Metal contamination of soils and dusts in Seoul metropolitan city,Korea

To investigate the dispersion patterns and the characteristics of heavy metal contamination due to urbanisation and industrialisation, soils and dusts collected from the Seoul area were analysed for Cu, Pb, Zn and Cd. The metal concentrations in most soils and dusts are higher than the world averages. The pollution index (( Metal concentrations in soils/Permissible level for metal)÷(Number of metals)) of soils and dusts is > 1 in most of the Seoul area, a result that concurs with the industrialisation and urbanisation index of the Seoul area. The soils are contaminated with Cu, Zn, Cd and particularly Pb. This suggests that the contamination of the soils in the Seoul area are mainly caused by vehicular emissions. The pollution index of soil is the highest in the Kuro area where Cu and Zn contamination in soils are due to the indigenous brass and bronze factories. From the discriminant analysis, the Seoul area may be partitioned into control, traffic and industrialized areas by the metal concentrations in the order of Zn > Cu > Pb.     

Enrichment of potentially toxic elements in areas underlain by black shales and slates in Korea

The Okchon black shale in Korea provides an important example of natural geological materials containing toxic elements; the Chung-Joo, Duk-Pyung, Geum-Kwan, I-Won and Chu-Bu areas are underlain by these black shales and slates of the Guryongsan Formation. This formation is part of the Okchon Group which is found in the central part of Korea. Geochemical surveys were undertaken in these five study areas in the Okchon Zone in order to examine the level of enrichment and dispersion patterns of potentially toxic elements in rocks and soils. After appropriate preparation, samples were analysed by instrumental neutron activation analysis and inductively coupled plasma atomic emission spectrometry for a range of elements. Arsenic, Cu, Mo, V, U and Zn are highly enriched in the Okchon black shales and their mean concentrations are significantly higher than those in black slates. These elements are closely associated with one another from a geochemical viewpoint and may be enriched simultaneously. Mean concentrations of As, Mo and U in soils derived from black shales occurring in the Duk-Pyung and Chu-Bu areas are higher than the permissible level suggested by Kloke (1979), and the enrichment index decreases in the order of Duk- Pyung > Chu-Bu > Chung-Joo > Geum-Kwan = I-Won areas. Uranium-bearing minerals such as uraninite and brannerite have been identified in black shales from the Chung-Joo area by electron probe micro-analysis. Uraninite grains are closely associated with monazite and pyrite with a grain size ranging from 2m to 10m whereas brannerite grains occur as a euhedral form 50m in diameter.     

Geochemical Characteristics of the Acid Mine Drainage in the Water System in the Vicinity of the Dogye Coal Mine in Korea

This study investigated geochemical characteristics of the acid mine drainage (AMD) discharged from the abandoned mine adits in the vicinity of the Dogye coal mine in Korea. Acid mine drainage discharged from Jeoncha pit adit of the Dogye coal mine, which is the main source of the AMD in the study area, had a pH value of 3.0 and concentrations of 2148mg SO₄ ^2– L^–1, 229mg Fe L^–1, 71mg A1 L^–1 and 11mg Mn L^–1. The reduction of some metal concentrations downstream from the discharge point could be explained on the basis of dilution and precipitation. The order of removal of metal ions downstream from the discharge point was Fe>A1, Cu>Zn, Mn. Acidity could be used as a good determining factor offering comprehensive and quantitative values for the polluting extent of acid mine drainage. The acidities existing in all acidic water samples in the Gunahan district originated primarily from mineral acidity, especially in the upper Nahan Creek from dissolved Fe and Al and in the middle and down Nahan Creek from dissolved Al. From the application of the WATEQ4F program, it was determined that predominant species of dissolved Fe in all water samples was Fe²⁺, and those of dissolved Al were AlSO₄ ⁺ and Al³⁺ except for IW2 sample which was associated with white precipitates. The species of dissolved Al in IW2 sample include also AlOH²⁺ and Al(OH)₂ ⁺. The saturation indices of goethite and haematite were positive in the water samples associated with ochrous precipitates (usually called Yellow Boy), therefore these solids might be precipitated. For the IW2 sample, the saturation indices of amorphous Al(OH)₃ and gibbsite were positive, so theoretically these solids might also be precipitated. By XRD analysis, it was found that goethite occurs in ochrous precipitates, and gibbsite in white precipitates.     

Platinum pollution in road dusts,roadside soils,and tree barks in Seoul,Korea

This study presents the level of platinum in urban environment in and around Seoul, the capital city of Korea. Road dust, roadside soil, and tree bark samples were collected from the sites of various traffic volumes and from control sites in the suburbs. The above samples were analyzed for Pt by ICP-MS and other heavy metals by ICP-OES. Platinum levels in road dusts and roadside soils from Seoul were in the range of 3.8–444 ng/g (av. 115.0 ng/g) and 0.7–221 ng/g (av. 49.7 ng/g), respectively, whereas those in the suburbs were in the range of 2.3–5.2 ng/g (av. 3.9 ng/g) in road dusts and 0.4–5.1 ng/g (av. 2.4 ng/g) in roadside soils. The highest Pt levels in road dusts were found from major roads with high traffic volume. The remarkable difference in average Pt level between heavy traffic roads (av. 132.2 ng/g) and light traffic roads (av. 22.8 ng/g) reflects that an important source of Pt in roadside environment is automobile catalytic converter. High Pt level in road dust was found from the site of erratic stop–start driving condition, for example, 178 ng/g Pt in road dust around a vehicle crossing gate. Platinum level in tree barks ranged from 0.9 to 4.5 ng/g, which indicates the existence of Pt-containing particulate matter in the atmosphere. Road dusts with high Pt level were enriched in traffic-related heavy metals.     

Assessment of soil and soil-gas radon activity using active and passive detecting methods in Korea

Radon ((222)Rn) is a carcinogenic gas produced by the radioactive decay of radium ((226)Ra). It has been reported that soil and soil-gas are primary factors that could cause indoor radon problems. Six sites were selected for this study--Sanbook, Gangcheon, Jikyeong, Choojung, Geumsung and Homyoung--each was classified according to bedrock type. In order to investigate soil-gas radon activities and radon emanating power, innovated active and passive detecting methods were developed and applied under both field and laboratory conditions. Statistical analysis of results confirmed that the radon activity values measured using either active or passive methods under field or laboratory conditions could be interchangeable with each other.     

Human risk assessment of As,Cd, Cu and Zn in the abandoned metal mine site

The cancer risk and the non-cancer hazard index for inhabitants exposed to As, Cd, Cu and Zn in the soils and stream waters of the abandoned Songcheon Au–Ag mine area were evaluated. Mean concentrations of As, Cd, Cu, Pb and Zn in agricultural soils were 230, 2.5, 120, 160, and 164 mg kg⁻¹, respectively. Mean concentrations of As, Cd and Zn of the water in the stream where drinking water was drawn was 246 μg L⁻¹, 161 μg L⁻¹ and 3899 μg L⁻¹, respectively. These levels are significantly higher than the permissible levels for drinking water quality recommended by Korea and WHO. The resulting human health risks to farmers who inhabited the surrounding areas due to drinking water were summarized as follows: (1) the non-cancer health hazard indices showed that the toxic risk due to As and Cd in drinking water were 10 and 4 times, respectively, greater than those induced by the safe average daily dosages of the respective chemicals. (2) the cancer risk of As for exposed individuals through the drinking water pathway was 5 in 1000, exceeded the acceptable risk of 1 in 10,000 set for regulatory purposes.     

Platinum pollution in road dusts,roadside soils,and tree barks in Seoul,Korea

This study presents the level of platinum in urban environment in and around Seoul, the capital city of Korea. Road dust, roadside soil, and tree bark samples were collected from the sites of various traffic volumes and from control sites in the suburbs. The above samples were analyzed for Pt by ICP-MS and other heavy metals by ICP-OES. Platinum levels in road dusts and roadside soils from Seoul were in the range of 3.8–444 ng/g (av. 115.0 ng/g) and 0.7–221 ng/g (av. 49.7 ng/g), respectively, whereas those in the suburbs were in the range of 2.3–5.2 ng/g (av. 3.9 ng/g) in road dusts and 0.4–5.1 ng/g (av. 2.4 ng/g) in roadside soils. The highest Pt levels in road dusts were found from major roads with high traffic volume. The remarkable difference in average Pt level between heavy traffic roads (av. 132.2 ng/g) and light traffic roads (av. 22.8 ng/g) reflects that an important source of Pt in roadside environment is automobile catalytic converter. High Pt level in road dust was found from the site of erratic stop–start driving condition, for example, 178 ng/g Pt in road dust around a vehicle crossing gate. Platinum level in tree barks ranged from 0.9 to 4.5 ng/g, which indicates the existence of Pt-containing particulate matter in the atmosphere. Road dusts with high Pt level were enriched in traffic-related heavy metals.

     

Seasonal Variations and Chemical Forms of Heavy Metals in Soils and Dusts from the Satellite Cities of Seoul, Korea

This research investigated heavy metal pollution of soils and dusts in two representative satellite cities of Seoul, Korea and studied the seasonal variations in metal concentrations through the rainy season and the chemical forms of metals using a sequential extraction analysis. The metal dispersion pattern was illustrated to match with urban structure. Soil and dust samples were collected from the cities of Uijeongbu and Koyang, which are the northern and northwestern satellite cities of Seoul (the capital), before and after rainy season. Concentrations of Cu, Pb and Zn were higher than those of the world averages for soils, and their levels decreased after rain, particularly in highly contaminated samples. Relatively high pH values were found in roadside soils, but no seasonal variation was found after the rainy season. The three metals (Cu, Pb and Zn) in soils and dusts were associated with various chemical fractions of soils and dusts as distinguished by the sequential extraction scheme, and a strong similarity of metal association between soils and dusts was found, which indicates that airborne dust may be a principle source of soil contamination. Copper is uniformly distributed, and Pb is largely associated with the reducible phase. There is an appreciable proportion of total Zn in the exchangeable/water-acid soluble fraction. After the rainy season, the most soluble fractions in soils and dusts were leached away. In terms of mobility and bioavailability of metals in soils and dusts, the order Zn >> Cu > Pb is suggested. Geographical variations of total metals corresponded well with urbanised areas of cities, especially the industrial complex and major motorways.     

Preface

The combination of bioremediation and electrokinetics, termed bioelectrokinetics, has been studied constantly to enhance the removal of organic and inorganic contaminants from soil. The use of the bioleaching process originating from Fe- and/or S-oxidizing bacteria may be a feasible technology for the remediation of heavy metal–contaminated soils. In this study, the bioleaching process driven by injection of S-oxidizing bacteria, Acidithiobacillus thiooxidans, was evaluated as a pre-treatment step. The bioleaching process was sequentially integrated with the electrokinetic soil process, and the final removal efficiency of the combined process was compared with those of individual processes. Tailing soil, heavily contaminated with Cd, Cu, Pb, Zn, Co, and As, was collected from an abandoned mine area in Korea. The results of geochemical studies supported that this tailing soil contains the reduced forms of sulfur that can be an energy source for A. thiooxidans. From the result of the combined process, we could conclude that the bioleaching process might be a good pre-treatment step to mobilize heavy metals in tailing soil. Additionally, the electrokinetic process can be an effective technology for the removal of heavy metals from tailing soil. For the sake of generalizing the proposed bioelectrokinetic process, however, the site-specific differences in soil should be taken into account in future studies.