Potentially Toxic Trace Elements Research Articles

Pb dispersion pathways in mountain soils contaminated by ancient mining and smelting activities

Over the last millennia, mining and smelting activities have produced large amounts of mine and metallurgical wastes that remain enriched in potentially toxic trace elements (PTE). A spatial distribution of Pb content was coupled to mineralogical observations and single extraction tests to characterise the Pb contamination legacy and Pb dispersion trajectories in an ancient mining and smelting site that has been abandoned for approximatively 200 years. In the Peisey-Nancroix Pb–Ag mine (Savoy, France), extreme anthropogenic Pb contamination is located close to the slag heaps and along ore and slag transport paths. The contamination gradient is restricted to a few hundred metres downhill, down to background Pb values. The Pb-bearing phases change along the contamination gradient. The most contaminated soils contain significant amounts of galena and slags that are more or less weathered into pyromorphite and cerussite. Pb-bearing Mn (hydr-)oxides are the most stable and ubiquitous forms of Pb, which proportions increase downgradient. Despite the presence of some stable Pb-bearing phases (pyromorphite, Pb-bearing Mn (hydr-)oxides), extraction tests indicate that a small proportion of Pb may still be mobile over time.

Innovative experimental approach for spatial mapping of source-specific risk contributions of potentially toxic trace elements in PM10

Exposure to potentially toxic trace elements (PTTEs) in inhalable particulate matter (PM10) is associated with an increased risk of developing cardiorespiratory diseases. Therefore, in multi-source polluted urban contexts, a spatially-resolved evaluation of health risks associated with exposure to PTTEs in PM is essential to identify critical risk areas. In this study, a very-low volume device for high spatial resolution sampling and analysis of PM10 was employed in Terni (Central Italy) in a wide and dense network (23 sampling sites, about 1 km between each other) during a 15-month monitoring campaign. The soluble and insoluble fraction of 33 elements in PM10 was analysed through a chemical fractionation procedure that increased the selectivity of the elements as source tracers. Total carcinogenic risk (CR) and non-carcinogenic risk (NCR) for adults and children due to concentrations of PTTEs in PM10 were calculated and quantitative source-specific risk apportionment was carried out by applying Positive Matrix Factorization (PMF) to the spatially-resolved concentrations of the chemically fractionated elements. PMF analysis identified 5 factors: steel plant, biomass burning, brake dust, soil dust and road dust. Steel plant showed the greatest risk contribution. Total CR and NCR, and source-specific risk contributions at the 23 sites were interpolated using the ordinary kriging (OK) method and mapped to geo-reference the health risks of the identified sources in the whole study area. This also allowed risk estimation in areas not directly measured and the assessment of the risk contribution of individual sources at each point of the study area. This innovative experimental approach is an effective tool to localize the health risks of spatially disaggregated sources of PTTEs and it may allow for better planning of control strategies and mitigation measures to reduce airborne pollutant concentrations in urban settings polluted by multiple sources.

Risk assessment of potentially toxic trace elements via consumption of dairy products sold in the city of Yerevan, Armenia

The study aimed to investigate the potentially toxic trace elements (PTEs) Pb, Cd, Hg, Mo, and Cu in dairy products sold in Yerevan's markets and to assess the related exposure and possible health risks among the adult population residing in the capital city of Armenia, Yerevan.The PTEs contents were determined in widely consumed dairy products (pasteurized milk, sour cream, matsoun and cheese from cow milk) using graphite furnace atomic absorption spectrometry. PTE contents were in the range of 7.90E-04 (Pb in pasteurized milk) to 6.75E-01 (Cu in cheese) mg/kg. Food consumption was assessed by the 24-h dietary recall method. The PTE daily intakes and margin of exposure (MOE) were calculated by the deterministic approach.The results indicated potential health concerns for the contribution of dairy products to the overall dietary intake of Pb and Cd. MOEs of Pb and Cd (8.71 and 8.80, respectively) estimated for high consumers of cheese (90 g/day and more) were lower than 10. The pilot data set provides the first comprehensive appraisal on the dairy products contamination by PTEs in the Caucasus region. The results point out further attention to sources of Pb and Cd in Armenian dairy products, including environment and farm characteristics.

Blood concentrations of potentially toxic trace elements (PTEs) and correlation with biochemical and hematological parameters in dogs from thrace region, Turkey

Environmental exposure to potentially toxic trace elements (PTEs) leads to health problems in animals as well as in humans. Dogs can be used as bioindicators for health status of both environment, animals and humans. The study material consisted of a total of 140 dogs from Thrace region in Turkey. Essential (Co, Cr, Cu, Fe, Zn) and non-essential (As, Cd, Hg, Ni, Pb) PTEs concentrations of blood samples were determined by ICP-MS. In addition, hemogram (RBC, MCV, MCH, MCHC, HCT, WBC, HGB, PLT) and biochemical parameters (Glucose, total protein, albumin, globulin, total bilirubin, triglyceride, cholesterol, BUN, AST, ALT, ALP, GGT) levels were determined. The possible correlations between PTEs and blood parameters were investigated. The results were compared according to gender, age (<2, 2–5, >5 years), sampled location with hemogram and biochemistry data. Essential element concentrations (ppb) were sorted as Zn > Fe > Cu > Cr > Co, and non-essentials were As > Ni > Pb > Hg > Cd. There were statistically important negative or positive correlations between elements and hematological (except Fe and Cd), and biochemical parameters (except Ni) (p < 0.05, p < 0.01). It was determined that Pb concentrations (9.34–23.30 ng ml−1) were below the concentrations considered to be toxic in all locations, Cu concentrations (475.35–521.98 ng ml−1) were within the normal reference range, Zn (3229.65–4.265.00 ng ml−1) were higher than the reference values in all locations. Since the concentrations of elements and correlations between hematological, biochemical parameters as well as gender, age, and location in an area with heavy urban and industrial activity; indicate that the situation may be similar for other living things in the region, it constitutes a starting point for studies to be carried out in this direction.

Accumulation of potentially toxic trace elements (PTEs) by native plant species growing in a typical gold mining area located in the northeast of Qinghai-Tibet Plateau.

Though gold mines provide significant economic benefits to local governments, mining causes soil pollution by potentially toxic trace elements (PTEs) in mining areas, especially in the Qinghai-Tibet Plateau. Screening of native plant species from mining areas is now an effective, inexpensive, and eco-friendly method for the remediation of PTEs in situ. In the present study, we conducted experiments to assess the accumulation of As, Cd, Pb, and Zn in 12 native plant species growing on a typical gold mining area in the Qinghai-Tibet Plateau. Our results showed that rhizosphere soils have high soil organic matter content, high levels of As, and moderate levels of Cd. Geranium pylzowianum accumulated relatively higher As in its shoots and exhibited translocation factor (TF) higher than 1 for As (4.65), Cd (1.87), and Pb (1.36). Potentilla saundersiana had bioconcentration factor of shoot (BCF-S) higher than 1 for Cd (4.52) and Pb (1.70), whereas its TF was higher than 1 for As, Cd, Pb, and Zn. These plant species exhibit strong tolerance to these PTEs. Furthermore, Elymus nutans accumulated low levels of As, Cd, Pb, and Zn in their shoots and exhibited TF values lower than 1 for the four PTEs. Therefore, G. pylzowianum is a promising candidate for the in situ phytoextraction of As, and P. saundersiana can be used as an effective plant for Cd and Pb phytoextraction. E. nutans is better suited for the phytostabilisation of multiple PTEs. This work is of significant importance for screening native plant species that can provide a reference for phytoremediation of PTE-contaminated soils in this area or other place with similar climate, and has a good potential for developing PTE phytoremediation strategies at mining sites.

Mycorrhizal stress alleviation in Senecio bonariensis Hook & Arn growing in urban polluted soils.

Loss of biodiversity and accumulation of contaminants in urban soils and water bodies cause serious issues in metropolitan areas. The Matanza-Riachuelo river basin (metropolitan area of Buenos Aires, Argentina) is one of the most environmentally degraded regions in the world. Senecio bonariensis Hook & Arn (Asteraceae) grows in the periodically flooded soils of this wetland. This plant concentrates potentially toxic trace elements (PTEs) in its tissues and establishes symbiosis with arbuscular mycorrhizal (AM) fungi that collaborate with PTE phytostabilization in soils. The objective of this work was to evaluate tolerance and stress alleviation of AM-colonized S. bonariensis when transplanting and exposing to highly polluted environmental conditions of the river basin. Plants were initially inoculated with different AM strains and maintained in greenhouse conditions. After 6 mo, they were transplanted to the field. These plants showed a more equal distribution between shoot and root biomass production in comparison to field spontaneous S. bonaerensis plants. Plants in earlier contact with native soil inoculum showed positive correlation with phosphorus content and a significant increase of vesicle frequency. Plants belatedly contacted with native inoculum in the field (control) showed a higher catalase level that was positively correlated with the total colonization frequency and chlorophyll content. The ability to establish symbiosis with Rhizophagus intraradices (strain GC3), commonly used in the formulation of biofertilizers, was also analyzed. Plants inoculated with GC3 at the beginning of the assay showed lower colonization and were less efficient in the field. The preservation of spontaneous native plants with ornamental value and bioaugmentation of their associated microbiome can contribute to the stabilization of contaminants in soils.

Occurrence, behaviour and environmental risk assessment of trace metals in stream sediments from southwestern Burkina Faso, West Africa.

In this study, the influence of source area weathering and provenance on the stream sediment geochemistry as well as the environmental impacts of selected potentially toxic trace elements (PTE) were evaluated. Four components derived from the R-mode factor analysis of additive logratio-transformed data pointed to the combined influence of weathering of granitoids, sedimentary rocks and greenstone belts and gold mineralisation on the stream geochemistry. Although 13 PTE were enriched in the majority of the samples, only five elements (As, Cr, Cu, Pb and Ni) were likely to have adverse biological effects. Based on the geochemical maps, the areas susceptible to produce adverse biological effects due to As enrichments are solely drained by the greenstone belts, whereas enrichment of Pb was pronounced in areas of high population densities. The linear regression between enrichment factor (EF) and adverse effect indices (AEI) indicated that in order for Pb to pose threats to the benthic organisms, EF should be 4.5, whereas EF for sediment toxicity are 1 for Cu, Cr and Ni and 2 for As. Consequently, Cu, Cr, Ni, As and, to a lesser degree, Pb pose serious environmental threats to benthic organisms in southwestern Burkina Faso. The stream sediment geochemical data of this study constitute a baseline for assessing future environmental risks.

The relationship between properties of plant-based biochars and sorption of Cd(II), Pb(II) and Zn(II) in soil model systems

Plant based biochars are proposed as soil amendments to immobilize potentially toxic trace elements (PTEs), such as Cd(II), Pb(II) and Zn(II) and aid in soil restoration. However, the sorption capacity of biochar for these elements can vary widely depending on biochar nature and metal properties. Currently, there is no clear methodology to pre-screen biochars for their suitability as adsorbents for these elements. Therefore, to facilitate biochar selection for application in soil restoration, this study explored the relationships between the physico-chemical properties of five plant-based biochars and their capacity to immobilize Cd(II), Pb(II) and Zn(II). Batch experiments using synthetic soil pore water were used to assess the sorption of these elements. The sorption isotherms described by the Hill model indicated that PTE sorption capacity followed the order Pb(II) > Cd(II) >Zn(II) regardless of biochar type in mono-element systems. Preferential sorption of Pb(II) limited the immobilization of Cd(II) and Zn(II) in multi-element systems. ATR-FTIR and SEM-EDX spectroscopy studies indicated that Cd(II) and Pb(II) sorption was mediated by complexation with carboxylic groups, cation–π interactions and precipitation with phosphates and silicates, while Zn(II) sorption occurred mainly by complexation with phenolic groups and precipitation with phosphates. A high correlation (>0.8) between Electrical Conductivity, Cation Exchange Capacity, pH and sorption capacity was identified for all metals tested, highlighting the electrostatic nature of the sorption mechanisms involved. Biochars derived from herbaceous feedstock were better candidates for remediation of soil polluted with Cd(II), Pb(II) and Zn(II), rather than wood-derived biochar. Overall, this study provides evidence of the direct relationship between specific properties of plant-based biochars (pH and EC) and their suitability as adsorbents for some PTEs in soil systems.

Impact of Biochar on Release Kinetics of Pb (II) and Zn (II) in a Calcareous Soil Polluted with Mining Activities

Release kinetics governs the detachment and migration of potentially toxic trace elements (PTEs) over time between the solid phase and soil solutions. The assessment of PTEs’ release behavior through time supports more accurate prediction models of toxicity in highly polluted soils. Recently, biochar, a charcoal black carbon ameliorant, was extensively applied for decreasing the release of Zn and Pb to the soil solution. This study was arranged during a short-term (45 days) incubation experiment to estimate the possible effects of walnut leaves (WL) and their biochars produced at three temperatures (200 (B200), 400 (B400), and 600 (B600) °C) on the kinetics of Zn and Pb release in a naturally calcareous and highly polluted soil. Results showed that the biochars could reduce the release of Zn and Pb to the soil solution. The rate of Zn release (“b” in power function) at different biochar levels was 0.35 (2% B600)–0.38 (control) (mg kg−1)−1, respectively; also, the release of Pb was 0.23 (2% B600)–0.33 (control) (mg kg−1)−1, respectively. The results illustrated that a lower concentration of these metals was associated with exchangeable and oxides of Fe-Mn, whereas the higher content of residual fractions of Zn and Pb reduced the release of Zn and Pb in soils treated with biochar. Overall, the more the level and temperature of biochar increased, stabilizing PTEs through changing the distribution of metals in the soil, the more biochars succeeded significantly in lessening the release of PTEs, which ultimately could retard the further toxicity in the soil solution.

Trace elements adsorption by natural and chemically modified humic acids.

Humic substances with or without chemical modification can serve as environmentally benign and inexpensive adsorbents of potentially toxic trace elements (PTTEs) in the environment. The present study investigated the absorption of Pb, Zn, Cu and Ni by natural and potassium persulfate (K2S2O8) modified humic acids (HAs) isolated from a lowland peat through batch experiments. The adsorption of the studied PTTEs on the natural HA was satisfactorily described by the Langmuir isotherm model with maximum monolayer adsorption capacities of 318.2, 286.5, 225.0 and 136.8mmol/kg for Pb, Cu, Zn and Ni, respectively. A thorough characterization of the natural and modified HA using 13C nuclear magnetic resonance spectroscopy demonstrated that the chemical modification of natural HA with K2S2O8 led to an increase in the content of carboxyl groups, and ketone and quinoid fragments in the HA structure. Consequently, the modified HA absorbed 16.3, 14.2, 10.6 and 6.9% more Pb, Ni, Zn and Cu, respectively, than the original natural HA. The isotherm data modeling together with adsorbent characterization suggested that the adsorption of PTTEs was controlled mainly by chemisorption mechanisms where inner-sphere complexations of metal ions with HA functional groups took place.

Soil, Site, and Management Factors Affecting Cadmium Concentrations in Cacao-Growing Soils

Soil contamination by potentially toxic trace elements (PTEs) such as Cadmium (Cd), is a major environmental concern because of its potential implications to human health. Cacao-based products have been identified as food sources with relatively high Cd contents. Here, we assessed Cd concentrations of cacao-growing soils in four major agricultural regions with contrasting climates in Peru, one of the main exporters of cacao products worldwide. At each study site (n = 40) a broad range of potential factors affecting Cd concentration in soils, i.e., site, soil and management, were evaluated. Concentrations of Cd ranged between 1.1–3.2 mg kg−1. Mean values per region were below 2.7 mg kg−1, usually established as upper-limit for non-polluted soils. Cadmium concentrations were significantly (p &lt; 0.001) higher in sites at higher elevations and in a temperate, drier climate. Cadmium correlated positively with pH (r = 0.57; p &lt; 0.05) and was higher (p &lt; 0.001) in alluvial sediments and Leptosols. Management factors (cacao variety, cultivation year, management practices) and agroecology did not affect Cd concentrations directly. Overall, this study highlights the importance of considering a broad range of both natural and anthropogenic factors to evaluate Cd concentrations in cacao-growing soils and contribute to effective and sustainable cacao production by improving land management and planning.

Identifying the sources and spatial patterns of potentially toxic trace elements (PTEs) in Shanghai suburb soils using global and local regression models

Destructive development of suburban areas in some metropolises has exposed suburban soils to high risk of potentially toxic trace elements (PTEs) enrichment, which also threatens human and ecosystem health. This study investigated the pollution status, sources and spatial patterns of four PTEs (Pb, Cd, Cr and As) in 1805 soil samples collected from the suburbs of Shanghai in 2015. Nineteen potential sources, including: 6 soil property factors, 10 proximity factors and 3 topography factors, were selected to help explain the PTEs aggregation using logistic regression models from global and local perspectives. The statistical results of PTEs concentration revealed that Cd showed the highest pollution risk in local soils, which was followed by As. Soil property was the primary factor affecting the PTEs (except Cr) enrichment, both identified by global models and local models. The local model particularly emphasized the significant correlation between soil property and PTEs in most parts of the outer suburbs and southeastern inner suburbs. Some proximity factors such as distance to district center and water were negatively correlated with Cd pollution and some topography factors such as elevation and slope were closely related to As pollution. It is worth noting that in the coastal areas, especially Chongming Island, there were obvious PTEs depositions in the soil near the estuary. This study helps to identify the sources of anthropogenic contamination and geogenic enrichment of the four PTEs and their spatial patterns, playing an essential role in formulating regional environmental policies for coastal cities.

Trace Elements in Leaf Extracts of Eucalyptus grandis Traditionally Used to Treat Common Cold and Flu.

Background.Eucalyptus species have been used for the remediation of mine tailings dams in Zimbabwe. However, a traditional medicinal remedy (TMR) for the treatment of mild acute respiratory infections, such as common cold and flu includes the use of Eucalyptus leaves.Objectives.The aim of the present study was to determine total concentrations of selected potentially toxic trace elements (PTEs) in gold mine tailings and leaves of Eucalyptus grandis and to identify extractable fractions of PTEs in leaves via boiling for 10 minutes in water, which is the process used to create TMRs to treat common cold and flu.Methods.Mine tailings and leaves of E. grandis were randomly collected at a gold mine tailings dam between April and June 2019. They were digested for laboratory analysis using standard analytical methods. Leaves were boiled in water for 10 minutes to prepare the TMR as practiced by the local community. The concentrations of PTEs were determined spectrometrically. Significant differences between PTEs in young and mature leaves were determined by analysis of variance.Results.Mine tailings were acidic (pH 4.52±0.62) with very low content of organic matter (0.02%) and contained PTEs in increasing concentrations of cadmium (Cd) < nickel (Ni) < lead (Pb) < chromium (Cr) < copper (Cu) < zinc (Zn) (n = 27). Mature leaves of E. grandis had higher concentrations than young leaves for Cr, Pb and Zn (p <0.05) which were lower than permissible limits in medicinal plants. Overall, boiling leaves in water for 10 minutes resulted in low extraction of PTEs (< 20%).Participant Consent.ObtainedConclusions.Concentrations of PTEs in leaves and leaf extracts of E. grandis were very low. However, TMRs should not be prepared from medicinal plants growing on metalliferous environments, such as mine tailings dams, due to the presence of cumulative toxins such as Cd and Pb. Further studies are needed to investigate the effect of various boiling times and should include arsenic in the studied PTEs.Competing Interests.The authors declare no competing interests for this study.

Temporal-spatial trends in potentially toxic trace element pollution in farmland soil in the major grain-producing regions of China

Pollution from potentially toxic trace elements (PTEs) is becoming serious and widespread in farmland soils in China, threatening food security and human health. Few large-scale studies systematically analyzed their temporal-spatial trends over vast spatially elaborate sites. The soil health status of the main grain producing areas was first announced based on a total of 3662 spatially elaborate farmland topsoil sites from the 1980s to the 2000s. Nearly 21.5% of sites were polluted, although only slightly. Pollution from the Cd, Ni, Cu, Zn, and Hg was more serious. Pollution was more extensive in the south than in the north. There was an increasing trend in the PTE concentrations, especially Cd with a growth of 21–25%, and in the proportion of mixed pollution at the sites (19.3%), Cd (21.5%), Pb (3.6%), Zn (5.7%), Cu (7.0%), and Hg (3.1%). Furthermore, temporal variations in severe Cd pollution and mixed-level Hg pollution in the north are severer. This study may provide guidance for policymakers regarding the protection and high-risk area of PTE contamination in the soils.

Assessment of Lead (Pb) and Zinc (Zn) Contamination in Beach Sands by Hot Spot Analysis

Kim, S.-M. and Choi, Y., 2019. Assessment of Lead (Pb) and Zinc (Zn) contamination in beach sands by hot spot analysis. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 321-325. Coconut Creek (Florida), ISSN 0749-0208.It is necessary to investigate contamination in beach sands for water safety because replenishing sand on eroding beaches may contain potentially toxic trace elements (PTEs). In order to understand the spatial variation and risk of PTEs in beach sands, this study uses hot spot analysis, which calculates a z-score based on the Getis–Ord Gi* statistic to identify a statistically significant hot spot sample. A high-value data sample surrounded by other high-value samples indicates a statistically significant hot spot. Using relatively cost- and time-effective portable X-ray fluorescence (PXRF) analysis, sand data are acquired from the OO beach on the eastern coast of Korea and used for hot spot analysis. The sand data of the OO beach are classified into four groups: high content with a high z-score (HH), high content with a low z-score (HL), low content with a high z-score (LH), and low content with a low z-score (LL). The HH case can be a critical hazard to human health, whereas the other cases may be insignificant. As a result, it was confirmed that Pb is mainly distributed in the northwestern and southeastern parts, and Zn is distributed in the southern part. However, all the PTE concentrations in the sample data do not exceed the soil contamination warning standards. Although Pb and Zn was detected from some samples, it was not critical from the PXRF and hot spot analysis results. The method implemented in this study may be utilized for the assessment of statistically significant contamination in beach sands.

Adsorption Characteristics of Zn2+ Ions onto Different Aggregate Size Fractions of Some Calcareous Soils and their Relationship with Soil Properties

Soils are exposed to potentially toxic trace elements (PTEs) such as zinc (Zn) through various ways. Adsorption of Zn in soils is one of factors affecting its availability and mobility. Soil aggregates are units of soil structure very important for adsorbing and retaining of PTEs. In this study, characteristics of the adsorption of Zn were studied in the aggregates of five calcareous soils. Soil aggregates were separated using the dry sieving into four size fractions: 4 to 2 and 2 to 0.25 mm (macroaggregates) and 0.25 to 0.053 and <0.053 mm (microaggregates). Then, adsorption of Zn was studied in different aggregate size fractions using an electrolyte solution calcium chloride (10 mM) containing Zn. Also, properties, such as pH, cation exchange capacity (CEC), calcium carbonate equivalent (CCE), free iron oxides, organic carbon, and amounts of total and available of Zn were determined in different aggregate size fractions. Results showed both the Langmuir and Freundlich equations are applicable to describe the adsorption of Zn in various aggregates. Adsorption capacity (qm in Langmuir model), distribution coefficient (KF in Freundlich model), and adsorption rate (n in Freundlich model) of the Zn in the microaggregates were higher than in the macroaggregates. At the same time, adsorption energy (KL in Langmuir model) and, therefore, maximum buffering capacity (MBC in Langmuir model) in the microaggregates were lower than in the macroaggregates. Thus, the amount and rate of Zn adsorption in the microaggregates was higher than in the macroaggregates, but it retained with lower energy. The results of regression study indicated that CEC and CCE are the most effective soil properties on the coefficients of adsorption isotherms. The results of this study revealed that the microaggregates (<0.25 mm) have a higher potential to contaminate the environment in comparison with the macroaggregates.

Use of Bacteria and Synthetic Zeolites in Remediation of Soil and Water Polluted with Superhigh-Organic-Sulfur Raša Coal (Raša Bay, North Adriatic, Croatia)

The Raša Bay (North Adriatic, Croatia) has been receiving various pollutants by inflowing streams laden with untreated municipal and coalmine effluents for decades. The locality was a regional center of coalmining (Raša coal), coal combustion, and metal processing industries for more than two centuries. As local soil and stream water were found to be contaminated with sulfur and potentially toxic trace elements (PTEs) as a consequence of weathering of Raša coal and its waste, some clean-up measures are highly required. Therefore, the aim of this study was to test the remediating potential of selected microorganisms and synthetic zeolites in the case of soil and coal-mine water, respectively, for the first time. By employing bacterial cultures of Ralstonia sp., we examined removal of sulfur and selected PTEs (As, Ba, Co, Cr, Cu, Ni, Pb, Rb, Se, Sr, U, V, and Zn) from soil. The removal of sulfur was up to 60%, arsenic up to 80%, while Se, Ba, and V up to 60%, and U up to 20%. By applying synthetic zeolites on water from the Raša coalmine and a local stream, the significant removal values were found for Sr (up to 99.9%) and Ba (up to 99.2%) only. Removal values were quite irregular (insignificant) in the cases of Fe, Ni, Zn, and Se, which were up to 80%, 50%, 30%, and 20%, respectively. Although promising, the results call for further research on this topic.

The Transfer Characteristics of Potentially Toxic Trace Elements in Different Soil-Rice Systems and Their Quantitative Models in Southeastern China.

The potentially toxic trace elements (PTEs) transfer characteristics in the soil-rice system plays an important role in soil quality management, and it can be used to guide the safe rice production. We collected soil and rice samples from three typical rice production areas (Nanxun, Shengzhou, Wenling in northern, central, and southern parts of Zhejiang Province, China). The controlling factors of PTEs′ transfer were studied for Hybrid rice and Japonica rice. The results indicated that the pH, organic matter (OM), and electrical conductivity (EC) values of Shengzhou were all lower than that of the other two production areas (Nanxun and Wenling). The concentrations of PTEs in the soils of Wenling were significantly higher than that in the other two areas, while the concentrations of PTEs in the rice of Shengzhou were significantly higher than that of Wenling and Nanxun (p < 0.05). The enrichment index (EI) of PTEs were also different in the three production areas. The EIs of Cd and Zn were higher than that of Cu and Ni in the three production areas, and the EIs in Shengzhou were significantly higher than that of other two areas (p < 0.05). The soil physico-chemical properties and PTEs’ fractions both played important roles in PTEs transfer in the soil-rice system. The log-linear model of EI for PTEs can predict the availability of PTEs in the soil-rice system under practical production areas. The accuracy of the model prediction of EI for Japonica rice was better than that for the Hybrid rice. The prediction model of Ni was better than that of other PTEs for both rices.

Contamination and health risk assessment of trace elements in soil at play centers of urban low-income settings

Young children are considered critical receptors of potentially toxic trace elements (PTEs) by non-dietary ingestion of contaminated soil. The study assessed the potential enrichment of soil and the health risk of PTEs to 471 children less than seven years via non-dietary soil ingestion at six Early Childhood Development Centers (ECDCs) in urban low-income settings. The total concentrations of PTEs were determined by ICP-AES after wet acid digestion. The extent of soil contamination with PTEs and their source apportionment were assessed by the enrichment factor (EF). The US-EPA risk assessment model was used to determine the risk of PTE exposure by children. Multivariate statistical analyses and the EF suggested anthropogenic origin of PTEs in playgrounds and indoors, especially Cd and Pb from atmospheric deposition. Indoor floor dust at ECDCs was enriched (significant to extreme) with PTEs of anthropogenic origin imported from the outside environment. Children at the six ECDCs were not at significant non-carcinogenic risk of PTEs in soil and dust through non-dietary ingestion. The study setting is typical of urban child play centers in low-income countries which needs regular risk assessment and the enforcement of legislation in order to reduce the exposure of children to PTEs.

Remediation potential of immobilized bacterial consortium with biochar as carrier in pyrene-Cr(VI) co-contaminated soil

ABSTRACTPolycyclic aromatic hydrocarbons (PAHs) and potentially toxic trace elements (PTEs) soil contamination have become areas of concern. Bioaugmentation is regarded as an effective bioremediation method, however it is difficult to simultaneously degrade organic compounds and remove PTEs with individual microbial strains. Therefore, the objective of this study was to evaluate the feasibility of using immobilized microbial consortia, including two PAH-degrading bacterial strains (W1 and W2) and a Cr(VI)-reducing bacterium (Y2), for the remediation of pyrene-Cr(VI) co-contaminated soil. Three immobilization methods were investigated: (1) bacterial consortium adsorption onto biochar (BC), (2) bacterial consortium entrapment in alginate beads (AC), (3) bacterial consortium adsorption on biochar and sequential entrapment in alginate beads (BAC). In addition, a free bacterial consortium (FC) was also used for comparison. Ten treatments were designed to illustrate the bioremediation efficiency of the free and immobilized consortia. The results show that treatments AC and BAC resulted in more efficient Cr(VI) removal compared with BC and FC. Pyrene levels in AC and BAC microcosms were reduced from 42.33 ± 3.82 to 11.56 ± 1.37 and 7.48 ± 0.39 mg kg−1, respectively. Bioavailable Cr (VI) in AC and BAC was significantly lower than that in other microcosms after 28 days’ incubation. Both AC and BAC microcosms exhibited a higher level of dehydrogenase and fluorescein diacetate hydrolysis activity. Furthermore, soil microbial diversity was higher in AC and BAC microcosms compared with the others. Thus, the entrapped consortia may be useful for bioremediation of pyrene and Cr (VI) without compromising soil ecology.