Comparisons of human risk assessment models for heavy metal contamination within abandoned metal mine areas in Korea

Environmental Geochemistry and Health - This study was initiated to develop a model specialized to conduct human risk assessments (HRAs) of abandoned metal mine areas in Korea. The Korean guideline...     

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.     

Investigation and risk assessment modeling of As and other heavy metals contamination around five abandoned metal mines in Korea

Tailings, agricultural soils, vegetables and groundwater samples were collected from abandoned metal mines (Duckum, Dongil, Dongjung, Myoungbong and Songchun mines) in Korea. Total concentrations of arsenic (As) and heavy metals (Cd, Cu, Pb and Zn) were analyzed to investigate the contamination level. Several digestion methods (Toxicity characteristics leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP), 0.1 N/1 N HCl) and sequential extraction analysis for mine tailings were conducted to examine the potential leachability of As and heavy metals from the tailings. The order of urgent remediation for the studied mines based on the risk assessment and remedial goals was suggested. The Songchun mine tailings were most severely contaminated by As and heavy metals. Total concentrations of As and Pb in the tailings were 38,600–58,700 mg/kg (av. 47,400 mg/kg) and 11,800–16,800 mg/kg (av. 14,600 mg/kg), respectively. Agricultural soils having high As concentrations were found at the all mines. Average concentrations of Cd in the vegetables exceeded the normal value at all mines areas, while As only at the Dongjung, Myoungbong, and Songchun mine area. One groundwater sample each from the Dongil and Myoungbong mines, and 4 groundwater samples from the Songchun mine had values above 10 μg/L of As concentration. The TCLP method revealed that only Pb in the Songchun tailings, 6.49 mg/L, exceeded the regulatory level (5 mg/L). Employing the 1-N HCl digestion method, the concentration of As in the Songchun mine tailings, 4,250 mg/kg, was up to 3,000 times higher than its Korean countermeasure standard. Results from the sequential extraction of As in the tailings showed that the easily releasable fraction in the Myoungbong and Songchun mine tailings was more than 30% and the residual fraction was less than 40%. Based on results showing the exposure health risk employing the hazard quotient and cancer risk of As, Cd and Zn, the Dongil mine needs the most urgent remedial action. The concentration reduction factor (CRF) of As in both soil and groundwater follows the order: Songchun>Dongjung>Dongil>Myoungbong>Duckum mine.     

Mineralogical and geochemical characterization of arsenic in an abandoned mine tailings of Korea

The mineralogical and chemical characteristics of As solid phases in arsenic-rich mine tailings from the Nakdong As–Bi mine in Korea was investigated. The tailings generated from the ore roasting process contained 4.36% of As whereas the concentration was up to 20.2% in some tailings from the cyanidation process for the Au extraction. Thin indurated layers and other secondary precipitates had formed at the surfaces of the tailings piles and the As contents of the hardened layers varied from 2.87 to 16.0%. Scorodite and iron arsenate (Fe₃AsO₇) were the primary As-bearing crystalline minerals. Others such as arsenolamprite, bernardite and titanium oxide arsenate were also found. The amorphous As–Fe phases often showed framboidal aggregates and gel type textures with desiccation cracks. Sequential extraction results also showed that 55.7–91.1% of the As in tailings were NH₄-oxalate extractable As, further confirmed the predominance of amorphous As–Fe solid phases. When the tailings were equilibrated with de-ionized water, the solution exhibited extremely acidic conditions (pH 2.01–3.10) and high concentrations of dissolved As (up to 29.5 mg L⁻¹), indicating high potentials for As to be released during rainfall events. The downstream water was affected by drainage from tailings and contained 12.7–522 μg L⁻¹ of As. The amorphous As–Fe phases in tailings have not entirely been stabilized through the long term natural weathering processes. To remediate the environmental harms they had caused, anthropogenic interventions to stabilize or immobilize As in the tailings pile should be explored.     

Risk assessment of cadmium intake via food among residents in the mining-affected areas of Nandan County,China

Environmental Geochemistry and Health - This study investigated the dietary structure, Cadmium (Cd) contents in foods and exposure to Cd through diets of the residents in the mining-affected areas...     

Contamination by Cd, Cu, Pb, and Zn in mine wastes from abandoned metal mines classified as mineralization types in Korea

The objective of this study was to investigate heavy metal contamination and geochemical characteristics of mine wastes, including tailings, from 38 abandoned mines classified as five mineralization types. Mine waste materials including tailings and soils were sampled from the mines and the physical and chemical characteristics of the samples were analyzed. The particle size of tailings was in the range of 10–100 μm. The pH of the waste covered a wide range, from 1.73 to 8.11, and was influenced by associated minerals and elevated levels of Cd, Cu, Pb, and Zn, extracted by a Korean Standard Method (digestion with 0.1 mol L⁻¹ HCl), which were found in the wastes. Half of the samples contained heavy metals at levels above those stipulated by the Soil Environmental Conservation Act (SECA) in Korea. In addition, extremely high concentrations of the metals were also found in mine wastes extracted by aqua regia, especially those from mines associated with sulfide minerals. Thus, it can be expected that trace elements in mine wastes may be dispersed both downstream and downslope through water and wind. Eventually they may pose a potential health risk to residents in the vicinity of the mine. It is necessary to control mine wastes by using a proper method for their reclamation, such as neutralization of the mine wastes using a fine-grained limestone.     

Soil washing of As-contaminated stream sediments in the vicinity of an abandoned mine in Korea

A soil washing process was applied to remediate arsenic (As)-contaminated stream sediments around an abandoned mine in Goro, Korea. Laboratory scale soil washing experiments for As-contaminated stream sediments were performed under various washing conditions in order to maximize As removal efficiency. Stream sediments were taken from two sites (S1 and S5) along the main stream connected to an abandoned mine. Stream sediments at the two sites were divided into two groups (≥0.35 and <0.35 mm in diameter), giving four types of sediments, which were thereupon used for soil washing experiments. The results of soil washing experiments involving various pH conditions suggested that As removal efficiency is very high in both strongly acidic and basic solutions (pH 1 and 13), regardless of sediment type. Removal efficiencies for fine sediments from S1 and S5 were >95% after 1 h of washing with 0.2 M citric acid (C₆H₈O₇). When using 0.2 M citric acid mixed with 0.1 M potassium phosphate (KH₂PO₄), the As removal efficiency increased to 100%. When recycled washing solution was applied, As removal efficiency was maintained at a level greater than 70%, even after eight recycling events. This suggests that the recycling of washing solution could be successfully applied as a means of decreasing the cost of the washing process. Results from the experiments suggest that soil washing is a potentially useful process for the remediation of As-contaminated stream sediments around abandoned mines.     

Concentrations of arsenic and heavy metals in vegetation at two abandoned mine tailings in South Korea

Untreated abandoned mines may result in hazards to ecosystems due to dispersion of various toxic elements such as arsenic (As) and lead (Pb). Phytoremediation is an alternative of remediation for large scale mine dumps. Plant species were sampled from two abandoned gold (Au) mines in South Korea. Plant samples were digested following the guidelines of US EPA Method 3050 (US-EPA, 1996) and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Concentrations and bioaccumulation factors of plants are reported and out-performing species are summarized. Poplar trees (Populus davidiana) growing on the Myoungbong tailings were suggested to be a potential species for revegetation of large scale Au mine tailings. Arsenic accumulations of bracken ferns (Pteridium aquilinum) sampled from the Duckum tailings were far lower than those of the reported hyperaccumulators, but the possible chronic adverse effects on residents through daily diet are of concern.     

Environmental risk assessment of metals contaminated soils at silvermines abandoned mine site,Co Tipperary,Ireland

A centuries long history of mining and mineral processing has resulted in elevated Cd, Pb and Zn soil concentrations in the vicinity of the Silvermines abandoned mine site (AMS), Co. Tipperary, Ireland. A process for preliminary evaluation of environmental risk was developed and implemented. Potential pathways of metal compound transport and deposition were mapped and used to optimise the subsequent site investigation. Elevated soil metals are shown to be predominantly in areas where metal deposition in soil is associated with water related pathways (surface runoff, seasonal groundwater seepage and floodplains). Extensive areas of soil in the surrounding district are classified as contaminated on the basis of Cd, Pb and Zn concentrations, both total and potential bioavailable (EDTA-extractable). The most affected areas, with metal concentrations in soil comparable with that within the AMS, were floodplains located 2–3 km downstream from the site. Assessment of the sequential effects on grass and grazing animals indicates that Pb poses the greatest risk due to its high toxicity and high concentrations in soil (more than 10 000 mg kg^–1). Within floodplain areas grazing cattle may intake a lethal dose of Pb. On the basis of the investigation an approach to risk assessment was developed which allowed quantified assessment of the risks related to individual metals, areas of contamination and contamination targets.     

Relationship between plant biodiversity and heavy metal bioavailability in grasslands overlying an abandoned mine

Abandoned metal mines in the Sierra de Guadarrama, Madrid, Spain, are often located in areas of high ecological value. This is true of an abandoned barium mine situated in the heart of a bird sanctuary. Today the area sustains grasslands, interspersed with oakwood formations of Quercus ilex and heywood scrub (Retama sphaerocarpa L.), used by cattle, sheep and wild animals. Our study was designed to establish a relationship between the plant biodiversity of these grasslands and the bioavailability of heavy metals in the topsoil layer of this abandoned mine. We conducted soil chemical analyses and performed a greenhouse evaluation of the effects of different soil heavy metal concentrations on biodiversity. The greenhouse bioassays were run for 6 months using soil samples obtained from the mine polluted with heavy metals (Cu, Zn, Pb and Cd) and from a control pasture. Soil heavy metal and Na concentrations, along with the pH, had intense negative effects on plant biodiversity, as determined through changes in the Shannon index and species richness. Numbers of grasses, legumes, and composites were reduced, whilst other species (including ruderals) were affected to a lesser extent. Zinc had the greatest effect on biodiversity, followed by Cd and Cu. When we compared the sensitivity of the biodiversity indicators to the different metal content variables, pseudototal metal concentrations determined by X-ray fluorescence (XRF) were the most sensitive, followed by available and soluble metal contents. Worse correlations between biodiversity variables and metal variables were shown by pseudototal contents obtained by plasma emission spectroscopy (ICP-OES). Our results highlight the importance of using as many different indicators as possible to reliably assess the response shown by plants to heavy metal soil pollution.     

Ameliorants to immobilize Cd in rice paddy soils contaminated by abandoned metal mines in Korea

The cadmium (Cd) content of rice grain grown in metal-contaminated paddy soils near abandoned metal mines in South Korea was found to exceed safety guidelines (0.2 mg Cd kg?1) set by the Korea Food and Drug Administration (KFDA). However, current remediation technologies for heavy metal-contaminated soils have limited application with respect to rice paddy soils. Laboratory and greenhouse experiments were conducted to assess the effects of amending contaminated rice paddy soils with zerovalent iron (ZVI), lime, humus, compost, and combinations of these compounds to immobilize Cd and inhibit Cd translocation to rice grain. Sequential extraction analysis revealed that treatment with the ameliorants induced a 50-90% decrease in the bioavailable Cd fractions when compared to the untreated control soil. When compared to the control, Cd uptake by rice was decreased in response to treatment with ZVI + humus (69%), lime (65%), ZVI + compost (61%), compost (46%), ZVI (42%), and humus (14%). In addition, ameliorants did not influence rice yield when compared to that of the control. Overall, the results of this study indicated that remediation technologies using ameliorants effectively reduce Cd bioavailability and uptake in contaminated rice paddy soils.     

Ameliorants to immobilize Cd in rice paddy soils contaminated by abandoned metal mines in Korea

The Yarlung Tsangbo (YT) is a large river running across southern Tibet and has significant effects on its lower reaches, the Ganges–Brahmaputra Basin. In order to investigate the geochemical features of the YT, 18 surface sediment samples were collected; ten trace element concentrations were measured for bulk sediments and two fine grain size fractions. Meanwhile, basic physicochemical parameters and element concentrations of river water were also analyzed. Results indicated that the river water was alkaline (pH 8.42) and that dissolved oxygen was mainly controlled by river water temperature. Some elements (e.g., Zn and Ni) showed close negative relationship to mean grain size of the sediments. Concentrations of most heavy metals, except As of the YT bulk sediments, were similar to those of Upper Crustal Concentration and its lower reaches, indicating almost no anthropogenic impact. Arsenic of the YT sediments was derived fundamentally from the parent rocks of the YT Basin and was far higher than that of its lower reaches. This indicates that relatively small amounts of As from the study area were transported down to the Brahmaputra River under present, relatively dry climatic conditions. However, more YT sediments might have been transported to its low reaches during the Holocene due to the wet climate, giving high As concentration in Holocene sediments of the Ganges–Brahmaputra Basin. Thus, As transported by the YT may produce important influence on the Ganges–Brahmaputra Basin and contribute to its high As concentration in groundwater.     

湖南省某矿遗址周围农业土壤重金属污染及风险评价

为了进一步了解湖南省某矿遗址周围农田土壤重金属的风险,在该矿遗址附近两个区域(Ⅰ区、Ⅱ区)采集125个农业土壤样品,分析其中重金属(As、Cd、Cr、Cu、Pb)的含量,运用综合污染评价法、潜在生态指数法和地积累指数法对其开展风险评估.结果表明,Ⅰ区农田土壤中As和Cd的含量比国家风险管控标准值高,属于中度污染土壤,存在着极高的潜在生态风险;地积累指数进一步指出Ⅰ区土壤中As污染属于二级污染、Cd污染属于四级污染.Ⅱ区农田土壤,除Cd的含量相对较高外,其它重金属含量均很低,该区域土壤重金属的综合污染评价值低于1.0.但是由于Ⅱ区土壤中Cd的地积累指数为1.92,表明Ⅱ区土壤受到Cd的轻度污染,存在一定的潜在风险.     

Stabilization of the As-contaminated soil from the metal mining areas in Korea

The stabilization efficiencies of arsenic (As) in contaminated soil were evaluated using various additives such as limestone, steel mill slag, granular ferric hydroxide (GFH), and mine sludge collected from an acid mine drainage treatment system. The soil samples were collected from the Chungyang area, where abandoned Au–Ag mines are located. Toxicity characteristic leaching procedure, synthetic precipitation leaching procedure, sequential extraction analysis, aqua regia digestion, cation exchange capacity, loss on ignition, and particle size distribution were conducted to assess the physical and chemical characteristics of highly arsenic-contaminated soils. The total concentrations of arsenic in the Chungyang area soil ranged up to 145 mg/kg. After the stabilization tests, the removal percentages of dissolved As(III) and As(V) were found to differ from the additives employed. Approximately 80 and 40% of the As(V) and As(III), respectively, were removed with the use of steel mill slag. The addition of limestone had a lesser effect on the removal of arsenic from solution. However, more than 99% of arsenic was removed from solution within 24 h when using GFH and mine sludge, with similar results observed when the contaminated soils were stabilized using GFH and mine sludge. These results suggested that GFH and mine sludge may play a significant role on the arsenic stabilization. Moreover, this result showed that mine sludge can be used as a suitable additive for the stabilization of arsenic.     

Stabilization of the As-contaminated soil from the metal mining areas in Korea

The stabilization efficiencies of arsenic (As) in contaminated soil were evaluated using various additives such as limestone, steel mill slag, granular ferric hydroxide (GFH), and mine sludge collected from an acid mine drainage treatment system. The soil samples were collected from the Chungyang area, where abandoned Au-Ag mines are located. Toxicity characteristic leaching procedure, synthetic precipitation leaching procedure, sequential extraction analysis, aqua regia digestion, cation exchange capacity, loss on ignition, and particle size distribution were conducted to assess the physical and chemical characteristics of highly arsenic-contaminated soils. The total concentrations of arsenic in the Chungyang area soil ranged up to 145 mg/kg. After the stabilization tests, the removal percentages of dissolved As(III) and As(V) were found to differ from the additives employed. Approximately 80 and 40% of the As(V) and As(III), respectively, were removed with the use of steel mill slag. The addition of limestone had a lesser effect on the removal of arsenic from solution. However, more than 99% of arsenic was removed from solution within 24 h when using GFH and mine sludge, with similar results observed when the contaminated soils were stabilized using GFH and mine sludge. These results suggested that GFH and mine sludge may play a significant role on the arsenic stabilization. Moreover, this result showed that mine sludge can be used as a suitable additive for the stabilization of arsenic.     

Stabilization of the As-contaminated soil from the metal mining areas in Korea

Phytoextraction is a remediation technology with a promising application for removing arsenic (As) from soils and waters. Several plant species were evaluated for their As accumulation capacity in hydroponic culture amended with As. Cucumis sativus (cucumber) displayed the highest tolerance against As among 4 plants tested in this study (corn, wheat, sorghum and cucumber). The germination ratio of Cucumis sativus was more than 50% at the high concentration of 5,000 mg-As/l. In Cucumis sativus grown in a solution contaminated with 25 mg-As/l, the accumulated As concentrations in the shoot and root were 675.5 ± 11.5 and 312.0 ± 163.4 mg/kg, respectively, and the corresponding values of the translocation and bioaccumulation factors for As were 1.9 ± 0.9 and 21.1 ± 8.4, respectively. These results indicate Cucumis sativus is to be a candidate plant for phytoextraction of As from soils and water.     

Risk assessment of bioaccessible arsenic and cadmium exposure through rice consumption in local residents of the Mae Tao Sub-district,Northwestern Thailand

Environmental Geochemistry and Health - Consumption of contaminated rice is a toxin exposure route in Asian populations. Since total concentrations generally overestimate health risks, the...     

某典型废弃硫酸场地土壤重金属污染特征与评价

硫酸生产场地可能存在严重的土壤重金属污染,调查并分析硫酸场地土壤重金属污染及迁移规律是其安全利用的基础.本研究以某废弃硫酸场地为例,采集0-3 m深度范围的土壤样品,测定其中的Pb、Cd、Cu、Ni、As、Hg含量,分析重金属的空间分布特征、来源及迁移行为,并对其进行内梅罗综合污染指数和潜在生态风险指数评价.结果 表明...     

Regional human health risk assessment of cadmium and hexachlorocyclohexane for agricultural land in China

Widespread pollution of agricultural soil is posing great risks to food safety and human health. The absence of human health-based Generic Assessment Criteria (GAC) for agricultural land means Chinese farmers struggle to manage these risks efficiently and effectively. Cadmium (Cd) and hexachlorocyclohexane (HCH), two of the most concerned contaminants, demonstrate threshold toxicity meaning that background exposure (MDI_oral) is considered when deriving soil Generic Assessment Criteria (GAC). The CLEA (Contaminated Land Exposure Assessment) model was used to derive GAC for Cd and HCH that reflect differences in diet and soil characteristics across 19 provinces/cities. For both cadmium and alpha-HCH, Sichuan had the lowest GAC of 0.379 mg kg^?1 and 0.0136 mg kg^?1, respectively, resulting from its significant high MDI_oral values, which are approximately six to nine times larger than the average MDI_oral for all the 19 provinces/cities. Jiangxi province had the highest GAC of 1.230 mg kg^?1 and 0.0866 mg kg^?1, respectively, for cadmium and alpha-HCH, caused by its notable low MDI_oral values and low vegetable consumption rate. Human health risk assessment based on regional GAC for Cd revealed that agricultural land with very high to high risks is located in southern China, while very low-risk land is located in northern China. For HCH, alpha- and gamma-HCH pose negligible health risks, but beta-HCH poses some health risk in some of the provinces/cities. When applying the regional GAC for beta-HCH, agricultural land in Beijing and Sichuan posed the highest risk, and those in Heilongjiang and Jiangxi had the lowest risk. This reflects the significant influence of background and vegetable consumption pathway on the GAC. Regional GACs could simplify and speed up risk assessment of agricultural land in different regions of China, by avoiding the need to calculate site-specific assessment criteria, thus saving time and money by avoiding over or under remediation.