bluuebunny/crossref_metadata_2025 huggingface dataset:
Naturally occurring Cr
6+
in shallow groundwaters of the Yilgarn Craton, Western Australia
Authors: Gray David J.
Published: March 2005

Hydrogeochemical investigations of the Yilgarn Craton and its margins have been dominantly in areas of deep (20–100 m) regolith, within unconfined aquifers where water tables are commonly 10–60 m below surface. These groundwaters contacting weathered Archaean rocks have a surprising (on the basis of its normal aqueous chemistry) lack of correlation between Cr content and acidity. Trivalent Cr has a soluble chemistry similar to that of Al, being extremely insoluble under neutral conditions, with appreciable solubilities only below pH 4. In contrast, dissolved Cr concentrations in the studied Yilgarn groundwaters can be very high, with no pH relationship, and are strongly correlated with the presence of ultramafic rocks. Groundwaters in contact with fresh and weathered ultramafic rocks contain consistently high (0.01–0.43 mg l
−1
) dissolved Cr concentrations, whereas waters in contact with other lithologies have Cr concentrations below detection (< 0.005 mg l
−1
). This effect is highly robust at the Yilgarn sites tested and offers a potential method for recognizing the presence of ultramafic rocks, even where they are intensely weathered.

If the dissolved Cr were present as Cr
3+
, those groundwaters with Cr concentration greater than 1 μg l
−1
and pH above 6 would be strongly over-saturated with respect to secondary Cr oxides. Comparison of ICP-AES and spectrophotometric analyses indicate that Cr in these groundwaters is present as Cr
6+
(i.e. CrO
4
2−
), which has a much higher solubility than Cr
3+
. A high oxidation state of dissolved Cr is also suggested by its highly anti-pathetic relationship with dissolved Fe, possibly due to the capacity of dissolved Fe
2+
to reduce CrO
4
2−
to the less soluble Cr
3+
ion. A similar anti-pathetic relationship is observed between dissolved Cr and Mn. In non-reducing (i.e. Fe– and Mn–poor) groundwaters, CrO
4
2−
will be relatively stable and potentially mobile. However, the mechanism by which CrO
4
2−
is released into groundwater is not known.

These naturally occurring concentrations of dissolved Cr
6+
are, in many cases, well above the WHO maximum concentration allowed in drinking water (0.05 mg l
−1
). In at least one area (Lawlers mining district, Western Australia), otherwise potable groundwaters cannot be used for human consumption due to concentrations of Cr
6+
up to six times greater than that allowable.
Environmental geochemistry of the Mt Perry copper mines area,SE Queensland, Australia
Authors: Ashley P.M. , Lottermoser B.G. , Chubb A.J.
Published: March 2005

Intermittent mining and processing of sulphide ore (pyrite–chalcopyrite) at the abandoned Mt Perry mine from the 1870s has resulted in numerousmine workings, waste dumps, a local drainage system contaminated by acid mine drainage (pH 3.3–4.5) and degradation of local soil and vegetation. Weatheringof sulphidic ore, oxidized waste material, tailings and slags (median of 32 samples: 0.65 ppm Au, 17 ppm Ag, 48 ppm As, 3090 ppm Cu, 3.5 wt% Fe, 138 ppm Mn, 19 ppm Mo, 55 ppm Pb, 39 ppm Zn) has led to the formation of secondary minerals (e.g. goethite, hematite, Cu carbonates, gypsum, jarosite, natrojarosite, chalcanthite) on waste materials, stream sediments and stream banks. Waters emanatingfrom underground workings and draining waste dumps have pH values as low as 3.3 and contain elevated contents of As, Cu, Fe, Zn and SO
4
. Dilution from uncontaminated tributaries and groundwaters causes decreasing Cu and Zn concentrations in stream waters, whereas Fe and As precipitate close to the mine site due to adsorption and coprecipitation processes. While much of the dissolved metal load derives from the mine site, Cu is also dissolved out of contaminated stream sediments. Soils in the mines area have elevated Cu and Fe values compared to background soils. The soils acquired their metal enrichments by hydromorphic dispersion from the dissolution of metal-rich particulates, transport of dust and physical erosion of metal-rich particulates from the dumps, and perhaps atmospheric fall-out from smelting plant emissions. Levels of Ag, As, Cu, Fe, and Zn in the fine fraction of stream sediments exceed background values by one to three orders of magnitude. This enrichment has been caused by physical erosion of metal-bearing minerals from abandoned ore and waste dumps and adsorption and coprecipitation of dissolved metals and metalloids in the stream bed. Areas disturbed by mining are characterized by lack of native vegetation, selective and non-selective bioaccumulation of metals and metalloids into plants (gold fern
Pityrogramma austroamericana
; hickory wattle
Acacia aulococarpa
; bunch speargrass
Heteropogon contortus
; wiregrass
Aristida benthamii
,
A. caput-medusae
), and partial recolonization by metal-tolerant plant species (gold fern; bunch speargrass; couch grass,
Cynodon dactylon
; swordsedge,
Lepidosperma
sp.).
Chemostat-controlled selective leaches of model soil phases – the hydrous manganese and iron oxides. Part 2: re-adsorption studies
Authors: Nolan Annette L. , Baltpurvins Karlis , Hamilton Ian C. , Lawrance Geoffrey A.
Published: March 2005

Selective leaching of synthetic Mn and Fe oxide phases was examined using a Chemostat to control the system temperature, pH and reductant concentration or Eh. Reaction conditions for the selective dissolution of model phases of Mn oxide (birnessite, ‘MnO
2
’), amorphous Fe oxyhydroxide (ferrihydrite, Fe(OH)
3
.
x
H
2
O) and crystalline Fe oxide (hematite/goethite, Fe
2
O
3
/FeOOH) were examined, concomitant with the behaviour of dopant metals Cu, Pb and Zn, present at concentrations of 1000 mg kg
−1
each. Part 1 of this study focused on achieving quantitative dissolutions of the target model phases within short reaction times (≤15 min) for the purpose of high-throughput field procedures. In this study, the behaviour of the doped trace metals during the selective extractions was examined. Selective extraction protocols were developed that attempt to optimize both the bulk phase dissolution and the selectivity of the doped trace metals hosted by particular phases. The behaviour of the doped trace metals suggests that trace metal selectivity is limited with respect to both re-adsorption onto and extraction from residual phases. Significant re-adsorption of extracted trace metals occurred under the necessarily milder conditions required for selective dissolution of Mn oxide (pH >3). At pH 5, 95% of Pb, 52% of Cu and 6% of Zn extracted from the Mn oxide phase re-adsorbed onto the residual amorphous Fe oxide phase. Partial extractions attempting to achieve selective dissolution of the Mn oxide phase and its associated trace metals must therefore be treated with caution. Selective extractions of soil samples from four different mineralized areas, employing the extraction conditions found to provide optimal selectivity, exhibited much slower dissolution kinetics for the bulk oxide phases, particularly for amorphous Fe oxide, in comparison to the model phases. Reaction times of ≤2 h are unlikely to be quantitative for amorphous Fe oxide extractions under these conditions; however, this leach is considered to be more robust than Mn oxide extractions.
An integrated mineral exploration programme in the Takengon tenement, Aceh magmatic arc, north Sumatra
Authors: Mulja Thomas , Collins Michael , Wong Henry H. , Rizal Rifqi , Brown Tyson , Zainuddin Muharis
Published: March 2005

A multidisciplinary approach led to the discovery of several gold and base metal occurrences during the 1996–1998 exploration campaign in the Takengon tenement of the Aceh magmatic arc, north Sumatra. Mineralization types included: (i) Au + base metal-bearing quartz veins; (ii) porphyry Cu-style mineralization; (iii) skarn-like Au and Cu-sulphide mineralization; and (iv) granite-hosted molybdenite veins. Regional structural interpretation of synthetic aperture radar and Landsat Thematic Mapper satellite images revealed prominent NNW–SSE and NNE–SSW trending fault zones that cross-cut the region and that were later shown to be spatially related to mineralization. Results from stream sediment analyses delineated several areas that were anomalous in Au±Cu, Pb, Zn, Mo and As, and mineralized bedrock was encountered in some of these areas during a subsequent lithogeochemical survey. An airborne geophysical survey defined a broad region characterized by a low magnetic response with locally high magnetic relief, and moderate to high potassium (K) but low thorium (Th) counts. In addition, the geophysical signals outlined smaller isolated areas that exhibit moderate magnetic anomalies and variable low to high K values. An integrated map with superimposed geological, geochemical and geophysical data demonstrates that results from the various prospecting techniques were generally complementary. Where mineralized and altered rocks occur, the adjacent sediments are metal-bearing (Au±Cu±Pb±As) and the geophysical responses are magnetic, and moderately to highly radioactive (K). In one case in which stream sediments were not auriferous, the discovery of Au- and base-metal-bearing quartz veins was possible through a combined exploration approach consisting of pathfinder elements (As and Pb), elliptical magnetic lineament, moderate to high K anomalies, and regional structures.
Mobility of palladium in the surface environment: data from a regional lake sediment survey in northwestern Ontario
Authors: Cameron Eion M. , Hattori Kéiko H.
Published: March 2005

This paper describes part of a project to examine geochemical methods in exploration for Pd deposits in northwestern Ontario. Palladium is one of the platinum group elements (PGE) that is mobile in dilute surface waters as hydroxy complexes, a feature that can facilitate its use in exploration. Earlier studies around the Lac des Iles Pd mine have shown that Pd is widely dispersed in solution even from sulphide-poor mineralization (
Hattori & Cameron 2004
). The region that includes Lac des Iles has been covered by a lake sediment survey by the Ontario Geological Survey (
Dyer & Russell 2002
). These lake sediment data provide a further means of better understanding the geochemistry of Pd in the surface environment and its application to exploration for PGE deposits. Factor analysis of the lake sediment data reveals three associations: Factor 1, an association of Cr, Co, Ni, Pt and Pd; Factor 2, an association of Pd, S and As; and Factor 3, an association of Cu, Ag and Au. High scores for Factor 1 extend for 10 km down-ice from the mineralized mafic rocks of Archean age at Lac des Iles and reflect the dispersion of clastic material by ice sheets, supplemented by hydromorphic dispersion. High scores for Factor 2 are much more widespread and are spatially associated with Quaternary glaciofluvial deposits, notably eskers. A plot of Pd alone in lake sediments throughout the area largely reflects this association with eskers. The elemental assemblage of Factor 2 originates from the leaching of fragments of Nipigon diabase (Pd) and Sibley sedimentary rocks (S, As), both of Proterozoic age, contained within the eskers. The high permeability of the eskers permits soluble elements to be leached. All three elements, Pd, S and As, form neutral and anionic complexes and are not adsorbed by negatively-charged iron oxyhydroxide colloids and coatings, which restrict the dispersion of elements that dissolve as cations, such as Cu, Ni and Co. Factor 3, Cu, Ag and Au, occurs in areas of Proterozoic bedrock.
Redox, pH and SP variation over mineralization in thick glacial overburden. Part I: methodologies and field investigation atthe Marsh Zone gold property
*
Authors: Hamilton S.M. , Cameron E.M. , McClenaghan M.B. , Hall G.E.M.
Published: March 2005

A surface and subsurface investigation of pH, oxidation–reduction potential (ORP) and spontaneous potential (SP) was carried out over sulphide-hosted gold mineralization in an area of thick and extensive glacially derived overburden. Protocols were developed to measure ORP and pH in clay slurries, peat and groundwater to test for the presence of redox and pH phenomena that were predicted to occur over mineralization. ORP protocols focused on removing memory effects caused by probe history and storage and on obtaining a reproducible measure of the ORP over mineralization relative to background areas. The results confirm the presence of distinct reduced ‘columns’ in clay and interstitial groundwater overlying sulphide mineralization that are in fact reduced ‘curtains’ that follow the trace of mineralization. These are accompanied by high pH within the reduced column, with minor lows on the flanks, and elevated H
2
S and CO
2
in shallow groundwater over mineralization. Whereas the H
2
S appears to have its source in bedrock mineralization, the CO
2
is likely a secondary near-surface phenomenon related to oxidation of metals in the reduced column, which produces acid and concomitant dissolution of carbonate in the clays. Wide groundwater temperature anomalies are spatially associated with mineralization. High ORP in shallow peat above mineralization may be evidence of an ‘oxidized cap’ over the reduced column. A minor SP response in surface peat was noted but is small in comparison to the redox field voltage
.
The presence of reduced columns and other features are consistent with a previously published redox-gradient transport model.
Orientation biogeochemical prospecting studies in Ireland
Authors: Smyth Dermot
Published: March 2005

Since the 1960s orientation geochemical prospecting studies conducted in Ireland have included atmogeochemical, hydrogeochemical and biogeochemical sampling. Results have indicated their potential usefulness in the detection of mineralized localities and the delineation of geological structure and lithology. Recently, orientation biogeochemical prospecting studies have been conductedat the Curraghinalt gold deposit and the Carlingford Cu–Ni–PGE prospect. At Curraghinalt a sample of gorse (
Ulex europaeus
) collected in a locality of lode gold mineralization contained 10.3 ppb Au (dry weight) in bark tissue. Data indicate that gorse is a viable sample medium for biogeochemical prospecting in this area. At Carlingford grab samples of Bell heather (
Erica cinerea
) collected during a BHP-Billiton soil geochemical survey contain elevated Au, Co, Cr, Cu, Ni and Zn in the vicinity of geological faults. Preliminary studies indicate that biogeochemical prospecting may be a viable alternative to soil geochemical surveys in rugged terrain due to the speed and ease of biogeochemical sampling.
Evaluation of a method for identification of host physico-chemical phases for trace metals and measurement of their solid-phase partitioning in soil samples by nitric acid extraction and chemometric mixture resolution
Authors: Cave Mark R. , Milodowski Antoni E. , Friel Ellen N.
Published: March 2005

A sequential extraction methodology, designed to measure the solid phase partitioning of metals in soils and sediments, is described. The method uses centrifugation to pass increasing concentrations of HNO
3
through the sample, followed by ICP-AES analysis of major and trace elements of the extracts. A data-processing algorithm is used to identify the number of physico-chemical components extracted, their composition and the proportion of each in each extract. The algorithm has been successfully tested on a synthetic data set and the combination of the extraction methodology and data-processing algorithm have been tested on a contaminated soil sample (NIST SRM 2710).

The 14 extracts from each duplicate experiment were analysed for 19 elements and data analysis identified nine chemically distinct soil components: pore-water residual solutes; organic, easily exchangeable; a Cu–Zn dominated phase; a Pb-dominated phase; amorphous Fe oxide/oxyhydroxide; crystalline Fe oxide; Fe–Ti oxide; and Mn oxide.
Metal partitioning in soil profiles in the vicinity of an industrial complex, New South Wales, Australia
Authors: Martley Elizabeth , Gulson Brian , Louie Honway , Wu Michael , Di Ping
Published: March 2005

The industrial complex of Port Kembla, NSW, Australia comprises a copper smelter, steelworks and associated industries. As part of an investigation into the regional extent of a suite of metals in soils, sequential extraction was undertaken in selected soil profiles. A single aqua regia extraction and a six-step sequential extraction procedure were applied to soil samples at six different horizons to a depth of 50 cm from: (i) a contaminated, disturbed site located about 70 m from a major point source (C1); (ii) a contaminated undisturbed area situated 1 km from the contamination source (C2); and (iii) an uncontaminated, undisturbed area located 22 km from the complex (C3). Cadmium, Cr, Cu, Pb and Zn were determined by inductively coupled plasma mass spectrometry (ICP-MS) and ICP atomic emission spectrometry (ICP-AES). In the uncontaminated soil profile, metals were preferentially bound to the less mobile fractions (crystalline Fe oxides, sulfides and organic matter) except for Pb, which was preferentially bound to hydrous Fe–Mn oxides. Metal partitioning was relatively constant with depth, except for Zn. In the contaminated undisturbed soil profile (C2), the proportion of mobile metals decreased with depth. Metal partitioning at the lower levels was similar to that of core C3. At the surface, Cr was found in the sulfides and organic matter fractions, and Cu was preferentially bound to hydrous Fe–Mn oxides, crystalline Fe oxides, and sulfides and organic matter. Lead was preferentially bound to carbonates, and Zn was fairly evenly distributed among the different fractions. In the contaminated disturbed soil profile, a large proportion of metals were found in the labile forms to a depth of 40–50 cm. Based on the assumption that the mobility of metals decreases in the order of the extraction sequence, the difference in mobility amongst metals in the three soil cores measured in this study were in the order: (Cd) > Zn ≈ Cu > Pb > Cr. The two contaminated sites may represent potential health and environmental hazards because of their high soluble metal content and hence a site-specific investigation is required.
Mercury and antimony in soils and non-vascular plants near two past-producing mercury mines, British Columbia, Canada
Authors: Plouffe A. , Rasmussen P.E. , Hall G.E.M. , Pelchat P.
Published: March 2005

Mercury and Sb in soils (humus, B horizon, C horizon) and environmental biomonitors (moss and epiphytic lichen) were examined near two past-producing Hg mines located in British Columbia, Canada: Pinchi Lake and Bralorne Takla mines. Sequential extraction analyses and scanning electron microscopy were used to determine the chemical associations of Hg and Sb and the mineralogical forms of Hg in soils. Mercury and Sb in the C horizon are derived mostly from natural sources because their concentrations are controlled by the bedrock geology, glacial transport, and sediment types. Distribution of Sb in the B horizon is similar to that of the C horizon suggesting a common geogenic source. Mercury in the B horizon at Pinchi Lake mine could be derived in part from anthropogenic sources, because (1) only at that site, and not at any other sites of cinnabar occurrences in bedrock, is there a labile Hg enrichment in the B compared to the C horizon, and (2) there is a weak correlation between non-labile Hg concentrations in the B horizon and distance from the mine which occurs independently of the natural concentrations of the C horizon. Mercury and Sb concentrations in humus near Pinchi Lake mine (<10 km) appear to be derived in part from anthropogenic sources because there are strong correlations between labile and non-labile Hg and Sb concentrations with distance from the mine which occurs independently of natural concentrations in the C horizon. Near Pinchi Lake mine, biogeochemical cycling and gaseous Hg derived from the substrate are thought to be minimal pathways and sources of Hg to the humus compared to anthropogenic sources, otherwise the strong Hg enrichment in the humus compared to the C horizon only observed near Pinchi Lake mine would also be present at several sites of cinnabar occurrences in bedrock along Pinchi Fault. Anthropogenic Hg and Sb enrichment in the soils near Bralorne Takla mine is indistinguishable from natural enrichment. Mercury and Sb levels in the sampled moss and lichen species reflect locally derived wind-borne soil and rock dust.
Comparison of geochemical data derived from till and lake sediment samples, Labrador, Canada
Authors: Rencz A. N. , Klassen R. A. , Moore A.
Published: March 2005

Techniques for combining geochemical data from a till survey (2438 samples) and a lake sediment survey (17 447 samples) are assessed to determine a rigorous method for comparing the two sampling media. This study is based on five elements, (Cu, Ni, Fe, Pb and Zn) from overlapping geochemical surveys in Labrador, Canada. Two methods for comparing the till and lake sediment geochemical data are: (1) gridding and (2) nearest neighbour. Pearson correlation coefficients between media are low (<0.2) for Cu, Fe and Zn and only Ni has a correlation significant at the 95% confidence level (r
2
 = 0.45). Results from gridding show slightly higher correlations. Differences are most evident at the extremes, as anomalously high element concentrations in one medium typically do not correlate with high values in the other medium. Correlations between media increase as distance decreases for Ni, Pb and Zn; however, no such trend is evident for Cu or Fe. The nearest neighbour method has several advantages: this procedure retains the original data and it permits calculation of statistics such as distance and direction between the points. The differences between the geochemical results from the two media highlight the synergistic value of multi-media geochemical sampling.
Indicator mineral and till geochemical dispersal patterns associated with the Ranch Lake kimberlite, Lac de Gras region, NWT, Canada
Authors: McClenaghan M. B. , Ward B. C. , Kjarsgaard I. M. , Kjarsgaard B. A. , Kerr D. E. , Dredge L. A.
Published: March 2005

The Ranch Lake kimberlite, in the Contwoyto Lake area of the northwest Territories, consists of volcaniclastic crater facies kimberlite which contains thousands of kimberlite indicator mineral grains in a 10 kg sample. Cr-diopside and pyrope are the most abundant indicator minerals in the kimberlite, accompanied by much less abundant chromite and rare Mg-ilmenite. Indicator minerals in till samples collected around the Ranch Lake kimberlite define a spectacular ribbon-shaped glacial dispersal train trending west for 70 km. At its head, the train is 500 m wide and gradually widens 2 km at 20 km down-ice. The lateral edges of the train are sharply defined by the presence or absence of indicator minerals in till. Background (up-ice) concentrations of all indicator minerals are zero. Patterns for Cr-diopside and pyrope abundance are similar and concentrations increase down-ice, reaching their highest levels between 15 and 19 km down-ice. Of the two size fractions of heavy minerals examined, most indicator minerals occur in the finer, 0.25 to 0.5 mm, size fraction. The <0.063 mm fraction of the till matrix displays weak geochemical signatures of the kimberlite down-ice, most notably for Ba, Cr, Ce and Th. The results of this study of indicator mineral and geochemical methods around a known kimberlite will aid in the design of mineral exploration programs for kimberlite-hosted diamond deposits in glaciated terrain around the world.
Comparison of Cu–Hg–Ni–Pb concentrations in soils adjacent to anthropogenic point sources: examples from four Canadian sites
Authors: McMartin Isabelle , Henderson Penny J. , Plouffe Alain , Knight Ross D.
Published: March 2005

The extent and variation of Cu, Hg, Ni, and Pb loading in soil profiles (humus, B-horizon, C-horizon) were examined in the vicinity of four Canadian industrial sources of airborne metal particulates located in different ecozones and geological terrains: the Cu smelter at Rouyn-Noranda, Québec; the Cu-Zn smelter at Flin Flon, Manitoba; the Pb–Zn smelter at Trail, British Columbia; and the inactive Pinchi Lake Hg Mine, British Columbia. Three major controlling factors on the metal concentrations in soils have been assessed: (1) distance from the anthropogenic point source, (2) organic matter content, and (3) geology of the substrate. Distance from source largely controls smelter-related metal concentrations in humus, with concentrations decreasing with increasing distance according to specific parameters for each element and at each location. In the B-horizon, variations in organic matter content and substrate geology are important controls on metal concentrations, except in areas close to the source where sub-surface contamination was recognized for certain metals. The metal content of the C-horizon is predominantly determined by the nature and composition of the substrate. Variations in humus/C-horizon and B-horizon/C-horizon metal ratios are useful to help distinguish anthropogenic from natural sources of metal enrichments in soils.
Mushrooms from two metal-contaminated areas in Norway: occurrence of metals and metallothionein-like proteins
Authors: Collin-Hansen C. , Yttri K. E. , Andersen R. A. , Berthelsen B. O. , Steinnes E.
Published: March 2005

This study tested the hypothesis that concentrations of metallothionein-like (MT-like) proteins in fruiting bodies of wild-growing macrofungi reflect exposure to the metals Cd, Cu and Zn. Screening for these proteins was done by taking 44 samples of seven species of macrofungi from two metal-polluted areas in Norway, namely Odda and Sulitjelma. Concentrations of Cd, Cu and Zn were measured in fruiting bodies and topsoil, the highest of which were observed in fruiting bodies – 126 μg g
−1
for Cd, 427 μg g
−1
for Cu and 396 μg g
−1
for Zn. A large intra- and inter-specific heterogeneity in metal uptake was displayed between fruiting bodies from the same soils. Cd,Zn–MT-like proteins were detected in all samples, except one stipe of
Boletus edulis
, whereas only 72% of the samples contained detectable levels of Cu–MT-like proteins. However, concentrations of MT-like proteins did not reflect variations in metal concentrations. Low content of cysteine in Cd-binding protein fractions from
Amanita muscaria
collected in Odda indicates that no proteins of the metallothionein family were present in this species. Onthe contrary, these protein fractions share several characteristics with cadmium–mycophosphatins.
Copper tolerance testing in populations of

Mimulus luteus

var.

variegatus

exposed and non-exposed to copper mine pollution
Authors: Ginocchio R. , Toro I. , Schnepf D. , Macnair M. R.
Published: March 2005

Several plant species have evolved metal tolerance as a response to increasing metal concentration in soils due to human activities. A well-described example is the evolution of copper-tolerant ecotypes of the monkey flower (
Mimulus guttatus
) in Copperopolis, California. Although copper mine activities have been intense in some areas of the Andes Range in central Chile, metal-tolerant ecotypes have not been reported for any native or endemic plant species. Copper tolerance of two populations of
Mimulus luteus
var.
variegatus
from pristine basins (Río Cipreses and Las Cayanas) and one population from a highly polluted copper mine area (Sewell) were tested to determine their copper tolerance. Tolerance was tested on cuttings collected in the field from adult plants (Sewell population) and on cuttings from plants cultivated from seeds in the laboratory (Río Cipreses, Las Cayanas and Sewell). All cuttings were grown under increasing concentrations of copper (0, 0.5 and 2.0 mg l
−1
) in calcium nitrate (0.5 g l
−1
). Results indicated that root number and length were strongly inhibited in
M. luteus
var.
variegatus
from Río Cipreses and Las Cayanas, but tolerant individuals were found in the Sewell population. The degree of copper tolerance of
M. luteus
var.
variegatus
from Sewell was, however, lower than that of individuals of
Mimulus guttatus
from Copperopolis.
Elemental mercury in copper, silver and gold ores: an unexpected contribution to Lake Superior sediments with global implications
Authors: Kerfoot W. Charles , Harting S. L. , Rossmann Ronald , Robbins John A.
Published: March 2005

Mercury and copper inventories are low in central Lake Superior and increase markedly towards the Keweenaw Peninsula. Total copper flux to Lake Superior sediments averages 5.0 ± 2.5 μg cm
−2
 year
−1
(mean ± 95% confidence limits), whereas mercury flux averages 7.5 ± 4.2 ng cm
−2
 year
−1
. In the Keweenaw Peninsula region, copper, mercury and silver inventories are elevated and highly correlated. High copper, silver and mercury inventories can be traced back to shoreline stamp sand piles, the parent ores and to smelters. Mercury occurs in elemental form, probably as a natural amalgam, in native metal (copper, silver, gold) deposits and was liberated as volatile Hg
0
during on-site copper smelting. Stamp mills discharged at least 364 Mt of ‘stamp sand’ tailings, whereas smelters refined 5 Mt of native copper, liberating together at least 42 t of mercury. The Keweenaw situation is not unique, as mineral-bound mercury is commonplace in US and Canadian Greenstone Belts and is of worldwide occurrence in massive base metal ores.
Nickel and copper tolerance of phytoplankton isolated from a recovering lake near Sudbury, Canada
Authors: Woodfine D. G. , Havas M. , Acreman J.
Published: March 2005

The current study compares the tolerance, to Ni and Cu, of three species of phytoplankton,
Urosolenia eriensis
,
Cosmarium minimum
and
Scenedesmus acutus
, isolated from Alice Lake, Sudbury, Canada. An attempt was made to determine if metal tolerance is related to the presence and abundance of these species in the lake. Alice Lake was subjected to 60 years of Ni and Cu pollution from a nearby Ni–Cu smelter. After the closure in 1972, the air quality improved immediately and water quality began to improve by the late 1970s and early 1980s. Phytoplankton, which had been all but absent from the lake, had reappeared by the mid-1980s. Metal tolerance was measured in defined media allowing the computer modelling of speciation described as ‘free’ Ni and Cu. Nickel tolerance was compared with ambient lake water concentrations and the presence of each species. The order of tolerance for Ni was
U. eriensis
 > 
C. minimum
 > 
S. acutus
. All species had similar tolerance to Cu. Differences in tolerance alone did not explain the shifts in species dominance within Alice Lake. These results emphasize the difficulties with using laboratory trace-metal tolerance estimates to interpret ecological field observations.
Mercury contamination from historic mining in water and sediment, Guadalupe River and San Francisco Bay, California
Authors: Thomas Martha A. , Conaway Christopher H. , Steding Douglas J. , Marvin-DiPasquale Mark , Abu-Saba Khalil E. , Flegal A. Russell
Published: March 2005

The New Almaden mercury mines in California (USA), which collectively represent the largest historic producers of mercury in North America, are a persistent source of mercury contamination to the San Francisco Bay estuary. An estimate based on total mercury concentration (Hg
TOT
) and provisional stream flow data measured at a gauging station in the Guadalupe River during base flow conditions yields a base flow flux of 30 g of mercury for the month of October 2000. In contrast to this base flow estimate, one 2-day rain event in October 2000 resulted in a flux of 22 g of mercury past this site. An estimate of mercury transport from the entire Guadalupe River watershed based on a sediment transport model and our measured suspended particulate Hg
TOT
(0.5–4 μg g
−1
) results in a total of 4–30 kg year
−1
transported to the southern reach of the estuary. Sediments in the southern reach have lower Hg
TOT
(most ≤0.4 μg g
−1
dry wt) and monomethylmercury (MMHg,
c.
1 ng g
−1
dry wt) concentrations than those in the Guadalupe River (Hg
TOT
, 0.41–33 μg g
−1
dry wt; MMHg, 1–10 ng g
−1
dry wt). Because the most elevated methylmercury concentrations (8–12 ng g
−1
dry wt) were found in sediments deposited immediately upstream of hydraulic structures (e.g. diversion dams and weirs) within the river, it is proposed that such physical structures may represent important zones of MMHg production and fluxes to San Francisco Bay.
Estimation of mercury and other heavy metal contamination in traditional gold-mining areas of Transbaikalia
Authors: Laperdina Tatyana G.
Published: March 2005

Contamination of the traditional gold-mining areas of Transbaikalia (Russia, Siberia) is described. To estimate the placer gold-mining impact on the ecological quality of river waters, extensive investigations were carried out in two river basins of the Lake Baikal catchment. Significant deterioration of river water quality (pH, turbidity, electric conductivity, and content of metals) was detected in the gold-mining sites. The extent of mercury contamination depended on the duration and intensity of mining activities. The most severe cases of mercury contamination were observed in areas with direct use of the mercury-amalgamation technique. Mercury concentrations at the gold-mining areas and at background sites varied from <0.001 to 0.78 mg kg
−1
for bedrock and minerals, <1–183 ng m
−3
for the atmosphere, 0.013–3.59 mg kg
−1
for soils, <5–5000 ng l
−1
, and <5–27 800 ng l
−1
for dissolved and particulate water fractions, respectively, and 0.008–54.2 mg kg
−1
for river-bottom sediments.
Lead isotopic fingerprinting of heavy metal contamination,Rio Pilcomayo basin, Bolivia
Authors: Miller Jerry R. , Lechler Paul J. , Hudson-Edwards Karen A. , Macklin Mark G.
Published: March 2005

Waste materials from mining of the Cerro Rico de Potosí precious metal-polymetallic tin deposits of southern Bolivia have been released to the headwaters of the Rio Pilcomayo for the past 450 years, resulting in extensive contamination of water, sediments and soils along the upper reaches of the river. This study uses isotopic data to identify the primary sources of Pb to the aquatic environment, and the relative contributions of each source to pre and post-mining alluvial deposits. Prior to the onset of mining activities in 1545, alluvial sediments along the Rio Pilcomayo were dominated by Pb from the underlying bedrock and from mineralized rocks exposed at the surface of Cerro Rico. Mining and milling operations at Cerro Rico released a new source of Pb to the river that can be traced downstream for at least 200 km. Simple mixing models suggest that Pb from the mines comprise between 30 and 89% of the Pb in the modern channel bed sediment. However, these estimates may be low because the isotopic composition of the contaminant source was based on samples of ore deposits rather than mill tailings, the latter of which contain fragments of both ore and host rock.
Arsenic speciation in the tailings impoundment of a gold recovery plant in Siberia
Authors: Lazareva Elena V. , Shuvaeva Olga V. , Tsimbalist Valentina G.
Published: March 2005

The recovery of gold from ores containing arsenopyrite releases significant amounts of arsenic into the environment. Arsenic releases primarily result from the processing and oxidation of stored mine tailings. This investigation examines: (1) the distribution of arsenic, iron, manganese and their chemical species in sediment cores extracted from a tailings impoundment in the Kemerovo region of southwestern Siberia; and (2) the weathering of arsenic minerals collected from its tailings dam. The data demonstrate that during storage of the sediments within the impoundment, arsenic is predominantly present as residual arsenopyrite and, to a lesser degree, as substances co-precipitated with iron hydroxide. The arsenic released from the sediment results from an oxidative dissolution of arsenopyrite and reductive dissolution of Fe oxides.
Mercury in vegetation and soils at abandoned mercury mines in southwestern Alaska, USA
Authors: Bailey Elizabeth A. , Gray John E. , Theodorakos Peter M.
Published: March 2005

We chemically analysed vegetation (willow and alder) and soil samples collected at three abandoned mercury (Hg) mines and at background sites in southwestern Alaska and compared Hg concentrations, speciation and distribution. Total Hg and methylmercury (MeHg) concentrations were higher in vegetation and soil samples from all the mine sites compared to samples from the background sites, but there was no correlation between total-Hg concentrations in vegetation and total-Hg concentrations in soil or between total-Hg and MeHg concentrations. However, the percent MeHg of the total Hg was higher in samples from the background sites compared to samples from the mine sites and is higher in vegetation samples than in corresponding soil samples. The percent MeHg is an order of magnitude higher in the willow samples than in corresponding alder or soil samples. The percent of divalent Hg [Hg(II)] is highest in soil samples from the retort and background areas. The higher percent MeHg in vegetation and soil in samples from background sites may be explained by the higher proportions of reactive Hg species, such as Hg(II), at these sites compared to the surface mined and tailings areas where most of the Hg is in the elemental and cinnabar (HgS) forms. Dissolved gaseous Hg species are more readily accumulated in vegetation and are more readily methylated than solid phases like HgS and liquid Hg.
Mercury distribution in water, sediment and soil in the Idrijca and SoĉAhca river systems
Authors: Horvat M. , Jereb V. , Fajon V. , Logar M. , Kotnik J. , Faganeli J. , Hines M. E. , Bonzongo J.-C.
Published: March 2005

Although the production of mercury (Hg) at the Idrija mercury mine, Slovenia, stopped in 1994, the tailings and contaminated soils in the mining region are continuously eroded and serve as a permanent source of Hg to the downstream rivers, flood plains and the Gulf of Trieste. The present article describes measurements of total Hg and monomethylmercury (MeHg) in various environmental compartments in the rivers Idrijca and So|$$|Ahca and the Gulf of Trieste during the period 1998–2000. Total Hg in the Idrijca river water upstream of the mercury mine varied between 2.8 and 6.9 ng l
−1
and increased to 197 ng l
−1
downstream of the mercury mine and remained elevated further downstream along the rivers Idrijca and So|$$|Ahca (from
c.
10 to 59 ng l
−1
), with lowest concentrations found in marine waters (from 0.2 to 2.0 ng l
−1
). The concentrations of total Hg were higher after the rain, which caused erosion and transport of particles enriched with Hg. Concentrations of MeHg were quite variable and did not follow the same trend as total Hg. The concentrations of MeHg in August 1999 were significantly higher than in June 1998, indicating the importance of seasonal effects, as well as hydrological conditions, on the production of MeHg. Above the mercury mine, MeHg was 0.1–0.2 ng l
−1
and doubled below the mercury mine. Downstream, in the rivers Idrijca and So|$$|Ahca, MeHg varied from 0.05 to 0.53 ng l
−1
and in marine waters from 0.06 to 0.08 ng l
−1
. Concentrations of Hg in sediments also increased downstream several fold with a value of 5.39 μg g
−1
above the mercury mine to a maximum of 727 μg g
−1
below the mine in the silt and clay fraction. The coarser-grained fraction (0.063 < 
d
 < 1.4 mm) frequently exceeded the value of total Hg in the silt and clay fraction due to the presence of particles of cinnabar. The concentrations of MeHg in sediments did not follow the same trend as total mercury. Highest concentrations of 14.1 and 10.0 ng g
−1
were found downstream of the peak total Hg concentration in sediments. In general, higher MeHg concentrations were associated with the silt and clay fraction, and accounted for 0.001–0.144% of total Hg. Total Hg in flood plain surficial soils varied from 60 to 150 μg g
−1
with less than 0.01% of mercury as MeHg. The results confirmed the fact that beside soils that are naturally elevated in Hg due to the high levels of Hg in geological materials in the Idrija district, there are also Hg-laden materials and tailings that are continuously eroded and deposited in flood plains downstream and serve as an important additional source of Hg to the rivers and the Gulf of Trieste. Important transformation mechanisms take place during fluvial transport, evidenced by the presence of MeHg in the various samples analyzed.
Low sampling density exploration geochemistry for gold in arid and tropical climates: comparison between conventional geochemistry and BLEG
Authors: Leduc C. , Itard Y.
Published: March 2005

Exploration of large areas for Au has led the Bureau de Recherches Géologiques et Minières to compare the efficiency of conventional fine-fraction geochemistry with BLEG (bulk cyanide leach extractable gold) sampling for low-density drainage surveys. Comparative test work was carried out on different types of mineralization in arid (Sudan) and tropical (Guinea, Indonesia) regions. Conventional geochemistry and BLEG give broadly similar results in all the test areas where Au anomalies of comparable size delineate the mineralized zones. In arid conditions, the mineralized zones can be detected by simulated surveys with a density of 1 sample per 10 km
2
, and such a sampling density is recommended for evaluating the Au potential in large remote areas. Under the tropical conditions of Indonesia (Irian Jaya), a lower density of one sample per 15 km
2
or more might be used in ‘grass-root’ surveys because of the large size of the potential mineralized zones and the mountainous morphology of the region.

In most of the test areas, the total Au contents of the stream sediment fine fractions (<63 μm, <125 μm or <180 μm) are higher than those extracted by BLEG from coarser size fractions (<500 μm or <2 mm) which means that cyanidation extracts only part of the free fine Au and/or that BLEG results are influenced by dilution of Au by barren material. On the other hand, the BLEG method extracted more Au than was present in the fine fraction from several sampling sites in Sudan and Iran Jaya, which indicated that the cyanidation extracted some coarse Au. The nugget effect so generated, however, does not hamper the recognition of mineralized zones.

From an operational point of view, conventional geochemistry on fine fractions is less costly than BLEG for remote areas, and has several other advantages including the ability to carry out multi-element analyses in order to rank anomalies, and the relatively easy transport and storage of samples.
X-ray diffraction data for the new ferroelectric tetragonal tungsten bronze phases, Ba2RETi2M3O15:M=Nb and RE=La, Pr, Nd, Sm, Gd, Dy, (Bi);M=Ta and RE=La, Nd
Authors: Miles Gabrielle C. , Stennett Martin C. , Pickthall David , Kirk Caroline A. , Reaney Ian M. , West Anthony R.
Published: March 2005

X-ray powder diffraction data are presented for nine new phases with the tetragonal tungsten bronze structure. By comparison with the structure of the M=Nb,RE=La analogue, these contain Ba in the large pentagonal sites with coordination number 15, a range of large rare-earth cations and Bi in the twelve coordinate sites, and the smaller cations, Ti and either Nb or Ta, in the octahedral framework sites. The a lattice parameter data of the tetragonal unit cell show an approximately linear variation with trivalent ion radius, apart from Dy, whose value appears to be anomalous; data for c show little variation with trivalent ion radius.
Europium nitride synthesized by direct nitridation with ammonia
Authors: Suehiro T. , Hirosaki N. , Wada T. , Yajima Y. , Mitomo M.
Published: March 2005

Europium nitride (EuN), which is potentially used as an activator for nitride luminescent materials, was prepared by direct nitridation at 600 °C in a NH3 atmosphere. X-ray powder diffraction and composition analysis of the nitrided sample were carefully conducted under an oxygen-free environment. The nitrided sample was found to be mononitride with NaCl structure. An appreciable amount of oxygen (∼0.06 a.u.) was detected, but no secondary oxide phase was found. The results suggest oxygen dissolution into the lattice of EuN.
Racial Variations in Treatment and Outcomes of Black and White Patients With High-Risk Non–ST-Elevation Acute Coronary Syndromes
Authors: Sonel Ali F. , Good Chester B. , Mulgund Jyotsna , Roe Matthew T. , Gibler W. Brian , Smith Sidney C. , Cohen Mauricio G. , Pollack Charles V. , Ohman E. Magnus , Peterson Eric D.
Published: March 2005

Background—

Black patients with acute myocardial infarction are less likely than whites to receive coronary interventions. It is unknown whether racial disparities exist for other treatments for non–ST-segment elevation acute coronary syndromes (NSTE ACS) and how different treatments affect outcomes.

Methods and Results—

Using data from 400 US hospitals participating in the CRUSADE (Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the ACC/AHA Guidelines?) National Quality Improvement Initiative, we identified black and white patients with high-risk NSTE ACS (positive cardiac markers and/or ischemic ST-segment changes). After adjustment for demographics and medical comorbidity, we compared the use of therapies recommended by the American College of Cardiology/American Heart Association guidelines for NSTE ACS and outcomes by race. Our study included 37 813 (87.3%) white and 5504 (12.7%) black patients. Black patients were younger; were more likely to have hypertension, diabetes, heart failure, and renal insufficiency; and were less likely to have insurance coverage or primary cardiology care. Black patients had a similar or higher likelihood than whites of receiving older ACS treatments such as aspirin, β-blockers, or ACE inhibitors but were significantly less likely to receive newer ACS therapies, including acute glycoprotein IIb/IIIa inhibitors, acute and discharge clopidogrel, and statin therapy at discharge. Blacks were also less likely to receive cardiac catheterization, revascularization procedures, or smoking cessation counseling. Acute risk-adjusted outcomes were similar between black and white patients.

Conclusions—

Black patients with NSTE ACS were less likely than whites to receive many evidence-based treatments, particularly those that are costly or newer. Longitudinal studies are needed to assess the long-term impact of these treatment disparities on clinical outcomes.