Freshwater macroinvertebrate distribution in two basins with different salinity gradients (Guadalete and Guadaira river basins,south-western Spain)

This work reports the results of one year's sampling of aquatic macroinver-brates in various streams with different salinity gradients. The study area was the headwaters of the rivers Guadaíra and Guadalete, located in the same geographical area in south-western Spain. The most interesting feature of the Guadaíra basin is the natural salinity of its waters due to the abundance of gypsum in its headwaters. Lithologically, the headwaters of the Guadalete basin flow over marls, clay, sandstone and limestone. Salinity values in most streams do not reach 1 mS cm^–1. At least at the levels of salinity found in the Guadaíra basin headwaters, the existence of a well-structured community of macroinvertebrates can be claimed. Of the groups studied, Diptera and Coleoptera showed the highest species richness, being distributed preferentially at the ends of the conductivity spectrum. Groups including taxa inhabiting waters of low salinty and taxa inhabiting waters with high salinity could be reliable indicators of salinity.     

Column abundance and the long-term trend of hydrogen chloride (HCl) above the Jungfraujoch Station

The integrated column amount of hydrogen chloride has been monitored above the International Scientific Station of the Jungfraujoch (Switzerland) during the last 8 years. The results deduced from solar absorption measurements near 3.42 m indicate a secular trend equivalent to (0.75±0.2) % increase per year since 1978, superimposed on a significant short-term variability which can be partly attributed to the tropospheric component of the total HCl burden. Based on an intensified set of measurements carried out over the last three years, a seasonal component in the total content of HCl has been established for the first time, showing a minimum occuring in early winter and a maximum during the spring.     

CO2-driven cation leaching after tropical forest clearing

The objective of this study was to investigate the role of dissolved CO₂ (H₂CO₃*) as a mechanism of cation removal from surface soils under secondary land uses in the tropics. Soil leachate columns were prepared with 0–10 cm soils from mature and secondary forest, and managed pastures, and extracted with H₂CO₃* from deionized water equilibrated with 0%, 0.5%, 1%, and 10% CO₂ (g). Extraction of soil cations slowed over time following an exponential form for the cumulative data. The rate of cation concentration decline varied as a function of CO₂ concentration with the 10% solution resulting in a greater percent decline with extraction volume. Potassium removal from the exchange sites of all soils and for all solutions was nearly complete ranging from 85% to 97% while removals of Mg (31% to 71%) and Ca (12% to 42%) were lower. The asymptotic patterns of cation loss observed in this study suggest that H₂CO₃* acid-driven losses of cations may become self-limiting over time. Other stronger acids from atmospheric deposition or organic sources may serve to perpetuate cation removal, and re-forestation on these cleared lands would certainly re-distribute cations from soils to vegetation.     

高岭土中全硫量快速测定方法

采用碳酸钠一氧化镁半熔融一氯化钡滴定法测定高岭土中的硫含量。试样用碱性熔荆半熔，熔块以水浸取，将转化为硫酸盐后的滤液，以玫瑰红酸钠为指示剂，在pH为5．5．7．0的条件下，用氯化钡标准溶液进行滴定。测定结果的RSD=2．47％（n=5），加标回收率为95．2％-100．3％。改进后的方法已用于高岭土中全硫量的测定，结果与国标重量法相符。     

以苄基三乙基氯化铵为增敏剂催化光度法测定痕量铁

在增敏剂苄基三乙基氯化铵存在下,Fe(Ⅲ)对H2O2氧化溴甲酚绿具有催化作用,据此建立了一种测定痕量Fe(Ⅲ)的新方法。考察该反应的最佳条件,测定反应动力学参数。催化反应的表观活化能Ea为61.14 kJ/mol。方法的检出限为2.8×10-8g/L,线性范围0~600μg/L。用于河水、自来水等样品中铁的测定结果满意,相对标准偏差(RSD,n=6)小于5%。     

低水合氯化镁吸水过程中水蒸气分压计算

对低水合氯化镁的吸水过程进行了初步的探讨,并对低水合氯化镁吸水过程中与水蒸气的平衡分压进行了计算。     

A ca. 800-Year Lithologic Record of Drought from Sub-annually Laminated Lake Sediment, East Java

Lithostratigraphic analyses of a sub-annually laminated core from Ranu Lamongan, a maar lake on the island of Java, document considerable changes in the lake’s chemistry and water balance over the past ca. 800 calendar years. Composition of the dark (clastics) and light (diatoms and/or calcium carbonate minerals) couplets suggests that these laminations form in response to seasonal changes in rainfall and water-column overturn in the lake. Calcium carbonate is not continuous in the core, and when it occurs it varies, sometimes abruptly, in carbonate phase and elemental composition (low Mg-calcite Mg-calcite, and aragonite). A significant correlation between Mg/Ca changes and δ¹⁸O variations in authigenic calcium carbonate suggest the basin is highly sensitive to hydrologic variation. Lithologic data suggest calcium carbonate precipitates and thus records hydrologic conditions during the dry season – a season in which rainfall anomalies are highly correlated with the phase of ENSO. Our carbonate-based record of Mg/Ca shows variability in evaporative concentration on a quasi-seasonal frequency for the past ca. 800 years. Our record shows two multi-decadal periods of drought – ca. 1275–1325 and ca. 1450–1650 CE – the latter of which was especially strong and/or prolonged. Our record also shows a possible change in drought frequency at around 1650 CE, in which periods of calcium carbonate precipitation and Mg/Ca change shifted from multi-decadal to interannual variability. Given the strong correlations between modern-day drought in East Java and ENSO variability, our drought record may indicate a regime shift in the behavior of the ENSO system about 350 years ago. Finally, comparisons between our record and others suggest that variation in ENSO on centennial and sub-centennial scales is not strongly associated with changes in the global mean climate state.     

氯离子守恒法确定土壤生态蓄水量

通过实验测得降水及土壤水的氯离子浓度,依据化学守恒原理,即降水与包气带土壤水中氯离子的质量守恒关系,计算出长春市丘陵、台地、阶地3类不同地貌区土壤一年内所得水量,该水量为土壤生态蓄水量。将土壤生态蓄水量与土壤的田间持水量、作物的生态需水量进行对比分析,评述了三者之间的关系。阐明土壤生态蓄水量不仅能客观反映土壤中的水分含量情况,也能对植被生态需水量的满足情况给予客观评价。     

碳酸钙矿物表面润湿性的控制机理

系统论述了碳酸钙矿物浮选中常用的捕收剂和抑制剂及其相关作用机理。这些药剂通过包括静电作用、氢键、半胶束吸附和化学吸附等多种机理,吸附在碳酸钙矿物表面,从而控制矿物表面的润湿性。捕收剂的功能在于增强矿物表面的疏水性,抑制剂的功能在于增强矿物表面的亲水性。选择合适的捕收剂和抑制剂复配方案对高效浮选分离至关重要。