Investigation of trace elements in agricultural soils by BCR sequential extraction method and its transfer to wheat plants

Fractionation of metals in soil for strawberry cultivation: Effect on metal migration in food chain and application in risk assessment

Although trace metals in strawberry production system have attracted growing attention, little is known about metal fractionation in soil for strawberry cultivation. We hypothesized that the metal fractions in soil influenced by strawberry production had significant effect on food chain transport of metals and their risk in soil. Here, samples of strawberries and soil were gathered in the Yangtze River Delta, China to verify the hypothesis. Results showed that the acid-soluble Cr, Cd, and Ni in soil for strawberry cultivation were 21.5%-88.3% higher than those in open field soil, which enhanced uptake and bioaccessible levels of these metals in strawberries. Overall, the ecological, mobility, and health risks of Pb, Zn, Ni, and Cu in soil were at a low level. However, the ecological risk of bioavailable Cd, mobility risk of Cd, and cancer risk of bioavailable Cr in over 70% of the soil samples were at moderate, high, and acceptable levels, respectively. Since the increased acid-soluble Cr and Ni in soil were related to soil acidification induced by strawberry production, nitrogen fertilizer application should be optimized to prevent soil acidification and reduce transfer of Cr and Ni. Additionally, as Cd and organic matter accumulated in soil, the acid-soluble Cd and the ecological and mobility risks of Cd in soil were enhanced. To decrease transfer and risk of Cd in soil, organic fertilizer application should be optimized to mitigate Cd accumulation, alter organic matter composition, and subsequently promote the transformation of bioavailable Cd into residual Cd in soil.

Changes in the extractability and fractionation of cadmium and copper in a contaminated soil amended with various sugarcane bagasse-based materials

Heavy-metal contamination in soil has long been a persistent challenge and the utilization of agricultural waste for in-situ stabilization remediation presents a promising approach to tackle this problem. Agricultural wastes exhibit promising potential in the remediation of contaminated land and modification could improve the adsorption performance markedly. Citric acid and Fe3O4 treated sugarcane bagasse adsorbed more heavy metals than raw materials in the aqueous system, employing these materials for heavy metal remediation in soil holds significant implications for broadening the raw material source of passivators and enhancing waste utilization efficiency. In this paper, a 120-day soil incubation study was conducted to compare the effects of pristine sugarcane bagasse (SB), citric-acid modified (SSB1, SSB2 and SSB3 with increasing proportion of citric acid) and citric-acid/Fe3O4 modified (MSB1, MSB4 and MSB7 with increasing proportion of Fe3O4) sugarcane bagasse at 1 % addition rate on cadmium (Cd) and copper (Cu) passivation. The SB, SSB1 and MSB1 did not always decrease the content of CaCl2-extractable Cd while all the seven amendments decreased the CaCl2-extractable Cu during the experiment period. Among all materials, SSB3 and MSB7 exhibited the highest efficiency in reducing the concentrations of CaCl2-extractable Cd and Cu. At Day 120, SB, SSB3 and MSB7 reduced the content of CaCl2-extractable Cd by 8 %, 18 % and 24 %, and of CaCl2-extractable Cu by 25 %, 50 % and 61 %, respectively. The efficiency of Cd and Cu immobilization was associated positively with the pH, functional groups and H-bonds of the amendments. The results suggest that the efficiency of sugarcane bagasse in heavy-metal passivation can be largely enhanced through chemical modifications using high proportions of citric acid and Fe3O4.

Evidence for the accumulation of toxic metal(loid)s in agricultural soils impacted from long-term application of phosphate fertilizer

Phosphate fertilizers may contain elevated concentrations of toxic metals and metalloids and therefore, their excessive application can result in the accumulation of both phosphorus (P) and metal(loid)s in agricultural soils. This study aims to investigate the occurrence, distribution, and potential plant-availability of metal(loid)s originating from phosphate fertilizer in a long-term experimental field at the Tidewater Research Station in North Carolina, where topsoil (10-20 cm deep) and subsoil (up to 150 cm deep) samples were collected from five plots with consistent and individually different application rates of P-fertilizer since 1966. We conducted systematic analyses of P and metal(loid)s in bulk soils, in the plant available fraction, and in four sequentially extracted soil fractions (exchangeable, reducible, oxidizable, and residual). The results show that P content in topsoils were directly associated with the rate of P-fertilizer application (ρ = 1, p < 0.05). Furthermore, P concentrations were highly correlated with concentrations of Cd, U, Cr, V, and As in the bulk topsoil (ρ > 0.58, p < 0.05), as well as the potential plant-available fraction (ρ > 0.67, p < 0.01), indicating the accumulation of the fertilizer-derived toxic metal(loid)s in the topsoil. Significant correlations (p < 0.001) of metal(loid)s concentrations between the bulk soil and the potential plant-available fraction raises the possibility that P-fertilizer application could increase the accumulation of toxic metal(loid)s in plants, which could increase human exposure. Results from sequential leaching experiments revealed that large portions of the trace elements, in particular Cd, occur in the soluble (exchangeable and reducing) fractions of topsoil with higher P-fertilizer input, whereas the levels of redox-sensitive elements (As, V, U, Cr) were higher in the reducible and oxidizable fractions of the soils. Overall, the data presented in this study demonstrate the effect of long-term P-fertilizer application on the occurrence and accumulation of a wide range of toxic metal(loid)s in agricultural topsoil.

Multi-metals analysis in sediment of the North Sumatra coast, Indonesia: The environmental status

This study aims to analyze multi-metals in marine sediment to provide the relative nature of metal concentrations. Sediment samples were collected in representative coasts of natural and more developing zones. The Sequential Extraction method was used to treat four metal associated hosts determined using the ICP-OES. Geo-accumulation index, Enrichment Factor and Principal Component analysis were used to evaluate. The metal concentrations varied and most of them appeared to show a gradual decrease from east, west to the isle coasts. The coastal environment has been recognized to contain non-residual associated metals suggesting the influence of anthropogenic metal input. These bioavailable fractions also show gradual decrease from the East coast to West and Isle coast. The environmental assessment reveals that most of these areas were categorized as unpolluted and concentration of some elements west and isle coast are relatively close to those of nature sediment.

Effects of microplastics on the phytoremediation of Cd, Pb, and Zn contaminated soils by Solanum photeinocarpum and Lantana camara

Microplastics are emerging pollutants and have become a global environmental issue. The impacts of microplastics on the phytoremediation of heavy metal-contaminated soils are unclear. A pot experiment was conducted to investigate the effects of four additions (0, 0.1%, 0.5%, and 1% w·w-1) of polyethylene (PE) and cadmium (Cd), lead (Pb), and zinc (Zn) contaminated soil on the growth and heavy metal accumulation of two hyperaccumulators (Solanum photeinocarpum and Lantana camara). PE significantly decreased the pH and activities of dehydrogenase and phosphatase in soil, while it increased the bioavailability of Cd and Pb in soil. Peroxidase (POD), catalase (CAT), and malondialdehyde (MDA) activity in the plant leaves were all considerably increased by PE. PE had no discernible impact on plant height, but it did significantly impede root growth. PE affected the morphological contents of heavy metals in soils and plants, while it did not alter their proportions. PE increased the content of heavy metals in the shoots and roots of the two plants by 8.01-38.32% and 12.24-46.28%, respectively. However, PE significantly reduced the Cd extraction amount in plant shoots, while it significantly increased the Zn extraction amount in the plant roots of S. photeinocarpum. For L. camara, a lower addition (0.1%) of PE inhibited the extraction amount of Pb and Zn in the plant shoots, but a higher addition (0.5% and 1%) of PE stimulated the Pb extraction amount in the plant roots and the Zn extraction amount in the plant shoots. Our results indicated that PE microplastics have negative effects on the soil environment, plant growth, and the phytoremediation efficiency of Cd and Pb. These findings contribute to a better knowledge of the interaction effects of microplastics and heavy metal-contaminated soils.

Micro/nanoscale bone char alleviates cadmium toxicity and boosts rice growth via positively altering the rhizosphere and endophytic microbial community

This present study investigated pork bone-derived biochar as a promising amendment to reduce Cd accumulation and alleviate Cd-induced oxidative stress in rice. Micro/nanoscale bone char (MNBC) pyrolyzed at 400 °C and 600 °C was synthesized and characterized before use. The application rates for MNBCs were set at 5 and 25 g·kg^-1 and the Cd exposure concentration was 15 mg·kg^-1. MNBCs increased rice biomass by 15.3-26.0% as compared to the Cd-alone treatment. Both types of MNBCs decreased the bioavailable Cd content by 27.4-54.8%; additionally, the acid-soluble Cd fraction decreased by 10.0-12.3% relative to the Cd alone treatment. MNBC significantly reduced the cell wall Cd content by 50.4-80.2% relative to the Cd-alone treatment. TEM images confirm the toxicity of Cd to rice cells and that MNBCs alleviated Cd-induced damage to the chloroplast ultrastructure. Importantly, the addition of MNBCs decreased the abundance of heavy metal tolerant bacteria, Acidobacteria and Chloroflexi, by 29.6-41.1% in the rhizosphere but had less impact on the endophytic microbial community. Overall, our findings demonstrate the significant potential of MNBC as both a soil amendment for heavy metal-contaminated soil remediation and for crop nutrition in sustainable agriculture.

Concentration and mobility of trace elements (Li, Ba, Sr, Ag, Hg, B) and macronutrients (Ca, Mg, K) in soil-orchid system on different bedrock types

The mobility of chemical elements in the soil-orchid system has been poorly studied. The aim of this study is to evaluate the uptake and mobility of several trace (Li, Ba, Sr, Ag, Hg, and B) and macronutrients (Ca, Mg, and K) in the orchid Anacamptis morio (L.) R.M.Bateman, Pridgeon & M.W.Chase from soils in western Serbia. The sampling sites are characterized by three different bedrock types-cherts, limestones, and serpentines, which are the source of the significant chemical differences in the elemental status of the soil and plant tissues. The four-step Community Bureau of Reference sequential extraction procedure was used to determine the distribution of fractions and predict their potential phytoavailability. The orchid and soil samples were analyzed for total elemental content analysis using ICP-OES. The greatest potential for plant availability was determined for Ba and Sr, representing about 80% of the total soil content. More than 40% of Li in the soils was found to be potentially phytoavailable. Significant correlations were found between the total content of Li, B, and Sr in soils. Between 38 and 60% of Li content and more than 80% of Ba and Sr content were determined to be potentially phytoavailable by sequential analysis. The highest bioconcentration factor (> 1) was determined in the case of B and Sr for all orchid organs, while translocation factor for Li was highest in tubers and leaves. The studied elements were mainly stored in tubers and roots, indicating the exclusion strategy of A. morio as a metal tolerance mechanism. The data obtained showed significant differences in metal content in soils and plants originating from sites with different parent materials, suggesting that bedrock type and associated soil properties are important factors that determine chemical element mobility and uptake.

Essential Metals and Trace Elements in Cereals and Their Derivatives Commercialized and Consumed in Cape Verde

Cereals and their derivatives are basic foods in the human diet and a source of minerals, but the content of elements may vary depending on the type of cereal or its processing. The levels of Na, K, Ca, Mg, Fe, Cu, Zn, Mo, Co, and Mn have been determined in 126 samples of cereals and cereal derivatives (rice, corn gofio, corn flour, wheat flour, corn, and wheat) commercialized and consumed in Cape Verde using an inductively coupled plasma-optical emission spectrometer (ICP-OES) after a wet microwave digestion process. Some elements stand out in products such as corn gofio (K), wheat (Mg), and wheat flour (Fe). Negative correlations were found between Mo-Na and Na-Zn that could suggest interference between these elements. Bearing in mind the dietary intake evaluation and the guideline values provided by EFSA (European Food Safety Authority) or FAO (Food Authority Organization), the consumption of wheat (100 g/day) provides a notable contribution of Mo, Mn, Fe, and Mg. Considering the nutritional value of the analyzed essential and trace elements, the consumption of different cereals and their derivatives should be promoted.

Contrasted speciation distribution of toxic metal(loid)s and microbial community structure in vanadium-titanium magnetite tailings under dry and wet disposal methods

Tailing disposal technologies such as dry and wet disposal methods have a profound effect on the ecosystem of mining areas. However, the chemical speciation of metal(loid)s and microbial community structure in tailings under different disposal methods are still poorly understood. Here we compared the bioavailable fraction of metal(loid)s and the microbial community in vanadium-titanium (V-Ti) magnetite tailing profiles derived from dry and wet stockpiled methods. In wet tailings, the bioavailability of Cr, Cu, Mn, Ni, V, and Zn was higher than that in dry tailings as identified by BCR sequential extraction. Especially for Cu and Ni, the oxidizable fraction was the predominant fraction except the residual fraction, accounting for 37.2-59.0% and 23.2-36.6% of the total concentration in wet tailings, respectively. Based on 16 S rRNA high-throughput sequencing, totally 12 indicator bacterial taxa were detected in dry tailings against 68 in wet tailings. As the biomarkers in wet tailings, genera Sulfuricurvum, Geobacter, and Pseudomonas were expected to be applied to the transformation of metal(loid)s in the tailings. Our results emphasize the importance of dehydration treatment of tailings before stockpiling to minimize the environmental risks caused by toxic metal(loid)s, and provide insights into the engineering application of microbial technologies in V-Ti magnetite tailing area.

An environmental field assessment of soil quality and phytoremediation of toxic metals from saline soil by selected halophytes

The current study has aims to investigate the soil quality and phytoextraction of cadmium (Cd), chromium (Cr), and lead (Pb) from saline soils using Alhagi maurorum (camelthorn), Tamarix aphylla (saltcedar), Salvadora persica (mustard bush), and Suaeda nigra (bush seep weed). The saline bulk soil, rhizospheric soil, and different parts of selected plants were oxidized using the acid mixture and determined Cd, Cr, and Pb by atomic absorption spectrometry. The bio-concentration factor (BCF) and translocation factor (T_F) of also examined. The quality parameters of soil like pH (< 8.5), and electrical conductivity (EC; > 4.00 dS m^-1) indicated the soil is saline. The salinity of soil was lower the organic matters, and total nitrogen contents in studied saline bulk soil due to deterioration condition of soils. However, the rhizospheric soil showed the improved quality of saline soil reflected the good phytoextraction of salts from saline soil. The high contents of Cd in roots and shoots (1.02 and 0.65 µg g^-1) of Alhagi maurorum, Cr in the roots and shoots (6.20, and 6.75 µg g^-1) of Tamarix aphylla and Pb in the roots and shoots (5.63, and 5.75 µg g^-1) of Suaeda nigra. The BCF and T_F showed the Tamarix aphylla and Alhagi maurorum for Pb, Alhagi maurorum, and Salvadora persica for Cr considered as hyperaccumulator plants. Based on BCF and T_F values of Alhagi maurorum, Tamarix aphylla for Cd, and Salvadora persica for Cr and Pb have the efficiency to uptake toxic metals from saline soil. Thus, it can be concluded that selected plant species may have ability for the phytoextraction the Cd, Cr and Pb from saline soil.

Speciation of metals by sequential extractions of agricultural soils located near a dumpsite for prediction of element availability to vegetables

In this paper heavy metal pollution has been investigated by comparing total concentrations and speciation of heavy metals (Cr, Cu, Mn, Zn, Pb and Sr) in soils from four agricultural fields (S1, S2, S3, S4) located in the direct vicinity of the largest landfill in Senegal. The sequential test allowed discriminating between various fractions of heavy metals, namely the acid-extractable fraction, the fraction bound to Fe oxides, the fraction bound to organic matter and the residual fraction. It was proven that the most important fractions of metals (Cr, Cu, Pb, Mn, Sr and Zn) are bound to the residual fraction, more than 50% for most sites, and thus they may be relatively hardly liberated into the environment. The results also showed that the metal pollution in S3 and S4 were more severe than in other sampling sites, especially for Mn and Zn. In addition, the exchangeable fraction, which is the most available, represents from 10 to 47% of the total concentration for Sr, Mn and Zn, indicating that a non-negligible part of these elements may be easily released. Matrix correlation between soil characteristics and the elemental concentrations was tested to study and to detect a possible trend of metal mobilization from organic matter or oxides to agricultural soils. Vegetable grown from the four sampling sites were analyzed, Cr, Zn and Pb concentrations were high in many studied foodstuffs, (up to 54 mg/kg; 45.8 mg/kg and 3.4 mg/kg for Mn, Zn and Pb respectively) and higher than the threshold values of FAO/WHO. Calculation of hazard indexes suggested no potential health risks associated with consuming the vegetables with the exception of cassava and cassava leaves.

Does biochar application in heavy metal-contaminated soils affect soil micronutrient dynamics?

Biochar has been practically used as a soil conditioner in degraded or contaminated soils. Whether biochar would simultaneously affect soil micronutrient bioavailability in heavy metal-contaminated soils warrants research. A 90-d incubation of rice straw biochar with either Pb- or Cd-contaminated soils was conducted to investigate the biochar effect on Fe, Mn, Cu and Zn bioavailability. Biochar amendment decreased the DTPA-extractable, acid extractable and reducible Pb and Cd but increased the oxidizable and residual Pb and Cd. It decreased the DTPA-extractable Fe by 73.8% and 23.1% but increased the DTPA-extractable Mn by 9.8% and 44.3% in the neutral and acidic soil, respectively. The lower Fe availability was attributed to the liming effect and the increased numbers of oxygen-containing groups and organic-mineral phases of biochar over time. Biochar amendment increased soil bacterial richness and diversity in both soils. Rice straw biochar can effectively immobilize heavy metals and reduce soil Fe bioavailability but increase Mn bioavailability, which would potentially affect soil micronutrient fertility and productivity.

The response of bacterial communities to V and Cr and novel reducing bacteria near a vanadium‑titanium magnetite refinery

Soil contamination with multiple heavy metals has always been a pressing issue, but little attention has been given to V and Cr and their chemical fractions' impacts on microorganisms because Cr₂O₃ usually occurs as an associated mineral in vanadium mines. To investigate this issue, samples (N1-N6) less affected by anthropogenic activities were selected for microbial analysis. The area near the refinery was heavily contaminated according to the PLI (pollution load index). Actinobacteriota, Proteobacteria, and Chloroflexi were the dominant phyla in the soil. The diversity of bacteria was positively influenced by V and Cr and negatively influenced by pH, while the abundance was positively correlated with soil nutrients. Interestingly, the influence of heavy metals in the residual fraction on the microbial community structure and functional metabolism was higher than that in the oxidizable fraction, which may be due to the relatively low heavy metal valence of the oxidizable fraction, suggesting that low valence binding forms of multivalence elements have little effect on microorganisms in the soil. Ultimately, two strains with great efficiency in reducing V and Cr were screened, and co-occurrence network characteristics with significant positive interactions suggested that Bacillus can coordinate community structure in the same niche. This research will help to explore the bioavailability of heavy metals and further achieve the bioremediation of heavy metal contamination in soil.

Distribution Characteristics and Relevance of Heavy Metals in Soils and Colloids Around a Mining Area in Nanjing, China

Heavy metal pollution in agricultural soils poses a direct threat to food safety and human health. It has been shown that the colloids is the carrier of heavy metal transport in the polluted soil by heavy metals, but the sources of heavy metals in the soil and colloids and their interrelations are not transparent at present. This study aims to investigate the distribution characteristics of heavy metals in agricultural soils near mining areas, and reveal the relevance of heavy metal content in colloids with total content in soils and their chemical species in soils. Results showed that the concentrations of Mn, Zn, and Pb in agricultural soils and colloids were higher than those of other heavy metals. The content of heavy metals in colloids was positively correlated with the total content of heavy metals in soil. Heavy metals in soil could be easily combined by humus-like substances and tryptophan-like protein in the colloids. The primary source of heavy metals in soil and colloids was mining activities. This study provides theoretical support for revealing the pollution characteristics and migration of heavy metals in agricultural soils and colloids around mining areas.

Heavy Metals Present in the Soils from Extremely Large Opencast Iron Mine Pit

The mining areas have faced severe pollution by caustic metals. In this study, heavy metals (Cu, Zn, Cr, Cd, Pb and Ni) in the soil of an extremely large iron mine pit from Ningwu-Luohe metallogenic belt, one of the seven iron ore areas in China was characterized. SiO₂ was predominant soil mineral composition as 57.0 ± 1.3 %, followed by considerable Al₂O₃ (23.1 ± 2.5 %) and Fe₂O₃ (8.58 ± 1.2 %). Cu, Zn, Cr, Cd, Pb and Ni had the range of 7.62-237, 97.8-313, 1.73-43.8, 0.119-0.512, 5.13-44.7 and 7.87-23.9 mg/kg, respectively, wherein, Cu, Zn, Cr and Pb were likely to have relatively low concentration in the soil from the boom of mining pit. Comparatively, both Cu and Zn arose at the level of 1-fold higher than that of local background values, indicating that the soil from mining pit had been subjected to Cu and Zn accumulation. BCR (European Communities Bureau of Reference) sequential extraction analysis showed that these metals mainly existed in residual fraction, with averaged percentages of 42.0 ± 18 %, 70.3 ± 8.1 %, 76.6 ± 18 %, 30.2 ± 14 %, 52.5 ± 11 % and 61.0 ± 9.7 % for Cu, Zn, Cr, Cd, Pb and Ni, respectively. Geo-accumulation index indicates that the soil was moderately contaminated by Cu, practically uncontaminated or uncontaminated to moderately contaminated by Zn, while practically uncontaminated by Cr, Cd, Pb and Ni. There were just significant relationships between Zn and Cd and between Cd and Pb, indicating that Cd in the soil investigated possibly had at least two sources and for most of the elements the sources were different. The effects of pit depth and major soil composition on the distribution of trace metals varied depending on the element itself and its chemical forms.

Novel agricultural waste-based materials decrease the uptake and accumulation of cadmium by rice (Oryza sativa L.) in contaminated paddy soils

Heavy metal pollution in paddy fields has caused widespread concerns due to the threat to food safety. The present study used low-cost sugarcane bagasse (SB) and two sugarcane bagasse materials modified with citric-acid (SSB) and citric-acid/Fe₃O₄ (MSB) to investigate their effects on the bioavailability of Cd in soil and Cd accumulations in rice in a pot experiment. The three organic amendments significantly decreased the Cd accumulation in plants by limiting its mobilization in soil. The MSB and SSB but not SB increased the soil pH and immobilized the Cd in soil significantly during the 120-day experiment. The amendments decreased Cd bioavailability through transforming to the stable fraction throughout the whole growth stage. The functional groups in the amendments (-OH, -COOH, C-O, -COO^- and Fe-O) and precipitates [Cd(NO₂)₂K(NO₂)₂, Cd(OH)₂ and Cd₇₅Zn₂₅Fe₂O₄] played active roles in Cd immobilization. Moreover, the three organic materials increased the content of Fe-Mn plaque on rice roots, which prevented its transport from soil to rice roots further. We also found that Fe competed with Cd for transporters and reduced potential Cd uptake and translocation in rice tissues. The addition of MSB and SB but not SSB inhibited the rice growth compared to the unamended control, indicating the potential of SSB in situ remediation. These results provide valuable information to use organic amendments for Cd passivation in soil and food safety.

Spatial and temporal variations of Cu and Cd mobility and their controlling factors in pore water of contaminated paddy soil under acid mine drainage: A laboratory column study

Acid mine drainage (AMD) poses a potential threat to human health worldwide, due to its high content of inorganic contaminants including heavy metals. Nevertheless, AMD is commonly used for irrigation of paddy soils. To determine the extent to which AMD affects contaminant levels in such practices, the effect of continuous AMD flooding on pH, redox potential Eh and the migration of Cu and Cd in contaminated paddy soil was studied in column experiments. By means of simulated AMD, dynamic changes of Cu and Cd concentrations in pore water were measured and the controlling factors pH, Eh and presence of Fe, dissolved organic carbon and sulfate were determined over a period of 60 days. Minerals in the soil were assessed by means of an Eh-pH diagram and solid-phase mineral detection. During continuous flooding with AMD-simulated water the soil pH increased, while Eh decreased over time. After 60 days the soil pH stabilized. Cu and Cd concentrations in the pore water negatively correlated with pH and with sulfate concentrations. Five-step sequential extraction illustrated that the fraction of exchangeable Cu increased significantly during AMD flooding. The overall content of Cu increased from initially 0.29 mg/g to 0.41 mg/g, while the content of Cd decreased from 9.2 mg/g to approximately 7.2 mg/g. Mobility factors were calculated and these conformed that Cd mobility significantly increased in contaminated soils during continuous AMD flooding. Our findings indicate that the release of Cu and Cd under AMD flooding can increase potential environmental risks, even though they lead to formation of metal sulfide deposits under anaerobic conditions. The presented data improves our understanding of the impact of overlying water conditions on the mobility of toxic metals in contaminated paddy soils.

Human Exposure to Toxic Metals (Al, Cd, Cr, Ni, Pb, Sr) from the Consumption of Cereals in Canary Islands

The Canary Islands is an archipelago that consumes cereals and derivatives imported from other regions of the world. The increase in contamination with toxic metals makes it necessary to assess the content of toxicological metals of interest to ensure quality and safety. The content of toxic metals (Al, Cd, Cr, Pb, Ni, Sr) was determined in 221 samples of cereals and derivatives (corn, wheat, gofio, corn gofio, barley gofio, roasted corn and flour) marketed in the Canary Islands using ICP-OES (inductively coupled plasma optical emission spectrometry) to assess dietary exposure. Al content recorded in barley gofio (29.5 mg/kg fresh weight) stands out. The estimated daily intake (EDI) of Pb is 52 µg/day if 100 g/day of barley gofio is consumed (121% and 240% of the BMDL nephrotoxicity limit set by the EFSA at 0.63 µg/kg body weight/day for adults and children, respectively). The EDI of PB is 16 µg/day if 30 g barley gofio/day is consumed by adults (36.2% of the abovementioned BMDL nephrotoxicity limit). The EDI of Pb is 7.8 µg/day if 15 g barley gofio/day is consumed by children (32.2% of the abovementioned BMDL nephrotoxicity limit). Gofio is a food of high nutritional value. It is necessary to establish monitoring programs for toxic metals in raw materials and processed products to reduce exposure levels.

Removal Mechanisms of Slag against Potentially Toxic Elements in Soil and Plants for Sustainable Agriculture Development: A Critical Review

Potentially toxic element (PTE) pollution is a major abiotic stress, which reduces plant growth and affects food quality by entering the food chain, and ultimately poses hazards to human health. Currently, the use of slag in PTE-contaminated soils has been reported to reduce PTEs and toxicity in plants. This review highlights the role of slag used as a fertilizer for better crop production and sustainable agricultural development. The application of slag increased the growth, yield, and quality of crops under PTE toxicity. The mechanisms followed by slag are the immobilization of PTEs in the soil, enhancement of soil pH, changes in the redox state of PTEs, and positive changes in soil physicochemical and biological properties under PTE toxicity. Nevertheless, these processes are influenced by the plant species, growth conditions, imposition length of stress, and type of slag used. The current review provides an insight into improving plant tolerance to PTE toxicity by slag-based fertilizer application and highlights the theoretical basis for applying slag in PTE-contaminated environments worldwide.

Toxic Metals in Cereals in Cape Verde: Risk Assessment Evaluation

Consumption of cereals and cereal-based products represents 47% of the total food energy intake in Cape Verde. However, cereals also contribute to dietary exposure to metals that may pose a risk. Strengthening food security and providing nutritional information is a high-priority challenge for the Cape Verde government. In this study, toxic metal content (Cr, Ni, Sr, Al, Cd, and Pb) is determined in 126 samples of cereals and derivatives (rice, corn, wheat, corn flour, wheat flour, corn gofio) consumed in Cape Verde. Wheat flour samples stand out, with the highest Sr (1.60 mg/kg), Ni (0.25 mg/kg) and Cr (0.13 mg/kg) levels. While the consumption of 100 g/day of wheat would contribute to 13.2% of the tolerable daily intake (TDI) of Ni, a consumption of 100 g/day of wheat flour would contribute to 8.18% of the tolerable weekly intake (TWI) of Cd. Results show relevant Al levels (1.17-13.4 mg/kg), with the highest level observed in corn gofio. The mean Pb average content in cereals is 0.03-0.08 mg/kg, with the highest level observed in corn gofio. Al and Pb levels are lower in cereals without husks. Without being a health risk, the consumption of 100 g/day of wheat contributes to 17.5% of the European benchmark doses lower confidence limit (BMDL) of Pb for nephrotoxic effects; the consumption of 100 g/day of corn gofio provides an intake of 1.34 mg Al/day (13.7% of the TWI) and 8 µg Pb/day (20% of the BMDL for nephrotoxic effects). A strategy to minimize the dietary exposure of the Cape Verdean population to toxic metals from cereals should consider the continuous monitoring of imported cereals on arrival in Cape Verde, the assessment of the population's total diet exposure to toxic metals and educational campaigns.

Rhizospheric pore-water content predicts the biochar-attenuated accumulation, translocation, and toxicity of cadmium to lettuce

Metal bioavailability controls its behaviors in soil-plant system, especially involved in biochar amendment. This study compared a rhizospheric pore-water extraction against a BCR sequential extraction method to understand cadmium (Cd) bioavailability in two typical Chinese soils. Soils were spiked with five levels of Cd (CdCl2) and remediated with 3% corn-straw derived biochar. After 60 days of lettuce growth, Cd accumulation and enzyme activities in tissues were analyzed. Results showed that biochar increased soil properties (pH, CEC and SOM) compared to un-amended soils, but decreased contents of bioavailable Cd in soil pore-water (Cdpore-water) and BCR extracted Cd (CdFi+Fii). Contents of Cdpore-water were lower in yellow-brown soils than that in red soils. Pearson analysis showed that bioavailable Cd is negatively correlated with soil pH and CEC (p < 0.05). Cd accumulation in lettuce roots and leaves both were decreased by biochar addition, and the established linear equations proved that soil Cdpore-water is the best predictor for Cd accumulation in lettuce roots (r2 = 0.964) and in leaves (r2 = 0.953), followed by CdFi+Fii. Transfer factor (TF) values of Cd from roots to leaves were lower than 1, and slightly better correlated with soil Cdpore-water (r = -0.674, p < 0.01) than CdFi+Fii (r = -0.615, p < 0.01). Aggregated boosted tree (ABT) analyses indicated that soil properties together with Cdpore-water contribute more than 50% to root enzyme activities. Collectively, soil Cdpore-water is a promising predictor of Cd bioavailability, accumulation and toxicity in soil-plant system with biochar addition.

Effects of carbide slag, lodestone and biochar on the immobilization, plant uptake and translocation of As and Cd in a contaminated paddy soil

The contamination of arsenic (As) and cadmium (Cd) in paddy soils is widely reported and these two metals are difficult to be co-remediated due to the contrasting chemical behaviors. This poses a challenge to simultaneously decrease their availability in soil and accumulation in rice via immobilization by amendments, especially in in-situ fields. This study compared the effects of carbide slag, lodestone and biochar on the bioavailability of As and Cd in soil and their accumulation in rice tissues and root Fe-Mn plaque at tillering and mature stages in a paddy field. The addition of three amendments significantly limited the mobilization of As and Cd in soil and decreased their accumulations in brown rice by 30-52% and 9-21%, respectively. Carbide slag was most whereas lodestone least effective in As and Cd immobilization in the tested contaminated soils. Community Bureau of Reference (BCR) sequential extraction analysis showed that the amendments changed the forms of As and Cd to less-available. Activated functional groups of the amendments (e.g. -OH, C-O, OC-O, OH^- and CO₃^2-) sequestered metals by precipitation, adsorption, ion exchange or electrostatic attributes contributed greatly to the As and Cd immobilization in soil. Furthermore, the amendments promoted the formation of Fe-Mn plaque in rice roots, which further limited the mobility of As and Cd in soil and prevented their transport from soil to rice roots. The application of carbide slag and biochar but not lodestone increased rice yield compared to the unamended control, indicating their applicability in situ remediation. Our study gives a strong reference to select immobilizing amendments for food safe production in co-contaminated paddy soils.

Relation between different metal pollution criteria in sediments and its contribution on assessing toxicity

Several tools have been developed and applied to evaluate the metal pollution status of sediments and predict their potential ecological risk assessment. To date, a comprehensive relationship between the information given by these sediment tools for predicting metal bioavailability and the effective toxicity observed is lacking. In this work, the possible inter-correlations between the data outcoming from using several qualitative evaluation tools of the sediment contamination (contamination factor, CF, the enrichment factor, EF, or the geoaccumulation index, Igeo), metal speciation on sediments (evaluated by the modified BCR sequential extraction procedure) and free metal concentrations in pore waters were studied. It was also our aim to evaluate if these assessment tools could be used for predicting the pore waters toxicity data as toxicity proxy. Principal component analysis and cluster analysis revealed that two quality indices used (CF and EF) were highly correlatable with the more labile fractions from BCR sediment speciation. However, neither of these parameters did correlate with the toxicity of pore waters measured by the chronic toxicity (72 h) in Pseudokirchneriella subcapitata. In contrast, the toxic effects of the given total metal load in sediments were better evaluated by using an additive metal approach using pore water free metal concentrations.

Annual input and output fluxes of heavy metals to paddy fields in four types of contaminated areas in Hunan Province, China

This study focused on the heavy metal concentrations in the soil and their representative input and output fluxes to paddy fields in four types of contaminated areas in Changzhutan urban agglomerations, Hunan, China. Four types of contaminated areas (mining area, livestock breeding area, suburb area and control area) were chosen for monitoring. Three input pathways and three output pathways were considered so as to figure out the heavy metal balance throughout the topsoil. In all study areas, the input fluxes of atmospheric deposition, accounting for 51.21%-94.74% of the total input fluxes, were significantly higher than those of fertilizer and irrigation water. Nevertheless, the manure fertilizer contributes nearly the same proportion as atmospheric deposition in livestock breeding area. In suburb area, only the flux of atmospheric deposition was higher than that in control area, and other input fluxes showed no significant difference. Crop removal, especially straw removal, was the primary output pathway of soil elements, contributing 60.19%-89.37% of the total output fluxes. Annual balance demonstrated that Cd was the metal of the primary concern in study areas. Furthermore, obvious differences were observed among the distribution of heavy metals (Cd, Pb and As) fractions in four types of contaminated areas. In general, the available content was the primary portion of the total contents, mostly up to about 51.70%-87.76%. The information obtained in this paper provides a more comprehensive understanding of the differences in the net inputs of heavy metals among four types of contaminated areas and emphasizes the significance of straw removal for Hunan agricultural soil.

Temporal Variation and Ecological Risk Assessment of Metals in Soil Nearby a Pb⁻Zn Mine in Southern China

Metal contamination in soil from tailings induces risks for the ecosystem and for humans. In this study, the concentrations and ecological risks of Cd, Cu, Pb, and Zn in soil contaminated by a tailing from Yangshuo (YS) lead and zinc (Pb–Zn) mine, which collapsed for more than 40 years, were determined in 2015. The mean concentrations of Zn, Pb, Cu, and Cd were 1301.79, 768.41, 82.60, and 4.82 mg/kg, respectively, which, with years of remediation activities, decreased by 66.9%, 61.7%, 65.4%, and 65.3% since 1986, but still exceed the national standards. From 1986 to 2015, soil pH increased significantly, with available concentrations of Zn, Pb, Cu and Cd decreasing by 13%, 81%, 77%, and 67%, respectively, and potential ecological risk indexes (E_r) of the determined metals decreasing by more than 60%. Horizontally, total contents and percentages of available concentrations of Zn, Pb, Cu, and Cd decreased with the distance from the tailing heap in SD village, while pH values showed the reverse pattern. Vertically, Zn and Cd, Pb, and Cu showed similar vertical distribution patterns in the soil profiles. There was a slight downward migration for the determined metals in soil of M and H area and the mobility was in the order of Cd > Zn > Pb > Cu. It can be concluded that although concentrations and ecological risks of Cd, Cu, Pb, and Zn in soil decreased significantly, SD village is still a high risk area, and the priority pollutant is Cd.

Evaluation of the mobility and pollution index of selected essential/toxic metals in paddy soil by sequential extraction method

Comparative distribution and mobility of selected essential and toxic metals in the paddy soil from district Sargodha, Pakistan was evaluated by the modified Community Bureau of Reference (mBCR) sequential extraction procedure. Most of the soil samples showed slightly alkaline nature while the soil texture was predominantly silty loam in nature. The metal contents were quantified in the exchangeable, reducible, oxidisable and residual fractions of the soil by flame atomic absorption spectrophotometry and the metal data were subjected to the statistical analyses in order to evaluate the mutual relationships among the metals in each fraction. Among the metals, Ca, Sr and Mn were found to be more mobile in the soil. A number of significant correlations between different metal pairs were noted in various fractions. Contamination factor, geoaccumulation index and enrichment factor revealed extremely severe enrichment/contamination for Cd; moderate to significant enrichment/contamination for Ni, Zn, Co and Pb while Cr, Sr, Cu and Mn revealed minimal to moderate contamination and accumulation in the soil. Multivariate cluster analysis showed significant anthropogenic intrusions of the metals in various fractions.

Arsenic, chromium, molybdenum, and selenium: Geochemical fractions and potential mobilization in riverine soil profiles originating from Germany and Egypt

The fractionation and potential mobilization of As, Cr, Mo, and Se in four floodplain soil profiles collected along the Nile (Egypt) and Wupper (Germany) Rivers were assessed using the BCR sequential extraction procedure. The concentrations of total and the geochemical fractions (acid soluble (F1), reducible (F2), oxidizable (F3), and residual (F4) fraction) of the elements were determined. The Wupper soils had the highest total concentrations (mg kg^-1) of As (378) and Cr (2,797) while the Nile soils contained the highest total Mo (12) and Se (42). The residual fraction of As, Cr, Mo, and Se was dominant in the Nile soils suggesting the geogenic source of the elements in these soils. The residual fraction of As and Mo and the oxidizable fraction of Cr and Se were dominant in the Wupper soils. Among the non-residual fractions (potential mobile fractions; PMF = ∑F1-F3), the oxidizable fraction was dominant for Cr, Mo, and Se in the Nile soils and for Mo in the Wupper soils, while the reducible fraction was dominant for As in both soils. The PMF of As, Cr, and Se was higher in the Wupper than in the Nile soils which might reflect the anthropogenic sources of these elements in the Wupper soils, while the opposite was the case for the PMF of Mo. The high PMF of Se (87%), Cr (87%), and As (21%) in the Wupper soils suggested that a release of these toxic elements may happen which increase the potential environmental risks in the anthropogenically polluted soils.

Evaluation of the bioaccessible gastric and intestinal fractions of heavy metals in contaminated soils by means of a simple bioaccessibility extraction test

A study is made to evaluate the bioaccessibility of heavy metals in contaminated soils through a simple bioaccessibility extraction test (SBET), applied to the analysis of both the gastric and intestinal phases. Soils with high metal content of the Mapocho, Cachapoal, and Rancagua series were studied; they are located in suburban areas of large cities in the central valley of Chile. The bioaccessible concentrations of Cd, Cr, Cu, Ni, Pb, and Zn were related to the main physicochemical characteristics of the soils and to the chemical forms obtained by sequential extraction. The elements Cd, Cu, Ni, and Zn are distributed in the soils between the exchangeable fractions, bound to oxides, to organic matter, and in the residual fraction. On the other hand, Cr and Pb are found mainly in the fractions bound to organic matter and in the residual fraction. The three soils have a high Cu content, (640-2060 mg/kg), in the order Cachapoal > Rancagua > Mapocho. The SBET test allowed establishing a different bioaccessibility for the elements in the soil. Cu was notoriously bioaccessible in both the gastric and intestinal phases in the three soils, reaching more than 50% in the Cachapoal and Rancagua soils. The other elements, regardless of the soil, were bioaccessible only in one of the phases, more frequently in the gastric phase. The multiple correlation study indicates that the metal forms have a higher incidence than the soil's physicochemical factors on the extractability to evaluate the human oral bioaccessibility of the metals.

Accumulation of heavy metals in soil-crop systems: a review for wheat and corn

The health risks arising from heavy metal pollution (HMP) in agricultural soils have attracted global attention, and research on the accumulation of heavy metals in soil-plant systems is the basis for human health risk assessments. This review studied the accumulation of seven typical heavy metals-Cd, Cr, As, Pb, Hg, Cu, and Zn-in soil-corn and soil-wheat systems. The findings indicated that, in general, wheat was more likely to accumulate heavy metals than corn. Bioconcentration factor (BCF) of the seven heavy metals in wheat and corn grains decreased exponentially with their average concentrations in soil. The seven heavy metals were ranked as follows, in ascending order of accumulation in corn grains: Pb < Cr < Zn < As < Cu < Cd <Hg. As for the order of accumulation in wheat grains, their ranking was as follows: Zn < Pb < Cr < Cu < As < Hg <Cd. The minimum BCFs of Cd, Cr, As, Pb, Hg, Cu, and Zn in corn grains were 0.054, 6.65 × 10^-4, 7.94 × 10^-4, 0.0044, 0.028, 0.13, and 0.19, respectively. The corresponding BCFs values for wheat grains were 0.25, 0.0045, 5.42 × 10^-4, 0.009, 4.03 × 10^-4, 0.11, and 0.054, respectively.

Fractionation of trace elements in agricultural soils using ultrasound assisted sequential extraction prior to inductively coupled plasma mass spectrometric determination

The main objectives of this study were to determine the concentration of fourteen trace elements and to investigate their distribution as well as a contamination levels in selected agricultural soils. An ultrasonic assisted sequential extraction procedure derived from three-step BCR method was used for fractionation of trace elements. The total concentration of trace elements in soil samples was obtained by total digestion method in soil samples with aqua regia. The results of the extractable fractions revealed that most of the target trace elements can be transferred to the human being through the food chain, thus leading to serious human health. Enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), risk assessment code (RAC) and individual contamination factors (ICF) were used to assess the environmental impacts of trace metals in soil samples. The EF revealed that Cd was enriched by 3.1-7.2 (except in Soil 1). The Igeo results showed that the soils in the study area was moderately contaminated with Fe, and heavily to extremely polluted with Cd. The soil samples from the unplanted field was found to have highest contamination factor for Cd and lowest for Pb. Soil 3 showed a high risk for Tl and Cd with RAC values of greater than or equal to 50%. In addition, Fe, Ni, Cu, V, As, Mo (except Soil 2), Sb and Pb posed low environmental risk. The modified BCR sequential extraction method provided more information about mobility and environmental implication of studied trace elements in the study area.

Micronutrient Fractionation in Coal Mine-Affected Agricultural Soils, India

Assessment of the anthropogenic impacts on bioavailability, mobility, immobility and toxicity of four micronutrients (Cu, Fe, Mn, and Zn) were carried out by Community Bureau of Reference (BCR) fractionation scheme in agricultural soils (n = 10) around Jharia coalfield, eastern India. The relative abundance of micronutrients was as follows: Fe > Mn > Zn > Cu. The enrichment factor was >1 for Zn (6.1) and Cu (1.8) near coal mining area indicated toward soil pollution due to coal mining activities and application of inorganic fertilizers. The I geo values of micronutrients were <0 suggest no pollution with respect to Cu, Fe, Mn and Zn. Correlation analysis showed geogenic origin of soil micronutrients and derived mainly from weathering of minerals present in the parent rock. The mean values of Cu, Mn and Zn were less than certified reference material indicating highly leached agricultural soils in the study region. BCR fractionation of micronutrients showed that a single element could not reveal all types of chemical reactions occurring in soil consortium.

Human health risk assessment of heavy metals in the irrigated area of Jinghui, Shaanxi, China, in terms of wheat flour consumption

Contamination of heavy metals (HMs) in agricultural soil has become a serious environmental problem because it poses a serious threat to human health by entering into food chains. Wheat is a staple food of the majority of the world's population; therefore, understanding the relationship between HM concentration in soils and its accumulation in wheat grain is imperative. This study assessed the concentrations of HMs (i.e., Hg, As, Cd, Cr, Pb, Cu, Zn, and Ni) in agricultural soils (a loess soil, eum-orthic anthrosol) and wheat flour in the historical irrigated area of Jinghui, Northwest China. The potential human health risks of HMs among local residents were also determined by evaluating the consumption of wheat flour. Results showed that the mean soil concentrations of HMs exceeded the corresponding natural background values of agricultural surface soil in Shaanxi: 0.07 mg kg(-1) for Hg, 15.4 mg kg(-1) for As, 0.25 mg kg(-1) for Cd, 75.5 mg kg(-1) for Cr, 27.2 mg kg(-1) for Pb, 28.1 mg kg(-1) for Cu, 81.1 mg kg(-1) for Zn, and 36.6 mg kg(-1) for Ni, respectively. However, all of the mean concentrations of HMs in soil were within the safety limits set by the Chinese regulation (HJ332-2006). The total HM concentrations in wheat flour were 0.0017 mg kg(-1) for Hg, 0.028 mg kg(-1) for As, 0.020 mg kg(-1) for Cd, 0.109 mg kg(-1) for Cr, 0.128 mg kg(-1) for Pb, 2.66 mg kg(-1) for Cu, 24.20 mg kg(-1) for Zn, and 0.20 mg kg(-1) for Ni, and they were significantly lower than the tolerance limits of Chinese standards. However, 15% of the wheat flour samples exceeded the Chinese standard (GB2762-2012) for Pb. This study highlighted the human health risks in the relationship of wheat flour consumption for both adults and children with HMs accumulated area. HMs did not cause noncarcinogenic risks in the area (HI < 1) except for children in Jingyang county; Cd generated the greatest carcinogenic risk, which poses a potential health risk to consumers. The results obtained in this study showed that the government and other institutions should implement measures to prevent and control HM contamination in agricultural soil and crops to mitigate the associated health risks.

Metal contamination of home garden soils and cultivated vegetables in the province of Brescia, Italy: implications for human exposure

BACKGROUND

For the past century, ferroalloy industries in Brescia province, Italy produced particulate emissions enriched in manganese (Mn), lead (Pb), zinc (Zn), copper (Cu), cadmium (Cd), chromium (Cr), iron (Fe), and aluminum (Al). This study assessed metal concentrations in soil and vegetables of regions with varying ferroalloy industrial activity levels.

METHODS

Home gardens (n=63) were selected in three regions of varying ferroalloy plant activity durations in Brescia province. Total soil metal concentration and extractability were measured by X-Ray Fluorescence (XRF), aqua regia extraction, and modified Community Bureau of Reference (BCR) sequential extraction. Unwashed and washed spinach and turnips cultivated in the same gardens were analyzed for metal concentrations by flame atomic absorption spectrometry.

RESULTS

Median soil Al, Cd, Fe, Mn, Pb, and Zn concentrations were significantly higher in home gardens near ferroalloy plants compared to reference home gardens. The BCR method yielded the most mobile soil fraction (the sum of extractable metals in Fractions 1 and 2) and all metal concentrations were higher in ferroalloy plant areas. Unwashed spinach showed higher metal concentrations compared to washed spinach. However, some metals in washed spinach were higher in the reference area likely due to history of agricultural product use. Over 60% of spinach samples exceeded the 2- to 4-fold Commission of European Communities and Codex Alimentarius Commission maximum Pb concentrations, and 10% of the same spinach samples exceeded 2- to 3-fold maximum Cd concentrations set by both organizations. Turnip metal concentrations were below maximum standard reference values.

CONCLUSIONS

Prolonged industrial emissions increase median metal concentrations and most soluble fractions (BCR F1+F2) in home garden soils near ferroalloy plants. Areas near ferroalloy plant sites had spinach Cd and Pb metal concentrations several-fold above maximum standard references. We recommend thorough washing of vegetables to minimize metal exposure.

Assessment on the occupational exposure of urban public bus drivers to bioaccessible trace metals through resuspended fraction of settled bus dust

Limited information is available on the bioaccessible fraction of trace metals in the resuspended fraction of settled bus dust in order to estimate bus drivers' occupational exposure. In this study, 45 resuspended fraction of settled dust samples were collected from gasoline and compressed natural gas (CNG) powered buses and analyzed for trace metals and their fraction concentrations using a three-step sequential extraction procedure. Experimental results showed that zinc (Zn) had the greatest bioaccessible fraction, recorded as an average of 608.53 mg/kg, followed in order of decreasing concentration by 129.80 mg/kg lead (Pb), 56.77 mg/kg copper (Cu), 34.03 mg/kg chromium (Cr), 22.05 mg/kg nickel (Ni), 13.17 mg/kg arsenic (As) and 2.77 mg/kg cadmium (Cd). Among the three settled bus dust exposure pathways, ingestion was the main route. Total exposure hazard index (HIt) for non-carcinogenic effect trace metals was lower than the safety level of 1. The incremental lifetime cancer risk (ILCR) for drivers was estimated for trace metal exposure. Pb and Ni presented relatively high potential risks in the non-carcinogenic and potentially carcinogenic health assessment for all drivers. ILCR was in the range of 1.84E-05 to 7.37E-05 and 1.74E-05 to 6.95E-05 for gasoline and CNG buses, respectively.

Health impact of bioaccessible metal in lip cosmetics to female college students and career women, northeast of China

Actual measure-based studies have estimated ingestion rate of moderate and high daily use to female college students and career women in northeast of China. Sequential extraction analyses showed that total bioaccessible metals concentration in lipstick ranged from 2.103 to 31.103 μg/g and in lip balm ranged from 0.100 to 3.716 μg/g. The relationship between total bioaccessible metal concentrations and the cost of lip cosmetics showed a negative correlation. Lead was detected in all 30 products (100%), with an average concentration of 0.346 for lip balm and 0.407 μg/g for lipstick. With the exception of chromium content in three lipsticks, the estimated exposure in female college students and career women to target metals via lipstick and lip balm ingestion (calculated for moderate and high use) were much lower than the acceptable reference limits. The findings strongly emphasize the need to focus on the health risk of lip balm.

Annual input fluxes of heavy metals in agricultural soil of Hainan Island, China

The accumulation of heavy metals in farmland has become an important issue related to food security and environmental risk. The annual inputs of heavy metals (As, Cd, Hg, Pb, Cr, Cu, and Zn) to agricultural soil for a full year in Hainan Island have been studied. Three fluxes through the cultivated horizon were considered: (1) atmospheric depositions, (2) fertilization, and (3) irrigation water. The corresponding samples were collected and analyzed on a large regional scale. The total input fluxes show obvious spatial variability among different regions. The inventory of heavy metal inputs to agricultural land demonstrates that agricultural soil is potentially at risk of heavy metal accumulation from irrigation water. The potential at risk of heavy metal accumulation from atmospheric deposition and fertilizer is relatively low compared to irrigation. The results indicate that Hg is the element of prior concern for agricultural soil, followed by Cd and As, and other heavy metal elements represent little threat to the environment in the study area. This work provides baseline information to develop policies to control and reduce toxic elements accumulated in agricultural soil.

Chemical speciation and human health risk of trace metals in urban street dusts from a metropolitan city, Nanjing, SE China

The modified BCR (the European Community Bureau of Reference) sequential extraction procedure was applied for partitioning and evaluating the mobility, availability and persistence of trace metals (Al, Cd, Co, Cr, Cu, Ni, Pb, Sr, V and Zn) in urban street dusts collected from different areas of Nanjing, China. The mobility sequence based on the sum of the BCR sequential extraction stages was: Sr (91.65%)>Pb (79.16%)>Zn (74.26%)>Cu (68.53%)>Co (45.98%)>Al (40.01%)≈V (38.45%)≈Ni (37.88%)>Cr (29.35%)>Cd (22.68%). Almost every trace metal had its highest total concentrations in the industrial area, except for Sr which had its highest concentration in the commercial area. Contamination factors (Cf), risk assessment code (RAC) and enrichment factor (Ef) were then calculated to further assess the environmental risk and provide a preliminary estimate of the main sources of trace metals in street dusts. Non-carcinogenic effects and carcinogenic effects due to exposure to urban street dusts were assessed for both children and adults. For non-carcinogenic effects, ingestion was the main route of exposure to street dusts for these metals, followed by dermal contact and inhalation. Hazard index values for all studied metals were lower than the safe level of 1, and Pb exhibited the highest risk value (0.125) in the case of children. The carcinogenic risk for Cd, Co, Cr and Ni were all below the acceptable level (<10(-6)).

Effects of soil properties on the transfer of cadmium from soil to wheat in the Yangtze River delta region, China--a typical industry-agriculture transition area

In order to identify the effects of soil properties on the transfer of Cd from soil to wheat under actual field conditions, 126 pairs of topsoil and wheat samples were collected from the Yangtze River delta region, China. Relevant parameters (Cd, Ca, Mg, Fe, Mn, Zn, N, P, K, S, pH, total organic carbon, and speciation of soil Cd) in soil and wheat tissues were analyzed, and the results were treated by statistical methods. Soil samples (19.8%) and 14.3% of the wheat grain samples exceeded the relevant maximum permissible Cd concentrations in China for agricultural soil and wheat grain, respectively. The major speciations of Cd in soil were exchangeable, bound to carbonates and fulvic and humic acid fraction, and they were readily affected by soil pH, total Ca, Mg, S and P, DTPA-Fe, Ex-Ca, and Ex-Mg. Cadmium showed a strong correlation with Fe, S, and P present in the grain and the soil, whereas there was no significant correlation in the straw or root. Generally, soil pH, Ca, Mg, Mn, P, and slowly available K restricted Cd transfer from soil to wheat, whereas soil S, N, Zn, DTPA-Fe, and total organic carbon enhance Cd uptake by wheat.

Effects of grinding and shaking on Cd, Pb and Zn distribution in anthropogenically impacted soils

The effects of grinding size and shaking process on the results of Cd (cadmium), Pb (lead) and Zn (zinc) distribution measurements three agricultural and three kitchen garden soils highly contaminated by past atmospheric fallout of two lead and zinc smelters in northern France were studied. The physico-chemical parameters and pseudo-total concentration of metals within these soils were determined. The fractionation of metals was performed in triplicate, using the procedure recommended by the Standards, Measurements and Testing program (SM&T), on each air-dried soil sample, ground to pass through 2-mm, 0.315-mm and 0.250-mm sieves and using a reciprocating or rotary shaker. The samples were analysed by flame or electrothermal absorption atomic spectrometry using a self-reversal background system. For both shaking processes, the grinding size had no effect on the fractionation of metals in contaminated agricultural soils. In contrast, using a reciprocating shaker, the fractionation of metals in the kitchen garden samples sieved at <2mm was so different that in the samples prepared to pass through the 0.315-mm and 0.250-mm sieves. Therefore changes (use of a 50 mL graduated polypropylene centrifuge tube, evaporation of the solution to a fixed volume in step 3 and the use of an automatic shaking heating bath) were made to the initial procedure and a rotary shaker was used to improve the suspension of the soil samples during extraction. For all grinding sizes, the fractionation of the three metals contained in the contaminated kitchen garden soil samples was successfully achieved. Nevertheless, some discrepancies from samples sieved at <2mm were obtained. On the other hand, it is worth noting that the effect of the type of shaker on the distribution of metal depended on the soil and the grinding size. From an analytical point of view, precision and trueness were improved after optimisation of the procedure for all sequential extraction procedure steps. The best results were obtained for samples sieved at <0.250 mm. Similar trends were obtained using the CRM BCR(®)-701 certified material. All the results showed that optimisation of the sequential extraction procedure could be adopted for the Cd-, Pb- and Zn-partitioning in contaminated kitchen garden soils with high-level anthropogenic sources.

Chemometric evaluation for the relation of BCR sequential extraction method and in vitro gastro-intestinal method for the assessment of metal bioavailability in contaminated soils in Turkey

INTRODUCTION

A chemometric evaluation has been done to classify metal ions in soils and to determine whether or not the gastric and intestinal phases of a physiologically based extraction test bear any relation to any of the phases of the four-stage Community Bureau of Reference (BCR) extraction protocol.

MATERIALS AND METHODS

Nine trace analytes (As, Ba, Cd, Cr, Cu, Mn, Ni, Pb and Zn) were determined in extracts obtained from the BCR sequential extraction procedure as well as from in vitro gastro-intestinal experiments. The results showed that high As, Pb, Zn and Cd concentrations were found in these soils. Principal component analysis (PCA) and linear discriminant analysis were used as classification techniques. Stepwise multiple linear regression analysis was applied to the data set to determine how the bioaccessibility of a metal is linked to the operationally defined fractions of metal speciation in soil.

RESULTS AND DISCUSSION

This analysis showed that the metal concentrations in the intestinal and gastric extracts are mainly dependent on the concentrations found in BCR phases 1 and 2 for each metal ion except for Cr, which was mainly dependent on the concentrations found in BCR phase 3. From the chemometric technique of correlation analysis, it was concluded that the metals extracted using BCR phases 1 and 2 are more likely to be bioaccessible, i.e. are also extracted by gastric and intestinal digestion solutions. When the correlation and PCA results were interpreted together, it indicated that the bioaccessiblity of Zn, Pb, Mn and Cd were higher than As, Ba, Cr, Ni and Cu for these soils.