Geochemistry and pH control of seepage from Ni-Cu rich mine tailings at Selebi Phikwe,Botswana

Acid mine drainage from mine tailings at Selebi Phikwe, eastern Botswana, has been investigated using a combination of total decomposition, sequential extraction, X-ray diffraction, Mössbauer spectroscopy, and SEM analyses of solid phase samples, water analyses, isotopic analyses, and geochemical modeling. The principal ferric phases in the seepage stream sediments are jarosite and goethite, which incorporate Ni and Cu. The Mössbauer spectroscopy (MS) indicated exclusively 3+ oxidation state of iron with typical features of ferric hydroxides/sulfates. A fraction of dissolved sulfate is also sequestered in gypsum which precipitates further downstream. Significant portions of Fe, Ni, and Cu are transported in suspension. Values of pH decreased downstream due to H⁺ generated by the precipitation of jarosite. Values of δ²H and δ¹⁸O indicate evaporation of pore water in the mine tailings before seepage. Values of δ³⁴S(SO₄) are consistent with the oxidation of sulfides, but sample from the seepage face is affected by dissolution of gypsum. No minerals of Ni and Cu were detected and the principal attenuation processes seem to be adsorption and co-precipitation with jarosite. Higher contents of Cu are sequestered in solid phases compared to Ni, in spite of much higher dissolved Ni concentrations. Based on the speciation calculations, seepage water is undersaturated with respect to all Ni and Cu phases and adsorption and co-precipitation with jarosite seems to be the principal attenuation processes. Direct geochemical modeling was able to reproduce downstream pH trends, thus confirming the precipitation of jarosite as the principal pH-controlling process.     

Comparison of static and mineralogical ARD prediction methods in the Nordic environment

Acid rock drainage (ARD) is a major problem related to the management of mining wastes, especially concerning deposits containing sulphide minerals. Commonly used tests for ARD prediction include acid–base accounting (ABA) tests and the net acid generation (NAG) test. Since drainage quality largely depends on the ratio and quality of acid-producing and neutralising minerals, mineralogical calculations could also be used for ARD prediction. In this study, several Finnish waste rock sites were investigated and the performance of different static ARD test methods was evaluated and compared. At the target mine sites, pyrrhotite was the main mineral contributing to acid production (AP). Silicate minerals were the main contributors to the neutralisation potential (NP) at 60% of the investigated mine sites. Since silicate minerals appear to have a significant role in ARD generation at Finnish mine waste sites, the behaviour of these minerals should be more thoroughly investigated, especially in relation to the acid produced by pyrrhotite oxidation. In general, the NP of silicate minerals appears to be underestimated by laboratory measurements. For example, in the NAG test, the slower-reacting NP-contributing minerals might require a longer time to react than is specified in the currently used method. The results suggest that ARD prediction based on SEM mineralogical calculations is at least as accurate as the commonly used static laboratory methods.     

Evaluation of the impacts of mine drainage from a coal waste pile on the surrounding environment at Smolnica, southern Poland

Mine drainage impacts from a coal waste pile at Smolnica, Poland have been monitored. Groundwater in an unconfined aquifer downgradient from the pile has near-neutral pH, but high concentrations of sulfate (up to 3,827 mg/l), chloride (up to 903 mg/l), and sodium (up to 2,606 mg/l). Concentrations of iron and manganese are elevated only locally, and concentrations of other metals are low. The behavior of sulfate seems to be conservative in the downgradient aquifer, and gypsum may only be precipitating locally. Concentrations of iron and manganese seem to be controlled by the precipitation of ferric oxide and hydroxides and rhodochrosite, respectively. Complete neutralization of mine drainage by carbonates is consistent with high concentrations of calcium (up to 470 mg/l) and magnesium (up to 563 mg/l) and also with high strontium concentrations of up to 3.08 mg/l, observed in groundwater downgradient from the pile. Hydraulic head profiles at two sites within the river bottom sediments indicate upward flow toward the river with large local differences in groundwater recharge. Water chemistry profiles in the river bottom sediments and geochemical modeling suggest conservative behavior of Na, Cl, and SO₄ and precipitation of Fe and Mn at the groundwater/river water interface. Mine drainage enters the Bierawka River and causes increasing sulfate concentrations. In contrast, concentrations of sodium and chloride in the Bierawka River decrease downgradient from the pile because water in the river upgradient from the pile is already highly contaminated by these species from the discharge of mining waters. Concentrations of Fe and Mn in the river water are low, as a consequence of the precipitation of Fe and Mn oxide and hydroxides. Direct geochemical modeling was able to reproduce measured concentrations of conservative species (e.g., Na, Cl, and SO₄), but errors for metals and Ba were relatively large. In addition, calculated P_CO2 values in the river water are very high, suggesting that equilibrium with atmospheric P_CO2 and P_O2 has not been reached, and at least some reactions should be modeled as kinetic processes. High concentrations of Na, Cl, and SO₄ contribute to the contamination of the Odra River, which is joined by the Bierawka River farther downgradient, thus limiting the use of river water for recreation and other purposes.     

Natural factors and mining activity bearings on the water quality of the Choapa basin, North Central Chile: insights on the role of mafic volcanic rocks in the buffering of the acid drainage process

This contribution analyzes water chemical data for the Choapa basin, North Central Chile, for the period 1980-2004. The parameters considered are As, Cu Fe, pH, EC, SO??2, Cl?1, and HCO[Formula: see text], from samples taken in nine monitoring stations throughout the basin. Results show rather moderate contents of As, Cu, and Fe, with the exception of the Cuncumén River and the Aucó creek, explained by the influence of the huge porphyry copper deposit of Los Pelambres and by the presence of mining operations, respectively. When compared against results obtained in previous researches at the neighboring Elqui river basin, which host the El Indio Au-Cu-As district, a much reduced grade of pollution is recognized for the Choapa basin. Considering the effect of acid rock drainage (ARD)-related Cu contents on the fine fraction of the sediments of both river basins, the differences recorded are even more striking. Although the Los Pelambres porphyry copper deposit, on the headwaters of the Choapa river basin, is between one and two orders of magnitude bigger than El Indio, stream water and sediments of the former exhibit significantly lower copper contents than those of the latter. A main factor which may explain these results is the smaller degree of H(?+?)-metasomatism on the host rocks of the Los Pelambres deposit, where mafic andesitic volcanic rocks presenting propylitic hydrothermal alteration are dominant. This fact contrast with the highly altered host rocks of El Indio district, where most of them have lost their potential to neutralize ARD.     

Stormflow hydrochemistry of a river draining an abandoned metal mine: the Afon Twymyn, central Wales

Contaminated drainage from metal mines is a serious water-quality problem facing nations that exploit metal mineral resources. Measurements of river hydrochemistry during baseflow are common at mine sites, whilst detailed hydrochemical information regarding stormflow is limited and often confined to a single event. This study investigates the seasonal evolution of stormflow hydrochemistry at an abandoned metal mine in central Wales, UK, and the possible sources and mechanisms of metal release. Significant flushing of metals was observed during stormflow events, resulting in concentrations that severely exceeded water-quality guidelines. The relationship between metal concentrations and river discharge suggests dissolution of efflorescent metal sulphates on the surface of the mine spoil as the principal source of the contamination. High fluxes of Pb during stormflows are linked to extended periods of dry weather prior to storm events that produced water table drawdown and encouraged oxidation of Pb sulphide in the mine spoil. However, some Pb flushing also occurred following wet antecedent conditions. It is suggested that Fe oxide reduction in mine spoil and translatory flows involving metal-rich pore waters results in flushing during wetter periods. Detailed measurements of stormflow hydrochemistry at mine sites are essential for accurate forecasting of long-term trends in metals flux to understand metal sources and mechanisms of release, to assess potential risks to water quality and instream ecology, and to gauge the potential effectiveness of remediation. In order to protect riverine and riparian ecosystems, it is suggested that routine monitoring of stormflows becomes part of catchment management in mining-impacted regions.     

Reservoir water quality: a case from Jordan

Jordan relies heavily on reservoirs building and development to cope with water supply challenges, where monitoring and assessment of reservoir water quality are critically important for the sustainable use of these water supplies. Mujib Dam is an important water supply source in central western Jordan. Evaluation of water quality parameters and their spatial distributions (vertical and horizontal) showed near-neutral pH values with nearly similar values from surface to bottom. The vertical profile of DO and TDS in the dammed reservoir showed slight decreasing trends with increasing depth. Although Ca, Mg, Na, and K concentrations varied slightly with depths, their variations showed no trends. Similarly, the vertical and horizontal distribution patterns of Cl, SO₄, HCO₃, NO₃, and PO₄ in Mujib reservoir water showed insignificant variations in surface water layer and relatively unchanged values or decreasing trends through the water column. Higher values of TN have been observed, especially in the western part, suggesting that agricultural activities and livestock farming in the upstream catchment are impacting water quality. Results revealed that weathering and dissolution of rocks are the major source of water chemistry. The majority of trace metal levels (Cd, Cr, Cu, Fe, Mn, Pb, Zn, Co, Ni, Sr, and B) in water showed relatively similar surface and bottom values. The concentrations of COD and BOD₅ in surface water were relatively low with higher concentrations observed in the northwestern corner, coincided with higher levels of chlorophyll a. The average ratio of TN to TP in surface water suggests that phosphorus is the limiting factor for the algal blooms, whereas the average chlorophyll a level in surface water indicates oligo-mesotrophic water.     

Evolution of water chemistry in natural acidic environments in Yangmingshan,Taiwan

In Yangmingshan National Park, located in the northern part of the Taiwan Island, there is a very rare area where fish (Channa asiatica) live in spite of acid environments. The origin of the acid in local acid ponds and rivers and the evolution of the water chemistry are discussed on the basis of sulfur stable isotope ratios and chemical equilibria. One of the sources of the acid is sulfuric acid, which is derived from the oxidation of hydrogen sulfide in volcanic gas gushing out from fumaroles around the area and from acid deposition supplied from Taipei City. It is also derived from the oxidation of pyrite: the sulfur stable isotope ratios of delta 34S of +1@1000 to +4@1000 (relative to CDT) of sulfate in acid pond waters (pH 3-4) could be related to those of hydrogen sulfide in volcanic gas, pyrite in local pond sediments and soils, and sulfate in rain water. One acid source is sulfuric and hydrochloric acids arising in springs from geothermal activity: the delta 34S values were characterised by +13@1000 to +17@1000 sulfate-S, which was provided by a disproportionation reaction of sulfur dioxide in the depths. Another acid source could be the oxidation of iron(II). Under acidic conditions, the water-rock reaction gives rise to high concentrations of aluminium and iron. While flowing down surface streams, iron(II) is oxidised to iron(III) and then hydrolysed to cause further acidification under oxic conditions. The concentrations of iron and aluminium are controlled by redox and dissolution equilibria.     

Preservation of sulfidic waters containing dissolved As(III)

Solutions containing variable concentrations of sulfide (0 to 31 ppm) and arsenite (0.35 to 10 ppm) were subjected to several different preservation treatments. As predicted by equilibrium thermodynamics, at near-neutral pH the experimental solutions were undersaturated with respect to orpiment (As2S3). However, upon acidification to pH 2 with HCl or HNO3, instantaneous precipitation of poorly crystalline As2S3 occurred in sulfidic solutions which resulted in the loss of dissolved arsenite. These results have implications concerning the practice of acidifying water samples containing hydrogen sulfide with HCl or HNO3 for the purpose of preserving total arsenic values. If a near-neutral water sample contains 1 ppm arsenite and as little as 0.4 ppm sulfide, loss of dissolved arsenic will occur upon acidification. An alternative three-step preservation method involving base addition, oxidation, and acidification is proposed and investigated as an appropriate technique for preserving sulfide-bearing aqueous samples for total arsenic.     

Geochemical behavior of heavy metals in a Zn–Pb–Cu mining area in the State of Mexico (central Mexico)

The geochemical behavior of zinc, lead and copper from sulfidic tailings in a mine site with potential to generate acidic drainage (pyrite (55%) and sphalerite (2%)) is reported in this paper. The mining area is divided in two zones, considering the topographic location of sampling points with respect to the tailings pile: (a) outer zone, out of the probable influence of acid mine drainage (AMD) pollution, and (b) inner zone, probably influenced by AMD pollution. Maximum total ions concentrations (mg/L) measured in superficial waters found were, in the outer zone: As (0.2), Cd (0.9), Fe (19), Mn (39), Pb (5.02), SO4(2-) (4650), Zn (107.67), and in the inner zone are As (0.1), Cd (0.2), Fe (88), Mn (13), Pb (6), SO4(2-) (4,880), Zn (46). The presence of these ions that exceeding the permissible maximum limits for human consume, could be associated to tailings mineralogy and acid leachates generated in tailings pile.     

The effect of oxidation and acidification on the speciation of heavy metals in sulfide-rich freshwater sediments using a sequential extraction procedure

The speciation of metals in a contaminated, anoxic, sulfide-rich, freshwater sediment was determined experimentally, using a sequential extraction procedure based on the method of Tessier et al. Taking into account the advantages and disadvantages of sequential extractions, the applied methodology allowed the investigation of the influence of aeration and acidification on the distribution of various metals in the sediment. Aeration caused Zn and Cd to be released from sulfides. Carbonates were partly dissolved by the oxidation process, causing mobilisation of Ca. Fe became less mobile owing to a stronger binding to organic matter. The speciation of K, Al, Ni, Pb and Mn and to a lesser extent of Cu was not affected by aeration. As a result of acidification of the aerated sediment, Ca, Mn, Ni, Zn and Cd became more mobile owing to the dissolution of carbonates.     

Leaching of potential hazardous elements of coal cleaning rejects

The geochemical characteristics of coal cleaning rejects (CCR) in Santa Catarina State, Brazil, were investigated. Around 3.5 million ton/ year of coal waste are dumped in Santa Catarina State. Coal beneficiation by froth flotation results in large amounts of CCR composed of coaly and mineral matter, the latter characterised by the occurrence of sulphide minerals and a broad array of leachable elements. The total and leachable contents of more than 60 elements were analysed. Atmospheric exposure promotes sulphide oxidation that releases substantial sulphate loads as well as Ca^2?+?, K^?+?, Mg^2?+?, Cl^??? and Al^3?+?. The metals with the most severe discharges were Zn, Cu, Mn, Co, Ni and Cd. Most trace pollutants in the CCR displayed a marked pH-dependent solubility, being immobile in near-neutral samples. The results highlight the complex interactions among mineral matter solubility, pH and the leaching of potentially hazardous elements.     

Radioactivity, Physical and Chemical Parameters of Underground and Surface Waters in Qua Iboe River Estuary, Nigeria

Radioactivity, physical and chemical parameters of underground boreholes and surface waters in the region of Qua Iboe River Estuary involved in oil production activities were measured. The physical and chemical parameters measured included pH, temperature, turbidity, and concentrations of total dissolved and suspended solids, dissolved oxygen, chemical and biochemical oxygen demand, oils and grease, salinity, hardness (carbonates and bicarbonates), chlorine, sulphide, and metal ions. The work reveals that the radioactivity, physical and chemical parameters determined for both the underground and surface waters are safely below the international permissible limits except that of carbonate (68.6 mg/d – 228.7 mg/l) and bicarbonate (22.9 mg/l – 76.3mg/l) which renders both sources of water hard. The exceedingly high concentration range of hydrogen sulphide (40 mg/l–440 mg/l) in both sources is also beyond the international limit of 0.05mg/l. The ammonium ion concentration (1.40–2.80mg/l) was determined to be slightly higher in both the underground and surface waters than the international limit of 0.5mg/l.     

Evaluation of the Impact of Acid Mine Drainage on the Chemistry and the Macrobenthos in the Carolina Stream (San Luis – Argentina)

The purpose of this study was to evaluate the impact of acid mine drainage on the chemistry and the macrobenthos of the Carolina stream (San Luis – Argentina). Samples were obtained in the years 1997–1998 at two sites: site C₁, located 200 m upstream of the drainage, and site C₂, located 800 m downstream. The system buffer capacity was evaluated in the non – contaminated site by means of the buffer index calculation. The physico – chemical changes observed as a consequence of the contribution of acid mine drainage (AMD) were: a decreasing of pH and an increase in the ionic concentration, especially sulfate and Fe coming from the oxidation produced by chemiolithotrophic bacteria. The values obtained indicated a low buffer capacity and a high intrinsic vulnerability of the system to resist the impact originated by the AMD, producing a remarkable decreasing of pH of the receiving stream. These changes caused modifications in the original benthic community that was replaced by organisms more tolerant to the acid stress. A reduction in the abundance and in the taxonomic richness of the benthic macroinvertebrates was observed when compared with the reference station. An increase in the proportion of Chironomidae and of Acari and a decrease in the proportion of the remaining taxa were observed. The most sensitive groups were Ephemeroptera, Trichoptera and Mollusca. The community was mostly affected by the following variables: pH, conductivity, sulfate and dissolved total Fe.     

Speciation of mercury in mine waste: case study of abandoned and active gold mine sites at the Bibiani–Anwiaso–Bekwai area of South Western Ghana

Speciation determines toxicity, transport pathways and residence time of a metal in different compartments of the environment. This study investigated the speciation of mercury in soils, derived from sites known for dumping of mine wastes in the Bibiani–Anwiaso–Bekwai district, a gold mining community of the Western Region of Ghana. Soil samples were taken from the surface; depths of 20, 40 and 60?cm from mine waste at both abandoned and active mine sites. Each sample was analysed for total mercury, organic mercury and elemental mercury. After sample treatment, digestion and reduction with stannous chloride (SnCl₂), total mercury content was determined using the Inductively Coupled Plasma—Optical Emissions Spectrometer (ICP–OES). Organic mercury content was determined employing a differential technique after disposing of elemental mercury by heating. Total mercury content in samples ranged from 0.067 to 0.876?mg/kg for surface soils. The same soil of depths 20, 40 and 60?cm had total mercury from 0.102 to 1.066, 0.037 to 4.037 and 0.191 to 4.998?mg/kg, respectively. For organic mercury, concentrations range from 0.012 to 0.260?mg/kg for surface soil. Soil depths of 20, 40 and 60?cm had organic mercury concentrations from 0.016 to 0.653, 0.041 to 1.093 and 0.101 to 2.546?mg/kg respectively. Elemental mercury concentrations in surface soils, soils at depths of 20, 40 and 60 cm ranged from 0.043 to 0.780; 0.017 to 0.749; 0.014 to 2.944 and 0.009 to 2.452 mg/kg respectively. Among the sites studied, only galamsey tailings (GM) showed a trend of increasing total mercury level with increasing depth. For the other sites, trends were not defined. There has been no defined trend for elemental mercury with depth at any of the sampling sites. Just as with total mercury, it was only GM that showed an increasing trend of organic mercury concentration with depth.     

Assessment of spatial variability in some soil properties as related to soil salinity and alkalinity in Bafra plain in northern Turkey

The objectives of this study were to assess the variability in soil properties affecting salinity and alkalinity, and to analyze spatial distribution patterns of salinity (EC) and alkalinity (ESP) in the plain, which was used irrigation agriculture with low quality waters. Soil samples were collected from 0–30cm, 30–60cm, 60–90cm and 90–120cm soil depths at 60 sampling sites. Soil pH had the minimum variability, and hydraulic conductivity (Ks) had the maximum variability at all depths. The mean values of pH, EC, ESP and Ks increased while the mean values of CEC decreased with soil depth. Values pH, EC and ESP were generally high in the east and northeastern sides. Soil properties indicated moderate to strong spatial dependence. ESP and pH were moderately spatially dependent for three of the four depths, EC exhibited moderate spatial dependence for one of the four depths, CEC had a moderate spatial dependence at all depths, and Ks exhibited a strong spatial dependence. EC, CEC, and ESP were considerably variable in small distances. The spatial variability in small distances of EC, CEC, pH and ESP generally increased with depth. All geostatistical range values were greater than 1230m. It was inferred that the strong spatial dependency of soil properties would be resulted in extrinsic factors such as ground water level, drainage, irrigation systems and microtopography.     

Modelling the contribution of different sources of sulphur to atmospheric deposition in the United Kingdom

In order to understand relationships between sources and receptors of atmospheric deposition, computer models must be used. This paper describes a Lagrangian acid deposition model that represents emissions of trace species across Northern Europe. The chemistry of sulphur dioxide, dimethyl sulphide and hydrogen sulphide is represented and the model tested against estimates of UK wet and dry deposition. Mean UK wet and dry deposition for the period 1992–1994 was 206 and 145 ktonne S yr^-1, respectively. The model predicted wet and dry deposition of 222 and 166 ktonne S yr^-1, in good agreement with measurements. The model has been used to examine the sources of deposited S to the UK. For a base year of 1992, 86% of the UK's SO₂ emissions are exported. The S deposition attributable from mainland European sources was 36% of the UK total S deposition, in good agreement with other UK models but this differs substantially from the calculations of the EMEP model. Natural sources of S deposition from planktonic emissions of dimethyl sulphide, biological emissions of hydrogen sulphide and non-eruptive volcanic emissions of sulphur dioxide contributed approximately 1% of the modelled UK S deposition, of which 95% originated from dimethyl sulphide. The explicit chemical scheme for dimethyl sulphide incorporated into the model showed that 24% of the resultant deposited S was methane sulphonic acid. Boundary conditions of the model were tested and it was found that initialisation of sulphur dioxide and sulphate concentrations to representative ambient conditions had a very small effect. The modelled contribution of UK and European sources to UK S deposition was approximately 40 and 60%, respectively, showing the dramatic change arising from projected UK SO₂ emissions in 2010. This revised version was published online in July 2006 with corrections to the Cover Date.     

Application of artificial neural networks for classification of uranium distribution in the Central Rand goldfield,South Africa

Mine tailings generate significant environmental impacts and contribute to water pollution. The Central Rand goldfield, South Africa is replete with gold mine tailings which have contributed significantly to water pollution as a result of acid mine drainage (AMD). Water quality is affected by mine tailings and spillages, especially from active slimes dams, currently reprocessed tailings, as well as footprints left behind after reprocessing. The release and distribution of uranium from these sites was studied. Correlation matrices show a strong link between different variables as a result of AMD produced. Principal component analysis (PCA) was used to identify very influential variables which account for the pollution trends. Artificial neural networks (ANN) using the Kohonen algorithm were applied to visualise these trends and patterns in the distribution of uranium. High concentrations of this radionuclide were detected in streams in the vicinity of the tailings dumps, active slimes and reprocessing areas. The concentrations are reduced drastically in dams and wetlands as a result of precipitation and dilution effects.     

Monitoring and assessment of surface water acidification following rewetting of oxidised acid sulfate soils

Large-scale exposure of acid sulfate soils during a hydrological drought in the Lower Lakes of South Australia resulted in acidification of surface water in several locations. Our aim was to describe the techniques used to monitor, assess and manage these acidification events using a field and laboratory dataset (n?=?1,208) of acidic to circum-neutral pH water samples. The median pH of the acidified (pH?<?6.5) samples was 3.8. Significant (p?<?0.05) increases in soluble metals (Al, Co, Mn, Ni and Zn above guidelines for ecosystem protection), SO₄ (from pyrite oxidation), Si (from aluminosilicate dissolution) and Ca (from carbonate dissolution and limestone addition), were observed under the acidic conditions. The log of the soluble metal concentrations, acidity and SO₄/Cl ratio increased linearly with pH. The pH, alkalinity and acidity measurements were used to inform aerial limestone dosing events to neutralise acidic water. Field measurements correlated strongly with laboratory measurements for pH, alkalinity and conductivity (r ²?≥?0.97) but only moderately with acidity (r ²?=?0.54), which could be due to difficulties in determining the indicator-based field titration endpoint. Laboratory measured acidity correlated well with calculated acidity (r ²?=?0.87, acidity present as Al^III?>>?H⁺?≈?Mn^II?>?Fe^II/III) but was about 20 % higher on average. Geochemical speciation calculations and XRD measurements indicated that solid phase minerals (schwertmannite and jarosite for Fe and jurbanite for Al) were likely controlling dissolved metal concentrations and influencing measured acidity between pH 2 and 5.     

Effects of Acid Rock Drainage on Stocked Rainbow Trout (Oncorhynchus mykiss): An In-Situ, Caged Fish Experiment

In-situ caged rainbow trout (Oncorhynchus mykiss) studies reveal significant fish toxicity and fish stress in a river impacted by headwater acid rock drainage (ARD). Stocked trout survival and aqueous water chemistry were monitored for 10 days at 3 study sites in the Snake River watershed, Colorado, U.S.A. Trout mortality was positively correlated with concentrations of metals calculated to be approaching or exceeding conservative toxicity thresholds (Zn, Mn, Cu, Cd). Significant metal accumulation on the gills of fish stocked at ARD impacted study sites support an association between elevated metals and fish mortality. Observations of feeding behavior and significant differences in fish relative weights between study site and feeding treatment indicate feeding and metals-related fish stress. Together, these results demonstrate the utility of in-situ exposure studies for stream stakeholders in quantifying the relative role of aqueous contaminant exposures in limiting stocked fish survival.     

Concentration of Cd, Cu, Pb, Zn, Al, and Fe in soils of Manresa, NE Spain

The aims of this study were to determine the contents of cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn), aluminium (Al), and iron (Fe) (aqua regia-extractable) in 27 soil plots (54 samples) from Manresa, NE Spain, and to establish relationships between heavy metals and some soil properties. The main soil types were surveyed and the median concentrations (mg kg(-1)) obtained were Cd 0.28, Cu 20.3, Pb 18.6, Zn 67.4, Al 22,572, and Fe 21,551. Element concentrations for these soils were lower than the published values for the Valencia region (Spain) and Torrelles and Sant Climent municipal districts (Catalonia, Spain). In terms of soil properties, the results of this study suggest that, in Manresa soils, both trace element adsorption and retention are influenced by several properties such as clay minerals, carbonates, organic matter, and pH. All element contents were positively correlated with clay content. Pb and Zn were negatively correlated with pH and CaCO(3).