Review of remediation technologies for sediments contaminated by heavy metals

Journal of Soils and Sediments - Contamination of sediments with heavy metals (HMs) is a worldwide environmental issue, due to the negative ecological effects of HMs. Sediments are an important...     

云南滇池沉积物中重金属的形态分布特征

Fractionation of heavy metals in sediments can help in understanding potential hazards of heavy metals. The present study analyzed total concentrations and fractions of selected heavy metals （Cd, Cr, Cu, Pb, and Zn） in surface sediments from Dianchi Lake, Yunnan Province, China, as well as factors that may affect distributions of the various heavy metal fractions. Total concentrations of the heavy metals decreased in the order Zn 〉 Cu 〉 Pb 〉 Cr 〉 Cd. These heavy metals, except Cr, were much higher than their background levels, indicating that Dianchi Lake was polluted by Cd, Zn, Pb, and Cu. Cadmium occurred mainly as the non-residual fraction （sum of the HOAc-soluble, reducible, and oxidizable fractions） （97.6%）, and Zn （55.7%） was also predominantly found in the non-residual fraction. In contrast, most of the Cr （88.5%）, Pb （81.8%）, and Cu （59.2%） occurred in the residual fraction. Correlation analysis showed that total heavy metal concentrations, organic matter and reducible Fe were the main factors affecting the distributions of the various heavy metal fractions. In the Walhai section of Dianchi Lake （comprising 97% of the lake area）, the concentrations of Cd, Zn, Pb, and Cu in the non-residual fraction were significantly lower （P ≤ 0.01 or 0.05） than those of the Caohal section （3% of the lake area）. This indicated that potential heavy metal hazards in the Caohai section were greater than the Waihai section.     

Pond sediments as historical record of heavy metals fallout

Well preserved pond sediments were dated as a function of depth by the Pb-210 geochronological method for the past 100 yr. The results have been checked with Cs-137 analysis for the last 30 yr. Mineralogical composition is very constant along the sediment core indicating mechanical erosion of local outcrops as bulk sediment origin. The contents of Al, Cu, Pb, Zn, Cd, and As have been determined and enrichment factors normalized to A1 value were calculated. Copper is mainly of natural origin, and As is influenced by local agricultural use. The anthropogenic source of Pb, Zn, and Cd is clearly provided by atmospheric fallout which is supported by comparison with atmospheric fluxes for wet and dry deposition.     

Transport and distribution of heavy metals in Cauvery river

Heavy metal transport in Cauvery river chiefly takes place in the particulate form. Tributaries Hemevathi and Kabini draining highly mineralized areas contribute significantly to the heavy metal load of the Cauvery river. Particulate metal transport is influenced by the presence of major dams built across the river. Factor analysis of the elemental data identifies two major group of heavy metals, (a) Fe, Mn, Cr, V and Ti and (b) Cu, Pb and Zn in the suspended sediments of Cauvery river. Heavy metals in surface sediments show wide variations in their concentrations due to the non-uniform grain size distribution of the sediments. The elements Fe, Mn, Pb, Cu, Zn, Ni, Co and As are dominantly present in the <20 μm fraction of the river sediments. Speciation studies show that Fe-Mn oxide phase held the largest share of heavy metals in the sediments. The depth variation of heavy metals in the core sediments suggest their similar mobility during diagenesis. Geoaccumulation indices calculated suggest that Cd, Zn, Cr, Pb, Cu and Ni are enriched in sediments several times over background values.     

Origin,retention and release of trace metals from sediments of the river seine

Metallic contents (Fe, Mn, Pb, Cu, Cd, Zn, Cr) of sediments were measured in 14 sites in the River Seine (France) along 110 km; in three sites surrounding the sewage treatment plant at Achères, vertical profiles were established from cores and dialysis cells, and interface exchanges have been studied. Metal contamination increases downstream, except for Pb for which contamination is higher immediately downstream of stormdrains (up to 130 mg kg^?1); that confirms its urban origin. Upstream of Achères, metallic contamination increases with depth while downstream, contribution to sediments of suspended matter from the treatment plant, loaded with organic matter, alters the behaviour of metals within the first ten centimeters. A strong link between particulate organic carbon (POC), polycyclic aromatic hydrocarbons (PAH), polychlorobiphenyls (PCB) and metal contents has been established. The organic matter brought down by the treatment plant effluents induces a specific diagenesis downstream leading to metal release in summer as attested by a 30% metal contents decrease in sediments. Calculation of molecular diffusion fluxes shows that in september, the release phenomenon is ending.     

不同水动力下湖泊沉积物重金属释放通量

为探讨不同水动力下湖泊沉积物重金属释放通量,该文在室内可循环式水槽试验中模拟了动水条件下沉积物的运动,试验时通过控制闸门开关改变水槽内水体流速,探讨了不同水动力下沉积物的悬浮与释放规律。以鄱阳湖沉积物为水槽试验沉积物,通过分析沉积物中Cu、Zn、Cd、Pb浓度的变化,建立了当沉积物粒径为50~200μm时,沉积物中Cu、Zn、Cd、Pb释放通量与流速的关系式。结果表明:释放通量随水体流速增大呈指数增长,当流速分别为15、35、65 cm/s时,Cu释放通量分别为45.82、65.18、127.16 mg/(m~2·d);Zn为104.35、139.82、220.5 mg/(m~2·d);Cd为0.116、0.163、0.28 mg/(m~2·d);Pb为4.78、6.72、11.57 mg/(m~2·d),鄱阳湖水体重金属浓度计算值与实测值误差在5%~20%范围内。研究结果可为湖泊重金属污染控制及治理提供科学依据。     

Identification of the sources of metals and arsenic in river sediments by multivariate analysis and geochemical approaches

Purpose

Frequent mining activities and higher background values in soil have led to the contamination of the sediments of some rivers in southwest China by several metals and arsenic (As). This study combined multivariate analysis with geochemical approaches to differentiate mining activity from other sources, which may aid to evaluate the effectiveness of reducing mining release.

Materials and methods

Sixteen sediment samples were collected along the Yuan River, China. The total concentrations of lead (Pb), zinc (Zn), copper (Cu), cadmium (Cd), chromium (Cr), mercury (Hg), and As were measured by inductively coupled plasma-atomic emission spectrometer (ICP-AES). The Pb isotopic composition was measured using a thermal ionization mass spectrometer (TIMES). Both geochemical approaches and multivariate statistical analysis were used to identify the sources of these metals. The fractionation of Pb was determined through a Community Bureau of Reference (BCR) sequential extraction procedure to aid the identification of the sources.

Results and discussion

The concentrations and enrichment factors (EFs) of Pb, Zn, Cu, Cd, and As in the middle reach of the river were higher than those at the other sites, indicating anthropogenic sources. The factor analysis (FA) extracted “mining and smelting,” “mixture of anthropogenic and natural,” and “natural” factors. The Pb isotope composition of metal ores was similar (²⁰⁶Pb/²⁰⁷Pb?<?1.190 and ²⁰⁸Pb/²⁰⁶Pb?>?2.023) to that found in the sediments in the middle reach, indicating anthropogenic sources of mining activities. Compared with the narrow ranges of the δ³⁴S ratios in the bedrock (+8.5 to +9.3?‰) and the metal ores (?1.4 to +1.9?‰), the sediment samples presented a relatively wide range of δ³⁴S ratios from ?2.6 to +9.2?‰ with a mean of +2.6?‰, which suggests a mixed composition. The BCR sequential extraction procedure revealed that the proportion of the extractable fraction in the sediments in the middle reach was higher than that in other sites, suggesting anthropogenic sources as the cause of contamination in the study area.

Conclusions

Lead, Zn, Cu, Cd, Cr, Hg, and As are mainly derived from natural materials in the upstream region. In the middle reach, these elements are the result of anthropogenic activities, particularly activities associated with the mining industry. In the downstream region, the origin of these elements is considered to be a mixture of anthropogenic and natural sources. In addition to geochemical approaches and multivariate statistical analysis, the BCR sequential extraction method is an effective procedure for the identification of the anthropogenic sources of sediment-associated metals.     

Selective removal of heavy metals from contaminated kaolin by chelators

The competitive desorption/dissolution of kaolin-adsorbed heavy metal mixtures and mixtures of adsorbed Cd with Mg and/or Ca by four chelators (NTA, EDTA, EGTA, and DCyTA) was investigated. Metals were adsorbed on kaolin at pH 7 and the effects of chelator type and concentration on the extent of metal dissolution was studied at a solution pH of 10. EGTA addition. EGTA was the most effective chelator in selectively removing Cd from kaolin in the presence of adsorbed alkaline-earth metals. Approximately 90% of the adsorbed Ca and Mg were retained on the kaolin until almost all (> 80%) of the cadmium was dissolved by EGTA chelator. NTA was the least effective chelator in selectively dissolving Cd from kaolin contaminated with both Cd and Ca (≈ 45% of the adsorbed Cd could not be removed). All four chelators exhibited some desorption/dissolution selectivity for Cd, Cu, and Pb adsorbed on kaolin. When the concentration of chelator in solution was insufficient to dissolve all adsorbed metals, the observed metal ordering for chelation and dissolution was Cd > Cu > Pb (for EGTA), Cd > Pb > Cu (for EDTA and DCyTA), and Cu > Cd > Pb (for NTA).     

Spatial and temporal variation of heavy metals in sediment cores from the calcasieu river/lake complex

Sediment cores were obtained from several locations in the Calcasieu River/Lake Complex (Lousiana), including Calcasieu Lake, Calcasieu River, two bayou tributaries, and Lake Charles, during the period from November 1983 to November 1985. The cores were analyzed for Cu, Zn, Cr, and Pb. The approximate sedimentation rate and a core chronology were determined by the use of ¹³⁷Cs and ²¹⁰Pb. The increase in metal concentrations after 1933, particularly along Bayou d'Inde where most industries are located, points to anthropogenic input of these metals to the system. The fact that metal concentrations tend to merge to a common value prior to 1940 throughout the system suggests that geological factors do not contribute to the observed variations in metal concentrations of heavy metals found in this area. The background concentrations of heavy metals found in this study for the Calcasieu River/Lake Complex were: Cu (10 mg kg^?1), Cr (25 mg kg^?1), Pb (8 mg kg^?1), and Zn (40 mg kg^?1), The main emphasis of the study focused along Bayou d'Inde due to the enhanced levels of heavy metals found.     

Assessment of ex-situ chemical washing of heavy metals from estuarine sediments around an industrial harbor in Southern Taiwan

Journal of Soils and Sediments - Harbor sediments normally accumulate the pollutants from municipal and industrial activities in the estuarine zone. This work aimed to characterize the...     

Forms and distribution of heavy metals in soils of the Axios delta of northern Greece

Abstract

Distribution and availability of heavy metals to plants is important when assessing the environmental quality of an area. The objectives of this study, conducted in 1992–1993, were: a) to determine the levels of the heavy metals, cadmium (Cd), chromium (Cr), copper(Cu), lead (Pb), manganese (Mn), nickel (Ni), and zinc (Zn), in the soils of the Axios Delta (a Ramsar wetland site in Northern Greece) so that the degree of pollution could be ascertained, b) to identify the various heavy metal forms present in soils using a fractionation scheme based on sequential extraction, and c) to find possible dependence on soil physicochemical properties. Total heavy metal content of the soils studied was generally higher than the levels reported in the literature for similar soils, suggesting some degree of pollution with heavy metals. The exchangeable forms of the heavy metals, however, were very low indicating that under present conditions, the availability of the heavy metals to plants is at a minimum. Most of the heavy metals occurred in forms that are considered immobile constituents of inorganic minerals or carbonate compounds. Only Cu and Zn were present in appreciable quantities as organically‐based forms that can become potentially available under certain conditions. Spatial distribution of Zn and Cu was related to the organic matter distribution, and there were indications suggesting that the immobile fraction of the heavy metals was adsorbed on to Mn‐oxides.     

Total petroleum hydrocarbons and heavy metals in road-deposited sediments in Tijuana,Mexico

Purpose

A study was carried out to evaluate the concentration of heavy metals (Pb, Cu, Cr, Cd, and Hg) and total petroleum hydrocarbons (TPH) in road-deposited sediments (RDS) from Tijuana, Mexico, and identify their possible sources.

Materials and methods

Thirty RDS samples were randomly collected during the dry season using a brush and dustpan and classified according to construction material, traffic intensity, and land use. Soil samples were collected from a nonurban area and their concentrations were used as background values. For TPH, the samples were quantified gravimetrically after Soxhlet extraction, whereas heavy metals were extracted by acid digestion and their concentrations were measured by atomic absorption spectrometry.

Results and discussion

The mean TPH concentrations for RDS were 4208 mg kg^?1 and ranged from 1186 to 9982 mg kg^?1. For heavy metals, mean concentrations were 31.8, 50.2, 17.1, 0.1, and 0.1 mg kg^?1 for Pb, Cu, Cr, Cd, and Hg, respectively. The Igeo results showed that RDS from Tijuana are moderately to strongly polluted with Pb and Cu and moderately polluted with Cr. Principal component analysis (PCA) showed that Pb, Cu, and Cr could have their origin in tire wear, brake pads, bearings, and bushings.

Conclusions

The findings of this study revealed that RDS from Tijuana are polluted with TPH and heavy metals and that their principal sources are anthropogenic activities.

     

The distribution of heavy metals in sediments of Sörfjord,West Norway

The bottom sediments of Sörfjord, West Norway, contain unusually high concentrations of Ag, Ba, Bi, Cd, Cu, In, Pb, Sb, Sn, and Zn. The concentrations of Zn and Pb reach ～ 10% by weight in some sediments. The concentrations of most of the elements are positively correlated, those of Pb, Cd, and Cu with Zn being particularly well developed; correlations also exist between Sb and Zn, and Ag and Cu. The concentrations of the metals in the bottom sediments decrease southwards and northwards from a locality close to a source of industrial waste.     

Incidence of heavy metals in street surface sediments: Solubility and grain size studies

Samples of surface and gutter sediment from roads within N.W. London have been analyzed for levels of Cd, Cu, Fe, Mn, Pb, and Zn. Sediment and associated metal grading curves are presented and apart from Mn and Fe which reflect natural background levels, the remaining metals show distributions which relate to road type and traffic conditions. For highways carrying the highest traffic densities the concentrations of Cd and Pb are greatest for grain sizes between 100 and 500 µm and an aggregation process is postulated. Residential side street samples show a marked affinity of Cd, Fe, and Zn for the coarsest grain fractions. Laboratory sorption and desorption studies are described and solution concentrations are obtained for Cd, Cu, Mn, Pb, and Zn over 1 to 30 day time periods. Solubility curves are typically variable with time. The relationship of leachate patterns to particle size and sample site location is discussed and its relative importance to Stormwater loadings is considered. Extraction efficiencies for the five metals are found to be independent of road type and in the order Cd > Zn, Cu > Mn > Pb. The relevance of this hierarchy to Stormwater toxicity is discussed.     

The effect of heavy metals and other pollutants on the sediments of Onondaga Lake

Physical and chemical characterization of the recent sediments of Onondaga Lake indicate significant pollution based alterations to the system.²¹⁰Pb data depict an extremely high sedimentation rate within the consolidated layers (5 to 9 cm yr^?1), that has resulted largely from the loading of the Lake with industrially derived Ca. A further alteration of the sedimentary system is the very extensive flocculent layer (up to 2.5 m deep) between the overlaying water and the consolidated sediments. The chemistry of the sediments, though not unusual in dominant component makeup for a hardwater lake, is characterized by very severe heavy metal and Fe contamination that has resulted from culturally derived loadings. Heavy metals and P are concentrated within the upper flocculent strata. Indirect evidence is presented for the upward vertical migration of heavy metals within the sedimentary system.     

太湖重金属污染沉积物中的铁硫地球化学特征及其与相关重金属的关系

To understand the geochemical characteristics of iron and sulfur and the extent of iron-sulfide minerals influencing heavy metal behaviour in metal-polluted sediments of Talhu Lake, two sites, in Meiliang Bay （ML） and Wuli Lake （WL）, were selected to study the fractionation of iron, sulfur and related heavy metals. There were relatively high concentrations of Fe^2＋ and low concentrations of total S^2- in porewaters, indicating that conditions in these sediments favored iron reduction. The concentrations of acid volatile sulfides in sediments were 1.9-9.6 μmol g^-1 at ML and 1.0-11.7 μmool g^-1 at WL, both in the range of values detected in unpolluted lakes. Pyrite-S was 10.2-49.4 μmol g^-1 at ML and 10.3- 33.0 μmol g^-1 at WL, accounting for more than 69% of the reduced inorganic sulfur at both sites. The low degree of sulphidization （〈 14%） and pyritization （〈 10%） indicate that sulfate may be the limiting factor for pyrite formation. The extractability of Mn, Cu, Pb, Zn, Ni, and Cr in sediments all suggest that sulfides are not the major binding phase for these metals during early diagenesis. Sulfur may play a modest role in the geochemistry of iron and traced metals in the sediments.     

Retention of heavy metals from blast-furnace dedusting sludges by a clayey subsoil

The suitability of a clay (Upper Liassic) as barrier for a heavy metal disposal site had been investigated by analysing the subsoil of an approximately 40 yr old blast-furnace dust dump on this clay. Concentration profiles show that the heavy metals (mainly Zn and Pb) have been retained by sorption processes in the upper 5 to 10 cm below the clay/waste interface. Heavy-metal migrated into the clay by pure diffusion with an effective diffusion coefficient of 1.5 × 10^–9 cm² s^–1, which corresponds to a retardation factor R between about 600 and 2100. It could be concluded that there is no potential risk of groundwater pollution because the subsoil, a 3 m thick plastic clay underlain by a 40 m thick clay rock, has a sorption capacity high enough to retain all heavy metals leachable from the dust dump.     

Elimination of heavy metals from process waters of the bioleaching process by electrolysis

2 Conclusions  The investigations into the membrane electrolysis cell show that electrochemical metal separation from bioleaching process waters can represent a practical alternative for metal separation by alcalization, Coal and platinized titanium material exhibit good anodic resistance at the current densities tested. By contrast, high-grade steel and to some extent lead anodes were dissolved and are hence unsuitable for this purpose. However, for practical application, suitable ways are required to discharge the precipitates containing heavy metals deposited on the electrodes from the electrolysis cell and to prevent membrane clogging. Regarding the main components zinc, manganese, and nickel, the combination electrodes proved to be suitable for eliminating the heavy metals from the aqueous phase. Another way of treating diluted process waters containing sulphuric acidic and heavy metals is to concentrate the sulphuric acid in the anode region and to precipitate the heavy metals in the cathode region. The sulphuric acid recovered could then be returned to the leaching process, hence avoiding wastewater.     

Application of a plant bioassay for the evaluation of ecotoxicological risks of heavy metals in sediments affected by mining activities

Purpose

The objective of this work was to evaluate the effectiveness of a plant bioassay (Phytotoxkit®) for screening ecotoxicological risks in sediments affected by mining activities.

Materials and methods

A total of 42 sediment samples affected by mining activities were studied, including 39 sediment samples from the Sierra Minera, Spain, an area affected by old extraction procedures, and three sediments from an area affected by opencast mining. These three samples were then mixed with limestone filler at 10, 20 and 30 %, providing nine stabilised samples. The total and soluble metal(loid) content (As, Cd, Cu, Fe, Pb and Zn) was determined in all samples, and the Phytotoxkit® bioassay was applied to determine the ecotoxicological effect of this procedure.

Results and discussion

The stabilised material had a neutral pH and low soluble metal(loid) concentration, similar to that of samples in which a natural attenuation process had taken place because of mixing with surrounding carbonate-rich materials. An ecotoxicological survey identified the low toxicity levels of the stabilised samples.

Conclusions

The applied bioassay is a good tool for screening metal(loid) contamination in areas affected by mining activities, since it provides information on both natural and simulated attenuation processes. The mixing of sediments with limestone filler could be applied to the remediation of zones affected by mining activities, because the toxicological effect on the tested organisms in the stabilised sediments was reduced significantly and the metal(loid) content was diminished.