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81.
膜萃取-微扑集/气相色谱-质谱测定小体积水样中痕量苯系物的方法 总被引:4,自引:0,他引:4
用膜萃取-微脯集/气相色谱-质谱分析方法,分别测定环境地表水,工厂排污水,饮用水和汽油等样品中痕量苯,甲苯和甲苯等有机污染物。结果表明,膜萃取,微捕集回收率为89%-99%,相对标准偏差为1.16-3.60%。 相似文献
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83.
50Hz低频环境磁场对细胞增殖的影响及其机理探讨 总被引:8,自引:0,他引:8
本文以细胞株LO2(人肝细胞)和CHL(中国仓鼠肺成纤维细胞)为研究对象,用50Hz正弦磁场以不同强度、不同时间作用于细胞。长时间作用后,2种细胞的增殖均受到抑制,但抑制程度与磁场作用量并非呈简单的线性关系;磁场短时间作用对细胞增殖无明显影响,但细胞膜的流动性变差,在磁场撤去后膜的流动性又有所恢复。这一现象说明,低频弱磁场引起宏观生物效应需要时间的积累。同时观察到磁场短时间作用导致的CHL细胞上表皮生长因子受体(EGFR)的聚集,这可能是低频弱磁场引起宏观生物效应的一种机制。 相似文献
84.
Traditional culture methods may underestimate the tolerance of microorganisms to disinfectants because of the existence of viable but nonculturable or sublethally injured cells after disinfection.The selection of a strict method is crucial for the evaluation of disinfection performance.The actions of 2 typical disinfectants–ultraviolet(UV)and chlorine–on the fecal indicator Escherichia coli were investigated by the detection of culturability,membrane permeability,metabolic activity,deoxyribonucleic acid(DNA),and messenger ribonucleic acid(m RNA).During UV disinfection,the irreversible damages in the cell membrane and cellular adenosine triphosphate(ATP)were negligible at low UV doses(80 m J/cm~2).However,membrane permeability was damaged at low doses of chlorine(5 mg/L),leading to leakage of cellular ATP.Our study showed that a slight lesion in DNA was detected even at high doses of UV(400 m J/cm~2)and chlorine(5 mg/L)treatments.The decay of m RNA was more rapid than that of DNA.The degradation level of m RNA depended on the choice of target genes.After exposure to 50 m J/cm~2UV dose or 5 mg/L chlorine for30 min,the DNA damage repair function(Rec A m RNA)was inhibited.The m RNA involved in the DNA damage repair function can be a potential indicator of bacterial viability. 相似文献
85.
As a routine measurement to alleviate membrane fouling, hydraulic cleaning is of great significance for the steady operation of ultrafiltration (UF) systems in water treatment processes. In this work, a comparative study was performed to investigate the effects of the composition of backwash water on the hydraulic cleaning performance of UF membranes fouled by humic acid (HA). Various types of backwash water, including UF permeate, Milli-Q water, NaCl solution, CaCl2 solution and HA solution, were compared in terms of hydraulically irreversible fouling index, total surface tension and residual HA. The results indicated that Milli-Q water backwash was superior to UF permeate backwash in cleaning HA-fouled membranes, and the backwash water containing Na+ or HA outperformed Milli-Q water in alleviating HA fouling. On the contrary, the presence of Ca2 + in backwash water significantly decreased the backwash efficiency. Moreover, Ca2 + played an important role in foulant removal, and the residual HA content closely related to the residual Ca2 + content. Mechanism analysis suggested that the backwash process may involve fouling layer swelling, ion exchange, electric double layer release and competitive complexation. Ion exchange and competitive complexation played significant roles in the efficient hydraulic cleaning associated with Na+ and HA, respectively. 相似文献
86.
Yuanzhi Hu Qian Yang Yang Guo Jie Xu Wenfeng Zhou Jing Li Ernest R. Blatchley 《环境科学学报(英文版)》2020,32(6):256-263
Volatile organic chloramines are reported as the disinfection byproducts during chlorination or chloramination.However,ClO_2,as an important alternative disinfectant for chlorine,was not considered to produce halogenated amines.In the present work,volatile organic chloramines including(CH_3)_2 NCl and CH_3 NCl_2 were found to be generated during the reaction of ClO_2 and the dye pollutants.(CH_3)_2 NCl was the dominant volatile DBP to result from ClO_2 treated all four dye pollutants including Methyl Orange,Methyl Red,Methylene Blue and Malachite Green,with molar yields ranging from 2.6% to 38.5% at a ClO_2 to precursor(ClO_2/P) molar ratio of 10.HOCl was identified and proved to be the reactive species for the formation of (CH_3)_2 NCl,which implied(CH_3)_2 NCl was transformed by a combined oxidation of ClO_2 and hypochlorous acid.(CH_3)_2 NCl concentrations in the ppb range were observed when real water samples were treated by ClO_2 in the presence of the dye pollutants.The results suggest that these azo dyes are one of the significant precursors for the formation of HOCl during ClO_2 treatment and that organic chloramines should be considered in ClO_2 disinfection chemistry and water treatment. 相似文献
87.
Yanjun Zhang Changwei Zhao Shaofeng Zhang Ling Yu Jiding Li Li-an Hou 《环境科学学报(英文版)》2019,31(4):183-192
The lack of fresh water in the world makes the search for an effective method to decontaminate water an urgent priority. An important step is to remove different multivalent ions in salt treatment. Nanofiltration (NF) has been used for treating water containing different kinds of salts. In this work, sulfonate group-modified graphene oxide (SGO) was prepared, and added during the interfacial polymerization (IP) reaction to prepare SGO-modifiedNF membranes (PA-SGO). The chemical composition, structure and surface properties of PA and PA-SGO membranes were characterized by FT-IR, XPS, SEM, AFM, contact angle and zeta potential measurements. Their water flux, salt rejection and anti-fouling abilities were investigated systematically. The testing results showed that the water flux of PA-SGO (0.03% SGO) was 45.85 LMH under a pressure of 0.2?MPa, and the salt rejection varied in the order of Na2SO4 (98.99%)?>?MgSO4 (91.25%)?>?MgCl2 (42.27%)?>?NaCl (21.96%). An anti-fouling experiment indicated that the PA-SGO membrane had good anti-fouling properties because of its decreased roughness and increased hydrophilicity and electronegativity. The PA-SGO membrane has good potential for use in removing salt ions from water. 相似文献
88.
开发膜生物反应器的经济技术因素探讨 总被引:8,自引:0,他引:8
经济因素是制约膜生物反应器废水处理工艺发展的关键,影响经济性的直接原因是能耗,间接原因是膜受污染失效。MBR中降解有机物的主要手段仍是生物反应器,膜分离对生物反应器起到了独特的强化作用,但必须考虑适当的运行条件,否则会带来负面效应。 相似文献
89.
90.
The immunodeficiency associated with a defective expression of HLA molecules is an autosomal recessive disorder leading to death during childhood. We have performed prenatal diagnosis for six fetuses at risk for this disease by membrane immunofluorescence on blood lymphocytes and monocytes, using specific monoclonal antibodies for HLA class I and II molecules. Two pregnancies have been found to be affected. The diagnosis has been confirmed on each abortus by the study of the membrane expression of HLA class I and II molecules on blood lymphocytes and monocytes, and on thymic and splenic cells. The four other cases were found to be normal both during pregnancy and after birth. The detection of the defect as early as the 20th week of gestation allows selective termination. 相似文献