Heavy Metal Removal Capacity Research Articles

Adsorption and chemical precipitation of lead and zinc from contaminated solutions in porous rocks: Possible application in environmental protection

Natural porous rocks, like limestone and rhyolite tuff are able to reduce heavy metal pollution by adsorbing or precipitating them from heavy metal containing solutions due to the favourable physical and chemical properties of these rocks.In our experiment, two porous rocks, a porous limestone and rhyolite tuff were used. Petrophysical parameters namely apparent density, real density, capillary water absorption, ultrasonic pulse velocity, total porosity and open porosity of the two porous rocks were determined in water-saturated and dried conditions.Powdered rock samples and cylindrical specimens were placed in lead-nitrate and zinc-sulphate solutions (initial concentration: 1000 ppm) and the amount of lead (II) and zinc (II) ions were identified by titration (chelatometry) of the residual solution. According to the experiments, powdered rocks and rock specimens of limestone and rhyolite tuff reduced the lead (II) and zinc (II) ion concentrations in aqueous solution. The results were cross-checked by ICP-MS. Heavy metal removal capacity was relatively high, 92–99% in each case. The treated powdered rocks and rock specimens were also studied by scanning electron microscope (SEM-EDS) and new heavy metal precipitates were identified.According to the tests result, it could be confirmed that these types of lithologies are capable of removing heavy metals and can be used in environmental protection technologies in a form of permeable reactive barrier.

Evaluation of Heavy Metal Removal Capacity of Bioretention Systems

Bioretention is one of the most common low-impact development (LID) types but there is lack of knowledge in the capacity and local behavior of bioretentions. In this study, laboratory-scale experiments are conducted in order to investigate the heavy metal removal capacity of bioretentions. Batch sorption experiments were first performed to determine the sorption parameters and retardation factor of copper (Cu), lead (Pb), and zinc (Zn) on various bioretention media, namely mulch, turf, vegetative soil, sand, and gravel. Reaction kinetics of Cu, Pb, and Zn were determined in order to assess the sorption equilibrium time of these metals for the five different bioretention media. The results of the batch tests show that turf has the highest sorption capacity followed by mulch and vegetative soil. For the range of concentrations considered in this study, linear sorption isotherm was found to best represent the metal sorption for all bioretention media. Metal removal percentages were highest for Pb and lowest for Zn. The time required to reach equilibrium ranged from 1 to 6 h depending on the type of bioretention media and metal. In addition to batch sorption experiments, column sorption experiments were also conducted in order to investigate effects of soil textures and organic content on removal of heavy metal in bioretention columns. For this purpose, four bioretention columns with different vegetative soil, turf, and sand ratios were prepared. The column tests were conducted for a period of 127 days under continuous boundary source, i.e., constant flow rate is supplied to each column with a concentration of 5 mg/L for each metal. Results show that different local soil types in bioretention design affect removal of heavy metal concentration considerably. Breakthrough analysis indicates that the removal of Zn reaches almost zero in about 127 days, while Cu and Pb are almost fully retained in all columns until the end of the experiment.

GWP (Global Warming Potential)를 고려한 가시박 바이오차르의 토양 납 제거 효과 분석

Biochar, a by-product from pyrolysis of biomass, is a promising option to mitigate climate change by increasing soil carbon sequestration. This material is also considered to have potential to remediate a soil with heavy metal pollution by increasing the soil's adsorptive capacity. This study conducted the assessment of two biochars considering the climate change mitigation potential and heavy metal removal capacity at the same time. Two kinds of biochars (BC_Ch, TW_Ch) were prepared by pyrolyzing the biomass of burcucumber (BC_Bm) and tea waste (TW_Bm). The soils polluted with Pb were mixed with biochars or biomass and incubated for 60 d. During the incubation, , , and were regularly measured and the soil before and after incubation was analyzed for chemical and biological parameters including the acetate extractable Pb. The results showed that only the BC_Ch treatment significantly reduced the amount of Pb after 60 d incubation. During the incubation, the and emissions from the BC_Ch and TW_Ch were decreased by 24% and 34% compared to the BC_Bm and TW_Bm, respectively. The emissions were not significantly affected by biochar treatments. We calculated the GWP considering the production of amendment materials, application to the soils, removal of Pb, and soil carbon storage. The BC_Ch treatment had the most negative value because it had the higher Pb adsorption and soil carbon sequestration. Our results imply that if we apply biochar made from burcucumber, we could expect the pollution reduction and climate change mitigation at the same time.

EPS production and bioremoval of heavy metals by mixed and pure bacterial cultures isolated from Ankara Stream.

This study is focused on isolation of Ni(II), Cu(II) and Cr(VI) resistant bacteria to assess their exopolysaccharide (EPS) production and related bioremoval capacities. Mixed cultures had higher heavy metal removal capacity in media with molasses (MAS) than the control cultures lacking this carbon (AS) containing 50 mg/l of heavy metal. The yields were 32%, 75.7%, and 51.1% in MAS, while the corresponding values were 29%, 55.1%, and 34.5% in AS, respectively. Purification of the strains 1, 5 and 6 present in the mixed cultures decreased the bioremoval capacities of the mixed culture samples, although these strains produced higher EPS amounts in MAS agar. Strain 5 had the highest Cu(II) (69.1%) and Cr(VI) (43.1%) removal rates at 25 mg/l initial concentration of each pollutant with EPS amounts of 0.74 g/l and 1.05 g/l, respectively. This strain was identified as Stenotrophomonas maltophilia. The presented data show that especially mixed and also pure cultures of bacterial strains isolated from Ankara Stream could be assessed as potential bioremoval agents in the treatment of Cu(II) or Cr(VI) containing wastewaters.

Phytoremediation capacity of aquatic plants is associated with the degree of phytochelatin polymerization

Phytochelatins (PCs) play important role in phytoremediation as heavy metal binding peptides. In the present study, the association between heavy metal removal capacity and phytochelatin synthesis was compared through the examination of three aquatic plants: Elodea canadensis, Salvinia natans and Lemna minor. In case of a Cd treatment, or a Cd treatment combined with Cu and Zn, the highest removal capacity was observed in L. minor. At the same time, E. canadensis showed the lowest removal capacity except for Zn. The heavy metal-induced (Cu+Zn+Cd) oxidative stress generated the highest ascorbate level in L. minor. Cd in itself or combined with the other two metals induced a 10–15-fold increase in the amount of ɣ-glutamylcysteine in L. minor while no or smaller changes were observed in the other two species. Correspondingly, the total PC content was 6–8-fold greater in L. minor. In addition, PCs with higher degree of polymerization were only observed in L. minor (PC4, PC6 and PC7) while PC2 and PC3 occurred in E. canadensis and S. natans only. The correlation analysis indicated that the higher phytoremediation capacity of L. minor was associated with the synthesis of PCs and their higher degree of polymerization.

Zeolite development from fly ash and utilization in lignite mine-water treatment

Fly ash from two lignite-fed power stations in Greece (Megalopolis and Meliti) has been utilized to synthesize zeolitic materials with upgraded adsorption capacity. Two different siliceous fly ash samples were subjected to hydrothermal treatment at fixed solid/liquid ratio and constant temperature. The zeolitic products have been characterized for their microstructure, chemical, and mineralogical composition by means of SEM, AAS, and XRD, respectively. The primary zeolitic crystals identified were phillipsite and thomsonite, in Megalopolis and Meliti fly ash, respectively. In light of their prospective utilization as liquid-phase sorbents, the specific surface area and porosity of materials were also determined, by means of N2-porosimetry. The zeolitic samples were tested for their actual heavy metal-removal capacity by water sampled from active lignite mines in Northern Greece. Artificial aquatic samples with known concentration of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) were also tested, showing that the synthetic zeolitic materials are good to uptake a wide variety of potential pollutants with up to 100% efficiency. The efficiency of the synthetic zeolitic materials was comparatively assessed, showing that the more intense the presence of phillipsite in the synthetic materials, the greater the uptake rates for certain groups of trace elements.

HEAVY METAL BALANCE IN A HUNGARIAN MUNICIPAL SEWAGE TREATMENT PLANT

The present study was undertaken to experimentally evaluate the heavy metal (HM) removal capacity of a municipal wastewater treatment plant (WWTP) as a kind of mass balance. The aim of the work was to find a water or sludge stream in the WWTP that could be treated separately for heavy metal removal to maximize the same efficiency of the whole treatment technology. Although literature says that the HM content of sewage accumulates in the sewage sludge, the experimental results showed no compliance with it. The results obtained demonstrated that 85-95% of the inlet metal content was discharged into the recipient and only 5-15% was retained in the digested sludge in the studied plant. A few percentage of the metal content of the influent could only be measured in the primary and secondary sludge. Otherwise the metal concentration of these sludge streams was very similar. The reject water had an inconsiderable metal recycle in the technology, not more than 2-3% of the influent load. Approximately 2-10% of the HM inlet was removed by the sand trap. The separate HM removal from the sludge streams seems to be inadequate since most of the HM load of the plant was finally discharged with the treated effluent to the receiver. This is the reason why the prevention of these contaminants’ getting into the sewage is the most important task.

Organic free low temperature direct synthesis of hierarchical protonated layered titanates/anatase TiO2 hollow spheres and their task-specific applications

Layered protonated titanates and corresponding anatase TiO2 shapes, specifically the hollow spheres, are the most important functional materials and have attracted much attention because of their superior performance. Here, a facile organic substrate (both as solvent or surfactant) free, low temperature aqueous solution based chemical protocol for the direct synthesis of 3D arranged hierarchical hollow spheres of protonated layered dititanate (H2Ti2O5·H2O), is proposed. The spheres had a high surface area (as high as 334 m2 g−1), and were prepared through hydrothermal treatment of freshly prepared peroxo titanium carbonate complex in the presence of ammonium hydroxide. Ammonium hydroxide is crucial in the formation of spherical arrangement of titanate sheets and the size of the spheres is tunable by changing the amount of ammonium hydroxide. The titanate spheres can easily be converted to pure anatase TiO2 with identical morphology on subsequent calcination. The synthesized titanate spheres showed very high removal capacity for toxic heavy metals like Pb2+ and methylene blue from aqueous solution. Corresponding anatase TiO2 spheres manifested as a brilliant anode material for lithium ion batteries with excellent cyclability. TiO2 spheres also showed good photocatalytic activity.

Biofilm establishment and heavy metal removal capacity of an indigenous mining algal-microbial consortium in a photo-rotating biological contactor

An indigenous mining algal-microbial consortium was immobilised within a laboratory-scale photo-rotating biological contactor (PRBC) that was used to investigate the potential for heavy metal removal from acid mine drainage (AMD). The microbial consortium, dominated by Ulothrix sp., was collected from the AMD at the Sar Cheshmeh copper mine in Iran. This paper discusses the parameters required to establish an algal-microbial biofilm used for heavy metal removal, including nutrient requirements and rotational speed. The PRBC was tested using synthesised AMD with the multi-ion and acidic composition of wastewater (containing 18 elements, and with a pH of 3.5±0.5), from which the microbial consortium was collected. The biofilm was successfully developed on the PRBC's disc consortium over 60days of batch-mode operation. The PRBC was then run continuously with a 24h hydraulic residence time (HRT) over a ten-week period. Water analysis, performed on a weekly basis, demonstrated the ability of the algal-microbial biofilm to remove 20-50% of the various metals in the order Cu>Ni>Mn>Zn>Sb>Se>Co>Al. These results clearly indicate the significant potential for indigenous AMD microorganisms to be exploited within a PRBC for AMD treatment.

Characterisation of adsorbents prepared by pyrolysis of sludge and sludge/disposal filter cake mix

Copper and zinc removal from water (pH = 5.0) using adsorbents produced from slow and fast pyrolysis of industrial sludge and industrial sludge mixed with a disposal filter cake (FC), post treated with HCl, is investigated in comparison with a commercial adsorbent F400. The results show that a pseudo-second order kinetics model is followed. The Langmuir–Freundlich isotherm model is found to fit the data best. The capacity for heavy metal removal of studied adsorbents is generally better than that of commercial F400. The dominant heavy metal removal mechanism is cation exchange. Higher heavy metal removal capacity is associated with fast pyrolysis adsorbents and sludge/FC derived adsorbents, due to enhanced cation exchange. Improvement of Zn2+ removal via 1 N HCl post-treatment is only effective when exchangeable cations of the adsorbent are substituted with H+ ions, which boost the cation exchange capacity. Increase of temperature also enhances metal removal capacity. Fast pyrolysis sludge-based adsorbents can be reused after several adsorption–desorption cycles.

Self-assembled flower-like TiO2 on exfoliated graphite oxide for heavy metal removal

We describe that a hydrothermal preparation of flower-like TiO2-graphene oxide (GO-TiO2) hybrid by stirring a titanium oxide precursor in isopropyl alcohol with GO colloidal solution. The GO-TiO2 hybrid was applied for the removal of heavy metal ions from water. The oxygenated functional groups of exfoliated graphite oxide showed a high removal capacity of heavy metals. The flower-like TiO2 on GO structure significantly improved the removal efficiency of heavy metals. For example, the GO-TiO2 hybrid adsorption capacities of heavy metal ions, after 6h and 12h of hydrothermal treatment at 100°C, were respectively 44.8±3.4 and 88.9±3.3mg/g for removing Zn2+, 65.1±4.4 and 72.8±1.6mg/g for removing Cd2+, and 45.0±3.8 and 65.6±2.7mg/g for removing Pb2+ at pH 5.6. In contrast, colloidal GO under identical condition showed removal capacities of 30.1±2.5 (Zn2+), 14.9±1.5 (Cd2+), and 35.6±1.3mg/g (Pb2+). TiO2 blossoms markedly formed upon GO as the hydrothermal treatment time at 100°C increased from 6h to 12h. Longer treatment times resulted in an increase in the surface area of GO-TiO2 hybrid and thus its removal capacity of heavy metal increased.

키토산/폴리감마글루탐산 나노입자의 제조 및 중금속 제거에의 응용

키토산은 천연고분자 물질로 다양한 물리화학적(다중양이온, 반응성 수산화기와 아미노기 그룹), 생물학적(생리활성, 생체적합성, 생분해성) 특성을 가지고 있다. 본 연구에서는 겔형성제로 폴리감마글루탐산을 이용하여 키토산 나노입자를 제조하였다. 나노입자는 폴리감마글루탐산의 카르복실기(<TEX>$-COO^-$</TEX>)와 키토산의 아미노기(<TEX>$-NH_3^+$</TEX>)사이의 이온 상호작용에 의해 형성되었다. 키토산(0.1~1 g)을 100 ml 아세트산 용액(1% v/v)에 첨가한 후 상온에서 충분히 용해되도록 하룻밤 동안 교반하였다. 폴리감마글루탐산(0.1 g)은 상온에서 90 ml 증류수에 용해시켰다. 교반되고 있는 폴리감마글루탐산 용액에 키토산 용액을 주사바늘을 통해 상온에서 적가하였다. 입자의 평균 크기는 80~300 nm 범위에서 형성되었다. 키토산/폴리감마글루탐산 나노입자는 중금속 이온들(<TEX>$Cd^{2+}$</TEX>, <TEX>$Pb^{2+}$</TEX>, <TEX>$Zn^{2+}$</TEX>, <TEX>$Cu^{2+}$</TEX>, <TEX>$Ni^{2+}$</TEX>)의 제거를 위해 콜로이드 상태의 흡착 물질로 사용되었다. 나노입자의 중금속 제거 능력은 <TEX>$Cu^{2+}$</TEX> > <TEX>$Pb^{2+}$</TEX> > <TEX>$Cd^{2+}$</TEX> > <TEX>$Ni^{2+}$</TEX> > <TEX>$Zn^{2+}$</TEX>의 결과를 보였다. Chitosan is a natural polymer that has many physicochemical(polycationic, reactive OH and <TEX>$NH_2$</TEX> groups) and biological(bioactive, biocompatible, and biodegradable) properties. In this study, chitosan nanoparticles were prepared using poly-<TEX>${\gamma}$</TEX>-glutamic acid(<TEX>${\gamma}$</TEX>-PGA) as gelling agent. Nanoparticles were formed by ionic interaction between carboxylic groups in <TEX>${\gamma}$</TEX>-PGA and amino groups in chitosan. Chitosan(0.1~1 g) was dissolved in 100 ml of acetic acid (1% v/v) at room temperature and stirred overnight to ensure a complete solubility. An amount of 0.1 g of <TEX>${\gamma}$</TEX>-PGA was dissolved in 90 ml of distilled water at room temperature. Chitosan solution was dropped through needle into beaker containing <TEX>${\gamma}$</TEX>-PGA solution under gentle stirring at room temperature. The average particle sizes were in the range of 80~300 nm. The prepared chitosan/<TEX>${\gamma}$</TEX>-PGA nanoparticles were used to examine their removal of several heavy metal ions(<TEX>$Cd^{2+}$</TEX>, <TEX>$Pb^{2+}$</TEX>, <TEX>$Zn^{2+}$</TEX>, <TEX>$Cu^{2+}$</TEX>, and <TEX>$Ni^{2+}$</TEX>) as adsorbents in aqueous solution. The heavy metal removal capacity of the nanoparticles was in the order of <TEX>$Cu^{2+}$</TEX> > <TEX>$Pb^{2+}$</TEX> > <TEX>$Cd^{2+}$</TEX> > <TEX>$Ni^{2+}$</TEX> > <TEX>$Zn^{2+}$</TEX>.

Nutrient Removal Using Bauxsol&lt;sup&gt;TM&lt;/sup&gt; for Treated Wastewater Reuse

Urban areas consume huge amounts of water and produce much wastewater, which deteriorate the aquatic environment and exhaust the country’s freshwater resources. Water reuse from sewage and wastewater is recognized as a good option for securing water. There are several kinds of processes for improving the water quality. Nutrient removal is very important for water reuse, especially in water supply for outdoor use, to prevent water quality deterioration via eutrophication. Moreover, low cost and easy maintenance should be considered for nutrient removal. In this study, red mud and BauxsolTM, a mixed mineral powder made of physicochemically modified red mud residue generated by the Bayer process for alumina refineries, was used for the removal of nitrate and heavy metals in artificial solution, and of phosphate in final effluent, from a sewage treatment plant in Dae-gu, Republic of Korea. Nitrate removal by red mud showed little efficiency while heavy metal removal showed high efficiency. The concentrations of the total phosphate in the effluent and treated water were 1.51 and 0.14 mg/L, respectively, which represent about 90.7% removal. Before and after the treatment, the pH was maintained at a neutral range of 6.5-7.2. BauxsolTM also showed a high heavy metal removal capacity. Therefore, BauxsolTM in powder and pellet form can be applied individually or mixed with soil to improve water quality for water reuse.

A Study of Environmental factor on the Removal capacity of Heavy Metals by Exophiala sp. LH2.

A Study of Environmental factor on the Removal capacity of Heavy Metals by Exophiala sp. LH2.

Biofiltration of secondary treated municipal wastewater in a tropical city

Aquatic plants are quite effective in separating metals from polluted waters. A promising method using aquatic plants to sorb metals from secondary treated municipal wastewater is examined in the study. Traditional sewage treatment plants with secondary treatment facilities are not able to remove heavy metals efficiently from the wastewater. In Varanasi, the sewage is mixed with industrial effluents containing high concentrations of heavy metals such as Cr (1.2), Cd (0.09), Cu (0.11), Zn (0.92), Fe (1.8) and Ni (0.07) mg L −1. Eichhornia crassipes, Pistia stratiotes, Lemna minor, Azolla pinnata, and Spirodela polyrhiza were tested for their heavy metal removal capacity from the secondary treated municipal wastewater. Accumulation of heavy metal was higher in roots as compared to leaves. The preferential sequence of percent removal by the selected aquatic macrophytes was Fe > Cr > Cu > Cd > Zn > Ni. Statistical analysis revealed a positive and significant correlation between percent removal of heavy metals from the wastewater and increase in the plant tissues.

Removal of heavy metals using waste eggshell

The removal capacity of toxic heavy metals by the reused eggshell was studied. As a pretreatment process for the preparation of reused material from waste eggshell, calcination was performed in the furnace at 800°C for 2 h after crushing the dried waste eggshell. Calcination behavior, qualitative and quantitative elemental information, mineral type and surface characteristics before and after calcination of eggshell were examined by thermal gravimetric analysis (TGA), X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. After calcination, the major inorganic composition was identified as Ca (lime, 99.63%) and K, P and Sr were identified as minor components. When calcined eggshell was applied in the treatment of synthetic wastewater containing heavy metals, a complete removal of Cd as well as above 99% removal of Cr was observed after 10 min. Although the natural eggshell had some removal capacity of Cd and Cr, a complete removal was not accomplished even after 60 min due to quite slower removal rate. However, in contrast to Cd and Cr, an efficient removal of Pb was observed with the natural eggshell rather than the calcined eggshell. From the application of the calcined eggshell in the treatment of real electroplating wastewater, the calcined eggshell showed a promising removal capacity of heavy metal ions as well as had a good neutralization capacity in the treatment of strong acidic wastewater.

Lead biosorption and desorption by intact and pretreated spirulina maxima biomass

In order to search for locally available and untried biomaterials in China with high removal capacity of heavy metals from wastewater, the feasibility of Spirulina maxima as biosorbent for lead removal and recovery from aqueous solution was investigated. The lead biosorption was studied by using intact biomass and pretreated biomass of S. maxima. The effects of operational conditions (e.g. pH, contact time, biomass concentration etc.) on lead biosorption were investigated. The biosorption was solution pH dependent and the maximum adsorption was obtained at a solution pH of about 5.5. The adsorption equilibrium was reached in 60 min. The biosorption followed the Freundlich isotherm model. The maximum removal ratios of lead were about 84% in intact biomass and 92% in pretreated biomass. The lead adsorbed could be desorbed effectively by 0.1 M nitric acid, EDTA and hydrochloric acid. The results in this study indicated that pretreated biomass of S. maxima was a promising candidate for removing lead from wastewater.

고온.고압 처리한 키토산을 이용한 수중의 납 제거에 관한 연구

In order to know the effect of atuoclaving on the heavy metal removal using chitosan, lead removal capacities and removal rates by various chitosans in aqueous solution were compared according to the various autoclaving time. The lead removal efficiencies and removal rates by the autoclaved chitosan were found to be on the order of 15 min(98％) ＞ 10 min(95％) ＞ 30 min(83％) ＞ 5 min(53％) ＞ 60 min(47％) ＞ 0 min(22％) chitosan. The molecular weight of chitosan was decreased by the increase of autoclaving time. Therefore, the heavy metal removal capacity was not well correlated to the molecular weight. Langmuir isotherm was well fitted to experimental results of equilibrium adsorption on chitosan. In order to examine the process of lead removal by the autoclaved chitosan, TEMs, SEMs and FT-IR analyses were used. The surface of autoclaved chitosan was much more porous and the lead removal was mainly occurred on the surface of chitosan. The structure of autoclaved chitosan was same as that of controlled chitosan.

Biosorption of cadmium (II) and copper (II) by pretreated biomass of marine alga Gracilaria fisheri

The cadmium (II) and copper (n) adsorption properties of chemically pretreated biomass of red marine alga Gracilaria fisheri were investigated. Batch equilibrium experiments showed that the maximum adsorption capacity values of the pretreated biomass for cadmium and copper were 0.63 and 0.72 mmol g−1, respectively. The equilibrium data fitted well to the Langmuir isotherm model. The adsorption capacity increased as pH increased and reached a plateau at pH 4.O. The cadmium and copper uptake rates were rapid with 90% of the biosorption completed within 30 minutes. The presence of light metal ions (Na+, K+, Mg1+ and Ca2+) in solution had an insignificant effect on cadmium and copper sorption capacity. These findings indicate a positive potential for the biosorbent development with effective heavy metal removal capacity in the presence of light metal ions in waste streams by using the biomass of plentifully available red marine algae.

Distribution of Heavy Metals in Soils of Shihwa Tidal Freshwater Marshes

Shihwa tidal freshwater marsh was constructed recently to treat pollutants entering Shihwa lake. In this study, we examined the spatial and temporal patterns of heavy metal accumulation in soils of Shihwa marsh and sought correlations between several soil variables (pH, electrical conductivity, organic matter, and acid ammonium oxalate-extractable Fe and Al contents) and the heavy metal concentration of soils. Surface soil samples (0∼20 cm) were collected in June 2000, November 2000, and July 2001, and were analyzed for heavy metals (Zn, Cd, Pb, Cu, Cr, As, and Hg) and soil chemical properties. The neutral pH and water-saturated conditions of Shihwa marsh appeared to favor immobilization of heavy metal through adsorption onto soils. The concentrations of heavy metal (especially Zn, Cu, and Cr) in soils of Shihwa marsh increased along the sampling occasions, suggesting that soils of Shihwa marsh serve as a sink of heavy metal. Among the sub-marshes, metal concentrations were highest in Banweol high marshes and lowest in Samhwa marshes. The temporal and spatial variations in the heavy metal concentrations of soils were correlated positively with organic matter and oxalate extractable Fe and Al contents, but negatively with electrical conductivity. These results suggest that organic matter and hydrous oxide of Fe/Al may playa key role in removing heavy metals in soils of Shihwa marsh, and that heavy metal removing capacity would increase with desalinization. However, the removal patterns of heavy metal by reeds warrant further studies to evaluate the total removal capacity of heavy metals by Shihwa marsh.