ASSESSMENT OF As AND HEAVY METAL ...

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ASSESSMENT OF As AND HEAVY METAL CONTAMINATION IN THE VICINITY OF DUCKUM Au-Ag MINE, KOREA JU-YONG KIM1 , KYOUNG-WOONG KIM1,∗, JONG-UN LEE1 , JIN-SOO LEE2 and JENNY COOK3 1 Department of Environmental Science and Engineering, Kwangju Institute of Science and

Technology, Kwangju 500–712, South Korea 2 School of Civil, Urban and Geosystem Engineering, Seoul National University, Seoul 151–742,

South Korea 3 British Geological Survey, Nottingham NG12 5GG, England

(∗ author for correspondence: tel.: 62 970 2442; fax: 62 970 2434; e-mail: [email protected])

Received 21 February 2001; accepted in revised form 5 September 2001

Abstract. In order to assess the potential of As and heavy metal contamination derived from past mining activity and to estimate the human bioavailability quotients for As and heavy metals. Tailings, soils and crop samples were collected and analysed for As, Cd, Cu, Pb and Zn. The mean concentrations of As, Cd, Cu, Pb and Zn in the tailings were 68.5, 7.8, 99, 3,754 and 733 µg g−1 , respectively. Maximum Pb concentration in tailings was up to 90 times higher than its tolerable level. The concentrations of these metals were highest in the soils from the dressing plant area, and decreased in the order: farmland soil to paddy soil. In particular, some of the soils from the dressing plant area contained more than 1% of Pb and Zn. The pollution index ranged from 0.19 to 1.93 in paddy soils, and from 1.47 to 3.60 in farmland soils. The average concentrations of heavy metals in crops collected from farmland were higher than those in rice stalks or rice grains, and higher than the internationally accepted limits for vegetables. Element concentrations extracted from farmland soils within the simulated human stomach for 1 h are 9.4 mg kg−1 As, 3.8 mg kg−1 Cd, 37 mg kg−1 Cu, 250 mg kg−1 Pb and 301 mg kg−1 Zn. In particular, the extracted concentrations of Cd, Pb and Zn are in excess of the tolerable levels. The results of the simple bioavailability extraction test (SBET) indicate that regular ingestion (by inhalation and from dirty hands) of soils by the local population could pose a potential health threat due to long-term toxic element exposure. Key words: As, heavy metal, mining activity, potential health threat, SBET

1. Introduction Coal and metal mining activities were actively developed in South Korea from the early 20th century, but most of the mines were closed in the 1970s due to economic conditions and the exhaustion of ore reserves. There are several thousand abandoned metal mines in Korea, and piles of untreated tailings have been left in the vicinity of these mining areas. The tailings contain several kinds of toxic contaminants, which include heavy metals, and these may cause deterioration in the ecosystem around the metal mines. Recently heavy metal contamination of agricultural soils and crops in the mining area has been identified as one of most Environmental Geochemistry and Health 24: 215–227, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands.

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JU-YONG KIM ET AL.

Figure 1. Sampling location map of the study area.

serious environmental problems in South Korea (Jung and Thornton, 1996; Min et al., 1997; Kim et al., 1998). The Duckum Au-Ag mine is located in the southwestern part of Korea (Figure 1), and was developed sporadically from 1935 to 1994. The average grade of the ore vein was 49 g Au ton−1 , and the average production of Au was 10 kg year−1 . The ore deposit of this mine was an Au-Ag bearing quartz vein and the major ore minerals were sphalerite, galena, pyrite and chalcopyrite. Also, arsenopyrite occurred as a minor mineral. In the Duckum mining area, dressing plant, 645160 m3 of tailings and 225 000 m3 of waste rock piles were abandoned without

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an impounding dam (Min et al., 1997), and these may act as a potential contamination source to the surrounding environment. The main objectives of this study were to assess the potential of As and heavy metal contamination derived from mining activity, to investigate the soil-crop relationship in terms of the availability of heavy metals in the contaminated area, and to estimate the human bioavailability quotients for As and heavy metals from the soils.

2. Materials and methods Four tailing samples, 4 soil samples from the dressing plant area located just below the mine adit, 4 farmland soils and 24 paddy soils were collected around the Duckum mine in September 1999 (Figure 1). Each sample was taken within a depth of 15 cm from the surface, and was a composite of 15–20 subsamples taken across a 1 × 1 m square. Air-dried tailings and soil samples were disaggregated, sieved on a 10 mesh (

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