To facilitate its objective of high-resolution imaging of the Earth's crust and upper mantle, The Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL) has initiated studies into developing instrumentation capable of achieving that goal. The requirements include portable sensors capable of resolving seismic signals to 100 second periods. To test the feasibility of obtaining useful long-period seismic data from a portable array, prototype instruments were installed in hand excavated shallow holes (postholes) at several sites in various geologic settings across the continental United States. Three of the sites were near established seismic vaults and comparisons between posthole installation and vault installation were made. Results from this study indicate that posthole installation of long-period sensors may indeed be feasible: eight out of the 12 sites occupied had long-period background noise levels low enough to resolve 100-second surface waves generated from a magnitude 5.0 earthquake 30 degrees distant from the recording station. At periods less than 10 seconds, background noise recorded from postholes was no more than 3 dB. higher than that recorded in vaults. At 100 seconds, vertical noise was 11 to 16 dB. higher than that recorded in vaults and horizontal noise was 4 to 22 dB. higher. Across all posthole installations, as compared to Peterson’s Low Noise Model, vertical and horizontal noise at 100 seconds averaged 27 and 45 dB. higher, respectively. Sites should be located directly on bedrock, where possible. If this is not possible, they should be in well compacted inorganic soil with a low moisture content. Immediately after installation at a potential site, a noise sample should be analyzed in the field to test the suitability of the site. / Master of Science

by Lawal Mohammed Marafa. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (p. 216-234). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Copy of author's published article inserted. / Bibliography: leaves 191-202. / xix, 202 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / A limitation of the geostatistical approach to spatial modelling of soil properties was redressed by adopting a continuum approach to soil classification. This involved the use of the fuzzy-c-means algorithm, to quantify pedons into intragrade and extragrade classes by minimization of the objective functional for the most "precise" classification. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1991

A study of soil variability was performed on an 87 hectare area within a uniform mapping unit--Pima Clay loam-- at The University of Arizona Branch Experiment Station at Marana. The primary interest was with respect to soilwater parameters. From 36 sites selected by an unbalanced three-stage nested design, 180 core samples were collected at 30 cm depth intervals to 150 cm. In addition, 500 bulk samples were taken at the 60 cm depth on an equally spaced grid over a secondary sampling area of 96 by 76 meters. The measured parameters showed different patterns of spatial variation. For example, to estimate means within 10% for the 30 cm depth 5, 51, and 1,011 samples would be needed for bulk density, the porosity index, and the saturated hydraulic conductivity, respectively (using the 0.05 level of significance). Most of the other estimates for number of samples required were in a range of 50 to 100. Most coefficients of variation were between 10 and 50% with bulk density lower and saturated hydraulic conductivity higher. Variance components for the three stages obtained from the analysis of variance revealed that the variation among fields was smaller than within fields and sections for the majority of the measured parameters, their average relative contribution to the total variance being 25, 44, and 31%, respectively. Values of 15-bar moisture retention corresponding to the 500 bulk samples showed a frequency distribution close to the normal with a slight tendency toward skewness. Values of bulk density were normally distributed at each depth and on the combined 180 samples. The highly skewed distributed values of the saturated hydraulic conductivity proved to be normally distributed after a logarithmic transformation. The porosity index showed a nonconsistent distribution pattern at the different depths and a moderately skewed frequency distribution for the composite 180 samples. Close relationships were found between bulk density and per cent sand and silt. A highly significant correlation (significant at th 0.01 level) between 15-bar water retention and clay content existed. Values of the logarithm of the hydraulic conductivity showed a high degree of correlation with values of per cent pores drained at 50 millibars (correlation coefficients of high absolute values and significant at the 0.01 level). Particle size distribution exhibited a decrease of silt and clay and a corresponding increase of sand with depth. The average percentages of sand, silt, and clay at 30 cm depth were 23.3, 41.2, and 35.3, and at the 150 cm depth were 39.7, 35.6, and 24.7, respectively. A similar trend was revealed for bulk density which ranged from 1.42 at 30 cm depth to 1.57 g/cm³ at the 150 cm depth. Soil moisture release curves for each depth showed similar general shapes. The "porosity index" describing the moisture release curve in the low pressure range varied from 3.58 at 30 cm depth to 5.79 at the 150 cm depth. Mean values of the saturated hydraulic conductivity also tended to increase with depth--1.71 and 7.03 cm/hr at 30 and 150 cm depth, respectively. Comparison between the sampling scheme used and three-stage balanced designs revealed that at least two alternatives would be more effective in decreasing the variance of the mean, but they do not provide any degrees of freedom for the third stage. An apparent compromise was found to exist between the scheme used and the optimum unbalanced designs selected for efficient estimation of variance components for the majority of the measured parameters.

The understanding of the spatial distribution of lead (Pb) in soil is important in the assessment of potential risks and development of remediation strategies for Pb contaminated land. In situ heterogeneity of Pb was measured at two heavily contaminated sites in the United Kingdom using the Portable X-ray Fluorescence Spectrometer (P-XRF) over a range of spatial scales (0.02 to 50 m). The pattern of the distribution of Pb was very variable, and when expressed as heterogeneity factor (HF), it ranged from 1.2 to 3.2 (highly heterogeneous). The effect of such Pb heterogeneity on plant uptake was investigated in greenhouse pot trials. Two earlier pot trials, which assessed the effect of Pb in a fixed concentration (1000 mg/kg) and in a range of concentration (100 to 10000 mg/kg) found a significant effect of the Pb added treatments, when compared to a control treatment (0 mg/kg Pb added). Biomass and uptake varied by 20 to 100% within and between 16 species/varieties. Results enhanced the selection of two species (Brassica napus and Brassica juncea) for further pot trials. A third pot experiment with Brassica napus and Brassica juncea in simplistic binary model of heterogeneity found 20 to 60% lower uptake in the binary treatment, than homogeneous the treatment. Biomass was higher by 10 to 50% in Brassica juncea and 20 to 40% lower for B. napus in the bianary treatment, when compared to the homogeneous and control treatments. The effect of a more realistic in situ heterogeneity on plant uptake was investigated in a further pot trial, which simulated low (LH), medium) (MH) and high (HH) heterogeneity treatments, compared to a homogeneous (HO) treatment. It detected a significant (P < 0.05) impact of heterogeneity on biomass and uptake between treatments and species. Four to five fold lower biomass were recorded in HH treatment, when compared to the HO treatment. Shoot and root uptake in (mg/kg) concentration increased with increasing heterogeneity with peak uptake (twice as high as HO treatment) in LH for B. napus and in HH and MH treatments for B. juncea respectively. Shoot and root Pb masses in (μg) were maximum in HO and MH treatments respectively with 50 to 70% lower Pb mass in the HH treatment. Results showed that response to heterogeneity is species specific. A sub-experiment explored the behaviour of plant roots in HH treatment and found 20 to 80% variation in root biomass between concentric patches with same nominal soil Pb concentrations. This provided insights into varied responses of these species to realistic Pb heterogeneity. The research demonstrated that the presence and extent of in situ heterogeneity of Pb in soil plays an important role in Pb uptake by plants. It also showed that the homogeneous and simplistic binary model of heterogeneity do not give reliable estimates of plant growth and Pb uptake in realistic field conditions. This work has implications for improving the efficiency of phytoremediation of Pb contaminated land, phytomining, reliability of risk assessment and models of human exposure to Pb.

Heterogeneity of contaminants in soils can vary spatially over a range of scales, causing uncertainty in environmental measurements of contaminant concentrations. Sampling designs may aim to reduce the impact of on-site heterogeneity, by using composite sampling, increased sample mass and off-site homogenisation, yet they could overlook the small scale heterogeneity that can have significant implications for plant uptake of contaminants. Moreover, composite sampling and homogenisation may not be relevant to target receptor behaviour, e.g. plants, and studies, using simplistic models of heterogeneity have shown that it can significantly impact plant uptake of contaminants. The alternative approach, to accept and quantify heterogeneity, requires further exploration as contaminant heterogeneity is inevitable within soils and its quantification should enable improved reliability in risk assessment and understanding variability in plant contaminant uptake. This thesis reports the development of a new sampling design, to characterise and quantify contaminant heterogeneity at scales, from 0.02m to 20m, using in situ measurement techniques, and 0.005m to 0.0005m, using ex situ techniques. The design was implemented at two contaminated land sites, with contrasting heterogeneity based upon historic anthropogenic activity and showed heterogeneity varying between contaminants and at different spatial scales, for Pb, Cu and Zn. Secondly, this research demonstrates how contaminant heterogeneity measured in situ can be recreated in a pot experiment, at a scale specific to the plant under study. Results, from 4 different plant species, demonstrated that existing simplistic models of heterogeneity are an inadequate proxy for plant performance and contaminant uptake under field conditions, and significant differences were found in plant contaminant concentrations between simplistic models and those based upon actual site measurements of heterogeneity. Implications of heterogeneity on plant roots were explored in the final experiment showing significant differences in root biomass between patches of differing contaminant concentrations.

Thesis (M.S.)--Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.

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