Water quality impacts from mining in the Black Hills,South Dakota,USA

The focus of this research was to determine if abandoned mines constitute a major environmental hazard in the Black Hills. Many abandoned gold mines in the Black Hills contribute acid and heavy metals to streams. In some areas of sulfide mineralization local impacts are severe, but in most areas the impacts are small because most ore deposits consist of small quartz veins with few sulfides. Pegmatite mines appear to have negligible effects on water due to the insoluble nature of pegmatite minerals. Uranium mines in the southern Black Hills contribute some radioactivity to surface water, but the impact is limited because of the dry climate and lack of runoff in that area.     

A surface complexation model for cadmium and lead adsorption onto diatom surface

This work is devoted to the physico-chemical study of cadmium and lead interaction with diatom–water interfaces for two marine planktonic (Thalassiosira weissflogii = TW, Skeletonema costatum = SC) and two freshwater periphytic species (Achnanthidium minutissimum = AMIN, Navicula minima = NMIN) by combining adsorption measurements with surface complexation modeling. Reversible adsorption experiments were performed at 20 °C after 3 h of exposure as a function of pH, metal concentration in solution, and ionic strength. While the shape of pH-dependent adsorption edge is similar among all four diatom species, the constant-pH adsorption isotherm and maximal binding capacities differ. These observations allowed us to construct a surface complexation model for cadmium and lead binding by diatom surfaces that postulates the constant capacitance of the electric double layer and considers Cd and Pb complexation with mainly carboxylic and, partially, silanol groups. Parameters of this model are in agreement with previous acid–base titration results and allow quantitative reproduction of all adsorption experiments.     

Lithofacies succession of maar crater deposits in the Eifel area (Germany)

ABSTRACT Maar craters often contain exceptionally preserved fossils and maar sediments may reflect detailed environmental changes. Volcanosedimentary processes in a Middle Eocene maar crater lake are illustrated by the deposits of Eckfeld Maar in the Tertiary Hocheifel Volcanic Field (Rhenish Massif, Germany). The maar origin of the basin is evident from a circular negative gravity anomaly which indicates a low-density funnel-shaped basin filling. From the facies analysis of an Eocene (Eckfeld) and a Pleistocene (Döttingen) maar we develop a lithozone classification for the interpretation of maar sediments: syn-/post-eruptive breccias are followed by a fining-upwards sequence of lacustrine mud with coarse layers and final swamp deposits. From the facies analysis and regional geological data we reconstruct the pre- to post-eruptive history of a maar crater prior to post-Eocene uplift. These observations can be used for the interpretation of Tertiary and Quaternary maar craters that are ideal fossil and sediment traps.     

Distribution and sources of pre-anthropogenic lead isotopes in deep ocean water from FeMn crusts

The lead isotope composition of ocean water is not well constrained due to contamination by anthropogenic lead. Here the global distribution of lead isotopes in deep ocean water is presented as derived from dated (ca. 100 ka) surface layers of hydrogenetic Fe-Mn crusts. The results indicate that the radiogenic lead in North Atlantic deep water is probably supplied from the continents by river particulates, and that lead in Pacific deep water is similar to that characteristic of island and continental volcanic arcs. Despite a short residence time in deep water (80–100 a), the isotopes of lead appear to be exceedingly well mixed in the Pacific basin. There is no evidence for the import of North Atlantic deep water-derived lead into the Pacific ocean, nor into the North Indian Ocean. This implies that the short residence time of lead in deep water prohibits advection over such long distances. Consequently, any climate-induced changes in deep-water flow are not expected to result in major changes in the seawater Pb-isotope record of the Pacific Ocean.     

Graben generation of major sedimentary basins

Regional isostatic adjustment to the load that fills the trough of a large graben will produce a surface depression that extends far beyond the boundaries of the load. Sediment infilling of this depression can lead to the development of a major sedimentary basin as the regional adjustment mechanism approaches isostatic equilibrium.     

Metal content and environmental risk assessment around high-altitude mine sites

Gold mining activities in Apolobamba area, northwest of La Paz, Bolivia have created serious environmental concern and great risk to human health. The current methods used to extract gold are too primitive resulting in metal contamination of soil and water. The objectives of this study were to: (1) determine the degree of metal pollution, and (2) assess the risk to human health and environment in the Apolobamba area. Soil, water, sediment samples, and mine spills were collected and analyzed. Metals including Pb, Cu, Zn, Cd, and Hg concentrations were higher in surface soils than in subsurface soils indicating active atmospheric deposition of metals. Sediment samples had elevated levels of metals probably from mine spills discharged into the Sunchulli River. Surface soils in the Sunchulli community show the highest levels of Pb and Hg in all soil samples and may pose a risk to the health of the human population and environment.     

The groundwater geochemistry in a semi-arid, fractured crystalline basement area of Dodoma, Tanzania

The chemical character of groundwater is generated through processes including the leaching of surficial and near-surface soil salts, cation exchange and mineral dissolution of, in this case, mainly amphiboles and sodic plagioclase. Molar ratios thermodynamic analysis using a NETPATH geochemical model and standard Piper trilinear and Gibbs diagrams have been used to establish these geochemical processes. Though the groundwater is dominantly of NaCl type, it is apparently suitable for general irrigation purposes.     

Experimental Study of Factors Controlling Sorption of Heavy Metals on Ariake Clay and Implication for Practice

A series of batch tests have been presented to investigate the effects of solid-solution contact time, solid:solution ratio, and pH of solution on sorption of Cd²⁺ and Pb²⁺ on Ariake clay from Kyushu region of Japan. The results show that, among the three investigated factors, solid:solution ratio (SD/SN) seems to be the crucial controlling factor. The Freundlich sorption parameters determined from the batch tests were applied to a typical field landfill in which the Ariake clay was used as soil barrier. The impacts of the landfill were assessed by numerical analysis. Based on the analysis result, the significance of selecting proper solid:solution ratio for determining sorption parameters from batch test has been discussed.     

Spatial heterogeneity of epibenthos on artificial reefs: fouling communities in the early stages of colonization on an East Australian shipwreck

Artificial reefs are spatially complex habitats and serve as good model systems to study patterns of community succession and the response of epibiota to environmental clines over small spatial scales. Here, we quantified spatial heterogeneity in community composition and diversity of fouling communities across a number of environmental gradients that included water depth, surface orientation of habitats, exposure to currents, and shelter. Assemblage structure was quantified by spatially replicated photo transects on a recently scuttled large navy ship off the East Australian coast, lying in 27 m of water. A rich assemblage of epifauna had colonized the wreck within a year, dominated by barnacles, sponges and bryozoans. Community structure varied significantly over small spatial scales of meters to tens of meters. Depth, surface orientation and exposure were the major environmental drivers. Assemblages were substantially less diverse and abundant on the deepest (23 m near the seafloor) part of the hull with residual antifouling paint, on sheltered surfaces inside the wreck, and on the sediment‐laden horizontal surfaces. Overall, the wrecks’ habitat complexity corresponds with small‐scale heterogeneity in the fouling communities. This study supports the notion that wrecks enhance local diversity and biomass within the habitat mosaic of their location, and habitat complexity may be an important mechanism for this, as demonstrated by the large spatial variability in the assemblages documented here.