Heavy metal pollution in soil and plants at bone char site

This study determined the heavy metal concentration in soil and plants at a bone char site in Umuahia, Nigeria. Soil and plant samples collected in a randomized complete block design (RCBD) were analyzed for zinc (Zn), lead (Pb), cadmium (Cd), nickel (Ni), and arsenic (As). The concentration of metals in soil and plants in the vicinity of the bone char site are as follows: Zn (172?mg?kg^?1) and Ni (0.62?mg?kg^?1) in soil were highest at site P₃, Pb (2.37?mg?kg^?1) and As (0.08?mg?kg^?1) at site P₁, and Cd (18.30?mg?kg^?1) at site P₂. In plants, the concentrations of Zn (41.17?mg?kg^?1) and Cd (3?mg?kg^?1) were highest in Albizia ferruginea, Ni in Dialium guineense (0.09?mg?kg^?1), while Pb was in D. guineense (0.08?mg?kg^?1) and Spathodea companulata (0.06?mg?kg^?1). The levels of Zn, Cd, Pb, Ni, and As in soil ranged from 11.2 to 172, 2.68 to 18.2, 0.026 to 2.37, 0.33 to 0.62, and 0.02 to 0.08?mg?kg^?1, respectively. In plants, the concentration of Zn, Cd, Pb, and Ni ranged from 2.01 to 41.17, 0.12 to 3, 0.02 to 0.08, and 0.03 to 0.09?mg?kg^?1, respectively. There were significant correlations between Zn and Cd, and Pb and As in soil. The high concentration of Cd in soil might affect soil productivity.     

Determination of the levels of selected metals in seeds,flowers and fruits of medicinal plants used for tapeworm treatment in Ethiopia

The level of accumulation of selected essential and non-essential metals, namely; Ca, Cu, Fe, Zn, Mn, Cd, Pb, and Cr have been investigated in the seeds, fruits, and flowers of some medicinal plants utilized for tapeworm treatment in Ethiopia and their respective soil samples. These include seed of Cucurbita maxima (Duba), fruit of Embelia abyssinica (Ankoko), flowers of Hagenia abyssinica (Kosso), and fruits of Rosa abyssinica (Kega) and their respective soil samples. A wet digestion procedure with a mixture of conc. HNO₃ and HClO₄ for the plant samples and a mixture of conc. HNO₃, HCl, and H₂O₂ for soil samples were used to solubilize the metals. Ca (1280–12,670?mg?kg^?1) was the predominant metal followed by Fe (104–420?mg?kg^?1), and Zn (18–185?mg?kg^?1) in all the plant materials except for Hagenia abyssinica flower from Hirna in which Mn (16–42?mg?kg^?1) followed by Fe. Among the non-essential toxic metals, Pb was not detected in Cucurbita maxima of Boji, Gedo and Hirna origins and in Rosa abyssinica of Hirna site. Similarly, Cr was not detected in Rosa abyssinica fruits of Boji and Gedo sites. The sampled soils were found to be between strongly acidic to weakly basic (pH: 4.7–7.1). In the soil samples, Ca (8528–18,900?mg?kg^?1) was the most abundant metal followed by Fe (417–912?mg?kg^?1), Zn (155–588?mg?kg^?1), Mn (54–220?mg?kg^?1), Cr (21–105. mg?kg^?1), Cu (11–58?mg?kg^?1), Pb (13–32?mg?kg^?1) and Cd (2.8–4.8?mg?kg^?1). The levels of most of the metals determined in the medicinal plants and the respective soil samples are in good agreement with those reported in the literature and the standards set for the soil by various legislative authorities.     

Analysis of heavy metals in ecstasy tablets by electrochemical methods

Trace amounts of heavy metals have been analysed by electrochemical techniques in ecstasy tablets obtained from different police seizures in Spain. Lead, cadmium, copper and zinc were determined by differential-pulse anodic stripping voltammetry at a hanging mercury drop electrode, whereas nickel and cobalt were determined by adsorptive differential-pulse cathodic stripping voltammetry from their dimethylglyoxime complexes, M(DMG)₂. The performance of the procedure was compared with electrothermal atomic absorption spectrometry. The procedure was applied to the determination of these elements in nine ecstasy samples, finding that Zn is the element present in the highest concentration, ranging from 0.3 to 200?mg?kg^?1, Ni, Cu appear below 15?mg?kg^?1 and Pb below 8?mg?kg^?1, while Cd and Co levels were always lower than 0.51?mg?kg^?1.     

Metal levels in computer monitor components discarded in the vicinities of electronic workshops

Levels of Pb, Ni, Cr, Cu, Zn, and Cd in the glass screens (GS) and printed wiring boards (PWBs) of obsolete computer monitors (OCMs) were determined by flame atomic absorption spectrophotometry (FAAS) following standard digestion. Metal concentrations (mg kg^?1) in GS were in the following ranges (medians in brackets): Pb ND – 3100 (46), Cd 0.5–2.6 (0.8), Cr ND – 18.7 (3.1), and Zn 8.1–600 (37) and in PWBs (mg kg^?1): Pb 34,600 ± 17,000, Cd 11 ± 9, Cr 59 ± 45, Zn 15,900 ± 7800, Cu79,000 ± 22,600, and Ni 3200 ± 2500. In GS, the levels of the six metals were lower than their total threshold limit concentrations (TTLC), except for Pb with a TTLC of 1000 mg kg^?1 in 10% of the samples. In the PWBs, the TTLC of Pb and Cu (2500 mg kg^?1) was exceeded many fold. For Zn (5000 mg kg^?1) and Ni (2000 mg kg^?1); they were exceeded by 90% and 65%, respectively. For OCMs manufactured in 2001 and later, Pb and Zn levels in GS and Cr, Zn, and Ni in PWBs were significantly reduced.     

Distributions of total metals in the surface sediments of the Bandirma and Erdek Gulfs,Marmara Sea,Turkey

The aim of this study is to determine the contents of aluminum, iron, manganese, nickel, copper, zinc, chromium, cadmium, lead, and mercury in sediments at 1–30?m depths of the Band?rma and Erdek Gulfs in the Southern Inner Shelf of the Marmara Sea. Sediment samples were collected from different depths (1?m, 5?m, 10?m, 20?m, 30?m) at each region in February 2008. Primary hydrographic conditions, such as temperature (6.6–14.5°C), salinity (22.6–26.875 psu), percentage of dissolved oxygen saturation (35–83 %), and pH (8.0–8.4) were recorded for each sampling point. Moreover the total organic carbon (0.5–2.9%) and the total calcium carbonate contents (0.8–60%) of sediment samples were determined. In surface sediments of both gulfs, Pb (21–62?mg?kg^?1) and Cd (0.52–0.86?mg?kg^?1) contents were determined to be higher than the shale average (Pb 20?mg?kg^?1, Cd 0.2?mg?kg^?1) while the other metal contents were measured to be lower in general. On the other hand, generally Hg (0.06–1.1?mg?kg^?1) contents were higher than the shale average (0.3?mg?kg^?1)at all of the examined stations in the Band?rma Gulf and lower than the shale average in the Erdek Gulf.     

Abstracts to forthcoming papers

Food is the major source of metal exposure for the nonsmoking general population. Food samples of plant and animal origin from Ismailia, Egypt, were analyzed for the content of cadmium (Cd), lead (Pb), chromium (Cr), zinc (Zn), and copper (Cu) using AAS. The Cr, Zn, and Cu concentrations were in the range of 1.7–249?µg?kg^?1 wet weight (ww), 2–66?mg?kg^?1?ww, and 0.5–3.46?mg?kg^?1?ww, respectively. The mean daily intake of Cr, Zn, and Cu was 28.9?µg day^?1, 8.55?mg day^?1, and 1.7?mg day^?1, respectively. The intake estimates are within the range of the recommended intake established internationally. Concentrations of Cd and Pb were in the range of 10–321?µg?kg^?1?ww and 31–1200?µg?kg^?1?ww, respectively. The weekly dietary intake for Cd and Pb (4.02 and 20.4?µg?kg^?1 b.w, respectively) is lower than the FAO/WHO PTWI. Bread is the foodstuff that provided the highest rate of Pb and Cd (62 and 46% of the daily intake) to adults in Ismailia city.     

Acute and chronic toxic effect of lead (Pb) and zinc (Zn) on biomarker response in post larvae of Penaeus monodon (Fabricus, 1798)

Metal pollution produces damage to marine organisms at the cellular level possibly leading to ecological imbalance. The present investigation focused on the acute and chronic toxicity of lead (Pb) and zinc (Zn) by examining the effects of biomarker enzymes in post-larvae of Penaeus monodon (Tiger prawn). Antioxidant biomarker responses such as lipid peroxidation (LPO) and catalase (CAT) activity for Pb and Zn were determined following chronic exposure. Acute Lethal Concentration ₅₀ (LC₅₀) values observed in the study at 96?h for Pb and Zn at 5.77?±?0.32?mg?L^?1 and 3.02?±?0.82?mg?L^?1, respectively. The estimated No Observed Effect Concentration and Lowest Observed Effect Concentration values for Pb were 0.014 and 0.029?mg?L^?1 and that recorded for Zn was 0.011 and 0.022?mg?L^?1, respectively. Among the two metals studied, toxicity of Zn was found to be greater to P. monodon than Pb. The activities of antioxidant defense enzymes and total protein content differed significantly from control following exposure to both metals. Overall, the biomarker studies demonstrated that alterations in antioxidant enzymes and induction of LPO reflect the consequences of heavy metal exposure in P. monodon.     

Contamination and source assessment of metals,polychlorinated biphenyls,and polycyclic aromatic hydrocarbons in urban soils from Addis Ababa,Ethiopia

Urban areas in developing countries are facing vast environmental problems as a result of rapid urbanization and industrialization. Of major concern is the contamination of soils which are increasingly becoming sinks for environmental pollutants. However, to date only little is known about the pollution in the megalopolises of developing countries. The aim of this study was to assess the contamination and potential sources of metals, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in the urban environment of Addis Ababa, the capital of Ethiopia. The investigation revealed the presence of most of the analyzed pollutants in soil and sediment samples with total concentrations (dry wt) of PAHs ranging from 186 to 3150?µg?kg^?1, PCBs from 0.4 to 19?µg?kg^?1, Cu from 14 to 173?mg?kg^?1, Zn from 36 to 440?mg?kg^?1, Pb from 9 to 700?mg?kg^?1, and Ni from 16 to 72?mg?kg^?1. In addition, polyaromatic sulfur heterocycles, typical for oil and petrol residues, were detected in several soil samples. Source identification approaches revealed that Pb, Zn, and Cu are most likely derived from pyrolytic sources, with elevated values in samples related to waste combustion and traffic emissions. Ni is most probably of geogenic origin. For PCBs it is indicated that they are derived from a single source. However, correlations with technical PCB mixtures were inconsistent. PAHs originate from the combustion of biomass, vehicular exhausts, and petrogenic sources.     

Phenolic compounds in leaves of Salix species and hybrids growing under different soil conditions

The leaves of eight Salix species/hybrids were collected from two sites with different soil conditions including metal concentrations to investigate the concentration of Cu, Zn and Pb, phenolic profile and antioxidant scavenging activity. Cu, Zn and Pb, phenolic content and scavenging activity in leaves from the control area (lower concentration of metals in soil) (site C) were lower than in plants cultivated in site G (higher concentration of metals in soil). The content of Cu, Pb and Zn in leaves was in the range 9.21 (site G)–52.36 (site G), 0.41 (site C)?12.03 (site C) and 27.23 (site C)–214.44 (site G) mg?kg^?1, respectively. Total phenolic content ranged between 18.19 (site C) and 84.71 (site G) mg gallic acid equivalent per gram of dry matter. Total flavonoid content was between 7.98 (site C) and 54.48 (site G) mg catechin g^?1?d.m. The scavenging effect on 2,2-diphenyl-1-picrylhydrazyl˙ ranged between 33.6% (site C) and 56.3% (site G). Phenolic acids, myricetin and quercetin were quantified in leaves. The results show that phenolics are involved during adaptive mechanisms under elevated content of Cu, Pb and Zn in soil. Changes in the phenolic composition in leaves can be suggested as indicators of metal stress in Salix plants.     

Determination of metals in printed wiring boards of waste mobile phones

Metal contents of waste mobile phones represent a major environmental risk, especially considering the adoption of inappropriate management options in developing countries including open burning and disposal into surface water bodies. In this study the metal contents of mobile phone printed wiring board (PWB) samples were assessed. Sixty-two waste mobile phones of 15 brands were collected, dismantled, and their PWB samples were analyzed for Cu, Pb, Ag and Cd. The metal concentrations in the samples varied widely between and within brands. Among these metals, Cu and Pb were found to be at very high concentrations. The range (mean?±?SD) of Cu and Pb concentrations were 94.1–532?g?kg^?1 (250?±?92.3?g?kg^?1) and 7.0–46.2?g?kg^?1 (20.1?±?8.4?g?kg^?1), respectively. All Cu and Pb concentrations exceeded toxicity threshold limit concentration (TTLC) regulatory limits used in characterizing wastes as hazardous in the state of California, USA. The mean Cu and Pb concentrations exceeded the corresponding TTLC limits by factors of 100 and 20, respectively. The Ag and Cd concentrations were in the range 59.4–759?mg?kg^?1 (mean 227?±?104?mg?kg^?1) and ND – 15.6?mg?kg^?1 (2.1?±?3.3?mg?kg^?1), respectively.     

Lead and copper in the sclerotium of the mushroom Pleurotus tuber-regium (Osu): assessment of contribution to dietary intake in southeastern Nigeria

The concentrations of lead and copper in sclerotium of the mushroom Pleurotus tuber-regium widely consumed in Southeastern Nigeria were determined. The specimens purchased from different markets were mineralized with H₂SO₄ and H₂O₂ and analyzed using flame atomic absorption spectrophotometer. The concentrations of Pb ranged from 0.2?±?0.1?mg?kg^?1 to 0.8?±?0.5?mg?kg^?1 with approximately 91% of the results being below 1?mg?kg^?1. The concentrations of Cu ranged from 0.5?±?0.2?mg?kg^?1 to 1.2?±?0.6?mg?kg^?1 with 78% of the results below 1?mg?kg^?1. The results were compared with the literature and levels set by regulatory authorities, with the conclusion that the consumption of sclerotium does not pose a toxicological risk. The low Pb content of the studied products would contribute to only about 1% of the provisional tolerable weekly intake of Pb. The Cu contents would contribute to nutritional intake of the metal in the general population. It is recommended that the outer layers of the sclerotia be properly scrapped before use to reduce metal contamination from exogenous sources.     

Heavy metal concentration in soil and woody plants in a quarry

This study determined the concentration of three heavy metals zinc (Zn), lead (Pb), and cadmium (Cd) in soil and in a woody plant species, Milicia excelsa, at Ishiagu quarry, Nigeria. The highest soil concentrations of Zn, Pb, and Cd in soil were obtained at 1?m from the quarry site. In M. excelsa, the highest concentrations of Zn, Pb, and Cd were 3.12–9.1, 3.9–6.01, and 0.51–1.12?mg?kg^?1, respectively. There were significant positive correlations between Cd and Zn (r?=?0.963) and Cd and Pb (r?=?0.974) in plants as well as between Cd and Pb (r?=?9.84) in soil. The level of Cd in soil reflected significant pollution compared to average global concentrations in soils.     

Protective action of zinc against lead poisoning in tilapia Oreochromis niloticus

The accumulation of lead (Pb) in tilapias Oreochromis niloticus, acclimatized in cement tanks, and fed once a day with pellets of commercial food with lead nitrate, was investigated by square wave anodic stripping voltammetry (SWV). The head (including head bones, proteins, and brain) was the main target of lead uptake by tilapias, with a small amount in muscle tissue. A high concentration of Pb was found in feces which indicated low absorption by the organism when fed with high Pb concentration. The protective effects of zinc (Zn) against the Pb poisoning, the accumulation of Pb in the heads of the fishes of 107.8?±?3.1?mg?kg^?1 and in the viscera of 57.1?±?2.9?mg?kg^?1 with consequent decrease of calcium (Ca) concentration, were observed. In spite of the experimental time of 16 months and higher Pb concentration in the dietary food of 320?mg?kg^?1, no death of tilapias was observed due to the protective action of Zn.     

Soil pollution by trace metals derived from animal feed and manure in the Bursa region of Turkey

The Bursa region of Turkey has important agricultural production areas. Animal producers use agricultural fields in this region for disposal of manure. Therefore, in this study the concentrations of the seven trace metals Zn, Mn, Cu, Ni, Cr, Pb, and Cd in 324 animal feed and manure samples from three dairy cattle, three laying hens farms, and three broiler farms have been determined. The average concentrations in dairy cattle manure were 130 (Zn), 150 (Mn), 4.2 (Cu), 6.8 (Ni), 44 (Cr), 0.8 (Pb), and 0.09 (Cd) mg kg^?1 dry weight; for laying hens manure 240 (Zn), 190 (Mn), 0.63 (Cu), 3.8 (Ni), 30 (Cr), 0.55 (Pb), and 0.12 (Cd) mg kg^?1 dry weight; and for broiler manure 240 (Zn), 280 (Mn), 1.4 (Cu), 3.8 (Ni), 35 (Cr), 3.4 (Pb), and 0.16 (Cd) mg kg^?1 dry weight. The calculated trace metal loading rate indicated that manure application might pose a potential risk to agricultural fields according to the current soil protection regulations of Turkey.     

Stabilization of metals in acidic mine spoil with amendments and red fescue (<Emphasis Type="Italic">Festuca rubra</Emphasis> L.) growth

Stabilization of metals with amendments and red fescue (Festuca rubra, cv. Keszthelyi 2) growth was studied on an acidic and phytotoxic mine spoil (pH_KCl 3.20–3.26; Cd 7.1 mg kg^?1, Cu 120 mg kg^?1, Pb 2154 mg kg^?1 and Zn 605 mg kg^?1) from Gyöngyösoroszi, Hungary in a pot experiment. Raising the pH above 5.0 by lime (CaCO₃), and supplementing with 40 mg kg^?1nitrogen (NH₄NO₃) made this material suitable for plant growth. All cultures were limed with 0.5% (m/m) CaCO₃ (treatment 1), which was combined with 5% (m/m) municipal sewage sludge compost (treatment 2), 5% (m/m) peat (treatment 3), 7.5% (m/m) natural zeolite (clinoptilolite) (treatment 4), and 0.5 (m/m) KH₂PO₄ (treatment 5). Treatments 1–5 were combined with each other (treatment 6). After 60 days of red fescue growth, pH of the limed mine spoil decreased in all cultures units. Application of peat caused the highest pH decrease (1.15), while decrease of pH was less than 0.23 in treatments 2, 5 or 6. Application of lime significantly reduced concentrations of metals in the ‘plant available’ fraction of mine spoil compared to non-limed mine spoil. Amendments added to limed mine spoil changed variously the ratio of Cd, Cu, Pb and Zn in exchangeable or ‘plant available’ fractions, differently influencing the phytoavailability of these metals. Most of the metals were captured in the roots of test plants. Treatment 2 caused the appearance of less Cd in shoots (<0.1 μg g^?1) or roots (3.11 μg g^?1), while treatment 5 resulted in the highest Cd concentration (2.13 μg g^?1) in shoots. Treatments did not influence significantly the Cu accumulation in shoots. The Pb accumulation of roots (44.7 μg g^?1) was most effectively inhibited by combined treatment, while the highest value (136 μg g^?1) was found in the culture treated with potassium phosphate. Pb concentration in shoots was below the detection limit, except for treatments 5 and 6. Peat application resulted in higher Zn concentration (448 μg g^?1) in shoots than other amendments, where these values were around 100 μg g^?1. All amendments influenced positively the dry matter yield of red fescue grown in limed mine spoil, however the application of 0.5 phosphate was less favourable. Liming, application of amendments and growth of red fescue can stabilize metals in acidic and phytotoxic mine spoil, and by phytostabilization they can reduce the risk of metal contamination of the food chain.     

Metals contamination in the foraging area of Milky Stork: evidence of anthropogenic inputs in the aquatic environment of Kuala Gula,Malaysia

The rapid decline of the wild Milky Stork population in Malaysia has led to the reintroduction of the captive bred species in Kuala Gula, Perak. The area is known as an important migratory stopover and sanctuary for both visitors and resident birds. Although Kuala Gula and its adjacent areas are regarded as pristine and unpolluted, recent study suggested that accumulation of certain pollutants is occurring in the aquatic environment of the area. Surface sediment samples from five foraging areas considered important to the reintroduced Milky Storks have been analyzed for metals contamination. The results show that elevations of Cu, Zn, and Pb ranging from 9.7 to 57 mg kg^?1, 71 to 120 mg kg^?1, and 28 to 47 mg kg^?1 have occurred, except for Cd (0.9–1.7 mg kg^?1). The accumulation of these metals is site-specific which reflects continuous anthropogenic inputs into the aquatic environment of Kuala Gula. In addition, metal levels in some areas have exceeded the effects range low values, and thus urgent action is needed to ensure good practice and sustainable management of Kuala Gula by responsible parties.     

Purification of contaminated paddy fields by clean water irrigation over two decades

Paddy fields near a mining site in north part of Guangdong Province, PR China, were severely contaminated by heavy metals as a result of wastewater irrigation from the tailing pond. The following clean water irrigation for 2 decades produced marked rinsing effect, especially on Pb and Zn. Paddy fields continuously irrigated with wastewater ever since mining started (50 years) had 1,050.0 mg kg^?1 of Pb and 810.3 mg kg^?1 of Zn for upper 20 cm soil, in comparison with 215.9 mg kg^?1 of Pb and 525.4 mg kg^?1 of Zn, respectively, with clean water irrigation for 20 years. Rinsing effect mainly occurred to a depth of upper 40 cm, of which the soil contained highest metals. Copper and Cd in the farmlands were also reduced due to clean water irrigation. Higher availability of Pb might partly account for more Pb transferred from the tailing pond to the farmland and also more Pb removal from the farmland as a result of clean water irrigation. Neither rice in the paddy field nor dense weeds in the uncultivated field largely took up the metals. However, they might contribute to activate metals differently, leading to a different purification extent. Rotation of rice and weed reduced metal retention in the farmland soil, in comparison with sole rice growth. Harvesting of rice grain (and partially rice stalk) only contributed small fraction of total amount of removed metal. In summary, heavy metal in paddy field resulted from irrigation of mining wastewater could be largely removed by clean water irrigation for sufficient time.     

Electro-remediation of tailings from a multi-metal sulphide mine: comparing removal efficiencies of Pb,Zn, Cu and Cd

Sulphidic mine tailings characterised by high concentrations of heavy metals (Pb 3532?±?97?mg/kg, Zn 8450?±?154?mg/kg, Cu 239?±?18?mg/kg and Cd 14.1?±?0.3?mg/kg) and abundant carbonate (17%) were subjected to eight lab-scale electrodialytic remediation (EDR) experiments to investigate the influence of current density, treatment time and particle size on removal efficiency. Pb and Cu removal improved when increasing current density, while Zn and Cd removal did not. In contrast Zn and Cd removal improved by grinding the tailings, while Pb and Cu removal did not. At the highest current density (1.2?mA/cm²), 94%, 75%, 71% and 67% removal of Pb, Zn, Cu and Cd could be achieved, respectively, on grinded tailings in 28 days. Sequential chemical extraction made before and after EDR revealed larger oxidisable fractions of Zn, Cu and Cd, representing large fractions of sulphides, which was likely to be the main barrier to be removed as efficiently as Pb. This was in accordance with acid/base extraction tests in which Pb showed high solubility at both high and low pH (up to 65% and 86% of extraction, respectively), while considerable extraction of Zn (55%) happened only at low pH; and very limited extraction (<20%) of Cu and Cd occurred at any pH.     

Assessment of metal contamination in soil banks of the Rhumel wadi (Northeast Algeria)

Levels of six trace metals were assessed in bank soils of the Rhumel wadi (Northeast Algeria) and their association with soil properties was investigated. Samples were collected at 10 sites. The soils are neutral to moderately alkaline, have high contents of carbonate, and are low in organic carbon and clay. Mean metal concentrations are 1.1 (Cd), 63 (Cr), 20 (Cu), 26 (Ni), 31 (Pb), and 98 (Zn) mg kg^?1. The Cd, Cu, Pb, and Zn contents in soil from sites closest to Constantine City were higher than in uncontaminated soils worldwide, indicating accumulation due to human activities (residential, industrial, and agricultural). Statistical analyses (correlation and principal component analysis) demonstrated that Cd, Pb, and Zn are of anthropogenic origin in the urban areas, whereas Cr and Cu enrichment in some situations is caused by industrial activities, while Ni was geogenic.     

Assessment of As and Heavy Metal Contamination in the Vicinity of Duckum Au-Ag Mine, Korea

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.