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Titanium gypsum is a solid waste produced by sulphuric acid titanium dioxide producers when they neutralise the waste acid with calcium method, and the annual emission is quite large, causing relatively large environmental problems. Improving the comprehensive utilisation of titanium gypsum is the key to solving the problem of the large increase of titanium gypsum. This paper reviews the current beneficial applications of titanium gypsum, analyses the practical applications of titanium gypsum in three fields: extraction of useful material, construction material, and soil amendment, and the impact of these applications on the environment, in order to provide a basis for better understanding and application of titanium gypsum. [ABSTRACT FROM AUTHOR]

Tobacco exhibited a relatively strong environmental adaptability, and it is appealing to explore its vanadium stress-responsive characteristic. An indoor pot experiment with tobacco cultivated in soil with respectively 0 (control), 75, 150, 300, 600, and 900 mg kg−1 of exogenous pentavalent vanadium V(V) and in vanadium-rich soil from a mining area with 385.6 mg kg−1 of vanadium (marked as M0) was conducted. Results showed that tobacco growth was significantly (p< 0.05) inhibited at all treatments versus control. The seedlings could not survive at 900 mg kg−1 vanadium treatment. Vanadium was mainly concentrated in the root. Tobacco showed a relatively high vanadium bioconcentration capability (0.19 − 0.74) and a low translocation capability (0.02 − 0.03) in soil with exogenous vanadium addition treatments. Contrarily, at the control and M0 treatment, tobacco exhibited a low vanadium bioconcentration capability (0.06 − 0.08) and a relatively high translocation capability (0.06 − 0.09). For M0 treatment, the high percentage of vanadium in the residual fraction was also conducive to tobacco establishment in vanadium-loaded surroundings. Overall, tobacco showed the potential to colonize vanadium-rich soil. In soils after growing tobacco, Proteobacteria was the most abundant microbial community of the rhizospheric soil, followed by Actinobacteria. [ABSTRACT FROM AUTHOR]

The continuously elevated concentration of vanadium (V) in the environment is of great concern due to its potential risks to organisms. Microbial reduction is considered a green way to remediate the V-contaminated sites. This study presents the first demonstration of Pseudomonas balearica , a bacterium flourishing in vanadium-titanium magnetite tailings, exhibiting the capacity to reduce pentavalent V [V(V)]. We found that P. balearica exhibited strong tolerance to high V(V) levels, despite lacking known V(V)-reducing genes. After 48 h of incubation, the reduction rates of V(V) by P. balearica under 0.5 mM and 10 mM V(V) stress reached 81.1% and 60.6%, respectively. The phosphorus group and carboxyl group on the bacterial cell surface contributed to V(V) binding and reduction. Both extracellular and intracellular V(V) reduction was significantly facilitated by many critical V-induced differentially expressed genes (DEGs) encoding nitrate/nitrite reductases, ABC transporters, NADH, and c-type cytochromes. In addition, up-regulation of DEGs associated with reactive oxygen species (ROS)-scavenging enzymes, such as glutathione peroxidase, superoxide dismutase, and catalase, was observed as a protective response to oxidative stress triggered by V(V). Moreover, some up-regulated DEGs (ureC , ureE , ureA , and ureG) encoding urease subunit or urease accessory proteins significantly enriched in the nickel cation binding pathway, indicating that P. balearica may be resistant to Ni stress by regulating urease activity. This study will help to more thoroughly elucidate the characteristics and mechanisms of V(V) reduction by microbes and provide a native bacterium flourishing in tailings for potential bioremediation of V pollution and bioleaching of V-sources. [Display omitted] • V(V) reduction mechanisms in P. balearica were reported for the first time. • P. balearica showed a high V(V) reduction rate of 81.1% at 0.5 mM V(V) treatment. • Phosphorus group and carboxyl group contributed to V(V) binding and reduction. • Many V-induced DEGs promoted extracellular and intracellular V(V) reduction. • Nitrate/nitrite reductases and cytochrome c were involved in V(V) reduction. [ABSTRACT FROM AUTHOR]

[Display omitted] Microplastics (MPs), polymer particles capable of accumulating heavy metals from ambient medias, have been widely found in agriculture and pasture soils. Through the consumption of MPs in soils, heavy metals adsorbed on MPs can be transported into ruminant digestive guts. To explore the behavior of Cd loaded MPs in ruminant digestive system, we initially established a ruminant digestive in-vitro method (RDM) that simulates the rumination cycle between mouth and rumen to evaluate the release rates of Cd on 4 most commonly used undegradable MPs (PE, PP, PVC, and PS) and a biodegradable MP (PLA). After 120 h of adsorption, the Cd adsorption capabilities by 5 MPs ranged from 0.23 μg/g to 2.45 μg/g. Through RDM, all tested Cd loaded MPs released high proportions of Cd with release rates from 21.5% to 41.8%, where PLA showed the highest Cd release rate. Cadmium was mainly released in rumen and abomasum phases, and the rumination cycle between mouth and rumen can affect the Cd release from MPs. The present study provides a new view on the environmental hazard of heavy metal and MP pollution that their co-exposure to ruminants should be taken into account. [ABSTRACT FROM AUTHOR]

Abstract Oral bioaccessibility of vanadium(IV) and vanadium(V) in soil, dust and concentrate fines from a vanadium titanomagnetite mining region was assessed by a whole digestive system in-vitro scheme. The scheme including the addition of sweat and the large intestinal digestion was used to estimate the oral bioaccessibility of vanadium(IV) and vanadium(V) in the whole digestive system for the first time. Higher oral bioaccessibility of vanadium(IV) and vanadium(V) was determined in gastric and small intestinal phases demonstrating that their major roles for vanadium digestion and absorption. The decreasing order of the oral bioaccessibility of vanadium(IV) and vanadium(V) in each digestive phase was stomach, small intestine, large intestine and mouth. Higher oral bioaccessibility of vanadium(V) in the whole digestion indicated its higher risk potential for human than vanadium(IV). Lower oral bioaccessibility of vanadium(IV) and vanadium(V) determined in bionic digestion illustrated detoxicity potential of human body for ingested vanadium. Compared with soil and dust, higher digestion rate of vanadium in vanadium titanomagnetite concentrate fines indicated its higher risk for human, especially for mining workers. Based on vanadium oral bioaccessibility, hazard quotients of the vanadium were much less than the critical level suggested for no non-carcinogenic risks to the populations surrounding the sampling sites. Indeed, compared with the estimations based on total vanadium content, the incorporation of oral vanadium bioaccessibility into risk assessments could give more realistic information. Graphical abstract Image 1 Highlights • Determine vanadium bioaccessibility (VB) by a whole digestive system in-vitro model. • Sweat had insignificant influence (p > 0.05) on VB in mouth. • Most bioaccessible vanadium was observed in stomach and small intestine. • Digestive enzymes had opposite effect on VB in different digestive phases. • Bioaccessible vanadium(IV) was lower than vanadium(V) in digestive system. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Geochemical properties and microbial composition of tailings were detected. • Highlight the importance of dehydration treatment of tailings before stockpiling. • Proteobacteria, Actinobacteria, and Chloroflexi were major phyla found in all tailings. • Sulfuricurvum and Geobacter were biomarkers in wet tailings with remediation potential. • Bioavailable As was the strongest determinant of the tailing microbial community. [ABSTRACT FROM AUTHOR]

The discharge of effluents and sludge from the leather industry is raising a growing concern. However, the mobility and hazards of tannery organic pollutants in soils are easily ignored. Herein, soil column leaching experiments were conducted using typical tannery organic pollutants glutaraldehyde (GA) and two azo dyes [Acid Red 73 (AR 73) and Direct Blue 6 (DB 6)]. Under simulated rain conditions, the leaching behavior of GA and organic dyes showed significant differences even though they were both water-soluble organic pollutants. AR 73 and DB 6 could be detected in the leachates throughout 7 leaching events for 28 days and in soil columns after leaching, while GA failed to be detected in both leachates and soil columns, indicating that AR 73 and DB 6 with more complex molecular structures had poorer degradability than GA under the condition of similar initial concentrations. The results demonstrated that the azo dyes AR 73 and DB 6 used in the experiment were more likely to cause adverse effects on soil and underground water under the condition of the covering thickness of dyes ≥ 0.5 mm on soil, and thus possessed higher environmental risk than GA. This study is also conducive to further evaluating the risk of tannery contamination sites. [ABSTRACT FROM AUTHOR]

Stabilization technique is regarded effective to control heavy metal pollution in soil. Traditional stabilizers have raised concerns about soil acidification/alkalization, or the stable effectiveness in a long-term. To stabilize vanadium (V) in calcareous purple soil in an environmentally friendly way, Na-bentonite (Na–B) modified by tea polyphenol (TP-B), by FeSO 4 (Fe–B), and by TP and FeSO 4 (TP-Fe-B) were prepared, characterized and assayed. The tea polyphenol modification loaded –CH 2 on TP-B and TP-Fe-B, and ferrous modification introduced rozenite to Fe–B and TP-Fe-B, which supplied reaction sites to V. The effects of stabilizer dosage, soil moisture, and initial V concentration in soil were considered to ascertain the optimum stabilization conditions. Applying 5 wt% Fe–B into the 696.63 mg V/kg soil at 60% field water capacity soil yielded stabilization rates of 19.1%, 37.7% and 20.5% for water-extractable V, bioavailable V, and pentavalent V, respectively. Further study was conducted to assess the stable period of the passivation effect and the stability of the passivation effect under acid rain. The stabilization effect remained functional for at least 4 weeks after TP-B, Fe–B, and TP-Fe-B application. Notably, adding Fe–B could reduce the risk of V transfer from soil into the aquatic environment under acid rain. However, Fe–B resulted in a decrease in soil organic matter and alkali-hydrolyzed nitrogen, thus fertilization should be considered. These results proved that Fe–B was a potential stabilizer for V contaminated soil even under acid rainfall. Image 1 • An eco-friendly and effective vanadium(V) stabilization method was put forward. • TP and FeSO 4 yielded different properties of Na–B. • TP-B, Fe–B, and TP-Fe-B reduced the mobile and bioavailable V in soil. • Fe–B reduced the risk of V transferred from soil into water under acid rainfall. • TP-Fe-B increased fertility of V contaminated soil under acid rainfall. [ABSTRACT FROM AUTHOR]

Applying biodegradable chelating agents to assist in phytoremediation is a promising method to increase the remove efficiency of metal pollutants from contaminated soils. The effects of biodegradable chelating agents on improving the phytoremediation capacity in uranium (U) and cadmium (Cd) contaminated soil was investigated using sunflowers, which were grown in pots containing soil with U and Cd added at 15 mg/kg. After 2 months of growth, citric acid (CA), oxalic acid (OA) and ethylenediamine disuccinate (EDDS) at various concentrations (0, 2.5, 5.0 and 7.5 mmol/kg) were applied. The results showed that plant biomass decreased by 12.12% for shoot and 15.74% for root under U and Cd combined stress. Meanwhile, chelating agent treatments, especially with EDDS, enhanced U and Cd stress in plants by decreasing biomass, inhibiting photosynthesis, and increasing malondialdehyde and H 2 O 2 levels. The U uptake of plants after CA addition was significantly greater than that after OA and EDDS addition. Nevertheless, EDDS addition has better effects on Cd uptake than CA and OA addition. U and Cd remove efficiencies reached the maximum following the application of 5.0 mmol/kg CA and 5.0 mmol/kg EDDS, which were 177.48% and 181.51% higher than that of the control, respectively. Furthermore, the bioavailable U content in soils treated with CA were higher than that in soils treated with EDDS, whereas bioavailable Cd content significantly increased due to EDDS addition. These results suggest that biodegradable chelating agents have significant effects on improving the U and Cd phytoremediation potential of sunflowers. • EDDS enhanced the adverse effects of U and Cd in sunflower. • CA and EDDS effectively increased the uptake and translocation of U and Cd. • CA significantly promoted U bioavailability in soil-plant system. EDDS has better effects on mobilizing Cd in the soil. • CA and EDDS improved the phytoremediation efficiency of sunflower. [ABSTRACT FROM AUTHOR]

Municipal solid waste incineration (MSWI) fly ash is complex in composition and contains large amounts of heavy metals. To investigate the effects of different passivating agents on Cd, Pb, Cr, Ni and Zn in different types of fly ash, 7 reagents were selected as passivating agents, including 3 inorganic reagents (Na 2 S, Na 3 PO 4 , NaH 2 PO 4) and 4 organic reagents (SDD, DDTC, TMT, thiourea). The results showed that at low addition levels, sulfur-containing organic chemicals and phosphates were more effective in chelating these metals in both grate furnace incineration fly ash (GF FA) and circulating fluidised bed incineration fly ash (CFB FA), while Na 2 S was more effective in chelating heavy metals in CFB FA. In addition, agents containing -N-C S groups showed better chelation of heavy metals in GF FA, while heavy metals in CFB FA were more affinity to agents containing -SH groups. The ternary compound TMT-NaH 2 PO 4 -SDD (m 1 :m 2 :m 3 = 2:3:1) was an excellent chelating agent for Pb, Cd in the GF FA, and TMT-Na 2 S-thiourea (m 1 :m 2 :m 3 = 2:1:3) was a suitable chelating agent for these metals in CFB FA. The chelation rate of Cd and Pb after the treatments mixed ternary reagents was above 99%, and the leaching amount was much lower than the limit value of pollution control standards for domestic landfills. Moreover, under different pH leaching conditions, the leaching concentrations of Cd and Pb in the fly ashes treated with the ternary mixture were lower than the standard limits. In general, the ternary compound can effectively chelate heavy metals in fly ash, which provides a reference for selecting a suitable stabilizer combination for heavy metal in fly ash. [Display omitted] [ABSTRACT FROM AUTHOR]

Soils in large areas of China are enriched in fluorine (F). The present study analyzed F concentrations in cultivated soil, water, chemical fertilizer, and human hair, and metal concentrations in soils from an endemic fluorosis area in Southwest, China. In order to reveal the effects of industry on F concentration in the environment, 3 towns mainly with agriculture production and another 3 towns with developed phosphorus chemical industry in a same city were selected for sample collection. The total F concentrations of the 277 surface agricultural soil samples were 378.79–1576.13 μg g−1, and F concentrations of nearly 95% of the soil samples were higher than the Chinese average topsoil F concentration (480 μg g−1). Only a small fraction (0.75%) of total F was water soluble. The average total F, water soluble F, Ca, Cr, Fe, K, Mn, Rb, and Sr concentrations in soil samples from towns with intensive industry were higher than those from towns mainly with agriculture. Significant correlations were found between soil pH with total F (p < 0.01) and with water soluble F concentration (p < 0.1). Low F concentrations (<0.5 mg L−1) were found in irrigation water, well water and tap water in a town where the industry is dense. The phosphorus fertilizer and compound fertilizer had hundreds of times of contribution to soil F increment than the nitrogen fertilizer and potassium fertilizer. Nearly half percent of F in the human hair samples was of exogenic origin. Based on soil ingestion pathway, the health risk for adults exposure to F in soils was acceptable, however, F may pose possible health risks to children in high F concentration areas. • Soil total F concentration was higher in industrial than in agricultural towns. • P and compound fertilizers contributed more to soil F than N and K fertilizers. • F in human hair of industrial towns was higher than that of agricultural towns. • F may pose possible health risks to children in high soil F concentration areas. [ABSTRACT FROM AUTHOR]

• Microplastics (MPs) released more Cr in the in-vitro digestive model than in fresh water. • Gastric phase aroused the most bioaccessible Cr(VI) and Cr(III). • Cr on degradable MP was more bioaccessible than Cr on nondegradable MPs. • The Cr exposure via MP consumption was estimated for different human groups. • Cr on degradable MP may pose higher noncarcinogenic risks to human. Microplastics (MPs), polymer particles capable of adsorbing heavy metals from ambient environment, have been found in diverse human food resources. Through the consumption of MPs, heavy metals adsorbed on MPs might be transported into human body. This study aims to explore the behavior of heavy metal-contaminated MPs in human digestive system which is not previously researched. Firstly, a chromium (Cr) adsorption/desorption study was conducted with four commonly used nondegradable MPs [polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS)] as well as one degradable MP (polylactic, PLA). Then, the whole digestive system in-vitro method (WDSM), a systematic model including mouth, gastric, small intestine, and large intestine digestive phases, was conducted on the Cr-loaded MPs. Additionally, the bioaccessibilities and hazard quotients (HQs) of Cr(VI) and Cr(III) were evaluated. Among five MPs, although PLA showed the weakest adsorption capacity for Cr, the Cr(VI) bioaccessibilities for PLA reached the highest values of 19.9%, 15.6% and 3.9% in gastric, small intestinal and large intestinal phases, respectively. The bioaccessibilities of Cr(VI) in gastric phase were significantly higher than those in other phases, while no Cr release from MPs was detected in the mouth phase. In gastric phase, the bioaccessibilities of Cr(VI) were significantly higher than those of Cr(III) in the gastric phase, and both of them approached to a similar level in intestinal phases. In the WDSM, the HQs of Cr(VI) and Cr(III) on MPs were lower than the critical level for both adults and children. Based on the measured bioaccessibilities, the maximum daily total Cr intake for different human groups (female children, male children, female adults and male adults) through MP consumption was estimated from 0.50 to 1.18 μg/day. In general, the five tested MPs were potential to serve as Cr vectors in the WDSM. [ABSTRACT FROM AUTHOR]

• Determine F bioaccessibility by Biomimetic Whole Digestion-Plasma in-vitro Method. • More bioaccessible F was determined in small intestine and plasma. • High occupational exposure risk of F to local farmers should be concerned. • Same factor may not be equal in effects on F bioaccessibility and exposure risk. Due to potential adverse effects of excessive fluorine (F), interests regarding considerable accumulation of F in agricultural soils from application of fertilizers are increasing continually. However, less detailed information of hazard and risk of F in fertilizers to human directly by hand-to-mouth pathway can be obtained. Herein, the bioaccessibility of F (F bio) in fertilizers is determined by Biomimetic Whole Digestion-Plasma in-vitro Method (BWDPM), which is developed to detect the behaviour of bioaccessible F in both the whole digestive system and plasma for the first time. Observations of higher F bio in small intestinal phases (4.35–56.33%), large intestine (1.01–40.52%) and plasma (8.07–66.70%) yielded them as the major phases which are faced with higher exposure risk of F. Compared with phosphate fertilizer, more bioaccessible F was observed in compound fertilizer. Some studied factors, such as sweat and food, yield insignificant influences on F bio , whereas can affect the exposure estimations of F considerably. Exposure risks based on F bio of fertilizers should be highly concerned, especially the occupational exposure to local farmers. In a word, more explicit and realistic information of the potential risk of F on human health could be obtained by the introduction of F bio. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxalic acid enhanced the SMX removal by heterogeneous V 2 O 3 /percarbonate process. • •OH was the main precursor of CO 3 •- and O 2 •-. • Intramolecular electron transfer process was involved in the generation of •OH. • Oxalic acid restricted the conversion of •OH to CO 3 •- and O 2 •-. Sewage disposal technology in advanced oxidation processes (AOPs) should be enriched for providing more options for practical application. Herein, degradative and mechanistic investigation of heterogeneous V 2 O 3 -activated sodium percarbonate (SPC) process was implemented in the presence of oxalic acid (OA). The experimental results indicated a strong dependency of sulfamethoxazole (SMX) degradation on SPC dosage and a wide adaptability to the ambient pH in V 2 O 3 /SPC/OA system. Efficient removal of SMX in water reached 93.4 % within 10 min at the initial presence of 0.1 g/L V 2 O 3 and 2 mM SPC. Mechanistic experiments revealed that •OH played an indispensable role in SMX degradation, which partially dominated the degradation process and partially was the main precursor of CO 3 •- and O 2 •-. Moreover, except for the single electron transfer from low-valence state of vanadium (V) species to SPC, the intramolecular electron transfer process from –OOH ligand of V complex to hydrogen peroxide (H 2 O 2) also participated in the generation of •OH. Additionally, the introduction of OA could provide a complex, transient acidic and reductive condition for facilitating the SMX removal process. On the other hand, the addition of OA restricted the conversion of •OH to CO 3 •- and O 2 •-. Zeolite was employed to absorb the V species in the aqueous solution after the reaction and the residual vanadium concentrations were <2 mg/L. The existence of HPO 4 2-, CO 3 2– and humic acid exerted severe inhibition on the decontamination of SMX, and F- and NO 3 – exerted slight suppression, whereas the existence of Cl- and SO 4 2- did not show conspicuous impairment. This work filled the gap of decontamination performance of SMX in vanadium based heterogenous SPC system and deepened the understanding of the application of reductant. [ABSTRACT FROM AUTHOR]

Vanadium (V) is a widely distributed and potentially dangerous pollutant in soils. However, the extraction methods for bioavailability of V in soils have not been unified. This study focused on the assessment of BCR sequential and single extraction (8 extractants) methods to predict potential bioavailability of V in the tailing and soils. The total V concentration in the soil samples was 167.43 ± 14.92 mg·kg–1, and the total V concentration was 239.93 mg·kg–1 in the tailing. The available V (acid-soluble, reducible, and oxidizable phases) percentage extracted by BCR sequential extraction was low, which was 0.19–0.82%, 0.27–5.78% and 4.37–10.5% in the soils, respectively. Meanwhile, the content of V fractions in the tailing was 0.56% (acid soluble), 1.22% (reducible) and 4.37% (oxidizable). The residual fraction of V was a predominant ingredient in the soils (83.3–93.9%) and tailing (93.9%). Compared with the soil samples, the tailing sample extracted by single extractants has a lower available V content, which was 2.3% (DCB), 1.32% (HCl), 1.66% (HNO3) and 0.22% (C6H8O7) lower than the available V content in the soil samples, respectively. Furthermore, the correlation between soil properties and available V contents also discussed in this study. The V extracted by DPTA and C6H8O7 exhibited good correlation with the total V content and potential bioavailability of V extracted by BCR in the soils, suggesting that DPTA and C6H8O7 single extraction method might be an alternative to BCR sequential extraction to extract bioavailability of V in the soils. In addition, the potential ecological risks of V can not be ignored in this study area. [ABSTRACT FROM AUTHOR]

Vanadium (V) is a widely distributed and potentially dangerous pollutant in soils. However, the extraction methods for bioavailability of V in soils have not been unified. This study focused on the assessment of BCR sequential and single extraction (8 extractants) methods to predict potential bioavailability of V in the tailing and soils. The total V concentration in the soil samples was 167.43 ± 14.92 mg·kg–1, and the total V concentration was 239.93 mg·kg–1 in the tailing. The available V (acid-soluble, reducible, and oxidizable phases) percentage extracted by BCR sequential extraction was low, which was 0.19–0.82%, 0.27–5.78% and 4.37–10.5% in the soils, respectively. Meanwhile, the content of V fractions in the tailing was 0.56% (acid soluble), 1.22% (reducible) and 4.37% (oxidizable). The residual fraction of V was a predominant ingredient in the soils (83.3–93.9%) and tailing (93.9%). Compared with the soil samples, the tailing sample extracted by single extractants has a lower available V content, which was 2.3% (DCB), 1.32% (HCl), 1.66% (HNO3) and 0.22% (C6H8O7) lower than the available V content in the soil samples, respectively. Furthermore, the correlation between soil properties and available V contents also discussed in this study. The V extracted by DPTA and C6H8O7 exhibited good correlation with the total V content and potential bioavailability of V extracted by BCR in the soils, suggesting that DPTA and C6H8O7 single extraction method might be an alternative to BCR sequential extraction to extract bioavailability of V in the soils. In addition, the potential ecological risks of V can not be ignored in this study area. [ABSTRACT FROM AUTHOR]

Vanadium (V) is a toxic metal, which dominantly exists as V5+ in an aquatic environment. Rice straw, which is an abundant agricultural by-product throughout China was used to treat V5+ containing wastewater as an adsorbent after phosphoric acid treatment. The effects of initial V5+ concentration, solution temperature, pH and reaction time on V removal by phosphoric acid modified rice straw (AcM) were systematically assessed. A pH range of 2.0–3.0 was favorable for V removal and the adsorption capacity of V by AcM increased with elevated solution temperature. The maximum adsorption capacity for water containing 500 mg V5+ L−1 was 24.70 mg V g−1 dry matter under the optimum operation (3.33 g L−1 AcM, pH = 2.0, 50 °C, and 200 rpm for 4 h). Adsorption experiment data fitted well to pseudo-second-order kinetic and Langmuir adsorption isotherm models. In the presence of coexisting ions, Na+, Cu2+, NO3− and Cl− had no significant (P > 0.05) effect on V removal. These results indicated that AcM derived from agricultural waste was effective to remove V5+ from aqueous solution. [ABSTRACT FROM AUTHOR]

Microplastics have significant implications for global ecosystems. The microplastic distribution, types, sources, and quantified microplastic-heavy metal synergistic pollution in agricultural soil in Chengdu, China were analyzed. The microplastics were detected in all soil samples collected from 103 sites, with concentrations ranging from 1333 to 15067 particle kg−1. The abundance of microplastics in grassland (12,667 ± 3394 particle kg−1) was more than twice higher than that in open field, vegetable field, orchard, and woodland. The main morphological types of microplastics included fibers, films, and granules (all "3-Dimensional" microplastics), with the colors red, blue, and transparent. Granular and fiber microplastics were predominantly in particles < 500 mm, while film microplastics were uniformly distributed at all sizes. The plastic compositions were mainly polypropylene and polyethylene plastics, accounting for 20.73% and 27.90% of the soil microplastic, respectively. Agricultural plastic applications and irrigation water were the sources of soil microplastics. The concentration of Cd, Cr, and Cu in the microplastics was strongly correlated with the corresponding concentration in the soils (p < 0.01), and the microplastic-heavy metal synergistic pollution might deteriorate the soil environment. The results of soil TOC measurements were influenced by microplastics in the soil. The results provide important data for the characteristics of microplastics in the agroecosystem. [Display omitted] • Microplastics are widespread in agricultural fields in Chengdu, China. • The highest MPs abundance is in grassland among the five cultivation modes. • The main sources of soil MPs are varied among different cultivation modes. • Cd, Cr, and Cu content in soil and in microplastics are positively correlated. • Microplastics may influence the results of soil TOC measurements. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) has been identified as a very toxic heavy metal, which is widely present in the environment due to natural and anthropogenic emissions. Currently, in China, slight pollution of cultivated land is widespread and Cd is one of the top ranked inorganic pollutants in soils, which results in a great impact on the development of the economy and society. Therefore, there is an urgent need to develop an efficient and economical method to remediate Cd-polluted soil. This study focused on the development of new kinds of immobilizing soil amendments for the remediation of Cd-polluted soil. In addition, the immobilization capability of zinc (Zn) which may lead to increased toxicity of Cd was also investigated. The amendments, nanoiron-nanohydroxyapatite, nanoalumina-nanoiron and nanohydroxyapatite-nanoalumina, were prepared by the pairwise mixing of three raw materials: nanohydroxyapatite (nHAP), nanoiron (nFe) and nanoalumina (nAl2O3). The application rate, mixing ratio and pH of the amendments were studied to determine the optimal application conditions of the amendments. The results showed that, compared with the single materials of nHAP, nFe and nAl2O3, the immobilized efficiencies of Cd and Zn in soils by the pairwise mixed amendments were both significantly (p < 0.05) increased. Optimal immobilization rates of both Cd and Zn of water-soluble and available fractions were above 97.0%. Scanning electron microscopy illustrated a more uniform mixture can be obtained by wet-mixing compared with a dry-mixing method for nFe-nHAP and nHAP-nAl2O3, and the uniform mixture of nAl2O3-nFe can be obtained by both dry- and wet-mixing methods. Fourier-transform infrared analysis demonstrated that the mixed amendments retained the good capability of nHAP, nFe and nAl2O3 for the stabilization of Cd and Zn in soil. Generally, 4-8% application amount, 4:1 mixing ratio of nFe/nHAP, nAl2O3/nFe and nHAP/nAl2O3, respectively, and neutral or slightly acidic pH of the amendments were optional for the remediation of the studied soil. The order of the three raw nanomaterials that affected on the stabilization capacity of the pairwise mixed amendments was nAl2O3 > nFe > nHAP. [ABSTRACT FROM AUTHOR]

Vanadium (V) is widely used industrially, and plays an important role in the biosphere. Sensitive and reliable analytical methods to determine V in various kinds of samples are of extensive interest. Mainly two spectrophotometric methods developed in the last decade are discussed, namely complex formation methods and catalytic methods. The former is based on either oxidation or reduction of V leading to coloured complexes with proper reagents; they are applicable to determination of V at the mg L−1 level. Catalytic methods are based on the ability of V to catalyse the oxidation of various organic dyes and are applicable to determination at the μg L−1 level. Both methods are used for determination of V in environmental and biological samples. [ABSTRACT FROM AUTHOR]

Studies on Vanadium (V) adsorption in aqueous systems employing biomaterials friendly to the environment are rare. This study investigated the adsorption performance of the living and non-living Chlorella vulgaris (C. vulgaris) for V from aquatic systems. Vanadium inhibited the growth of living C. vulgaris. The results of isothermal equations showed that the non-living C. vulgaris biomass was favourable for V adsorption. At 400 mg L−1 V, 50 mg algae biomass, 40°C, and 0.01 M ionic strength for 24 h, the maximum adsorption capacity reached 94.00 mg g−1. The results of the kinetic studies indicated that chemisorption dominated the V adsorption process. Analysis on the surface of non-living C. vulgaris biomass revealed that hydroxyl groups, carboxylate groups, amide groups, aromatic carbons, and organic halogenated hydrocarbon groups played crucial roles in V biosorption. Vanadium was bound to the active sites on the surface of C. vulgaris through ion exchange action as opposed to redox reaction. Desorption experiments were conducted by eluting the non-living C. vulgaris biomass with 1 M NaOH solution, and the maximum desorption rate of V reached 98%. The results demonstrate that C. vulgaris is a green and highly effective biosorbent for vanadium removal from aquatic systems. [ABSTRACT FROM AUTHOR]

The environmental issues caused by chrome-tanned leather could not be overlooked, and the high concentration of chromium (Cr) in the waste leather fragments was a major factor in limiting its resource utilization. Few studies have reported the contamination of soil and groundwater by discarded leather fragments. Soil column and static leaching experiments were conductive to exploring the release and transport of organic compounds and Cr from waste leather fragments with various types and sizes. The findings revealed that the 1 cm2-sized leather fragments of cowhide released more organic compounds into the leachate than the pigskin with same size, whereas leather fragments of the pigskin released more Cr than those of the cowhide, and this phenomenon was more prominent under rainfall condition at pH 4.68 than at pH 5.86. The Cr concentration increased at first and then decreased in the leachate, while the concentrations of soluble protein (SP), free amino acid (FAA), and total organic carbon (TOC) increased with the leaching event. After leaching, the concentrations of SP and FAA in each soil layer were nearly three times higher in the leather treatment groups than in the leather absent groups. Cr(III) was the primary species existed in the deep soil layer. The impact of leather fragment type and size on the release of Cr and organic compounds into soil was assessed, which helped to guide waste leather fragment reuse, landfill procedures, and impermeability measure design. [Display omitted] [ABSTRACT FROM AUTHOR]

To evaluate the impact of F in soil on seed germination, growth performance and biochemical parameters of Chinese cabbage (Brassica campestris L.) and oilseed rape (Brassica napus L.), a pot experiment was conducted by amending soil with 0, 200, 400, 600, 800 and 1000 mg F kg−1 spiked soil. During aging of exogenous F in soil, an increase in the soil pH and concentrations of all F fractions was noted at elevated F concentrations. Fluorine in the soil was mainly found in the residual fraction (88% and 86%). The results of pot experiment revealed that the percentages of seed germination rate, chlorophylls concentration, and the dry biomass of Chinese cabbage and oilseed rape decreased by 31, 23, 16%, and 24, 38, 31%, respectively, as compared with their respective controls. The free proline concentration increased by 40% for Chinese cabbage and by 151% for oilseed rape. It was observed that F mainly accumulated in the roots of both plants, and the bioaccumulation factor and translocation factor remained <1. This study showed more remarkable effects of F on oilseed rape than those on Chinese cabbage. [ABSTRACT FROM AUTHOR]

The widespread use of plastic film in agricultural production has resulted in the accumulation of large amounts of residual plastic film in the soil, and most of the plastic residuals eventually break up into microplastics (MPs). However, the effects of different film mulching methods on the soil ecosystems are largely unexplored. Therefore, we investigated the MPs distribution and the physicochemical properties and microbial community structure in the farmland soil tillage layer covered with different mulching method of film. The results indicate that the film mulching method had no significant effect on the soil pH and organic matter content, however, the respiration intensity of the soil covered with mulching film (MF) (60.11–84.99 μg/g) and shed film (SF) (56.10–65.68 μg/g) was significantly higher than that covered with shed film & mulching film (SMF) (17.25–39.16 μg/g). The MPs abundance in the soil covered with MF (1367 particles/kg soil) was significantly higher than that covered with SF (800 particles/kg soil) and slightly higher than that with SMF (1000 particles/kg soil). The small-sized (0–0.5 mm) MPs abundance was increased with the tillage layer depth (0–20 cm), while the large-sized (1–5 mm) MPs abundance was the opposite. In addition, in the soil covered with agricultural film, the dominant phylum and genera of the bacteria were Proteobacteria (relative abundance was 64.06 %) and Pseudomonas (13.16 %), respectively. In the soil without agricultural film application as a control treatment, the diversity of the soil bacterial community was higher than that in the soil covered with agricultural film, and the relative abundances of the top 10 genera were all less than 5 %. Overall, this study provides essential information for understanding the effects of different film mulching methods on the agricultural systems. Overall, this study provides essential information for understanding the effects of different film mulching methods on the distribution of MPs and the biogeochemical properties of farmland soils. [Display omitted] • The use of MF and SF significantly increased soil respiration intensity than SMF. • The use of MF significantly increased MPs abundance than SF and SMF. • The small-sized (≤0.5 mm) MPs were increased with the depth of the tillage layer. • MPs in the soil decreased the diversity of soil bacterial communities. • The main phylum and genus were Proteobacteria and Pseudomonas in soil covered with MF. [ABSTRACT FROM AUTHOR]

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). Environ Toxicol Chem 2016;35:695-701. © 2015 SETAC [ABSTRACT FROM AUTHOR]

Health risk of F in soil is of special concern due to the continuously elevated concentration of F in soil. However, there is still a dearth of risk assessments of F in soil based on in-vitro bioaccessibility posed by multiple exposure routes. Herein, the oral, inhalation, and dermal bioaccessibility of F in soil was firstly obtained by adapting and combining in-vitro methods, which then was introduced to remedy an information gap of a comprehensive risk of F in soil posed by a multi-exposure pathway. Combined in-vitro tests indicate the oral, inhalation, and dermal bioaccessibility of F was 13.15 ± 2.63%, 16.55 ± 2.63%, and 1.27 ± 0.73%, respectively. Plasma yielded a detoxic potential for the absorbed F after digesting in small intestine, while effects of enzymes, sweat, and food on the oral bioaccessibility of F were insignificant. Different with metals, the major dissolving phase of F was the interstitial fluid in the deep lung instead of in the alveolar macrophages intracellular environment. A potentially major release of F in the exocrine sweat was noted than in the apocrine sweat. Risk assessments based on the daily exposure incorporated with the in-vitro bioaccessibility suggested that compared with inhalation and dermal contact, oral ingestion was the main exposure route of F in soil to human. Present findings provide insights into the bioaccessibility and health risk of F in soil by multiple exposure routes, which are crucial for the risk control of F contamination in soil. [Display omitted] • A detoxic potential of plasma for the absorbed F after digesting in small intestine was noted. • Higher inhalation bioaccessible F in GS was observed than in ALF. • Risk of F in soil was mainly posed by oral ingestion. • Exposure of F posed by inhalation and dermal contact was in same magnitude. • Factors with no statistically obvious effect on OF bio were able to affect the health risk notably. [ABSTRACT FROM AUTHOR]

The pollution in soils and groundwater caused by the tannery have attracted public attention. However, few studies have been done on the migration and species distribution of Cr and coexisting ions produced by tanning in the vadose zone. In this paper, an in-production tannery and a suspended tannery were selected to compare the migration of Cr and other inorganic ions from tanneries in the vadose zone. Results showed that the sewage treatment station and the temporary waste storage site had the highest concentration of pollutants. Cr exhibited a cumulative effect in the middle soil layer (100–300 cm) in the suspended tannery. However, in the in-production tannery, the cumulative effect occurred only at the temporary waste storage site. The distribution of pollutants in the soils at different depths was fixed in the suspended tannery field. But in the in-production tannery field, it was closely related to daily production. Visual MINTEQ showed that the saturation index of a species of Cr was positive or negative simultaneously in the two sites, indicating that (1) the change of saturation index of Cr had no relationship with operation of tannery. (2) the influence of Cr precipitation or dissolution was related to the source strength, the coexisting ions, and pH. This study contributed to understanding the migration of characteristic pollutants caused by tanneries in the vadose zone under different external environments, and provided a reference for the quantification calculation of the source load of pollutants caused by industrial infiltration into the groundwater. [Display omitted] • Pollutants distribution was fixed in suspended tannery but changed in-production. • The equilibrium state of Cr(III) saturation and Cr(VI) unsaturated keep stable. • Cr(VI)% reduced in suspended tannery, but kept stabled in-production. [ABSTRACT FROM AUTHOR]

Nano-hydroxyapatite (NHAP), possessing high defluoridation capacity, has been widely used to remove fluoride (F) from polluted water, but little is known about how it affects the bioavailability and toxicity of soil F towards plants. Here, the impact of NHAP (2% w/w) amendment on immobilization, speciation and accumulation of F was studied in a soil-plant system. The results revealed that the NHAP amendment worked effectively to reduce levels of water-soluble F (37.3%−87.8%) and increase available P (76.6%–147%). X-ray photoelectron spectroscopy analysis indicated that the formation of insoluble CaF 2 and the ion exchange of F− with OH− into NHAP might be involved in the mechanism of F immobilization and soil pH elevation. Exposure to NHAP significantly decreased the abundance of Cyanobacteria in tested soils, and Gemmatimonadetes abundance in bulk soil was significantly higher than that in rhizosphere soil at 1,000 mg kg−1 F spiked level. Additionally, NHAP amendment decreased F accumulation in wheat shoots (9.10%–18.7%) and roots (3.88%–22.4%), which could mainly be attributed to the reduction of soil bioavailable F and the supplement of Ca from NHAP. These results suggest that NHAP could be a promising amendment to be applied to acidic soil contaminated with F. ga1 • Fluoride bioavailability and toxicity were prominently reduced by NHAP amendment. • NHAP amendment provided a continuous P nutrient to wheat. • NHAP promoted F immobilization through the formation of CaF 2 and Ca 10 (PO 4) 6 F 2. • NHAP amendment significantly decreased the abundance of Cyanobacteria in the soils. • NHAP amendment promoted plant growth and reduced F uptake in wheat root and shoot. [ABSTRACT FROM AUTHOR]

Hitherto, the effect of vanadium on higher plant growth remains an open topic. Therefore, nontargeted metabolomic and RNA-Seq profiling were implemented to unravel the possible alteration in alfalfa seedlings subjected to 0.1 mg L−1 (B group) and 0.5 mg L−1 (C group) pentavalent vanadium [(V(V)] versus control (A group) in this study. Results revealed that vanadium exposure significantly altered some pivotal transcripts and metabolites. The number of differentially expressed genes (DEGs) markedly up- and down-regulated was 21 and 23 in B_vs_A, 27 and 33 in C_vs_A, and 24 and 43 in C_vs_B, respectively. The number for significantly up- and down-regulated differential metabolites was 17 and 15 in B_vs_A, 43 and 20 in C_vs_A, and 24 and 16 in C_vs_B, respectively. Metabolomics and transcriptomics co-analysis characterized three significantly enriched metabolic pathways in C_vs_A comparing group, viz., α -linolenic acid metabolism, flavonoid biosynthesis, and phenylpropanoid biosynthesis, from which some differentially expressed genes and differential metabolites participated. The metabolite of traumatic acid in α -linolenic acid metabolism and apigenin in flavonoid biosynthesis were markedly upregulated, while phenylalanine in phenylpropanoid biosynthesis was remarkably downregulated. The genes of allene oxide cyclase (AOC) and acetyl-CoA acyltransferase (fadA) in α -linolenic acid metabolism, and chalcone synthase (CHS), flavonoid 3′-monooxygenase (CYP75B1), and flavonol synthase (FLS) in flavonoid biosynthesis, and caffeoyl-CoA O -methyltransferase (CCoAOMT) in phenylpropanoid biosynthesis were significantly downregulated. While shikimate O -hydroxycinnamoyltransferase (HCT) in flavanoid and phenylpropanoid biosynthesis were conspicuously upregulated. Briefly, vanadium exposure induces a readjustment yielding in metabolite and the correlative synthetic precursors (transcripts/unigenes) in some branched metabolic pathways. This study provides a practical and in-depth perspective from transcriptomics and metabolomics in investigating the effects conferred by vanadium on plant growth and development. [Display omitted] • There exist three significantly enriched KEGG pathways at 0.5 mg L−1 V. • Raffinose was markedly upregulated at all vanadium exposed compare groups. • Traumatic acid was obviously upregulated at α -linolenic acid metabolism. • Apigenin was distinctly upregulated in flavonoid biosynthesis. [ABSTRACT FROM AUTHOR]

The microbially- and chemically-mediated redox process is critical in controlling the fate of vanadium (V) in tailing environment. Although the microbial reduction of V has been widely studied, the coupled biotic reduction mediated by beneficiation reagents and the underlying mechanism remain unclear. Herein, the reduction and redistribution of V in V-containing tailings and Fe/Mn oxide aggregates mediated by Shewanella oneidensis MR-1 and oxalic acid were explored. The dissolution of Fe-(hydr)oxides by oxalic acid promoted the microbe-mediated V release from solid-phase. After 48-day of reaction, the dissolved V concentrations in the bio-oxalic acid treatment reached maximum values of 1.72 ± 0.36 mg L–1 and 0.42 ± 0.15 mg L–1 in the tailing system and the aggregate system, respectively, significantly higher than those in control (0.63 ± 0.14 mg L–1 and 0.08 ± 0.02 mg L–1). As the electron donor, oxalic acid enhanced the electron transfer process of S. oneidensis MR-1 for V(V) reduction. The mineralogical characterization of final products indicates that S. oneidensis MR-1 and oxalic acid promoted solid-state conversion from V 2 O 5 to NaV 6 O 15. Collectively, this study demonstrates that microbe-mediated V release and redistribution in solid-phase were promoted by oxalic acid, suggesting that the role of organic agents for the V biogeochemical cycle in natural systems deserves greater attention. [Display omitted] • Dissolved V increased in biotic incubations compared to abiotic controls. • Oxalic acid could stimulate microbial reduction process and V release. • V mobilization resulted from reductive dissolution of Fe-(hydr)oxides in tailings. • The reduced V(IV) was immobilized in the newly formed mineral NaV 6 O 15. [ABSTRACT FROM AUTHOR]

Combined pollution in tannery sludge landfill has become increasingly serious. Accurate identification of the contribution of coexisting substances to Cr migration in tannery sludge sites was essential for the selection of remediation methods for tannery contaminated sites. However, the effect of the coexisting substances on their contribution to Cr migration remained unclear. In this study, the analytical method of panel data and soil column experiments were combined for the first time to quantify the extent to which different contaminants contribute to Cr migration, and further identify the dominant microbial species. Results showed that NH 3 –N inhibited the migration of Cr(VI), while NO 3 ––N and fatliquor agent promoted the migration of Cr(VI). The panel data analysis showed that the order of the contribution rate of the factors affecting the Cr(VI) migration was Cr(VI) concentration, coexisting substances, and environment factors. In addition, Veronii was the dominant popular in fatliquors-contaminated soils. The relative abundance of Veronii increased from 6.31% to 30.48% in the fatliquors treatment group, while it decreased to 21.65% in the fatliquors and Cr treatment group. This study provided a quantitative method to the contribution rate of various factors to Cr migration under rainfall, taken into account the response of the microbial community in each experimental group, and provided theoretical support for the selection of remediation methods in soil and groundwater for tannery sites. [Display omitted] • Panel data combined with soil column study to quantify the effect on Cr transport. • Coexisting substances influenced greater than environmental factors on Cr migration. • Denitrification significantly affected the migration of Cr(VI) in soil. [ABSTRACT FROM AUTHOR]

The widespread usage of per- and poly-fluoroalkyl substances (PFAS) has caused great concern due to their potential toxicology to human and environmental health. However, there have been limited investigations on the vertical distribution of PFAS in fluorine (F) contaminated soils. In this study, the spatial and vertical distribution of metals, total F, and PFAS in the soil profiles were investigated at different areas in an industrial city. The higher F concentrations in the farmland soils with intensive agricultural activities suggested the impacts of soil tillage. The ΣPFAS concentrations ranged from 0.187 to 1.852 ng g−1 in all soil samples, with PFOA as the dominant pollutant, which accounted for 17.2%–51.6% of the ΣPFAS in all samples. Highest level of PFAS was found in the shallow layer of the soil profiles. The long-chain PFAS such as PFUdA and PFTeDA tended to remain in the topsoil, while the short-chains (PFBA, PFPeA, and PFHxA) have migrated to depth of 100 cm in the vertical soil profile. The application of F-enriched phosphorus fertilizers and atmospheric deposition may be important sources of F and PFAS in soils in this area. Correlation analysis indicated that most of PFAS have similar common sources, and the significantly positive correlation between Zn and PFAS suggested they may share similar sources. This study highlights the need for further work to monitor the PFAS level in soil environments in industrialized areas, in addition to focusing on soil metal and F pollution. [Display omitted] • Vertical distribution of metals, F, and PFAS in soil profiles were investigated. • Higher F level in farmland soils with intensive agriculture activities was observed. • PFOA were the dominant PFAS with high concentrations in the soils. • Long-chain PFAS mainly remained in topsoil, while short-chains moved to deeper layer. • Metals such as Zn and PFAS in soils may share similar sources. [ABSTRACT FROM AUTHOR]

Vanadium-titanium (V-Ti) magnetite tailings have caused great concern due to their safety hazards and environmental risks. However, the microbial community structure and the key geochemical factors of V-Ti magnetite tailing profiles under different management modes remain unclear. Therefore, we investigated the heavy metal distribution and the microbial community structure of the soils and tailings at varied depths of V-Ti magnetite tailing profiles with and without soil coverage. The results indicated that the topsoil covering measures retarded the acidification of tailings during stockpiling. However, As, Mn, and V in tailings have the ability to migrate to the overlying soil. Based on 16S rRNA gene amplicon sequencing, Proteobacteria was the dominant genus in the topsoil-covered tailings, whereas the most abundant genus in the exposed tailings was Betaproteobacteria. Furthermore, Rhodobacter , Hydrogenophaga , Novosphingobium , and Geobacter enriched in tailings may potentially contribute to V(V) biotransformation and the development of mine bioreremediation technologies. RDA and Spearman correlation analysis showed that pH, EC, Cd, Mn, Pb, and V were the main influencing factors regulating microbial community composition. Overall, this study provides insights for evaluating the soil covering management mode and the engineering applications of microbial technologies to manage V-Ti magnetite tailings. [Display omitted] • Soil covering retarded acidification of V-Ti magnetite tailings during stockpiling. • Upward transportation of As, Mn, and V from tailings may bring risk to covering soil. • Proteobacteria , Actinobacteria and Chloroflex dominated in the study tailings. • Microbial community succession occurred in the tailings stockpiling process. • pH, EC, Cd, Mn, Pb, and V were the key factors affecting microbial community. [ABSTRACT FROM AUTHOR]

The prosperity and development of tannery industry have brought about rapid economic growth. However, the tannery landfill without anti-seepage measures in the early stage has generated masses of environmental hazards owing to the lack of awareness in environmental protection. Therefore, it is imperative to pay much attention to the understanding of environmental hazards from tannery waste. In this study, solid samples and groundwater samples were collected from a tannery landfill to study the effect of the characteristic pollutants produced by tanning on chromium distribution with other coexisting substances. The results showed that significant correlations were demonstrated between multiple coexisting substances (total organic carbon, total petroleum hydrocarbons, total nitrogen, Cr, F, Ca, Cu and Pb), indicating the possible same source or they coming from the same tannery production stage. The weights of positive effects and negative effects of coexisting substances on total Cr distribution in the profile decreased in the order: total nitrogen > Cu > Ca > Pb > total organic carbon > F > SO 4 2– > Cd, and Ni > Cl > Hg, respectively. Moreover, the simulation of Visual MINTEQ showed that the cations were mainly bound to Cr as CrO 4 2−, while the anions were bound to Cr3+. This study provided a new perspective on the selection of remediation strategies for Cr-contaminated sites to avoid secondary environmental pollution caused by the release of coexisting heavy metals. [Display omitted] • Total Cr was significantly correlated with TN and TOC, while Cr(VI) was not. • Different coexisting substances made various impacts on total Cr concentration. • TN, TOC, Cu, Pb, and Ca had a significant positive effect on total Cr. • The cation was bound to Cr as CrO 4 2− and the anion was bound to Cr3+. [ABSTRACT FROM AUTHOR]

Chromium (Cr) and tannin are two major pollutants in leather industry. However, little is known about the co-migration of leather tannins and Cr in soils. In this study, column experiments were conducted to estimate Cr leaching behavior from topsoil and the environmental risk of the leachate at various tannin dosages and different ways (tannin either directly adding to the Cr-contaminated soil or adding stepwise through simulated rain) into the soil. The total Cr concentration in leachate was positively related with tannin content in soil, while Cr (Ⅵ) concentration was negatively correlated. The maximum cumulative leaching efficiency of total Cr from soil after six leaching events was 44.65% with 3 mg/g tannin adding into soil directly, and the maximum cumulative leaching efficiency of Cr (Ⅵ) was 38.75% with simulated rain leaching Cr-contaminated soil. With 3 mg/g tannin adding into soil, tannin concentration in the top layer (0–7 cm) lost by 32.67% after leaching, the amount of decomposed tannin was 0.25 mg/g, excluding the amount of tannin in leachate (3.63 mg/L) and the original amount in the soil (0.34 mg/g), indicating a slow degradation under natural condition. Both of the total Cr and Cr (Ⅵ) concentration in each layer of the soil columns decreased under tannin treatments compared with control. Compared with tannin adding stepwise into simulated rain, adding tannin into soil significantly (p < 0.05) affected the migration of Cr. Tannin increased the residual fraction while decreased the exchangeable fraction of Cr in the soils. Overall, this research can provide reference information for environmental risk assessment of contaminants in tanning sites. [Display omitted] • We examined the effect of tannin on release and fractionation of Cr in soils. • Tannin increased the total Cr while decreased the Cr (Ⅵ) concentration in leachate. • The degradation speed of tannin is slow under natural condition. • After leaching, the percentage of residual Cr-fraction in soils increased. • This result reflected that the tannin caused immobilization of Cr in soils. [ABSTRACT FROM AUTHOR]

Two new triterpene glycosides named ilexpublesnin A (1) and ilexpublesnin B (2) were isolated from the root of Ilex pubescens. Their structures were determined as 3-O-(β-d-xylopyranosyl)-28-O-(β-d-glucopyranosyl)-3β, 19α-dihydroxyurs-23-oxo-12-en-28-oic acid (1) and 28-O-(β-d-xylopyranosyl-(2→1)-β-d-glucopyranosyl)-3β, 19α-dihydroxyurs-23-oxo-12-en-28-oic acid (2) on the basis of chemical and spectroscopic methods. [Copyright &y& Elsevier]

Fluorine (F) is widely dispersed in the environment and frequently used in industry and agriculture with a high migration ability. Thus, it is essential to understand the leaching characteristic of F in soil from industry and agriculture sources. Several sources of F pollutants in soil, including fertilizers, pesticides, phosphogypsum, and atmospheric deposition, were selected to investigate leaching characteristics of F in soil by leaching experiments. The addition of phosphate fertilizer and compound fertilizer (N:P:K = 20:10:15) enhanced the leachability of F in soil and the proportion of F leached out from soil treated by these fertilizers were 0.25% and 0.24%, respectively. However, unanticipated lower leachability of F appeared in compound fertilizer (N:P:K = 17:17:17), nitrogen fertilizer, dipterex, fluoroglycofen, fluopimomide, simulative dry deposition (YF 3), and phosphogypsum loaded soils compared with additive-absent treatment. Although phosphogysum had a high F concentration, minimum proportion of F released (0.18%) was observed in phosphogypsum-coverd soil. The amounts of F leaching-out from surface soils (0–25 cm) treated with nitrogen fertilizer decreased 1.03 kg ha−1 comparing with blank control. Soil with phosphate fertilizer leached 5.47 kg F ha−1 a year, having the highest environment risk to deeper soil and groundwater. However, phosphogypsum and dry deposition of airbone F chemical had few effects on F leaching in soil. F-containing materials from agricultural process may leach more F from surface soils than industrial sources. [Display omitted] • Not every F-containing material in soil yields an increase of soil F leachability. • Soil applied with phosphate fertilizer had the highest F environment risk. • Minimum F leaching rate was observed in phosphogypsum-loaded soil. • Most of the F-containing atmospheric deposition accumulate in the surface of soil. • Fertilization contributes more in F leaching out from surface soil than pesticide. [ABSTRACT FROM AUTHOR]

The tannery industry is an integral part of economic development in many developing countries, and the environmental pollution caused by the tannery industry cannot be ignored. In this study, soil and groundwater samples at different depths were collected from an abandoned tannery to investigate the temporal and spatial distribution of characteristic pollutants produced by tanning. The concentrations of Cr, Cl, F and NH 4 +–N in the soil from the sludge temporary storage area were higher than those from the liming and unhairing workshop, chrome tanning workshop, wastewater outlet, and around wastewater pond. The concentration of Cr(VI) in all sampling sites was below the detection limit. The main species of Cr in the groundwater were Cr(NH 3) 6 Cl2+ and CrO 4 2− based on the simulation of Visual MINTEQ. The saturation index was negative and changed with time indicating that Cr existed in the dissolved phase. The proportion of Cr(VI) to total Cr was negatively correlated with the saturation index in village 1 and village 3. The simulation results from Visual MODFLOW and MT3DMS showed that the migration of Cr, NH 4 +–N, Cl− and F− mainly occurred in the Quaternary system. The coverage of the pollution plume of pollutants in villages 1 and 3 was as follows: Cr > NH 4 +−N > Cl− > F−. Two decay rate calculation methods of pollutants with migration time and distance were put forward to provide a basis for the actual investigation of the pollution migration scope and time determination. [Display omitted] • The migration of Cr, NH 4 +–N, F− and Cl− mainly occurred in the Quaternary system. • The saturation index of Cr increased firstly and then stabled or declined. • The species of Cr in groundwater were mainly Cr(NH 3) 6 Cl2+ and CrO 4 2−. • Two calculation methods of decay rate considering the actual situation were given. [ABSTRACT FROM AUTHOR]

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. ga1 • Vanadium speciation is influenced by soil conditions including redox potential, pH, organic matter, and microorganisms. • Low levels of V has beneficial effects on plants, but excessive V induces numerous adverse effects. • Plants have well-developed antioxidant defence systems to alleviate V toxicity. [ABSTRACT FROM AUTHOR]

Biochar additions to soil have been proposed as an environment-friendly way to enhance the soil nutrients or to amend the contaminated soils; however, few studies have evaluated the effectiveness of biochars from an integrated perspective of soil remediation and quality improvement, especially for the soil contaminated by vanadium with increasing prevalence, complex species and chemistry, widespread toxicity to organisms. Herein, this gap is addressed by using a biochar to evaluate the effectiveness of both remediation and quality improvement of a vanadium contaminated soil. Based on the physicochemical and morphology properties, the optimal biochar with a good porous structure and abundant surface functional groups prepared by pyrolyzing rice straw at 650 °C and sieving through a 200 mesh (RS-T 650 -P 0.075) was selected from 18 candidates. The increase of pH (1.72), organic matter content (3.80%), and available P content (9.17 mg kg−1) of soil and the decrease of bioavailable vanadium (225.59 ± 16.25 mg vanadium kg−1 soil) in soil during a 10-week experiment indicated an effective and stable improvement of soil quality and treatment for soil vanadium pollution, by high RS-T 650 -P 0.075 application (3%) to soil contaminated at high exogenous vanadium level (1000 mg vanadium kg−1 soil). Analysis of the cost-benefit and environmental influence confirmed the potential feasibility for practical applicating the RS-T 650 -P 0.075 to treat the vanadium contaminated soils. Overall, the RS-T 650 -P 0.075 can be served as a cost-effective and ecofriendly amendment for both soil quality improvement and the vanadium contaminated soil remediation. Image 1 • RS-T 650 -P 0.075 have a porous structure and high surface area. • RS-T 650 -P 0.075 have abundant functional groups and high aromaticity. • RS-T 650 -P 0.075 addition improved organic matter and available P level in soil. • Bioavailable V in soil decreased after adding RS-T 650 -P 0.075. • RS-T 650 -P 0.075 application is effective and ecofriendly for V polluted soil treatment. [ABSTRACT FROM AUTHOR]