The importance of solid-phase distribution on the oral bioaccessibility of Ni and Cr in soils overlying Palaeogene basalt lavas, Northern Ireland

Potentially toxic elements (PTEs) including nickel and chromium are often present in soils overlying basalt at concentrations above regulatory guidance values due to the presence of these elements in underlying geology. Oral bioaccessibility testing allows the risk posed by PTEs to human health to be assessed; however, bioaccessibility is controlled by factors including mineralogy, particle size, solid-phase speciation and encapsulation. X-ray diffraction was used to characterise the mineralogy of 12 soil samples overlying Palaeogene basalt lavas in Northern Ireland, and non-specific sequential extraction coupled with chemometric analysis was used to determine the distribution of elements amongst soil components in 3 of these samples. The data obtained were related to total concentration and oral bioaccessible concentration to determine whether a relationship exists between the overall concentrations of PTEs, their bioaccessibility and the soils mineralogy and geochemistry. Gastric phase bioaccessible fraction (BAF %) ranged from 0.4 to 5.4 % for chromium in soils overlying basalt and bioaccessible and total chromium concentrations are positively correlated. In contrast, the range of gastric phase BAF for nickel was greater (1.4–43.8 %), while no significant correlation was observed between bioaccessible and total nickel concentrations. However, nickel BAF was inversely correlated with total concentration. Solid-phase fractionation information showed that bioaccessible nickel was associated with calcium carbonate, aluminium oxide, iron oxide and clay-related components, while bioaccessible chromium was associated with clay-related components. This suggests that weathering significantly affects nickel bioaccessibility, but does not have the same effect on the bioaccessibility of chromium.     

Correction to: Biosolids application affects the competitive sorption and lability of cadmium,copper, nickel,lead, and zinc in fluvial and calcareous soils

Environmental Geochemistry and Health - Unfortunately, in the original publication of the article, Prof. Yong Sik Ok’s affiliation was incorrectly published.     

Biosolids application affects the competitive sorption and lability of cadmium,copper, nickel,lead, and zinc in fluvial and calcareous soils

The objective of this research was to investigate the effects of biosolids on the competitive sorption and lability of the sorbed Cd, Cu, Ni, Pb, and Zn in fluvial and calcareous soils. Competitive sorption isotherms were developed, and the lability of these metals was estimated by DTPA extraction following their sorption. Sorption of all metals was higher in the fluvial than in the calcareous soil. Sorption of Cu and Pb was stronger than that of Cd, Ni, and Zn in all soils. Biosolids application (2.5%) reduced the sorption of all metals especially Cu and Pb (28–43%) in both soils (especially the calcareous soil) at the lower added metal concentrations (50 and 100 mg L^?1). However, it increased the sorption of all metals especially Pb and Cu in both soils (especially the calcareous soil; 15.5-fold for Cu) at the higher added concentrations (250 and 300 mg L^?1). Nickel showed the highest lability followed by Cd, Zn, and Pb in both soils. Biosolids increased the lability of the sorbed Ni in the fluvial soils at all added concentrations and the lability of Cd, Pb, and Zn at 50 mg L^?1, but decreased the lability of Cd, Pb, and Zn at 250 and 300 mg L^?1 in both soils. We conclude that at low loading rate (e.g., 50 mg L^?1) biosolids treatment might increase the lability and environmental risk of Cd, Cu, Pb, and Zn. However, at high loading rate (e.g., 300 mg L^?1) biosolids may be used as an immobilizing agent for Cd, Cu, Pb, Zn and mobilizing agent for Ni.     

Geochemistry,mineralogy, solid-phase fractionation and oral bioaccessibility of lead in urban soils of Lisbon

An urban survey of Lisbon, the largest city in Portugal, was carried out to investigate its environmental burden, emphasizing metallic elements and their public health impacts. This paper examines the geochemistry of lead (Pb) and its influence on human health data. A total of 51 soil samples were collected from urban recreational areas used by children to play outdoors. The semi-quantitative analysis of Pb was carried out by inductively coupled plasma mass spectrometry after an acid digestion. X-ray diffraction was used to characterize the soil mineralogy. The solid-phase distribution of Pb in the urban soils was investigated on a subset of 7 soils, out of a total of 51 samples, using a non-specific sequential extraction method coupled with chemometric analysis. Oral bioaccessibility measurements were obtained using the Unified BARGE Method developed by the Bioaccessibility Research Group of Europe. The objectives of the study are as follows: (1) investigation of Pb solid-phase distribution; (2) interpretation of Pb oral bioaccessibility measurements; (3) integration of metal geochemistry with human health data; and (4) understanding the influence of geochemistry and mineralogy on oral bioaccessibility. The results show that the bioaccessible fraction of Pb is lower when major metal fractions are associated with less soluble soil phases such as Fe oxyhydroxides, and more increased when the metal is in the highly soluble carbonate phase. However, there is some evidence that the proportion of carbonates in the soil environment is also a key control over the oral bioaccessibility of Pb, irrespective of its solid-phase fractionation.     

Evaluating the respiratory bioaccessibility of nickel in soil through the use of a simulated lung fluid

Simulated lung fluids are solutions designed to mimic the composition of human interstitial lung fluid as closely as possible. Analysis of mineral dusts using such solutions has been used to evaluate the respiratory bioaccessibility of various elements for which solubility in the lungs is a primary determinant of reactivity. The objective of this study was to employ simulated lung fluid analysis to investigate the respiratory bioaccessibility of nickel in soils. Current occupational guidelines in Australia regulate nickel compounds in terms of water solubility, though this may not be an accurate estimation of the total nickel that will dissociate in the lungs. Surface soils were collected from the city of Kalgoorlie in Western Australia, the site of an operational nickel smelter and metal mining activities. The fraction of the samples less than 10 μm was extracted from the soil, and it was this sub-10-μm fraction that was found to hold most of the total nickel present in the soil. The fine fraction was analyzed using a simulated lung fluid (modified Gamble’s solution) to isolate the nickel phases soluble in the lungs. In addition, a sequential extraction was employed to compare the bioaccessible fraction to those dissolved from different binding forms in the soil. In all samples, the simulated lung fluid extracted more nickel than the two weakest leaches of the sequential extraction combined, providing a more representative nickel bioaccessibility value than the current water leach method.     

污染土壤中铅、砷的生物可给性研究进展

土壤铅、砷污染已成为重要的环境问题,并可对人体健康造成严重危害。对食物链途径的有效控制使得从口部无意摄入的土壤铅、砷对人体,特别是对儿童铅、砷摄入总量的贡献率越来越大,甚至成为主要来源。土壤中铅、砷直接进入人体的消化系统并可被人体胃肠道溶解出的部分称为其生物可给性。有效、准确地判定土壤中铅、砷的生物可给性已经成为解决儿童铅、砷中毒的关键科学问题。因此,有关土壤中铅、砷的生物可给性及其在人体健康风险评价中的应用受到了越来越多的关注。文章综述了污染土壤中铅、砷生物可给性的研究方法及各方法的优缺点,并从土壤性质、模拟胃肠条件等方面分析了影响土壤中铅、砷生物可给性的主要因素和存在的问题,还进一步论述了土壤中铅、砷生物可给性在人体健康风险评价中的应用。最后,提出了今后该领域应重点加强土壤铅、砷生物可给性的标准参考物、模拟胃肠条件的优化以及土壤铅、砷生物可给性在人体健康风险评价中的应用等方面的研究。以期充分发挥铅、砷等环境污染物的生物可给性研究方法的潜力,更好地为控制土壤污染、保护人类健康服务。     

Human bioaccessibility of Cr, Cu, Ni, Pb and Zn in urban soils from the city of Torino, Italy

Several physiologically based extraction procedures have been proposed to estimate the fraction of the potentially toxic element content that would be bioaccessible in the human gastro-intestinal tract following accidental ingestion of soil. Many of these procedures are complex, they have been applied to a very limited range of soils, and most work has focussed on arsenic and lead. In the present study, a simplified, two-stage extraction, simulating the human stomach and intestine, was developed and applied to urban soil samples from ten public-access areas in the City of Torino, Italy. The human oral bioaccessibility of chromium, copper, nickel, lead and zinc was estimated. Lead and zinc bioaccessibilities were found to be higher in the stomach, but chromium was more bioaccessible in the intestine. Analyte concentrations were higher in roadside soils than in soils from parks. A higher proportion of the soil metal content was found in bioaccessible forms at roadsides than in parks. Comparison of the current findings with results of earlier work involving sequential extraction of the same soils indicated that the sequential procedure gave a relative, but not an absolute, indication of bioaccessibility. Calculations based on the bioaccessible analyte concentrations suggest that ingestion of only 2–3 g of some of the roadside soil samples from Torino could deliver the tolerable daily oral intake of chromium, nickel and lead to a 20-kg child. The developed procedure is useful for preliminary screening of soils and prediction of whether their bioaccessible metal contents are likely to pose a risk to human health.     

Use of a physiologically based extraction test to estimate the human bioaccessibility of potentially toxic elements in urban soils from the city of Glasgow,UK

A simple, two-stage, physiologically based extraction has been applied to assess the human bioaccessibility of potentially toxic elements (PTE) in 20 urban soils from a major UK city. Chromium and iron bioaccessibilities were found to be markedly higher in the intestinal phase, whilst lead and zinc bioaccessibilities were higher in the stomach. Copper and manganese bioaccessibilities were generally similar under both extraction conditions. Principal component analysis was used to study relationships amongst bioaccessible element concentrations and land use. Distinctions could be observed between the distributions of the urban metals—copper, lead and zinc—and metals predominantly of geogenic origin, such as iron. There was no clear delineation between roadside soils and soils obtained from public parks. Bioaccessible analyte concentrations were found to be correlated with pseudototal (aqua regia soluble) analyte concentrations for all elements except iron. Results of the BCR sequential extraction did not, in general, provide a good indication of human bioaccessibility. Comparison of bioaccessible PTE concentrations with toxicological data indicated that lead is the element of greatest concern in these soils but that levels are unlikely to pose a health risk to children with average soil intake.     

Assessment of bioaccessibility and exposure risk of arsenic and lead in urban soils of Guangzhou City,China

Soil ingestion is an important human exposure pathway of heavy metals in urban environments with heavy metal contaminated soils. This study aims to assess potential health risks of heavy metals in soils sampled from an urban environment where high frequency of human exposure may be present. A bioaccessibility test is used, which is an in vitro gastrointestinal (IVG) test of soluble metals under simulated physiological conditions of the human digestion system. Soil samples for assessing the oral bioaccessibility of arsenic (As) and lead (Pb) were collected from a diverse range of different land uses, including urban parks, roadsides, industrial sites and residential areas in Guangzhou City, China. The soil samples contained a wide range of total As (10.2 to 61.0 mg kg⁻¹) and Pb (38.4 to 348 mg kg⁻¹) concentrations. The bioaccessibility of As and Pb in the soil samples were 11.3 and 39.1% in the stomach phase, and 1.9 and 6.9% in the intestinal phase, respectively. The As and Pb bioaccessibility in the small intestinal phase was significantly lower than those in the gastric phase. Arsenic bioaccessibility was closely influenced by soil pH and organic matter content (r ² = 0.451, p < 0.01) in the stomach phase, and by organic matter, silt and total As contents (r ² = 0.604, p < 0.001) in the intestinal phase. The general risk of As and Pb intake for children from incidental ingestion of soils is low, compared to their maximum doses, without causing negative human health effects. The exposure risk of Pb in the soils ranked in the order of: industrial area/urban parks > residential area/road side. Although the risk of heavy metal exposure from direct ingestion of urban soils is relatively low, the risk of inhalation of fine soil particulates in the air remains to be evaluated.     

Function analysis as a coastal management tool: the South Wales coastline,UK

Fifteen beaches from the Swansea Bay coastal sediment cell, South Wales, UK, were analysed via function analysis, involving assessment of specific environmental and socio-economic indicators. These were allocated scores from field surveys and extensive desktop studies, which included beach awards, relevant shoreline management plans, planning and conservation designations and current legislation. Normalised scores allowed production of a conservation/development matrix, enabling beach location in conservation, development or conflict fields, which results appropriately identified. Conservation field beaches tended to have a low density residential hinterland with little or no commercialisation. Conversely, beaches that leant towards the development field had a high density residential hinterland and were highly commercialised. Evaluation showed the importance of planning legislation in conflict areas and identified locations of development potential, where significant environmental consequences would be unlikely. This representation could be used for evolution of conservation/development status within coastal areas, enabling policy adjustment as necessary. It will also enable future sustainability assessment and it is suggested that indicators could be modified to reduce environmental emphasis and provide a more uniform socio-economic consideration.     

Biosorption of copper, zinc, cadmium and nickel by Chlorella vulgaris

The sorption capacity of the microalga, Chlorella vulgaris, was investigated using different metals (Cu, Zn, Cd and Ni), in both monometallic and bimetallic solutions. The final metal concentrations were significantly low. In the case of copper, an acid pretreatment (at pH 3) of the biomass was required to avoid an excessive increase in pH and the subsequent precipitation of metal during tests. This pretreatment was not necessary for the rest of the metals. The study of the influence of pH led to a greater metal uptake at a higher pH, suggesting a clear competition between metal cations and protons during the biosorption process. The biomass concentration was also a relevant variable, and the best sorption capacities were achieved at the lowest biomass concentration. pH also had a great influence on the elution of the metal retained by the biomass. The best recovery yields were obtained for the lower pH of the eluent solution. Sorption isotherms were well fitted to the Langmuir model, for both single-metal and two-metal systems. In both cases, the biomass showed a greater affinity for Cd.     

A conceptual snapsot of a big coastal dune aquifer: Magilligan,Northern Ireland

The Magilligan sand spit dune field is situated on the eastern mouth of Lough Foyle in County Londonderry, Northern Ireland. It is a large triangular-shaped site some 7 km by 4 km by 1.5 km wide (about 800 ha) and maintains areas, particularly in the eastern part, with slacks that regularly flood in winter. The size of the system acts as a buffer to external drivers due to the large volume of groundwater stored, the longer travel distances and lower hydraulic gradients. However, unlike many other coastal dune sites with humid dune slacks in the British Isles the sand is not wholly underlain by silt and clay, as raised beach sand and gravel deposits are in contact with the sand aquifer in some places. A preliminary water balance suggests that the majority of the discharge from the sand aquifer occurs via the underlying raised beach deposits and only a small amount discharges directly from the sand aquifer beneath the foredunes. Available water level monitoring is skewed towards the wetter end of the dune system; no significant short-term water level trends are apparent. The data also indicate that recharge regularly takes place within the sand aquifer interspersed by periods of groundwater level recession.     

Use of trace element analysis of feathers as a tool to track fine-scale dispersal in birds

Tracking dispersal and migratory movements of animals over small and large spatial scales is a challenge. In birds, a promising yet underutilized tool is the trace elemental composition of feathers. The elemental profile of a feather may reveal information about the geographic origin of a bird provided that molting occurs on the breeding grounds and that elemental differences exist between breeding areas. Here, we explore the use of trace elemental composition in body feathers of the Puget Sound white-crowned sparrow Zonotrichia leucophrys pugetensis as a tool (1) to discriminate among birds collected in four different song dialect populations along a 400-km stretch of the Pacific Northwest coast and (2) to assign males singing nonlocal dialects in one population to potential natal populations. Inductively coupled plasma mass spectrometry detected 34 trace elements in sampled feathers and in a discriminant function analysis seven of these elements differed among the four source populations. Half of the six nonlocal dialect singers, who were likely to have immigrated into the focal population, were assigned to a population that matched their song dialect. Our study suggests that feather microchemistry is a promising tool for identifying geographic origins of dispersing birds over small geographic scales and in combination with other markers, such as song, may give insight into ecological and evolutionary processes.     

Gypsum addition to soils contaminated by red mud: implications for aluminium, arsenic, molybdenum and vanadium solubility

Red mud is highly alkaline (pH 13), saline and can contain elevated concentrations of several potentially toxic elements (e.g. Al, As, Mo and V). Release of up to 1 million m³ of bauxite residue (red mud) suspension from the Ajka repository, western Hungary, caused large-scale contamination of downstream rivers and floodplains. There is now concern about the potential leaching of toxic metal(loid)s from the red mud as some have enhanced solubility at high pH. This study investigated the impact of red mud addition to three different Hungarian soils with respect to trace element solubility and soil geochemistry. The effectiveness of gypsum amendment for the rehabilitation of red mud-contaminated soils was also examined. Red mud addition to soils caused a pH increase, proportional to red mud addition, of up to 4 pH units (e.g. pH 7 → 11). Increasing red mud addition also led to significant increases in salinity, dissolved organic carbon and aqueous trace element concentrations. However, the response was highly soil specific and one of the soils tested buffered pH to around pH 8.5 even with the highest red mud loading tested (33 % w/w); experiments using this soil also had much lower aqueous Al, As and V concentrations. Gypsum addition to soil/red mud mixtures, even at relatively low concentrations (1 % w/w), was sufficient to buffer experimental pH to 7.5–8.5. This effect was attributed to the reaction of Ca²⁺ supplied by the gypsum with OH^? and carbonate from the red mud to precipitate calcite. The lowered pH enhanced trace element sorption and largely inhibited the release of Al, As and V. Mo concentrations, however, were largely unaffected by gypsum induced pH buffering due to the greater solubility of Mo (as molybdate) at circumneutral pH. Gypsum addition also leads to significantly higher porewater salinities, and column experiments demonstrated that this increase in total dissolved solids persisted even after 25 pore volume replacements. Gypsum addition could therefore provide a cheaper alternative to recovery (dig and dump) for the treatment of red mud-affected soils. The observed inhibition of trace metal release within red mud-affected soils was relatively insensitive to either the percentage of red mud or gypsum present, making the treatment easy to apply. However, there is risk that over-application of gypsum could lead to detrimental long-term increases in soil salinity.     

Spatial distribution of potentially bioavailable metals in surface soils of a contaminated sports ground in Galway, Ireland

Assessing the environmental risk of metal contamination in soils requires the determination of both total (TCs) and bioavailable (BCs) element concentrations. A total of 200 surface (0–10 cm) soil samples were collected from an urban sports ground (South Park) in Galway, Ireland, a former landfill and dumping site, which is currently under remediation. The potential BCs of metals were measured using ethylene-diamine-tetra-acetic acid (EDTA) extraction followed by inductively coupled plasma-optical emission spectrometry analysis, while the TCs were determined using portable X-ray fluorescence spectrometry. It was found that Zn was primarily present in the insoluble residue (EDTA un-extractable) fraction in soils, with the median ratio of BCs/TCs 0.27. However, Pb and Cu had higher ratios of BCs/TCs (median values of 0.60 and 0.39, respectively) suggesting that they are potentially more bioavailable in the soils. The spatial distribution maps showed that both TCs and BCs for Cu, Pb and Zn in the study area were spatially heterogeneous. It was found that the BCs exhibited generally similar spatial patterns as their TCs of Cu, Pb and Zn: high values were mainly located in the west, north-east and south-east portions of the study area, where only a thin layer of topsoil existed. It was recommended that the current remediation action for this site needs to be carried out on an urgent basis.     

Effect of biogeochemical interactions on bioaccessibility of arsenic in soils of a former smelter site in Republic of Korea

The total concentration-based regulations for soil remediation do not consider the possible changes in bioaccessibility of remaining arsenic (As) in soils due to biogeochemical interactions after remediation. This study used As-contaminated soil and pore water samples that were collected from the rice paddy and forest/farmland located in the vicinity of a former smelter site in Republic of Korea to elucidate the changes in As bioaccessibility due to biogeochemical interactions. Bioaccessibility and chemical forms of As in soils were determined by using an in vitro method and sequential extraction, respectively, and soil microbial community was evaluated. Bioaccessibility of As in the rice paddy soil samples was higher than that in the forest/farmland soil samples. This could be attributed to relatively higher dependence of bioaccessible As in the rice paddy soils on the soil concentration of iron (Fe), aluminum, or manganese, which could lead to greater changes in bioaccessible As via reductive dissolution. The strong linear relationship (R ² = 0.90, p value ≤0.001) between the pore water As and Fe concentrations, and the greater portion of bacterial species related to reductive dissolution of Fe oxides in the rice paddies can support the higher As bioaccessibility promoted by reductive dissolution. Therefore, it is necessary to consider the potential changes in the bioaccessible As due to biogeochemical interactions in remediation of As-contaminated soils, particularly when soils are likely to be reused under reductive dissolution-promoting conditions (e.g., flooded conditions).     

Baseline zinc content of soils and plants in Poland

Topsoils from Poland were analysed for total and extractable zinc, and for a range of major elements and selected soil properties. Plant samples from the same locations were also analysed for zinc content. The geometric mean concentrations of zinc in samples were (mg/kg dry weight): soil total-Zn, 45.9; soil extractable-Zn 3.1; grass, 30.0; dandelion-tops, 45.9; dandelion-roots, 23.2; oat-leaves, 20.0; oat-grains, 29.7; lichens, 111.5. Significant relationships were found for zinc in grass and extractable-Zn in soils as well as for zinc in lichens and both total and extractable Zn in soils. Zinc in soils varied for soil kinds and regions.     

Identification and mapping of heavy metal pollution in soils of a sports ground in Galway City,Ireland, using a portable XRF analyser and GIS

Heavy metals in urban soils continue to attract attention because of their potential long-term effects on human health. During a previous investigation of urban soils in Galway City, Ireland, a pollution hotspot of Pb, Cu, Zn and As was identified in the sports ground of South Park in the Claddagh. The sports ground was formerly a rubbish dumping site for both municipal and industrial wastes. In the present study, a portable X-ray fluorescence (PXRF) analyser was used to obtain rapid in-situ elemental analyses of the topsoil (depth: about 5–10 cm) at 200 locations on a 20 × 20-m grid in South Park. Extremely high values of the pollutants were found, with maximum values of Pb, Zn, Cu and As of 10,297, 24,716, 2224 and 744 mg/kg soil, respectively. High values occur particularly where the topsoil cover is thin, whereas lower values were found in areas where imported topsoil covers the polluted substrate. Geographic Information Systems (GIS) techniques were applied to the dataset to create elemental spatial distribution maps, three-dimensional images and interpretive hazard maps of the pollutants in the study area. Immediate action to remediate the contaminated topsoil is recommended to safeguard the health of children who play at the sports ground.     

Phosphate-induced differences in stabilization efficiency for soils contaminated with lead,zinc, and cadmium

Phosphates can cost-effectively decrease the mobility of Pb in contaminated soils. However, Pb always coexists with other metals in soil, their competitive reactions with phosphates have not been tested. In this study, the abilities of KH₂PO₄, K₂HPO₄, and K₃PO₄ to stabilize Pb, Zn, and Cd in soils contaminated with a single metal or a ternary metal for different phosphorus/metal molar ratios were investigated. Results indicated that the stabilization efficiency of KH₂PO₄, K₂HPO₄, and K₃PO₄ for Pb, Zn, and Cd in single metal contaminated soil (P/M ratio 0.6) was 96.00%–98.74%, 33.76%–47.81%, and 9.50%–55.79%, respectively. Competitive stabilization occurred in the ternary system, Pb exhibited a strong competition, the stabilization efficiency of Zn and Cd reduced by 23.50%–31.64%, and 7.10%–39.26%, respectively. Pyromorphite and amorphous lead phosphate formed with excess KH₂PO₄ or K₂HPO₄ addition, while K₃PO₄ resulted in the formation of a hydroxypyromorphite precipitate. Amorphous Zn and Cd phosphates and hydroxides were the primary products. The immobilization rate of Zn and Cd depends on pH, and increased significantly in response to the excess phosphate application. This approach provides insight into phosphate-induced differences in stabilization efficiency in soils contaminated with multiple metals, which is of theoretical and engineering significance.

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