有机单体同位素分析技术在地下水污染中的研究现状

有机单体同位素分析(CSIA)在地下水污染研究领域的测试数据主要应用于:确定污染物的来源;确定和量化污染场地的生物(或非生物)迁移反应;表征生成分子的元素反应机理.介绍了CSIA分析前处理技术及水污染研究领域中应用CSIA方法确定污染物来源和生物非生物降解分馏作用的研究进展,总结了CSIA技术在其他稳定同位素领域的研究进展和未来发展方向.     

冰川沉积物成因确定的一种新方法

冰川沉积物的成因鉴定一直存在争论,尤其是体现在讨论第四纪冰川沉积物的成因确定问题方面,传统地质学从冰川沉积物的沉积学和地貌学特征方面来讨论其成因受到了挑战,本文试图从沉积砾石中寻找与冰川成因直接相关的应用信息,进而提出用砾石的声发射应力测量法确定其冰川成因的新认识,首先对现代冰川砾石进行声发射应力测量,将此测量值丙与 石所受的实际铅直应力值比较,研究显示二者对应很好,说明冰川砾石是能够记忆上覆冰层所造成的应力,其次,无争议的第四纪冰川砾石亦具有对应的应力记录,最后讨论了有争议的庐山地区第本四冰川沉积,研     

Chemical Weathering of Pleistocene Glacial Outwash Sediments: A Comparison of Contemporary and Long-term Rates for Soils and Groundwaters

Pore water solutes increase to depths of up to six meters in unsaturated 10 kyr-old glacial outwash sediments in the Trout Lake Basin of northern Wisconsin, USA. After correction for evapotranspiration, these increases reflect weathering gradients produced from plagioclase, calc-magnesium pyroxenes, and amphiboles. In spite of relatively abundant K-feldspar, solute K and Rb reflect negative gradients produced by nutrient plant uptake and cycling. Weathering rates are calculated from solute gradients (b _solute), hydraulic fluxes (q _h ), volumetric BET surface areas (S _v ), and mineral-specific stoichiometric coefficients (β) such that $ R_{\text{solute}} = \frac{{q_{h} }}{{b_{\text{solute}} \beta {\kern 1pt} {\kern 1pt} S_{v} }} $ Average plagioclase weathering rates (R _plag = 1.6–3.1 × 10^?15 mol m^?2 s^?1) bracket rates calculated for other Quaternary glaciated landscapes. Deeper soil pore waters are as chemically concentrated as underlying groundwaters which, based on hydrologic analyses, have traveled distances up to several kilometers over transient times of hundreds of years. Pore water recharge essentially sets solute compositions close to thermodynamic saturation, thus limiting additional weathering potential along these ground water flow paths. Solid-state elemental and mineral gradients, unlike solute gradients, are essentially invariant with soil depth, reflecting low weathering intensities produced over the relatively short geologic time since sediment deposition. A spreadsheet calculator reproduces modest mass loses from such profiles and indicates that present-day weathering is kinetically and not saturation/transport controlled.     

氢同位素分析样品制备新方法

发展了氢同位素分析新方法－石墨还原法，其分析精度达到1．5‰，优于常规的金属还原法。通过多次改进，设计了简单而可靠的氢气制备系统及反应管，经反复试验，确定了石墨还原法的最佳反应条件为反应时间10min，反应温度1050℃，将石墨的法与传统的金属锌还原法进行了对比实验，两种方法对多个水样的测量结果保持在误差范围内，进一步确立了石墨还原法的可靠性。     

海洋沉积物的锌同位素地球化学及其应用

锌同位素体系是海洋地球化学研究的新示踪剂,应用于示踪海水中锌元素的来源及其运移过程.海洋沉积物作为锌元素重要的"源"与/或"汇",其锌同位素组成的研究有助于理解海洋锌元素的地球化学循环.海洋沉积物记录了海水组成的信息,可以反演古海水锌同位素组成的变化,前提是理解沉积物与海水之间的分馏.对海水及海洋不同储库锌同位素研究进行系统总结,包括河流输入、热液体系、不同类型海洋沉积物(如富碳酸盐的沉积物、陆源硅酸盐碎屑、硅质沉积物、铁锰结核、贫氧-缺氧沉积物)的锌同位素组成,阐述了海洋沉积物锌同位素组成变化在古气候、古环境重建以及古海洋学等领域的应用以及重要性.      

Factors Controlling Sulfide Geochemistry in Sub-tropical Estuarine and Bay Sediments

The primary factors that control the concentration of total reduced (inorganic) sulfide in coastal sediments are believed to be the availability of reactive iron, dissolved sulfate and metabolizable organic carbon. We selected nine sites in shallow (<3 m), close to sub-tropical, estuaries and bays along the central Texas coast that represented a range in sediment grain size (a proxy for reactive iron), salinity (a proxy for dissolved sulfate), and total organic carbon (a proxy for metabolizable organic carbon). Based on these parameters a prediction was made of which factor was likely to control total reduced sulfide at each site and what the relative total reduced sulfide concentration was likely to be. To test the prediction, the sediments were analyzed for total reduced sulfide, acid volatile sulfide, and citrate dithionate-extractable, HCl-extractable and total Fe in the solid phase. Using solid-state gold–mercury amalgam microelectrodes and voltammetry, we determined pore water depth profiles of Fe(II) and ΣH₂S and presence or absence of FeS_(aq). At five of the nine sites the calculated degree of sufildization of citrate dithionite-reactive-iron was close to or greater than 1 indicating that rapidly reactive iron was probably the limiting factor for iron sulfide mineral formation. At one site (salinity = 0.9) dissolved Fe(II) was high, ΣH₂S was undetectable and the total reduced sulfide concentration was low indicating sulfate limitation. At the last three sites a low degree of sulfidization and modest total reduced (inorganic) sulfide concentrations appeared to be the result of a limited supply of metabolizable organic carbon. Fe(II)–S(-II) clusters (FeS_(aq)) were undetectable in 10 out of 12 bay sediment profiles where ΣH₂S was close to or below detection limits, but was observed in all other porewater profiles. Acid volatile sulfide, but not total reduced sulfide, was well correlated with total organic carbon and ranged from being undetectable in some cores to representing a major portion of total reduced sulfide in other cores. Although predicted controls on total reduced sulfide were good for very low salinity water or sandy sediments, they were only right about half the time for the other sediments. The likely reasons for the wrong predictions are the poor correlation of total organic carbon with grain size and differing fractions of metabolizable organic carbon in different sedimentary environments. Differences in sediment accumulation rates may also play a role, but these are difficult to determine in this region where hurricanes often resuspend and move sediments. This study demonstrates the need to examine more complex and often difficult to determine parameters in anoxic “normal marine” sediments if we are to understand what controls the concentration and distribution of sulfides.     

Estuarine Dispersion from Tidal Trapping: A New Analytical Framework

Observations of tidal trapping in a channel connected to large volumes along its perimeter showed that the exchange between them is driven by advection due to tidal flows. Therefore, quantifying the longitudinal dispersion of scalars in the channel that results from tidal trapping was not possible using traditional frameworks, which assume that the exchange is a diffusive process. This study uses the concentration moment method to solve analytically for the dispersion coefficient of a solute in a tidal channel which exchanges advectively with volumes along its edges. This constitutes a new framework for analyzing the longitudinal dispersion that results from tidal trapping in systems such as a branching tidal channel or the breached salt ponds of San Francisco Bay. A comparison of dispersion coefficients from traditional, diffusion-driven frameworks for tidal trapping, the new advective framework derived in the present study, and observations show that the new formulation is best suited to this environment.     

Hf Isotope Systematics of Kimberlites and their Megacrysts: New Constraints on their Source Regions

Kimberlites from Southern Africa, along with their low-Cr megacrysts,have unusual Hf–Nd isotopic characteristics. Group I andTransitional kimberlites define arrays trending oblique to,and well below, the Nd–Hf isotope ‘mantle array’,defined by oceanic basalts, i.e. they have negative     

Albany K-Feldspar: A New Pb Isotope Reference Material

Lead isotopes are a powerful and versatile tool to elucidate fundamental geological problems related to the formation and evolution of continental crust. K-feldspar is a popular target for Pb isotope measurement as it is prevalent in many rock types and tends to capture the initial Pb isotope composition of its parental magma. We present data for a new Pb isotope reference material: Albany K-feldspar; as well as updated data for Shap K-feldspar. Results of Pb double-spike TIMS for Albany K-feldspar are ²⁰⁶Pb/²⁰⁴Pb = 16.7872 ± 0.0062, ²⁰⁷Pb/²⁰⁴Pb = 15.5640 ± 0.0056, and ²⁰⁸Pb/²⁰⁴Pb = 36.6600 ± 0.0168 (2s). TIMS measurement results for Shap K-feldspar indicate two isotopically distinct Pb populations. LA-MC-ICP-MS, with a spatial resolution as high as 15 μm, indicates a homogeneous Pb isotopic composition in Albany K-feldspar. In accord with previous studies, our results show that scatter in the measured Pb isotope ratios, related to the low natural isotopic abundance of ²⁰⁴Pb, along with the effect of isobaric ²⁰⁴Hg-²⁰⁴Pb interference, increases at lower count rates. However, the mean Pb isotope ratios measured via LA-MC-ICP-MS using a range of spot sizes are in excellent agreement with TIMS results thus highlighting the feasibility of Pb isotope determination via LA-MC-ICP-MS to access geological information preserved in small crystals, including mineral inclusions.     

碳同位素技术在碳质气溶胶源解析中应用的研究进展

概述了国内外14C和13C技术在大气碳质气溶胶源解析中应用的研究进展,指出14C在碳质气溶胶源解析研究中具有不可替代的独特优势,联合采用14C和13C技术有利于解决多种排放源的区分问题;随着碳质气溶胶组分分离技术的进步,对有机碳(0C)和黑碳(BC)等组分中14C的研究获得重要进展;除需深入研究13C的分馏机制外,建立各种排放源在不同区域的δ13C值域“特征谱”的重要性也日益突出;结合14C和13C以外的其他示踪剂、模型和分析方法将提供更多关于气溶胶来源的信息,并减小来源贡献率估算的不确定性.     

铜同位素示踪覆盖区地表土壤的异常来源初探:以福建罗卜岭隐伏铜钼矿床为例

地表微细粒土壤地球化学测量是国内研究较多的深穿透地球化学方法之一,判断地表异常与深部隐伏矿体的关系是未来该方法广泛应用的理论基础。以已知的隐伏矿床——紫金山罗卜岭铜钼矿床为研究对象,利用铜同位素示踪覆盖区地表土壤的异常来源。结果显示:(1)矿石单矿物的δ⁶⁵Cu变化范围较小(-0.04‰~0.56‰),指示较高的成矿温度(250~300 ℃);钻孔由深至浅,矿石的δ⁶⁵Cu值具有明显升高的趋势,符合斑岩型成矿系统早期至晚期铜同位素的变化特征,流体分馏是造成不同阶段形成的矿石铜同位素存在差异的主要原因。(2)背景区地表土壤铜含量的平均值(59.4 μg/g)显著低于异常区(131.0 μg/g)。背景区土壤δ⁶⁵Cu变化范围为-1.94‰~-0.82‰,平均值为-1.38‰;异常区土壤δ⁶⁵Cu变化范围为-5.01‰~1.05‰,平均值为-1.40‰,背景区和异常区铜同位素组成相差不大。(3)本次利用铜同位素组成判别地表介质铜异常来源的效果不理想,可能因为矿石本身的铜同位素组成存在差异,地表土壤本身的铜同位素信息覆盖了来自深部与隐伏铜矿体有关的信息,或从深部原生环境迁移至地表氧化环境的过程中,因氧化还原反应发生了铜同位素的分馏。     

古高程计：氢氧同位素的新应用

定量恢复高大地形的古高程是地质学家一直以来追求的目标，将自生矿物中氢氧同位素用作古高程计的历史不长，这种方法还有很大的应用潜力，可用到比新生代更古老的时期。根据与气团上升和水汽凝结的热动力学性质相关的瑞利平衡分馏原理，建立了这种古高程计的热动力模型，这个模型应用简便，适用于纬度小于35°的地区。区域性经验关系的方法误差较小，但也有计算繁琐、适用区域有限的不足。以上两种方法的计算精度均有待于提高。研究中使用方解石作为样品最普遍，在方解石、高岭石、蒙脱石和针铁石等矿物中,究竟使用哪种推算古高程产生的误差更小，还需进一步研究。     

土壤和沉积物中重金属生物可利用性的评估

土壤和沉积物中重金属被植物吸收利用可通过单一化学萃取方法评估。几种重金属生物可利用态的萃取方法被用于土壤和沉积物中重金属的提取。根据实验萃取结果和文献报道,对中性盐、弱酸、螯合剂和联合萃取法进行评价,对影响生物可利用态萃取方法的因素进行讨论,并对土壤和沉积物中重金属生物可利用性评价方法的建立和有效统一使用提出建议。     

土壤甲烷及其碳同位素地球化学特征

本文重点对我国干旱-半干旱区油气异常区和非油气区地表土壤甲烷的碳同位素组成进行了分析;据此,对土壤、重烃及甲烷的碳同位素地球化学特征进行了讨论。     

The Diversity of Organic Matter in Marine Sediments and the Suspiciousness of Source Parameters: A Review

There are various types of Organic Matter (OM) in marine sediments, and it is of great significance to accurately estimate the source of them. The methods used in most researches include element ratio (C/N), stable isotopes (δ¹³C) and biomarkers (BIT), all of which are used for the whole sample as objects and calculated by end-member of terrestrial and marine source OM, respectively. However, OM is preserved in different ways, such as on its own recalcitrance or combining with inorganic minerals. Preservation differences make their respective parameter values change. After differential sedimentary by gravity or other factors,different preservation types of OM are enriched or dispersed, making some parameters distorted and even meaningless in some areas. Therefore, the parameters of OM measured by the whole sample are influenced by the source of OM and the way of deposition and preservation. Therefore, it is unreliable to use these parameters to study the source of OM without considering the way of preservation. Based on this, this paper put forward a method of particle separation to separate the sediment in different propertied and preservation types. According to the composition and characteristics of the OM at the specific grain level, the corresponding index and end-members value were used to calculate more accurate proportion of the OM. It is of profound significance to understand the production, aggregation, occurrence, migration and deposition of OM and its evolution in the entire carbon cycle.     

New Method to Obtain Quantified Data on Color of Marine Sediments

Doklady Earth Sciences - A new method of quantitative determination of color using an original photodevice is presented for marine sediments, which are a specific geological object. The advantages...     

A Comparison of Otolith Geochemistry and Stable Isotope Markers to Track Fish Movement: Describing Estuarine Ingress by Larval and Post-larval Halibut

Estuarine recruitment of fishes is a potential bottleneck in the life cycle of many coastal species. We investigated patterns of size-at-ingress for larval and post-larval California halibut entering the Punta Banda Estuary (PBE), Mexico, using both otolith geochemistry and carbon stable isotope ratios (SIR). Juvenile halibut (n?=?126; 38–163 mm standard length [SL]) were collected from inside PBE and the adjacent exposed coast during the fall of 2003, and otoliths (geochemistry) and muscle tissues (SIR) were analyzed to reconstruct the environmental histories of individuals. Based on geochemical analyses, nearly all fish collected from PBE were characterized by a non-estuarine signature (e.g., low Mn and Ba) in the otolith growth bands deposited when fish were <30 mm SL. Although fish collected from the coast retained that signature throughout their lives, fish collected within PBE showed elevated concentrations of Mn and Ba in the otolith growth bands deposited once halibut were 30–70 mm SL, thereby recording ingress. Carbon SIR of juvenile halibut prey also differed between the estuary and coast. Muscle δ ¹³C values of halibut captured along the coast were consistent (ca.?15‰), while those captured in the estuary were variable and generally more enriched in ¹³C (?16‰ to ?11‰). Both natural tagging approaches agreed that most halibut (~75 %) enter PBE long after settlement (>?>?8–12 mm SL), although size-at-ingress estimates were significantly larger (mean difference = 27 mm; p?<?0.001) when derived via carbon SIR than with otolith geochemistry. Potential explanations for the differences in size-at-ingress estimates involve the magnitude of isotopic and trace element gradients at this ocean–estuary boundary, the temporal resolution of environmental tags stored within otoliths and soft tissues, and the size-at-capture or somatic growth rate of juvenile halibut. We conclude by discussing the relative merits of otolith geochemistry and SIR as natural tags, and by considering the implications of secondary dispersal into estuaries by post-larval fish.     

土壤和沉积物中22种有机氯农药和8种多氯联苯的气相色谱分析

近年来地下水、土壤和沉积物等介质中有机氯农药和多氯联苯分析方法的改善主要集中在样品前处理和分析测试条件等方面,而探讨布点、采样等方面的整套方法较少。本文建立了一套适用性较广的气相色谱法同时测定土壤和沉积物中22种有机氯农药和8种多氯联苯,方法检出限为0.09~0.48 ng/g,平均空白回收率为58.7%~133.7%。针对布点、采样、运输、保存、提取、净化、浓缩、仪器测试、数据处理和提交报告整个过程阐述了方法的有效性和实用性;并对提取、净化、测试等多个环节提供了两种或更多的选择,使方法具有更大的灵活性。本文提出,布点前应根据踏勘样品和前人资料考虑采集不同深度的样品;样品的布点、采集和制备均需选择样品,它们共同决定了样品的代表性;分析方法要灵活运用,对于很少检出的目标化合物可采用允许共峰但分析快速的方法,如果有检出再采用针对性的方法分别测定;样品的测定序列不应为了节约分析成本而过于简单。     

土壤/沉积物中石油烃微生物降解研究综述

结合目前国内外研究进展,综述了土壤和沉积物中石油烃污染物的来源、危害和生物降解的菌种及降解途径,分析了微生物性质和包括氧、营养物、温度、土壤/沉积物理化性质等环境因素对石油烃降解的影响,指出这些研究往往局限于某种特殊污染物、特殊污染降解菌种和单一条件下辅助降解方面,引入了人为因素的影响,造成与实际不符的降解假象。因此,自然条件下石油烃生物降解将成为重要的研究课题。     

Stable Sulfur Isotopic Evidence for Historical Changes of Sulfur Cycling in Estuarine Sediments from Northern Florida

Data on abundance and isotopic composition of porewater and sedimentary sulfur species are reported for relatively uncontaminated and highly contaminated fine-grained anoxic sediments of St. Andrew Bay, Florida. A strong contrast in amount and composition of sedimentary organic matter at the two sites allows a comparative study of the historical effects of increased organic loading on sulfur cycling and sulfur isotopic fractionation. In the contaminated sediments, an increase in organic loading caused increased sedimentary carbon/sulfur ratios and resulted in higher rates of bacterial sulfate reduction, but a lower efficiency of sulfide oxidation. These differences are well reflected in the isotopic composition of dissolved sulfate, sulfide, and sedimentary pyrite. Concentration and isotopic profiles of dissolved sulfate, organic carbon, and total sulfur suggest that the anaerobic decomposition of organic matter is most active in the upper 8cm but proceeds at very slow rates below this depth. The rapid formation of more than 90% of pyrite in the uppermost 2 cm which corresponds to about 3 years of sediment deposition allows the use of pyrite isotopic composition for tracing changing diagenetic conditions. Sediment profiles of the sulfur isotopic composition of pyrite reflect present-day higher rates of bacterial sulfate reduction and lower rates of sulfide oxidation, and record a profound change in the diagenetic cycling of sulfur in the contaminated sediments coincident with urban and industrial development of the St. Andrew Bay area.