depth limits derived in part from statistical analyses of micropalaeontological data were constructed to present the most likely depth variations through time in the region. The palaeobathymetric curves obtained from micropalaeontological investigations are compared with the palaeobathyemtric variations that were suggested by independent structural restorationms for the region. The outcomes of these two approaches are shown to be essentially similar which implies the soundness of this new approach to micropalaeontological data. Both the structural restoration and micropalaeontological results point to the following: a shallowing in the palaeowater depths in the Early Cretaceous; a deepening in the middle Cretaceous; a shallowing in the Late Cretaceous; a deepening in the Palaeogene; a shallowing in the early Neogene, and a deppening in the late Neogene (Pliocene). The Quaternary interval in wells in this study illustrates the complexity of the palaeoenvironmental record over this period of time, with some wells clearlt showing subsidence while others suggesting relative uplift. This complexity is the result of the impact of ice movement and multiple glaciations and subsequent isostatic re-adjustments.

Assessment of health risks to skin and lung of elevated radon levels in abandoned mines.

Abstract— Radon, together with its progeny, is present in high levels in some underground sites. Radon is known to increase the risk of lung cancer, while increased levels of radon decay products on the skin surface have been implicated in skin cancer induction and at sufficient levels might cause deterministic effects such as erythema. Although radon levels in working mines are controlled, radon in abandoned mines can reach very high levels, which would result in an occupant exceeding recommended annual exposure limits in less than 2 h in some mines. The relative importance of dose limits for the lung, skin cancer, and deterministic effects is discussed in the light of practical experience.

Sediments and Ostracoda from Courteenhall, Northamptonshire, UK and their implications for the depositional environment of the Pleistocene Milton Formation

The Milton Formation (Quaternary) of central Northamptonshire in the English Midlands comprises a suite of locally derived sands, gravels and occasional fine-grained sediments. The sedimentology and lithostratigraphic position of the deposit indicates that it was laid down under braided fluvial conditions and should be attributed to a pre-Anglian-Cromerian ( sensu lato ) stage of the Quaternary. This paper reports the first significant recovery of organic material from these deposits and presents analyses of Ostracoda contained therein. The assemblages of Ostracoda suggest the occurrence of at least one major climatic shift from temperate to cool conditions during the deposition of part of the Milton Formation and therefore imply that a braided regime had been established while the aquatic environment, at least, was still temperate. In addition, the stratigraphic ranges of six ostracod taxa have been expanded: Limnocythere sanctipatricii, Potamocypris arcuata, Eucypris virens and ilyocypris sp. A are recorded for the first time in pre-Anglian sediments, whilst Heterocypris incongruens has been found for the first time in the British Middle Pleistocene. Bradleystrandesia fuscatus has been recorded from British Pleistocene sediments for the first time.