Physical-chemical and electrochemical characterization of Fe-exchanged natural zeolite applied for obtaining of hydrogen peroxide amperometric sensors     

《Chemie der Erde / Geochemistry》2014,74(4):653-660

This work demonstrates that a Fe-exchanged zeolitic volcanic tuff from Cepari (Fe/CV) (Bistrita-Nasaud County, Romania) is suitable for the amperometric detection of H₂O₂, using new modified carbon paste electrodes based on this material (Fe/CV-CPEs). The physical-chemical characterization of natural (CV) and modified (Fe/CV) forms was realized using chemical analysis, optical microscopy, scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transformed infrared (FTIR) spectroscopy. The resulting electrodes (Fe/CV-CPEs) were investigated using cyclic voltammetry and chronoamperometry measurements. The new electrodes showed good electrocatalytic activity toward H₂O₂ reduction. The calibration curve for H₂O₂ determination was linear up to 0.1 mM, with a detection limit (signal to noise ratio of 3) of 20 μM.  相似文献   

Environmental change and seasonal behavior of mastodons in the Great Lakes region inferred from stable isotope analysis     

Jessica Z. Metcalfe  Fred J. Longstaffe 《Quaternary Research》2014

We investigate seasonal variations in the diet and drinking water of four Great Lakes mastodon (Mammut americanum) specimens using stable isotope analysis of serially sampled inner-enamel bioapatite structural carbonate (δ¹³C_sc, δ¹⁸O_sc), and previously published bulk analyses. Isotopic analyses and thin section measurements showed that mastodon tooth enamel extension rates (~ 12–4 mm/yr, decreasing toward the cervix) were lower than those of mammoths or modern elephants. Mastodons had distinct and highly regular seasonal variations in δ¹³C_sc and δ¹⁸O_sc, which we interpret in the context of local glacial history and vegetation changes. Seasonal variations in δ¹⁸O were large but variations in δ¹³C were small, and may have been obscured if coarser sampling methods than our inner-enamel sampling approach were used. Thus, our approach may be particularly useful for understanding relatively small seasonal changes in δ¹³C within C₃ environments. The seasonal patterns, though not entirely conclusive, suggest that the Ontario mastodons did not migrate over very long distances. Rather, the climate and seasonal dietary patterns of mastodons within the region changed over time, from ~ 12,400 to 10,400 ¹⁴C yr BP (~ 15,000 – 12,000 cal yr BP). Insights gained using these methods can contribute to a better understanding of megafaunal extinctions and Paleoamerican lifeways.  相似文献   

Carbon Isotope Features of the Sugetbrak Section in the Aksu?Wushi Area, Northwest China: Implications for the Precambrian/Cambrian Stratigraphic Correlations     

YAO Chunyan  DING Haifeng  MA Dongsheng  LI Guoxiang 《《地质学报》英文版》2014,88(5):1535-1546

The upper Qigeblaq Formation （Fm） dolostones and the Yurtus Fm phosphatic cherts, black shales, limestones, and dolostones are widely distributed in the Precambrian/Cambrian transitional succession of the Aksu-Wushi area. Negative δ13C excursion above the Yurtus Fm/ Qigeblaq Fm boundary was determined in this study. The pronounced negative carbon isotope excursion occurs in the phosphatic chert layers at the bottom of the Cambrian Yurtus Fm, below which the first appearance of the Asteridium- Heh＇osphaeridium-Comasphaeridium （AHC） acritarch assemblage zone. The δ13C curve of the lower part of the Yurtus Fm in the Aksu-Wushi area was found to be correlated with the early Cambrian δ13C curves of the Zhujiaqing Fm （Daibu Member）, the lower part of the Yanjiahe Fm on the Yangtze Platform in China, the lower Tal Fm in India, the Sukharikha Fm in Siberia, and the upper part of the Tsagaan Oloom Fm in Mongolia through biostigraphy. The lower part of the Yurtus Fm in the Tarim Basin is at the Nemakit-Daldynian stage, and the Precambrian/Cambrian boundary of the Aksu-Wushi area may be located in the phosphatic chert unit which just below the first appearance AHC acritarch assemblage zone. The negative δ13C excursion （N1） across the Precambrian/Cambrian boundary in the studied section may have resulted from oceanic overturning and sea level rise.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987113001060     

Yunbo Zhang  Zongju Zhao  Genhou Wang  Zaixing Jiang  Mingjian Wang  Min Zheng  Shiben Zhang 《地学前缘(英文版)》2014,5(2):289-298

Type division and controlling factor analysis of 3rd-order sequence are of practical significance to tec-tonic analysis, sedimentary environment identification, and other geological researches. Based on the comprehensive analysis of carbon and oxygen isotope trends, paleobathymetry and spectral-frequency of representative well logs, 3rd-order sequences can be divided into 3 types： （a） global sea level （GSL） sequence mainly controlled by GSL change;（b） tectonic sequence mainly controlled by regional tectonic activity;and （c） composite sequence jointly controlled by GSL change and regional tectonic activity. This study aims to identify the controlling factors of 3rd-order sequences and to illustrate a new method for classification of 3rd-order sequences of the middle Permian strata in the Sichuan Basin, China. The middle Permian strata in the Sichuan Basin consist of 3 basin-contrastive 3rd-order sequences, i.e., PSQ1, PSQ2 and PSQ3. Of these, PSQ1 is a GSL sequence while PSQ2 and PSQ3 are composite sequences. The results suggest that the depositional environment was stable during the deposition of PSQ1, but was activated by tectonic activity during the deposition of the middle Permian Maokou Formation.  相似文献   

Design alternatives for a domestic carbon trading scheme in the United States     

K. John Holmes  Robert M. Friedman 《Global Environmental Change》2000,10(4)

One critical aspect of the Kyoto Protocol is its flexibility in compliance. Countries or groups of countries are free to choose their own implementation strategies. Should the United States ratify the Protocol, it will most likely use emissions trading in some form to implement this accord. Two variations on a US domestic carbon trading system are presented here. One is an auction system controlling carbon at the point of energy production and distribution. The second is a hybrid system allocating permits to large combustors and controlling smaller sources through standards. Within this paper we describe and compare the main attributes of each system. Separate sections also discuss various methods for allocating permits and incorporating standards.  相似文献   

光强对缘管浒苔(Ulva linza)光合生理特性和短期温度效应的影响     

付倩倩  李航霄  吴海龙  徐军田 《海洋与湖沼》2018,49(5):967-974

由于季节和分布深度的不同,海藻接受的光强和温度也不同,其生理响应机制也不同。本文旨在研究不同光强对缘管浒苔(Ulvalinza)光合生理特性及短期温度效应的影响。缘管浒苔样品采自连云港高公岛海区(119.3°E, 34.5°N)。实验设置了低、中、高三个不同水平的光强,分别为90、200和400μE/(m~2·s)。结果表明,藻体的净光合作用速率在低光下显著低于培养在高、中光下的,而光强对呼吸作用速率无显著影响。高光下藻体光系统Ⅱ的最大光化学效率(F_v/F_m)值显著低于中、低光强下,而非光化学淬灭(NPQ)值随光强降低显著下降。叶绿素a和叶绿素b的含量在低光强下均显著高于高、中光强下的含量。最大相对电子传递速率(rETR_(max))随光强变化显著,中光下最高,低光下最低;饱和光强(I_k)在低光下显著低于在高、中光下。在不同浓度的溶解性无机碳(DIC)下,净光合作用速率在不受碳限制时所能达到的最大速率(V_(max))随光强升高而显著增大,净光合作用速率为最大速率一半时的底物浓度(K_m)在低光下显著低于高、中光下。这表明低光上调了藻体的无机碳利用能力。短期温度实验表明,高光培养下,酶失活一半时的温度(T_h)显著增加,而低光下藻体的净光合作用速率的最适温度(T_(opt))显著降低,这表明低光显著提高了缘管浒苔对环境的敏感性,而高光下的藻体更适应高温的环境,这为绿潮在5—7月份大规模暴发的现象研究提供了一定的理论参考依据。  相似文献   

城市化、产业结构、能源消费、经济增长与碳排放的关联性分析——基于中国省际收入水平异质性的实证研究     

原嫄  孙欣彤 《气候变化研究进展》2020,16(6):738-747

在全国推崇节能减排,寻求低碳经济发展的大环境下,探究不同收入水平下各影响因子与碳排放的关联性有助于区域异质性碳减排政策的制定。根据2002—2016年的经济发展水平数据,将中国30个省及直辖市（不包含西藏及港、澳、台地区）划分为4个不同收入水平,分别建立面板向量自回归（PVAR）模型,并运用面板格兰杰因果检验、脉冲响应和方差分解探究城市化、产业结构、能源消费、经济增长与碳排放之间的关联性。研究结果表明,处于不同收入水平下的省份各影响因子与碳排放之间的关系存在异质性。收入水平较高的省份当前城市化水平已产生显著的减排效应,而欠发达地区仍处于城市化进程加速碳排放阶段;4个收入水平下能源消费均会长期影响碳排放,但欠发达地区更加需要摆脱能源依赖的经济发展路径,并且提高能源利用率从而降低碳排放;非高收入水平省份产业结构对碳排放造成的影响明显高于高收入水平省份。此外,实证结果表明,中国仍处于碳排放与经济发展的同步增长阶段,减排政策将会对经济增长产生负向反馈,故现有减排路径的选择需要高度审慎的设计与实施。  相似文献   

Particle export within cyclonic Hawaiian lee eddies derived from Pb–Po disequilibrium     

E. Verdeny  P. Masqu  K. Maiti  J. Garcia-Orellana  J.M. Bruach  C. Mahaffey  C.R. Benitez-Nelson 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1461

Particle export from the upper waters of the oligotrophic ocean may play a crucial role in the global carbon cycle. Mesoscale eddies have been hypothesized to inject new nutrients into oligotrophic surface waters, thereby increasing new production and particle export in otherwise nutrient deficient regimes. The E-Flux Program was a large multidisciplinary project designed to investigate the physical, biological and biogeochemical characteristics of cold-core cyclonic eddies that form in the lee of the Hawaiian Islands. There, we investigated particle dynamics using ²¹⁰Pb–²¹⁰Po disequilibrium. Seawater samples for ²¹⁰Pb and ²¹⁰Po were collected both within (IN) and outside (OUT) of two cyclones, Noah and Opal, at different stages of their evolution as well as from the eddy generation region. Particulate carbon (PC), particulate nitrogen (PN) and biogenic silica (bSiO₂) export fluxes were determined using water-column PC, PN, and bSiO₂ inventories and the residence times of ²¹⁰Po. PC and PN fluxes at 150 m ranged from 1.58±0.10 to 1.71±0.16 mmol C m⁻² d⁻¹ and 0.22±0.02 to 0.30±0.02 mmol N m⁻² d⁻¹ within Cyclones Opal and Noah. PC and PN fluxes at OUT stations sampled during both cruises were of similar magnitudes, 1.69±0.16 to 1.67±0.16 mmol C m⁻² d⁻¹ and 0.30±0.03 to 0.26±0.03 mmol N m⁻² d⁻¹. The bSiO₂ fluxes within Cyclone Opal were 0.157±0.010 mmol Si m⁻² d⁻¹ versus 0.025±0.002 mmol Si m⁻² d⁻¹ at OUT stations. These results of minimal PC and PN export, but significant eddy-induced bSiO₂ fluxes, agree very well with other studies that used a variety of direct and indirect methods. Thus, our results suggest that using elemental inventories and residence times of ²¹⁰Po is another independent and robust method for determining particle export and should be investigated more fully.  相似文献   

The diffusion coefficient of dissolved silica revisited   总被引：1，自引：0，他引：1  

Laura Rebreanu  Jean-Pierre Vanderborght  Lei Chou   《Marine Chemistry》2008,112(3-4):230-233

The diffusion coefficient of dissolved silica was determined for two different salinities, 36 and 0, at temperatures ranging from 2 °C to 30 °C and at an average pH value of 8.1. Our results show limited influence of salinity and a variation by a factor of 2 to 3 of the silica diffusion coefficient within the temperature range considered in this study. The values obtained at 25 °C are in agreement with previous work carried out at room temperature for seawater and freshwater. The dependency on temperature and viscosity of the diffusion coefficient agrees well with the Einstein–Stokes equation. The composition of the solvent appears to be an important factor because it modifies the viscosity and allows for the complexation of the dissolved silica with less mobile ions, while its pH controls the dissolved silica speciation. In seawater, the higher viscosity and the presence of dissociated and polymeric species result in a decrease of the diffusion coefficient compared to freshwater systems.  相似文献   

浅析碳汇渔业所需的碳交易市场规模——基于海洋渔业生产数据的测算   总被引：1，自引：0，他引：1       下载免费PDF全文

于梦璇  田天  马云瑞 《海洋开发与管理》2018,35(7):88-93

文章通过构建博弈模型,研究引导渔民将海水养殖量减少至可持续发展的最优水平的长、短期策略。从长期看,实现海水养殖可持续发展有提高生产技术、改变市场结构和发展碳汇渔业3种策略;从短期看,发展碳汇渔业见效更快。文章利用数值模拟方法,测算出为发展碳汇渔业,所需的碳汇市场需求规模为1 480万t。该结果与我国碳汇市场发展实际数据基本一致。说明当前我国碳汇市场规模已经足够庞大,可以有效容纳碳汇渔业所提供的碳汇供给。  相似文献