Remediation of soils contaminated with heavy metals with an emphasis on immobilization technology.

The major frequent contaminants in soil are heavy metals which may be responsible for detrimental health effects. The remediation of heavy metals in contaminated soils is considered as one of the most complicated tasks. Among different technologies, in situ immobilization of metals has received a great deal of attention and turned out to be a promising solution for soil remediation. In this review, remediation methods for removal of heavy metals in soil are explored with an emphasis on the in situ immobilization technique of metal(loid)s. Besides, the immobilization technique in contaminated soils is evaluated through the manipulation of the bioavailability of heavy metals using a range of soil amendment conditions. This technique is expected to efficiently alleviate the risk of groundwater contamination, plant uptake, and exposure to other living organisms. The efficacy of several amendments (e.g., red mud, biochar, phosphate rock) has been examined to emphasize the need for the simultaneous measurement of leaching and the phytoavailability of heavy metals. In addition, some amendments that are used in this technique are inexpensive and readily available in large quantities because they have been derived from bio-products or industrial by-products (e.g., biochar, red mud, and steel slag). Among different amendments, iron-rich compounds and biochars show high efficiency to remediate multi-metal contaminated soils. Thereupon, immobilization technique can be considered a preferable option as it is inexpensive and easily applicable to large quantities of contaminants derived from various sources.

Accumulation of metals in three fish species from the Yaounde Municipal Lake in Cameroon.

Metals are dangerous to aquatic organisms and they can bioaccumulate in the food chain and represent risk for humans. In order to appraise their levels in fish species, concentrations of various elements including Na, Mg, K, Ca, Al, Fe, Mn, Cr, Ni, Co, Cd, Cu, Pb, Zn, Ba, and Sr were determined in the muscles and gills of three fish species (Oreochromis niloticus, Sarotherodon galilaeus, and Clarias sp.) which are more fished and consumed in the Yaounde Municipal Lake, Cameroon. According to chemical results of the fish samples analyzed by ICP-AES, the concentrations of metals (mg kg(-1), wet tissues) in those fish tissues varied as follows for the muscle (and gill) Na 1480-3780 (4180-9310), Mg 897-1250 (843-1450), K 9600-18,500 (6020-10,400), Ca 430-3900 (22,200-62,400), Al 8.10-615 (113-951), Fe 12.0-725 (307-1160), Mn 1.61-30.1 (14.3-433), Cr 1.58-267 (0.31-35.4), Ni 0.16-1.85 (1.06-2.82), Co 0.10-0.47 (0.07-0.16), Cd 0.11-0.23 (0.10-0.22), Cu 0.59-5.13 (1.31-5.13), Pb 1.11-5.12 (2.56-5.74), Zn 15.4-47.2 (45.3-69.2), Ba 0.61-51.15 (0.35-83.2), and Sr 2.31-5.74 (2.09-5.75). The results revealed that Na, Ca, Zn, Fe, and Mn were higher concentrated in the gills than in the muscles, while K, Cr, Ni, Co, and Cd were more concentrated in the muscles of the species. In addition, all the elements were bioaccumulated in the fish species and the bioaccumulation factors (BAFs) were decreased in the following order: Cr > Ni > Zn > Al > Ca > Pb > Mn > Ba > K > Fe > Mg > Cu > Na > Sr > Co > Cd. Compared to international standards, Pb, Cd, Cr, Ni, and Zn were over the recommendations of the European Community, WHO, and Norwegian guidance values for human health. Therefore, fishes from the Yaounde Municipal Lake are not advised for human consumption as toxic elements might be taken above the recommended levels.

A simple approach for measuring emission patterns of vapor phase mercury under temperature-controlled conditions from soil.

In an effort to study the possible effects of climate change on the behavior of atmospheric mercury (Hg), we built a temperature-controlled microchamber system to measure its emission from top soils. To this end, mercury vapour emission rates were investigated in the laboratory using top soil samples collected from an urban area. The emissions of Hg, when measured as a function of soil temperature (from ambient levels up to 70°C at increments of 10°C), showed a positive correlation with rising temperature. According to the continuous analyses of the Hg vapor given off by the identical soil samples, evasion rate diminished noticeably with increasing number of repetitions. The experimental results, if examined in terms of activation energy (Ea), showed highly contrasting patterns between the single and repetitive runs. Although the results of the former exhibited Ea values smaller than the vaporization energy of Hg (i.e., <14 Kcal mol(-1)), those of the latter increased systematically with increasing number of repetitions. As such, it is proposed that changes in the magnitude of Ea values can be used as a highly sensitive criterion to discriminate the important role of vaporization from other diverse (biotic/abiotic) processes occurring in the soil layer.

Mercury contamination in agricultural soils from abandoned metal mines classified by geology and mineralization.

This survey aimed to compare mercury concentrations in soils related to geology and mineralization types of mines. A total of 16,386 surface soils (0~15 cm in depth) were taken from agricultural lands near 343 abandoned mines (within 2 km from each mine) and analyzed for Hg by AAS with a hydride-generation device. To meaningfully compare mercury levels in soils with geology and mineralization types, three subclassification criteria were adapted: (1) five mineralization types, (2) four valuable ore mineral types, and (3) four parent rock types. The average concentration of Hg in all soils was 0.204 mg kg(-1) with a range of 0.002-24.07 mg kg(-1). Based on the mineralization types, average Hg concentrations (mg kg(-1)) in the soils decreased in the order of pegmatite (0.250) > hydrothermal vein (0.208) > hydrothermal replacement (0.166) > skarn (0.121) > sedimentary deposits (0.045). In terms of the valuable ore mineral types, the concentrations decreased in the order of Au-Ag-base metal mines ≈ base metal mines > Au-Ag mines > Sn-W-Mo-Fe-Mn mines. For parent rock types, similar concentrations were found in the soils derived from sedimentary rocks and metamorphic rocks followed by heterogeneous rocks with igneous and metamorphic processes. Furthermore, farmland soils contained relatively higher Hg levels than paddy soils. Therefore, it can be concluded that soils in Au, Ag, and base metal mines derived from a hydrothermal vein type of metamorphic rocks and pegmatite deposits contained relatively higher concentrations of mercury in the surface environment.

Sequential Application of Column Leaching and Plant Uptake Tests to Assess the Effect of Various Commercial Amendments on Cu Immobilization in Ultra-High Cu-Contaminated Soil.

The presence of copper (Cu)-contaminated soil has increased recently due to agricultural and industrial activities. Immobilization techniques using soil amendments have attracted significant research because of their cost-effectiveness, eco-friendliness, and community acceptance. This study used various commercial amendments, including magnetite (M), talc (T), activated carbon (AC), and cornstarch (CS), to immobilize Cu in soil contaminated by acidic waste materials with Cu in Korea (9546 ± 5 mg/kg). To evaluate the immobilizing effect of these amendments, this study applied a sequential process of column leaching and plant uptake tests to observe the ability of Cu to remain in soil with and without amendments through the Cu removal rate. The amendments were characterized by SEM, XRD, and specific surface area and applied to the soil at a rate of 2% (w/w). The first stage of evaluation, i.e., the column leaching test, was conducted by continuously pumping distilled water (DW) for 28 days, and the second stage of evaluation, i.e., the plant uptake test, was started immediately after by planting 10-day-old lettuce seedlings for 28 days. The experimental results showed that all of the amendments had a significant effect on Cu immobilization Cu in soil (p < 0.05), and the T treatment showed the highest efficiency in Cu immobilization, with only 47.0% Cu loss compared to 73.5% in the control soil when assessed by sequential column leaching and plant uptake tests. In conclusion, this study provides an effective assessment method to evaluate the effect of amendments on Cu immobilization in soil, as well as providing feasible options to immobilize Cu using commercial amendments.

Environmental Assessment of Friable Asbestos from Soil to Air Using the Releasable Asbestos Sampler (RAS).

The objectives of this study are to examine the feasibility of the releasable asbestos sampler (RAS) equipment for laboratory tests as an alternative to activity-based sampling (ABS), and to apply the equipment controlled by wind velocity and water contents in the field to asbestos-contaminated soils. Two asbestos-contaminated mines (the Jecheon mine and the Jongmin-ri mine) were selected. At each mine, 21 surface soils (0~15 cm) were sampled, the asbestos concentrations were analyzed, and then three representative sites, containing 0.25%, 0.50%, and 0.75% of asbestos in soils, were chosen to evaluate the amount of releasable asbestos by the modified RAS with wind velocity and water contents. The results showed that the levels of releasable asbestos from soil to air increased with higher wind velocities and lower water content. In addition, the application of risk assessment of releasable asbestos in the soils as an alternative to the activity-based sampling (ABS) method was established at each site, and an estimation of the excess lifetime cancer risk (ELCR) was also calculated. According to the calculation, the estimated ELCR values did not exceed the threshold value (1 × 10-4) in the Jecheon mine for all the soils, while some samples from the Jongmin-ri mine exceeded the threshold value. Therefore, proper remediation work is needed to control friable asbestos from soils to air in the vicinity of the mines.

Relative extraction ratio (RER) for arsenic and heavy metals in soils and tailings from various metal mines, Korea.

This study focused on the evaluation of leaching behaviours for arsenic and heavy metals (Cd, Cu, Ni, Pb and Zn) in soils and tailings contaminated by mining activities. Ten representative mine soils were taken at four representative metal mines in Korea. To evaluate the leaching characteristics of the samples, eight extraction methods were adapted namely 0.1 M HCl, 0.5 M HCl, 1.0 M HCl, 3.0 M HCl, Korean Standard Leaching Procedure for waste materials (KSLP), Synthetic Precipitation Leaching Procedure (SPLP), Toxicity Characteristic Leaching Procedure (TCLP) and aqua regia extraction (AR) methods. In order to compare element concentrations as extraction methods, relative extraction ratios (RERs, %), defined as element concentration extracted by the individual leaching method divided by that extracted by aqua regia based on USEPA method 3050B, were calculated. Although the RER values can vary upon sample types and elements, they increase with increasing ionic strength of each extracting solution. Thus, the RER for arsenic and heavy metals in the samples increased in the order of KSLP < SPLP < TCLP < 0.1 M HCl < 0.5 M HCl < 1.0 M HCl < 3.0 M HCl. In the same extraction method, the RER values for Cd and Zn were relatively higher than those for As, Cu, Ni and Pb. This may be due to differences in geochemical behaviour of each element, namely high solubility of Cd and Zn and low solubility of As, Cu, Ni and Pb in surface environment. Thus, the extraction results can give important information on the degree and extent of arsenic and heavy metal dispersion in the surface environment.

Solidification of arsenic and heavy metal containing tailings using cement and blast furnace slag.

The objective of this study is to examine the solidification of toxic elements in tailings by the use of cement and blast furnace slag. Tailings samples were taken at an Au-Ag mine in Korea. To examine the best mixing ratio of tailings and the mixture of ordinary Portland cement (OPC) and blast furnace slag (SG) of 5:5, 6:6, 7:3, and 8:2, the 7:3 ratio of tailings and OPC+SG was adapted. In addition, the mixing ratios of water and OPC + SG were applied to 10, 20, and 30 wt%. After 7, 14, and 28 days' curing, the UCS test was undertaken. A relatively high strength of solidified material (137.2 kg cm⁻² in average of 3 samples) at 28 days' curing was found in 20 wt% of water content (WC). This study also examined the leachability of arsenic and heavy metals (Cd, Cu, Pb, and Zn) under the Korean Standard Leaching Test, and it showed that the reductions in leachabilities of As and heavy metals of solidified samples were ranged from 76 to 99%. Thus, all the solidified samples were within the guidelines for special and hazardous waste materials by the Waste Management Act in Korea. In addition, the result of freeze-thaw cycle test of the materials indicated that the durability of the materials was sufficient. In conclusion, solidification using a 7:3 mixing ratio of tailings and a 1:1 mixture of OPC + SG with 20% of WC is one of the best methods for the remediation of arsenic and heavy metals in tailings and other contaminated materials.

Mobility of metal(loid)s in roof dusts and agricultural soils surrounding a Zn smelter: Focused on the impacts of smelter-derived fugitive dusts.

The mobility of Zn, Cd, Pb, Cu, and As was assessed in an atmospheric environment and soil system near a Zn smelter by performing sequential extraction as well as Pb isotopic and mineralogical analyses for fugitive and roof dusts and agricultural soils. Transmission electron microscopy observations with selected area electron diffraction patterns confirmed that micron-sized roof dusts originated from the Zn smelter. Both fugitive and roof dusts contained zincite, massicot, franklinite, anglesite, and willemite. The sequential extraction of the fugitive dust from the Zn smelter stacks showed that Zn, Cd, and Pb were predominantly bound to the exchangeable (FI), carbonate (FII), and reducible (FIII) fractions, whereas Cu and As were significantly associated with the residual (FV) fraction and had low mobility. The estimation of remobilized concentrations of Zn, Cd, and Pb bound to labile fractions (FI and FII) in the fugitive dust implied their severe environmental and human health risks. In contrast, the studied metal(loid)s in the roof dust had low mobility except for Pb, implying the insignificant risks of roof dusts, although anthropogenic dusts from the Zn smelter significantly impacted FV as well as the non-residual fractions based on the Pb isotopic compositions of geochemical fractions. Similarly, the mobility and bioavailability of the studied metal(loid)s were low in agricultural soils, except for Cd, suggesting a low adverse effect on crops cultivated in the soil. The decrease in labile Cd fractions with depth indicated that the agricultural soil did not retain anthropogenic Cd in the soil subsurface. The mineralogical investigation combined with sequential extraction revealed that the different mobility of Zn, Cd, and Pb between fugitive dusts, roof dusts and agricultural soils resulted from the different solubility of metal-bearing minerals, e.g., zincite, willemite, simonkolleite which were not detected in the residuals of the fugitive dust collected after FIII extraction.

Effects of fine fractions of soil organic, semi-organic, and inorganic amendments on the mitigation of heavy metal(loid)s leaching and bioavailability in a post-mining area.

This study investigated the effects of soil amendments including biomasses (rice husk, RRH and maple leaf, RML), biochar (rice husk biochar, RHB and maple leaf biochar, MLB), and industrial by-products (red mud, RM and steel slag, SS), at two application rates (0, 1, and 2% w/w) on leaching and bioavailability of heavy metal(loid)s (HMs) (As, Cd, Cu, Pb, and Zn) in the presence of an Asteraceae (i.e., lettuce). Physicochemical properties of the soil (i.e., pH, EC, CEC, and HMs leaching) and plants were examined before and after amending. The addition of amendments significantly (p < 0.05) increased soil EC (from 100 to 180 µScm-1) and CEC (from 7.6 to 15 meq100 g-1). Soil pH from 6.7 ± 0.05 increased about 2 units with increasing in the application rate of MLB, RM, and SS, while it decreased about 0.8 units in RML amended soil. Soil amendments reduced the easily leachable fractions (exchangeable and carbonate) of HMs in the order of MLB > SS > RM > RHB. The average concentration of Cd, Cu, Pb, and Zn in plant roots and shoots decreased >30 wt% in biochars and industrial by-products amended soils, while biomasses mitigated As uptake in lettuce. Results demonstrated that adding maple-derived biochar combined with revegetation effectively immobilized HMs in a post-mining area beside an induce in plant growth parameters.

BBQ charcoal as an important source of mercury emission.

In this study, the environmental significance of mercury emission has been investigated with respect to the use of the barbecue (BBQ) charcoal. For this purpose, emission gas samples collected from a total of 11 barbecue charcoal products commonly available in the Korean market were analyzed. All of these products consist of both domestic (4 types) and imported products (7 types from three countries). The emission concentration of Hg varied widely from sample to sample ranging from 114 to 496ngm(-3). The amount of Hg emission appeared to be affected by the diverse nature of raw materials and/or the processes involved in their production. In light of the recent reference exposure limits (REL) of Hg, it can be a potential threat to human health. As such, a proper regulation is desirable from a toxicological viewpoint to reduce the potential risk associated with the use of BBQ charcoal.

The effects of soil properties on the turbidity of catchment soils from the Yongdam dam basin in Korea.

Environmental concerns have been raised that suspended solids in turbid water adversely affect human health, and that their removal increases in the cost of water treatment. The Yongdam dam reservoir, located in the southwestern region of Korea, is severely affected by inflowing turbid water after storms. In this study, soil samples were collected from 37 sites in the Yongdam upstream basin to investigate mineralogical and environmental factors associated with the turbidity potential of soils in water environments. Turbidity potential was estimated by measuring the turbidity of soil-suspension solutions after settling for 24 h. The mineralogy of the soils was dominated by four minerals-quartz, microcline, albite, and muscovite-with lesser amounts of hornblende, chlorite, kaolinite, illite, and mixed layer illite. The quartz content was the most variable of the soil mineralogy among the collected samples. Principal-components analysis (PCA) was used to examine relationships between turbidity potential and other soil properties. The variables considered in the PCA included turbidity potential, quartz content, albite content, mean size of soil particles, clay content, clay mineral content, zeta potential, conductivity, and pH of the soil-suspension solution. The first two components of the PCA explained 52% of the overall variation of the selected variables. The first component was possibly explained by physical properties such as the size of the soil particles; the second was correlated with chemical properties of the soils, for example dissolution and extent of weathering. Closer examination of the PCA results revealed that the quartz content of the soils was negatively correlated with their turbidity potential. A linear correlation (r = 0.63) was obtained between measured turbidity potential and that predicted using multiple regression analysis based on the content of clay-sized particles, clay minerals, and quartz, and the conductivity of the soil-suspension solution.

Heavy Metal Concentrations in Soils and Factors Affecting Metal Uptake by Plants in the Vicinity of a Korean Cu-W Mine.

Heavy metal concentrations were measured in soils and plants in and around a copper-tungsten mine in southeast Korea to investigate the influence of past base metal mining on the surface environment. The results of chemical analysis indicate that the heavy metals in soils decreased with distance from the source, controlled mainly by water movement and topography. The metal concentrations measured in plant species generally decreased in the order; spring onions > soybean leaves > perilla leaves ¼ red pepper > corn grains ¼ jujube grains, although this pattern varied moderately between different elements. The results agree with other reports that metal concentrations in leaves are usually much higher than those in grain. Factors influencing the bioavailability of metals and their occurrences in crops were found as soil pH, cation exchange capacity, organic matter content, soil texture, and interaction among the target elements. It is concluded that total metal concentrations in soils are the main controls on their contents in plants. Soil pH was also an important factor. A stepwise linear multiple regression analysis was also conducted to identify the dominant factors influencing metal uptake by plants. Metal concentrations in plants were also estimated by computer-aided statistical methods.

Arsenic, Sb and Bi contamination of soils, plants, waters and sediments in the vicinity of the Dalsung Cu-W mine in Korea.

The objective of this study is to investigate environmental contamination derived from metalliferous mining activities. In the study area, the Dalsung Cu-W mine, soils, various crop plants, stream waters, sediments and particulates were sampled in and around the mine and analyzed for As, Sb and Bi by ICP-AES with a hydride generator. In addition, soil pH, cation exchange capacity, loss-on-ignition and soil texture were also measured. Concentrations of As, Sb and Bi in surface soils sampled in the mine dump sites averaged 2500, 54 and 436 microg g(-1), respectively. Relatively lower concentrations, however, were found in soils from alluvial and high land sites and household garden sites. Arsenic, Sb and Bi contents in plant samples varied depending upon their species and parts, with higher concentrations in spring onions, soybean leaves and perilla leaves and lower levels in red peppers, corn grains and jujube grains. These results confirm that elemental concentrations in plant leaves are much higher than those in plant grain. Elevated levels of As, Sb and Bi were also found in stream sediments sampled in the vicinity of the mine and decreased with distance from the mine. Concentrations in stream water samples ranged from 0.8 to 19.1 microg As l(-1) and from 0.3 to 8.4 microg Bi l(-1); all the samples contained less than 1.0 microg Sb l(-1). Because of very low particulate loading at the time of sampling, the metal contents in particulates were very low (< 8.2 microg As l(-1), < 0.22 microg Sb l(-1) and 2.8 microg Bi l(-1). This may be mainly due to the low solubility of those elements under moderately acidic and oxidizing conditions of the mining area.

The impact of mining activities in alteration of As levels in the surrounding ecosystems: an encompassing risk assessment and evaluation of remediation strategies.

A comprehensive field survey was conducted to explore the status of arsenic (As) contamination in soil and water systems surrounding numerous abandoned mine sites in Korea, which were previously applied with soil-topping (15 cm deep) and lime treatment for remediation purposes. This survey also aimed to assess the environmental stability of those reservoirs in relation to their established guidelines for As. To this end, a total of 5837 target soils (TS) were analyzed along with 305 control soils (CS) and 74 tailing (TA) samples. In addition, analyses were also extended to cover 1066 water and 329 sediment samples. Substantial evidence (e.g., differences in the mean As levels between TS (12.7 mg kg(-1)) and CS (0.69 mg kg(-1)) and the strong correlation between TS and TA) suggests a strong effect of previous mining activities. Soil-topping method was successful in confining As at the subsurface soil and restraining its dispersal. Although soil pH level also dropped with increasing As, it was restored to near neutrality by liming treatment. The mean values of As in water samples are comparable between dry (22.2) and wet seasons (21.2 mg L(-1)), while its values frequently exceeded various guideline limits. The pollution status of the current land and water systems needs to be assessed properly along with a removal plan for mine wastes/tailings to limit the dispersion of As in the study area.

BBQ charcoal combustion as an important source of trace metal exposure to humans.

To provide information about charcoal combustion as an important source of atmospheric trace metal pollution, 11 charcoal products were combusted and PM(10) filter samples were collected. The PM-bound metal elements were extracted by microwave acid digestion and analyzed by ICP-AES. The concentrations of trace metal elements ranged from a few to 10(5)ng m(-3) in the following order of magnitude: Zn>Pb>Mg>Ba>Cu>V>Cr>Co>Cd>Ni>Mn>Se>As. Emissions of most elements from charcoal combustion were high compared to other sources. In case of Cd, Co, and Ni, their concentrations exceeded the inhalation minimum risk levels (MRLs) of the United States Agency for Toxic Substances and Disease Registry (US-ATSDR) for chronic duration exposure by a factor of 30, 3.9, and 2.2, respectively. Likewise, Cd levels exceeded the US-ATSDR MRLs for acute-duration exposure by a factor of 10, while those of Pb and Cd exceeded air quality guideline (AQG) of the World Health Organization (WHO) by a factor of 29 and 59, respectively. Mn levels also exceeded the United States Environmental Protection Agency (US EPA) Reference Air Concentrations (RfCs) by a factor of 2.7. This study shows that barbecue charcoal combustion can be an important source of trace metal emissions to the atmosphere with potential health risks.

Airborne mercury pollution from a large oil spill accident on the west coast of Korea.

Atmospheric mercury pollution was recognized after a large oil spill on the west coast of Korea on 7 December 2007. In this study, the concentrations of gaseous elemental mercury (GEM: Hg(0)) in air were measured both shortly after the oil spill ( approximately 100h) and 1month after the accident near the accident site. When the Hg concentration levels were compared between two seashore sites and two parallel sites offshore, the values tend to decrease further offshore. The unusual rise in Hg concentration levels observed on the seashore area shortly after the accident (mean of 16.4+/-9.85ngm(-3)) dropped dramatically after 1month with active cleanup activities (2.99+/-1.40ngm(-3)). Because of the connection between crude oil and Hg (one of the major impurities), the unusual rise in the atmospheric Hg after the oil spill can be explained by the active evasion of Hg from the spilled crude oil. Although Hg levels determined a few days after the accident did not exceed the reference exposure limits (REL) proposed by several agencies, the early build-up of elemental mercury level due to the oil spill might have exerted certain impacts on the surrounding environments.

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 microm. 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.

In-situ electrochemical measurements of total concentration and speciation of heavy metals in acid mine drainage (AMD): assessment of the use of anodic stripping voltammetry.

We assessed the use of anodic stripping voltammetry (ASV) for in-situ determinations of both total concentration and speciation of dissolved heavy metals (Cd, Cu, Pb and Zn) in acid mine drainage (AMD). In the Kwangyang Au-Ag mine area of South Korea, different sites with varying water chemistry within an AMD were studied with a field portable anodic stripping voltammeter. Anodic stripping voltammetry after wet oxidation (acidification) was very sensitive enough to determine total concentration of dissolved Cd because Cd was dominantly present as 'labile' species, whilst the technique was not so effective for determining total Cu especially in the downstream sites from the retention pond, due to its complexation with organic matter. For dissolved Pb, the concentrations determined by ASV after wet oxidation generally agreed with those by ICP-AES. In the downstream samples (pH>5), however, ASV data after wet oxidation were lower than ICP-AES data because a significant fraction of dissolved Pb was present in those samples as 'inert' species associated with colloidal iron oxide particles. The determination of total dissolved Zn by ASV after wet oxidation appeared to be unsatisfactory for the samples with high Cu content, possibly due to the interference by the formation of Zn-Cu intermetallic compounds on the mercury coated electrode. In AMD samples with high dissolved iron, use of ultraviolet irradiation was not effective for determining total concentrations because humate destruction by UV irradiation possibly resulted in the removal of a part of dissolved heavy metals from waters through the precipitation of iron hydroxides.

Baseline study on essential and trace elements in polished rice from South Korea.

In 2000, 63 (polished) white rice samples were collected in eight administrative areas all over South Korea and analyzed for 16 elements by inductively coupled plasma atomic emission spectrometry (ICP-AES). Potassium had the highest content, next to Mg, Ca, Si, Zn, Na, Al and Fe. Most of the samples contained worldwide average concentrations of essential and trace elements in rice grains reported by various researches. For inter-area differences in those elements in the rice, the statistical analysis showed no significant differences (p > 0.05) among the eight administrative areas, suggesting that inter-area differences were not substantial in most cases. Thus, the present data can be used as national background levels of elements in rice produced in South Korea. Using the published data on daily consumption of rice in South Korea, it was possible to estimate the daily intake of As, Cd, Cu, Pb and Zn via rice. The results showed that a regular consumption of rice produced in Korea plays an important role in accumulation of essential and trace elements in Korean, especially for farm-households consuming relatively large amounts of rice.