PRELIMINARY STUDIES OF TOXIC METAL POLLUTION IN THE MINING AND NEARBY AREA IN LEFKE REGION
Emür Henden, Onur Yayayürük, Nur Aksuner, Nüket Tirtom and Seniha Arsal
Department of Chemistry, Faculty of Science, University of Ege,
35100 Bornova, İzmir, Turkey
1. Introduction
Studies in the last 15 years have shown that untreated copper mining deposits left by Cyprus Mining Corporation (CMC) with no site security in the Lefke region is a serious source of pollution for soil, water storage reservoir, underground water and sea water. Large scale mining of sulfide, pyrite and calchopyrite ores and mineral processing activities took place in the Gemikonagi and Karadag region between 1913 and 1974 mainly for copper production. Gold production based on cyanide extraction was also done for a shorter period. At present, contaminated wastes are located in this area including several tailing ponds, waste water clarifiers, row copper ore piles, waste piles, remains of mine acid processing plant and remains as yellow soil pile of gold extraction with cyanide.
It is well known that wastes of sulfide containing minerals are oxidized by oxygen in air and by the oxidation of iron(III) forming sulfuric acid, this is named as acid mine drainage(AMD). AMD causes a form of water pollution characterized by low pH, high metallic and sulfate contents that originates in mining areas containing sulphide ores (1,2). It was also shown that bacterial oxidation of the sulfide containing ore and wastes is another effective reason of acid formation (3).
Various environmental studies have been carried out in the area, the latest being the UNDP project made for environmental assessment of the area in 2002 (4). This project also emphasized that the CMC wastes is a serious treat for the environment.
In this study, analyses were carried out for pH,
conductivity at the site on the 29th and 30th March 2007, and for CN
, As, Hg, Fe, Cu, Ni, Pb, Cd and Mn in the water, soil and
sediment samples collected on the same days will be presented.
2. Experimental
2.1. Reagents
All reagents used were of analytical reagent grade (from Merck). Quartz distilled water was used in the preparation of solutions. As mercury reducing agent 3% w/v stannous chloride was prepared daily by dissolving 7.5 g of SnCl2.2H2O in 37.5 mL of concentrated hydrochloric acid and finally making up to 250 mL with distilled water. Hg(II) solution (1000 mg L-1) was prepared by dissolving 1.00 g of analytical reagent grade mercury in 10 mL concentrated nitric acid. 0.3 mL of 5% K2Cr2O7 solution was added to prevent adsorption on glass-ware. Finally the solution was made up 10 % in nitric acid and diluted to liter with distilled water.
1000 mg L-1 arsenic(III) and arsenic(V) stock standard solutions were prepared by dissolving 0.330 g As2O3 and 0.383 g As2O5 respectively in concentrated HCl and diluting to 250 mL with distilled water. As(III) and As(V) stock solution contained 2 mol L-1 HCl. Standard solutions were prepared daily by dilution of the stock solutions. Sodium tetrahydroborate(III) solution was prepared by dissolving NaBH4 pellet in 0.01 M NaOH.
1000 mg L-1 cyanide stock solution was prepared by dissolving 1.6 g NaOH and 2.51 g KCN in 1L distilled water. Standard solutions were prepared by dilution with 0.15 M NaOH solution.
All glassware and polyethylene sampling cups were soaked in 10% nitric acid to remove any metal impurities and stop cross contamination for at least 24 hours prior to use and then rinsed with distilled water.
2.2. Instrumentation
For mercury determination PSA 10.004 atomic fluorescence spectrometer with continuous-flow vapour generator was used.
For arsenic determination GBC 904 PBT model atomic absorption spectrometer was used. The data system was a model Celeron-333 computer. A quartz tube atomizer and both HG 3000 continuous flow hydride generator and a laboratory-made batch type hydride generation system were employed. For the determination of the other metals the same apparatus was operated in the flame mode. In all the studies related hollow cathode lambs were used and background corrections was made with deuterium lamb.
For cyanide determination Jenway 3040 ion analyser with Orion 94-06 cyanide ion selective electrode was used.
WTW Multiline P4 Universal Meter was used for conductivity and pH measurements at site.
2.3. Sample Collection and Preservation
Water, soil and sediment samples were collected in polyethylene bags and water samples were put into polyethylene bottle on 29 and 30.04.2007 at the stations described in the Table 1 and is shown in Figure 1.
Sea water samples for metal ion analysis except for arsenic were taken by adding 1 g of Chelax 100 resin into 500 mL sample. Metal ions from the resin were recovered before the measurements by extracting with 1M HNO3. Sea water samples for arsenic was taken directly and acidified to 0,01 M HCl.
Table1. Samples and sampling stations.
|
|
|
1
Surface
soil samples taken at the entrance of the CMC processing plant.
2 Soil samples of the station 1 at the depth ~50-60 cm.
3 Sediment samples collected at the water barier for AMD near yellow soil pile
|
|
|
4 Surface soil samples taken at the yellow soil pile
5 Soil samples of the Station 4 at the depth ~90-100 cm.
6 Soil sample taken at red soil pile close to the yellow soil pile
|
|
|
7 Sediment sample taken at Pond 11 C
8 Sediment sample taken at Pond 14
|
|
|
9 Sediment sample of the small water pool in Karadağ
10 Sediment sample taken at Gemikonağı water reservoir
|
|
 |
11 Sediment sample taken at Gemikonağı water reservoir
12 Sediment sample of the sea in front of the yellow soil pile
13 Water samples collected at the barier for AMD.
14 Water sample collected at the Pond 11 C
15 Water sample collected at the Pond 14
16 Water sample of the small water pool in Karadağ
17 Water sample collected at Gemikonağı water reservoir
18 Water sample collected at Gemikonağı water reservoir
19 Water sample collected at Gemikonağı water reservoir
20 Water sample taken at Lefke İstiklal Primary School
21 Water sample taken at water well at the south of Gemikonağı water reservoir
22 Water sample taken at the water release point of Gemikonağı water reservoir (green colour)
23 Sea water sample taken at in front of the entrance of the CMC processing plant
24
Sea
water sample taken at in front of the the yellow soil pile
Water samples for metal analyses were preserved by making the sample 0.01 M in HCl . For cyanide analyses water samples were preserved by making the samples 0.01 M in NaOH. All the samples were brought to the laboratory in a double walled container cooled with ice and kept at 4oC in the laboratory until analyses.
2.4. Digestion Procedure for Sediment and Soil Samples
Sediment samples were dried at 60 oC. 10 mL conc. HNO3 was added onto 2 g sample in a 100 mL beaker and kept for 1 hour at room temperature. The mixture was heated at 250oC for 2 hours and then 3 mL of 30% (v/v) H2O2 was added. Heating was continued for 1 hour more. After cooling the mixture was filtered through black ribbon fitler paper and the filtrate was diluted to 50 mL with distilled water.
Soil and sediment samples were extracted with 1 M HCl at 60 oC for 1 hour for arsenic determination.
2.5. Measurements
Metal ions were determined by means of using atomic absorbtion spectrophotometer (AAS) with flame atomizer. Arsenic determination was made using AAS with continous flow hydride generation system. As(V) was reduced to As(III) in 1 M HCl by using KI and ascorbic acid before its conversion to hydride for its determination. In order to check interferences with the arsenic determination batch type hydride generation in more dilute HCl solution and masking metal ion interferences with 0.01 M EDTA were also made(5,6). Relative standard deviations for the determination of arsenic were in the range 4-6% and recoveries of arsenic(III) and arsenic(V) added in the sample solutions were above 90%. Mercury was determined using atomic flourecence spectrophotometer with continous flow cold vapour generation based on reduction of mercury(II) with SnCl2.
Total cyanide was determined by means of using a standard method based on distilation and measurements with cyanide selective electrode (7).
3. Results and Discussion
Results of the soil and sediment analyses are shown in
Table 2 and water analyses in Table 3. According to these measurements of pH,
conductivity at the site on the 29th and 30th March 2007, and for CN, As, Hg, Fe, Cu, Ni, Pb, Cd and Mn in the water, soil and
sediment samples collected on the same days have shown that the liquid wastes
in the tailing ponds were highly acidic with pH values between 2-2.5. Most of
the sediment and soil samples and liquids in the tailing ponds contain iron
and copper at high concentrations as expected. Concentration of Cd in all the
samples and Pb and Hg in water samples were below the LOD of the techniques
used. 0.85 mg kg-1 Hg was found in the sediment precipitated
behind the AMD barrier. Sediment and liquids of the tailing ponds also contain
considerably high concentration of arsenic. More significant is that analysis
of the total cyanide showed stil existing cyanide in the yellow soil pile
that is the wastes of the previous gold extraction process with cyanide. These
wastes were also found to contain relatively high concentration of arsenic.
Further more detailed analyses of the yellow soil pile for cyanide and arsenic
and tailing ponds and soil of the plants for arsenic need to be done for
remedation studies and to protect the environment and life.
Arsenic analyses in water samples are very critical because arsenic is easly lost by sorption on the sampling cup walls even present known precautions are taken from drinking waters. Therefore, analyses should be completed without delay after sampling. Moreover, interferences in the analyses techniques vary with the sample composition. In the present study it was observed that about 50% of arsenic in the tap water preserved with 0.1 M HCl was lost in 48 hours.