Vanadium uptake and translocation in dominant plant species on an urban coastal brownfield site

Interplay between vanadium distribution and microbial community in soil-plant system

Soil-plant system play an essential role in distribution and transformation of vanadium (V). V shapes the diversity of soil communities, while soil microorganisms mediate V transformation. Plants also absorb V from surrounding soil. However, the study of microbial response to V stress in different soil-plant compartments is limited, and the metabolic functions driving V transformation across these systems remain elusive. The study investigates the distribution of V in soil-plant systems nearby a V smelter. 16S rRNA sequencing and metagenomics are utilized to reveal the microbial adaptation and V transformation in bulk soil, rhizosphere, and endosphere. Bothriochloa ischaemum (L.) Keng. (BK) exhibits higher phytoextraction potential (TF = 0.74 ± 0.26). Environmental variables, including pH, V, OM, and AP, show significant (p < 0.05) influence in soil community composition, with homogeneous selection governing the assembly processes in bulk soil and rhizosphere, while stochastic process dominates endospheric assembly. Metagenomic investigation revealed a coordinated metabolic pathway between functional taxa in soil and plants, which lead to root uptake and translocation. V stress is mitigated through Nocardioide, Microvirga, and Solirubrobacter, putatively harboring V(V) reduction genes n arG and mtrC in soil. In rhizosphere, citrate synthase gltA and alkaline phosphatase phoD exhibit functional potential to facilitate formation of V-complexation to increase V mobility. In endoshere, endophytic Enterobacter further detoxifies V(V), and likely promotes V translocation through siderophore biosynthesis gene, iucA. These findings enhance our understanding on interplay between V and microbial community in soil-plant systems, which is instrumental in developing mitigation plan for V contaminated sites.

Determination of the Suitable Biomonitors to be used in Monitoring the Change for Reducing the Concentration of V in Areas with High-Level of Air Pollution

In this study, Vanadium (V) concentrations were analyzed in five tree species (Pinus pinaster, Cupressus arizonica, Picea orientalis, Cedrus atlantica, and Pseudotsuga menziesii) from Duzce city (Turkey), a highly polluted area. The research compared V levels across species, organs, directions, and age groups over the past 40 years. Trees, which absorb nutrients from soil and air, were used as biomonitors. Cupressus arizonica and Cedrus atlantica emerged as effective for V mitigation due to high wood accumulation. Significant inter- and intra-species variations in V concentrations were noted, underscoring their potential as V indicators. Annual rings from older trees offer a long-term monitoring method. This study highlights the importance of species-specific selection for monitoring heavy metals and the role of wood in preventing reintroduction of metals into ecosystems. It enhances our understanding of V dynamics and the environmental monitoring potential of these species.

Vanadium in the Environment: Biogeochemistry and Bioremediation

Vanadium(V) is a highly toxic multivalent, redox-sensitive element. It is widely distributed in the environment and employed in various industrial applications. Interactions between V and (micro)organisms have recently garnered considerable attention. This Review discusses the biogeochemical cycling of V and its corresponding bioremediation strategies. Anthropogenic activities have resulted in elevated environmental V concentrations compared to natural emissions. The global distributions of V in the atmosphere, soils, water bodies, and sediments are outlined here, with notable prevalence in Europe. Soluble V(V) predominantly exists in the environment and exhibits high mobility and chemical reactivity. The transport of V within environmental media and across food chains is also discussed. Microbially mediated V transformation is evaluated to shed light on the primary mechanisms underlying microbial V(V) reduction, namely electron transfer and enzymatic catalysis. Additionally, this Review highlights bioremediation strategies by exploring their geochemical influences and technical implementation methods. The identified knowledge gaps include the particulate speciation of V and its associated environmental behaviors as well as the biogeochemical processes of V in marine environments. Finally, challenges for future research are reported, including the screening of V hyperaccumulators and V(V)-reducing microbes and field tests for bioremediation approaches.

Responses of rhizosphere microbial community structure and metabolic function to heavy metal coinhibition

Metal mineral mining results in releases of large amounts of heavy metals into the environment, and it is necessary to better understand the response of rhizosphere microbial communities to simultaneous stress from multiple heavy metals (HMs), which directly impacts plant growth and human health. In this study, by adding different concentrations of cadmium (Cd) to a soil with high background concentrations of vanadium (V) and chromium (Cr), the growth of maize during the jointing stage was explored under limiting conditions. High-throughput sequencing was used to explore the response and survival strategies of rhizosphere soil microbial communities to complex HM stress. The results showed that complex HMs inhibited the growth of maize at the jointing stage, and the diversity and abundance of maize rhizosphere soil microorganisms were significantly different at different metal enrichment levels. In addition, according to the different stress levels, the maize rhizosphere attracted many tolerant colonizing bacteria, and cooccurrence network analysis showed that these bacteria interacted very closely. The effects of residual heavy metals on beneficial microorganisms (such as Xanthomonas, Sphingomonas, and lysozyme) were significantly stronger than those of bioavailable metals and soil physical and chemical properties. PICRUSt analysis revealed that the different forms of V and Cd had significantly greater effects on microbial metabolic pathways than all forms of Cr. Cr mainly affected the two major metabolic pathways: microbial cell growth and division and environmental information transmission. In addition, significant differences in rhizosphere microbial metabolism under different concentrations were found, and this can serve as a reference for subsequent metagenomic analysis. This study is helpful for exploring the threshold for the growth of crops in toxic HM soils in mining areas and achieving further biological remediation.

Soil amendments for vanadium remediation: a review of remediation of vanadium in soil through chemical stabilization and bioremediation

Immobilization of vanadium (V) in soils is one option to prevent groundwater contamination and plant uptake. Phytoremediation, microbial remediation, and chemical stabilization using soil amendments are among the leading environmentally friendly and economically feasible techniques in V remediation. Soil amendments were used to reduce V mobility by immobilizing it in the soil matrix through chemical stabilization, while bioremediation methods such as phytoremediation and microbial remediation were used to remove V from contaminated soils. Vanadium exists in several species and among them V5+ species are the most prevalent, toxic, and soluble form and present as a negatively charged ion (H2VO4- and HVO42-) in oxic soils above pH 4. Amendments used for chemical stabilization can change the physicochemical properties enhancing immobility of V in soil. The pH of the soil environment, point of zero charge of the colloid surface, and redox conditions are some of the most important factors that determine the efficiency of the amendment. Commonly used amendments for chemical stabilization include biochar, zeolites, organic acids, various clay minerals and oxides of elements such as iron, titanium, manganese, and aluminum. For bioremediation, chelating agents and microbial communities are used to mobilize V to enhance phyto-or microbial-extraction procedures. The objectives of this review were to discuss remediation methods of V while considering V speciation and toxicity in soil, and soil amendment application for V removal from soil. The information compiled in this review can guide further research on soil amendments for optimal V remediation in largely contaminated industrial sites.

Comparative Responses of Silicon to Reduce Cadmium and Enrich Selenium in Rice Varieties

Cadmium (Cd), a highly toxic heavy metal for crops in China, poses a significant threat to rice cultivation. It is crucial to identify the genotypes with robust resistance to heavy metals, including Cd, in rice. The experiment was conducted to examine the mitigation effect of silicon (Si) on Cd toxicity levels in Se-enriched Z3055B and non-Se-enriched G46B rice genotypes. A basal dose of Si improved the growth and the quality of rice significantly by reducing the Cd content in rice roots, stems, leaves and grains and increased the yield, biomass and selenium (Se) content of brown rice in both genotypes. Additionally, Se content in brown rice and polished rice was notably higher in Se-enriched rice than in non-Se-enriched rice, with the highest amount at 0.129 mg/kg and 0.085 mg/kg, respectively. The results demonstrated that a basal fertilizer concentration of 30 mg/kg of Si was more effective in reducing Cd transport from roots to shoots in Se-enriched rice than in non-Se-enriched rice genotypes. Therefore, it can be concluded that Se-enriched rice genotypes are a viable option for food crop production in Cd-contaminated areas.

Vanadium-resistant endophytes modulate multiple strategies to facilitate vanadium detoxification and phytoremediation in Pteris vittata

Vanadium (V) contamination of soils poses potential risks to humans and ecosystems. This study was conducted to evaluate the effects of endophyte-assisted phytoremediation and to determine the mechanisms involved in V detoxification and plant growth promotion. Results showed that the endophytic bacterium Serratia marcescens PRE01 could successfully colonize the roots and increase the total V uptake of Pteris vittata by 25.4 %, with higher plant biomass and V accumulation in roots. Endophyte inoculation significantly improved the secretion of phytic, malic, and oxalic acids and accelerated FeVO₄ dissolution and subsequent Fe and V uptake in the rhizosphere. Under V stress without inoculation, V removed by shoot uptake, root uptake, and root surface adsorption accounted for 21.76 %, 42.14 %, and 30.93 % of the total V removal efficiency, respectively. To detoxify excess V, PRE01 effectively strengthened the adsorption of V on the root surface, with an increase in its contribution to the total V removal efficiency from 30.93 % to 38.10 %. Furthermore, beneficial endophytes could alleviate oxidative damage caused by V stress by reinforcing the plant antioxidant system and promoting V(V) reduction in root tissues. These findings clearly reveal that inoculation with endophytes is a promising method for modulating multiple strategies to enhance the phytoremediation of V-contaminated soils.

Distribution, co-existing metals, and potential health risk of fluorine in farmland soil in different anthropogenic activity dominated districts in a county-level city in Sichuan province, Southwest China, in 2015

Continuous fluorine (F) accumulation in soil by anthropogenic activities leads to variously global environmental and health issues. Herein, 300 farmland soil samples were collected from different anthropogenic activity dominated districts for studying the distribution and related health risk of F in soils. Co-existing metal concentrations in soil samples were also analysed to evaluate the relationship between the distribution of F and metals in soil. The median value of the total F concentration of 488 mg kg^-1 in the present samples was higher than the median background F concentration in topsoil in Sichuan province of China (261 mg kg^-1). Concentration of water-soluble F (1.33-26.2 mg kg^-1) was two or three orders of magnitude less than that of total F in soil. Levels of total and water-soluble F in soils collected from the district with longer contamination history were higher than that from other districts with shorter contamination period, indicating a historical contribution of anthropogenic activities to F accumulation in soil. Notable positive correlation between the total F and vanadium (V) concentration in soil can be partly linked to the usually negative charged form or a common source of F and V in soil (e.g. coal combustion). Compared with inhalation and dermal contact, present human exposure of F in soil was mainly caused by oral ingestion, and the health risks posed by F in soil for both children and adults were acceptable. However, considering the higher potential risk for children than adults, the accumulation of F in soil induced by anthropogenic activities should not be neglect.

Vanadium: A Review of Different Extraction Methods to Evaluate Bioavailability and Speciation

The excessive input of heavy metals such as vanadium (V) into the environment has been one of the consequences of global industrial development. Excessive exposure to V can pose a potential threat to ecological safety and human health. Due to the heterogeneous composition and reactivity of the various elements in soils and sediments, quantitative analysis of the chemical speciation of V in different environmental samples is very complicated. The analysis of V chemical speciation can further reveal the bioavailability of V and accurately quantify its ecotoxicity. This is essential for assessing for exposure and for controlling ecological risks of V. Although the current investigation technologies for the chemical speciation of V have grown rapidly, the lack of comprehensive comparisons and systematic analyses of these types of technologies impedes a more comprehensive understanding of ecosystem safety and human health risks. In this review, we studied the chemical and physical extraction methods for V from multiple perspectives, such as technological, principle-based, and efficiency-based, and their application to the evaluation of V bioavailability. By sorting out the advantages and disadvantages of the current technologies, the future demand for the in situ detection of trace heavy metals such as V can be met and the accuracy of heavy metal bioavailability prediction can be improved, which will be conducive to development in the fields of environmental protection policy and risk management.

The role and its transcriptome mechanisms of cell wall polysaccharides in vanadium detoxication of rice

Cell wall-polysaccharides play a crucial role in heavy metals binding, and hence, contribute to heavy metal detoxication in plants. However, there is no data regarding the molecular mechanisms of vanadium (V) binding to root cell walls in plants, especially in rice (Oryza sativa L.). Taking two rice cultivars with various V tolerance as the research material, the present study investigated the effect of various V concentrations on subcellular distribution of V and revealed the regulatory mechanism of cell wall polysaccharides to V exposure. The results showed that rice roots inhibited the upward movement of V, and root cell walls accumulated 69.85-82.71% of V in roots. Furthermore, hemicellulose-1 (HC-1) in cell walls shared up to 67.72% and 66.95% of the cell-wall-bound V in tolerant and sensitive cultivars, respectively. FTIR spectroscopy demonstrated that V stress induced the remolding of cell wall polysaccharides. Under V stress, V-tolerant rice generated up to 19.3% pectin, 40.9% HC-1, and 49.34% HC-2, which were higher than V-sensitive cultivar. The genes encoding UGDH, UGE, and AXS for polysaccharide biosynthesis were higher expressed in V-tolerant rice than V-sensitive rice when exposed to V. The results could provide novel insight for phytoremediation and food security guarantees.

Effect of vanadium on Lactuca sativa L. growth and associated health risk for human due to consumption of the vegetable

Elevated vanadium in the environment adversely affects organisms, including plants, animals, and humans. Plants act as the main conduit for environmental vanadium to enter the food chain, and simultaneously their growth response characteristics reflect vanadium toxicity efficacy for plants. The aim of the present study is to investigate lettuce (Lactuca sativa L.) growth involving morphological change, physiological adjustment, vanadium accumulation under vanadium stress, and the potential health risk (expressed as health risk index (HRI)) of adults and children who consume it. Lettuce was grown in nutrient solution with 0, 0.1, 0.5, 2.0, and 4.0 mg L-1 of pentavalent vanadium [V(V)]. Results showed that 0.1 mg L-1 V did not significantly affect lettuce growth versus control, and marked depression arose at ≥ 0.5 mg L-1 V. Foliar proline increased rapidly at ≥ 0.5 mg L-1 V. No striking change emerged in leaf cell membrane permeability at all treatments. V(V) and total vanadium concentration in plant tissues were ordered as root > stem > leaf, while tetravalent vanadium [V(IV)] was leaf > root > stem. No health risk (HRI < 1) exists for adults and children who consume lettuce at control treatment. However, the health risk occurs (HRI ˃ 1) when they both ingest the seedlings exposed to ≥ 0.1 mg L-1 V, and the risk overall markedly increases with increasing vanadium. Therefore, enough attention needs to be paid to the human health associated with the ingestion of vegetables like lettuce grown in substrata contaminated by vanadium.

Citric acid and AMF inoculation combination-assisted phytoextraction of vanadium (V) by Medicago sativa in V mining contaminated soil

The use of citric acid (CA) chelator to facilitate metal bioavailability is a promising approach for the phytoextraction of heavy metal contaminants. However, the role of the CA chelator associated with arbuscular mycorrhizal fungi (AMF) inoculation on phytoextraction of vanadium (V) has not been studied. Therefore, in this study, a greenhouse pot experiment was conducted to evaluate the combined effect of CA chelator and AMF inoculation on growth performance and V phytoextraction of plants in V-contaminated soil. The experiment was performed via CA (at 0, 5, and 10 mM kg^-1 soil levels) application alone or in combination with AMF inoculation by Medicago sativa Linn. (M. sativa). Plant biomass, root mycorrhizal colonization, P and V accumulation, antioxidant enzyme activity in plants, and soil chemical speciation of V were evaluated. Results depicted (1) a marked decline in plant biomass and root mycorrhizal colonization in 5- and 10-mM CA treatments which were accompanied by a significant increased V accumulation in plant tissues. The effects could be attributed to the enhanced acid-soluble V fraction transferring from the reducible fraction. (2) The presence of CA significantly enhanced P acquisition while the P/V concentration ratio in plant shoots and roots decreased, owing to the increased V translocation from soil to plant. (3) In both CA-treated soil, AMF-plant symbiosis significantly improved dry weight (31.4-73.3%) and P content (37.3-122.5%) in shoots and roots of M. sativa. The combined treatments also showed markedly contribution in reduction of malondialdehyde (MDA) content (12.8-16.2%) and higher antioxidants (SOD, POD, and CAT) activities in the leaves. This suggests their combination could promote growth performance and stimulate antioxidant response to alleviate V stress induced by CA chelator. (4) Taken together, 10 mM kg^-1 CA application and AMF inoculation combination exhibited a higher amount of extracted V both in plant shoots and roots. Thus, citric acid-AMF-plant symbiosis provides a novel remediation strategy for in situ V phytoextraction by M. sativa in V-contaminated soil.

Vanadium accumulation mode of Heteropogon contortus and its driving factors in Majiatian tailing reservoir in Panzhihua, Southwestern China

Native plants in metal pollution sites have great potentials for mine rehabilitation. In the presented work, we investigated Vanadium (V) concentrations of soils and plants (Heteropogon contortus) in Majiatian V-Ti magnetite tailing reservoir in Panzhihua, Southwestern China. The objectives were to explore the V accumulation mode of H. contortus and its driving factors, as well as the phytoremediation potential of H. contortus. As the results, H. contortus accumulated 37.53 mg/kg and 8.69 mg/kg of V in root and aerial part, respectively. With the increase of rehabilitation age, root V concentrations decreased, while aerial part V concentrations remained constant. The significant negative correlations between root V and soil V, acid-soluble V (V_HAc) (P < 0.05) indicated that increasing soil V and V_HAc concentrations drove the V accumulation mode of H. contortus. Soil properties had a little influence on the V accumulation mode of H. contortus. Therefore, H. contortus might be not the suitable plant extractant to remove V from mine tailing for its lower V accumulation capacity. On the other hand, it can tolerate high V stress through elimination and detoxification/isolation V. Furthermore, the settlement of H. contortus increased the content of soil organic matter and might thus improve the soil quality. The cover of H. contortus is also beneficial to reduce the dispersion of the tailings and prevent contaminating surrounding soil. Therefor it showed a great potential to serve as a pioneer plant in the remediation of V-rich tailing reservoirs and other V-contaminated sites with similar poor soil condition.

A Dual Role of Vanadium in Environmental Systems-Beneficial and Detrimental Effects on Terrestrial Plants and Humans

The importance of vanadium (V) in the functioning of land systems is extremely diverse, as this element may exert both positive and harmful effects on terrestrial organisms. It recently become considered an element of beneficial character with a range of applications for human welfare. The health-ameliorative properties of this transition element depend on its degree of oxidation and on optimal concentration in the target cells. It was found that a similar relationship applies to vascular plants. However, excessive amounts of vanadium in the environment contaminate the soil and negatively affect the majority of living organisms. A significantly elevated level of V results in the destabilization of plant physiological balance, slowing down the growth of biomass which significantly reduces yield. In turn, low doses of the appropriate vanadium ions can stimulate plant growth and development, exert cytoprotective effects, and effectively enhance the synthesis of some biologically active compounds. We present the scientific achievements of research teams dealing with such topics. The issues discussed concern the role of vanadium in the environment, particular organisms, and highlight its dualistic influence on plants. Achievements in the field of V bioremediation, with the use of appropriately selected microorganisms and plant species, are emphasized.

Vanadium in soil-plant system: Source, fate, toxicity, and bioremediation

Vanadium(V) is an important component of industrial activities, while it may pose toxic hazards to plants, animals, and humans at high levels. Owing to its various uses in numerous industrial processes, high amount of V is released into the soil environment. Previous literature has focused on the biogeochemistry and ecotoxicity of V in soil-plant system. Consequently, this overview presents its source, fate, phyto-uptake, phyto-toxicity, detoxification, and bioremediation based on available data, especially published from 2015 to 2020. Vanadium occurs as various chemical forms (primarily as V(V) and V(IV)) in the soil environment, and its biogeochemical behaviour is easily influenced by soil conditions including redox potential, soil pH, organic matter, and microorganisms. Vanadium mainly accumulates in plant roots with very limited translocation to shoots. However, plants such as dog's tail grass and green bean are reported to accumulate high levels of V in aboveground tissues. An insight into the processes and mechanisms that allow plants to absorb and translocate V in soil-plant system is also stressed in this overview. In plants, low levels of V have beneficial effects on plant growth and development. Nevertheless, excessive V provokes numerous deleterious effects including reducing seed germination, inhibiting root and shoot growth, depressing photosynthesis, interfering with nutrients uptake, inducing overgeneration of ROS, and leading to lipid peroxidation. Mechanisms related to detoxification strategies like sequestration in root system, compartmentation in vacuoles and cell wall, and antioxidant defence systems to endure V-induced toxicity in plants are discussed as well. The detailed knowledge of bioremediation involved in the cleanup of V-contaminated soils would immensely help understand and improve the remediation process. Furthermore, this overview outlines several research gaps requiring further investigation in order to advance our understanding of the biogeochemical roles of V in soil-plant systems.

Growth responses, accumulation, translocation and distribution of vanadium in tobacco and its potential in phytoremediation

The metal tolerance mechanism of plants is of great importance to explore the plant-based clean-up of environmental substrata contaminated by heavy metals. Indoor experiment of tobacco (Nicotiana tabacum L.) seedlings growing hydroponically in nutrient solution containing 0, 0.1, 0.5, 2.0, and 4.0 mg L-1 V was conducted. The results indicated that plant overall growth performance was significantly affected at ≥ 2.0 mg L-1 V. Oxidative stress degree as indicated by foliar O2-· and H2O2 content intensified markedly at ≥ 0.5 mg L-1 V treatments. In response, the plant activated its enzyme and non-enzyme protecting mechanism to cope with oxidative stress inflicted by vanadium. The activities of antioxidant enzymes, including SOD, POD, CAT, APX, and the concentration of non-enzyme antioxidants, e.g., AsA and GSH were all conspicuously (p < 0.5 or p < 0.1) enhanced at ≥ 0.5 mg L-1 V treatments. Vanadium accumulated in leaves, stems, and roots increased with increasing vanadium level. The majority of the absorbed vanadium retained in plant root, and minor portions were transferred to aerial parts. Vanadium concentration in plant tissues ordered as root ˃ stem ˃ leaf. Translocation factors (TF) in vanadium-treated tobaccos (TF « 1) were significantly lower than that of control (TF ˃ 1). In conclusion, although vanadium at ≥ 2.0 mg L-1 inhibited plant growth, tobacco exhibited a relatively good vanadium tolerance through self-adaptive regulation and has the potential as a phytostabilizer in decontaminating the environment contaminated by vanadium.

Review of plant-vanadium physiological interactions, bioaccumulation, and bioremediation of vanadium-contaminated sites

Vanadium is a multivalent redox-sensitive metal that is widely distributed in the environment. Low levels of vanadium elevate plant height, root length, and biomass production due to enhanced chlorophyll biosynthesis, seed germination, essential element uptake, and nitrogen assimilation and utilization. However, high vanadium concentrations disrupt energy metabolism and matter cycling; inhibit key enzymes mediating energy production, protein synthesis, ion transportation, and other important physiological processes; and lead to growth retardation, root and shoot abnormalities, and even death of plants. The threshold level of toxicity is highly plant species-specific, and in most cases, the half maximal effective concentration (EC₅₀) of vanadium for plants grown under hydroponic conditions and in soil varies from 1 to 50 mg/L, and from 18 to 510 mg/kg, respectively. Plants such as Chinese green mustard, chickpea, and bunny cactus could accumulate high concentrations of vanadium in their tissues, and thus are suitable for decontaminating and reclaiming of vanadium-polluted soils on a large scale. Soil pH, organic matter, and the contents of iron and aluminum (hydr)oxides, phosphorus, calcium, and other coexisting elements affect the bioavailability, toxicity, and plant uptake of vanadium. Mediation of these conditions or properties in vanadium-contaminated soils could improve plant tolerance, accumulation, or exclusion, thereby enhancing phytoremediation efficiency. Phytoremediation with the assistance of soil amendments and microorganisms is a promising method for decontamination of vanadium polluted soils.

Characteristic of adsorption, desorption, and co-transport of vanadium on humic acid colloid

Understanding the interactions between humic acid colloid (HAC) and vanadium (V) in soils is of great importance in forecasting the behaviors and fates of V in the soil and groundwater systems. This study investigated the characteristics and factors that affect V adsorption-desorption by the HAC; meanwhile, we also explored the co-transport of the HAC and V in a saturated porous media. Scanning Electronic Microscopy micrographs showed the variation of morphological features on the surface of the HAC before and after V adsorption. Fourier transform infrared spectroscopy spectra revealed that the presence of hydroxyl, carboxyl, carbonyl, carbon-carbon double bond, amino, and aromatic ring on the HAC participated in V adsorption. The adsorption isotherms were well described by the Langmuir model, and the adsorption kinetics of the HAC was better described by the pseudo-first-order kinetic models. The adsorption-desorption was strongly dependent on the initial V concentration, solution pH, and temperature. The maximum adsorption amount was 861.17 mg g^-1 by 200 mg L^-1 HAC at the initial V concentration of 500 mg L^-1, and the corresponding desorption amount was 15.13 mg g^-1. These results showed that the HAC had high fixation capacity of V in soil. In addition, the HAC sped up the mobility of V; however, it decreased mass of migration of V in the saturated quartz sand column. These results are expected to provide insight into the potential impact of HAC on geochemical behaviours of V in vulnerable ecosystems.

Bioaccumulation and growth characteristics of Vallisneria natans (Lour.) Hara after chronic exposure to metal-contaminated sediments

Metal-contaminated sediments in lakes is a global concern that poses toxicological risk to aquatic organisms. This study performed bioassays using the submerged macrophyte, Vallisneria natans (Lour.) Hara, exposed to contaminated sediments collected from five locations in Dianchi Lake, Yunnan, China. Among the sediments collected, I_geo showed enrichment of As and Cd in Dianchi Lake sediments. In spite of enriched toxic metals at some locations, laboratory bioassays found no significant difference in leaf biomass or leaf photosynthesis rate between the sites. Root biomass and root activity showed significant differences between locations and were negatively correlated with the concentration of As, Cd, Hg, and Pb in sediment but not related to Cr. The above correlations were strongest for Hg and As, respectively. Accumulation of Cd and Pb to leaves of bioassay plants was observed, but this was not evident for As and Cr. Overall, the results indicate that V. natans can be used as a bioassay organism and measures of root toxicity are sensitive to metal concentrations present in Dianchi Lake sediments. Furthermore, the study species holds promise for use as a biomonitor of Cd and Pb sediment metal content.

A scientometric analysis and visualization of global research on brownfields

Brownfields have attracted increasing attentions from both researchers and practitioners. However, few studies have attempted to make a comprehensive and quantitative review on this topic. This study conducted a scientometric review on the brownfield research from 1995 to 2017 using CiteSpace. The knowledge structure, hot topics, research trends, and gaps were analyzed based on the co-author, co-word, co-citation, and clusters analysis. Six hundred thirty articles from the Web of Science core collection database were selected as the research samples. Results revealed that the research focus has changed from soil remediation technologies to sustainable regeneration methods. The most vital development in brownfield research occurred in the USA, England, Canada, Germany, and China. "Brownfield," "heavy metal," "remediation," "redevelopment," and "sustainability" were the most frequently used keywords. Whereas "management" and "biodiversity" received citation bursts in recent years. Existing researches mainly concentrated on subject categories of environmental sciences ecology, environmental sciences, engineering, environmental studies, engineering environmental, and urban studies. Sustainable regeneration, urban brownfields' regeneration, mental distribution, coal-mine brownfield, and ecosystem service were the identified co-citation clusters and represented the hot topics and emerging trends. The research gaps can serve as a motivation to research on the next generation of brownfields to support the sustainable development. This study provides researchers and practitioners an extensive and intensive understanding of the salient research themes and trends of brownfields' research worldwide.

Redox chemistry of vanadium in soils and sediments: Interactions with colloidal materials, mobilization, speciation, and relevant environmental implications- A review

Vanadium (V), although serving as an important component of industrial activities, has bioinorganic implications to pose highly toxic hazards to humans and animals. Soils and sediments throughout the world exhibit wide ranges of vanadium concentrations. Although vanadium toxicity varies between different species, it is mainly controlled by soil redox potential (E_H). Nonetheless, knowledge of the redox geochemistry of vanadium lags in comparison to what is known about other potentially toxic elements (PTEs). In particular, the redox-induced speciation and mobilization of vanadium in soils and sediments and the associated risks to the environment have not been reviewed to date. Therefore, this review aims to address 1) the content and geochemical fate of vanadium in soils and sediments, 2) its redox-induced release dynamics, 3) redox-mediated chemical reactions between vanadium and soil organic and inorganic colloidal materials in soil solution, 4) its speciation in soil solution and soil-sediments, and 5) the use of advanced geochemical and spectroscopic techniques to investigate these complex systems. Vanadium (+5) is the most mobile and toxic form of its species while being the thermodynamically stable valence state in oxic environments, while vanadium (+3) might be expected to be predominant under euxinic (anoxic and sulfidic) conditions. Vanadium can react variably in response to changing soil E_H: under anoxic conditions, the mobilization of vanadium can decrease because vanadium (+5) can be reduced to relatively less soluble vanadium (+4) via inorganic reactions such as with H₂S and organic matter and by metal-reducing microorganisms. On the other hand, dissolved concentrations of vanadium can increase at low E_H in many soils to reveal a similar pattern to that of Fe, which may be due to the reductive dissolution of Fe(hydr)oxides and the release of the associated vanadium. Those differences in vanadium release dynamics might occur as a result of the direct impact of E_H on vanadium speciation in soil solution and soil sediments, and/or because of the E_H-dependent changes in soil pH, chemistry of (Fe)(hydr)oxides, and complexation with soil organic carbon. Release dynamics of vanadium in soils may also be affected positively by soil pH and the release of aromatic organic compounds. X-ray absorption spectroscopy (XAS) is a powerful tool to investigate the speciation of vanadium present in soil. X-ray absorption near edge structure (XANES) is often used to constrain the average valence state of vanadium in soils and sediments, and in limited cases extended X-ray absorption fine structure (EXAFS) analysis has been used to determine the average molecular coordination environment of vanadium in soil components. In conclusion, this review presents the state of the art about the redox geochemistry of vanadium and thus contributes to a better understanding of the speciation, potential mobilization, and environmental hazards of vanadium in the near-surface environment of uplands, wetlands, and agricultural ecosystems as affected by various colloidal particles. Further research is needed to elucidate the geochemistry and speciation of vanadium in the dissolved, colloidal, and soil sediments phases, including the determination of factors that control the redox geochemistry of vanadium.

Effective phytoremediation of low-level heavy metals by native macrophytes in a vanadium mining area, China

Heavy metal contamination, particularly vanadium contamination in mining and smelting areas, is a worldwide serious problem threatening the ecological system and human health. The contamination level of vanadium, arsenic, cadmium, chromium, mercury, and lead in sediments and waters in a vanadium mining area in China was investigated in the present study. The behavior of heavy metal uptake by 12 native aquatic macrophytes was evaluated, including 5 species of emergent aquatic plants (Acorus calamus, Scirpus tabernaemontani, Typha orientalis, Phragmites australis, and Bermuda grass), 3 species of floating plants (Marsilea quadrifolia, Nymphaea tetragona, and Eleocharis plantagineiformis), and 4 species of submerged plants (Hydrilla verticillata, Ceratophyllum demersum, Myriophyllum verticillatum, and Potamogetom crispus). Different heavy metal accumulation abilities were found across these macrophytes. Generally, they tended to accumulate higher contents of chromium, and C. demersum showed a particularly higher accumulation capacity for vanadium. The heavy metals were preferentially distributed in roots, instead of translocation into leaves and stems, indicating an internal detoxification mechanism for heavy metal tolerance in macrophytes. In 24-day laboratory hydroponic experiments, the macrophytes had a satisfied phytoremediation performance for heavy metals, when their concentrations were at the microgram per liter level. Particularly, vanadium was effectively removed by P. australis and C. demersum, the removal efficiencies of which were approximately 50%. In addition, a combination of terrestrial plant (Bermuda grass) and aquatic macrophytes (P. australis, M. quadrifolia, and C. demersum) exhibited high uptake capacity of all the six heavy metals and their residual concentrations were 95 (vanadium), 39.5 (arsenic), 4.54 (cadmium), 17.2 (chromium), 0.028 (mercury), and 7.9 (lead) μg/L, respectively. This work is of significant importance for introducing native macrophytes to remove low-level heavy metal contamination, particularly vanadium, and suggests phytoremediation as a promising and cost-effective method for in situ remediation at mining sites.

The interactions of metal concentrations and soil properties on toxic metal accumulation of native plants in vanadium mining area

High demand of Vanadium (V) in high-strength steel and battery manufacturing industry led to extensive V mining activity in China, and caused multi-metal pollution of soil around V mining area. To understand the phytoremediation potentials of native plants grown in V mining area, and the effect of soil properties and soil metal concentrations on toxic metal accumulations of native plants. Setaria viridis, Kochia scoparia and Chenopodium album were sampled from different sites in V mining area, soil properties, soil metal concentrations and metal accumulation amount of investigated plants were measured, bioaccumulation (BAF) and translocation (TF) efficiencies were calculated. Soil pH, cation exchange capacity (CEC) and available phosphorous (P) can significantly affect V and copper (Cu) uptake in the shoots of Setaria viridis while soil metal contents were lower than the permissible limits. Soil pH can significantly affect V accumulations in the roots and shoots of Kochia scoparia grown in slightly V polluted soils. Setaria viridis exhibited TF > 1 for moderately V and slightly chromium (Cr) polluted soils, and BAF>1 for slightly Cu contaminated soils respectively. Kochia scoparia and Chenopodium album showed TF > 1 and BAF>1 for slightly V polluted soils, respectively. Setaria viridis was practical for in situ phytoextractions of moderately V and slightly Cr polluted soils, and phytostabilization of slightly Cu contaminated soils. Kochia scoparia and Chenopodium album could be used as phytoextractor and phytostablizer in slightly V polluted soils in V mining area. Metal uptake of native plants grown in slightly multi-metal contaminated sites in V mining area can be manipulated by altering soil properties.

Physiological and anthocyanin biosynthesis genes response induced by vanadium stress in mustard genotypes with distinct photosynthetic activity

The present study aimed to elucidate the photosynthetic performance, antioxidant enzyme activities, anthocyanin contents, anthocyanin biosynthetic gene expression, and vanadium uptake in mustard genotypes (purple and green) that differ in photosynthetic capacity under vanadium stress. The results indicated that vanadium significantly reduced photosynthetic activity in both genotypes. The activities of the antioxidant enzymes were increased significantly in response to vanadium in both genotypes, although the purple exhibited higher. The anthocyanin contents were also reduced under vanadium stress. The anthocyanin biosynthetic genes were highly expressed in the purple genotype, notably the genes TT8, F3H, and MYBL2 under vanadium stress. The results indicate that induction of TT8, F3H, and MYBL2 genes was associated with upregulation of the biosynthetic genes required for higher anthocyanin biosynthesis in purple compared with the green mustard. The roots accumulated higher vanadium than shoots in both mustard genotypes. The results indicate that the purple mustard had higher vanadium tolerance.

Seasonal differences in trace element concentrations and distribution in Spartina alterniflora root tissue

The present study uses nanometer-scale synchrotron X-ray nanofluorescence to investigate season differences in concentrations and distributions of major (Ca, K, S and P) and trace elements (As, Cr, Cu, Fe and Zn) in the root system of Spartina alterniflora collected from Jamaica Bay, New York, in April and September 2015. The root samples were cross-sectioned at a thickness of 10 μm. Selected areas in the root epidermis and endodermis were mapped with a sampling resolution of 100 and 200 nm, varying with the mapping areas. The results indicate that trace element concentrations in the epidermis and endodermis vary among the elements measured, possibly because of their different chemical properties or their ability to act as micronutrients for the plants. Elemental concentrations (As, Ca, Cr, Cu, Fe, K, P, S and Zn) within each individual root sample and between the root samples collected during two different seasons are both significantly different (p < 0.01). Furthermore, this study indicates that the nonessential elements (As and Cr) are significantly correlated (p < 0.01) with Fe, with high concentrations in the root epidermis, while others are not, implying that Fe may be a barrier to nonessential element transport in the root system. Hierarchy cluster analysis shows two distinct groups, one including As, Cr and Fe and the other the rest of the elements measured. Factor analysis also indicates that the processes and mechanisms controlling element transport in the root system can be different between the nutrient and nonessential elements.

Screening of groundwater remedial alternatives for brownfield sites: a comprehensive method integrated MCDA with numerical simulation

Brownfield sites pollution and remediation is an urgent environmental issue worldwide. The screening and assessment of remedial alternatives is especially complex owing to its multiple criteria that involves technique, economy, and policy. To help the decision-makers selecting the remedial alternatives efficiently, the criteria framework conducted by the U.S. EPA is improved and a comprehensive method that integrates multiple criteria decision analysis (MCDA) with numerical simulation is conducted in this paper. The criteria framework is modified and classified into three categories: qualitative, semi-quantitative, and quantitative criteria, MCDA method, AHP-PROMETHEE (analytical hierarchy process-preference ranking organization method for enrichment evaluation) is used to determine the priority ranking of the remedial alternatives and the solute transport simulation is conducted to assess the remedial efficiency. A case study was present to demonstrate the screening method in a brownfield site in Cangzhou, northern China. The results show that the systematic method provides a reliable way to quantify the priority of the remedial alternatives.

Amendment of vanadium-contaminated soil with soil conditioners: A study based on pot experiments with canola plants (Brassica campestris L.)

We performed pot experiments with canola plants (Brassica campestris L.) to evaluate the effect of eight soil conditioners on the amendment of vanadium (V)-contaminated soil based on analysis of the growth of canola plants and the uptake, bioaccumulation, and translocation of heavy metals. Tested soil conditioners included polyacrylamide (PAM), sepiolite, humic acid (HAC), peat, sludge compost (SC), bentonite, lime, and fly ash. Results from the analysis of the growth of canola plants and the analysis of variance showed that the best soil conditioners for V-contaminated soil were 0.05-0.1 wt% PAM, 1 wt% peat, 1 wt% HAC, and 1 wt% SC; moderately effective soil conditioners included sepiolite and lime. The best combination of soil conditioners was 0.1 wt% PAM, 1 wt% HAC, and 0.15 wt% lime, in addition of 1% ZVI, which increased the biomass and height of canola plants by 1.18-fold and 59.49%, respectively. We conclude that the best combination of soil conditioners determined from this study is promising for mitigating V contamination in soil.

Isolation of vanadium-resistance endophytic bacterium PRE01 from Pteris vittata in stone coal smelting district and characterization for potential use in phytoremediation

This study investigates the V-resistant endophytic bacteria isolated from V-accumulator Pteris vittata grown on stone coal smelting district. Among all the ten isolates, the strain PRE01 identified as Serratia marcescens ss marcescens by Biolog GEN III MicroPlate™ was screened out by ranking first in terms of heavy metal resistance and plant growth promoting traits. The S. marcescens PRE01 had strong V, Cr and Cd resistance especially for V up to 1500mg/L. In addition, it exhibited ACC deaminase activity, siderophore production and high indoleacetic acid production (60.14mg/L) and solubilizing P potential (336.41mg/L). For heavy metal detoxification tests, PRE01 could specifically assimilate 97.6%, 21.7% and 6.6% of Cd(II), Cr(VI) and V(V) within 72h incubation. Despite the poor absorption of the two anions, most V(V) and Cr(VI) were detoxified and reduced to lower valence states by the strain. Furthermore, the isolate had the potential to facilitate the metals uptake of their hosts by changing heavy metal speciation. Our research may open up further scope of utilizing the endophyte for enhancing phytoextraction of vanadium industry contaminated soils.

Fate of heavy metals in vertical subsurface flow constructed wetlands treating secondary treated petroleum refinery wastewater in Kaduna, Nigeria

This study examined the performance of pilot-scale vertical subsurface flow constructed wetlands (VSF-CWs) planted with three indigenous plants, i.e. Typha latifolia, Cyperus alternifolius, and Cynodon dactylon, in removing heavy metals from secondary treated refinery wastewater under tropical conditions. The T. latifolia-planted VSF-CW had the best heavy metal removal performance, followed by the Cyperus alternifolius-planted VSF-CW and then the Cynodon dactylon-planted VSF-CW. The data indicated that Cu, Cr, Zn, Pb, Cd, and Fe were accumulated in the plants at all the three VSF-CWs. However, the accumulation of the heavy metals in the plants accounted for only a rather small fraction (0.09-16%) of the overall heavy metal removal by the wetlands. The plant roots accumulated the highest amount of heavy metals, followed by the leaves, and then the stem. Cr and Fe were mainly retained in the roots of T. latifolia, Cyperus alternifolius, and Cynodon dactylon (TF < 1), meaning that Cr and Fe were only partially transported to the leaves of these plants. This study showed that VSF-CWs planted with T. latifolia, Cyperus Alternifolius, and Cynodon dactylon can be used for the large-scale removal of heavy metals from secondary refinery wastewater.

Toxic metal tolerance in native plant species grown in a vanadium mining area

Vanadium (V) has been extensively mined in China and caused soil pollution in mining area. It has toxic effects on plants, animals and humans, posing potential health risks to communities that farm and graze cattle adjacent to the mining area. To evaluate in situ phytoremediation potentials of native plants, V, chromium, copper and zinc concentrations in roots and shoots were measured and the bioaccumulation (BAF) and translocation (TF) efficiencies were calculated. The results showed that Setaria viridis accumulated greater than 1000 mg kg^-1 V in its shoots and exhibited TF > 1 for V, Cr, Zn and BAF > 1 for Cu. The V accumulation amount in the roots of Kochia scoparia also surpassed 1000 mg kg^-1 and showed TF > 1 for Zn. Chenopodium album had BAF > 1 for V and Zn and Daucus carota showed TF > 1 for Cu. Eleusine indica presented strong tolerance and high metal accumulations. S. viridis is practical for in situ phytoextractions of V, Cr and Zn and phytostabilisation of Cu in V mining area. Other species had low potential use as phytoremediation plant at multi-metal polluted sites, but showed relatively strong resistance to V, Cr, Cu and Zn toxicity, can be used to vegetate the contaminated soils and stabilise toxic metals in V mining area.

Risk assessment and interpretation of heavy metal contaminated soils on an urban brownfield site in New York metropolitan area

In this study, soil samples were collected at 22 sites in Liberty State Park, New Jersey, in 2005, for metal enrichment and potential ecological risk assessment. The geoaccumulation index (I _geo) showed that enrichment levels of trace metals followed an order of Cu > Pb > Zn > As > Cr > Hg while the potential ecological risk factor ([Formula: see text]) indicated that the potential ecological risk of the metals was in the order of Cu > Pb > As > Hg > Zn > Cr. Among these 22 sites, this investigation identified 9 sites at moderate ecological risk, 3 sites at considerable ecological risk, and 4 sites at high ecological risk according to the potential ecological risk index (RI). Hierarchical cluster analysis (CA) of soil metal concentrations separated the study sites into four groups, which are supported by the significant difference in RI values. Geographically, three regions in the Liberty State Park brownfield site were determined based on the CA results and RI values. Subarea 1 had low ecological risk while subareas 2 and 3 had a greater potential for ecological risk. Significant correlations of Pb with Cr and Zn were observed in subareas 2 and 3, respectively. This study shows that statistical approaches coupled with a risk assessment index provide a more comprehensive interpretation of land contamination than a single approach in support of planning land redevelopment.

Nanoscale measurement of trace element distributions in Spartina alterniflora root tissue during dormancy

This paper reports a nanometer-scale investigation of trace element (As, Ca, Cr, Cu, Fe, Mn, Ni, S and Zn) distributions in the root system Spartina alterniflora during dormancy. The sample was collected on a salt marsh island in Jamaica Bay, New York, in April 2015 and the root was cross-sectioned with 10 μm resolution. Synchrotron X-ray nanofluorescence was applied to map the trace element distributions in selected areas of the root epidermis and endodermis. The sampling resolution was 60 nm to increase the measurement accuracy and reduce the uncertainty. The results indicate that the elemental concentrations in the epidermis, outer endodermis and inner endodermis are significantly (p < 0.01) different. The root endodermis has relatively higher concentrations of these elements than the root epidermis. Furthermore, this high resolution measurement indicates that the elemental concentrations in the outer endodermis are significantly (p < 0.01) higher than those in the inner endodermis. These results suggest that the Casparian strip may play a role in governing the aplastic transport of these elements. Pearson correlation analysis on the average concentrations of each element in the selected areas shows that most of the elements are significantly (p < 0.05) correlated, which suggests that these elements may share the same transport pathways.

The potential for constructed wetlands to treat alkaline bauxite-residue leachate: Phragmites australis growth

High alkalinity (pH > 12) of bauxite-residue leachates presents challenges for the long-term storage and managements of the residue. Recent evidence has highlighted the potential for constructed wetlands to effectively buffer the alkalinity, but there is limited evidence on the potential for wetland plants to establish and grow in soils inundated with residue leachate. A pot-based trial was conducted to investigate the potential for Phragmites australis to establish and grow in substrate treated with residue leachate over a pH range of 8.6-11.1. The trial ran for 3 months, after which plant growth and biomass were determined. Concentrations of soluble and exchangeable trace elements in the soil substrate and also in the aboveground and belowground biomass were determined. Residue leachate pH did not affect plant biomass or microbial biomass. With the exception of Na, there was no effect on exchangeable trace elements in the substrate; however, increases in soluble metals (As, Cd and Na) were observed with increasing leachate concentration. Furthermore, increases in Al, As and V were observed in belowground biomass and for Cd and Cr in aboveground biomass. Concentrations within the vegetation biomass were less than critical phytotoxic levels. Results demonstrate the ability for P. australis to grow in bauxite-residue leachate-inundated growth media without adverse effects.

Heavy-metal-contaminated industrial soil: Uptake assessment in native plant species from Brazilian Cerrado

Plants of the Cerrado have shown some potential for restoration and/or phytoremediation projects due to their ability to grow in and tolerate acidic soils rich in metals. The aim of this study is to evaluate the tolerance and accumulation of metals (Cd, Cu, Pb, and Zn) in five native tree species of the Brazilian Cerrado (Copaifera langsdorffii, Eugenia dysenterica, Inga laurina, Cedrela fissilis, Handroanthus impetiginosus) subjected to three experiments with contaminated soils obtained from a zinc processing industry (S1, S2, S3) and control soil (S0). The experimental design was completely randomized (factorial 5 × 4 × 3) and conducted in a greenhouse environment during a 90-day experimentation time. The plant species behavior was assessed by visual symptoms of toxicity, tolerance index (TI), translocation factor (TF), and bioaccumulation factor (BF). C. fissilis has performed as a Zn accumulator by the higher BFs obtained in the experiments, equal to 3.72, 0.88, and 0.41 for S1, S2, and S3 respectively. This species had some ability of uptake control as a defense mechanism in high stress conditions with the best behavior for phytoremediation and high tolerance to contamination. With economical and technical benefits, this study may support a preliminary analysis necessary for using native tree species in environmental projects.

Damage suffered by swamp morning glory (Ipomoea aquatica Forsk) exposed to vanadium (V)

To elucidate the physiological and morphological responses generated by vanadium (V) in plants, hydroponic culture experiments were performed with swamp morning glory (Ipomoea aquatica Forsk) exposed to 0 mg L(-1) to 2.50 mg L(-1) pentavalent V [V(V)] in Hoagland nutrient solutions. The concentration of chlorophyll a, chlorophyll b, and carotene peaked at a V(V) concentration of 0.05 mg L(-1) and gradually decreased at higher V(V) concentrations. Similarly, the plant biomass was stimulated at low levels of V(V) and was inhibited when V(V) concentrations exceeded 0.1 mg L(-1). Pentavalent V had negative effects on the uptake of phosphorus (P) by roots, shoots, and leaves. The biological absorption coefficients of V of the roots were higher than those of the aerial parts. Under low concentrations of V(V) exposure, the predominant species of V in the aerial parts was tetravalent V [V(IV)], whereas V(V) became more prevalent when concentrations of V(V) in the solution was higher than 0.50 mg L(-1). In the roots, however, the concentrations of V(V) were always higher than those of the V(IV), except in the control group. Organelles in the V(V)-treated leaves were distorted, and the periplasmic space became wider. These results indicate V(V) has concentration-dependent effects on the physiological properties of swamp morning glory, whereas the plant has the ability to develop self-protective function to adapt to the toxicity of V(V).

Uptake and speciation of vanadium in the rhizosphere soils of rape (Brassica juncea L.)

The response of rape (Brassica juncea L.) to different vanadium (V) speciation in rhizosphere soils was investigated in pot experiments using an agricultural soil containing 147 mg V kg(-1) supplemented with 0-500 mg V kg(-1) of pentavalent V [V(V)] and a mining soil containing 774 mg V kg(-1). Tetravalent V [V(IV)] accounted for 76.1 and 85.9 % of total V in the untreated agricultural soil and mining soil, respectively. The proportion of both V(V) and water-extractable V increased with increasing concentrations of V(V) in the agricultural soil. The growth of rape substantially reduced the concentrations of V(V) but not V(IV) in the rhizosphere soil, suggesting that V(V) was actively involved in the soil-rape interaction of V. Both soil V(V) and water-extractable V were negatively related to the total rape biomass, but were positively correlated with the concentration of root V. No such relationships were found for total V and soil V(IV). Together, these results indicate that soil V(V) and water-extractable V might better reflect the toxicity of V in soils than total V and soil V(IV). Rape accumulated V in the sequence: roots > > stem > leaf > seed. As indicated by the remarkably low root bioconcentration factor of V(V) (0.41-7.24 %), rape had a lower ability to accumulate V than other plants reported in the literature (14.6-298 %). Only a small fraction of V in rape roots was translocated to the aboveground organs (the translocation factor was 3.57-46.9 %). No V was detectable in seeds in the soils at 147 and 197 mg V kg(-1), and no seed was produced in the soils at higher V concentrations. Thus, the risk of V intake by humans via the consumption of rapeseed-based foods under normal conditions is considered to be lower than that of other plants.

Antimony in the soil-water-plant system at the Su Suergiu abandoned mine (Sardinia, Italy): strategies to mitigate contamination

This study was aimed to implement the understanding of the Sb behavior in near-surface environments, as a contribution to address appropriate mitigation actions at contaminated sites. For this purpose, geochemical data of soil (8 sites), water (29 sites), and plant (12 sites) samples were collected. The study area is located at Su Suergiu and surroundings in Sardinia (Italy), an abandoned mine area heavily contaminated with Sb, with relevant impact on water bodies that supply water for agriculture and domestic uses. Antimony in the soil horizons ranged from 19 to 4400 mg kg(-1), with highest concentrations in soils located close to the mining-related wastes, and concentrations in the topsoil much higher than in the bedrock. The Sb readily available fraction was about 2% of the total Sb in the soil. Antimony in the pore water ranged from 23 to 1700 μg L(-1), with highest values in the Sb-rich soils. The waters showed neutral to slightly alkaline pH, redox potential values indicating oxidizing conditions, electrical conductivity in the range of 0.2 to 3.7 mS cm(-1), and dissolved organic carbon ≤2 mg L(-1). The waters collected upstream of the mine have Ca-bicarbonate dominant composition, and median concentration of Sb(tot) of 1.7 μg L(-1) (that is total antimony determined in waters filtered through 0.45 μm), a value relatively high as compared with the background value (≤0.5 μg L(-1) Sb) estimated for Sardinian waters, but below the limits established by the European Union and the World Health Organization for drinking water (5 μg L(-1) Sb and 20 μg L(-1) Sb, respectively). The waters flowing in the mine area are characterized by Ca-sulfate dominant composition, and median concentrations of 7000 μg L(-1) Sb(tot). Extreme concentrations, up to 30,000 μg L(-1) Sb(tot), were observed in waters flowing out of the slag materials derived from the processing of Sb-ore. The Sb(III) was in the range of 0.8 to 760 μg L(-1) and represented up to 6% of Sb(tot). In the waters collected downstream of the mine, median Sb(tot) concentrations decreased as distance from the mine area increases: 1300 μg L(-1) Sb(tot) in the stream Rio Ciurixeda at 3 km distance, and 25 μg L(-1) Sb(tot) in the main River Flumendosa 15 km further downstream. Attenuation of Sb contamination was mainly due to dilution. Results of modeling, carried out by both EQ3 and Visual MINTEQ computer programs, suggest that sorption of dissolved Sb onto solid phases, and/or precipitation of Sb-bearing minerals, likely give a minor contribution to attenuation of Sb contamination. The slightly alkaline pH and oxidizing conditions might favor the persistence of inorganic Sb(V)-bearing species at long distance in the studied waters. Concentrations of Sb in the plants Pistacia lentiscus and Asparagus ranged from 0.1 to 22 mg kg(-1), with maximum values in plants growing very close to the mining-related wastes. The P. lentiscus grows well on the soils highly contaminated with Sb at Su Suergiu and might be used for revegetation of the Sb-rich heaps, thus contributing to reduce the dispersion of contaminated materials. Major effects of contamination were observed on the water bodies located downstream of the Su Suergiu abandoned mine. The maximum load (16.6 kg Sb per day) to the Flumendosa, the main aquatic recipient, was observed after heavy rain events. Therefore, priorities of mitigation actions should be focused on minimizing the contact of rain and runoff waters on the heaps of mining wastes.