200 years of mining activities at La Paz/San Luis Potosí/Mexico - Consequences for environment and geochemical exploration

The Ag---Pb---Zn---Cu---Au mining district of Santa María de La Paz has been extensively exploited for approximately 200 years. Consequences of these activities are several deposits of tailings with high As and heavy metal concentrations, which are completely unstable. The climate is semiarid and as the dumps have no protective cover, material from the dumps is dispersed by strong winds. It is also washed out during seasonally heavy rainfalls. By these processes approximately 100 km² of surrounding have been contaminated by dump material. The As and heavy metal content of the soils was determined as well as their level in crops (Zea Maize) from agricultural lands in the vicinity of the dumps. In the direction of prevailing winds concentrations up to 1000 ppm Zn, 400 ppm Pb, 16 ppm Cd, 550 ppm Cu and 300 As have been detected in top soils. Using fuzzy cluster analysis the different contamination sources could be identified. Grains of corn from contaminated sites showed no critical concentrations, but leaves which are also used tor fodder, have As-concentrations up to 20 ppm.     

Mobility of heavy metals as a function of pH of samples from an overbank sediment profile contaminated by mining activities

Parts of the flood plains north of the Harz Mountains are contaminated with heavy metals, such as Pb, Cu, Zn and Cd derived from mining, which has been carried out in the Harz Mts. since the Middle Ages. It is important to know the mobility of the heavy metals in these overbank sediments in order to estimate the danger to the environment arising from this source. This paper deals with the effect of pH on heavy-metal mobility, using a constant-pH method. The investigations were carried out on an overbank sediment profile near Salzgitter Bad, north of the Harz Mts. The mobility of the heavy metals in the overbank sediment profile is described as a function of pH and depth. Besides the mobile heavy-metal fraction at a certain pH, the buffering capacity of the sediment at this pH must be taken into consideration. The different layers of the overbank sediment profile show distinct differences in buffering capacity and a natural pH harrier could be identified in the upper part of the profile. Therefore, to avoid increasing heavy-metal mobility the natural layering of the overbank sediment profile should not be disturbed. Two different kinds of desorption experiments at constant pH are also discussed, as well as the conversion of the heavy-metal species in the ore minerals into the species in the sediment.     

ICP—AES法同时测定高纯氧化钇中稀土及非稀土杂质元素方法研究

本文提出了用ＩＣＰ－ＡＥＳ法直接同时测定高纯氧化钇中１４个稀土和１６个非稀土杂质元素的分析方法，对被测元素的 谱线、氧化钇基本及背景影响进行了研究，用标准加入法测出氧化钇基准中的微量杂质元素，消除了由于忽略基准中的杂质元素含量给高纯氧化钇分析测定带来的误差，同时对工作条件进行了优化。方法中各被测元素的检出限为0.003～1.31ug/g，能够满足生产过程中的质量控制及进出口商品检验     

单道扫描电感耦合等离子体发射光谱法测定大洋标准物质中稀土元素

采用单道扫描等离子体发射光谱法测定了大洋多金属结核及深海沉积物中的稀土元素与钪，比较了不同功率下各稀土元素的检测限，研究了低功率下的稳定性，拟定了可靠的样品处理方法。方法经多金属结核及深海沉积物国家标准ＧＢＷ０７３１３、ＧＢＷ０７２４９分析验证，结果与标准值相符。测定精度（ＲＳＤ）在１３％～５３％。已用此法为第２批多金属结核和深海沉积物标准物质提供了定值数据，其结果无剔除值     

湖南省珍稀濒危植物及其特征

首批中国珍稀濒危植物分布于湖南的有65种4变种。从区系组成、植物地理分布、在自然森林群落中的生态地位,以及利用价值等方面分析了它们的特征,并对湖南珍稀濒危植物就地保护的有效性和措施进行了讨论。     

Rare earth and other trace element mobility during mylonitization: a comparison of the Brevard and Hope Valley shear zones in the Appalachian Mountains, USA

In progressing from a granitoid mylonite to an ultramylonite in the Brevard shear zone in North Carolina, Ca and LOI (H₂O) increase, Si, Mg, K, Na, Ba, Sr, Ta, Cs and Th decrease, while changes in Al, Ti, Fe, P, Sc, Rb, REE, Hf, Cr and U are relatively small. A volume loss of 44% is calculated for the Brevard ultramylonite relative to an Al–Ti–Fe isocon. The increase in Ca and LOI is related to a large increase in retrograde epidote and muscovite in the ultramylonite, the decreases in K, Na, Si, Ba and Sr reflect the destruction of feldspars, and the decrease in Mg is related to the destruction of biotite during mylonitization. In an amphibolite facies fault zone separating grey and pink granitic gneisses in the Hope Valley shear zone in New England, compositional similarity suggests the ultramylonite is composed chiefly of the pink gneisses. Utilizing an Al–Ti–Fe isocon for the pink gneisses, Sc, Cr, Hf, Ta, U, Th and M-HREE are relatively unchanged, Si, LOI, K, Mg, Rb, Cs and Ba are enriched, and Ca, Na, P, Sr and LREE are lost during deformation. In contrast to the Brevard mylonite, the Hope Valley mylonite appears to have increased in volume by about 70%, chiefly in response to an introduction of quartz. Chondrite-normalized REE patterns of granitoids from both shear zones are LREE-enriched and have prominent negative Eu anomalies. Although REE increase in abundance in the Brevard ultramylonites (reflecting the volume loss), the shape of the REE pattern remains unchanged. In contrast, REE and especially LREE decrease in abundance with increasing deformation of the Hope Valley gneisses. Mass balance calculations indicate that ≥95% of the REE in the Brevard rocks reside in titanite. In contrast, in the Hope Valley rocks only 15–40% of the REE can be accounted for collectively by titanite, apatite and zircon. Possible sites for the remaining REE are allanite, fluorite or grain boundaries. Loss of LREE from the pink gneisses during deformation may have resulted from decreases in allanite and perhaps apatite or by leaching ofy REE from grain boundaries by fluids moving through the shear zone. Among the element ratios most resistant to change during mylonitization in the Brevard shear zone are La/Yb, Eu/Eu*, Sm/Nd, La/Sc, Th/Sc, Th/Yb, Cr/Th, Th/U and Hf/Ta, whereas the most stable ratios in the Hope Valley shear zone are K/Rb, Rb/Cs, Th/U, Eu/Eu*, Th/Sc, Th/Yb, Sm/Nd, Th/Ta, Hf/Ta and Hf/Yb. However, until more trace element data are available from other shear zones, these ratios should not be used alone to identify protoliths of deformed rocks.     

Heavy metal retention in secondary precipitates from a mine rock dump and underlying soil, Dalarna, Sweden

This study investigates the retention of heavy metals in secondary precipitates from a sulfidic mine rock dump and underlying podzolic soils by means of mineralogical and chemical extraction methods. The rock dump, which is at least 50 years old, consists of a 5–10-cm-thick leached zone and an underlying 110–115-cm-thick accumulation zone. Optical microscopy and electron microprobe analyses confirm that pyrrhotite weathering has proceeded much further in the leached horizon relative to the accumulation horizon. The weathering of sulfides in the leached zone has resulted in the migration of most heavy metals to the accumulation zone or underlying soils, where they are retained in more stable phases such as secondary ferric minerals, including goethite and jarosite. Some metals are temporarily retained in hydrated ferrous sulfates (e.g., melanterite, rozenite). Received: 28 October 1996 · Accepted: 24 February 1997     

Electrokinetic remediation of metal contaminated glacial tills

This paper presents the results of an experimental investigation which studied the feasibility of using the electrokinetic process to remediate contaminated clays of glacial origin, otherwise known as glacial tills. An overview of the electrokinetic phenomena, as well as previously performed laboratory and field investigations, is first presented. The methodology of the electrokinetic experiments which were conducted to investigate the removal of metals from a glacial till is then described. A total of 16 experiments were conducted using glacial till samples obtained from a project site near Chicago. Sodium and calcium were used as the surrogate cationic metallic contaminants. These experiments demonstrated that ion transport during the electrokinetic process occurs due to both electro-osmosis and electromigration, but that due to electromigration is significantly higher than that due to electro-osmosis. Unlike other clays such as kaolinite, the glacial till used for this investigation possessed high buffering capacity because of its high carbonate content which prevented the acid front migration from the anode to the cathode during the electrokinetic process. The ion removal efficiency of the electrokinetic process was found to increase when: (1) the voltage gradient applied to the soil was increased, (2) the initial concentration of the contaminants was increased, and (3) the duration of the treatment process was increased. The ion removal efficiency was also greater for smaller ions which possess less ionic charge and when the ions existed independently in the soil as compared to when they coexisted. This investigation suggests that the electrokinetic process has significant potential for remediating glacial tills contaminated with metals. However, the properties of Na and Ca are not representative of contaminants, such as heavy metals, so further investigations are needed.     

磁学方法在环境污染研究中的应用

环境磁学方法问世20多年来，因其快速、灵敏、经济、无破坏性和信息量大的特点，在环境研究中得到广泛的应用。磁学方法可用于传统的污染分析技术（化学）之前的预研究，而后者一般耗费大量人力、物力和时间；它也可以作为环境污染评估的代用指标。近年来，随着世界环境污染问题的日益严重和倍受关注，磁学方法被广泛地应用于环境污染研究。欧洲环境磁学专家在重建污染历史、监测现代环境污染、追踪与分离污染源等方面，开展了大量的工作，并积累了一定的经验。介绍了磁学方法用于污染研究的显著特点、主要用途、野外工作方法以及相关仪器；展示了在大气、土壤、潮滩、河流、湖泊以及海洋等不同环境系统中，利用磁手段研究污染的成果和最新进展；对 于一些难点、热点问题，如磁性机理的研究、多源污染的分离、强烈多变的人类活动对获取有意义磁讯号的影响等，做了相应的分析和总结。     

Bathymetric and geochemical investigation of Kawah Ijen Crater Lake, East Java, Indonesia

A bathymetric survey of Kawah Ijen crater lake was conducted by acoustic sounding in 1996 to compare the lake morphology with those measured in 1922, 1925 and 1938, and to calculate the present lake volume. Even though the lake experienced several hydrothermal eruptions, the maximum depth became shallower (182 m) than before (200 m), resulting in a reduced lake volume (3.0×10⁷ m³).Fifty-two major and minor constituents including rare earth elements and polythionates (PT) of the lake waters at various depths were determined by ICP-AES, ICP-MS and HPLC, respectively. These ions except for several volatile elements are taken up by lake fringe through congruent dissolution of pyroclastics of Kawah Ijen volcano. Most ions are homogeneously distributed throughout the lake, although PT showed a considerable vertical variation. Rare earth elements (REE) in the Kawah Ijen water as well as those from other hyper-acidic crater lakes show distribution patterns likely due to the three rock dissolution (preferential, congruent and residual) types, and their logarithmic concentrations linearly depend upon the pH values of the lake waters.Using the PT degradation kinetics data, production rates of PT, injection rates of SO₂ and H₂S into the lake were estimated to be 114, 86 and 30 tons/day, respectively. Also travel time of the spring water at the Banyupahit Riverhead from Kawah Ijen was estimated to be 600–1000 days through the consideration of decreasing rates of PT. Molten sulfur stocks containing Sn, Cu, Bi sulfides and Pb-barite exposed on the inner crater slope were presumed to be extinct molten sulfur pools at the former lake bottom. This was strongly supported by the barite precipitation temperature estimated through the consideration of the temperature dependence of Pb-chlorocomplex formation.