四川黄龙沟天然水中的深源CO_2与大规模的钙华沉积

在有大规模钙华沉积的四川黄龙沟中,使用化学成分数据以及碳氧稳定同位素组成对其水文地球化学特征进行了分析研究。研究区钙华沉积的地表溪流水质基本上受到两种水混合的制约,即断层泉水和山区的融雪(冰)水。泉水中含有高浓度的经由断层提供的CO2,结果高浓度的溶解CO2使得其溶解的碳酸盐岩比普通的岩溶泉溶解的碳酸盐岩高得多,同时也导致硅酸盐岩的溶解。黄龙沟中上游的泉水相对于方解石接近于平衡。溶解无机碳(DIC)的浓度和它们的δ13C值是大约由c=0.02mol·L1δ13C=-3‰的CO2(aq)与含有δ13C=+3‰的碳酸盐岩在封闭系统条件下反应的结果。估计这些CO2中约有70%来自上地幔。所有泉水的水化学数据均落在高岭石稳定域内,但对Na长石和Ca长石具有侵蚀性。由于这些长石矿物的溶解速率太慢,所以水中的化学成分远离长石稳定域。地表溪流的DIC种类之间达到同位素平衡,在不同观测点发现的δ13CDIC变化主要是由于从水中释放出的CO2的程度不同引起的。水样的δ18O值与其采集点的海拔高度之间存在线性关系;研究区的地表溪流的氧同位素组成受到蒸发的制约。在流经钙华沉积物的地表溪流中白天和夜晚的水化学及pH的日变化表明生物作用促进了碳酸盐的沉积,尽管作用不显著。据估计研究区碳酸钙的日沉积速率是4778kg·km2,即约1mm·a1。     

华北地区城市地下水中主要离子含量升高机理分析——以洛阳市为例

本文以洛阳市为例，讨论了华北地区地下水中主要离子的背景浓度及其形成作用。在此基础上，重点阐述了地下水中Ｃａ＾２＋，Ｍｇ＾２＋浓度升高的若干机理，并对污染源各不相同的三个水源地地下水Ｃａ＾２＋，Ｍｇ＾２＋浓度升高机理进行了定量分析，比较了Ｃａ＾２＋，Ｍｇ＾２＋浓度与其它主要离子浓度的相关特征，研究表明：该区两类地下水主要形成了钙长石和镁榄石的风化作用，地下水中ＣＯ２分压升高，可促进Ｃａ，Ｍｇ硅酸盐，     

马莲河流域化学风化的季节变化和影响因素

为查明黄土高原马莲河流域不同季节河水化学的变化特征、来源及主要控制因子,2016年1~12月在流域下游雨落坪水文站采集时间序列水样40组,分析了主要离子组成并计算了化学风化速率.结果表明,河水总溶解固体(TDS)均值1 154.0 mg·L~(-1),远高于长江、黄河和珠江.阳离子以Na+为主,均值202.8 mg·L~(-1),其次为Ca~(2+)和Mg~(2+),阴离子以SO_4~(2-)为主,均值431.2 mg·L~(-1).主要离子质量浓度的季节变化明显,总体规律是雨季前降低,雨季后增高,在融冰期和暴雨期分别突增和骤降.离子来源主要为岩石化学风化,蒸发岩、硅酸盐和碳酸盐贡献比例均值分别为67.1%、13.7%和19.2%.矿物含量和风化速率的不同决定了各风化作用对气候变化的差异响应:蒸发岩因其高风化速率对季风气候响应积极,雨季风化作用增强;雨季前期河水流量低,较长的水岩作用时间有利于硅酸盐风化进行;碳酸盐风化作用在雨季晚期和后期明显增强,可能因其在黄土中含量较高,雨季后降雨吸收了更多的土壤CO_2形成H2CO3增进了碳酸盐的溶解.蒸发岩、碳酸盐风化速率和流量显著正相关,流量是控制流域化学风化的主要因素.     

Comparison of surface water chemistry and weathering effects of two lake basins in the Changtang Nature Reserve, China

The geochemistry of natural waters in the Changtang Nature Reserve,northern Tibet,can help us understand the geology of catchments,and provide additional insight in surface processes that influence water chemistry such as rock weathering on the Qinghai–Tibet Plateau.However,severe natural conditions are responsible for a lack of scientific data for this area.This study represents the first investigation of the chemical composition of surface waters and weathering effects in two lake basins in the reserve(Lake Dogaicoring Qiangco and Lake Longwei Co).The results indicate that total dissolved solids(TDS)in the two lakes are significantly higher than in other gauged lakes on the Qinghai–Tibet Plateau,reaching 20–40 g/L,and that TDS of the tectonic lake(Lake Dogaicoring Qiangco)is significantly higher than that of the barrier lake(Lake Longwei Co).Na+and Cl-are the dominant ions in the lake waters as well as in the glacier-fed lake inflows,with chemical compositions mainly affected by halite weathering.In contrast,ion contents of inflowing rivers fed by nearby runoff are lower and concentrations of dominant ions are not significant.Evaporite,silicate,and carbonate weathering has relatively equal effects on these rivers.Due to their limited scope,small streams near the lakes are less affected by carbonate than by silicate weathering.     

Are calcareous soils in uplands less prone to damage from road salting than acidic soils?

Previous studies of upland roadside soils in Cumbria, that would normally be naturally acidic, have highlighted that (a) runoff from roads subjected to long-term road salting can dramatically raise soil pH down slope in upland areas; (b) the soil pH increase dramatically changes N cycling in soils down slope, increasing mineralisation of organic matter, ammonification, ammonium leaching down slope and nitrification and nitrate leaching; (c) the increase in nitrification substantially increases nitrate leaching to down-slope rivers, and this is readily detectable in field studies; and (d) loss of soil organic matter over decades of salting is so great that organic matter is no longer substantially solubilised by high salt concentrations found in soil solution below road drains. This paper tests and supports the hypothesis that such effects are minimal for more calcareous soil ecosystems. It examines the soil and soil solution chemistry on another Cumbrian upland highway, the A686 near Leadgate, Alston. Sodium % of soil CEC values for soil transects affected by spray containing road salt are similar at both the A6 and A686 sites. However, spatial trends in calcium, magnesium, ammonium, and nitrate concentrations as well as pH differ, as a direct result of the higher weathering rate of parent material and possibly also the presence of limestone walls above both spray-affected and control transects at the A686 site.     

INCREASES IN SODIUM AND CHLORIDE IN THE MOHAWK RIVER,NEW YORK,FROM THE 1950'S TO THE 1970'S ATTRIBUTED TO ROAD SALT1

Regression analyses of major ion concentration in relation to specific conductance of water from the Mohawk River during two separate periods, 1951–53 and 1970–74, indicate statistically insignificant changes in the linear relationship of all constituents studied except chloride. Mean values and changes in the slopes of these relationships indicate that sodium and chloride have had consistently higher yields, in kilograms per square kilometer per year, than the other ions, although all ions show a general 20 percent increase in yields during the two decades. This general increase in ion yields is attributed to an accelerated transport rate of ions out of the basin as a result of a 19 percent increase in mean stream discharge. Transport rates of sodium and chloride have increased by 72 and 145 percent, respectively, in the Mohawk River since the early 1950's. Analysis of the sodium and chloride sources indicates rock salt used as a road deicei to be the primary source. This salt use accounts for 96 percent of the sodium transport increase and 69 percent of the chloride transport increase within the basin during the last two decades.     

Climatic Variation and Solute Concentration and Flux in Meltwaters Draining from an Alpine Glacier

Measurements of electrical conductivity and discharge ofmeltwaters in the Gornera, which drains from the 83%glacierised basin containing Gornergletscher, PennineAlps, Switzerland, were undertaken between May andSeptember in both 1979 and 1998. Discharge in theGornera was 43% higher in 1998, average air temperatureduring the ablation season being 2.1 °C warmer andpreceding winter precipitation 28% lower than in 1979. Mean electrical conductivity of meltwater in 1998 wasreduced by 40%. In the same 60 day period in 1998,however, solute flux was augmented by only 2% bycomparison with 1979. Year-to-year climatic variations,reflected in discharge variability, strongly affectsolute concentration in glacial meltwaters, but havelimited impact on solute flux. Climatic conditionstranslate into meltwater quality through inter-relationships between mineral reaction rates, subglacialresidence time in contact with sediment, and discharge. Annual variability in solute flux depends on the extentto which volume of flow can offset decline in soluteconcentration brought about by reducing residence time.     

Leaching Induced Changes in Substrate and Solution Chemistry of Mine Soil Microcosms

Leaching of soluble salts formed as the result of pyrite oxidation and primary mineral weathering is a major process in mine soil development. A microcosm experiment was designed to study leaching rates from mine soil columns under controlled laboratory conditions. Objectives of this experiment were to investigate the effect of leaching and the effect of fly ash amelioration on mid- to long-term chemical soil properties, and to test whether the results are qualitatively comparable to long-term field studies along a site chronosequence. The leaching experiment was conducted over a period of 850 days representing a kind of time-lapse picture due to high water fluxes. Leaching resulted in more favourable mid- to long-term properties of mine site topsoils, especially a reduced risk for acidity and salt stress. Ash amelioration decreases leaching rates by increasing pH and Al and Fe precipitation. It could be shown that the results of the column leaching studies are qualitatively in good agreement with field observations at least for long-term considerations. By enhancing the leaching process mid- to long-term chemical soil properties can be estimated.     

Biodegradation of Crude Oil Contaminating Marine Shorelines and Freshwater Wetlands

This paper is a summary of the various factors influencing weathering of oil after it has been released into the environment from a spill incident. Special emphasis has been placed on biodegradation processes. Results from two field studies conducted in 1994 and 1999 involving bioremediation of an experimental oil spill on a marine sandy shoreline in Delaware and a freshwater wetland on the St. Lawrence River in Quebec, Canada have been presented in the paper.     

典型耐候钢在江津大气环境中暴晒1 a的腐蚀行为

目的 研究3种典型耐候钢在江津大气环境中暴晒1 a的初期腐蚀行为。方法 采用户外大气挂片、腐蚀质量损失、SEM、XRD、电化学等方法,研究Q355NH、Q460FRW、Q690的腐蚀速率、锈层形貌、锈层物相和锈层电阻,并与Q345碳钢进行对比。结果 耐候钢和碳钢在大气暴晒初期的腐蚀规律是一致的,Q355NH、Q460FRW、Q690和Q345碳钢的腐蚀速率分别为0.050 9、0.053 6、0.047 8、0.055 mm/a,Q690的腐蚀速率最小,约为碳钢的87%。耐候钢和碳钢的锈层都主要由α-FeOOH、γ-FeOOH和Fe₂O₃组成,耐候钢的锈层更致密,裂纹更少。Q355NH、Q460FRW、Q690的锈层电阻值分别为821.3、1 005、1 080?·cm²,碳钢为101.68?·cm²,耐候钢的锈层电阻值约为碳钢的10倍。Cr和Cu元素在耐候钢的锈层中富集明显。结论 耐候钢的腐蚀速率低于碳钢,3种耐候钢的耐蚀性顺序为Q690>Q355NH>Q460FRW。Cr和Cu元素在...