首钢工业区土壤剖面重金属含量及其结合态的磁指示作用的研究

对取自首都钢铁厂附近的土壤样芯进行了重金属含量、形态分析和的磁学测量.探讨了利用磁参数追踪和指示重金属污染和有机结合态和铁锰氧化结合态重金属的可行性.结果表明:土壤样芯中Cu、Pb、Zn、Fe和Mn的含量与χ、SIRM和ARM存在着十分相似的垂向变化特征,且相关关系显著(0.98>R>0.86).进一步对磁化率和Cu、Pb、Zn、Fe和Mn各结合态进行相关分析表明:五种元素的有机结合态与铁锰结合态和磁化率呈显著相关关系(0.98>R>0.56),而交换态和残渣态重金属与磁化率基本不存在相关关系.反映了磁性矿物和和重金属在赋存状态的本质联系.表明了磁性测量可作为工业区土壤重金属污染及有机结合态与铁锰结合态重金属记录信息提取的辅助手段.     

Development of Emission Models and Improvement of Emission Data for Germany

Measurements and model developments with the objective to improve the quality and resolution of estimations of anthropogenic emissions are described. Measurement results on a chassis dynamometer were used to determine VOC profiles for exhaust gas emissions of passenger cars for different vehicle and fuel types and different driving modes. Further measurements resulted in emission factors and VOC profiles for lignite burning in residential stoves. Using remote sensing techniques benzene emission factors of gas stations and the efficiency of gasoline vapour recovery systems were measured.To improve the quality and the spatial and temporal resolution of emission data, emission models were improved or modified. This was done by elaborating and applying new methods for important emission source categories (e.g., solvent use, road traffic, small combustion) as well as including new data sources in the calculation routines (e.g. emission statements, land use data, import/export indices of solvents). Simultaneously considerable progress was made improving temporal and spatial allocation functions and VOC profiles. With these improvements a large number of anthropogenic emission data sets for 14 different grid projections in Germany and Europe have been generated. An emission scenario for Germany for 2010 suggests that considering air quality directives from the EU and Germany which are in force or in pipeline, German emissions of VOC and NO_x will decrease, but still exceed the national emission ceilings of the EU-NEC directive.     

An Inter-Laboratory Assessment of the Thorium Isotopic Composition of Synthetic and Rock Reference Materials

We present a concerted international effort to cross-calibrate five synthetic Th isotope reference materials (UCSC Th "A", OU Th "U", WUN, IRMM-35 and IRMM-36), and six rock reference materials (UCSC TML, Icelandic ATHO, USGS BCR-2, USGS W-2, USGS BHVO-2, LV18) using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). We then compare our new values with a compilation of literature mass spectrometric data for these reference materials and derive recommended "consensus"²³⁰Th/²³²Th values for each. We also present isotope dilution U and Th concentration data for four rock reference materials (UCSC TML, Icelandic ATHO, USGS BCR-2, USGS W-2).     

The Hoher List observations of the occultation of 28 Sagittarii by Titan

Observations of the occultation of 28 Sgr by Titan are presented. Apparently being located close to the central line of the occultation track, a double peaked central flash was observed. Some characteristic times of the phenomenon are given.     

Causes of sinks near Tucson, Arizona, USA

 Land subsidence in the form of sinks has occurred on and near farmlands near Tucson, Pima County, Arizona, USA. The sinks occur in alluvial deposits along the flood plain of the Santa Cruz River, and have made farmlands dangerous and unsuitable for farming. More than 1700 sinks are confined to the flood plain of the Santa Cruz River and are grouped along two north-northwestward-trending bands that are approximately parallel to the river and other flood-plain drainages. An estimated 17,000 m³ of sediment have been removed in the formation of the sinks. Thirteen trenches were dug to depths of 4–6 m to characterize near-surface sediments in sink and nonsink areas. Sediments below about 2 m included a large percentage of dispersive clays in sink areas. Sediments in nonsink areas contain a large component of medium- to coarse-grained, moderately to well sorted sand that probably fills a paleochannel. Electromagnetic surveys support the association of silts and clays in sink areas that are highly electrically conductive relative to sand in nonsink areas. Sinks probably are caused by the near-surface process of subsurface erosion of dispersive sediments along pre-existing cracks in predominantly silt and clay sediments. The pre-existing cracks probably result from desiccation or tension that developed during periods of water-table decline and channel incision during the past 100 years or in earlier periods. Submitted, April 1997 · Revised, November 1997 · Accepted, April 1998     

Forecasting models to quantify three anthropogenic stresses on coral reefs from marine recreation: anchor damage, diver contact and copper emission from antifouling paint

This research focuses on damage to coral reefs from three anthropogenic stresses: the dropping of anchors and their chains, human contact, and emission of copper from antifouling paints. Forecasting models are described that quantify degradation in terms of percentage of coral cover damaged/year or increasing levels of water toxicity/year. The models utilize a Monte Carlo simulation that applies a range of values or a probability distribution to each of the numerous uncertain variables. This model has the flexibility to adapt, and become more accurate, when users input assumptions specific to their diving sites. Given our specific assumptions for a frequently visited site, anchors and their chains forecast a distribution of coral reef cover damage with a mean of 7.11%+/-4.77%, diver contact forecast a distribution of coral reef cover damage with a mean of 0.67%+/-0.38%, and antifouling paint forecast a distribution of copper level increase in the water with a mean of 0.037+/-0.014ppb. The results support recommendations for the implementation and sustained use of several specific marine recreation practices.     

The stabilisation of wet sediment cores by means of a polyethylene glycol/freeze-drying treatment for display and permanent storage

A reversible method is presented to transform waterlogged sediment cores into dry and stable specimens which can go on exhibition or into permanent storage, needing no special precautions. Wet sediment core segments are bath-impregnated with polyethylene glycol of molecular weight 3,350 (PEG 3,350) dissolved in water. The samples are then subjected to a freeze-drying process, during which the PEG forms a stabilising and bonding porous network structure in the capillary system of the sediment. Standard sediment cores at least 1 m long become strong enough to stand upright. Sediment types ranging from muddy deep-sea sediments to very coarse littoral Halimeda sand were successfully stabilised. For standard cores of 10-cm diameters split length-wise, impregnation times vary from 2 weeks for coarse sand to 6–10 weeks for more compacted sediments. With regard to the stability of the samples and the visual clarity of detail, best results were obtained by impregnation with 25 to 60% solutions of PEG 3,350, coarse sediments needing more PEG than finer ones. Colour changes are systematic – the processed samples are lighter in appearance and the contrasts are enhanced, but there is no serious shift in colour tones. The PEG can easily be re-dissolved and washed out of the sediments. Display specimens can thus be made available for research again.     

Extended structures around yso in Mid-IR broad emission features

We present CO(1-0) observations toward the soft gamma-ray repeater SGR 1806-20. We discuss the implications on the distance to the X-ray counterpart: AX 1805.7-2025. We also present an upper limit at = 1.3 mm for the thermal emission from dust and high resolution IRAS maps of the region. SGR 1806-20 is very likely associated with the H II complex W31. The G10.0-0.3 supernova remnant (SNR) could be expanding in the very low density region produced by the wind of the bright O9-B2 star recently detected.National Academy of Sciences / National Research Council Resident Research Associate     

Assessment of USGS BCR-2 as a Reference Material for Silicate Rock U-Pa Disequilibrium Measurements

The accuracy of ²³¹Pa-²³⁵U measurements can be readily assessed using a secular equilibrium reference material (RM), but a secular equilibrium RM is also required to calibrate the ²³³Pa spike used in ²³¹Pa determinations. The only silicate RM commonly accepted to be in secular equilibrium is Table Mountain Latite (TML) and so an additional reference is required. Our measurements on the widely available USGS BCR-2 (Basalt Columbia River) rock powder yielded (²³¹Pa/²³⁵U) = 0.997 ± 0.013 2s (n = 10), indicating its value as a secondary reference to test the fidelity of U-Pa determinations. Such a reference material additionally provides a useful check on data reduction, which our literature survey highlights can lead to discrepancies of up to 53% between reported (²³¹Pa/²³⁵U) activity ratios and corresponding U and Pa concentration data.