Mine Tailings Spill Research Articles

Mercury and other trace elements in soils affected by the mine tailing spill in Aznalcóllar (SW Spain)

The Aznalcóllar accident (28th April 1998) occurred because the collapse of the tailing-dam dike of the Aznalcóllar–Los Frailes mines. Soils were affected by a slurry of acidic water loaded with trace elements, finely divided metal sulphides, and materials used in the refining /floating process. Studies carried out before and after the soil restoration activities (sludge removal, amending, tilling, and afforestation) showed severe trace-element contamination (mainly As, Cd, Cu, Pb, Tl and Zn) in the superficial layer of the sludge-affected soils. Despite Hg being an important component of the Los Frailes ore and therefore of the contaminant sludge, data on Hg content of sludge-affected soils are scarce and sometimes controversial. The aim of this study was to determine the effect of the spill and of restoration measures on the Hg content of soils and how this related to other elements. Concentration of Hg immediately after the spill was 8-fold above background (0.061 ± 0.012 mg kg − 1 ; mean ± SD) at the surface (0–5 cm) and 3–4-fold greater in deeper layers (0–20; 0–50 cm). After the remediation measures, mean values of Hg and other elements (As, Cd, Cu, Pb and Zn) were very variable and remained above background values. These anomalies are due to the sludge left on the soil surface or buried during restoration operations, resulting in an irregular distribution of trace elements. The highest values for the less mobile elements (up to 176 mg kg − 1 As, 2.36 mg kg − 1 Hg and 1556 mg kg − 1 Pb) were observed in the area 1 km downstream of the tailings dam.

State of the marine environment at Little Bay Arm, Newfoundland and Labrador, Canada, 10 years after a "do nothing" response to a mine tailings spill.

In 1989, the tailings pond dam at the site of a former copper mine near Little Bay, Newfoundland and Labrador, Canada, ruptured and tailings spilled into Little Bay Arm. At the time, no action was taken to arrest the flow of tailings or to mitigate the effects of the spill. To date, no action has been taken to repair the dam and tailings continue to flow into Little Bay Arm. As a result, the marine environment around Little Bay Arm has become contaminated with heavy metals from the tailings. However, the tailings are not the only source of heavy metals to the ecosystem. An old slag heap and what is presumably concentrated copper ore spilled during the loading of ore freighters, are also contributing to the ecosystem's metal load. Marine sediment throughout the Arm contained elevated concentrations of Cu, Ni, Zn, As, V, Co, and Mn. Beach material also contained elevated concentrations of metals with material near the slag heap being the most contaminated. At this site, Cu concentrations were in excess of 5000 mg kg(-1) dry weight, Zn greater than 3000 mg kg(-1) and Co concentrations exceeded 700 mg kg(-1). The highest concentrations of metals in biota were found near the slag heap, near the tailings dam breach, and at the site of the former concentrate loading dock. Despite elevated metal concentrations, the tailings and nearby sediment were not devoid of life. Bivalves and seaweed were abundant in the area and there were no obvious signs of tissue damage or disease in soft shell clams (Mya arenaria) living in the tailings. These clams may be suffering from chronic exposure to the tailings, however, evidence of lipid peroxidation in the clams was inconclusive.

Heavy metal concentrations in marine sediments impacted by a mine-tailings spill, Marinduque Island, Philippines

A mine-tailings spill occurred on the island of Marinduque, Philippines, on 24 March 1996. Originating from the Marcopper Mine, tailings sludge flowed down the Boac River abruptly and during subsequent storm events. Most of the tailings material has since accumulated in the nearshore environment along the western coast of the island. Nineteen sediment cores were collected from this site and analyzed for heavy metals. Elevated concentrations of Cu (706–3,080 ppm), Mn (445–1,060 ppm), Pb (43–56 ppm), and Zn (131–276 ppm) are present in the tailings. Two horizons of high metal concentrations in the marine sediment profile are interpreted to correspond to two distinct tailings input events. The lower horizon corresponds to the original 1996 spill, whereas the spike near the surface is thought to be a combination of input due to dredging of the river in 1997 and reworking of sediments. A previous history of contamination is also deduced from the metal profiles. The volume of tailings material released into the marine environment due to the spill is estimated to be 180,000 to 260,000 m3.

Heavy metal content and speciation in groundwater of the Guadiamar river basin

This work presents the conclusions of a speciation study concerning Zn, Cd, Pb and Cu in groundwater from ten wells in the alluvial aquifers of the Guadiamar river, affected by Aznalcollar mine tailing spill (April 1998). The sampling campaign took place in January 2000, almost two years after the mining accident. Four metal fractions were determined: labile metal forms, H + exchangeable metal forms, strongly inert forms (associated with organic and inorganic matter in solution), and forms associated with suspended matter. Total metal concentration in groundwater followed the trend Cd<Pb<Cu<Zn. The speciation study showed that Zn and Cd were present to a great extent in available forms (labile and H + exchangeable), while Pb and Cu were found mostly in the less available forms (strongly inert). These results can illustrate the potential value of the speciation tool for the follow-up of spill-induced pollution in the area.

Determination of arsenic species in a freshwater crustacean Procambarus clarkii

AbstractThe arsenic species present in samples of the crayfish Procambarus clarkii caught in the area affected by the toxic mine‐tailing spill at Aznalcóllar (Seville, Southern Spain) were analyzed. The total arsenic contents ranged between 1.2 and 8.5 µg g−1 dry mass (DM). With regard to the different species of arsenic, the highest concentrations were for inorganic arsenic (0.34–5.4 µg g−1 DM), whereas arsenobetaine, unlike the situation found in marine fish products, was not the major arsenic species (0.16 ± 0.09 µg g−1 DM). Smaller concentrations were found of arsenosugars 1a (0.18 ± 0.11 µg g−1 DM), 1b (0.077 ± 0.049 µg g−1 DM), 1c (0.080 ± 0.089 µg g−1 DM), and 1d (0.14 ± 0.13 µg g−1 DM). The presence of two unknown arsenic species was revealed (U1: 0.058 ± 0.058 µg g−1 DM; U2: 0.12 ± 0.12 µg g−1 DM). No significant differences were seen with respect to the total arsenic contents between the sexes. However, significant differences in the total arsenic contents were revealed between the area affected by the spill and the area not affected, the contents being greater in the affected area. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Influence of the Aznalcóllar mining spill on the vertical distribution of heavy metals in sediments from the Guadalquivir estuary (SW Spain)

The Natural Park of Doñana and the Guadalquivir estuary were impacted by the release of 6 million cubic meters of acid waste after the mine-tailing spill in Aznalcóllar (Andalusia, SW, Spain). Here is presented the monitoring of the accidental spill on vertical distribution of heavy metals in the estuarine sediments. The total concentration of six metals (Fe, Mn, Zn, Cd, Pb, Cu), their chemical speciation and the organic carbon concentration were analyzed in sediment vertical profiles. The results obtained determine background levels similar to previously reported in the area. The analysis catalogues the impact of the accident on the estuary as acute and mainly associated with high concentrations of Zn and Cd. The recent enrichment in Zn and Cd and their geochemical association with the more mobile fractions of the sediment determine an environmental risk associated with the acute impact and detected in some of the areas of the estuary.

Modelling the oxidation of sulphides in an unsaturated soil

Abstract Within the framework of a study on the impact of a mine-tailing spill at Aznalćollar, SW Spain, we investigated the oxidation of pyrite and other sulphides by means of two column experiments and reactive transport modelling. The columns were filled with pyritic sludge mixed up with a sandy and a clayey soil, respectively. The columns were located outdoors for 15 months and leached 10 times. Prior to simulating reactive transport, a flow model permitted a detailed description of the behaviour of the column at a daily time-scale. The most important parameter extracted was the hydraulic saturation. This parameter controlled the amount of O 2 that could diffuse into the soil, which, in its turn, affected the rate of pyrite oxidation. The sandy and clayey columns behaved very differently. In the sandy column, pH dropped due to the oxidation of pyrite. As a result, silicate minerals dissolved, providing Na and/or K that precipitate together with Fe and SO 4 as jarosite. The high concentration of Zn in the leachates was consistent with the concentrations predicted from sphalerite oxidation. The low As and Pb concentrations, however, were explained by their coprecipitation in the jarosite. In the clayey column, the dissolution of dolomite kept the pH high, impeding the dissolution of silicate minerals and precipitating amorphous Fe(OH) 3 in the place of jarosite. The model also permitted rate laws proposed in the literature for pyrite oxidation to be discussed. We found that the oxidation of pyrite by Fe 3+ was not faster than by O 2 , contrary reports in the literature. Finally, the model was used to predict the behaviour of other soil types and other sludge contents. According to the predictions the dissolution of jarosite was very important to maintaining the pH at a value of approximately 2, even for gravels or low reactive sand.

Diatom communities as indicators of environmental stress in the Guadiamar River, S-W. Spain, following a major mine tailings spill

An accident in a mine tailings dam caused the outflowof mud and water rich in heavy metals in April 1998that flooded the Guadiamar River and its floodplain,in the vicinity of Donana National Park. Theimpact on the periphytic communities was evaluated byanalyzing the evolution of the diatom communitiesafter seven (November 1998) and fourteen months (June1999) of the accident. The comparison between thereference and affected sites showed a shift from adiatom community dominated by Fragilariaconstruens, Achnanthes minutisssima and Amphora pediculus to another dominated by Nitzschia palea and Gomphonema parvulum. Thevalues for Shannon-Wiener diversity strongly decreasedin the affected area; changes between survey periodsfailed to show a marked recovery. However, evennesswas slightly higher for the June 1999 period,suggesting a slight improvement in the diatomcommunity. Diatom indices (IPS-IDG, Descy, CEE,Lange-Bertalot) were applied to the data. Values forthese also showed a marked decrease in water qualityat sites closest to the mine tailings spill, as wellas a progressive recovery downstream. Correlationanalyses between the diatom descriptors and theenvironmental variables confirmed that heavy metals inthe water and sediment had a marked and lasting effecton the diatom communities of the Guadiamar. Otherpollution events (e.g. `alpechin' sewage) probablyhindered recovery of the periphytic communities.

Fluvial geomorphology and hydrology in the dispersal and fate of pyrite mud particles released by the Aznalcóllar mine tailings spill

The Agrio-Guadiamar River reach affected by the Aznalcóllar mine tailings spill can be divided into three main sectors taking account of geomorphic characteristics and human-induced changes. Along the first 15 km, the valley presents the characteristics of a middle fluvial reach of moderate sinuosity and gradient; the floodplain declines gently towards the main channel and is built up mainly by lateral accretion deposits, which are mined by open pits. The second sector is located between 15 and 30 km downstream of the mine, and is characterised by higher channel sinuosity and a lower gradient; the floodplain is built on overbank deposits, separated from the main channel by natural levees, showing some low sinuosity flood channels. Finally, the lowest reach, with a similar low gradient, can be described as the proximal area of the Doñana marshlands, whose geomorphology has been modified by agricultural practices for the last 40 years. The spread of mining tailings deposited a mat of pyrite mud (fine milled heavy metal-rich ore) over the main channel and floodplain with a thickness of up to 50 cm in the first sector and then, progressively decreasing downstream. The pyrite mud was deposited over the natural sediments without significant mobilisation of the latter and without relevant geomorphic changes. The subsequent cleaning up of the pyrite mud with the help of heavy machinery resulted in the removal of most of the bushy and herbaceous vegetation as well as the reworking of bed sediments and the destruction of their natural armouring. Relatively small amounts of submerged pyrite mud that could not be removed from the main channel and that mixed with the shallow natural sediments during the cleaning works provides a long-term pollution element in the system. Pyrite mud remnants on floodplains are not being directly removed by fluvial activity in the mid-term because these sedimentation areas are susceptible to erosion only by the wandering of the main channel. However, these materials can be easily oxidised, therefore, plant uptake and underground water pollution should be monitored. On the other hand, the channel bed and banks are source areas of sediments and pyrite materials that can be easily eroded due to the destruction of the natural protection features (vegetation and armouring). Once eroded, the pyrite particles will be transported over longer distances than the coarser host natural alluvium, and deposited on floodplains or areas with low flow velocity.

Feeding, growth, and habitat associations of young-of-year walleye (Stizostedion vitreum) in a river affected by a mine tailings spill

Nous avons etudie l'ecologie de dores (Stizostedion vitreum) tot au debut du cycle vital vivant dans un cours d'eau du nord de l'Ontario qui avait ete contamine par le deversement de 300 000 tonnes de residus d'une mine d'or. Nous avons compare l'alimentation, la croissance et la selection d'habitats chez des jeunes de l'annee dans un troncon de 5 km touche par les residus a celles de jeunes situes dans un troncon non atteint et situe plus en aval. L'etude s'est deroulee de juin a aout 1992, soit 1,5 ans apres le deversement. Le taux de croissance ne differait pas beaucoup entre les deux groupes avant la fin-juillet, date a laquelle les jeunes de l'annee situes dans le troncon atteint sont devenus significativement plus petits que ceux du troncon de reference. Chez les premiers, leur plus petite taille s'accompagnait du fait que leur estomac etait moins rempli, qu'on trouvait davantage d'estomacs vides et qu'on en capturait de moins en moins, ce qui est indicatif d'une mauvaise alimentation, d'une mortalite elevee et (ou) d'une emigration. Les jeunes de l'annee de plus de 25 mm longueur totale captures dans les deux troncons etaient presque exclusivement piscivores; ils se nourrissaient principalement de perchaudes (Perca flavescens) et de meuniers noirs (Catostomus commersoni) de l'annee. Il existe une correlation positive entre les prises par effort de peche du dore et celles de la perchaude et du meunier, mais sans qu'elle soit associee a aucune variable des microhabitats sauf la temperature. Ces resultats paraissent indiquer que, dans ce systeme, le dore juvenile est un generaliste sur le plan de l'habitat et qu'il choisit peut-etre ses secteurs en fonction de l'abondance du poisson lui servant de proie.

Feeding, growth, and habitat associations of young-of-year walleye (&lt;I&gt;Stizostedion vitreum&lt;/I&gt;) in a river affected by a mine tailings spill

Feeding, growth, and habitat associations of young-of-year walleye (&lt;I&gt;Stizostedion vitreum&lt;/I&gt;) in a river affected by a mine tailings spill