ГЕОХИМИЯ, 2008, № 9, с. 965-979
THE ACCUMULATION OF Cu, Zn, Cd, AND Pb IN AQUATIC BIOMASS
OF SULPHIDE TAILING PONDS
© 2008 r. Elena I. Khozhina*1 and Barbara L. Sherriff
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada * Corresponding author. Phone: (204) 474-7986, fax: (204) 474-7986, e-mail: ehozhina@inbox.ru 1 Permanent and correspondence address: Department of Geological Sciences, University of Manitoba,
Winnipeg, Manitoba, R3T2N2, Canada Поступила в редакцию 10.08.2006г.
Abstract—Flooding mine tailings to limit the oxidation of sulfides provides a habitat for aquatic organisms, such as plants, plankton, insects, and fish, which can uptake metals and, thus, threaten for local ecosystems and influence the cycling of elements in biogeocenosis. An aquatic ecosystem developed naturally in sulphide tailing ponds containing cyanidation wastes of the Salair ore-refining plant (SORP), Russia, was studied. The objectives of this research were to: i) reveal the level of contamination of living organisms in the tailing ponds compared to a natural control site; and ii) calculate the weight of metals in aquatic biomass to estimate amount of metals transferring from the tailing ponds into the biogechemical cycle.
The concentration of Cu, Zn, Cd, and Pb in the sediments of the tailing ponds is significantly higher than from the control site. Concentrations of Cu, Zn, Cd, and Pb in plant shoots were significantly higher than in the control and accumulated mainly in cell envelopes and membranes. The concentration of Pb in fish liver and eggs were 41 and 7.5 times higher, respectively, than maximum allowable concentrations.
The biomass distribution between producers and consumers of the tailing pond ecosystem is similar to those of natural pond ecosystems. However, the weights of Cu, Zn, Cd, and Pb in all trophic levels per hectare of the tailing pond are orders of magnitude higher than those for Lake Baikal. The largest portion of metal circulates within the ecosystem of the Dyukov Ravine Pond with a maximum of 5 to 13 % of this amount transferred into the surrounding environment through the food chains.
1. INTRODUCTION
The concentration of elements in living organisms depends on their physiological needs, and the metal content is related to the species [1]. However, this applies only to organisms living in natural uncontaminated environments. In mine waste environments with high levels of metals, living organisms can accumulate elements greater than their physiological need. Concentrations of some elements can be orders of magnitude higher in mine waste than in uncontaminated soils [2-5]. Terrestrial and aquatic plants, growing on the surface of mine waste, accumulate elements such as Cr, Co, Ni, Cu, Zn, As, Se, Cd, Sn, Sb, Hg, and Pb in concentrations up to thousands of times higher than those innatural uncon-taminated habitats [6-10].
Living organisms play a large role in the process of element migration at the Earth's surface. Perelman cited by [11] calculated that the total production of biomass for the past 500 million years has exceeded the mass of the Earth's crust. Therefore, organisms play a significant role in the process of element migration including the bio-geochemical cycling of elements in contaminated areas.
Large volumes of mine wastes produced by metal mining are usually stored in natural basins or artificial reservoirs. When mine tailings are exposed to atmospheric oxygen, acidification allows toxic metals be re-
leased into the surrounding environment [l2-14]. One of the techniques most commonly used to limit environmental impact from tailings is to flood them to create a water cover, which reduces the diffusion of oxygen to negligible levels [l5-17]. A favourable water balance and active engineering management are required to extend the life of a tailing impoundment [17-19].
Flooded tailing ponds are habitats for aquatic organisms such as plants, plankton, insects, and fish and potentially sources of metals into the food chain [5 and 10]. The aim of this study was to estimate the weight of metals (Cu, Zn, Cd, and Pb) transferred from flooded sulphide tailings into biogeochemical cycles through the components of an aquatic ecosystem at a metal mine in Salair, Russia. To do this, the concentration of metals and total mass were measured for water overlying solid tailings, aquatic plants and their transpiration excretions, insects, and fish. Metal paths from the submerged tailings into the surrounding environment were identified.
2. STUDY AREA, PLANTS AND ANIMALS 2.1. Area
The study was carried out using the ponds of the Salair ore-refining plant (SORP), Salair, western Siberia, Russia (Fig. 1). The measurements were made at the
^lai
Open pit
Plants (1-Au extracting, 2-Pb-Zn concentrating);
Submerged tailings
Exposed tailings;
....... Town border;
3 The Dyukov ravine pond; 4-6 Control areas
Fig. 1. The location of Salair and a schematic map of the Salair Refining Plant.
Dyukov Ravine Pond, one of a series of collection ponds of the SORP (Fig. 1), where mine tailings were dumped until 1975. Here, an ecosystem had developed naturally after the discharge ceased.
Dyukov Ravine contains 1.5 million tonnes of sulphide tailings from cyanidation of ore from a barite complex. It consists of four small reservoirs staggered on the slope from northeast to south-west (Fig. 2). These reservoirs are separated by dams made of limestone and diabase porphyry waste rock so that each reservoir is the separate sub-ecosystem. A road for industrial vehicles over a dam connects one of the open pits with the Pb-Zn ore refining plant. The local population has access to the reservoirs as houses are located at the Dyukov Ravine [20] (Picture 1). Reservoir 1, the largest area, is used for swimming and as a pasture for poultry and cattle, Reservoir 2 for poultry and cattle, and Reservoir 3 only for poultry (Picture 2). Animals drink the water and eat the aquatic plants and algae from these reservoirs. Reservoir 4 does not contain water or plants.
Three samples of water and living organisms were collected from Podsobnoe Lake, which is a dammed area of the Osipovka River, and two locations on the Kedrov-ka River 2.3, 2.4, and 4.8 km upstream from the tailings, respectively (Fig. 1). The average concentrations of metals in these samples were used as controls.
2.2. Plants, insects, and fish
Perennial aquatic plants (aquatic macrophytes) that usually grow on swampy ground and at the edges of ponds, lakes, and streams [21] were studied. These include common cattail (Typha latifolia L.) and narrow-leaved cattail (Typha angustifolia L.), common reed grass (Pragmites australis L.), woodland bulrush (Scirpus sylvaticus L.), swamp horsetail (Equisetum fluviatile L.), broad-leaved water-plantain (Alisma plantago-aquatica L.), and creeping spike-rush (Eleocharis palustris (L.) R. Br.). One species of rooted hydatophytes, a true aquatic plant, was collected but its species was not identified. All of the plants, except the rooted hydatophyte, are helophytes, aquatic plants which have part of their body above the surface of the pond water and, thus, transpire moisture to the atmosphere [21]. Historically, these plants have been utilized by people. For example, cattail leaves have been used for barrel, mat and paper production and the fuzz for packing material. Cattail rhizomes, reed shoots and woodland bulrush have been used for food [22-24]. Horsetail has unusual morphological features consisting of narrow leaves, the stem as the main photosynthetic organ and epidermal cells saturated with silica [25 and 26]. The hard stems of-horsetail have been used for scouring dishes.
The aquatic beetles, water-tigers (Colymbetes Clairv and Grophogeres), found in the ponds usually live in
Exposed tailindgs; Submerged tailindgs; Aquatic plants;
a-c
Gardens;
Sediment sampling;
Cattail bushes preferred by fish.
Fig. 2. A map of the Dyukov Ravine Pond.
fresh or brackish water, taking air from the atmosphere tigers can also carry a bubble of air under water to great
by swimming to the water surface and using their abdo- depths. Adult individuals eat insects and other inverte-
men to breathe. Their inability to stay under water for brates living in the water and the larger individuals can
long time was utilized here to develop a trap. The water- attack tadpoles and even young fish [27].
Silver crucian carp (Carassius auratus gibelio B.) is a native species for Siberia [28], which eats benthos, animal plankton, and algae [29 and 30]. Individuals of this species become sexually mature at about 4 years, when their bodies are more than 12 cm long. They usually spawn in June and July with their spawn sticking to submerged aquatic plants [29].
3. METHODS
A map of the Dyukov Ravine Pond was made using a rope-azimuth method. The map contains detailed information about the size of plant clusters, and the area of submerged and exposed tailings (Fig. 2). Surface areas were determined by cutting out and weighing each area of a copy of the map. These weights were converted to areas in square meters.
Chemical analyses were done in the Laboratory of Rare Element and Ecological Geochemistry at the United Institute of Geology, Geophysics and Mineralogy of the Siberian Division of the Russian Academy of Sciences. The Russian Federation Committee of standardisation, metrology, and certification (Russian State Standard) accredited the laboratory in 1999.
3.1. Sediments and water
Samples of sediments and pond water were taken from several equidistant sampling points in each reservoir (Fig. 2). Sediments were sampled from areas of 50 by 50 cm2 and up to 20 cm deep. Samples of pond water were taken at the same points. One sediment sample and one water sample were collected from each of the three Control Areas employing similar techniques.
Sediments were air-dried and crushed. A lg portion was
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