Geological Society of Malaysia Annual Geological Conference 2001 June 2-3 2001, Pangkor Island, Perak Darul Ridzuan, Malaysia Minor and trace metals in slurry slime in mined-out ponds in the Kinta Valley, Perak CHOW WENG SUM Minerals and Geoscience Department Malaysia 201h Floor, Tabung Haji Building, Jalan Tun Razak, P.O.Box 11110, 50736 Kuala Lumpur Abstract: The Kinta Valley was renowned as the largest tin field in the world and up to 1989, there were 70,158 hectares of land under mining leases. Thereafter, the tin mining industry took a down-tum due to falling tin metal prices and what is left of the industry is now mined-out land with abundant abandoned ponds. Stretching from Pengkalan near lpoh to Kampar in the south over a distance of 42km, there is a total of 1,194 mined-out ponds. About 66.7% of these ponds have slurry slime at the pond bottoms, with thickness varying from O.lm to 7.0m. Many of these abandoned ponds are used for the rearing of fish and ducks, or are cultivated with lotus plants. Slime is occasionally admixed with tailing sand for agricultural purposes. As such, should the slime be contaminated with heavy metals the food chain will be affected. Slime from eight ponds in the Kinta Valley was tested for minor and trace metals. Most of the slime contained higher concentrations of uranium and other trace heavy metals such asSn, Hg, Sb, 8i and Cd as compared to the norm in the earth's crust or stream sediments. Amongst the eight test ponds, slime from Pond 881 contained relatively higher concentrations of minor, radioactive and trace metals. Slime from Pond 881 should not be utilised as fill material as the concentration of as is above the trigger concentration and threshold value. It should also not to be used for the planting of crops as the level of zinc is high. INTRODUCTION to the environment and to study whether concentrations of precious, radioactive, minor or trace heavy metals present The Kinta Valley was renowned as the largest tin field in the slurry slime conform to the norm in earth's crust or in the world and up to 1989, there were 70,158 hectares of are similar to that in the stream sediments. land under mining leases. Thereafter, the tin mining industry took a down-tum due to falling tin metal prices and what METHOD OF STUDY is left of the industry is now mined-out land with abundant abandoned ponds. Stretching from Pengkalan near lpoh to To study the distribution of heavy metals in the slurry Kampar in the south over a distance of 42km, there is a slime, eight ponds, five of which (Ponds E814, B72, B20, total of 1,194 mined-out ponds (Figure 1). About 66.7% of B 141 and B81) are left overs of the palong method of these ponds have slurry slime at the pond bottoms, with mining and the remaining three (Ponds B 122, B 127 and thickness varying from 0.1m to 7 .Om. Some of these ponds BS) which are abandoned dredged ponds were selected have been utilised for the rearing of fish or ducks. Some of (Table 1). the more shallow ponds are cultivated with lotus plants and Slurry slime was collected with a slime bailor and air­ the seeds and roots of the plants are considered a culinary dried and then crushed in an agate mortar. The crushed delicacy. Slime from some of the ponds has also been recovered samples were sieved to minus 80 mesh. A portion of the and admixed with tailing sand for agricultural purposes. sieved samples was analysed by Atomic Absorption As slurry slime from these mined-out ponds is Spectrophotometer for bismuth (Bi), cadmium (Cd), derived from the beneficiation of mineralised residual soil chromium (Cr), lead (Pb), copper (Cu), zinc (Zn), cobalt or alluvium, it may contain unusually higher concentrations (Co), nickel (Ni), iron (Fe), manganese (Mn), silver (Ag), of heavy metals such as Fe, Cu, Zn or As, which are molybdenum (Mo) and antimony (Sb). For mercury (Hg), associated with gangue minerals such as arsenopyrite, pyrite, a cold-vapour atomic absorption method was employed chalcopyrite or sphalerite. Should fishes ingest such slurry using a Coleman MAS-50 analyser. For the analysis of slime or crops cultivated on such slime, the plants and uranium (U), a fluorometer was used. fishes may absorb the heavy metals and may contaminate To analyse for tin (Sn), tungsten (W )and arsenic (As), the food chain. the samples were further crushed to minus 150 to minus 200 mesh and the colorimetry method modified from OBJECTIVES OF INVESTIGATION Stanton (1966) was employed. The methods of analyses for all 18 elements were The objectives of this investigation are to determine if adopted after the Geological Survey Special Paper 3 (GSD, the concentrations of metals in the slurry slime are hazardous 1981). 302 CHow WENG SuM Table 1. List of ponds tested for heavy metals in study area. Pond No. Mukim Longitude Latitude Mining Method Bedrock Geology E814 Kampar 101 ° 7'37.21" 4° 19' 13.46" Palong Limestone B72 Tg. Tualang 101 ° 4' 14.43" 4° 20' 11.39" Pa1ong Limestone with schist lenses B20 Tg. Tualang 101 ° 3' 18 .23" 4° 24' 50.12" Pa1ong Limestone B141 Teja 101 ° 5' 26.58" 4° 22' 3.04" Palong Deep limestone B81 Tg. Tua1ang 101 ° 2' 30.38" 4° 20' 48.60" Palong Schist with limestone lenses Bl22 Tg. Tualang 101 ° 4' 51.64" 4° 21' 46.35" Dredging Limestone with schist lenses B127 Teja 101 ° 5' 0" 4° 20' 51.03" Dredging Limestone B5 Tg. Tualang 101 ° 3' 25.06" 4° 24' 28.86" Dredging Deep limestone composition and the concentration of elements in the rocks may not conform to that as shown in Figure 2. Geochemical analyses of stream sediments collected . ' from the Kuala Pilah - Gemas area (Abdul et al., 1995 ), .' r Boundary Range area which is around the Kelantan - < 1\EOAH i ·' Trengganu - Pahang border (Chu et al., 1986), South / -·, Kelantan (Chu et al., 1982) and within the Kenyir Reservou in Trengganu (Chow, 1986) (Table 2) showed that mercury ./'·· ...... _ .i !" ~ - is present in the order of 10'2 ppm, silver, 10'2 to 10'1 ppm ( and uranium 10·1 to 10° ppm. Seven other metals, namely, I K ELANTAN I molybdenum, tungsten, antimony, bismuth, nickel, coba~ t and arsenic have concentrations in the order of 10° ppm. Tin and copper vary between concentrations of 10° to 1" 1 ppm. Lead, zinc and manganese are present in higher concentrations, with lead and zinc in the order of 10 1 pp and manganese, 102 ppm. Iron has the highest concentratio .:~ in the stream sediments and are present in the order of 100%. ',) PAHANG RESULTS .... .., -~ ~ ..... The concentrations of precious (silver), radioactive ( (uranium), minor (iron and manganese) or trace (molybdenum, copper, zinc, chromium, tin, tungsten, mercury, antimony, bismuth, cadmium, lead, nickel, cobalt and arsenic) metals in the slurry slime from the eight test ponds were analysed and compared with the average concentration in the earth's crust (as depicted in Figure 2 Figure 1. Location of the study area. which is after Darnley et al., 1995) and the concentrations in stream sediments (Table 2) in the Kuala Pilah-Gema" NATURAL BACKGROUND VALUES area (Abdul et al., 1995), Boundary Range area (Chu et al. , 1986), South Kelantan area (Chu et al., 1982) and th The average abundance of the 18 elements within the Kenyir Reservoir area (Chow, 1986). earth's crust are shown in Figure 2. Silver and mercury are Precious Metal found in the order of 1o- 2 ppm in the earth's crust. Of slightly higher concentrations are cadmium, antimony and One precious metal silver (Ag) was analysed. Silve1· bismuth, which are found in the order of 10·1ppm. Uranium, (A g) is normally present in low concentrations in the earth' s arsenic, tungsten, tin and molybdenum are present in crust and in the stream sediments (in the order of 10- z concentrations in the order of 10° ppm. Following these are ppm). cobalt, nickel, copper, lead and zinc which are present in Silver(Ag) the order of 101 ppm in the earth's crust. Of even higher concentrations are chromium, manganese and iron, which All slurry slime samples, except for two, B 1_41/S 1 and are present in the order of 102 ppm, 103 ppm and 104 ppm B 127 /S2, had concentrations of silver (Ag) (Table 3) highe.,.. respectively. than the average in the earth's crust which is in the orde However, it must be borne in mind that the granitic of 10·2 ppm (Figure 2) as well as that of stream sedi ment ~· rocks which are found in the Kinta Valley are acidic in from the Kuala Pilah - Gemas area, Boundary Range area, Geological Society of Malaysia Annual Geological Conference 2001 MINOR AND TRACE METALS IN SLURRY SLIME IN MINED-OUT PONDS IN THE KINTA V ALLEY, PERAK 303 Table 2. Concentrations of precious, radioactive, minor and trace metals in stream sediments. Note:Geochemical results of the Kuala Pilah - Gemas area are after Abdul eta/., 1995; the Boundary Range area after Chu et al., 1986; the South Kelantan area after Chu et al. , I 982; and the Kenyir Reservoir area after Chow, 1996. Total no. Locality Mo Cu Zn Cr Sn w Hg Sb Bi Cd Pb Ni Co As Fe Mn Ag u of samples ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm % ppm ppm ppm 512 Kuala Pilah - 1.0 30.0 29.0 - 10.0 3.0 0.07 2.0 1.0 14.0 4.0 4.0 8.0 1.9 155 0.08 1.17 Gemas area 3844 Boundary Range area (Kelantan-Terengganu u 9.4 43.0 5.2 2.5 0.06 19.0 3.7 3.7 /6.0 2.0 250 0.02 0.19 -Pahang border) 4360 South Kelantan 1.4 12.0 40.0 9.0 1.4 0.06 16.0 5.0 5.0 4.0 2.1 240 0.16 0.3 1000 Kenyir Reservoir 1.5 6.4 37.0 6.0 2.6 - 19.0 2.8 4.4 6.6 2.0 120 0.05 1.20 South Kelantan area and Kenyir Reservoir area which varied crust (Figure 2), but is very close to the stream sediments from 0.02 to 0.16 ppm (Table 2).