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81.
Biological degradation of dissolved organic matter(DOM) regulates its structure and fate in river ecosystems. Previous views suggested that labile components were dominantly consumed by microbial metabolism. Here we provide new observations that a part of recalcitrant compounds largely contribute to riverine DOM biodegradation. The excitationemission matrix fluorescent spectroscopy combined with peak picking and parallel factor analysis are used to explore component variability during DOM incuba... 相似文献
82.
Jin Zhang Fanhao Song Tingting Li Kefu Xie Huiying Yao Baoshan Xing Zhongyu Li Yingchen Bai 《环境科学学报(英文版)》2020,32(4):310-320
Simulated photo-degradation of fluorescent dissolved organic matter(FDOM) in Lake Baihua(BH) and Lake Hongfeng(HF) was investigated with three-dimensional excitationemission matrix(3 DEEM) fluorescence combined with the fluorescence regional integration(FRI),parallel factor(PARAFAC) analysis,and multi-order kinetic models.In the FRI analysis,fulvic-like and humic-like materials were the main constituents for both BH-FDOM and HF-FDOM.Four individual components were identified by use of PARAFAC analysis as humic-like components(C1),fulvic-like components(C2),protein-like components(C3) and unidentified components(C4).The maximum 3 DEEM fluorescence intensity of PARAFAC components C1-C3 decreased by about 60%,70% and 90%,respectively after photo-degradation.The multi-order kinetic model was acceptable to represent the photo-degradation of FDOM with correlation coefficient(R_(adj)~2)(0.963-0.998).The photo-degradation rate constants(k_n) showed differences of three orders of magnitude,from 1.09 x 10~(-6) to 4.02 x 10~(-4) min-1,and half-life of multi-order model(T_(1/2)~n)ranged from 5.26 to 64.01 min.The decreased values of fluorescence index(FI) and biogenic index(BI),the fact that of percent fluorescence response parameter of Region I(P_(Ⅰ,n)) showed the greatest change ratio,followed by percent fluorescence response parameter of Region II(P_(Ⅱ,n),while the largest decrease ratio was found for C3 components,and the lowest T_(1/2)~n was observed for C3,indicated preferential degradation of protein-like materials/components derived from biological sources during photodegradation.This research on the degradation of FDOM by 3 DEEM/FRI-PARAFAC would be beneficial to understanding the photo-degradation of FD OM in natural environments and accurately predicting the environmental behaviors of contaminants in the presence of FDOM. 相似文献
83.
Hao Chen Renzhi Hu Pinhua Xie Xingbiao Xing Liuyi Ling Zhiyan Li Fengyang Wang Yihui Wang Jianguo Liu Wenqing Liu 《环境科学学报(英文版)》2018,30(3):190-200
An OH radical measurement instrument based on Fluorescence Assay by Gas Expansion(FAGE)has been developed in our laboratory.Ambient air is introduced into a low-pressure fluorescence cell through a pinhole aperture and irradiated by a dye laser at a high repetition rate of 8.5 k Hz.The OH radical is both excited and detected at 308 nm using A-X(0,0)band.To satisfy the high efficiency needs of fluorescence collection and detection,a 4-lens optical system and a self-designed gated photomultiplier(PMT)is used,and gating is actualized by switching the voltage applied on the PMT dynodes.A micro channel photomultiplier(MCP)is also prepared for fluorescence detection.Then the weak signal is accumulated by a photon counter in a specific timing.The OH radical excitation spectrum range in the wavelength of 307.82–308.2 nm is detected and the excited line for OH detection is determined to be Q_1(2)line.The calibration of the FAGE system is researched by using simultaneous photolysis of H_2O and O_2.The minimum detection limit of the instrument using gated PMT is determined to be 9.4×10~5molecules/cm~3,and the sensitivity is 9.5×10~(-7)cps/(OH·cm~(-3)),with a signal-to-noise ratio of 2 and an integration time of 60 sec,while OH detection limit and the detection sensitivity using MCP is calculated to be 1.6×10~5molecules/cm~3and 2.3×10~(-6)cps/(OH·cm~(-3)).The laboratory OH radical measurement is carried out and results show that the proposed system can be used for atmospheric OH radical measurement. 相似文献
84.
Fanhao Song Fengchang Wu Weiying Feng Zhi Tang John P. Giesy Fei Guo Di Shi Xiaofei Liu Ning Qin Baoshan Xing Yingchen Bai 《环境科学学报(英文版)》2018,30(12):116-125
Structural characteristics and proton binding properties of sub-fractions (FA3–FA13) of fulvic acid (FA), eluted stepwise by pyrophosphate buffer were examined by use of fluorescence titration combined with fluorescence regional integration (FRI) and differential fluorescence spectroscopy (DFS). Humic-like (H-L) and fulvic-like (F-L) materials, which accounted for more than 80% of fluorescence response, were dominant in five sub-fractions of FA. Based on FRI analysis, except the response of F-L materials in FA9 and FA13, maximum changes in percent fluorescence response were less than 10% as pH was increased from 2.5 to 11.5. Contents of carboxylic and phenolic groups were compared for fluorescence peaks of FA sub-fractions based on pH-dependent fluorescence derived from DFS. Static quenching was the dominant mechanism for binding of protons by FA sub-fractions. Dissociation constants (pKa) were calculated by use of results of DFS and the modified Stern-Volmer relationship. The pKa of H-L, F-L, tryptophan-like and tyrosine-like materials of FA sub-fractions exhibited ranges of 3.17–4.06, 3.12–3.97, 4.14–4.45 and 4.25–4.76, respectively, for acidic pHs. At basic pHs, values of pKa for corresponding materials were in ranges of 9.71–10.24, 9.62–10.99, 9.67–10.31 and 9.33–10.28, respectively. At acidic pH, protein-like (P-L) materials had greater affinities for protons than did either H-L or F-L materials. The di-carboxylic and phenolic groups were likely predominant sites of protonation for both H-L and F-L materials at both acidic and basic pHs. Amino acid groups were significant factors during proton binding to protein-like materials of FA sub-fractions at basic pH. 相似文献
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在pH值为5.0的HAc-NaAc缓冲溶液中,曙红在540 nm处产生一个荧光峰,并能被ClO2氧化导致其荧光发生猝灭.通过试验确定了ClO2使曙红褪色的最佳条件,ClO2在0.042 mg/L~0.916 mg/L范围内与曙红荧光猝灭强度呈线性关系,据此建立了水中ClO2的荧光分析方法,方法检出限为0.01 mg/L. 相似文献
89.
畜禽养殖废水的三维荧光特征 总被引:1,自引:0,他引:1
对某畜禽养殖废水连续采样,利用荧光光谱法研究畜禽养殖废水的三维荧光特性.结果表明:该废水的三维荧光光谱有两个荧光峰,分别为270 nm/297 nm和315 nm/410 nm,两峰的强度之比为3.45~4.94;该畜禽养殖废水由蛋白质、腐酸、尿液及阴离子表面活性剂组成;各峰的峰位置及峰强度比值都可作为判断废水是否为该... 相似文献
90.
A synchronous fluorescence spectroscopy (SFS) method was developed for determination of pyrene in the gills of exposed fish. The wavelength differences (Δλ) of 50 nm was maintained between excitation and emission wavelengths and it was found to be suitable for the effective determination of pyrene in fish gills; the peak were observed at λex 334.5 nm. Linear relationships between SFS intensity and the concentration of pyrene in n-hexane solution were established. It was demonstrated that the SFS method was effective, simple, and less expensive, providing an attractive alternative for the rapid analysis of pyrene in fish gills. 相似文献