Heterogeneous Chemistry of Nitryl Halides in Relation to Tropospheric Halogen Activation

The heterogeneous chemistry of nitryl chloride and nitryl bromide by salt containing solutions was studied as a function of temperature in the range from 275 to 293 K with the wetted-wall flowtube combined with FTIR and mass spectrometry detection. Uptake coefficients and values of the product Hk^1/2 on these saline solutions have been determined. For nitryl halides interacting with NaI and NaBr solutions, the values of the product Hk^1/2 are respectively 4384.7±326.7 and 103.1±18.7 M atm^-1 s^-1/2 for nitryl chloride at 275 K and 544.2±94.7 and 47.7±15.2 M atm^-1 s^-1/2 for nitryl bromide at 278 K. When reacting with NaI or NaBr solutions, these heterogeneous reactions release, as major products, the molecular forms of the halogen i.e., respectively I₂ and Br₂. A simplified reaction scheme explaining the formation of these products is presented and is inserted into a model simulating the chemistry in the marine boundary layer. The modelling effort showed Cl and BrO atoms concentrations up to 5×10⁴ and 1.8×10⁶ molecules cm^-3 respectively, which are comparable to values actually measured in field campaigns.     

Chemical mass balance of calcrete genesis on the Toledo granite (Spain)

The chemical mass balance of calcrete genesis is studied on a typical sequence developed in granite, in the Toledo mountains, Central Spain.

Field evidence and petrographic observations indicate that the texture and the bulk volume of the parent rock are strictly preserved all along the studied calcrete profile.

Microscopic observations indicate that the calcitization process starts within the saprolite, superimposed on the usual mechanisms of granite weathering: the fresh rock is first weathered to secondary clays, mainly smectites, which are then pseudomorphically replaced by calcite. Based on this evidence, chemical mass transfers are calculated, assuming iso-volume transformation from the parent rock to the calcrete.

The mass balance results show the increasing loss of matter due to weathering of the primary phases, from the saprolite towards the calcrete layers higher in the sequence. Zr, Ti or Th, which are classically considered as immobile during weathering, are also depleted along the profile, especially in the calcrete layer. This results from the prevailing highly alkaline conditions, which could account for the simultaneous precipitation of CaCO₃ and silicate dissolution.

The calculated budget suggests that the elements exported from the weathering profile are provided dominantly by the weathering of plagioclase and biotite. We calculate that 8–42% of the original Ca remains in granitic relics, while only 15% of the authigenic Ca released by weathering is reincorporated in the calcite. This suggests that 373 kg/m² of calcium (i.e., three times the original amount) is imported into the calcrete from allochtonous sources, probably due to aeolian transport from distant limestone formations.     

Structural characterisation of the high-pressure phase CaAl4Si2O11

Single crystals of CaAl₄Si₂O₁₁ were synthesised at 1,500?°C and 14 GPa in a multi-anvil press, and the structure of the phase determined by single-crystal X-ray diffraction at room conditions. The structure-type is that of the “hexagonal barium ferrites”. The space group of the average structure is P6 ₃ /mmc and the cell parameters are a?=?5.4223(4) Å, c?=?12.7041(6) Å, V?=?323.28(5) ų, with Z?=?2, and its density is 3.905?g?cm^?3, which is reasonable for a high-pressure alumino-silicate phase. The 22 oxygen and two calcium atoms within the unit-cell form an approximate hexagonal-close-packed array. Ten of the twelve octahedral interstices within this array that have only oxygen atoms for apices are filled with Si and/or Al. M1 octahedra share edges to form a spinel-like sheet of octahedra. The average bond length ?=?1.833 Å suggests mixed occupancy by Si and Al. The M1 octahedral sheets are linked by shared corners to pairs of face-sharing M2 octahedra containing Al, with ?= 1.918 Å. The remaining two cations of the unit-cell contents statistically occupy four tetrahedrally-coordinated interstices, which occur as face-sharing pairs. The average bond length for these sites (1.742 Å) suggests that they are occupied by Al, although Si occupancy cannot be excluded by the data. It is proposed that only one interstice of each pair is locally occupied, with the possibility of some short-range ordering of such occupancies. Complete long-range order leading to the acentric space group P6 ₃ mc is excluded by the data, as is the possibility of the average structure being comprised of merohedral (0?0?0?1) twins of P6 ₃ mc symmetry.     

跨海地铁盾构管片混凝土耐久性及寿命预测分析

根据某跨海地铁2号线的工况，确定跨海区间盾构管片的环境类别和作用等级，由各原材料氯离子含量计算推荐配合比混凝土氯离子含量，并对推荐配合比混凝土开展氯离子扩散系数试验和抗压强度试验。分别使用《海港工程高性能混凝土质量控制标准》(JTS 257-2—2012)、《混凝土结构耐久性评定标准》(CECS 220：2007)中的评定方法及多因素耦合评价(MFC)方法，基于钢筋开始锈蚀阶段t_i、混凝土保护层锈胀开裂阶段t_c、混凝土功能明显退化阶段t_d对混凝土结构使用年限t_e进行预测。结果表明，以上3种耐久性预测模型预测跨海地铁2号线推荐配合比使用年限的计算结果均大于100年，能够满足使用100年的要求。     

DPQAC-PAC-MC复合改性粘土在不同介质中的絮凝行为研究

改性粘土法絮凝消除浮游微藻是我国迄今唯一得到大规模应用的有害赤潮应急处置方法,研发安全高效的改性粘土材料是该方法发展的重要方向之一.本文研究了双烷基聚氧乙烯基三季铵盐(DPQAC)与聚合氯化铝(PAC)复合改性粘土获得新材料DPQAC-PAC-MC在去离子水、海水及东海原甲藻藻液(Prorocentrum dongha...     

盐田兑卤法提高光卤石矿质量的方法探讨

通过相图分析及计算,介绍了一种"由盐湖卤水兑卤除氯化钠后,首先获得成矿卤水,然后对其蒸发制取质量较好光卤石矿"的生产方法。