Application of the geographical information systems approach to watershed mass balance studies

This study was undertaken to test the utility of a geographical information systems (GIS) approach to problems of watershed mass balance. This approach proved most useful in exploring the effects that watershed scale, lithology and land use have on chemical weathering rates, and in assessing whether mass balance calculations could be applied to large multilithological watersheds. Water quality data from 52 stations were retrieved from STORET and a complete GIS database consisting of the watershed divide, lithology and land use was compiled for each station. Water quality data were also obtained from 7 experimental watersheds to develop a methodology to estimate annual fluxes from incomplete data sets. The methodology consists of preparing a composite of daily flux data, calculating a best fit sinusoid and integrating the equation to obtain an annual flux. Comparison with annual fluxes calculated from high resolution data sets suggests that this method predicts fluxes within about 10% of the true annual flux. Annual magnesium fluxes (moles km⁻² yr⁻¹) were calculated for all stations and adjusted for fluxes from atmospheric deposition. Magnesium flux was found to be a strong function of the amount of carbonate in the watershed, and silica fluxes were found to increase with the fraction of sandstone present in the watershed. All fluxes were strongly influenced by mining practices, with magnesium fluxes from affected watersheds being 6–10 times higher than fluxes from comparable pristine watersheds. Mining practices enhance chemical weathering by increasing the surface area of unweathered rock to which water has access and by increasing acidity and rate of mineral weathering. Fluxes were also found to increase with watershed size. This scale dependence is most likely caused by the sensitivity of weathering fluxes to even minor quantities of carbonates, which are likely to be found in all lithologies at larger scales. Mass balances were carried out in watersheds where gauged sub-watersheds made up more than 95% of the area. The calculations show large magnesium flux and water balance discrepancies. These errors may be a result of significant groundwater inputs to streams between gauges. The results suggest that improvements in how we measure discharge and estimate fluxes may be required before we can apply mass balance techniques to larger scales. © 1997 John Wiley & Sons, Ltd.     

Comparison of methods for calculating annual solute exports from six forested appalachian watersheds

Six methods were compared for calculating annual stream exports of sulfate, nitrate, calcium, magnesium and aluminum from six small Appalachian watersheds. Approximately 250–400 stream samples and concurrent stream flow measurements were collected during baseflows and storm flows for the 1989 water year at five Pennsylvania watersheds and during the 1989–1992 water years at a West Virginia watershed. Continuous stream flow records were also collected at each watershed. Solute exports were calculated from the complete data set using six different scenarios ranging from instantaneous monthly measurements of stream chemistry and stream flow, to intensive monitoring of storm flow events and multiple regression equations. The results for five of the methods were compared with the regression method because statistically significant models were developed and the regression equations allowed for prediction of solute concentrations during unsampled storm flows. Results indicated that continuous stream flow measurement was critical to producing exports within 10% of regression estimates. For solutes whose concentrations were not correlated strongly with stream flow, weekly grab samples combined with continuous records of stream flow were sufficient to produce export estimates within 10% of the regression method. For solutes whose concentrations were correlated strongly with stream flow, more intensive sampling during storm flows or the use of multiple regression equations were the most appropriate methods, especially for watersheds where stream flows changed most quickly. Concentration–stream flow relationships, stream hydrological response, available resources and required level of accuracy of chemical budgets should be considered when choosing a method for calculating solute exports. © 1997 John Wiley & Sons, Ltd.     

Phase stability and kinetics of methane hydrate formation in presence of calcium and magnesium carbonate

The huge amount of methane hydrate deposits identified in deep marine sediments is considered as the new resource for future energy. Since carbonates are one of the major components of marine sediments, in the present study, an investigation has been made to study methane hydrate stability and kinetics in the presence of CaCO₃ and MgCO₃. Effect of the presence of carbonates on the solubility of methane in the system has also been examined as it directly affects the hydrate formation process. It has been observed that in presence of CaCO₃ and MgCO₃, the hydrate formation is inhibited. Comparative studies have also been done in the presence of artificial seawater to consider the effect of presence of different salts. Mole consumption of methane gas during hydrate formation in different carbonate samples was measured using real gas equation and found to be minimum in CaCO₃ in seawater sample due to the combined effect of the presence of CaCO₃ and different salts of seawater. An increase in nucleation and induction time was also observed demonstrating the inhibition of hydrate formation in the presence of these components. Further, the decrease in hydrate formation rate also confirmed the inhibition effect of CaCO₃ and MgCO₃ on hydrate formation.     

俄罗斯贝加尔湖北部 Yoko-Dovyren 层状纯橄岩-橄长岩-辉长岩地块: 结构、成分以及作为矿物原材料的用途

Yoko-Dovyren层状纯橄岩-橄长岩-辉长岩地块位于西伯利亚克拉通南部的一处褶皱构造框架中(俄罗斯贝加尔湖地区北部)。该地块的结构在其厚度最大的中部得到了着重研究。剖面底部主体成分为斜长橄榄岩,并依据内部的堆晶成分变化从下往上可分为五个主要的地层序列:纯橄岩→橄长岩→橄榄辉长岩→橄榄辉长苏长岩→石英辉长苏长岩以及含易变辉石的辉长岩。该地块的矿化包括铜-镍矿化、低硫型富铂族元素(PGE)矿化以及铬铁矿化等。另外,该地块也含多种非金属矿物原材料,如硼矿化、透辉石、各种镁质硅酸盐岩等。它们也包括纯橄岩、异剥橄榄岩和橄长岩,并以较高的品质产出,有望采掘加工成为建筑材料(水泥、混凝土、沥青混凝土和建筑陶瓷)。综合利用矿物原材料可增加矿床价值,并有助于建设环保型采矿工作体系。     

典型海洋大气环境中AZ80镁合金电偶腐蚀行为研究

镁合金作为最轻的金属结构材料,具有比强度高、比刚度高、减震性能好、电磁屏蔽等优点。随着海洋强国战略的实施,先进镁合金结构材料逐步在海洋装备上开始应用。已列装的新型高强AZ80镁合金,通过与QBe1.7铍青铜紧固件连接,共同构成整体在典型海洋大气环境中服役。在高盐、高湿的海洋环境环境中,镁合金与电位更正的QBe1.7铍青铜偶接后,极易发生电偶腐蚀。电位相对更负的高强AZ80镁合金,作为电偶腐蚀的阳极被加速溶解。本研究对高强AZ80镁合金电偶腐蚀样品经过12个月青岛海洋大气暴露试验,发现空白对照组、电偶1组(紧固件铍青铜直径Ψ=10mm)和电偶2组(紧固件铍青铜直径Ψ=20mm)的平均腐蚀速率分别为108.1071、133.8929、173.6250g/(m~2·a)。电偶对表面的主要腐蚀产物为:Mg(OH)_2、MgSO_4和MgCl_2。空白样品、电偶1组和电偶2组平均腐蚀深度分别为:0.175、0.330、0.315mm/a。样品中部腐蚀深度最大,边部腐蚀深度则相对较小。不同样品在青岛试验站的腐蚀产物对基体保护能力的量度(n值)分别为1.1337、1.1378、1.0895,表明随着暴露时间的延长,试样在海洋大气环境中的腐蚀速率会加快,试样表面的腐蚀产物对基体根本起不到保护作用。通过灰色关联分析法,计算了青岛海洋大气腐蚀站点的环境因素与AZ80镁合金腐蚀深度和腐蚀失重之间的关联度,结果表明:青岛海洋大气环境因素对高强AZ80镁合金空白样品腐蚀失重影响前三位分别为:SO_4~(2-)非水溶性硫酸盐转化率;对电偶1组样品影响前三位的环境因素分别为:SO_2硫酸盐转化率NO_2;对电偶2组样品影响前三位的环境因素分别为:水溶性降尘SO_2NH_3。对比电偶对2组和1组,唯一的差别是电偶对的面积比,但决定镁合金腐蚀速度的大气成分完全不同,相关机制会在未来工作中详细研究。     

富马酸根插层镁—铝类水滑石的共沉淀法制备及性质表征

富马酸根插层类水滑石(LDHs)是一种具有较好聚合物相容性和热稳定性等潜在应用价值的多功能复合材料.本文通过密度泛函理论对富马酸根离子静电势和离子尺寸的分析,预测了富马酸根插入LDHs的离子尺寸约为0.802 nm,并从热力学角度说明了富马酸根离子与乙烯、氢自由基加成反应的可能性;以低成本氯化物为原料,采用一步共沉淀法...     

New Extraction System for Lithium from Brine with High Magnesium Content

正Lithium is an important element with a wide variety of applications,especially in lithium ion batteries and in the exploration of nuclear energy.Salt lake brine is the most abundant lithium source available in world,comp-rising70%~80%of all known lithium deposits.Lithium can be abstracted from brines with low magnesium content and processed into kinds of lithium compound in Atacama and Hombre Muerto of South America(Nie et al.,2013).     

Intercalation Assembly and Chemical Product Engineering of Layered Intercalated Functional Materials Based on Efficient Utilization of Magnesium Resources in Salt Lakes

正1 Introduction Magnesium salts are very important by-product of salt lake industry in West China.Nearly 200 million cubic meters of waste brine are released to the environment     

Stability and crystal chemistry of iron-bearing dense hydrous magnesium silicates

Dense hydrous magnesium silicates (DHMS) are supposed to be key phases in planetary water cycles because of their ability to carry water to deep mantle regions in subduction slab environments. In order to understand water cycles in iron-enriched planetary systems such as Mars knowledge of the water content and stability of iron-bearing DHMS is required. Iron-bearing DHMS were synthesized based on two starting compositions, MgFeSiO₄ + 9.5 wt% H₂O system and a simple hydrous Martian mantle composition containing Fe, Mg, Al and Si + 12.35 wt% H₂O (hydrous FMAS system). Compared to literature data on phase D, iron-bearing phase D shows analogous variations in water contents as Mg-phase D but appears to be stable at higher temperatures than Mg-phase D for both starting compositions used in this study. Iron-bearing superhydrous phase B contains up to 7 wt% H₂O and shows an extended thermal stability in the hydrous FMAS system. The high-temperature stability of iron-bearing DHMS with a Mars-like bulk composition indicates that these hydrous phases could host significant amounts of water at core-mantle boundary conditions (1500 °C and 23 GPa) in a hydrous Martian mantle.     

Low flow water chemistry in forested and pasture catchments,Mawheraiti River,Westland

Water samples taken at 19 locations in the Mawheraiti River catchment at weekly intervals during 1979–80 were analysed for sodium, magnesium, potassium, calcium, phosphate, nitrate, and ammonium ion concentrations and for electrical conductivity. Seasonal discharge effects were apparent, and lithology and land management practice also influenced solute concentrations. Solute concentrations were generally very low; nitrate and soluble phosphate were rarely greater than 0.05 mg.L^‐1 and ammonium was rarely greater than 0.01 mg.L^‐1. The 4 major cations (Na, Mg, K, and Ca) usually summed to less than 6 mg.L^‐1 much of which was supplied by precipitation. Forest management (clearfelling and slash‐burning) caused significant increases in solute concentrations, but concentrations declined rapidly during succeeding months and approached pretreatment levels after 2–3 years. The higher concentrations associated with forest management in small experimental catchments were rapidly diluted downstream; together with the low natural solute concentrations this suggests that harmful downstream effects of management practices are unlikely under low flow conditions.