Belinda Colston

Investigating the effects of humidity and salt crystallisation on medieval masonry

An investigation of the effects of humidity and salt crystallisation on medieval masonry has been undertaken at the parish church of Walpole St Andrew, Norfolk, with the intention of establishing a relationship between changes in environmental conditions and levels of stone decay. Masonry within the church has been contaminated with sodium chloride salts, which are undergoing cycles of crystallisation/dissolution in response to fluctuations in relative humidity corresponding to the equilibrium relative humidity of the salt. The effects of these cycles have been determined by a combination of gravimetric analysis, ion chromatography, and qualitative assessment of deposited material. Appropriate remedial action, based on a combination of desalination techniques and environmental control, is put forward for discussion.

A preliminary study of the reduction of Np(VI) by formohydroxamic acid using stopped-flow near-infrared spectrophotometry

The kinetics of the reduction of NpO22+ to NpO2+ in nitric acid aqueous solution by formohydroxamic acid (FHA) were studied to allow more accurate flow sheet modelling of neptunium separation from uranium and plutonium in an Advanced PUREX process. The rate of the reaction was monitored using stopped-flow spectrophotometry with near-infrared detection. The conditional reduction rate in 2 M nitric acid at 22°C could be described by the following equation: -d [NpO22+]/dt = k [NpO22+][FHA](M/s) with k = 1.17×103 M-1 s-1 at [H+] = 2.0 M. Comparison with other data available in the literature, indicates that formohydroxamic acid is an unusually strong reducing agent for NpO22+.

Environmentally-induced stone decay: the cumulative effects of crystallization–hydration cycles on a Lincolnshire oopelsparite limestone

An investigation has been undertaken at St Andrew’s church, Walpole St Andrew, Norfolk, to establish the underlying causes of the observed stone decay to the upper parts of the six stone piers. The stone decay was first recorded in the early 1930s. The salt-contaminated masonry within the church has been shown to undergo severe salt decay during the summer, with little damage occurring over the winter months. The south aisle piers have been shown to decay 2.5 times faster than the north aisle piers. Although crystallization–hydration cycles have been identified, the rate of decay is at its greatest when the cycling is relatively infrequent. This was not the expected trend. Furthermore, it has been shown that during extended periods where the ambient relative humidity is less than 75%, the rate of decay reaches a maximum. It is the length of this ‘drying’ period that apparently has the greatest influence on the rate of decay and could explain the significant difference in the rate of decay between the south and north aisle piers. The results have serious implications for passive conservation, where it is often recommended to lower the ambient relative humidity to well below the equilibrium relative humidity of the salt contaminant, to avoid crystallization–hydration cycles. Since, at the time of building, the church was situated on the coast, it is possible that the sodium chloride contamination occurred during the building process (1440–1520), particularly since the area was prone to sea-flooding at this time. Alternatively, the salt could have been applied as a treatment during the general restoration of 1897. Whatever the source of the salt, it seems likely that the ambient environment was changed by the insertion of a sealed floor in 1897, which could account for the onset of the salt decay.

Use of Metal Ion Indicators to Determine Complex Stability Constants: the Method of Competitive Equilibration

The work presented illustrates the feasibility of using metal ion indicators to study various aspects of complexation reactions. The overall aim of the work was to develop a simple method for studying metal–ligand complexation relevant to the environmental migration of radionuclides. The reaction of Xylenol Orange with zinc(II) ions is investigated as a simple model system, initially determining the variation of equilibrium constant with ionic strength. The data are used to show the validity of the Davies equation to predict equilibrium constants in systems where I<0.1 M. By the introduction of a second ligand (sulfate) to the zinc–Xylenol Orange mixture, competitive equilibration is used to determine the equilibrium constant of the zinc–sulfate reaction. The experimental data (giving K0=218.8) show good agreement with literature values, thus illustrating the validity of this approach to measure complex stability constants in systems where other methods are difficult or even impossible.

Regional variation in the mechanical properties of cortical bone from the porcine femur

Despite the widespread use of porcine bone as a substitute for human bone in the development of surgical technique and the use of fixation devices, relatively few studies have reported on the mechanical behaviour of porcine long bones. Regional variation in the mechanical properties of cortical bone from porcine femora was investigated using three-point bending and cutting tests. Results were related to measurements of bone architecture and composition and Rutherford backscattering spectrometry (RBS) was used to calculate the calcium to phosphorus ratio. There was significant, but limited, regional variation in the strength of the femur with bone from the distal, posterior quadrant (241.4 ± 10.43 MPa) being significantly stronger than that of the lateral quadrant (162.3 ± 17.96 MPa). Cortical bone was also anisotropic; samples cut transverse to the bones axis were around six times tougher than those cut parallel to the axis (p<0.05). This corresponded with a significant negative correlation between the Youngs modulus and toughness when cut along the longitudinal axis. RBS analysis of cortical bone samples gave a Ca:P ratio of 1.37 ± 0.035, somewhat lower than that reported for cortical bone of adult human femora. These results indicate that the mechanical properties of cortical bone show significant, but limited, variation around the porcine femur and that this should be taken into consideration when sampling and choosing an appropriate animal model for orthopaedic biomechanics research.

Ionic strength effects in modelling radionuclide migration in environmental systems: Estimating the errors and uncertainties

Abstract Thermodynamic models are widely used to predict the chemical behaviour of radionuclides in the geosphere. The accuracy of such predictions depends upon the quality of the thermodynamic data used in the calculations. These data are affected by the ionic strength of the system. In most environmental situations modelled, the ionic strength is rather low: sea water is about 0.5 molal but many groundwaters are less than this (0.1–0.001 molal). By contrast, the great majority of experimental measurements of formation constants have been made at high ionic strength, between 1 and 10 molal, and in the majority of cases, measurements have been made at only one ionic strength. With the lack of thermodynamic data at ‘environmental’ ionic strengths, modellers find themselves having to extrapolate with only one data point! For instance, the formation constants of the actinides, of particular importance in radioactive waste disposal, have nearly all been measured at a single, high, ionic strength. There are a number of methods for extrapolating such data: the most widely used is the Davies equation. The magnitude of the errors that may be incurred by utilising this method, particularly with data at high ionic strength, has been evaluated, and found to be typically several orders of magnitude.

Analysis of Bat Wing Beat Frequency Using Fourier Transform

Computer vision techniques have been used extensively to automatically monitor human activities; however, applications for analysing animal behaviour are sparse. The analysis of bat behaviour in particular has attracted only one or two studies. Most existing work uses either expensive thermal imaging equipment, or bespoke sensors which are not accessible to field researchers, ecologists, and scientists studying behaviour. The work we present here uses spectral analysis techniques to quantify wingbeat frequency, using a single imaging device in low-light. We propose two modified techniques based on bounded box metrics, and similarity matrices, for measuring periodic and cyclical motion as a 1D time domain signal. These are transformed to the frequency domain using Short Time Fourier Transform (STFT). Finally we evaluate these techniques against the baseline algorithm proposed by Cutler and Davis [5], using expert-annotated ground-truth data.

KINETICS IN A EU(III)-HUMIC ACID SYSTEM BY ISOTOPIC EXCHANGE WITH 152MEU3+AND SIZE EXCLUSION CHROMATOGRAPHY : A FEASIBILITY STUDY

The work presented illustrates the feasibility of using radiotracers with size exclusion chromatography (SEC) as a means of studying the kinetics of metal-ligand interactions in environmental systems. To simulate such systems a pre-equilibrated Eu(III)-humic acid model system was chosen in which 152mEu3+ as a radiotracer was used to study the isotopic exchange between Eu3+ and Eu(III)-humic acid complexation.

Determination of Arsenic, Mercury and Barium in herbarium mount paper using dynamic ultrasound-assisted extraction prior to atomic fluorescence and absorption spectrometry

A dynamic ultrasound-assisted extraction method using Atomic Absorption and Atomic Fluorescence spectrometers as detectors was developed to analyze mercury, arsenic, and barium from herbarium mount paper originating from the herbarium collection of the National Museum of Wales. The variables influencing extraction were optimized by a multivariate approach. The optimal conditions were found to be 1% HNO3 extractant solution used at a flow rate of 1 mL min−1. The duty cycle and amplitude of the ultrasonic probe was found to be 50% in both cases with an ultrasound power of 400 W. The optimal distance between the probe and the top face of the extraction chamber was found to be 0 cm. Under these conditions the time required for complete extraction of the three analytes was 25 min. Cold vapor and hydride generation coupled to atomic fluorescence spectrometry was utilized to determine mercury and arsenic, respectively. The chemical and instrumental conditions were optimized to provide detection limits of 0.01 ng g−1 and 1.25 ng g−1 for mercury and arsenic, respectively. Barium was determined by graphite-furnace atomic absorption spectrometry, with a detection limit of 25 ng g−1. By using 0.5 g of sample, the concentrations of the target analytes varied for the different types of paper and ranged between 0.4–2.55 µg g−1 for Ba, 0.035–10.47 µg g−1 for As, and 0.0046–2.37 µg g−1 for Hg.

Preliminary investigations of pentachlorophenol emissions from biocide-treated masonry: a source of indoor air contamination

An empty, unoccupied basement room in Melton Constable Hall, Norfolk (England), was chosen as a case study to determine whether pentachlorophenol (PCP) treatment of masonry could significantly elevate PCP concentrations in indoor air, thus posing a potential health hazard. This particular room was chosen because it contained a vast quantity of crystalline PCP on the surface of a previously treated wall, and, being rarely used, was less likely to be subject to any external sources of PCP contamination. Analysis of dust debris, airborne particulates, passively deposited suspended particulates and volatile PCP emissions from the contaminated surface showed no evidence that inhalation was a probable route of PCP exposure.