钒镉复合污染对水稻吸收积累镉、钒和磷的影响

采用溶液培养法研究钒与镉复合污染对水稻生长及其吸收积累镉的影响,以便弄清在钒与镉复合污染条件下水稻的生长情况.试验结果表明,钒镉复合污染可影响水稻的生长发育.在培养液镉浓度(1 0mg·L-1)不变的情况下,随着溶液中钒浓度的增加,水稻根长、根系和茎叶的干重不断减少.当溶液中钒浓度达到1 6mg·L-1和3 2mg·L-1时,水稻茎叶和根系干重减少分别达到显著水平(p<0 05).钒镉复合污染也影响水稻植株对磷、钒和镉的吸收与积累.当培养液中镉浓度不变时,随着溶液中钒浓度的增加,水稻根系和茎叶中的磷浓度不断降低,而钒含量却不断提高,根系比茎叶积累更多的钒.此外,钒可抑制水稻植株对镉的吸收与积累.     

Release kinetics of vanadium from vanadium titano-magnetite: The effects of pH, dissolved oxygen, temperature andforeign ions

As part of a broader study of the environmental geochemistry behavior of vanadium(V), the release kinetics of V from the dissolution of natural vanadium titano-magnetite under environmentally relevant conditions was investigated. In both the acidic and basic domains, the V release rate was found to be proportional to fractional powers of hydrogen ion and dissolved oxygen activities. The dependence of the rate on dissolved oxygen can also be described in terms of the Langmuir adsorption model. The empirical rate equation is given by: r= k′α(H~+)~α(Kα(O_2))/(1+Kα(O_2)) where, α = 0.099–0.265, k′ = 3.2 × 10~(-6)–1.7 × 10~(-5), K =2.7 × 10~4–3.9 × 10~4 mol/L in acid solution(pH 4.1), and α =-0.494-(-0.527), k′ = 2.0 × 10~4–2.5 × 10~(-11), and K = 4.1 × 10~3–6.5 × 10~3 mol/L in basic solution(pH 8.8) at 20°C. Based on the effect of temperature on the release rate of V, the activation energies of minerals at p H 8.8 were determined to be 148–235 k J/mol, suggesting that the dissolution of vanadium titano-magnetite is a surface-controlled process. The presence of Na~+, Ca~(2+), Mg~(2+), K~+, NO_3~-, Cl~-, SO_4~(2-)and CO_3~(2-)was found to accelerate the V release rates. This study improves the understanding of both the V pollution risk in some mine areas and the fate of V in the environment.     

纳米铁锰氧化物对钒的吸附特性研究

为寻求处理土壤和地下水钒污染的吸附剂,采用模拟实验,开展了纳米铁锰氧化物(MnFe_2O_4)对五价钒(V~(5+))的吸附特征研究,分析了纳米铁锰氧化物浓度、pH值、时间、温度和初始钒浓度等因素对MnFe_2O_4吸附V~(5+)的影响,以揭示纳米铁锰氧化物的吸附动力学及热力学等特征,并通过扫描电镜(SEM)和红外光谱(IR)等表征方法分析了纳米铁锰氧化物吸附V~(5+)的机理.结果表明,在初始钒溶液为100 mg·L~(-1),MnFe_2O_4加入量为0.1 g,pH=4,温度为25℃的条件下,吸附过程在24 h达到平衡,且此条件下有最大吸附值和吸附率,分别为15.14 mg·g~(-1)和60.54%.纳米铁锰氧化物吸附钒的动力学过程符合伪二级动力学模型,等温吸附线符合Langmuir模型.热力学研究表明,升高温度有利于吸附,吸附过程为吸热过程.由扫描电镜结果可知,纳米铁锰氧化物有较大的比表面积,可提供较多的活性位点.因此,纳米铁锰氧化物可作为一种吸附材料用于钒污染废水处理.     

NH3-SCR performance and the resistance to SO2 for Nb doped vanadium based catalyst at low temperatures

Niobium oxide as the promoter was doped in the V/WTi catalyst for the selective catalytic reduction(SCR)of NO.The results showed that the addition of Nb_2O_5could improve the SCR activity at low temperatures and the 6 wt.%additive was an appropriate dosage.The enhanced reaction activity of adsorbed ammonia species and the improved dispersion of vanadium oxide might be the reasons for the elevation of SCR activity at low temperatures.The resistances to SO_2of 3V6Nb/WTi catalyst at different temperatures were investigated.FTIR spectrum and TG-FTIR result indicated that the deposition of ammonium sulfate species was the main deactivation reason at low temperatures,which still exhibited the reactivity with NO above 200°C on the catalyst surface.There was a synergistic effect among NH_3,H_2O and SO_2that NH_3and H_2O both accelerated the catalyst deactivation in the presence of SO_2at 175°C.The thermal treatment at 400°C could regenerate the deactivated catalyst and get SCR activity recovered.The particle and monolith catalysts both kept stable NO_xconversion at 225°C with high concentration of H_2O and SO_2during the long time tests.     

滇西北剑湖沉积物钒空间分布特征和生态风险

用电感耦合等离子体发射光谱仪（ICP-OES）测定剑湖表层及柱状沉积物钒（V）含量,采用改进BCR连续提取法提取V各形态,并对V空间分布特征和生态风险进行了分析,揭示了粒度对剑湖沉积物V及形态含量的影响.结果表明,剑湖表层沉积物和柱状沉积物颗粒均以粉砂粒和细砂为主,细颗粒V含量更高.表层沉积物V含量为（117.82±63.31）mg/kg,其水平空间分布差异较大.V可交换态、可还原态、可氧化态和残渣态含量分别为（8.91±8.91）,（18.36±10.53）,（7.67±7.67）,（80.22±58.71）mg/kg,主要以残渣态形式存在,且黏粒和粉砂粒对V可还原态和残渣态影响较大.V垂直分布差异大,底层V含量高于表层,少部分区域受黏粒和粉砂粒影响.剑湖沉积物V污染程度小,大部分地区潜在生态风险较低,底层沉积物污染程度和潜在生态风险都高于表层.     

土壤中钒的化学结合形态与转化条件的研究

为了利用和控制土壤条件,改善土壤供钒特征,为农业生产和环境保护服务,综合参考国内外对土壤中其他微量元素形态划分的方法,初步区分出土壤中的钒以５种主要的化学结合形态存在。其含量多少依次为残留态＞无定形氧化铁结合态＞有机质结合态＞易还原锰结合态＞可溶态。通常,残留态钒占土壤全钒含量的90％以上,而可溶态钒的含量常低于1μg/g。一般而言,在较高的温度,较强的还原条件以及酸性土壤条件下,土壤中其它化学结合态钒更多地向可溶态钒转化;除有机质结合态钒外,其它形态钒的含量都与土壤全铁含量间有着显著或极显著的正相关。外源钒在酸性红壤中的形态转化速率较慢,在石灰性的栗钙土中的形态转化速率较快。酸性土壤对钒的缓冲能力强,缓冲容量大,不容易产生钒污染。     

废SCR脱硝催化剂中钨和钒的浸出实验研究

废SCR脱硝催化剂中钨和钒的浸出是实现其回收的关键.采用碳酸钠混合焙烧-稀硫酸浸出法,对废SCR脱硝催化剂中金属钨和钒的浸出实验进行了研究,考察了焙烧温度t_1(℃)、焙烧时间t_2(h)、硫酸浓度c(v/v)、液固比w、浸出温度t_3(℃)、浸出时间t_4(h)、Na_2CO_3与催化剂的质量比m(Na_2CO_3)/m(催化剂)等因素对钨和钒浸出率的影响.结果表明,在t_1为800℃、t_2为3 h、c为2%、w为8:1、t_3为80℃、t_4为4 h、m(Na2CO3)/m(催化剂)为1.2的反应条件下,废SCR脱硝催化剂中钨和钒的浸出率可分别高达99.08%、98.49%,为后续钨和钒的高效提取与回收提供了有利的条件.     

Bioreduction of vanadium (V) in groundwater by autohydrogentrophic bacteria: Mechanisms and microorganisms

As one of the transition metals, vanadium(V)(V(V)) in trace amounts represents an essential element for normal cell growth, but becomes toxic when its concentration is above 1 mg/L. V(V) can alter cellular differentiation, gene expression, and other biochemical and metabolic phenomena. A feasible method to detoxify V(V) is to reduce it to V(IV), which precipitates and can be readily removed from the water. The bioreduction of V(V) in a contaminated groundwater was investigated using autohydrogentrophic bacteria and hydrogen gas as the electron donor. Compared with the previous organic donors,H2 shows the advantages as an ideal electron donor, including nontoxicity and less production of excess biomass. V(V) was 95.5% removed by biochemical reduction when autohydrogentrophic bacteria and hydrogen were both present, and the reduced V(IV)precipitated, leading to total-V removal. Reduction kinetics could be described by a first-order model and were sensitive to p H and temperature, with the optimum ranges of p H 7.5–8.0 and 35–40°C, respectively. Phylogenetic analysis by clone library showed that the dominant species in the experiments with V(V) bioreduction belonged to theβ-Proteobacteria. Previously known V(V)-reducing species were absent, suggesting that V(V)reduction was carried out by novel species. Their selective enrichment during V(V)bioreduction suggests that Rhodocyclus, a denitrifying bacterium, and Clostridium, a fermenter known to carry out metal reduction, were responsible for V(V) bioreduction.     

Bioreduction of vanadium (V) in groundwater by autohydrogentrophic bacteria: Mechanisms and microorganisms

As one of the transition metals, vanadium (V) (V(V)) in trace amounts represents an essential element for normal cell growth, but becomes toxic when its concentration is above 1 mg/L. V(V) can alter cellular differentiation, gene expression, and other biochemical and metabolic phenomena. A feasible method to detoxify V(V) is to reduce it to V(IV), which precipitates and can be readily removed from the water. The bioreduction of V(V) in a contaminated groundwater was investigated using autohydrogentrophic bacteria and hydrogen gas as the electron donor. Compared with the previous organic donors, H₂ shows the advantages as an ideal electron donor, including nontoxicity and less production of excess biomass. V(V) was 95.5% removed by biochemical reduction when autohydrogentrophic bacteria and hydrogen were both present, and the reduced V(IV) precipitated, leading to total-V removal. Reduction kinetics could be described by a first-order model and were sensitive to pH and temperature, with the optimum ranges of pH 7.5–8.0 and 35–40°C, respectively. Phylogenetic analysis by clone library showed that the dominant species in the experiments with V(V) bioreduction belonged to the β-Proteobacteria. Previously known V(V)-reducing species were absent, suggesting that V(V) reduction was carried out by novel species. Their selective enrichment during V(V) bioreduction suggests that Rhodocyclus, a denitrifying bacterium, and Clostridium, a fermenter known to carry out metal reduction, were responsible for V(V) bioreduction.     

Effect of MoO3 on vanadium based catalysts for the selective catalytic reduction of NOx with NH3 at low temperature

The selective catalytic reduction(SCR) activities of the MoO_3 doped V/WTi catalysts prepared by the incipient wetness impregnation method at low temperature were investigated.The results showed that the addition of MoO_3 could enhance the NO_ xconversion at low temperature and the best SCR activity was obtained when the dosage of MoO_3 reached5 wt.%. The NH3-TPD and DRIFTS experiments indicated that the addition of MoO_3 changed the type and number of acid sites on the surface of catalysts and reaction activities of acid sites were altered at the same time. The redox capacity and amount of active oxygen species got improved for V3Mo5/WTi catalyst, which could be confirmed by the H_2-TPR and transient response experiments. Water vapor inhibited the NO_xconversion at low temperature. Deposition of ammonium sulfate or bisulfate might be main reason for the loss of catalytic activity in the presence of SO_2 at low temperature. Choosing the suitable NH_3/NO ratio and elevation of reaction temperature both could weaken the influence of SO_2 on the SCR activity of the V3Mo5/WTi catalyst. Thermal treatment of the deactivated catalyst at350°C could get the low temperature activity recovered. The decrease of GHSV improved the de NO_x efficiency at low temperature and we speculated that the rational technological process and operation parameters could contribute to the application of this kind of catalysts in real industrial environment.     

基于唐南渗析原理阳离子交换膜对Cu~(2+)、Mn~(2+)、Zn~(2+)去除能力的研究

基于唐南渗析原理,采用阳离子交换膜去除原水中Cu2+、Mn2+、Zn2+等重金属离子,研究影响阳离子交换膜去除各重金属离子能力大小的机制以及2种重金属离子共存时互相干扰的机制.结果表明,阳离子交换膜可有效去除原水中Cu2+、Mn2+、Zn2+等重金属离子,去除率为75%～85%;在浓度相同下且重金属离子带相同电荷数时,其水化离子半径越小,离子扩散速度就越快,阳离子交换膜对其去除能力就越强;当重金属水化离子半径基本相同时,膜对原子序数小的重金属离子的去除能力更强;相同浓度且相同电荷数的重金属离子共存时,各离子同步被去除,但各离子之间存在干扰,越易于被离子交换的离子与其它离子共存时,其竞争能力越强,使其他离子的去除率降低越多;当待去除离子的总浓度远低于膜的交换容量时,离子共存时各离子的去除率相比离子单独存在时各离子的去除率下降幅度不大.     

An optimised sequential extraction scheme for the evaluation of vanadium mobility in soils

Reviewing the current state of knowledge about sequential extraction applied for soil vanadium(V) fractionation, we identified an urgent requirement of an sequential extraction(SE) specified for V. Namely, almost all previous SE extracted only 8.4%–48% of total V in soils(excluding residue). Thus, we proposed an eight-step SE for V fractionation in soils according to the knowledge gained from literature and our own dissolution experiments with model minerals. After extracting the mobilisable and adsorbed V with de-ionised water and 5 mmol/L phosphate, 1 mol/L pyrophosphate was applied to gather organic matter bound V which minimised the artefact dissolving Al and Fe(hydr)oxides occurred when using HNO_3–H_2O_2for extraction. Extraction with 0.4 mol/L NH_2OH·HCl was highly selective toward manganese oxides. Fractionation of different crystalline Al and Fe(hydr)oxides associated V with 1 mol/L HCl, 0.2 mol/L oxalate buffer and 4 mol/L HCl at 95°C especially improved the extractability of V incorporated with crystalline phase associated V. The suitability of our new SE scheme was confirmed by its higher selectivity against the target phases and higher extraction efficiencies(55%–77% of total V) with model minerals and 6 soils of different properties than previous SE.     

五氯苯酚与邻氯苯酚和2,4-二氯苯酚对斑马鱼的联合毒性

在五氯苯酚(PCP)与邻氯苯酚(2-CP)和2,4-二氯苯酚(2,4-DCP)3种物质单一毒性试验结果的基础上,按照等毒性单位设计,采用相加指数法,对五氯苯酚(PCP)与邻氯苯酚(2-CP)或2,4-二氯苯酚(2,4-DCP)以及这3种物质共存对斑马鱼(Brachydanio rerio)的联合毒性进行了试验研究.结果表明,邻氯苯酚(2-CP)和2,4-二氯苯酚(2,4-DCP)与五氯苯酚的联合毒性效应均表现为协同作用,使五氯苯酚的毒性剧增.由于邻氯苯酚或2,4-二氯苯酚的存在以及3种物质共存,使五氯苯酚对斑马鱼的48 h LC50由原来的0.102 mg/L,分别下降到0.031,0.029及0.022 mg/L.因此可见,水体污染评价目前只考虑单一毒物的影响还远远不够,由此制定的控制标准对水体的保护不利,必须从联合毒性的角度对水质污染进行综合评价.      

Promoting effect of vanadium on catalytic activity of Pt/Ce–Zr–O diesel oxidation catalysts

A series of Pt–V/Ce–Zr–O diesel oxidation catalysts was prepared using the impregnation method. The catalytic activity and sulfur resistance of Pt–V/Ce–Zr–O were investigated in the presence of simulated diesel exhaust. The effect of vanadium on the structure and redox properties of the catalysts was also investigated using the Brunauer–Emmett–Teller method,X-ray diffraction, H2temperature-programmed reduction, CO temperature-programmed desorption, X-ray photoelectron spectroscopy, and Energy Dispersive Spectroscopy. Results showed that the Pt particles were well dispersed on the Ce–Zr–O carrier through the vanadium isolation effect, which significantly improved the oxidation activity toward CO and hydrocarbons. An electron-withdrawing phenomenon occurred from V to Pt, resulting in an increase in the metallic nature of platinum, which was beneficial to hydrocarbon molecular activation.     

Levels, distributions, and sources of legacy and novel per- and perfluoroalkyl substances (PFAS) in the topsoil of Tianjin, China

Soil is a major sink for per- and perfluoroalkyl substances (PFAS), wherein PFAS may be transferred through the food chain to predators at upper trophic levels, which poses a threat to human health. Herein, the concentrations and distributions of legacy and novel PFAS in topsoil samples from different functional areas in Tianjin were comprehensively investigated. Seventeen PFAS congeners were identified, with concentrations ranging from 0.21 ng/g to 5.35 ng/g, with a mean concentration of 1.25 ng/g. The main PFAS in the topsoil was perfluorooctanoic acid (PFOA). 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA; <MDL–1.95 ng/g, mean 0.11 ng/g), as an emerging substitute for perfluorooctane sulfonate (PFOS), was also detected in the topsoil. It showed slightly higher concentrations than PFOS (<MDL–1.62 ng/g, mean 0.10 ng/g), indicating it has gradually replaced legacy PFOS in this area. Based on the positive-definite matrix factor (PMF) receptor model, the major PFAS sources was dominated by textile treatment, metal electroplating plants, and some potential precursors of PFAS with longer chains (>C8) were the major sources (43.4%), followed by food packaging as well as coating materials (25.5%). In addition, Spearman correlation analysis and the structural equation model showed that population density significantly impacted the PFAS distribution in the topsoil of Tianjin.     

Seasonal variability of ambient NH3, NO, NO2 and SO2 over Delhi

We present the diurnal and seasonal variability of ambient NH3, NO, NO2 and SO2 over Delhi, India. Ambient NH3, NO and NO2 were measured continuously during winter, summer and autumn seasons using NH3- and NOx-analyzer, which operates by chemiluminescence method with a higher estimation e ciency (> 90%) than the chemical trap method (reproducibility 4.7%). Prominent diurnal, day-to-day and seasonal variations of ambient mixing ratio of NH3, NO, NO2 and SO2 were observed during the study period. Seasonal variation with higher mixing ratio in winter was observed for all measured trace gases except NO. Day-night variation of all measured trace gases observed was higher in winter in comparison with summer. Late morning increase in NO2 mixing ratio might be attributed to conversion of NO to NO2 with the interaction of O3.     

低温条件下1,2,4-三氯苯降解菌的筛选及降解特性

在10 ℃的低温条件下, 从吉林石化化工厂排污管和长春第一汽车制造厂污水处理厂的混合污泥中驯化并分离出10株能以1,2,4-三氯苯（1,2,4-TCB）为唯一碳源的降解菌株, 通过筛选得到6株高效1,2,4-TCB降解菌株. 以6株菌的混合菌为研究对象, 考察其对1,2,4-TCB的降解特性. 结果表明, 混合菌在以葡萄糖为辅助碳源, 硫脲为氮源, pH为7.0, 盐度为2.0%, 溶液体积100 mL的条件下对1,2,4-TCB的降解效果最佳, 且添加辅助碳源对1,2,4-TCB的降解有一定的促进作用. 根据菌种的生理生化特征对降解菌进行初步鉴定, 结果表明,6株菌分别属于弧菌属（Vibrio sp.）, 奈瑟氏球菌属（Neisseria sp.）, 螺菌属（Spirillum sp.）, 无色细菌属（Achromobacter sp.）, 醋酸单胞菌属（Acetobacter sp.）和节细菌属（Archrobacter sp.）.