Development of a thermal desorption method for the analysis of particle associated polycyclic aromatic hydrocarbons in ambient air

An investigation for the analysis of polycyclic aromatic hydrocarbons in airborne particulates using thermal desorption and gas chromatography-mass spectrometry is described. Samples are obtained from ambient air using fibreglass filters and the volatile material from the filter is thermally desorbed to gas chromatograph. A 30 meter capillary column is used to separate the hydrocarbons and eight polyaromatic hydrocarbons are used to test the method and recovery is >95%. The eight polycyclic aromatic hydrocarbons anthracene, phenanthrene, fluoranthrene, pyrene, benzo (a) anthracene, chrysene, benzo (a) pyrene and benzo (e) pyrene were the most abundant PAHs found in the samples of ambient air with current method at Uxbridge-London. Application of the measurement of polycyclic aromatic hydrocarbons in ambient air samples shows that the hydrocarbons trapped in the particle phase to a lesser degree at higher ambient temperature. In conclusion a method has been developed to transfer the PAHs in particle phase from a filter to GC-MS by thermal desorption. A standard mixture of PAHs, when absorbed onto the filter, did lead to strong analyte absorbent interactions by the high percent recovery of the sample.     

Visibility Analysis In Vision Metrology Network Design

The aim of this paper is to present a method whereby accuracy enhancement of an existing photogrammetric network is achieved through the automatic selection of additional camera stations. The determination of the positions of these 'accuracy fulfilment' camera stations is based upon what has been termed 'visibility uncertainty prediction modelling' of visibility constraints derived from the existing network geometry. Following a review of vision constraints in network design, the concepts of visibility uncertainty prediction and visibility uncertainty spheres are introduced. These provide a mechanism to predict the visibility of current object target points for the new accuracy fulfilment images. This in turn aids in network design improvement. The visibility uncertainty modelling is then illustrated for two close range photogrammetric network configurations, for which the test results demonstrate that the proposed model can reliably predict target visibility with an overall certainty of 75%.     

Climatic classification of Saudi Arabia: An application of factor -- Cluster analysis

This study is aimed to be a contribution to climatic regionalization of Saudi Arabia. The study applies a multivariate factor -- cluster analysis technique. The data used here have been obtained from 56 meteorological stations. The application of the technique is made into two stages. In the first stage, factor analysis alone is considered and its results in Saudi Arabia are discussed. In the second stage, the resultant factor scores are taken as an input in a cluster analysis process to obtain climatic regions. Thus the regions obtained in the second stage are a result of the integration of factor and cluster techniques. The results obtained by the technique are compared with those of some traditional methods. The factor-cluster analysis technique is found advantageous over many of those methods, as it produces richer regions and shows clear climate variations within this vast country.     

沉积岩数据库:计算机的应用

岩石学数据在许多地质统计分析中是相当有用的。为了得出焦伊布尔哈德地区的焦因蒂亚布尔区和锡尔赫特地区焦伊布尔哈德灰岩区的构造、地层和沉积作用情况，已作了大量的详细的野外工作和室内分析。已对锡尔赫特地区和焦伊布尔哈德地区的灰岩作了化学分析，且对Ｔｉｐａｍ砂岩作了矿物分析。所获取数据可应用于ＳＥＤＢＡ。用于ＳＥＤＢＡ的参数必须是精确的和沉积成因的。     

Conceptual issues in dealing with land degradation/conservation problems in developing countries

Among experts in the field, there is general agreement that land degradation/conservation is a matter of life or death to hundreds of millions of people. There is general agreement too that in spite of the great efforts being made to combat desertification in the last 10 years, the problem is growing worse every day. On the other hand the technology and know-how to deal with all sorts of land degradation problems is available everywhere in abundance. Why then do we in the developing world, the most affected by the problem, seem handicapped or not able to deal effectively with it? What do we really lack? Do we lack the knowledge, the experience, the money or do we lack the will to live? This paper, while trying to give at least partial answers to all those questions, assumes that the right way of thinking in dealing with resources degradation is the most serious thing we are lacking. With some examples from Egypt and other developing countries, the paper will point to some aspects that may constitute part of the conceptual framework that is required to save our world and to keep the forthcoming disasters at an acceptable level.     

Experimental (clay) models of inversion structures

Experimental modeling is used to study the geometry and evolution of inversion structures. Two main types of inversion structures are analyzed:

1. (1) structures formed by fault-propagation folding; and

2. (2) structures formed by fault-bend folding on listric faults.

Fault-propagation inversion structures initially develop as broad drape folds with possible fault breakthrough during an early extensional phase. Syn-extensional strata deposited in the hanging wall typically thicken away from the fault. Compressional reactivation results in reversal of slip on the master and secondary faults, their rotation to shallower dips, and the development of a compressional fault-propagation fold. Key features of the fault-propagation fold are basinward thickening of syn-extensional units and resulting steep dips of the front limb of the structure. Fault-bend inversion structures initiate as rollover folds within extensional half-graben. Deformation is primarily localized along a system of antithetic faults. Syn-extensional strata typically thicken across the fault but also thin basinward away from the fault. During compression, the extensional rollover folds are folded into compressional fault-bend folds. Key features of this structure are thinning of syn-extensional units into the basin. Inversion of more symmetric graben results in a doubly-convex geometry of syn-extensional units. These observations of bed geometry and thickness provide predictive models for interpreting the geometries of inversion structures in areas of poor data quality.     

Genesis of Disseminated Sulphide Assemblages in Niagara Peninsula,Canada

In the Niagara Peninsula of Southern Ontario, Canada, subeconomic occurrences of Mississippi Valley-type base metal assemblages are found in the petroliferous carbonate units of the Middle Silurian sedimentary succession. These units, which were deposited on the northwestern margin of the Appalachian Basin, were buried by about 2.4 km of Paleozoic sediments up to the time of the Appalachian orogeny. The sulphide minerals form 13 different assemblages and occur in veins, veinlets, vugs and stylolite seams. Distribution of the gangue minerals is irregular but the sulphide minerals display an overlapping vertical zonation. Although dolomite is more abundant in the Lockport Formation, the amount of dolomitization is not directly related to the degree of lead-zinc mineralization. The origin of the assemblages can be explained by a model that relates mineralization to the evolution of the Appalachian Basin. Minor quantities of sphalerite (in chert nodules) and pyrite (as framboids) precipitated during the early diagenetic stage. During later diagenesis, “hot” petroleum-bearing connate waters were expelled from sediments by compaction, and possibly later by the compressive forces of the Appalachian orogeny. As these waters moved outward and upward to zones of lower pressure, they became more saline and separated into liquid petroleum and connate brine phases. Petroleum, due to its lower density, preceded the general outward and upward movement of the connate brines to the basin margins. Here, the Middle Silurian carbonates of the Niagara Peninsula impeded the previous, relatively rapid flow, through the underlying clastics, and were locally enriched in petroleum as it moved into the immediately overlying Upper Silurian reservoirs. This petroleum provided source of reduced sulphur. During their passage, the connate brines probably leached metals from a variety of sediments of differing provenance. These metals precipitated as sulphides on reaching the zone of reduced sulphure. After uplift of the basin, the late Paleozoic strata were eroded and downward-moving meteoric groundwater leached metals, sulphates and carbonates from the host rocks. On reaching the reducing conditions of the water table, sulphides precipitated where the concentration of reduced sulphur was sufficiently high. This process, which is still continuing enables us to propose that many carbonate-hosted Pb-Zn deposits may have been enriched during periods of uplift.     

A change-detection application on the evolution of Kahak playa (South Khorasan province, Iran)

Kahak salt playa in South Khorasan province of Iran, have special geomorphological characteristics by the presence of ephemeral saline lakes, wetlands, salt crusts, surface accumulations of salt and zones of patterned ground. Salt crusts in the soil surface are unique in the region and have laminated horizons in the playa soil. Soil-surface salt accumulations are dominated by NaCl and gypsum. It has been found that distribution of chemical soluble is not uniform across the playa landscape, and this result influences on the variety form of patterned ground. In this study, the percent changes in some of the chemical elements such as NaCl, gypsum and also brine extent have been calculated in the playa. Indicating changes in Kahak salt playa is the main aim of this study by using remote sensing and GIS techniques. In this paper, techniques such as spectral un-mixing, maximum likelihood classification, band rationing, fuzzy classification and correlation relationships are discussed. This contribution presents modeling of temporal and spatial changes of salinity and playa developing using combined approaches that incorporate different data-fusion and data-integration techniques for two periods of date. Furthermore, percent changes in the surface-patterned ground of the playa have been calculated using texture and pattern analysis of the PCA1. Results have revealed that, in the playa developing, chemical materials such as sodium, NaCl, gypsum and also brine extent are positively correlated with each other and the most increased changes are related to gypsum and the most decreased changes are related to the NaCl. Also changes in the amount of agricultural area in the playa-lakes margin, show low effects in the desertification process.