Robert Inkpen

Carbonate crystals precipitated by freshwater bacteria and their use as a limestone consolidant.

ABSTRACT Bacterial carbonate precipitation is known to be a natural phenomenon associated with a wide range of bacterial species. Recently, the ability of bacteria to produce carbonates has been studied for its value in the conservation of limestone monuments and concrete. This paper describes investigations of carbonate crystals precipitated by freshwater bacteria by means of histological (Loefflers methylene blue and alcian blue-periodic acid-Schiff stain) and fluorescence (CTC [5-cyano-2,3-ditolyl tetrazolium chloride]) stains, determination of cell viability inside carbonate crystals, and pore size reduction in limestone by image analysis. Carbonate crystals were found to be composed of bacteria embedded in a matrix of neutral and acid polysaccharides. Cell viability inside the carbonate crystals decreased with time. On stone, bacteria were found to form carbonate crystals, with only a few bacteria remaining as isolated cells or as cell aggregates. Pore size was reduced by about 50%, but no blockage was detected. Taken together, the results of this research provide some reassurance to conservators that biocalcification by bacteria could be a safe consolidation tool in a restoration strategy for building stone conservation.

Trends in stone weathering and atmospheric pollution at St Paul's Cathedral, London 1980–1990

Micro-erosion meter measurements on the balustrade of St Pauls Cathedral, London, already taken annually from 1980 to 1985, were repeated in 1990. The new data continue to show no significant changes in rates of surface lowering over time. This sustained level of weathering has occurred despite decreases in SO2 concentrations in central London in the same period.

The Topography of Historical Contingency

Abstract Starting with Ben-Menahem’s definition of historical contingency as sensitivity to variations in initial conditions, we suggest that historical events and processes can be thought of as forming a complex landscape of contingency and necessity. We suggest three different ways of extending and elaborating Ben-Menahem’s concepts: (1) By supplementing them with a notion of historical disturbance; (2) by pointing out that contingency and necessity are subject to scaling effects; (3) by showing how degrees of contingency/necessity can change over time. We also argue that further development of Sterelny’s notion of conditional inevitability leads to our conclusion that the topography of historical contingency is something that can change over time.

Influence of Environmental Temperature on Biocalcification by Non-sporing Freshwater Bacteria

The process of biocalcification, recognised as precipitation of calcium carbonate, has been described as a widespread phenomenon associated with a wide range of different bacterial species. This biocalcifying activity, and factors that affect it, have been widely studied in moderately halophilic bacteria but there is a lack of information on factors that affect biocalcification by freshwater bacteria. In this paper, we study how temperature can affect biocalcification by freshwater bacteria that potentially could be used for the process of bioconsolidation during conservation. Ten isolates were characterised by standard biochemical and API 20NE tests. Their biocalcifying activity was studied at temperatures between 10 and 40°C in B4 liquid medium. Mineralogical and quantitative analyses of the crystals were carried out by XRD, and morphological studies by SEM. Biocalcification only occurred when bacteria were present and were able to grow. Carbonate precipitation by bacteria increased with time and temperature of incubation. Temperature affected not only the amount of precipitation but also crystal quality and morphology. As bioconsolidant agents, these organisms could be applied to stone when the temperature does not exceed 40°C depending on the type of isolate.

Identification and quantification of weathering by plant roots

Small weathering forms were produced on polished marble tablets by the etching action of plant roots. Imagery of the forms was obtained with a high quality photogrammetric scanner. Automated classification methods, used in image processing, proved inadequate for identifying etched areas, but observer defined mapping within a GIS was able to identify and map the extent and intensity of etching across a range of scales. Root etching patterns were not apparently influenced by forms produced during tablet preparation. Root etching occurs across grains and at grain boundaries, and appears to be more intense at the junction of root networks.

Rates of stone loss at St Paul's Cathedral, London

Abstract Rates of surface lowering of the Portland stone balustrade of St Pauls Cathedral, London are presented. Long term rates (1718–1987) are derived from measurements of lead plugs (LPI) on the top of the balustrade and average 0.081 mm a−1. Short term rates, provided by micro-erosion meter (MEM) measurements between 1980 and 1985, average 0.06 mm a−1. The use of means obscures important spatial and temporal variability within the data sets.

Assessing historical saltmarsh change; an investigation into the reliability of historical saltmarsh mapping using contemporaneous aerial photography and cartographic data

Habitat protection, creation and management are at the forefront of nature conservation throughout the world. Many terrestrial and marine ecosystems are under pressure from a diverse range of issues including impacts associated with climate change, multiple resource use and increased development. Saltmarsh within the United Kingdom, is one such valuable habitat which has suffered significant losses over the last eighty or so years. Any environmental management practice or decision applied to these areas, should ideally be based on evidence of processes and change. One potential way of measuring saltmarsh change is by using historical maps and aerial photographs to look for patterns of growth or reduction. This research examines the process of saltmarsh mapping and compares historical aerial photographs and maps to assess their suitability for habitat change assessment. This research suggests that whilst historical aerial photography can be accessed and utilised effectively, the data presented on maps should be treated with a great deal of caution. The saltmarsh represented on the maps used in this research was noticeably different from that mapped using aerial photographs from a similar time period. Whilst this does not dismiss the use of historic maps along this part of the coast, it does suggest they should be treated with some degree of caution and will vary in their reliability.

Mapping Palestine and Mesopotamia in the First World War

Abstract The survey and mapping activities which took place in Palestine and Mesopotamia during the First World War need to be considered in their contexts, both of long-term British mapping activities in the region, and of survey and mapping generally during the First World War. Thus, while it is important to recognise the real technical advances in map-making which resulted from survey activities in the Near and Middle East during the First World War, it needs to be recognised that this was simply the culmination of nearly 80 years of British military mapping in the region. Each generation of surveyors used the most appropriate tools for the task in hand and the conditions under which the survey needed to be conducted. The First World War surveyors were fortunate that a new tool, aerial photography, had become available just prior to the war.

The RGS, exploration and Empire and the contested nature of surveying

In 1879, the RGS started courses in practical surveying based on the methods used by navigators. Subsequently, RGS courses, increasingly under the influence of former members of the Survey of India, changed in character. At the same time as the nature of appropriate surveying was being negotiated within the RGS, the debate over the academic nature of geography also took shape. The development of the ‘new’ geography reflected the conflicts within the RGS Council over the meaning of scientific geography.

Fitness spaces and their potential for visualizing change in the physical landscape

The use of the metaphors of general fitness and N-K spaces can assist in the understanding of the development of the physical landscape. Different modes of change can be viewed as different types of movement in, and distortions of, these phase spaces. Visualized in this manner landscape change can be viewed as both channelized, constrained and random.