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排序方式: 共有279条查询结果,搜索用时 15 毫秒
61.
以纳米银(AgNPs)作为典型的纳米颗粒物,利用非对称流场流分离技术构建纳米颗粒物的分离监测方法。制备了柠檬酸盐稳定的AgNPs分散液,采用透射电镜、紫外可见分光光度计、Zeta电位分析仪对AgNPs分散液进行了表征。结果表明,AgNPs半径多数小于10 nm,最大吸收波长为400 nm,Zeta电位为-42.56 m V。采用非对称流场流分离仪对AgNPs进行粒径分离,得到UV-Vis信号谱图,并收集得到半径小于10 nm、10~30 nm、30~50 nm、50~70 nm、70~100nm范围的AgNPs颗粒,结合电感耦合等离子体质谱仪测定每个粒径范围内AgNPs的质量浓度。结果表明,该方法重现性良好,AgNPs在半径小于10 nm的范围内达到了UV-Vis吸收峰值,响应信号最高为0.022 5~0.027 5 V,表明半径小于10 nm的AgNPs浓度较高。半径小于10 nm、10~30 nm、30~50 nm、50~70 nm、70~100 nm范围内AgNPs的质量浓度分别为(1 021.86±61.74)μg/L、(323.23±45.83)μg/L、(72.90±32.14)μg/L、(44.64±9.28)μg/L、(39.12±5.04)μg/L,回收率为43.96%±0.84%。 相似文献
62.
Hangfeng Wu Jiayue Wang Yangjie Ou Binbin Li Wusheng Jiang Donghua Liu 《毒物与环境化学》2017,99(5-6):913-925
This study deals with the characterisation of early responses of roots of Salix matsudana in respect to oxidative stress, subcellular distribution, and chemical forms when exposed to 50 μmol/L Cd. Within 12 h, the root length is reduced and the contents of O2??, H2O2, and malondialdehyde are increased by 49%, 43%, and 35%. Cd is mainly retained in the cell walls; small amounts are distributed into other cell organelles. The largest proportion of Cd is found in the NaCl extractable, pectate-, and protein-integrated fraction. 相似文献
63.
This work focuses on the influence of humic acids (HAs) on the fate of carbon nanotubes (CNTs) in aqueous media. This influence was demonstrated by mixing CNT powder with HAs in aqueous solution in varying concentrations. The aqueous media containing HAs and CNTs were size-characterized by asymmetrical flow field-flow fractionation (AsFlFFF) coupled with multi-angle light scattering (MALS). This coupling yielded information concerning the size distribution of single- and multi-walled CNTs (SWCNTs and MWCNTs) and HAs under different physico-chemical conditions that can occur in environmental water. HAs can disperse individual CNTs in aqueous media. However, the difference in the physical structure between SWCNTs and MWCNTs leads to significant differences in the quantity of HA that can adsorb onto the nanotube surface and in the stability of the CNT/HA complex. Compared with MWCNTs, SWCNTs suspended in HAs are less affected by changing ionic strength with respect to stability and the amount suspended. 相似文献
64.
Size and resin fractionations of dissolved organic matter and trihalomethane precursors from four typical source waters in China 总被引:3,自引:0,他引:3
Wei Q Wang D Wei Q Qiao C Shi B Tang H 《Environmental monitoring and assessment》2008,141(1-3):347-357
Dissolved organic matter (DOM) and its potential to form disinfection by-products (DBPs) during drinking water treatment raise
challenges to water quality control. Understanding both chemical and physical characteristics of DOM in source waters is key
to better water treatment. In this study, the DOM from four typical source waters in China was fractionated by XAD resin adsorption
(RA) and ultrafiltration (UF) techniques. The trihalomethane formation potential (THMFP) of all fractions in the DOM were
investigated to reveal the major THM precursors. The fraction distributions of DOM could be related to their geographical
origins in a certain extent. The dominant chemical fraction as THM precursors in the DOM from south waters (East-Lake reservoir
in Shenzhen and Peal rivers in Guangzhou) was hydrophobic acid (HoA). The size fraction with molecular weight (MW) <1 kDa
in both south waters had the highest THMFP. The results of cluster analysis showed that the parameters of fractions including
DOC percentage (DOC%), UV254%, SUVA254 (specific UV254 absorbance) and THMFP were better for representing the differences of DOM from the studied waters than specific THMFP (STHMFP).
The weak correlation between SUVA254 and STHMFP for either size or XAD fractions suggests that whether SUVA254 can be used as an indicator for the reactivity of THM formation is highly dependent on the nature of organic matter. 相似文献
65.
66.
本研究利用荧光区域积分法考察了在水体冻结过程中,溶解性有机物(DOM)组分中荧光物质的迁移转化.同时,利用XAD树脂,将DOM分为3个部分:疏水性有机酸(HPO-A)、过渡亲水性有机酸(TPI-A)和亲水性有机物(HPI).结果表明,在水体冻结过程中,HPO-A、TPI-A和HPI的DOC浓度在水相中逐渐增加,而在冰相中先减少后增加,并且这3种DOM组分在冰、水两相间的分配系数排序为:HPITPI-AHPOA.在水体冻结过程中,水相中HPO-A和HPI的总累计荧光强度(ΦT,n)值,以及冰相中3种DOM组分的总ΦT,n值随冻结时间的变化趋势均为先降低后升高.在水体冻结过程中,水相中3种DOM组分的类腐殖酸荧光峰发生蓝移.冻融作用导致HPO-A和HPI的荧光性降低.与HPO-A和HPI相比,TPI-A的荧光性受冻融作用的影响相对较小.此外,在4类荧光物质中,冻融作用对DOM组分中的类富里酸荧光物质和类腐殖酸荧光物质的影响较显著. 相似文献
67.
Arsenic fractionation and contamination assessment in sediments of thirteen lakes from the East Plain and Yungui Plateau Ecoregions, China 总被引:2,自引:0,他引:2
Fengyu Zan Shouliang Huo Jingtian Zhang Li Zhang Beidou Xi Lieyu Zhang 《环境科学学报(英文版)》2014,26(10):1977-1984
Arsenic(As) fractions in the sediments of seven lakes from East Plain Ecoregion and six lakes from Yungui Plateau Ecoregion, China, were investigated. Results indicated that the total As concentrations in sediment samples of lakes of the East Plain Lake Ecoregion are higher than those of Yungui Plateau Lake Ecoregion. Residual As is the main fraction in sediment samples of lakes from both ecoregions, followed by reducible As and soluble or oxidizable As. The total As is correlated to oxidizable As and residual As in sediment samples from both lake ecoregions. As distribution in sediment samples of lakes of the East Plain Ecoregion appears to be affected by human activity, while the As origin mainly comes from natural sources in sediment samples of lakes in the Yungui Plateau Ecoregion. The potential ecological risk index and geoaccumulation index values suggest "low to moderate" risk degree and "unpolluted to moderately polluted" for As in the studied lake sediments. 相似文献
68.
锌同位素是示踪植物中锌地球化学的重要手段,详细了解植物中锌同位素的分馏过程是探究其生物地球化学的关键。本文对目前研究程度较高的超富集植物、普通植物的锌同位素分馏成果进行了系统的总结,发现二者锌同位素分馏趋势基本一致,即相比于培养液或土壤的同位素组成,植物根部相对富集锌的重同位素,而植物地上部(如茎、叶等组织器官)相对富集锌的轻同位素。对于能够引起植物发生锌同位素分馏的因素归纳如下:(1)植物根部相对富集锌的重同位素,是土壤中锌的形态、根部对锌的吸收方式、细胞表面吸附共同作用的结果;(2)植物木质部对锌的向上运输,会随着传输距离的增加而使地上部组织器官相对富集锌的轻同位素;(3)大气沉降也可能导致叶片富集锌的轻同位素。 相似文献
69.
南京市城市污泥和工业污泥中典型矿质元素含量和形态分布研究 总被引:1,自引:0,他引:1
采用三态连续提取法研究南京市部分城市污泥和工业污泥中典型矿质元素的含量和形态分布,为污泥资源化的合理利用提供科学参考.结果表明,污泥总体呈高有机质、高氮磷、低K的相似性,但其理化性质如阳离子交换容量(CEC)、pH等有差异.污泥中不同矿质元素含量差异也较大,Fe的浓度最高,其次是Mg、Zn;且不同污泥间同一矿质元素含量的差异也较大.各元素的形态分布有一定差异,Cu主要分布在可氧化态,其酸溶/交换态和可还原态的百分率很低;Zn三态分布均较高;Mg、Mn主要分布在酸溶/交换态;Fe主要分布在残渣态.但三种提取形态百分率之和除Fe外均超过50%.研究同时表明,城市污泥和工业污泥中矿质元素形态分布无显著性差异. 相似文献
70.
Xian Q Chen H Liu H Zou H Yin D 《Environmental science and pollution research international》2006,13(4):233-237