Trace Element Contamination Research Articles

Soil trace elements contamination in the vicinity of Khatoon Abad copper smelter, Kerman province, Iran

Continuous deposition from Khatoon Abad smelter stack particulates has resulted in trace elements contamination in soil. To investigate the regional distribution and fractionation of trace elements in soils, soil samples were collected and examined. The results demonstrate that the highest trace element concentrations in top soil are: >10000 mg Cu kg-1, 2000 mg Mo kg-1, >10000 mg Zn kg-1, 2694.2 mg As kg-1, 2006.2 mg Pb kg-1, 420.4 mg Sb kg-1, and 90.7 mg Cd kg-1. The concentrations of the trace elements are much higher than the normal concentrations in the uncontaminated soil and geochemical background. The most contaminated areas are located in the vicinity of smelter in the prevailing wind directions. Calculated geoaccumulation index and contamination load index indicate surface soil enrichment in potentially toxic metals (Cu, Mo, As, Sb, Cd, Zn, and Pb). Combined multivariate statistical and geostatistical methods successfully separate the contaminant metals (As, Cd, Cu, Pb, Sb, Mo, and Zn) from the uncontaminated ones (Al, Fe, Mn, and Cr). Furthermore, it was found that the As, Cd, Cu, Pb, Sb, Mo, and Zn mainly come from the copper smelter. The modified BCR three-step sequential extraction technique was applied to assess the four fractions (residual, acid, reducible and oxidizable) in smelter dust and surface soil samples. The results demonstrate that a high proportion of Cu, Mo, As, Pb, Sb, and Zn is extracted in the mobile fractions, indicating high mobility and probably hazardous environmental consequences.

Trace elements in different land use soils of Bangladesh and potential ecological risk.

Bogra city is highly susceptible to environmental pollution due to overpopulation, rapid industrialization, and urbanization during the last decades. The levels of six trace elements (chromium, nickel, copper, arsenic, cadmium, and lead) in seven different land use soils in Bangladesh were assessed. The ranges of Cr, Ni, Cu, As, Cd, and Pb in studied soils were 6.3-256, 8.3-271, 13-279, 7.5-87, 0.09-29, and 5.3-624mg/kg, respectively. The pollution load index (PLI) values for all land uses were higher than 1, indicating the progressive deterioration of soil due to trace elements contamination. In view of the potential ecological risk (PER), soils from all land uses showed moderate to very high potential ecological risk. Among the elements, As and Cd showed a higher potential ecological risk than the others.

Abnormal trace element concentrations in a shallow aquifer belonging to saline reclaimed environments, Codigoro (Italy)

Geogenic trace element (TE) contamination is an upcoming concern. The present study reports the temporal and spatial variation of major ions and TEs in a shallow unconfined aquifer belonging to a complex marsh saline environment reclaimed in modern age and intensively cultivated. The use of intensive depth profiles in five different locations gave insights into groundwater and sediment matrix interactions. Data indicate that the dominant factor involved in determining the spatial variability of TE is the sediment–water interaction, while the temporal variation of TE is due to the organic matter content and to the water table oscillation, which in turn drive the groundwater redox status and the mobilization of some inorganic microconstituents, such as Fe and Mn. Despite that the anthropogenic input of TEs in groundwater from fertilizer sources cannot be undoubtedly ruled out, given the elevated TE background concentrations, the combined use of high-resolution sediment profiles, seasonal groundwater sampling and end-member analyses is a promising procedure to distinguish between anthropogenic metal contamination and geogenic contribution in reclaimed deltaic environments. Finally, this study underlines the need of having a dense piezometer network and to perform several monitoring campaigns to ensure that the temporal and spatial variability could be correctly represented and background values of TE confidently determined.

Influence of ore deposits on river sediment compositions in Dan River drainage, China

We mainly investigated trace element contamination of surface sediments in the Dan River drainage, the source of drinking water for the South to North Water Transfer Project, China, to determine trace element sources and associated levels of risk. Sediment samples were collected at 95 sites along the Dan River in connection with field surveys, and total element concentrations were determined using inductively coupled plasma-mass spectrometry (ICP-MS). Concentrations of most elements were lower than background levels; however, toxic heavy metals, such as As, Cd, Pb, and Sb, showed extremely high concentrations at sites associated with nearby metal ore deposits. Moreover, the spatial variations of contamination by some heavy metals were directly related to the distributions of metal ore deposits in the North and South Qinling terrains; sediment samples with especially high concentrations of Sb and As were from the North Qinling terrain, while sediments with especially high concentrations of Cd and Pb were from the South Qinling terrain, suggesting that metal ore distributions and associated mining activity strongly influence the distribution of heavy metals and heavy metal contamination in the Dan River drainage. Multivariate techniques, including Pearson correlation, hierarchical cluster, and factor analysis, were used to assess the sources of metal contamination. Results indicate that distributions of Al, Ba, Cu, Fe, Mg, Mn, Pb, Sn, Ti, V and Zn are controlled by natural sources; Co and Cr by a combination of geological and anthropogenic inputs; whereas As, Cd, Ni, Sb, and Pb appear to be primarily of anthropogenic origin. The ecological risk associated with heavy metal contamination of sediments was rated as moderate, based on an assessment using geo-accumulation index (Igeo), enrichment factor (EF), potential ecological risk index (RI) and mean probable effect concentration quotient (mPECQ).

Linking trace element variations with macronutrients and major cations in marine mussels Mytilus edulis and Perna viridis.

Marine mussels have long been used as biomonitors of contamination of trace elements, but little is known about whether variation in tissue trace elements is significantly associated with those of macronutrients and major cations. The authors examined the variability of macronutrients and major cations and their potential relationships with bioaccumulation of trace elements. The authors analyzed the concentrations of macronutrients (C, N, P, S), major cations (Na, Mg, K, Ca), and trace elements (Al, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Ba, Pb) in the whole soft tissues of marine mussels Mytilus edulis and Perna viridis collected globally from 21 sites. The results showed that 12% to 84% of the variances in the trace elements was associated with major cations, and the tissue concentration of major cations such as Na and Mg in mussels was a good proxy for ambient seawater concentrations of the major cations. Specifically, bioaccumulation of most of the trace elements was significantly associated with major cations, and the relationships of major cations with trace cations and trace oxyanions were totally opposite. Furthermore, 14% to 69% of the variances in the trace elements were significantly associated with macronutrients. Notably, more than half of the variance in the tissue concentrations of As, Cd, V, Ba, and Pb was explained by the variance in macronutrients in one or both species. Because the tissue macronutrient concentrations were strongly associated with animal growth and reproduction, the observed coupling relationships indicated that these biological processes strongly influenced the bioaccumulation of some trace elements. The present study indicated that simultaneous quantification of macronutrients and major cations with trace elements can improve the interpretation of biomonitoring data.

Investigation of aerosol trace element concentrations nearby Algiers for environmental monitoring using instrumental neutron activation analysis

The aim of this study was to enhance the use of instrumental neutron activation analysis (INAA) for long-term monitoring of air pollution and to identify critical sources of air pollution. For the collection of total suspended particulate matter (TSP), a filter unit low volume sampler (LVS) was employed. One hundred and seventeen samples were collected during 2010, 2011, and 2012, both on weekdays and weekends at a monitoring station located in Draria city, a suburban site near Algiers, Algeria. The concentrations of 25 trace elements (As, Br, Ca, Cd, Ce, Cl, Co, Cr, Cs, Eu, Fe, Gd, Hf, K, La, Mn, Mo, Na, Sb, Sc, Se, Sm, Sr, V, and Zn) were determined by INAA using short and long neutron irradiation technique. Generally lower concentration values were observed during the weekends compared to the weekdays for almost all elements. The mean TSP concentration (34.8μg/m3) showed a seasonal pattern with higher levels during summer. The weekday/weekend ratio of TSP was 1.3 higher during summer than in winter. The concentrations of the elements Sb, Se, and Cd are found to be highly enriched in atmospheric particulate matter. According to their high enrichment factors (EFs), it was possible to establish that these elements are of anthropogenic origin coming from automobile exhausts which is the main source of emission in this area. The typical suburban background TSP and trace element levels were compared with literature data from other regions around the world, and were lower than those reported in an urban site in Algiers in a previous study. Significant correlations between elements were found (Pearson's coefficients >0.5) suggesting that the contaminant trace elements may be discharged from the same sources.

Lipid and fatty acid biomarkers as proxies for environmental contamination in caged mussels Mytilus galloprovincialis

Mussels (Mytilus galloprovincialis) were transplanted from a reference site (Syracuse harbour) to an impacted site (Augusta Bay) from January to July 2013 to assess the biochemical response of caged mussels to high trace element and polycyclic aromatic hydrocarbon (PAH) contamination, using lipid and fatty acid (FA) biomarkers. Sediment and mussels were analysed to assess contaminant bioavailability in the study sites and bioaccumulation in mussel tissue. Trace elements (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, V, Zn) and PAHs were significantly higher in mussels from Augusta than in those from Syracuse, mirroring the different environmental contamination. The biological impact quotient (BIQs), which indicates the potential biological impact of mussel-accumulated contaminants, reflected the highest contaminant concentrations found in Augusta and their temporal trend, which increased from the start of the experiment to 3–4 months after transplanting, followed by a decrease, as indication of mussel detoxification processes. Lower condition index (CI) and phospholipids (PL), as well as higher total (TL) and neutral lipids (NL) in mussels from Augusta, indicated the occurrence of a physiological and biochemical stress response to pollutant exposure and accumulation. Differences in FA composition, especially polyunsaturated (PUFA), essential (EFA) and non-methylene interrupted dienoic (NMID) FAs between the study sites revealed the occurrence of stress-induced lipid peroxidation, followed by compensatory/adaptive processes in Augusta mussels. The marked increase in bacterial biomarkers, mainly cyclopropyl (CY) FAs, reflecting the greater bioaccumulation of chemicals in the Augusta mussels, may be the result of bacterial infections or symbiosis with bacteria involved in detoxification processes.

Arbuscular mycorrhizal fungal inoculation protects Miscanthus × giganteus against trace element toxicity in a highly metal-contaminated site

Arbuscular mycorrhizal fungus (AMF)-assisted phytoremediation could constitute an ecological and economic method in polluted soil rehabilitation programs. The aim of this work was to characterize the trace element (TE) phytoremediation potential of mycorrhizal Miscanthus×giganteus. To understand the mechanisms involved in arbuscular mycorrhizal symbiosis tolerance to TE toxicity, the fatty acid compositions and several stress oxidative biomarkers were compared in the roots and leaves of Miscanthus×giganteus cultivated under field conditions in either TE-contaminated or control soils. TEs were accumulated in greater amounts in roots, but the leaves were the organ most affected by TE contamination and were characterized by a strong decrease in fatty acid contents. TE-induced oxidative stress in leaves was confirmed by an increase in the lipid peroxidation biomarker malondialdehyde (MDA). TE contamination decreased the GSSG/GSH ratio in the leaves of exposed plants, while peroxidase (PO) and superoxide dismutase (SOD) activities were increased in leaves and in whole plants, respectively. AMF inoculation also increased root colonization in the presence of TE contamination. The mycorrhizal colonization determined a decrease in SOD activity in the whole plant and PO activities in leaves and induced a significant increase in the fatty acid content in leaves and a decrease in MDA formation in whole plants. These results suggested that mycorrhization is able to confer protection against oxidative stress induced by soil pollution. Our findings suggest that mycorrhizal inoculation could be used as a bioaugmentation technique, facilitating Miscanthus cultivation on highly TE-contaminated soil.

Assessing trace element contamination in Fildes Peninsula (King George Island) and Ardley Island, Antarctic

King George Island, situated in the South Shetland Islands archipelago, is one of the most visited sites in Antarctica. This has contributed to a high density of scientific stations and shelters in the region, especially in Fildes Peninsula. In order to evaluate the natural and anthropogenic sources of trace elements (As, Cd, Cu, Zn, Pb and Hg) soil and moss samples were collected from different sites in January 2013. In general, the results revealed homogeneous concentrations (μgg−1) for each element in the majority of collected samples (As: 3.8±1.4; Cd: 0.4±0.9; Cu: 34±4; Zn: 115±13; Pb: 20±5; Hg; 0.011±0.009). However, some samples in specific areas of Fildes Bay showed the existence of local anthropogenic activities that have contributed to the enrichment of contaminants in soils and moss samples that correlated to one another (e.g. Pb: 1101μgg−1).Human presence is linked to examples of contamination and environmental perturbation, making essential the implementation of this type of study in order to understand and protect unique places in Antarctica.

Potential of Ranunculus acris L. for biomonitoring trace element contamination of riverbank soils: photosystem II activity and phenotypic responses for two soil series.

Foliar ionome, photosystem II activity, and leaf growth parameters of Ranunculus acris L., a potential biomonitor of trace element (TE) contamination and phytoavailability, were assessed using two riverbank soil series. R. acris was cultivated on two potted soil series obtained by mixing a TE (Cd, Cu, Pb, and Zn)-contaminated technosol with either an uncontaminated sandy riverbank soil (A) or a silty clay one slightly contaminated by TE (B). Trace elements concentrations in the soil-pore water and the leaves, leaf dry weight (DW) yield, total leaf area (TLA), specific leaf area (SLA), and photosystem II activity were measured for both soil series after a 50-day growth period. As soil contamination increased, changes in soluble TE concentrations depended on soil texture. Increase in total soil TE did not affect the leaf DW yield, the TLA, the SLA, and the photosystem II activity of R. acris over the 50-day exposure. The foliar ionome did not reflect the total and soluble TE concentrations in both soil series. Foliar ionome of R. acris was only effective to biomonitor total and soluble soil Na concentrations in both soil series and total and soluble soil Mo concentrations in the soil series B.

Seasonal variation in trace element concentrations and Pb isotopic composition of airborne particulates during Asian dust and non-Asian dust periods in Daejeon, Korea

Trace element contamination (As, Cd, Cr, Co, Cu, Mo, Ni, Pb, S, Zn, and Zr) in both Asian dust (AD) and non-Asian dust (NAD) periods taken from Daejeon, Korea, in 2008 was examined, and the pollution sources were evaluated based on the Pb stable isotope. Additionally, temporal variation in the trace element concentrations of total suspended particulate matter, PM10 and PM2.5, was evaluated in 14 samples for AD and 46 samples for NAD collected from March 2007 to November 2008. Patterns showed that the monthly mean concentrations of trace elements in winter were 2–13 times higher than those in other seasons. In contrast, the monthly mean concentrations of sulfur were the highest in the summer monsoon season. Distinct temporal patterns were observed in the monthly mean concentrations of trace elements, due mainly to high coal combustion in China. These results were supported by the 206Pb/207Pb ratios of AD and NAD, which were identical or similar to those of the airborne particles in certain heavily industrialized Chinese cities and coal and coal combustion dust of China. The Pb isotopic composition in the particulate matter of NAD showed lower 206Pb/207Pb, 207Pb/204Pb, and 206Pb/204Pb ratios in the autumn, winter, and spring seasons, showing the influence of Pb from the heavily industrial cities of China, and higher values in the summer, indicating the dilution and/or mixing effect of the marine air mass from the south.

Lake and watershed influences on the distribution of elemental contaminants in the Rideau Canal System, a UNESCO world heritage site.

Watershed-specific variables such as sediment particle size distribution, water depth, sedimentation rate, focusing factors, and catchment area to lake area ratio can affect the distribution of trace element contaminants to lakes. The aim of this study was to investigate sources of metals to three headwater lakes and to quantify effects of watershed-specific variables on spatial and temporal trends of trace elements (As, Cd, Co, Cr, Cu, Hg, K, Ni, Pb, Rb, and Zn) in sediments and mercury (Hg) concentrations in fish. Surface sediment and water samples were used to characterize spatial patterns, while sediment cores were collected to portray temporal trends. Historical trends of Hg in northern pike (Esox lucius) were assessed in relation to paleolimnological trends of sediment Hg concentrations. Similarity in timing of sediment peak trace element concentrations for the lakes suggests large-scale, atmospheric sources. The lake with highest catchment area-to-lake area ratio was consistently associated with highest sediment elemental concentrations and displayed significant correlations between increased sediment Hg concentrations and decreased pike tissue concentrations over time. This suggests that catchment area-to-lake area ratio is an important factor influencing the concentration of atmospherically derived contaminants within lake sediments and their transfer through the food web.

Assessment of trace element pollution and its environmental risk to freshwater sediments influenced by anthropogenic contributions: The case study of Alqueva reservoir (Guadiana Basin)

The Guadiana Basin (SW Iberian Peninsula) is affected by acid mine drainage (AMD), a consequence of ancient mining activities in the Iberian Pyrite Belt (IPB). Consequently, the sediments at the Alqueva reservoir (SE Portugal) in the Guadiana Basin are potentially contaminated by trace elements, which make important: (i) to characterize the status of trace element pollution of the sediments; (ii) to evaluate the mobility and the bioavailability of As, Cd, Cu, Cr, Pb and Zn; and (iii) to assess the environmental risk associated with the total and bioavailable concentrations of trace elements, using the sediment quality guidelines (SQGs) and the risk assessment code (RAC). Metal enrichment factors (EF) and geoaccumulation indexes (Igeo), determined taking into account the regional background levels, revealed that, among the metals analyzed, Cd contributed the highest to pollution levels followed by Pb and As. Despite the trace element contamination of the Alqueva sediments, the sequential extraction showed that most of them are found in the oxidizable and residual fractions, which indicates that they are sparingly bioavailable, with exception of Cd (acid-labile fraction) and Pb (reducible fraction). Based on the RAC, Cd was the only metal that presented a high risk, while Pb, As and Zn showed a medium risk. Moreover, the SQGs revealed the existence of certain areas of extremely high risk, particularly related to high concentrations of total As and, in less extent, of Pb and Cd, associated with AMD, wastewater discharges and runoff of plant protection products from agricultural fields located near the reservoir.

Bioassessment of trace element contamination of Mediterranean coastal waters using the seagrass Posidonia oceanica

A large scale survey of the trace element (TE) contamination of Mediterranean coastal waters was performed from the analysis of Ag, As, Cd, Cu, Hg, Ni and Pb in the bioindicator Posidonia oceanica, sampled at 110 sites differing by their levels of exposure to contaminants. The holistic approach developed in this study, based on the combined utilization of several complementary monitoring tools, i.e. water quality scale, pollution index and spatial analysis, accurately assessed the TE contamination rate of Mediterranean coastal waters. In particular, the mapping of the TE contamination according to a new proposed 5-level water quality scale precisely outlined the contamination severity along Mediterranean coasts and facilitated interregional comparisons. Finally, the reliability of the use of P. oceanica as bioindicator species was again demonstrated through several global, regional and local detailed case studies.NB: The designations employed and the presentation of the information in this document do not imply the expression of any opinion whatsoever on the part of the authors concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

Just a crush? Contamination of archaeological samples by different grinding media

A chert cobble from an archaeological quarry on southern Baffin Island, Canada, was divided and crushed using five different methods: i) agate mortar and pestle, ii) stainless steel shatterbox, iii) tungsten carbide shatterbox, iv) alumina ceramic shatterbox, and v) zirconia ceramic shatterbox. Powders produced by each method were submitted for acid digestion and analysis by inductively coupled plasma mass spectrometry. The trace element results indicate that different crushing media can contribute significant trace element contamination to chert during the grinding process. These results demonstrate the need for an informed approach to the selection of sample preparation methods when submitting archaeological samples for solution or pellet based geochemical analysis.

Trace elements contamination and human health risk assessment in drinking water from Shenzhen, China.

The levels of seven essential trace elements (Mn, Co, Ni, Cu, Zn, Se, and Mo) and six non-essential trace elements (Cr, As, Cd, Sb, Hg, and Pb) in a total of 89 drinking water samples collected in Shenzhen, China were determined using inductively coupled plasma mass spectrometry (ICP-MS) in the present study. Both the essential and non-essential trace elements were frequently detectable in the different kinds of drinking waters assessed. Remarkable temporal and spatial variations were observed among most of the trace elements in the tap water collected from two tap water treatment plants. Meanwhile, potential human health risk from these non-essential trace elements in the drinking water for local residents was also assessed. The median values of cancer risks associated with exposure to carcinogenic metals via drinking water consumption were estimated to be 6.1 × 10(-7), 2.1 × 10(-8), and 2.5 × 10(-7) for As, Cd, and Cr, respectively; the median values of incremental lifetime for non-cancer risks were estimated to be 6.1 × 10(-6), 4.4 × 10(-5), and 2.2 × 10(-5) for Hg, Pb, and Sb, respectively. The median value of total incremental lifetime health risk induced by the six non-essential trace elements for the population was 3.5 × 10(-5), indicating that the potential health risks from non-carcinogenic trace elements in drinking water also require some attention. Sensitivity analysis indicates that the most important factor for health risk assessment should be the levels of heavy metal in drinking water.

A study of the impact of moist-heat and dry-heat treatment processes on hazardous trace elements migration in food waste

Using laboratory experiments, the authors investigated the impact of dry-heat and moist-heat treatment processes on hazardous trace elements (As, Hg, Cd, Cr, and Pb) in food waste and explored their distribution patterns for three waste components: oil, aqueous, and solid components. The results indicated that an insignificant reduction of hazardous trace elements in heat-treated waste—0.61–14.29% after moist-heat treatment and 4.53–12.25% after dry-heat treatment—and a significant reduction in hazardous trace elements (except for Hg without external addition) after centrifugal dehydration (P < 0.5). Moreover, after heat treatment, over 90% of the hazardous trace elements in the waste were detected in the aqueous and solid components, whereas only a trace amount of hazardous trace elements was detected in the oil component (<0.01%). In addition, results indicated that heat treatment process did not significantly reduce the concentration of hazardous trace elements in food waste, but the separation process for solid and aqueous components, such as centrifugal dehydration, could reduce the risk considerably. Finally, combined with the separation technology for solid and liquid components, dry-heat treatment is superior to moist-heat treatment on the removal of external water-soluble ionic hazardous trace elements.Implications: An insignificant reduction of hazardous trace elements in heat-treated waste showed that heat treatment does not reduce trace elements contamination in food waste considerably, whereas the separation process for solid and aqueous components, such as centrifugal dehydration, could reduce the risk significantly. Moreover, combined with the separation technology for solid and liquid components, dry-heat treatment is superior to moist-heat treatment for the removal of external water-soluble ionic hazardous trace elements, by exploring distribution patterns of trace elements in three waste components: oil, aqueous, and solid components.

Risk assessment of trace element contamination in river sediments in Serbia using pollution indices and statistical methods: a pilot study

To effectively manage potential environmental and human health impacts of contaminated river sediments, it is important that information about the source (anthropogenic vs geogenic), variability and environmental risks associated with the contamination are well understood. The present study was carried out to assess the source and severity of contamination and to undertake a risk assessment for selected elements (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn) in river sediments in Serbia. The estimate of the anthropogenic component of contamination was derived by determining the total element content and the background values for elements in sediments, and the severity of pollution was assessed by calculating a number of pollution indices including the contamination factor, the enrichment factor, the index of geoaccumulation, the ecological risk factor, the potential ecological risk index, the pollution load index, the combined pollution index, the modified degree of contamination and the toxic unit factor. This analysis indicates that river sediments in Serbia are primarily polluted with Zn, Cu and Cd. The most contaminated river systems are the Ibar, Pek, West Morava and Great Morava rivers. Mining activities were found to have a significant influence on sediment. Multivariate analyses suggested anthropogenic origins for Pb, Zn, Cd, As, Ni and Cu, whilst Fe, V, Mn, Co and Cr appear to have a mixed origin (both lithogenic and anthropogenic sources). A geochemical approach, with a calculation of pollution indices and statistical methods, is recognised as useful for the risk management of trace elements in sediments around the world.

Highly contaminated areas as sources of pollution for adjoining ecosystems: The case of Augusta Bay (Central Mediterranean)

An assessment of trace element and polycyclic aromatic hydrocarbon (PAH) contamination based on surface sediments collected in summer 2012 was carried out in Priolo Bay adjoining one of the most polluted areas of the Mediterranean Sea, the industrial Augusta harbour (Italy, Central Mediterranean). Inorganic and organic contaminants were generally not remarkable. Occasional elevated concentrations of Hg, Cd, Ni and PAHs exceeding sediment quality guidelines were detected in the northern sector of Priolo Bay, close to Augusta harbour, possibly as a result of water drainage of industrialised and urbanised areas and/or potential direct export of contaminated material from Augusta harbour, whose influence on the adjoining Priolo Bay ecosystem cannot be ruled out. By domino effect, Priolo sediments may therefore become a potential source of pollutants and may represent a threat to the biota.

Laboratory comparison of four iron-based filter materials for water treatment of trace element contaminants.

A laboratory investigation provided preliminary comparison of trace element contaminant water treatment capabilities for four iron-based filter materials. The iron-based filter materials tested were zero-valent iron (ZVI), porous iron composite (PIC), sulfur modified iron (SMI), and iron oxide/hydroxide (IOH). Two types of trace element contaminant solutions were tested, one combined As, Cr, and Se (added as AsO4(3-), CrO4(2-), and SeO4(2-), respectively), while the second combined Cd2+, Cu2+, and Pb2+. The laboratory investigation included saturated falling-head hydraulic conductivity tests, contaminant removal-desorption/dissolution batch tests, and low-to-high flow rate saturated solute transport column tests. Hydraulic conductivity test results indicate that all four iron-based filter materials have sufficient water flow capacity as indicated by saturated hydraulic conductivity values greater than 1 x 10(-2) cm/s. Essentially, 100% of each trace element (As, Cd, Cr, Cu, Pb, and Se) was removed by SMI during the contaminant removal portion of the batch tests and during the column tests, while IOH exhibited good removal of each trace element except Se. Results from the contaminant removal portion of the batch tests and from the column tests showed ZVI and PIC were effective in treating Cd, Cr, Cu, and Pb. With the exception of Se adsorption/precipitation onto IOH, the desorption/dissolution portion of the batch tests showed that once As, Cd, Cr, Cu, Pb, or Se are adsorbed/precipitated onto ZVI, PIC, SMI, or IOH particle surfaces, these trace elements are then not readily desorbed or dissolved back into solution.