Molecular diversity of arbuscular mycorrhizal fungi at a large-scale antimony mining area in southern China

Arbuscular mycorrhizal fungi (AMF) have great potential for assisting heavy metal hyperaccumulators in the remediation of contaminated soils. However, little information is available about the community composition of AMF under natural conditions in soils contaminated by antimony (Sb). The objective of this study was to investigate the characteristics of AMF molecular diversity, and to explore the effects of Sb content and soil properties on the AMF community structure in an Sb mining area. Four Sb mine spoils and one adjacent reference area were selected from around the Xikuangshan mine in southern China. The association of AMF molecular diversity and community composition with the rhizosphere soils of the dominant plant species was studied by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE). Results from all five studied sites showed that the diversity of AMF decreased with increasing Sb concentration. Principal component analysis (PCA) indicated that the AMF community structure was markedly different among these groups. Further redundancy analysis (RDA) showed that Sb contamination was the dominating factor influencing the AMF community structure in the Sb mine area. However, the multivariate analysis showed that, apart from the soil Sb content, extractable nitrogen content and organic matter content also attributed to AMF sequence distribution type. Some AMF sequences were only found in the highly contaminated area and these might be ideal candidates for improving phytoremediation efficiency in Sb mining regions. Gene sequencing analysis revealed that most species were affiliated with Glomus, suggesting that Glomus was the dominant AMF genus in the studied Sb mining area.     

土壤环境中锑的生物毒性评价方法比较

锑的生物毒性测试可以间接反映锑及其化合物对生物与生态系统的影响。在简要介绍锑在土壤环境中赋存特征的基础上,综述了不同类型生物对土壤及其浸提液中锑的毒性响应,比较了不同的生物毒性测试方法在土壤环境中锑污染识别的可行性及适应性,并提出了考虑土壤性质及老化时间对锑生物毒性评价的影响,以及使用不同营养等级指示生物(微生物、动物和植物)评价等建议。     

环境敏感地区纺织染整工业锑污染物排放限值探究

在对纺织染整企业集聚、环境位置敏感的两个典型区域调研的基础上,通过类似重金属标准和毒性类比、排污治理情况及水体底泥中锑含量的分析、水环境承载力和允许排放浓度计算等技术论证,提出环境敏感地区纺织染整工业锑的排放限值按不同排放情形可分别设定为0.1 mg/L和0.05 mg/L。工程实例表明,采用基于聚合硫酸铁混凝沉淀法的高低浓度废水分质处理技术可满足排放限值要求,且经济成本可接受。     

Characterization and physicochemical aspects of novel cellulose-based layered double hydroxide nanocomposite for removal of antimony and fluoride from aqueous solution

A series of novel adsorbents composed of cellulose (CL) with Ca/Al layered double hydroxide (CC_xA; where x represent the Ca/Al molar ratio) were prepared for the adsorption of antimony (Sb(V)) and fluoride (F^?) ions from aqueous solutions. The CC_xA was characterized by Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), elemental analysis (CHNS/O), thermogravimetric analysis (TGA-DTA), zeta potential, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) analysis. The effects of varying parameters such as dose, pH, contact time, temperature and initial concentration on the adsorption process were investigated. According to the obtained results, the adsorption processes were described by a pseudo-second-order kinetic model. Langmuir adsorption isotherm model provided the best fit for the experimental data and was used to describe isotherm constants. The maximum adsorption capacity was found to be 77.2 and 63.1 mg/g for Sb(V) and F^?, respectively by CC₃A (experimental conditions: pH 5.5, time 60 min, dose 15 mg/10 mL, temperature 298 K). The CC₃A nanocomposite was able to reduce the Sb(V) and F^? ions concentration in synthetic solution to lower than 6 μg/L and 1.5 mg/L, respectively, which are maximum contaminant levels of these elements in drinking water according to WHO guidelines.     

Multiple effects of nitrate amendment on the transport, transformation and bioavailability of antimony in a paddy soil-rice plant system

Nitrate (NO₃^?) is known to be actively involved in the processes of mineralization and heavy metal transformation; however, it is unclear whether and how it affects the bioavailability of antimony (Sb) in paddy soils and subsequent Sb accumulation in rice. Here, the effects of NO₃^? on Sb transformation in soil-rice system were investigated with pot experiments over the entire growth period. Results demonstrated that NO₃^? reduced Sb accumulation in brown rice by 15.6% compared to that in the control. After amendment with NO₃^?, the Sb content in rice plants increased initially and then gradually decreased (in roots by 46.1%). During the first 15 days, the soil pH increased, the oxidation of Sb(III) and sulfides was promoted, but the reduction of iron oxide minerals was inhibited, resulting in the release of adsorbed and organic-bound Sb from soil. The microbial arsenite-oxidizing marker gene aoxB played an important role in Sb(III) oxidation. From days 15 to 45, after NO₃^? was partially consumed, the soil pH decreased, and the reductive dissolution of Fe(III)-bearing minerals was enhanced; consequently, iron oxide-bound Sb was transformed into adsorbed and dissolved Sb species. After day 45, NO₃^? was completely reduced, Sb(V) was evidently reduced to Sb(III), and green rust was generated gradually. Thus, the available Sb decreased due to its enhanced affinity for iron oxides. Moreover, NO₃^? inhibited the reductive dissolution of iron minerals, which ultimately caused low Sb availability. Therefore, NO₃^? can chemically and biologically reduce the Sb availability in paddy soils and alleviate Sb accumulation in rice. This study provides a potential strategy for decreasing Sb accumulation in rice in the Sb-contaminated sites.     

贵州某锑冶炼厂周边农田土壤锑、砷污染与人体健康风险评估

本研究以贵州省独山县某锑冶炼厂周边农田土壤为研究对象,系统采集17个土壤样品,测定了土壤中Sb、As总含量,并采用生理提取试验(PBET)和简化生物可给性提取试验(SBET)两种体外胃肠模拟实验方法分析了土壤中Sb、As的生物可给态含量,基于土壤Sb、As总量和生物可给性(PBET和SBET)评估了研究区锑、砷污染土壤暴露引起的潜在人体健康风险。结果表明:研究区农田土壤锑、砷污染严重,土壤中Sb(55.63±75.59 mg/kg)和As(44.31±38.34 mg/kg)的平均含量均超过贵州省区域背景值和我国农用地土壤污染风险筛选值;土壤中SBET和PBET提取的生物可给态Sb和As含量和计算得到的生物可给性都较低,大多数样品的生物可给性低于40%。相对于元素总量,基于Sb和As生物可给性(PBET和SBET)的人体非致癌风险(HQ和HI)和致癌风险(CR)均显著降低,其中成人和儿童的非致癌风险值均降至安全值范围,但是As的致癌风险除了CR_SBET-成人降至安全水平,CR_PBET-成人、CR_SBET-儿童以及CR_PBET-儿童值仍处于1.0E-06~1.0E-04之间,表明As对当地成人和儿童的潜在致癌风险仍不容忽视,特别是儿童。     

Antimony transformation and mobilization from stibnite by an antimonite oxidizing bacterium Bosea sp. AS-1

Soils and waters are heavily contaminated by antimony in Xikuangshan（XKS） mine area.It is widely accepted that oxidative dissolution of sulfide minerals and aqueous dissolution are the most prevalent geochemical mechanisms for the release of Sb to the environment.Bosea sp. AS-1 is an antimonite-oxidizer isolated from the mine slag in Xikuangshan Sb mine. Whole genome sequencing revealed the presence of multiple sulfur-oxidizing genes,antimony（Sb） metabolism genes and carbon fixation genes in AS-...     

Co-leaching of brominated compounds and antimony from bottled water

A fast-growing bottled water market is occasionally challenged by reports calling for contaminant leaching from water-contact materials (plastics). Our focus was on leaching of antimony (Sb) and brominated compounds expressed by total soluble bromine (Br) measurements, including those of polybrominated diphenyl ethers (PBDE). Studies are lacking on concomitant leaching of two or more inorganic plastic constituents from the same bottle. A market-representative basket survey of bottled water was initiated in Boston, USA supermarkets. Bottled water classes sampled were: i) non-carbonated (NCR), ii) carbonated (CR), and iii) non-carbonated and enriched (NCRE). Plastic bottle materials sampled were: polyethylene terephthalate (PET), high-density polyethylene (HDPE), polystyrene (PS), and polycarbonate (PC). Storage conditions for the 31 bottled water samples were: 23 °C temperature, no-shaking and 12 h/12 h light/dark for 60 days of equilibration. Average Br and Sb concentrations after 60-days of storage followed the order of NCR < CR = NCRE, and NCR < CR < NCRE, respectively, suggesting that the presence of dissolved carbon dioxide in CR samples coupled to additions of flavors and color to NCRE could explain the elevated leaching of Br and Sb. Combining all bottled water classes and plastic material types, a highly significant (p < 0.001) correlation was observed between log-transformed soluble Br and Sb concentrations, suggesting similar leaching behavior. Among samples with the highest soluble Br concentrations, BDE-209 congener was qualitatively confirmed in three out of four bottled water samples. The PC, HDPE, and PS samples exhibited significantly (p < 0.05) lower Sb and Br leaching than PET. Upon quantitative validation of PBDE leaching from certain plastic bottles into water, a revisit to existing PBDE exposure assessment reports will be deemed necessary.     

Antimony leaching in plastics from waste electrical and electronic equipment (WEEE) with various acids and gamma irradiation

There has been a recent interest in antimony since the availability in readily mined areas is decreasing compared to the amounts used. It is important in many applications such as flame retardants and in the production of polyester, which can trigger an investigation of the leachability of antimony from plastics using different acids. In this paper, different types of acids are tested for their ability to leach antimony from a discarded computer housing, made of poly(acrylonitrile butadiene styrene), which is a common plastic type used in electrical and electronic equipment. The acid solutions included sodium hydrogen tartrate (0.5 M) dissolved in either dimethyl sulfoxide or water (at ca. 23 °C and heated to ca. 105 °C). The metal content after leaching was determined by inductively coupled plasma optical emission spectroscopy. The most efficient leaching medium was the heated solution of sodium hydrogen tartrate in dimethyl sulfoxide, which leached almost half of the antimony from the poly(acrylonitrile butadiene styrene). Gamma irradiation, which is proposed to improve the mechanical properties in plastics, was used here to investigate the influence of antimony leaching ability. No significant change in the amount of leached antimony could be observed.