Resolving the influence of nitrogen abundances on sediment organic matter in macrophyte-dominated lakes, using fluorescence spectroscopy

A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis. Macrophyte biomass showed coincident growth trends with time, but different variation rates with nitrogen treatment. All plant growth indexes with nitrogen addition (N, NH₄Cl 100, 200, 400 mg/kg, respectively) were lower than those of the control group. Four humiclike components, two autochthonous tryptophan-like components, and one autochthonous tyrosine-like component were identified using the parallel factor analysis model. The results suggested that the relative component changes of fluorescence in the colonized sediments were in direct relation to the change of root biomass with time. In the experiment, the root formation parameters of the plants studied were significantly affected by adding N in sediments, whichmay be related to the reason that the root growthwas affected byNaddition. Adding a low concentration of N to sediments can play a part in supplying nutrients to the plants. However, the intensive uptake of NH₄⁺ may result in an increase in the intracellular concentration of ammonia, which is highly toxic to the plant cells. Hence, our experiment results manifested that organic matter cycling in the macrophyte-dominated sediment was influenced by nitrogen enrichment through influencing vegetation and relevant microbial activity.     

Impacts of produced water origin on bacterial community structures of activated sludge

The purpose of this study was to reveal how activated sludge communities respond to influent quality and indigenous communities by treating two produced waters from different origins in a batch reactor in succession. The community shift and compositions were investigated using Polymerase Chain Reaction–denaturing gradient gel electrophoresis(PCR–DGGE) and further16 S ribosomal DNA(r DNA) clone library analysis. The abundance of targeted genes for polycyclic aromatic hydrocarbon(PAH) degradation, nah Ac/phn Ac and C12O/C23 O, was tracked to define the metabolic ability of the in situ microbial community by Most Probable Number(MPN) PCR. The biosystem performed almost the same for treatment of both produced waters in terms of removals of chemical oxygen demand(COD) and PAHs. Sludge communities were closely associated with the respective influent bacterial communities(similarity 60%), while one sludge clone library was dominated by the Betaproteobacteria(38%) and Bacteriodetes(30%)and the other was dominated by Gammaproteobacteria(52%). This suggested that different influent and water quality have an effect on sludge community compositions. In addition, the existence of catabolic genes in sludge was consistent with the potential for degradation of PAHs in the treatment of both produced waters.     

厌氧条件下 2,2',4,4'-四溴联苯醚的微生物降解

多溴联苯醚是环境中的新兴污染物,其中2,2’,4,4’-四溴联苯醚(BDE-47)在环境(尤其是水环境)中普遍存在且生物毒性很高.以BDE-47为对象,研究了6组含脱卤球菌的培养液对BDE-47的降解,目的是了解厌氧条件下BDE-47的微生物降解及其动力学.采用100 mL血清瓶作为厌氧反应器,对厌氧微生物进行培养.对每组菌作两种处理,一是仅加入BDE-47作为能源(设计终浓度为200μg.L-1),另一是同时加入BDE-47和三氯乙烯(TCE)作为能源(设计终浓度分别为200μg.L-1和13mg.L-1).经过3个月的实验,两组含脱卤球菌的培养液(6M6B和T2)均能明显降解BDE-47,生成BDE-17、BDE-4及少量的DE,TCE的存在一定程度上减弱了6M6B和T2菌对BDE-47的降解.采用PCR-DGGE法对不同培养菌液的群落结构进行比较,发现醋酸杆菌属与BDE-47的降解关联较大.在3种不同初始浓度(50、250和500μg.L-1)条件下,BDE-47的降解速率分别为0.003 3、0.001 4和0.001 0 d-1.本研究表明,厌氧条件下BDE-47在细菌的作用下可发生还原降解,生成BDE-17和BDE-4.醋酸杆菌属可能在BDE-47的降解中起较大作用.高浓度的BDE-47在一定程度上会抑制降解菌的活性.     

兰州市城区河道表层沉积物重金属污染及磁学参数相关关系研究

以兰州市城区8条河流的表层沉积物为研究载体,通过Hakanson潜在生态风险指数法、地质累积指数法及富集因子评价法等3种污染评价指标以及环境磁学方法对As、Co、Cr、Cu、Ni、Pb、V、Zn共8种重金属元素污染特征进行分析.结果显示,①元素As、Co、Ni、V在8条河流中均表现为轻微生态危害;元素Cr、Pb、Zn在...     

喀斯特高镉地质背景区水稻镉的富集、转运特征与机理

西南喀斯特地区土壤镉(Cd)具有"高地质背景、低污染风险"特征,但超过《土壤环境质量农用地土壤污染风险管控标准》风险管制值的区域是否仍具有低风险性,是迫切需要回答的问题.本文在罗甸县喀斯特峰丛谷地选择一个高Cd 土壤水稻种植区,开展土壤-水稻系统Cd含量特征和土壤Cd赋存形态等方面的研究,评价水稻各部位Cd的富集、转运...     

藏东多曲河流域锶富集水化学特征及控制因素

分析高原河流地表水中锶(Sr)富集的水化学特征及其影响因素,有助于指导水资源的合理开发利用和生态环境保护.以金沙江多曲河流域地表水为例,采集地表水样品23组,综合利用相关分析、主成分分析、Gibbs模型和离子比等方法,分析该区地表水中Sr²⁺富集的水化学特征及控制因素,识别主要离子的物质来源.结果表明,多曲河流域地表水阳离子主要以Ca²⁺和Mg²⁺为主,阴离子以HCO₃^-为主.该流域水化学类型以HCO₃-Ca型为主,其次为HCO₃-Ca·Mg型.主成分分析揭示了影响多曲河水质演化的3个主成分因子,碳酸盐岩风化溶解是控制多曲河水化学组成的主要因素.ρ(Sr²⁺)超过0.40 mg·L^-1的富Sr水点占样品总量的30.43%.区内分布的闪长岩及花岗岩为多曲河流域Sr²⁺富集提供了物质基础.Sr²⁺与Ca²⁺相关性较高,二者存在伴生...     

叶面喷施纳米MnO2对水稻富集镉的影响机制

镉（Cd）容易被水稻富集,从而造成稻米中Cd含量超标,严重威胁人类健康.锰（Mn）是植物必需元素,为了探究叶面喷施纳米MnO₂对水稻富集Cd的影响机制,本研究在酸性Cd污染土壤上进行田间小区试验,在水稻抽穗早期叶面喷施0.1%、0.3%和0.5%的纳米MnO₂溶液.结果表明与对照组相比,叶面喷施不同浓度的纳米MnO₂可以有效降低水稻叶、壳和糙米中的Cd含量,增加所有部位的Mn含量,但对水稻的产量影响不大.叶面喷施纳米MnO₂后,提高了叶片光合作用效果,抑制了叶片脂质过氧化,增加了氧化应激酶的含量,从而缓解Cd对水稻的胁迫.此外,叶面喷施纳米MnO₂增加了水稻根表铁锰胶膜的含量,强化了铁锰胶膜对Cd的吸附/共沉淀作用,从而限制水稻根系吸收Cd.因此,在水稻抽穗早期叶面喷施纳米MnO₂是一种增加糙米中Mn含量和减少Cd含量的有效措施.     

Relationship between heavy metal concentrations of herbaceous plants and soils at four Pb-Zn mining sites in Yunnan, China

This paper studied the relationship between heavy metal concentrations of herbaceous plants and soils at four Pb-Zn mining sites in Yunnan, China. 50 herbaceous plant samples of 9 plant species from 4 families and 50 soil samples were collected and then ana1yzed for the tota1 concentrations of Pb, Cd, and Zn. The results showed that the average concentrations of Pb, Cd, and Zn in soil samples were 3772.83, 168.81, and 5385.65 mg/kg, respectively. The average concentrations of Pb, Cd, and Zn were 395.68, 28.14, and 1664.20 mg/kg in the shoots, and 924.12, 57.25, and 1778.75 mg/kg in the roots, respectively. Heterospecific plants at the same site and conspecific plants at various sites had different average levels of Pb, Cd, and Zn, both in the shoots and the roots. Enrichment coefficients of Pb, Cd, and Zn were greater than 1 in 2, 3, and 9 herbaceous plant samples, respectively. Translocation factors of Pb, Cd, and Zn were greater than 1 in 10, 17, and 25 herbaceous plant samples, respectively. In all 50 samples, the concentrations of Pb, Cd, and Zn between the shoots and the roots, the shoots, and the soils, and the roots and the soils had significant positive relationships.     

Impact of medical fitness to drive policies in preventing property damage,injury, and death from motor vehicle collisions in Ontario,Canada

Introduction: Drivers with medical conditions and functional impairments are at increased collision risk. A challenge lies in identifying the point at which such risk becomes unacceptable to society and requires mitigating measures. This study models the road safety impact of medical fitness-to-drive policy in Ontario. Method: Using data from 2005 to 2014, we estimated the losses to road safety incurred during the time medically-at-risk drivers were under review, as well as the savings to road safety accrued as a result of licensing decisions made after the review process. Results: While under review, drivers with medical conditions had an age- and sex-standardized collision rate no different from the general driver population, suggesting no road safety losses occurred (RR = 1.02; 95% CI: 0.93–1.12). Licensing decisions were estimated to have subsequently prevented 1,211 (95% CI: 780–1,730) collisions, indicating net road safety savings resulting from medical fitness to drive policies. However, more collisions occurred than were prevented for drivers with musculoskeletal disorders, sleep apnea, and diabetes. We theorize on these findings and discuss its multiple implications. Conclusions: Minimizing the impact of medical conditions on collision occurrence requires robust policies that balance fairness and safety. It is dependent on efforts by academic researchers (who study fitness to drive); policymakers (who set driver medical standards); licensing authorities (who make licensing decisions under such standards); and clinicians (who counsel patients on their driving risk and liaise with licensing authorities). Practical Applications: Further efforts are needed to improve understanding of the effects of medical conditions on collision risk, especially for the identified conditions and combinations of conditions. Results reinforce the value of optimizing the processes by which information is solicited from physicians in order to better assess the functional impact of drivers’ medical conditions on driving and to take suitable licensing action.     

Transmembrane transport of polycyclic aromatic hydrocarbons by bacteria and functional regulation of membrane proteins

• Explaintheadsorption, uptake and transmembrane transport of PAHs by bacteria. • Analyze functional regulation of membrane proteins inthe transmembrane transport. • Proteomics technology such as iTRAQ labeling was used to access expressed proteins. • Single cell analysis technology wereused to study the morphological structure. In recent years, increasing research has been conducted on transmembrane transport processes and the mechanisms behind the microbial breakdown of polycyclic aromatic hydrocarbons (PAHs), including the role of membrane proteins in transmembrane transport and the mode of transmission. This article explains the adsorption, uptake and transmembrane transport of PAHs by bacteria, the regulation of membrane protein function during the transmembrane transport. There are three different regulation mechanisms for uptake, depending on the state and size of the oil droplets relative to the size of the microbial cells, which are (i) direct adhesion, (ii) emulsification and pseudosolubilization, and (iii) interfacial uptake. Furthermore, two main transmembrane transport modes are introduced, which are (i) active transport and (ii) passive uptake and active efflux mechanism. Meanwhile, introduce the proteomics and single cell analysis technology used to address these areas of research, such as Isobaric tags for relative and absolute quantitation (iTRAQ) technology and Nano Secondary ion mass spectrometry (Nano-SIMS). Additionally, analyze the changes in morphology and structure and the characteristics of microbial cell membranes in the process of transmembrane transport. Finally, recognize the microscopic mechanism of PAHs biodegradation in terms of cell and membrane proteins are of great theoretical and practical significance for understanding the factors that influence the efficient degradation of PAHs contaminants in soil and for remediating the PAHs contamination in this area with biotechnology.