Relationships between heavy metals and iron oxides,fulvic acids,particle size fractions in urban roadside soils

Urban roadside soils are the “recipients” of large amounts of heavy metals from a variety of sources including vehicle emissions, coal burning waste and other activities. The behavior of heavy metals in urban roadside soils depends on the occurrence as well as the total amount. Accordingly, knowledge of the interactions between heavy metals and other constituents in the soil is required to judge their environmental impact. In this study, correlations of heavy metal concentrations (Pb, Zn, Cu, Ag, Se, Ni, Cr and Ba) to iron extracted using dithionite–citrate–bicarbonate (DCB) buffer (Fe_DCB), fulvic acids and particle size fractions were examined from the Xuzhou urban roadside soils. Heavy metals except for Cr and fulvic acids had a positive significant correlation with Fe_DCB, indicating these metals and fulvic acids are principally associated with the surfaces of iron oxides of the soils. Significant positive correlations were also found between the contents of fulvic acids and heavy metals, showing these heavy metals (especially for Cu, Ni and Cr) form stable complexes with fulvic acids. Such finding is of importance with regard to the increased mobilization of heavy metals, e.g., into freshwater ecosystems. Ag, Se and Cr are independent of particle size fractions because of their low concentrations of Ag and Se in the studied soils. Pb, Zn, Cu, Ba and Ag are mainly enriched in the finer soil particles (especially <16 μm).     

残坡积土壤层中铁锰氧化物的吸附特性及其地球化学找矿意义

作者用不同方法研究了粤北某铅锌矿区近矿灰岩风化土壤中铁锰氧化物对微量元素的富集作用。发现铁锰氧化物对Sb、Pb、Cd、Ni等元素具有强烈的吸附作用;对Zn、Cu等21种元素有程度不等的吸附;对Ti、Sr等12种元素不吸附。据此,作者认为在土壤地球化学找矿中,应着重在铁锰结核层和铁锰粘土层取样,或用编提取方法分析铁锰氧化物相的元素含量,强化异常,提高找矿效果。     

藏南查拉普金矿床载金矿物特征与金的赋存状态

黄铁矿和毒砂是卡林型和造山型金矿床重要的载金矿物。文章通过电子探针(EPMA)分析研究了藏南查拉普金矿床不同类型黄铁矿和毒砂中Au、As、S、Fe等元素的含量变化和分布规律,发现不同阶段的黄铁矿具有不同的结构特征和元素组成特点。沉积成岩期黄铁矿(Py1)主要呈草莓状、胶状,常构成环带状黄铁矿的核心,其中金的含量最高,显示了金在沉积成岩期的大量富集。热液期早阶段黄铁矿(Py2)主要呈自形-半自形的立方体,与Py1元素(S、Fe、As)组成相近,显示了一定的继承演化关系。热液期主阶段黄铁矿(Py3)与毒砂共生,多呈自形-半自形的五角十二面体、立方体,常包裹早期的黄铁矿形成环带结构。Py3中As的含量明显升高,其增加量近似等于S的减少量,说明As主要进入黄铁矿晶格替代了S的位置。各个阶段的黄铁矿和毒砂中Au的分布在EPMA微束的分辨率下均显示是不均匀的,Au在Py1和大部分Py2中主要以纳米级自然金(Au0)的形式存在;而在Py3中主要以(Au+)的形式存在,少部分以纳米级自然金(Au0)形式存在。Py1的结构及元素组成与典型卡林型金矿和造山型金矿沉积成岩期黄铁矿的特点相似,而Py3的大量发育则符合卡林型金矿的特征。     

Correlation of rhyolitic pyroclastic eruptive units from the Taupo volcanic zone by Fe–Ti oxide compositional data

Grain-specific analyses of Fe–Ti oxides and estimates of eruption temperature (T) and oxygen fugacity (fO₂) have been used to fingerprint rhyolitic fall and flow deposits that are important for tephrostratigraphic studies in and around the Taupo volcanic zone of North Island, New Zealand. The analysed Fe–Ti oxides commonly occur in the rims of orthopyroxene crystals and appear to reflect equilibrium immediately prior to eruption because of geochemical correlation with the co-existing glass phase. The composition of the spinel phase is particularly diagnostic of eruptive centre for post-65 ka events and can be used to distinguish many tephra beds from the same volcano. The 29 different units examined were erupted over a wide range in T (690–990°C) and Δ log fO₂ (–0.1 to 2.0). These parameters are closely related to the mafic mineral assemblage, with hydrous mineral-bearing units displaying higher fO₂. Such trends are superimposed on larger differences in fO₂ that are related to eruptive centre. At any given temperature, all post-65 ka Okataina centre tephra have higher fO₂ values than post-65 ka Taupo centre tephra. This provides a useful criterion for identifying the volcanic source. There are no temporal T and fO₂ trends in the tephra record; over intervals >20 ka, however, tephra sequences from Taupo centre form characteristic T-fO₂ buffer trends mirroring the glass chemistry. Individual eruptive events display uniform spinel and rhombohedral phase compositions and thus narrow ranges in T (± <20°C) and log fO₂ (± <0.5), allowing these features to identify individual magma batches. These criteria can help distinguish tephra deposits of similar bulk or glass composition that originated from the same volcano. Distal fall deposits record the same T-fO₂ conditions as the proximal ignimbrite and enable distal–proximal correlation. Lateral and vertical compositional and T-fO₂ variability displayed in large volume (>100 km³) ignimbrites, such as the Oruanui, Rotoiti and Ongatiti, is similar to that found in a single pumice clast and thus mainly reflects analytical error; however, thermal gradients of ca. 50°C may occur in some units. Received: 6 April 1998 / Accepted: 16 June 1998     

Occurrence,distribution and source of arsenic in deep groundwater wells in Maydavood area,southwestern Iran

Groundwater in some deep wells of Maydavood aquifer, southwestern Iran, contains relatively high concentrations of arsenic. Detailed hydrochemical analysis of these groundwaters (with ICP-OES instrument) showed that concentrations of iron, manganese, nickel, and vanadium are also high in them and concentrations of total arsenic in 81% of deep wells are greater than World Health Organization’s permissible value (10 ppb). XRF analysis of surrounding geological formations and aquifer sediments proposed that original source of arsenic in aquifer material can be attributed to minerals from Asmari Formation. It appears that a key mechanism for arsenic mobilizing to deep wells is microbial biodegradation of petroleum related organic matters (PROMs), which exist in aquifer sediments and originates from the bedrock of the aquifer (Gachsaran Formation). This process is followed by microbially mediated reductive dissolution of arsenic-bearing iron/manganese oxyhydroxides/oxides and further by nickel and vanadium mobilizing to groundwater. According to hydrogeochemical conditions and cluster analysis, water wells in Maydavood aquifer are divided to four subgroups: the wells with mildly reducing condition (subgroup I), moderately reducing condition (subgroup II), reducing condition (subgroup III), and high reducing condition (subgroup IV). Affected wells to arsenic are belonged to subgroups III and IV.     

浙江长兴大银山金矿成因探讨

受燕山中晚期地质构造运动和岩浆活动的影响 ,在中酸性侵入岩体与钙镁碳酸盐岩外接触带 ,大银山金矿体呈扁平透镜状产于侵入体的舌状端部。是中低温热液型含金矽卡岩矿床。研究其成矿地质条件和控因素 ,对找矿和成矿预测均有重要意义     

自然水体采集的生物膜上铁、锰氧化物的萃取分离

采用选择性萃取分离技术对自然水体采集的生物膜上铁、锰氧化物进行萃取分离研究,考察该技术的适用性。参考人工培养生物膜的萃取方法,分别用NH₂OH·HCl和Na₂S₂O₄为萃取剂选择性萃取生物膜上的锰氧化物和铁、锰氧化物。实验中分别依次只改变萃取剂浓度、萃取液酸度或萃取时间,保持其它两个因素不变,分别考察这三个因素对萃取效果的影响,从中选出对铁、锰氧化物萃取率高而对有机质影响小的条件为最佳条件。用选定的最佳条件对不同时间和地点采集的生物膜进行萃取,发现对目的组分的萃取率可达70.8%~94.6%,而对非目的组分的影响很小（3.3%~11.0%）,满足萃取分离的要求。这说明选择性萃取技术可以广泛应用于自然水体采集的生物膜上铁、锰氧化物的萃取分离。     

Characteristics of reactive nitrogen compounds and other relevant trace gases in the atmosphere at urban and rural areas of Korea during May–June, 2004

This study examines the general characteristics of reactive nitrogen oxides (NO_y) at urban and rural sites in terms of measurement- and modeling-based analyses. In this field study, NO_x at urban and rural sites were 92 and 89% of NO_y on average, respectively. HONO levels (e.g., 1.8 ppbv) at the urban site were significantly higher than those at the rural site by a factor of 4.5. HONO concentrations at the urban site during the night were clearly higher than those during the day, which were likely to result from heterogeneous reactions on the surfaces of airborne aerosols and/or grounds. In contrast, there were no significant differences of PAN concentrations in either the temporal or spatial distributions. The significantly low ratios of NO_z/NO_y at both sampling sites indicated a more limited chemical aging process in air mass. O₃ levels were weakly related to NO_x oxidation at both sites, especially at the rural site.     

陕西洛川黄土剖面的白度参数及其古气候意义

对陕西洛川黄土剖面的白度研究表明，黄土和古土壤存在明显的白度差别，表现为黄土的白度值较高，而古土壤的白度值较低，依据白度值可以清晰地区另出剖面中的黄土层和古土壤层。化学处理以及分粒级实验结果表明风化成壤作用造成细粒级铁氧化物的含量增高是古土壤中白度值降低的主要因素。洛川剖面白度值的变化与第四纪冰期－间冰期旋回的波动特征相一致，其逐渐增高的趋势与全球气候变冷总体趋势相吻合，表明白度在反映夏季风环流强度变化，以及对全球气候变化的响应问题上具有广泛的应用前景。     

招远市夏甸金矿含金流体成因及就位机制的研究

通过对夏甸金矿石英中流体包裹体成分和矿石微量元素测定,得出含金流体为幔源-岩浆和变质复合成因.依据容矿断裂形成机制的理论分析、高温高压实验研究、含金流体就位过程及容矿断裂形成环境的探讨,提出复合含金流体主动就位机制.