In this study, we have characterized three fluorescent components of dissolved organic matter (DOM) in the surface and underground water of one rare earth element ore district by excitation-emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC). Two protein-like components (C1, tyrosine and C2, tryptophan) and one humic-like component (C3) were identified by the DOM Fluor-PARAFAC model, with C3 constituting more than 95% of the total DOM, while C1 and C2 occupying a tiny fraction of DOM. The distribution of three PARAFAC-identified components was strongly influenced by the river direction, terrain and location of various water samples. The results suggested that DOM of samples collected from downstream or a central region had higher fluorescence intensity than those of upstream or surrounding the center. In addition, a negative linear correlation (R(2) = 0.8465) between pH (5.7-9.2) and fluorescence intensity of C3 was observed, indicating that the increase of pH might enhance the intensity of fluorescent humic-like substances. Although the fluorescence intensity of C1 and C2 was independent of pH changes, strong quenching effects of different heavy metals were presented for C1, and evident positive correlations between C2 and concentrations of rare earth metals (La, Ce, Tb, Dy, Tm, etc.) were observed, which showed that tyrosine-like (C1) and tryptophan-like (C2) substances were assumingly responsible for metal binding and adsorption in water, respectively. Based on EEM-PARAFAC modeling, all the fluorescence EEMs of samples could be decomposed into a three-component model, and their potential applications in water quality monitoring and metal-binding indicator were likely to be developed in the fluorescence analysis of natural water.

Arsenic (As) contamination of environmental water has attracted much attention in recent years, due to its high mobility and various species. In this work, water samples collected from Chenjiang, Liuyang, and Xiangjiang River, the most heavily Ascontaminated rivers in China, were investigated using size exclusion chromatography (SEC), combined with inductively coupled plasma mass spectrometry (ICP-MS), as well as three-dimensional excitation-emission matrix (3DEEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC). By EEM-PARAFAC modeling, all EEM peaks could be decomposed into a five-component model including: one fulvic acid-like component, one tryptophan-like component, and three humic-like components. Using SEC-ICP-MS, arsenite, arsenate, arsenobetaine, and DOM-bound As were eluted and detected according to different molecular weights, and the co-elution of 56 Fe and DOM-bound As under the same elution condition indicated the complexation between DOM and As through Fe ions. Furthermore, obvious quenching effects of fluorescent DOM components in the presence of As(III) were observed, suggesting that strong complexation or adsorption occurred between As(III) and different DOM components. Among five DOM components identified by PARAFAC, the humic-like components played a key role in forming complexes with As(III), thus leading to the changes of As species in natural water. The results exhibited considerable implications for the role of DOM components on the mobilization and speciation of As, which could be applied to the As removal in natural water and act as an indicator to evaluate the capacity of As complexation or adsorption in the environment.

During the design process of Reactor Coolant Pump (RCP) test circuit, a flow conditioner is considered to be necessary in view of the fact that the RCP test circuit has a large flow volume and a relatively limited space, and it must meet the need of stabilizing the flow as quickly as possible. This article bases on the demands of the function of the flow conditioner in reactor coolant pump test circuit, utilizes the CFD analysis software to carry out 3-dimensioning modeling of several flow conditioners, and simulates the characteristic of the fluid in circuit under different flow conditioners. Through the analysis of the pressure distribution in the downstream of the flow conditioner, different stabilizing effects are obtained, and the final structure of the flow conditioner is determined considering the real demand of the test circuit.