Fluoride ion contamination in the groundwater of Mithi sub-district, the Thar Desert, Pakistan

Groundwater samples were collected from various localities of Mithi sub-district of the Thar Desert of Pakistan and analysed for fluoride ion along with other chemical parameters. The area is mainly covered by sand dunes and kaolin/granite at variable depths. Results showed that collected water samples were severely contaminated by the presence of fluoride ion and most of the samples have higher concentration than prescribed WHO standards (1.5 mg/l) for drinking water. Fluoride ion concentrations ranged between 0.09 and 11.63 mg/l with mean and median values of 3.64 and 3.44 mg/l, respectively, in this area whereas, distribution pattern showed high concentrations in the vicinity of Islamkot and Mithi towns. The content of F⁻ has also been correlated with other major ions found in the groundwater of the study area. The positive correlation of F⁻ with Na⁺ and HCO₃ ⁻ showed that the water with high Na⁺ and HCO₃ ⁻ stabilizes F⁻ ions in the groundwater of the Thar Desert. The pH versus F⁻ plots signifies high fluoride concentration at higher pH values, implying that alkaline environment favours the replacement of exchangeable OH⁻ with F⁻ in the groundwater of Mithi area. The saturation indices (SI) of fluorite (CaF₂) and calcite (CaCO₃) in the groundwater samples showed that most of the samples are oversaturated with respect to calcite whereas majority of samples have been found under saturated with respect to fluorite. The log TDS and Na/Na+Ca ratio reflected supremacy of weathering of rocks, which promotes the availability of fluoride ions in the groundwater. Piper diagram has been used to classify the hydrofacies. In the cation triangle, all samples are Na-type, while the anion triangle reflects major dominance of Cl-type with a minor influence of HCO₃ ⁻ and SO₄ ⁻.     

土壤中不同形态砷的分析方法

选取磷酸作为提取剂,比较了超声和水浴两种方法辅助提取土壤中不同形态的砷,离子色谱一氢化物发生原子荧光光谱联用法(IC-HGAFS)测定砷的4种形态,即As(Ⅲ)、As(Ⅴ)、MMA (甲基胂酸)和DMA(二甲基胂酸)。从测定结果可以看出,水浴的提取效果明显高于超声的提取效果。土壤中砷以无机态为主,而无机态砷又以As(Ⅴ)为主,没有检测到有机砷。测定土壤中各种形态砷的加标回收率为72.0%～105.4%,相对标准偏差(RSD,n=5)为2.61%～8.19%。     

气相色谱法定量测定烃源岩中轻烃的含量

将烃源岩石使用低沸点溶剂密封抽提,采用高分辨毛细柱进行色谱分析,在选定的色谱条件下,能获得C5~C30的烃类物质信息。选用色谱内标法对C6~C15轻烃组分进行定量分析研究,由于轻烃组分的不同挥发性,以1-己烯作内标物来控制C6~C7烃类物质的定量,以1-壬烯作内标物来控制C7~C15(含C7)烃类物质的定量。结果表明,方法加标回收率大于85%,重复性分析相对误差小于10%。方法稳定可靠,能准确提供烃源岩中C6~C15轻烃的定量数据,有效应用于油气田勘探资源量评价中。     

柴达木盆地西北部库拉木勒克萨伊河—阿拉尔河流域水化学特征分析

运用水文地球化学常用分析方法,对柴达木盆地西北部库拉木勒克萨伊河—阿拉尔河流域进行了系统研究,分析了河水中主要离子特征、控制机制及其来源。结果表明:该流域为低矿化度、天然弱碱性淡水;河水类型主要为重碳酸盐型水,部分为氯化物型水;河水中主要离子的化学特征受控于岩石风化作用,流域蒸发作用逐渐显露,阿拉尔河蒸发作用较明显。河水中主要离子来自于岩盐、钾盐、硬石膏、白云石和方解石的风化溶解,并且受到少量溶解于河水中硅酸盐矿物的影响。     

High‐Precision Measurement of Molybdenum Isotopic Compositions of Selected Geochemical Reference Materials

Here we describe high‐precision molybdenum isotopic composition measurements of geological reference materials, performed using multi‐collector inductively coupled plasma‐mass spectrometry (MC‐ICP‐MS). Purification of Mo for isotopic measurements was achieved by ion exchange chromatography using Bio‐Rad AG^® 1‐X8 anion exchange resin. Instrumental mass bias was corrected using ¹⁰⁰Mo‐⁹⁷Mo double spiking techniques. The precision under intermediate measurement conditions (eighteen measurement sessions over 20 months) in terms of δ^98/95Mo was 0.10‰ (2s). The measurement output was approximately four times more efficient than previous techniques, with no compromise in precision. The Mo isotopic compositions of seven geochemical reference materials, seawater (IAPSO), manganese nodules (NOD‐P‐1 and NOD‐A‐1), copper‐molybdenum ore (HV‐2), basalt (BCR‐2) and shale (SGR‐1b and SCo‐1), were measured. δ^98/95Mo values were obtained for IAPSO (2.25 ± 0.09‰), NOD‐P‐1 (?0.66 ± 0.05‰), NOD‐A‐1 (?0.48 ± 0.05‰), HV‐2 (?0.23 ± 0.10‰), BCR‐2 (0.21 ± 0.07‰), SCo‐1 (?0.24 ± 0.06‰) and SGR‐1b (0.63 ± 0.02‰) by calculating δ^98/95Mo relative to NIST SRM 3134 (0.25‰, 2s). The molybdenum isotopic compositions of IAPSO, NOD‐A‐1 and NOD‐P‐1 obtained in this study are within error of the compositions reported previously. Molybdenum isotopic compositions for BCR‐2, SCo‐1 and SGR‐1b are reported for the first time.     

温度和铜离子浓度对近江牡蛎超氧化物岐化酶活力的联合效应

Superoxide dismutase(SOD) is a crucial antioxidant enzyme playing the first defense line in antioxidant pathways against reactive oxygen species in various organisms including marine invertebrates. There exist mainly two specific forms, Cu/Zn-SOD(SOD1) and Mn-SOD(SOD2), in eukaryotes. SODs are known to be concurrently modulated by a variety of environmental stressors. By using central composite experimental design and response surface method, the joint effects of water temperature(18–34°C) and copper ion concentration(0.1–1.5 mg/L) on the total SOD activity in the digestive gland of Crassostrea ariakensis were studied. The results showed that the linear effect of temperature was highly significant(P0.01), the quadratic effect of temperature was significant(P0.05); the linear effect of copper ion concentration was not significant(P0.05), while the quadratic effect of copper ion concentration was highly significant(P0.01); the interactive effect of temperature and copper ion concentration was not significant(P0.05); the effect of temperature was greater than that of copper ion concentration. The model equation of digestive gland SOD enzyme activity towards the two factors of interest was established, with R2 and predictive R2 as high as 0.961 6 and 0.820 7, respectively, suggesting that the goodness-offit to experimental data be very satisfactory, and could be applied to prediction of digestive gland SOD activity in C. ariakensis under the conditions of the experiment. Our results would be conducive to addressing the health of aquatic animals and/or to detecting environmental problems by taking SOD as a potential bioindicator.     

湖南新田富锶地下水水化学特征与成因分析

研究湖南新田富锶地下水水化学特征及成因,为富锶地下水的可持续利用与开发提供理论依据。对研究区21个下降泉、30个机井富锶地下水样品的水化学类型、化学成分含量特征、成分间相关性以及离子比值的研究。结果表明：下降泉水化学类型全部为HCO3-Ca型,机井水化学类型以HCO3-Ca、HCO3-Ca·Mg型为主。相关分析表明,下降泉和机井中SO42-与Ca2+、Mg2+均表现显著相关或极显著相关,HCO3-与Ca2+、SO42-与NO3-在下降泉与机井中的相关性具有差异,下降泉、机井Sr与Ca2+、Mg2+、HCO3-均表现为极显著相关。Gibbs图表明下降泉和机井的水化学组成主要受水-岩相互作用的控制,下降泉、机井c(Ca2+)/c(Mg2+)、c(HCO3-)/c(SO42-+Cl-)、c(Na+)/c(Cl-)、c(Cl-)/c(Ca2+)系数比值具有差异。结果表明富Sr地下水的形成受碳酸盐岩成分影响显著,赋存条件的差异导致富锶地下水在下降泉、机井中的水化学特征、相关性以及离子系数比值的差异。     

基于Sentinel--2A的阿里萨罗盐湖锂资源遥感定量分析

为探究阿里萨罗盐湖中锂资源的空间分布状况,笔者利用Sentinel--2A卫星数据和锂离子含量实测数据对其进行统计分析,并利用波段组合方法建立盐指数,再结合主成分分析对盐湖中的锂离子含量进行分离,建立盐湖中锂离子含量遥感预测模型。结果表明,此遥感预测模型的盐湖中锂离子含量预测结果精度均 80%,预测得到的锂离子含量分布情况与实际情况基本一致。     

金属同位素质谱中分析样品处理的基本原则与方法

二十年来,国内外相继建立了多种金属（铁铜锌镁钙锂钼硒汞铬镉矾钡钛等）同位素的分析方法。金属同位素分析中的样品处理包括两个过程：样品的消解和样品中待测元素的分离纯化。为了获得真实、准确的金属同位素数据,样品处理过程必须遵守两个基本原则：①不引入待测元素以及可能会对待测元素同位素分析产生干扰的元素;②待测元素不发生损失。金属同位素分析常用的样品消解方法是酸溶法（包括高压闷罐法和微波消解法）。待测元素的分离纯化主要使用离子交换分离法。相同的树脂可以用于不同元素的化学分离,同一种元素也可以使用不同的树脂进行化学分离。不同类型样品的基质差异较大,需要不同的流程对待测元素进行分离。研究人员可以通过改变前人的分离流程,包括改变树脂的用量、变换淋洗液或用量、增加分离步骤等方法来满足不同样品的分离要求。本文提出了金属同位素样品处理中需要注意的一些细节：①如果消解样品时使用了高氯酸,必须将高氯酸在高温下彻底去除,因为残余的高氯酸具有强氧化性会使后续化学分离中使用的离子交换树脂失效,影响分离效果;②同一体积的树脂放入不同内径的交换柱中,树脂柱越细越长,淋洗液流速越慢、洗脱时间越长,并且待测元素洗脱出来越滞后;③离子交换过程中,每次加入的试剂体积越小,淋洗出来的元素越集中,分离效果越好。