The solubility of iron sulphides in synthetic and natural waters at ambient temperature

A critical evaluation of literature values for the solubility products, K _sp ^NBS = [Fe²⁺][HS^–] Fe²⁺ HS^– (H _NBS ⁺ )^–1, of various iron sulphide phases results in consensus values for the pKs of 2.95 ± 0.1 for amorphous ferrous sulphide, 3.6 ± 0.2 for mackinawite, 4.4 ± 0.1 for greigite, 5.1 ± 0.1 for pyrrhotite, 5.25 ± 0.2 for troilite and 16.4 ± 1.2 for pyrite.Where the analogous ion activity products have been measured in anoxic freshwaters in which there is evidence for the presence of solid phase FeS, the values lie within the range of 2.6–3.22, indicating that amorphous iron sulphide is the controlling phase. The single value for a groundwater of 2.65 (2.98 considering carbonate complexation) agrees. In seawater four values range between 3.85 to 4.2, indicating that mackinawite or greigite may be the controlling phase. The single low value of 2.94 is in a situation where particularly high fluxes of Fe (II) and S (–II) may result in the preferential precipitation of amorphous iron sulphide. Formation of framboidal pyrite in these sulphidic environments may occur in micro-niches and does not appear to influence bulk concentrations. Calculations show that the formation of Fe₂S₂ species probably accounts for very little of the iron or sulphide in most natural waters. Previously reported stability constants for the formation of Fe (HS)₂ and (Fe (HS)₃)^– are shown to be suspect, and these species are also thought to be negligible in natural waters. In completely anoxic pore waters polysulphides also have a negligible effect on speciation, but in tidal sediments they may reach appreciable concentrations and lead to the direct formation of pyrite. Concentrations of iron and sulphide in pore waters can be controlled by the more soluble iron sulphide phase. The change in the IAP with depth within the sediment may reflect ageing of the solid phase or a greater flux of Fe (II) and S (–II) nearer the sediment surface. This possible kinetic influence on the value of IAPs has implications for their use in geochemical studies involving phase formation.     

焦作-郑州天然气输气管道工程地质灾害防治措施及防治建议

焦作-郑州天然气输气管道是较重要建设项目,输气管道起自焦作市博爱县磨头镇,南止郑州市惠济区古荥镇,该输气管道沿线地质环境条件复杂程度为简单-中等。地质灾害类型主要为崩塌、地裂缝、地面不均匀沉陷,黄土湿陷和沙土液化等地质灾害。工程建设有引发和加剧崩塌灾害的可能性,有遭受地质灾害的危险性。工程建设过程中应针对不同的灾害类型采取适当的预防或治理措施。     

饱和软土压缩曲线的“反常”现象

饱和软土压缩试验时,经常出现压缩曲线“反常”、压缩系数“倒大”的现象。它是土的原始结构发生破坏前后的不同压缩性的客观反映。饱和软土的结构力很微弱,唯质量好的原状土才能见到这种“反常”。应从成孔、取样、测试及资料整理等多个环节保证其工程意义。     

Mesoproterozoic diamondiferous ultramafic pipes at Majhgawan and Hinota, Panna area, central India: Key to the nature of sub-continental lithospheric mantle beneath the Vindhyan basin

Amongst all the perceptible igneous manifestations (volcanic tuffs and agglomerates, minor rhyolitic flows and andesites, dolerite dykes and sills near the basin margins, etc.) in the Vindhyan basin, the two Mesoproterozoic diamondiferous ultramafic pipes intruding the Kaimur Group of sediments at Majhgawan and Hinota in the Panna area are not only the most conspicuous but also well-known and have relatively deeper mantle origin. Hence, these pipes constitute the only yet available ‘direct’ mantle samples from this region and their petrology, geochemistry and isotope systematics are of profound significance in understanding the nature of the sub-continental lithospheric mantle beneath the Vindhyan basin. Their emplacement age (∼ 1100 Ma) also constitutes the only reliable minimum age constrain on the Lower Vindhyan Group of rocks. The Majhgawan and Hinota pipes share the petrological, geochemical and isotope characteristics of kimberlite, orangeite (Group II kimberlite) and lamproite and hence are recognised as belonging to a ‘transitional kimberlite-orangeite-lamproite’ rock type. The namemajhagwanite has been proposed by this author to distinguish them from other primary diamond source rocks. The parent magma of the Majhgawan and Hinota pipes is envisaged to have been derived by very small (<1%) degrees of partial melting of a phlogopite-garnet lherzolite source (rich in titanium and barium) that has been previously subjected to an episode of initial depletion (extensive melting during continent formation) and subsequent metasomatism (enrichment). There is absence of any subduction-related characteristics, such as large negative anomalies at Ta and Nb, and therefore, the source enrichment (metasomatism) of both these pipes is attributed to the volatile- and K-rich, extremely low-viscosity melts that leak continuously to semi-continuously from the asthenosphere and accumulate in the overlying lithosphere. Lithospheric/crustal extension, rather than decompression melting induced by a mantle plume, is favoured as the cause of melting of the source regions of Majhgawan and Hinota pipes. This paper is a review of the critical evaluation of the published work on these pipes based on contemporary knowledge derived from similar occurrences elsewhere.     

金属腐蚀探测

本阐述了金属腐蚀的危害性和金属管道腐蚀探测的迫切性，并介绍了几种具有探测腐蚀功能的物探方法。     

基于自然水系网信息的元素运移分析

地面上的矿物或污染物元素主要是随水系而运移的。因此，利用自然水系网信息来定量分析元素沿水系的迁移、分散，对于地质找矿和环境保护都具有重要意义。在研究应用主概率权模拟模型产生自然水系网的基础上，提出了元素在水系网中运移的计算方法，结合所模拟出的水系网，具体分析了元素在其中的迁移、扩散情况，给出了正问题和反问题的计算结果。结果表明，正、反问题的求解具有一致性，方法是有效、可行的。     

浅谈环境地质与环境保护

环境问题已成为全世界共同关心的问题。地质环境是影响人类生存的重要因素。本文述及了因自然地质因素引起的地震灾害、火山灾害、滑坡灾害等，以及因人为地质因素引发的水污染灾害、水库失事灾害、水土流失、沙漠扩大灾害等诸方面内容，指出在今后应重视对地质灾害的监测和预防。