Influence of the structure and composition of Fe–Mn binary oxides on rGO on As(III) removal from aquifers

Fe–Mn binary oxide (FMBO) possesses high efficiency for As(III) abatement based on the good adsorption affinity of iron oxide and the oxidizing capacity of Mn(IV), and the composition and structure of FMBO play important roles in this process. To compare the removal performance and determine the optimum formula for FMBO, magnetic graphene oxide (MRGO)–FMBO and MRGO–MnO₂ were synthesized with MRGO as a carrier to improve the dispersity of the adsorbents in aquifers and achieve magnetic recycling. Results indicated that MRGO–FMBO had higher As(III) removal than that of MRGO–MnO₂, although the ratios of Fe and Mn were similar, because the binary oxide of Fe and Mn facilitated electron transfer from Mn(IV) to As(III), while the separation of Mn and Fe on MRGO–MnO₂ restricted the process. The optimal stoichiometry x for MRGO–FMBO (Mn_xFe_3-xO₄) was 0.46, and an extraordinary adsorption capacity of 24.38 mg/g for As(III) was achieved. MRGO–FMBO showed stable dispersive properties in aquifers, and exhibited excellent practicability and reusability, with a saturation magnetization of 7.6 emu/g and high conservation of magnetic properties after 5 cycles of regeneration and reuse. In addition, the presence of coexisting ions would not restrict the practical application of MRGO–FMBO in groundwater remediation. The redox reactions of As(III) and Mn(IV) on MRGO–FMBO were also described. The deprotonated aqueous As(III) on the surface of MRGO–FMBO transferred electrons to Mn(IV), and the formed As(V) oxyanions were bound to ferric oxide as inner-sphere complexes by coordinating their “–OH” groups with Mn(IV) oxides at the surface of MRGO–FMBO. This work could provide new insights into high-performance removal of As(III) in aquifers.     

象山港流域入湾河流水体中重金属风险评价及其来源解析

本文根据丰水期象山港8种溶解态重金属的浓度调查,通过单因子污染指数(P_i)、内梅罗综合污染指数(P_n)和重金属污染指数(HPI)评价方法研究了重金属流域内入湾河流中重金属的污染.基于流域内土地利用类型与重金属浓度的相关性,结合实地走访调查,对重金属的来源进行了解析.结果表明,区域内重金属平均浓度大小表现为:FeMnZnCuAsCrPbCd;除Mn和Fe外,其余6种重金属浓度均符合《地表水环境质量标准》中的Ⅰ类水标准;区域内重金属风险较低,无污染现象,但存在沾污情况;以水产养殖为代表的农业面源污染是区域内重金属出现沾污的主要因素.为了合理规避区域内城镇化发展进程中的重金属风险,重点在于加强以农业面源为主的污染源监管.     

Effect of Gamma Radiation on the Properties of Crosslinked Chitosan Nano-composite Film

Chitosan nano-composite film crosslinked by citric acid and with glycerol as plasticizer and MgO as antibacterial agent was prepared by casting method. MgO nanoparticles were synthesized via calcination method in furnace at 500 °C for 4 h and characterized by X-ray diffraction and transmission electron microscope. The chitosan nano-composite film with composition chitosan/citric/glycerol/magnesium oxide (1 wt%:1 wt%:75 vol%:10 wt%) has high mechanical properties than other films. The effects of different irradiation doses on the mechanical, thermal and antibacterial activity were investigated. The tensile strength enhanced by increasing irradiation dose up to 10 kGy and the elongation negligible changed as irradiation dose increased. The thermal stability slightly increased up to dose 2.5 kGy then decreased with dose increment. The antimicrobial activity film was studied against white mulberry-borne bacterial pathogens either Gram positive or Gram negative bacteria and has positive impact of gamma irradiation on the antimicrobial activity. The use of the selected chitosan nano-composite film which irradiated by dose of 2.5 kGy and has magnesium oxide of average particle size 54.3 nm as new packaging materials found to improve storage quality and shelf-life of mulberry fruit.     

Effects of iodoacetic acid drinking water disinfection byproduct on the gut microbiota and its metabolism in rats

Iodoacetic acid (IAA) is an unregulated disinfection byproduct in drinking water and has been shown to exert cytotoxicity, genotoxicity, tumorigenicity, and reproductive and developmental toxicity. However, the effects of IAA on gut microbiota and its metabolism are still unknown, especially the association between gut microbiota and the metabolism and toxicity of IAA. In this study, female and male Sprague–Dawley rats were exposed to IAA at 0 and 16 mg/kg bw/day daily for 8 weeks by oral gavage. Results of 16S rRNA gene sequencing showed that IAA could alter the diversity, relative abundance and function of gut microbiota in female and male rats. IAA also increased the abundance of genes related to steroid hormone biosynthesis in the gut microbiota of male rats. Moreover, metabolomics profiling revealed that IAA could significantly disturb 6 and 13 metabolites in the feces of female and male rats, respectively. In female rats, the level of androstanediol increased in the IAA treatment group. These results were consistent with our previous findings, where IAA was identified as an androgen disruptor. Additionally, the perturbed gut microbiota and altered metabolites were correlated with each other. The results of this study indicated that IAA could disturb gut microbiota and its metabolism. These changes in gut microbiota and its metabolism were associated with the reproductive and developmental toxicity of IAA.     

Application of soft computing to predict water quality in wetland

Prediction of water quality is a critical issue because of its significant impact on human and ecosystem health. This research aims to predict water quality index (WQI) for the free surface wetland using three soft computing techniques namely, adaptive neuro-fuzzy system (ANFIS), artificial neural networks (ANNs), and group method of data handling (GMDH). Seventeen wetland points for a period of 14 months were considered for monitoring water quality parameters including conductivity, suspended solid (SS), biochemical oxygen demand (BOD), ammoniacal nitrogen (AN), chemical oxygen demand (COD), dissolved oxygen (DO), temperature, pH, phosphate nitrite, and nitrate. The sensitivity analysis performed by ANFIS indicates that the significant parameters to predict WQI are pH, COD, AN, and SS. The results indicated that ANFIS with Nash-Sutcliffe Efficiency (NSE = 0.9634) and mean absolute error (MAE = 0.0219) has better performance to predict the WQI comparing with ANNs (NSE = 0.9617 and MAE = 0.0222) and GMDH (NSE = 0.9594 and MAE = 0.0245) models. However, ANNs provided a comparable prediction and the GMDH can be considered as a technique with an acceptable prediction for practical purposes. The findings of this study could be used as an effective reference for policy makers in the field of water resource management. Decreasing variables, reduction of running time, and high speed of these approaches are the most important reasons to employ them in any aquatic environment worldwide.

     

Environment-forming role of black saxaul, <Emphasis Type="Italic">Haloxylon aphyllum</Emphasis> (Minkw.) Iljin in the Karnabchul Desert

The environment-forming role of desert tree plants has been studied in the light of A.A. Uranov’s concept of phytogenic field using the example of black saxaul, Haloxylon aphyllum (Minkw.) Iljin, in the Karnabchul Desert. It has been shown that the environment-forming influence of this species leads to considerable changes in the light regime, air and soil moisture and temperature regimes, and soil humus and salt contents within its phytogenic field. Consequently, pertinent changes take place in the dynamics of abundance and distribution pattern of the main plant species and wormwood–ephemeral vegetation.     

抗生素对耐药型反硝化菌反硝化过程及微生物群落结构的影响

城市污水中部分抗生素通过常规工艺处理的去除率较低,导致自然水环境中微生物耐药性增强.为降低抗生素对城镇受纳水体的生态危害,提出了利用耐药型反硝化菌的共代谢作用降解微量抗生素的风险控制技术.采用乙酸钠为电子供体,并保持氧氟沙星(OFLX)浓度为1μg·L~(-1),逐步提高抗生素降解菌的优势生长,分别培养获得仅有乙酸钠和氮元素存在条件下的反硝化菌群(DnB_1)、微量抗生素与乙酸钠、氮元素同时存在条件的反硝化菌群(DnB_2).考察了抗生素通过反硝化共代谢的降解效果,抗生素对耐药型反硝化菌脱氮过程的影响,以及微生物群落结构的变化情况.结果表明DnB_2相比于DnB_1,对OFLX具有明显降解作用, DnB_1和DnB_2对OFLX的降解量分别为0.31μg·g~(-1)和16.14μg·g~(-1).OFLX浓度的提高,会在短期内抑制DnB_1反硝化活性.DnB_2反硝化过程受OFLX影响较小.同时,使用Illumina MiSeq平台进行高通量测序,基于测序结果聚类形成的OTUs信息,对比分析各样品的多样性,结果表明,DnB_1的微生物群落相对丰度和微生物群落多样性均要高于DnB_2.     

A2O工艺活性污泥中可培养丝状细菌的多样性

活性污泥法是应用最广泛的污水处理方法之一,但是由于丝状菌过度繁殖而引发的污泥膨胀是制约其发展的重大难题.本研究从A2O工艺城市污水处理系统的膨胀期活性污泥中分离培养出17株丝状细菌.对各菌株进行了16S rDNA测序和系统发育树分析,结果表明,这些分离的可培养丝状细菌均属于链霉菌属;利用rep-PCR指纹图谱技术进一步分析了所得菌种属内多样性,显示出活性污泥中链霉菌存在丰富的多样性.由于这些可培养丝状细菌与引起污泥膨胀的优势丝状菌(微丝菌)生理特征差别较大,不会在污水处理系统中过度繁殖,本研究向活性污泥中投加一定量的链霉菌分离菌株,发现部分菌株对污泥的沉降性能有明显改善作用,为污泥膨胀的防控提供了新的思路.     

Simulation of flow field and steel/slag interface in the mold region of a thin slab steel continuous caster with tetra-furcated nozzle

A three dimensional steady flow field model in the mold region of a thin slab steel continuous caster is presented using real geometrical dimension starting from the inlet port of the nozzle. The results indicate a special flow pattern in the caster while using a tetra-furcated nozzle. The fluid pattern in the mold region is shown to have two large downward and upward recirculation zones with a classic double-roll and two small vortices generated by the upward flow from the upper ports of the submerged entry nozzle. The flow pattern agrees well with the real observation obtained by full scale water model. This study investigates the interface wave behavior and its mechanism that leads to the breakup of the steel/slag interface, and thus the induction of impurities inside the final steel product. It is shown that a maximum wave height occurred because of the fluid contact from the upper ports. A critical casting speed was defined as the casting speed lead to wave instability, mostly associated with emulsification phenomena.     

塔里木河中游水盐梯度下的物种多样性研究

根据塔里木河中游5个断面30眼地下水监测井和30个植物样地2006—2008年调查监测的数据,分析了输水堤防修建后地下水埋深、地下水质以及物种多样性的变化及其相互关系。结果表明:地下水埋深的空间变化表现为沿河道方向先增加后减小的趋势,在时间上则表现为,从2006年到2008年埋深呈逐渐增加的特点;地下水化学类型的变化,在空间上表现出沿着河道方向有由Cl-—SO42-—Na+—Mg2+向Cl-—Na+类型转变的趋势,在时间上,地下水矿化度逐渐增加。物种多样性总体上呈现增加变化,地下水位和水质对塔里木河中游物种多样性变化有着密切的关系,地下水埋深2.8~3.7 m,矿化度1.8~2.4 g·L-1水平下的多样性较高,随着地下水埋深的增大和矿化度的升高,物种多样性水平降低。