David J. Mitchell

Influence of climatically induced cycles in physical weathering

Abstract Climatically induced cycles of stone temperature and moisture content may result in physical rock weathering through various mechanisms. These mechanisms cause rock to oscillate between periods of expansion and contraction, resulting in compressive and tensile stresses. Cycles of compression and tension may cause fatigue of the stone and therefore the frequency of these cycles may be of critical importance. The temperature and moisture content of stones with four different aspects were monitored over one year and the frequency of heating-cooling, wetting-drying and freeze-thaw cycles calculated. Heating-cooling cycles were found to occur on all aspects, but the highest frequency of cycles occurred on south and west aspects during summer months. Heating and cooling of stone creates a thermal gradient within the stone, which is critical in causing insolation weathering. Differences in the rate of thermal expansion between minerals or superficially degraded parts of stone may also contribute to breakdown. Moisture availability may alter the mechanisms by which heating—cooling causes weathering. Cycles of wetting—drying are less frequent than heating—cooling cycles, but may cause weathering by five mechanisms, depending upon the hygrometric gradients. Freeze-thaw cycles show a much lower frequency than heating—cooling and wetting—drying cycles, but are active on all aspects.

Real time measurements of sandstone deterioration: a microcatchment study

Abstract In order to gain a greater insight into the mechanisms responsible for the deterioration of sandstone buildings, chemical analysis of runoff water from sandstone and glass (control) surfaces has been carried out. Results indicate that the blocking of the stones pores by atmospheric particulates, soluble salts and algae may be involved in this decay. Evidence is presented which indicates that pressures created by salts and trapped moisture may cause the detachment of surface layers of sandstone from buildings. Weakening by kaolinite formation is identified as a potential factor in sandstone weathering.

The Relationships between Indoor and Outdoor Respirable Particulate Matter: Meteorology, Chemistry and Personal Exposure

Respirable particulate matter was collected inside and outside of a building located in Wolverhampton city centre during the same time period between 19/9/00 and 1/5/01. A total of 103 pairs of indoor and outdoor measurements were made using Casella personal dust monitors. The building monitored was located in a small street canyon produced by 4- and 5-storey buildings on both sides of the road. The road is the main approach road to a major bus station and is used by large numbers of heavy-duty diesel vehicles each day. The mean concentration for outdoor samples was 27.6 and 9.8 µg·m–3 for indoor samples. The mean indoor/outdoor ratio for this period was 0.4 (±0.02 SE). Meteorological variables including wind speed, wind direction and precipitation were measured at a nearby urban monitoring station. A greater wind speed caused an increase in the quantity of outdoor generated particulates penetrating indoors. Wind direction affected both indoor and outdoor particulate concentrations, with lower concentrations being observed when the wind direction was parallel to the street canyon. The indoor/outdoor ratio also showed a decrease during parallel wind conditions. During days with high amounts of precipitation, the concentration of particulates, both indoors and outdoors, decreased significantly. The personal exposure of a building occupant was measured for 20 working days in conjunction with outdoor and indoor measurements. Personal exposure concentrations were well correlated with indoor concentrations (r2 = 0.98). Forty of the indoor and outdoor particulate samples of dust were chemically analysed for sulphate, nitrate, chloride, zinc, copper, manganese and aluminium to determine any indoor/outdoor relationships of particulate chemistry and any interrelationships between the analytes.

Stone deterioration in polluted urban environments

Stone Weathering and Urban Particulate Pollution in the UK: David E. Searle and David J. Mitchell Urban Pollution and Stone Weathering in the Black Country: David E. Searle and David J. Mitchell Potential for Building Stone Soiling from Vehicle-related Pollutants Along-side a Busy Road: Paul Giess and Vaughan Shilton Weathering of Rocks by Lichens with Special Reference to Stonework: A Review: M.J. Wilson Experimental Studies of Rock Weathering by Plant Roots: Updating the Work of Julius Sachs (1832-1897): D.N. Mottershead and H.A. Viles Comparison of the Process of Decay of Two Limestones in a Polluted Urban Environment: A. T r k Initial Stages of Sandstone Decay in a Polluted Urban Environment: Alice V. Turkington Role of NO2 and SO2 on the Degradation of Limestone: G.C. Allen et al. Dry Deposition of SO2 on Carbonate Stone: An Overview of Laboratory Studies: Elizabeth A. Bede Development and Potential Uses of Computer Simulation Techniques in the Study of Rock Weathering: Sarah Antill an

The effects of coal and diesel particulates on the weathering loss of two major building stones in the United Kingdom—A comparative microcatchment study

Publisher Summary Coal derived particulates in the UK urban atmosphere have been significantly reduced because of reductions in domestic usage, legislation, and changes in fuel use. Majority of particulate in the urban atmosphere originate from vehicle exhausts because of increase in road usage and an expansion in the use of diesel engines. Particulate matter, resulting from coal combustion, has been recorded as being present in black patinas on some historic stone buildings and monuments, and it has been associated with accelerated weathering of stone surfaces as a result of enhanced gypsum formation. Some recent researches show the role of diesel particulates as a potential catalyst for the promotion of sulfation. This chapter describes the comparative study conducted to study the effects of coal and diesel particulates on the weathering of stones by using the technique of microcatchments under ambient atmospheric conditions. Slabs of Hollington sandstone and Portland limestone were artificially loaded with coal and diesel particulates, both separately and in various combinations. These slabs were then exposed to atmospheric conditions utilizing the microcatchment technique. All the chemical changes occurring as a result of the treatments were determined by comparison with an untreated stone control. The chapter provides tables and graphs to illustrate the results of analyses. It was found that diesel coated Portland limestone samples showed a significant reduction in both the rate of weathering loss and the volume of precipitation run-off when, compared to untreated samples. The samples treated with a combination of both particulate types demonstrated a highly significant increase in the volume of precipitation run-off from the sandstone microcatchments.

The Characterisation of Settled Dust by Scanning Electron Microscopy and Energy Dispersive X-ray Analysis

Settled dust has been collected inside the main foyers ofthree University buildings in Wolverhampton City Centre,U.K. Two of the three buildings are located in a streetcanyon used almost exclusively by heavy duty dieselvehicles. The dust was collected on adhesive carbonspectro-tabs to be in a form suitable for analysis byscanning electron microscope and energy dispersive X-rayanalysis. Using these analytical techniques, individualparticle analysis was undertaken for morphology andchemistry. Seasonal variations and variations due tolocation were observed in both the morphologicalmeasurements and chemical analysis. Many of the differencesappear attributable to the influence of road traffic, inparticular, the heavy duty diesel vehicles, travellingalong the street canyon.

The influence of building orientation on climate weathering cycles in Staffordshire, UK

Publisher Summary Climate or meteorological induced cycles are associated with weathering processes of building stone for a long time. Freeze-thaw cycles have severe effects on stone disintegration. Other cycles such as heating-cooling and wetting- drying creates similar stresses in stone. During certain synoptic conditions, building orientation has a great influence on climatic extremes of different facades. The use of sensors and data loggers has opened up the potential for in-depth investigations of general climatic monitoring of the exterior of buildings and effect of cyclic changes in temperature and moisture on stone. The chapter describes the study conducted to evaluate the frequency of heating-cooling, wetting-drying, and freeze-thaw cycles on the four cardinal faces of the tower of Lichfield Cathedral, Staffordshire, UK by using temperature and humidity sensors located on them.. It focuses on the assessment of the influence of orientation of building on the frequency of climatic cycles. The west and south faces have the highest frequency, whereas the north and east have the lowest values, with the north having the least. These could be loosely termed the “maritime” and “continental” faces, respectively. In a parallel study of 30 sandstone churches in the West Midlands, the occurrences of 18 forms of weathering were recorded. Granular disintegration, spalling, multiple flaking, total case hardened stone, and total autotrophic stone were found to be the greatest on the north; and relief weathering and total blackened stone were the greatest on south and west aspects.

Climatic Constraints to Crop Production in the Red Soils Area of Southern China

A review of the climate of southern China combined with data from an experimental site in Yunnan Province reveals a number of climatic constraints to crop production in the area dominated by red soils. In addition to the well-known effects of late summer drought and high summer evaporation, other factors include variability of the onset date of the summer monsoon as well as the intensity and damaging effects of the monsoon. Other climatic constraints identified are the occurrence of cold conditions and frost during the winter monsoon and local microclimatic variability due to topographic factors.