Analysis of geological structure and anthropological factors affecting arsenic distribution in the Lahore aquifer,Pakistan

This study investigated the potential factors affecting arsenic concentration in the groundwater system of Lahore, Pakistan. The effects of several factors such as population density (PD), pumping rate (PR), impermeable land use (LU), surface elevation (SE), and water-table elevation (WL) on arsenic concentration were studied in 101 union councils of Lahore. Forty single and multi-factor models were established using geographic information system (GIS) techniques to develop an arsenic contamination map and to investigate the most effective combinations among factors. Additionally, statistical tests were used to evaluate arsenic concentration between classes of the same single factor. The arsenic concentration in the Lahore aquifer varied from 0.001 to 0.143 mg L^?1. The highest arsenic concentrations were detected in the Walled City and the town of Shahdara. Among the 40 raster models, groundwater arsenic concentration showed the best matching frequency with single-factor models for PD (50.70 %) and SE (47 %). Thus, PD and SE were used to develop an arsenic distribution raster map, and they were also used to study the effect of aquifer depth on arsenic concentration. PD was found to have hidden latent variables such as PR and LU. The shallow aquifer depth was negatively correlated with arsenic concentration (r?=??0.23) and positively with PR (r?=?0.15). Therefore, when there was high PR in wells with smaller aquifer depth, the arsenic concentration was high. The existing water treatment and alternative water resources are good options, which should be developed to deal with Lahore wells contaminated with arsenic at high concentrations.     

Rockfall susceptibility zoning based on back analysis of rockfall deposit inventory in Gunung Kelir,Java

A rockfall susceptibility based on trajectory-energy/velocity approach needs release area or rockfall source. However, identification of rockfall source is not always possible for some areas in Indonesia. This paper presents a rockfall susceptibility zoning based on back analysis technique of rockfall deposit inventory in Gunung Kelir, Java. There were several steps in the rockfall susceptibility zoning: (1) rockfall deposit inventory, (2) rockfall simulation based on back analysis of rockfall deposit inventory, (3) sensitivity analysis, and (4) rockfall susceptibility zoning. The result suggests that the travel distance is affected by the spatial distribution of rockfall source, lithology or surface material, and topography (angle of slope and angle of aspect). Final trajectories were employed to generate landslide susceptibility map which may allow a policy maker to have an advanced consideration to achieve specified risk measures and evaluation of their cost efficiency to optimize budget and design. Application of rockfall susceptibility zoning based on back analysis of rockfall deposits is efficient where rockfall source information is unavailable.     

The variances of tidal harmonics

Summary The variances, or squared standard errors, of estimates of tidal harmonic constants from analyses of a month or a year of tide-gauge data are analysed in terms of spectral properties of their noise continuum, modelled as exponential cuspsE ₁ superimposed on a smoothly monotonic non-tidal spectrumE ₀. Taking 5 representative stations, each with 19 years of data,E ₀ is evaluated from the inter-species noise levels, andE ₁ from the ratio of the variances from monthly and yearly analyses. It is shown that the cusps surrounding the diurnal tides are dominated byE ₀, whereas the more important semi-diurnal and higher species cusps are fitted by an exponential form forE ₁ with bandwidth of a few cycles per year. The variance ratios (monthly: yearly analyses) for diurnal harmonics are somewhat greater than the value expected for white noise, partly because of residual tidal lines in the monthly analyses which cannot be related to the major constituents. The corresponding ratios for semi-diurnal and higher species harmonics are less than the white noise value, on account of the cusps. The standard errors of yearly estimates of the larger tidal constituents may be predicted as proportional to their mean amplitude, as a very rough guide, in the approximate ratio of 11 mm/m.Zusammenfassung Die Varianzen — oder Quadrate der Standardabweichungen — der Abschätzungen von harmonischen Gezeitenkonstanten aus Analysen monatlicher bzw. jährlicher Pegelbeobachtungsreihen werden nach den spektralen Eigenschaften ihres Rauschens analysiert. Dieses wird durch exponentielle SpitzenE ₁, die einem glatten monotonen NichtgezeitenspektrumE ₀ überlagert sind, dargestellt. Anhand 19 jähriger Beobachtungsreihen von 5 repräsentativen Stationen wirdE ₀ aus dem Hintergrundrauschen ermittelt undE ₁ aus dem Verhältnis der Varianzen aus monatlichen und jährlichen Analysen. Es wird gezeigt, daß die Spitzen im Bereich der eintägigen Tiden vonE ₀ beherrscht werden, die wichtigeren Spitzen der halbtägigen Tiden und der Tiden höherer Ordnung werden dagegen durch einen exponentiellen Ausdruck fürE ₁ mit einer Bandbreite von einigen Perioden pro Jahr angenähert. Die Verhältnisse der Varianzen (aus monatlichen zu jährlichen Analysen) für eintägige Harmonische sind etwas größer als der Wert, den man für weißes Rauschen erwarten würde, zum Teil deshalb, weil bei monatlichen Analysen nicht alle Tiden den Hauptkomponenten zugeordnet werden können. Die entsprechenden Verhältnisse für halbtägige und höhere Harmonische sind wegen der Spitzen kleiner als der Wert für weißes Rauschen. Die Standardabweichungen der jährlichen Abschätzungen größerer Gezeitenkomponenten können grob als proportional zu ihrer mittleren Amplitude geschätzt werden mit einem Verhältnis von etwa 11 mm/m.

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Varianzen harmonischer Gezeitenkonstanten

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Les variances des constantes harmoniques de marée

Résumé Les variances, ou carrés des écarts types, des estimations de constantes harmoniques de marée provenant d'analyses portant sur un mois ou une année de données marégraphiques sont analysées en terme de propriétés spectrales de leur continuum de bruit, modélisé comme des pics exponentielsE ₁ superposés à un spectre ne provenant pas de la marée sensiblement monotoneE ₀. Si l'on prend 5 stations représentatives, chacune comportant 19 années d'observations,E ₀ est évalué par les niveaux de bruit inter-espèces, etE ₁ par le rapport des variances provenant des analyses mensuelles et annuelles. On montre que les pics entourant les marées de type diurne sont dominés parE ₀, alors que les pics plus importants de type semidiurne et d'espèces supérieures sont bien approximés par une forme exponentielle pourE ₁ avec une largeur de bande de quelques cycles par an. Les rapports de variance (analyses mensuelles/annuelles) des harmoniques diurnes sont un peu plus grands que la valeur attendue pour le bruit blanc, partiellement à cause des composantes de marée résiduelles dans les analyses mensuelles qui ne peuvent pas être rattachées aux composantes majeures. En raison des pics, les rapports correspondants pour les harmoniques des espèces supérieures et semi-diurnes sont inférieures à la valeur du bruit blanc. Les écarts types des valeurs estimées annuelles des composantes principales de marée peuvent être définis grossièrement comme proportionnels à leur amplitude moyenne, en admettant un rapport de proportionnalité approximatif de 11 mm/m.

     

Engineering properties of sabkha soils in the benghazi plain and construction problems

This paper describes the geological, geotechnical and chemical properties of some Sabkha (lagoonal) soils in the Benghazi plain. Several buildings constructed on such soils show tilting and cracks. The cause of this trouble has been traced to the special characteristics of Sabkha soils. It is suggested that improved mix design and dense concrete should be used so as to make concrete in the foundation impermeable.     

Geo-temporal Twitter demographics

This paper seeks and uses highly disaggregate social media sources to characterize Greater London in terms of flows of people with modelled individual characteristics, as well as conventional measures of land use morphology and night-time residence. We conduct three analyses. First, we use the Shannon Entropy measure to characterize the geography of information creation across the city. Second, we create a geo-temporal demographic classification of Twitter users in London. Third, we begin to use Twitter data to characterize the links between different locations across the city. We see all three elements as data rich, highly disaggregate geo-temporal analysis of urban form and function, albeit one that pertains to no clearly defined population. Our conclusions reflect upon this severe shortcoming in analysis using social media data, and its implications for progressing our understanding of socio-spatial distributions within cities.