Toxicity and potential risk assessment of a river polluted by acid mine drainage in the Iberian Pyrite Belt (SW Spain)

Metal contamination from acid mine drainage (AMD) is a serious problem in the southwest of the Iberian Peninsula, where the Iberian Pyrite Belt is located. This zone contains original sulfide reserves of about 1700 Mt distributed among more than 50 massive sulfide deposits. Weathering of these minerals releases to the waters significant quantities of toxic elements, which severely affect the sediments and surface waters of the region. The main goal of this paper is to evaluate the toxicity and the potential risk associated with the mining areas using Microtox test and different factors which assess the degree of contamination of the sediments and waters. For this, a natural stream polluted by AMD-discharge from an abandoned mine has been studied. The results show that elevated concentrations of Cu, As and Zn involve an important potential risk on the aquatic environment, associated both with sediments and waters. Microtox test informs that the sediments are extremely or very toxic, mainly related to concentrations of Fe, As, Cr, Al, Cd, Cu and Zn. Pollution is mainly transferred to the sediments increasing their potential toxicity. A natural creek affected by AMD can store a huge amount of pollution in its sediments while exhibiting a not very low water pH and low water metal concentration.     

Heavy metal bioaccumulation and macroinvertebrate community changes in a Mediterranean stream affected by acid mine drainage and an accidental spill (Guadiamar River, SW Spain)

In the 1998 Aznalcóllar mining accident, 5 million cubic meters of toxic waste were spilled into the Guadiamar River (SW Spain). This paper describes the likely effects of metal pollution on the macroinvertebrate community in the first 15 km of the river adjacent to the mine, 2 years after the spill. The contents of Zn, Cu, Pb, As, Cd, Tl, and Sb in water, sediment, and in the caddisfly Hydropsyche were analysed, together with some physico-chemical parameters. From the results of physico-chemical and community parameters, the studied area was divided into three sections: the first section contained upstream control stations, not affected by current mining activities, and with a diverse macroinvertebrate community structure (mean number of families = 19); the second section, close to the mine, was severely polluted, with more than 50 mg l(-1) of Zn or 1.6 mg l(-1) of Cu in water, a pH of nearly 4, and a very diminished macroinvertebrate community (three families); in the last section, 6-15 km downstream from the mine, the water quality improved, metal concentrations decreased, pH reached neutrality and the macroinvertebrate community comprised eight families. We also determined metal concentrations in the larvae of Hydropsyche and found increases of 3- to 35-fold (for Cu and Cd, respectively) compared to control sites. As far as we are aware, these values are the highest concentrations so far detected in this caddisfly anywhere in the world. Different patterns of metal and pH tolerance were identified in macroinvertebrates. Most of the species were intolerant to present pollution levels and were only present in control sites. Others were tolerant to metal pollution but not to low pH and were present in the main river downstream of the mine, while a very few species managed to live in the most polluted section, with very low pH and high metal concentrations.     

Valuing acid mine drainage remediation in West Virginia: a hedonic modeling approach

In this article, we use a spatial-econometric approach to estimate the willingness to pay for the cleanup of acid mine drainage-impaired waterways in the Cheat River Watershed of West Virginia. We derive economic values for housing relating to remediating the effects of acid mine drainage using 21 years of housing sales data, and use geographic information systems to link housing market sales data with stream water quality. The results indicate being located near an acid mine drainage-impaired stream has an implicit marginal cost of $4,783 on housing. If all the streams are restored in the Cheat River Watershed, those properties located near the restoration (within a 1/4 mile) would benefit by $1.7 million. US EPA, Office of Research and Development, National Risk Management Research Laboratory, Sustainable Technology Division, Sustainable Environment Branch. The views are the authors’ and do not necessarily represent planned or actual policy of the EPA.     

Acid mine-water and agricultural pollution in a river skirting the Doñana National Park (Guadiamar river, South West Spain)

An inventory of the pollution originated by a mining industry in its first stages of development and by a highly developed agriculture is carried out in a river skirting the Doñana National Park.

The pathway along the Guadiamar river basin was studied for heavy metals derived from the opencast-worked polymetallic sulphide deposits and from the mine spoil heaps. The dynamics of N, P and herbicides in waters of urban and/or agricultural origin was also discussed.     

Social preferences and economic valuation for water quality and river restoration: the Segura River,Spain

The Water Framework Directive (WFD) aims at improving the ecological status of the water bodies in Europe. In this context, some rivers are currently being restored and, in accordance with this Directive, the restoration actions have to be evaluated from a socio‐economic approach. This work applies the Choice Modelling method to the WFD provisions for river restoration. This method proves to be useful for the economic valuation of the restoration measures, as well as a very important tool for people's public participation. In this sense, the water quality improvement has been defined as a priority action from a social point of view. Moreover, the method used has provided answers to both basic questions included in the WFD: the calculation of the economic value of the Segura River's ecological flow, the decrease of which would pose an environmental cost, and the estimation of the environmental income generated by this river.     

Sorption of benzo[a]pyrene to sediment contaminated by acid mine drainage: contrasting particle concentration-dependencies in river water and seawater

The sorption of benzo[a]pyrene (BaP) to sediment contaminated by acid mine drainage from the River Carnon, SW England, has been studied as a function of particle concentration in river water and seawater. The sediment is iron-rich and has a high specific surface area, and previous studies have demonstrated that it exhibits positive surface charge when suspended in native river water (pH approximately 5), and, through an increase in pH (to about 8) and the adsorption of organic matter, negative charge when suspended in seawater. Unit sorption of BaP exhibited an inverse dependency on particle concentration (particle concentration effect. PCE) in seawater, but was relatively invariant in river water. Consequently, BaP was apparently salted out at particle concentrations below about 100 mg l(-1), and salted in at higher particle concentrations. The absence of a PCE (and inherent salting in) for such a hydrophobic compound is an unusual, and possibly unique observation, and is inconsistent with a third (e.g. colloidal) phase model. More likely, a PCE in seawater is caused, in part, by salt induced particle-particle or particle-organic matter interactions which result in increasing particle aggregation or sorption irreversibility with increasing particle concentration. Although the results have limited environmental application and do not conclusively resolve any causal mechanisms for the PCE, they suggest that, with respect to neutral organic compounds, adsorbed organic matter is a pre-requisite for a PCE in the natural environment, and the effect should not solely or generally be attributed to the existence of a third phase.     

Seasonal factors controlling mineral precipitation in the acid mine drainage at Donghae coal mine, Korea

Monitoring over a 12 month period in the Sanae creek flow in acid mine drainage, Donghae coal mine area, demonstrates that the concentrations of dissolved metals and sulphate are highest during autumn when water flow in the creek is at its lowest. The highest pH values of the stream were measured in April and May, whereas the lowest pH was recorded in October. The Fe concentration of stream water rapidly decreased downstream due to the precipitation of Fe oxyhydroxide and/or oxyhydroxysulfate phases in the stream. Mineral precipitates in the creek in the Donghae mine area show various colours such as brownish yellow (Munsell colour 9.5 YR hues), reddish brown (Munsell colour 3.5 YR hues) and white depending on seasons and distance from the pollution source in the creek. Such phenomena are attributed to the variation in pH and chemical composition of stream water caused by seasonal factors. The measured pH ranges in stream water of the brownish yellow, white and reddish brown precipitates are pH 3.2-4.5, 4.5-6.0 and 5.3-6.9, respectively.     

Seasonal variations of characteristics of organic matter in the Dnieper River water

The paper assessed characteristics of natural organic substances of the Dnieper River (Kiev) by seasons of the year based on determination of such parameters as total organic carbon, absorption in the ultraviolet region (UV₂₅₄), specific absorption (SUVA), and color. It has been shown that in different seasons of the year the water in this region is characterized by average values of SUVA and a rather high content of total organic carbon.     

Spatial and seasonal variations in the water quality of the Amu Darya River (Central Asia)

Although the use of the water resources in Uzbekistan is strongly limited by their quality, it has to be noted that there is a lack of information and data within the international scientific literature with regard to the water chemical characteristics of the Amu Darya River, one of the main water resources in Central Asia. To add to such knowledge, this paper examines the spatial and temporal variation of the water quality of the Amu Darya River in order to assess its degree of degradation and the main causal factors. The functional relationships of the pollutants with respect to the flow regime are investigated. Finally an "opportune temporal window" for water withdrawal for filling the reservoirs, in relation to human consumption, will be indicated. The high salinization levels of the waters are mainly due to the presence of sulphates and chlorine. At the up-stream site salinity, although presenting elevated concentrations, does not exceed palatability levels; after the 450 km point the opportune temporal window for water withdrawal with acceptable salinity values is reduced to the period from May to September. Two main driving forces govern the temporal variation of the salinity of the Amu Darya water: a low drainage density of the area which limits the salt loads induced by the natural runoff processes, and snow and glacier melting in the upper catchment area which promotes dilution of the dissolved salts during the high-flow period. During low-flow periods salinity is strongly influenced by the return of waters used for land washing and irrigation.     

A decision support system for water quality issues in the Manzanares River (Madrid, Spain)

The Manzanares River, located in Madrid (Spain), is the main water supplier of a highly populated region, and it also receives wastewater from the same area. The effluents of eight Waste Water Treatment Plants (WWTPs) downstream of the river, which represent 90% of the flow in the middle and lower parts of the river, are the primary sources of water pollution. Although the situation has improved slightly in the last two years, the water in the river is highly polluted, making it uninhabitable for aquatic life. Water quality modelling is typically used to assess the effect of treatment improvements in water bodies. In this work, the GESCAL module of the Aquatool Decision Support System Shell was used to simulate water quality in the Manzanares River. GESCAL is appropriate for modelling in an integrated way water quality for whole water resources systems, including reservoirs and rivers. A model was built that simulates conductivity, phosphorous, carbonaceous organic matter, dissolved oxygen, organic nitrogen, ammonia, and nitrates. The period from October 2006 to September 2008 was selected for calibration due to the many treatment modifications that occurred during this time. An earlier and longer period, from October 2000 to September 2006, was used for validation. In addition, a daily model was used to analyse the robustness of the GESCAL model. Once the GESCAL model was validated, different scenarios were considered and simulated. First, different combinations of nutrient elimination among the different WWTPs were simulated, leading to the conclusion that investments have to focus on three of the proposed WWTPs. Moreover, these treatments will not be sufficient to maintain fish habitat conditions at all times. Additional measures, such as the increment of the flow in the river or oxygen injection, were simulated. Incrementing the flow of the Manzanares River has been shown to be an efficient means of increasing water quality, but this implies an increment in the risk of water scarcity situations in the Madrid water supply system.     

Effects of acid mine drainage on groundwater quality: a case study from an open-pit copper mine in eastern Turkey

This study was undertaken to determine the variation in groundwater quality of an open-pit copper mine in Maden (eastern Turkey) which has been in operation since 2000 BC, and with modern methods since 1939. Physical and chemical parameters (including pH, temperature, electrical conductivity, concentrations of Na, K, Ca, Mg, Cl, HCO₃, SO₄, NO₃, Fe, Co, Cr, Mn, Ni, Cu, Zn, Al, Cd, and Pb) of the groundwater and spring water samples from the study area were measured on a seasonal basis between October 2009 and July 2010. The groundwater quality was hydrochemically assessed in order to determine its suitability for human consumption and agricultural use. The measured and analyzed parameters in all the water samples were below the maximum admissible concentrations set out in international and national standards, guidelines, directives, and regulations for human consumption and for agricultural purposes. In addition, the results of previous studies on the possible effects of the mine site on soil, stream sediment, plants, and surface water in the same area are discussed.     

Comparative study of the Cd. Cu and Pb determination by AAS and by ICP-AES in river water : Application to a mediterranean river (Congost river, Catalonia, Spain)

The accuracy, precision, detection limit and rapidity in the determination of Cd, Cu and Pb in river water by AAS determination, previous extraction with APDC-MIBK system, is compared with direct determination method ICP-AES. Both methods show a similar detection limit and an analogous accuracy by the addition standard method. With a calibration curve only ICP-AES presents good accuracy, this technique is advantageous in long term precision and requires minimum sample preparation. The sample stability at different temperature conservation is studied. Finally both methods are applied to the determination of Cd, Cu and Pb in Congost river water.     

Geochemical fingerprints and controls in the sediments of an urban river: River Manzanares, Madrid (Spain)

The geochemical fingerprint of sediment retrieved from the banks of the River Manzanares as it passes through the City of Madrid is presented here. The river collects the effluent water from several Waste Water Treatment (WWT) plants in and around the city, such that, at low flows, up to 60% of the flow has been treated. A total of 18 bank-sediment cores were collected along the course of the river, down to its confluence with the Jarama river, to the south-east of Madrid. Trace and major elements in each sample were extracted following a double protocol: (a) "Total" digestion with HNO3, HClO4 and HF; (b) "Weak" digestion with sodium acetate buffered to pH=5 with acetic acid, under constant stirring. The digests thus obtained were subsequently analysed by ICP-AES, except for Hg which was extracted with aqua regia and sodium chloride-hydroxylamine sulfate, and analysed by Cold Vapour-AAS. X-ray diffraction was additionally employed to determine the mineralogical composition of the samples. Uni- and multivariate analyses of the chemical data reveal the influence of Madrid on the geochemistry of Manzanares' sediments, clearly manifested by a marked increase in the concentration of typically "urban" elements Ag, Cr, Cu, Pb and Zn, downstream of the intersection of the river with the city's perimeter. The highest concentrations of these elements appear to be associated with illegal or accidental dumping of waste materials, and with the uncontrolled incorporation of untreated urban runoff to the river. The natural matrix of the sediment is characterised by fairly constant concentrations of Ce, La and Y, whereas changes in the lithology intersected by the river cause corresponding variations in Ca-Mg and Al-Na contents. In the final stretch of the river, the presence of carbonate materials seems to exert a strong geochemical control on the amount of Zn and, to a lesser extent, Cu immobilised in the sediments. This fact suggests that a variable but significant proportion of both elements may be susceptible to reincorporation in the aqueous phase under realistic environmental conditions.     

Hydrological and chemical factors controlling the concentrations of Fe, Cu, Zn and As in a river system contaminated by acid mine drainage

The seasonal variations in the trace element concentrations and flow rates in the Carnon River system, south west England have been investigated on a monthly basis for a period of 1 yr. Approximately 85% of Fe, Zn and As, and 45% of Cu originate from mine waters. A strong seasonal dependence of the flux of trace elements in the natural and mine waters is observed. There appears to be a direct correlation between trace element concentrations and the proportion of infiltrated surface drainage in mine waters. Rises in these concentrations in the Carnon River due to increased fluxes from mine waters in winter months are offset by higher flow rates in surface discharge.Iron is transported predominantly in the particulate phase in Carnon River waters and virtually all dissolved Fe (< 0.45 μm) precipitates in estuarine waters. Dissolved concentrations of Cu, Zn and As appear to be regulated by sorptive processes particularly with Fe oxyhydroxides in both fresh and saline waters.     

Pollution of soils by the toxic spill of a pyrite mine (Aznalcollar, Spain)

On 25 April 1998 the retention walls broke open in a pond containing the residues from a pyrite mine of Aznalcollar (southern Spain), spilling some 45 x 10(5) m3 of polluted water and toxic tailings into the Agrio and Guadiamar River basin, affecting some 55 km2. On 5 May, seven sectors in the affected area were studied, analysing tailings, polluted water, and contaminated as well as uncontaminated soils. The principal pollutants were: Zn, Pb, Cu, As, Sb, Bi, Cd and Tl. The range of total contamination of each element was extremely broad, as penetration of the tailings depended on the soil characteristics. Most of the Cu, Zn and Cd penetrated the soil in the solution phase of the spill, while the other elements penetrated mostly as part of the solid phase. Zn exceeded the maximum concentrations permitted by the international community in four of the seven sectors studied, As in three, and the other elements only in one sector. Drying and consequent aeration of the tailings rapidly oxidized sulphides to sulphates, lowered the pH and solubilized the pollutants. Therefore, future rains could aggravate the pollution problem, if the tailings are not quickly removed.     

Solid state partitioning of trace metals in suspended particulate matter from a river system affected by smelting-waste drainage

The partitioning of particulate trace metals was investigated during one year of monthly sampling of suspended particulate matter (SPM) at eight sites along the Lot-Garonne fluvial system, known for its polymetallic pollution. The chemical partitioning in five operationally defined fractions (exchangeable/carbonate, Fe/Mn oxides, organic matter/sulfides, acid soluble, residual) was determined using a multiple single extraction approach. This approach showed that Cd, Zn, Pb and Cu were mainly associated with acid soluble phases (84-95%, 65-88%, 61-82% and 55-80% of the respective total metal content), and therefore showed a high mean potential of mobilization and bioavailability. In the Riou-Mort River, draining the smelting-wastes, Zn, Cd and Mn showed high mobility as they were little associated with the residual fraction (1-2%) and mainly bound to the 'exchangeable' fraction of SPM (60-80%), probably weakly adsorbed on amorphous freshly-precipitated sulfide and/or oxide phases. Upstream and downstream of the anthropogenic source of metallic pollution, Mn and Cd, and Zn to a lesser extent, remained highly reactive. The other trace metals were mainly associated with the residual fraction and thus less mobile. However, the multiple single extraction scheme revealed that the most reactive transport phases were non-selectively extracted by the conventional extractants used here. These selectivity problems could not have been observed if sequential extraction was used.     

The influence of biofilms on the migration of uranium in acid mine drainage (AMD) waters

The uranium mine in Königstein (Germany) is currently in the process of being flooded. Huge mass of Ferrovum myxofaciens dominated biofilms are growing in the acid mine drainage (AMD) water as macroscopic streamers and as stalactite-like snottites hanging from the ceiling of the galleries. Microsensor measurements were performed in the AMD water as well as in the biofilms from the drainage channel on-site and in the laboratory. The analytical data of the AMD water was used for the thermodynamic calculation of the predominance fields of the aquatic uranium sulfate (UO₂SO₄) and UO₂⁺⁺ speciation as well as of the solid uranium species Uranophane [Ca(UO₂)₂(SiO₃OH)₂?5H₂O] and Coffinite [U(SiO₄)_1 − x(OH)_4x], which are defined in the stability field of pH > 4.8 and Eh < 960 mV and pH > 0 and Eh < 300 mV, respectively. The plotting of the measured redox potential and pH of the AMD water and the biofilm into the calculated pH-Eh diagram showed that an aqueous uranium(VI) sulfate complex exists under the ambient conditions. According to thermodynamic calculations a retention of uranium from the AMD water by forming solid uranium(VI) or uranium(IV) species will be inhibited until the pH will increase to > 4.8. Even analysis by Energy-filtered Transmission Electron Microscopy (EF-TEM) and electron energy loss spectroscopy (EELS) within the biofilms did not provide any microscopic or spectroscopic evidence for the presence of uranium immobilization. In laboratory experiments the first phase of the flooding process was simulated by increasing the pH of the AMD water. The results of the experiments indicated that the F. myxofaciens dominated biofilms may have a substantial impact on the migration of uranium. The AMD water remained acid although it was permanently neutralized with the consequence that the retention of uranium from the aqueous solution by the formation of solid uranium species will be inhibited.     

Viral pollution determination of superficial waters (river water and sea-water) from the urban area of Barcelona (Spain)

Various surface water systems in the metropolitan area of Barcelona (Spain), including two rivers and three beaches, were analysed for human viruses using glass powder as adsorbent to concentrate them. The method used allows concentration of large volumes (up to 2001), of water in a single step. Values obtained varied from 18.4 to values higher than 55 MPNCU 1⁻¹in the Besôs river and 0.44-44 MPNCU 1⁻¹in the Llobregat river. Viruses were isolated from approx. 70% of sea-water samples, the values ranging from 0 to 1.60 MPNCU 1⁻¹. Findings are discussed in terms of correlation between virus pollution and bacterial indicators of fecal contamination. Also, the suitability of glass powder adsorption to concentrate viruses in sea-water is discussed.     

Aquatic insect diversity and biomass in a stream marginally polluted by acid strip mine drainage

Upper Three Runs receives a point source of acid mine drainage from a small acid feeder stream and the pH of the main stream falls from above 6 to about 4.5. Over the 1.2 km study section below the introduction of acid drainage, the pH rises to 5.0. This moderate degree of mine acid pollution has severely affected aquatic insect populations. The acid feeder itself (pH near 3.2) was inhabited only by a chironomid, a megalopteran (Sialis), and the caddisfly Ptilostomis. Biomass was very low (140 mg dry weight/m²). The drainage of the acid feeder into the stream caused a drop in the Shannon-Weiner diversity index from 3.10 to 1.95, and a drop in biomass from 6.5 g/m² to 2.2 g/m². At the two stations further downstream, the diversity index remained relatively constant and the biomass leveled off at about 1.2 g/m². The number of taxa declined steadily from 30 at the control station to 13 at the lowest site. Populations of Coleoptera, Ephemeroptera and Trichoptera showed little or no recovery as the acid pollution ameliorated slightly. Representatives of the orders Diptera and Plecoptera (especially Nemoura) showed a decided recovery and increase in numbers near pH 5.0. If fish were able to survive in acid mine polluted waters of pH's between 4.5 and 5.0 they should find sufficient insect food for maintenance of a limited population.     

Determination and speciation of copper and lead in sediments of a Mediterranean river (River Tenes, Catalonia, Spain)

Total concentrations of Cu and Pb and the speciation of these metals in sediments of the River Tenes are studied in order to establish the extent to which they are polluted and their capacity of remobilization. Five samples taken along the river were analyzed, major components of the sediments were studied using XRF and total Pb and Cu content were determined by AAS. In order to test the accuracy of the digestion methods used (triacid attack with nitric, perchloric and hydrofluoric acids or diacic attack with nitric and hydrochloric acids) for the determination of total trace metal, a standard reference material was also analyzed. Triacid attack is proposed to obtain good results. The results show a highly polluted area (1556 mg kg⁻¹ Cu and 1555 mg kg⁻¹ Pb) in the last sampling site analyzed. For metal speciation, the sequential scheme of Tessier et al. was used. From the results obtained, it can be concluded that Cu content in non-residual fraction is bonded mainly to organic matter, whereas non-residual Pb is mainly associated to iron and manganese oxides.