Mercury uptake by Paspalum distichum L. in relation to the mercury distribution pattern in rhizosphere soil

Environmental Science and Pollution Research - Paspalum distichum L. was tested to evaluate their phytoremediation capacity for Hg contaminated soil through analyzing the dissipation of Hg in soil...     

Salinity and nutrient modulate soil bacterial communities in the coastal wetland of the Yellow River Delta,China

The Yellow River Delta is the largest and youngest estuarine and coastal wetland in China and is experiencing the most active interactions of seawater and freshwater in the world. Bacteria played multifaceted influence on soil biogeochemical processes, and it was necessary to investigate the intermodulation between the soil factors and bacterial communities. Soil samples were collected at sites with different salinity degree, vegetations, and interference. The sequences of bacilli were tested using 16S rRNA sequencing method and operational taxonomic units were classified with 97% similarity. The soil was highly salinized and oligotrophic, and the wetland was nitrogen-restricted. Redundancy analysis suggested that factors related with seawater erosion were principal to drive the changes of soil bacterial communities and then the nutrient level and human disturbance. A broader implication was that, in the early succession stages of the coastal ecosystem, seawater erosion was the key driver of the variations of marine oligotrophic bacterial communities, while the increasing nutrient availability may enhance in the abundance of the riverine copiotrophs in the late stages. This study provided new insights on the characteristics of soil bacterial communities in estuarine and coastal wetlands.

     

Effect of oxide nanoparticles on the morphology and fluidity of phospholipid membranes and the role of hydrogen bonds

Engineered oxide nanoparticles (NPs) are widely applied in insulators, catalyzers, paints, cosmetic products, textiles and semiconductors. Their attachment on cell membrane may lead to cytotoxicity. The effects of Al₂O₃, Fe₂O₃, SiO₂, TiO₂ and ZnO NPs on membrane integrity and fluidity were studied using giant or small unilamellar vesicles in this study. Al₂O₃ and SiO₂ NPs disrupted the oppositely charged membrane, indicating the important role of electrostatic attraction. However, Fe₂O₃, TiO₂ and ZnO NPs did not cause serious membrane disruption as Al₂O₃ and SiO₂ NPs. Membrane fluidity was evaluated by the generalized polarity (GP) values of Laurdan fluorescent emission. SiO₂ NPs induce the membrane gelation of both positively and negatively charged membrane. Al₂O₃ and ZnO NPs induced the gelation of the oppositely charged membrane, but did not cause obvious membrane gelation to the like charged membrane. The phospholipid molecular structural changes after NP exposure were analyzed by Fourier transform infrared (FT-IR) spectroscopy. FT-IR spectra revealed the hydrogen bond formation between NPs and the carbonyl/phosphate groups of phospholipids. Al₂O₃ and SiO₂ NPs showed strongest evidence of hydrogen bonding on their FT-IR spectra. It was consistent with the microscopic observation and fluorescent data that Al₂O₃ and SiO₂ NPs caused more serious membrane disruption and gelation. This study on membrane damage provides further knowledge on the cytotoxicity of nanomaterials and the safety of NP application.     

Effects of sludge retention time, carbon and initial biomass concentrations on selection process: From activated sludge to polyhydroxyalkanoate accumulating cultures

Four sequence batch reactors (SBRs) fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding (ADF) mode with different configurations of sludge retention time (SRT), carbon and initial biomass concentrations to enrich polyhydroxyalkanoate (PHA) accumulating mixed microbial cultures (MMCs) from municipal activated sludge. The stability of SBRs was investigated besides the enrichment performance. The microbial community structures of the enriched MMCs were analyzed using terminal restriction fragment length polymorphism (T-RFLP). The optimum operating conditions for the enrichment process were: SRT of 5 days, carbon concentration of 2.52 g COD/L and initial biomass concentration of 3.65 g/L. The best enrichment performance in terms of both operating stability and PHA storage ability of enriched cultures (with the maximum PHA content and PHA storage yield (Y_PHA/S) of 61.26% and 0.68 mg COD/mg COD, respectively) was achieved under this condition. Effects of the SRT, carbon concentration and initial biomass concentration on the PHA accumulating MMCs selection process were discussed respectively. A new model including the segmentation of the enrichment process and the effects of SRT on each phase was proposed.     

湖北省PM2.5与PM10比值分析及PM2.5时空分布特征研究

基于2012年-2014年湖北省大气污染物监测数据,通过数据反演方法,得到湖北省17个城市的PM2.5年均浓度.利用ArcGIS绘制出各城市不同年份的颗粒物浓度空间分布图,并对其进行分析.结果表明,2012年-2014年间,湖北省17个城市PM2.5与PM10年均浓度比值为0.66,PM2.5年均浓度超出国家二级标准,整体呈现上升趋势.城市方面,在多数城市PM2.5与PM10浓度上升的同时,仅武汉、黄冈和天门3个城市颗粒物浓度2014年较2013年有所下降,且武汉市PM2.5浓度下降率达12.8%,表明武汉市近两年来采取的政策措施具有较好的可行性和有效性.     

环境规划实施评估指标体系研究

环境规划指标体系是环境规划的核心内容,具有重要意义.环境规划能否切实发挥重要功能,与其规划实施评估有着密不可分的关系.环境规划评估指标体系的建立有利于系统有效地分析和评估环境规划实施效果和问题.通过分析定性评估、定量评估、层次分析法、逻辑框架法等评估方法,并实证分析环境规划评估指标体系的建立,对比分析发现,逻辑框架法可有效地分析环境规划实施过程中存在的问题,从而从总体上构建评估指标体系,可为环境规划的实施评估提供有效的参考.     

新型ISTD反应器处理污水处理厂污泥的试验研究

针对传统的污泥处理方法存在消化时间长、投资及运行费用高、运行管理较复杂等问题,开发了污泥同时浓缩与消化——新型ISTD反应器,并对城市污水厂剩余污泥进行试验研究。试验结果表明:在30³5℃,COD有机负荷0.65 kg/(m3·d),水力停留时间5 d的条件下,有机物分解率为53.88%,排泥含水率为91.91%,出水SS平均为612 mg/L。     

电除尘器中水雾雾化特性及对除尘性能的影响

湿式电除尘器将水雾除尘与电除尘技术相结合,可以有效地对细颗粒物进行收集,抑制了二次扬尘的发生。通过研究电除尘器喷淋系统的雾化特性,以及不同供水压力对水雾荷电的影响,并测得其分级效率。研究结果表明:在供水压力为0.4 MPa时,湿式电除尘器的除尘效率大于99.5%;在喷雾粒径为100μm时,对10μm以下的细颗粒物除尘效率大于92%。通过分析,为湿式除尘器喷淋系统设计提供了依据。     

Formation of THMs and HANs during bromination of Microcystis aeruginosa

Bromine-contained disinfectants and biocides are widely used in swimming pools, recreational waters and cooling towers. The objective of this study was to evaluate the formation of thrihalomethanes (THMs) and haloacetonitriles (HANs) and their cytotoxicity in algae solutions during free bromine disinfection. Disinfection by-products formation potential experiments were conducted using model solutions containing 7 mg/L (as total organic carbon) Microcystis aeruginosa cells. Effects of free bromine dosage, pH and ammonia were investigated. The results showed that brominated disinfection by-products were the major products when free bromine was applied. The total THMs formed during bromination was much as that formed during chlorination, whereas HANs were elevated by using bromination instead of chlorination. Dibromoacetonitrice (C2H2NBr2 ) and bromoform (CHBr3 ) were the only detected species during free bromine disinfection. The production of C2H2NBr2 and CHBr 3 increased with disinfectant dosage but decreased with dosing ammonia. CHBr3 increased with the pH changing from 5 to 9. However, C2H2NBr2 achieved the highest production at neutral pH, which was due to a joint effect of variation in hydrolysis rate and free bromine reactivity. The hydrolysis of C2H2NBr2 was base-catalytic and nearly unaffected by disinfectant. Finally, estimation of cytotoxicity of the disinfected algae solutions showed that HANs formation was responsible for the majority of toxicity. Considering its highest toxicity among the measured disinfection by-products, the elevated C2H2NBr2 should be considered when using bromine-related algaecide.     

Speciation of organic phosphorus in a sediment profile of Lake Taihu II. Molecular species and their depth attenuation

The understanding of organic phosphorus(P) dynamics in sediments requires information on their species at the molecular level,but such information in sediment profiles is scarce.A sediment profile was selected from a large eutrophic lake,Lake Taihu(China),and organic P species in the sediments were detected using solution phosphorus-31 nuclear magnetic resonance spectroscopy(31 P NMR) following extraction of the sediments with a mixture of 0.25 mol/L NaOH and 50 mmol/L EDTA(NaOH-EDTA) solution.The results showed that P in the NaOH-EDTA extracts was mainly composed of orthophosphate,orthophosphate monoesters,phospholipids,DNA,and pyrophosphate.Concentrations of the major organic P compound groups and pyrophosphate showed a decreasing trend with the increase of depth.Their half-life times varied from 3 to 27 years,following the order of orthophosphate monoesters > phospholipids DNA > pyrophosphate.Principal component analysis revealed that the detected organic P species had binding phases similar to those of humic acid-associated organic P(NaOH-NRP HA),a labile organic P pool that tends to transform to recalcitrant organic P pools as the early diagenetic processes proceed.This demonstrated that the depth attenuation of the organic P species could be partly attributed to their increasing immobilization by the sediment solids,while their degradation rates should be significantly lower than what were suggested in previous studies.