Integration of magnetism and heavy metal chemistry of soils to quantify the environmental pollution in Kathmandu, Nepal

Abstract Soil profiles of the Kathmandu urban area exhibit significant variations in magnetic susceptibility (χ) and saturation isothermal remanence (SIRM), which can be used to discriminate environmental pollution. Magnetic susceptibility can be used to delineate soil intervals by depth into normal (< 10^?7 m³/kg), moderately enhanced (10^?7–< 10^?6 m³/kg) and highly enhanced (≥ 10^?6 m³/kg). Soils far from roads and industrial sites commonly fall into the ‘normal’ category. Close to a road corridor, soils at depths of several centimeters have the highest χ, which remains high within the upper 20 cm interval, and decreases with depth through ‘moderately magnetic’ to ‘normal’ at approximately 30–40 cm. Soils in the upper parts of profiles in urban recreational parks have moderate χ. Soil SIRM has three components of distinct median acquisition fields (B_1/2): soft (30–50 mT, magnetite‐like phase), intermediate (120–180 mT, probably maghemite or soft coercivity hematite) and hard (550–600 mT, hematite). Close to the daylight surface, SIRM is dominated by a soft component, implying that urban pollution results in enrichment by a magnetite‐like phase. Atomic absorption spectrometry of soils from several profiles for heavy metals reveals remarkable variability (ratio of maximum to minimum contents) of Cu (16.3), Zn (14.8) and Pb (9.3). At Rani Pokhari, several metals are well correlated with χ, as shown by a linear relationship between the logarithmic values. At Ratna Park, however, both χ and SIRM show significant positive correlation with Zn, Pb and Cu, but poor and even negative correlation with Fe (Mn), Cr, Ni and Co. Such differences result from a variety of geogenic, pedogenic, biogenic and man‐made factors, which vary in time and space. Nevertheless, for soil profiles affected by pollution (basically traffic‐related), χ exhibits a significant linear relationship with a pollution index based on the contents of some urban elements (Cu, Pb, Zn), and therefore it serves as an effective parameter for quantifying the urban pollution.     

Isotopic and molecular composition of coal-bed gas in the Amasra region (Zonguldak basin—western Black Sea)

Previous studies on the coal-bed methane potential of the Zonguldak basin have indicated that the gases are thermogenic and sourced by the coal-bearing Carboniferous units. In this earlier work, the origin of coal-bed gas was only defined according to the molecular composition of gases and to organic geochemical properties of the respective source rocks, since data on isotopic composition of gases were not available. Furthermore, in the western Black Sea region there also exist other source rocks, which may have contributed to the coal-bed gas accumulations. The aim of this study is to determine the origin of coal-bed gas and to try a gas-source rock correlation. For this purpose, the molecular and isotopic compositions of 13 headspace gases from coals and adjacent sediments of two wells in the Amasra region have been analyzed. Total organic carbon (TOC) measurements and Rock-Eval pyrolysis were performed in order to characterize the respective source rocks. Coals and sediments are bearing humic type organic matter, which have hydrogen indices (HI) of up to 300 mgHC/gTOC, indicating a certain content of liptinitic material. The stable carbon isotope ratios (δ¹³C) of the kerogen vary from −23.1 to −27.7‰. Air-free calculated gases contain hydrocarbons up to C₅, carbon dioxide (<1%) and a considerable amount of nitrogen (up to 38%). The gaseous hydrocarbons are dominated by methane (>98%). The stable carbon isotope ratios of methane, ethane and propane are defined as δ¹³C₁: −51.1 to −48.3‰, δ¹³C₂: −37.9 to −25.3‰, δ¹³C₃: −26.0 to −19.2 ‰, respectively. The δD₁ values of methane range from −190 to −178‰. According to its isotopic composition, methane is a mixture, partly generated bacterially, partly thermogenic. Molecular and isotopic composition of the gases and organic geochemical properties of possible source rocks indicate that the thermogenic gas generation took place in coals and organic rich shales of the Westphalian-A Kozlu formation. The bacterial input can be related to a primary bacterial methane generation during Carboniferous and/or to a recent secondary bacterial methane generation. However, some peculiarities of respective isotope values of headspace gases can also be related to the desorption process, which took place by sampling.     

Variability of petroleum inclusions in vein, fossil and vug cements—a geochemical study in the Barrandian Basin (Lower Palaeozoic, Czech Republic)

Although no commercial oil or gas occurrences have been found in the Barrandian Basin, residual oils and petroleum inclusions give evidence about the petroleum history of this Lower Palaeozoic Basin. Petroleum inclusions are hosted in six generations of calcite and quartz cements that can be attributed to different stages of a basinal cycle and associated diagenetic events. They were analysed using an on-line crushing and an off-line crush-and-leach approach. Five different groups (PI-A to PI-E) and intermediate mixtures (PI-M) could be differentiated based on the relative distribution of n-alkanes. All oils had a calculated aromatic maturity R_c ranging between 0.9 and 1.6%. PI-A shows a molecular weight maximum in the range of n-C_8–11 with a constant attenuation towards higher carbon numbered n-alkanes. This distribution is interpreted as the pristine precursor oil for other petroleum inclusion groups. PI-B has a maximum weight abundance at n-C_15–20. The genetic relationship between PI-B and PI-A can tentatively be explained by mixing effects or by gas stripping. PI-C is bimodal and characterised by a molecular weight maximum at n-C_32–34, and also a molecular weight maximum at n-C_15–20 similar to that of group PI-B. PI-D shows a normally distributed molecular weight maximum in the range n-C_25–28 and is interpreted as a wax precipitate from ascending gas saturated in n-alkanes. PI-E contains predominantly gaseous compounds with only a few higher hydrocarbons. Thompson's aromaticity values are elevated for condensates of group PI-E, and also for group PI-C that is dominated by long-chained n-alkanes. This gives evidence that fault-bound petroleum migration in the Barrandian Basin was associated with evaporative fractionation for group PI-C and PI-E. Samples of group PI-E yielded gas-range compounds only, and all come from a last generation of vein-filling whitish calcite that was formed in a late uplift phase of the basin. For other petroleum inclusion groups, only a vague preferential occurrence in specific mineralisation phases or stratigraphic intervals of the host rock has been found. This reflects the predominance of fracture-bound migration in the Barrandian Basin. Aromatic maturity values also showed no correlation between either crystal type or PI-group. In six of the investigated petroleum inclusion samples alk-1-enes are present. These terminal olefins are interpreted to be the result of the natural pyrolysis of petroleum due to the intrusion of volcanic dykes or hydrothermal processes. An artificial generation of olefins during sample work-up and analysis is unlikely. The preservation of alk-1-enes from Palaeozoic times was possible due to the protecting environment of petroleum inclusions.     

Partitioning Between Chlorine Reservoir Species Deduced from Observations in the Arctic Winter Stratosphere

Simultaneous observations of several chlorine source gases, as well asHCl and ClO, have been performed in the Arctic stratosphere on 1 and 9February 1994, using balloon-borne instrumentation as a contribution toSESAME (Second European Stratospheric Arctic and Mid latitude Experiment).The observed mixing ratios of HCl and N₂O show a clearanticorrelation. No severe loss of HCl was observed inside the vortex duringour measurement. These measurements showed that during this period at 20 kmand above, HCl was either in excess, or at least as abundant, asClONO₂ and comprised between 50 and 70% of theavailable chlorine, Cl_y. On 1 February, measurements were madeinside the polar vortex. The air mass sampled on this day showed a clearsignature of diabatic descent, and also enhanced levels of ClO with amaximum of 230 pptv at 22.5 km. A 10 day backward trajectory analysis showedthat these air masses had passed a large region of low temperatures a fewhours prior to the measurement. Temperatures along the back trajectory atthe 475 K and 550 K levels (20.1 and 23.7 km respectively) were cold enoughfor heterogeneous chlorine activation to occur, in agreement with theobserved elevated ClO mixing ratios.     

Geometric methods for estimating representative sidewalk widths applied to Vienna’s streetscape surfaces database

Space, and in particular public space for movement and leisure, is a valuable and scarce resource, especially in today’s growing urban centres. The distribution and absolute amount of urban space—especially the provision of sufficient pedestrian areas, such as sidewalks—is considered crucial for shaping living and mobility options as well as transport choices. Ubiquitous urban data collection and today’s IT capabilities offer new possibilities for providing a relation-preserving overview and for keeping track of infrastructure changes. This paper presents three novel methods for estimating representative sidewalk widths and applies them to the official Viennese streetscape surface database. The first two methods use individual pedestrian area polygons and their geometrical representations of minimum circumscribing and maximum inscribing circles to derive a representative width of these individual surfaces. The third method utilizes aggregated pedestrian areas within the buffered street axis and results in a representative width for the corresponding road axis segment. Results are displayed as city-wide means in a 500 by 500 m grid and spatial autocorrelation based on Moran’s I is studied. We also compare the results between methods as well as to previous research, existing databases and guideline requirements on sidewalk widths. Finally, we discuss possible applications of these methods for monitoring and regression analysis and suggest future methodological improvements for increased accuracy.     

Differential geodetic stereo SAR with TerraSAR-X by exploiting small multi-directional radar reflectors

In this paper, we report on the direct positioning of small multi-directional radar reflectors, so-called octahedrons, with the synthetic aperture radar (SAR) satellite TerraSAR-X. Its highest resolution imaging mode termed staring spotlight enables the use of such octahedron reflectors with a dimension of only half a meter, but still providing backscatter equivalent to 1–2 cm observation error. Four octahedrons were deployed at Wettzell geodetic observatory, and observed by TerraSAR-X with 12 acquisitions in three different geometries. By applying our least squares stereo SAR algorithm already tested with common trihedral corner reflectors (CRs), and introducing a novel differential extension using one octahedron as reference point, the coordinates of the remaining octahedrons were directly retrieved in the International Terrestrial Reference Frame (ITRF). Contrary to our standard processing, the differential approach does not require external corrections for the atmospheric path delays and the geodynamic displacements, rendering it particularly useful for joint geodetic networks employing SAR and GNSS. In this paper, we present and discuss both methods based on results when applying them to the aforementioned Wettzell data set of the octahedrons. The comparison with the independently determined reference coordinates confirms the positioning accuracy with 2–5 cm for the standard approach, and 2–3 cm for the differential processing. Moreover, we present statistical uncertainty estimates of the observations and the positioning solutions, which are additionally provided by our parameter estimation algorithms. The results also include our 1.5 m CR available at Wettzell, and the outcomes clearly demonstrate the advantage of the multi-directional octahedrons over conventional CRs for global positioning applications with SAR.     

Search for extinct Cl: Vigarano CAIs, the Pink Angel from Allende, and a Ningqiang chondrule

We have searched for excesses of ³⁶S derived from the decay of extinct ³⁶Cl in sodalite, a secondary Cl-rich mineral, in Ca-Al-rich inclusions (CAIs) from the Vigarano and Allende CV3 chondrites and in a chondrule from the Ningqiang carbonaceous chondrite. The presence of sodalite in two CAIs from Vigarano and its absence from surrounding CAI fragments suggests sodalite formation after CAI fragmentation. As for sodalite in the Allende Pink Angel CAI, oxygen isotopic compositions have been interpreted as indicative of high temperature interactions, thus suggesting formation prior to accretion to the parent body, probably in a nebular setting. Sodalite in the Ningqiang chondrule is considered to have formed via alkali-Ca exchange, which is believed to have occurred before accretion to the parent body.Sodalites in the Vigarano CAIs and in the Ningqiang chondrule show no clear evidence for the presence of radiogenic ³⁶S. The inferred 2σ upper limits for ³⁶Cl/³⁵Cl at the time of sodalite formation are 1.6 × 10⁻⁶ (Vigarano CAIs) and 3.3 × 10⁻⁶ (Ningqiang chondrule), respectively. In the Pink Angel CAI sodalite exhibits small ³⁶S excesses which weakly correlate with ³⁵Cl/³⁴S ratios. The inferred ³⁶Cl/³⁵Cl ratio of (1.8 ± 2.2) × 10⁻⁶ (2σ error) is lower than that found by Hsu et al. [Hsu, W., Guan, Y., Leshin, L. A., Ushikubo, T. and Wasserburg, G. J. (2006) A late episode of irradiation in the early solar system: Evidence from extinct ³⁶Cl and ²⁶Al in meteorites. Astrophys. J. 640, 525-529], thus indicative of heterogeneous distribution of ³⁶Cl in this CAI. Spallation reactions induced by energetic particles from the young Sun are suggested for the origin of ³⁶Cl, similar to the case of ¹⁰Be. While ¹⁰Be appears to be present in roughly equal abundance in all studied CAIs, our study indicates the level of ³⁶Cl abundances to be variable so that there seems to be no simple relationship between ¹⁰Be and ³⁶Cl. This would be expected if trapped cosmic rays rather than Early Solar System spallation were the dominant source of ¹⁰Be in the Early Solar System, since their contribution to ³⁶Cl would have been tiny.If the variability of ³⁶Cl abundances is caused by temporal differences in the alteration that formed sodalite, sodalite in the Vigarano CAIs and in the Ningqiang chondrule may have formed ?0.5 and ?0.2 Ma after formation of the sodalite in the Ningqiang CAI analyzed by Lin et al. [Lin, Y., Guan, Y., Leshin, L. A., Ouyang, Z. and Wang, D. (2005) Short-lived chlorine-36 in a Ca- and Al-rich inclusion from the Ningqiang carbonaceous chondrite. Proc. Natl. Acad. Sci. USA 102, 1306-1311]. The Pink Angel sodalite that we analyzed may have formed ∼0.3 Ma after formation of the sodalite in the Pink Angel analyzed by Hsu et al. [Hsu, W., Guan, Y., Leshin, L. A., Ushikubo, T. and Wasserburg G. J. (2006) A late episode of irradiation in the early solar system: Evidence from extinct ³⁶Cl and ²⁶Al in meteorites. Astrophys. J. 640, 525-529]. The estimated temporal differences suggest that alteration extended over at least 0.5 Ma. If previous works showing very low initial ³⁶Cl/³⁵Cl in the Allende CAIs and a H3 chondrite CAI are also considered, then alteration processes may have been more than 1.7 Ma.