Stream water pollution by heavy metals around the Unalsky tailing pond

Semenova I.V.,Petrov V.A.

Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry ras, Moscow, Russia

parcete44@gmail.com

The elements and compounds uncovered and liberated through mining and processing, which are not usually part of the ecological systems (in such form or concentration) have the potential to alter the receiving environment to its detriment. Matter of concern is that high concentrations of contaminants can be released into the surrounding aquifers. This investigation reports preliminary laboratory results, which represents trace element concentrations in water streams around Unalsky tailing pond.

The research area is located in a mountain part of North Ossetia–Alania (North Caucasus, Russia). More precisely, it is in a valley between Bokovoi and Skalistui ranges (the Sadono-Unalsky kettle), in a river basin of Ardon and its inflows (rivers Unaldon and Mairamdon). Landscapes of this territory concern ecologically most vulnerable systems. The height above sea level varies from 900 to 2000 meters. Two types of breeds, such as crumpled in folds argillic rock mass and monocline limestone block prevail.

One of sources of pollution by heavy metals of water stream is a waste of Mizursky processing plant (MPP), stored in tailing pond around the village Nizniy Unal. Mining for lead and zinc began here from the end of 19 century. Factory raw-material base presented by vein-rocks of the Sadonsky ore deposit. The basic minerals extracting and processing from ores are galenite and sphalerite.

Considerable part of open surface tailing impoundment (from 40 to 50 percent in a various season) is constantly covered by water. The strip of dry tails, width of 45-100 m, reaches the northeast along a dam which are bending around tailing pond from the east. Taking into account the occupied area (17,5 hectares) and the measured depth (12-15 m), the capacity of tailing pond exceeds 2,2 million square meters.

The composition of tailings is directly dependent on the composition of the ore and the process of mineral extraction used on the ore. The pulp arriving from MPP represents a suspension of the crushed particles (~ 30%) of breed and liquid production wastes (~ 70%). Tailings mineral structure is correlated with average structure of ores of polymetallic deposits of Sadonsky ore field. Ore minerals, in decreasing order, are presented by sphalerite, galenite, pyrite, marcasite, chalcopyrite and arcenopyrite; nonmetallic – quartz, chlorite, barite, siderite and calcite [1].

Water samples were collected in September 2011. Samples were selected from eight surface sources higher up (Y-1, Ar-6) and downstream (Ar-1, Ar-2, Ar-3, Ar-4, Ar-5) from tailing pond. In addition, sample St-1 directly from a drain was taken. The detailed location of points is described at the Table.

Analysis of trace elements was carry out by inductively coupled plasma mass spectrometry (ICP-MS) in Laboratory of mineral substance analyses (IGEM RAS). Thus, content of thirty seven chemical elements in samples have been established. Maximum allowable concentration (MAC) in surface water is exceeded for copper and arsenic. However the arsenic content are at the moment specified by means of other analytical methods. It was caused by features of ICP-MS definition concerned analyte. Concentration date of some components is resulted at the Table.

№	Sample	Description	Mineralization, mg/l	pH	Pb, ppb	Cu, ppb	Cd, ppb	Sb, ppb	Mn, ppb	Co, ppb
1	Ar-1	2 km downstream from tailing pond, river Ardon	226,7	7,3	1,75	3,26	0,08	48,1	13,2	0,001
2	Ar-2	3 km downstream from tailing pond, river Ardon	198,7	7,3	1,20	1,23	0,05	33,2	10,4	0
3	Ar-3	5 km downstream from tailing pond, river Ardon	183	7,4	0,37	0,49	0,07	45,3	4,53	0
4	Ar-4	9 km downstream from tailing pond, river Ardon	183	7,4	2,26	1,27	0,12	45,1	17,4	0,02
5	Ar-5	1 m downstream after tailing pond, river Ardon	248,4	7,1	1,40	2,02	0,21	0,36	28,5	0
6	Ar-6	0,5 km higher up from tailing pond, river Ardon	186,3	6,9	0,81	0,55	0,51	0,55	4,73	0,01
7	Y-1	river Unaldon, higher up from tailing	176	7,1	1,44	0,77	0,67	0,44	8,20	0
8	St-1	drain of tailing pond	10746,1	11,2	1271,7	240,2	18,5	30324	131,4	3,65
	MAC	Maximum allowable concentration			30	1	1	50	100	10

Table. Stream water research date

Conclusions: 1. Content of heavy metals in a drain from tailing pond considerably exceeds maximum allowable concentration for surface water. Obtained data are evidence of danger of tailing pond for the surrounding environment.

2. Preliminary researches of a chemical compound of water show excess of the MAC concerning Cu and Sb whereas for drain of tailing pond practically all elements show their excess of the MAC. In spite of the fact that maximum allowable concentration in water streams around Unalsky tailing pond are in most cases comprehensible, it is necessary to carry out of the further researches in the field of migration of technogenic substances in different pH-Eh conditions.

References:

1. Panshin A.M., Evdokimov S.I., Solodenko A.B., Dzajnukov A.B. Recycling of a waste of the mountain-metallurgical enterprises. Vladikavkaz: Mavr, 2009. 196 p. (in Russian)