Characterizing dissolved organic matter in Taihu Lake with PARAFAC and SOM method

The three-dimensional fluorescence spectrum has a significant amount of information than the single-stage scanning fluorescence spectrum. At the same time, the parallel factor (PARAFAC) analysis and neural network method can help explore the fluorescence characteristics further, thus could be used to analyse multiple sets of three-dimensional matrix data. In this study, the PARAFAC analysis and the self-organizing mapping (SOM) neural network method are firstly introduced comprehensively. They are then adopted to extract information of the three-dimensional fluorescence spectrum data set for fluorescence characteristics analysis of dissolved organic matter (DOM) in Taihu Lake water. Forty water samples with DOM species were taken from different seasons with the fluorescence information obtained through the three-dimensional fluorescence spectrum analysis, PARAFAC analysis and SOM analysis. The PARAFAC analysis results indicated that the main fluorescence components of dissolved organic matter in Taihu Lake water were aromatic proteins, fulvic acids, and dissolved microorganisms. While the SOM analysis results exhibited that the fluorescence characteristics of the dissolved organics in Taihu Lake varied seasonally. Therefore, the combined method of the three-dimensional fluorescence spectrum analysis, PARAFAC and SOM analysis can provide important information for the characterization of the fluorescence properties of dissolved organic matter in surface water bodies.

LA-ICP-MS U-Pb dating and geochemical characterization of oil inclusion-bearing calcite cements: Constraints on primary oil migration in lacustrine mudstone source rocks

To date, few isotope age constraints on primary oil migration have been reported. Here we present U-Pb dating and characterization of two fracture-filling, oil inclusion-bearing calcite veins hosted in the Paleocene siliciclastic mudstone source rocks in Subei Basin, China. Deposition age of the mudstone formation was estimated to be ca. 60.2−58.0 Ma. The first vein consists of two major phases: a microcrystalline-granular (MG) calcite phase, and a blocky calcite phase, each showing distinctive petrographic features, rare earth element patterns, and carbon and oxygen isotope compositions. The early MG phase resulted from local mobilization of host carbonates, likely associated with disequilibrium compaction over-pressuring or tectonic extension, whereas the late-filling blocky calcite phase was derived from overpressured oil-bearing fluids with enhanced fluid-rock interactions. Vein texture and fluorescence characteristics reveal at least two oil expulsion events, the former represented by multiple bitumen veinlets postdating the MG calcite generation, and the latter marked by blue-fluorescing primary oil inclusions synchronous with the blocky calcite cementation. The MG calcite yields a laser ablation−inductively coupled plasma−mass spectrometry U-Pb age of 55.6 ± 1.4 Ma, constraining the earliest timing of the early oil migration event. The blocky calcite gives a younger U-Pb age of 47.8 ± 2.3 Ma, analytically indistinguishable from the U-Pb age of 46.5 ± 1.7 Ma yielded by the second calcite vein. These two ages define the time of the late oil migration event, agreeing well with the age estimate of 49.7−45.2 Ma inferred from fluid-inclusion homogenization temperature and published burial models. Thermodynamic modeling shows that the oil inclusions were trapped at ∼27.0−40.9 MPa, exceeding corresponding hydrostatic pressures (23.1−26.7 MPa), confirming mild-moderate overpressure created by oil generation-expulsion. This integrated study combining carbonate U-Pb dating and fluid-inclusion characterization provides a new approach for reconstructing pressure-temperature-composition-time points in petroleum systems.

Fluorescence Characteristics of Highly-Pure Nanoparticles Embedded in Dye Complexes for Random Laser Design

In this work, highly-pure titanium dioxide nanoparticles produced by dc magnetron sputtering technique were embedded in organometallic complex solutions such as Baq2 or Znq2 to form random gain media. The structural characteristics of the TiO2 nanoparticles were determined to confirm their high structural purity. The spectroscopic characteristics, mainly photoluminescence and fluorescence, of the complex solutions containing the nanoparticles were determined and studied. These media were compared to two of the most common laser dyes (Rhodamine b and Rhodamine 6G) to determine the feasibility to use them to produce random laser.

Fluorescence Characteristics of Coalbed Methane Produced Water and Its Influence on Freshwater Bacteria in the South Qinshui Basin, China

Production of coalbed methane (CBM) resources commonly requires using hydraulic fracturing and chemical production well additives. Concern exists for the existence of chemical compounds in CBM produced water, due to the risk of environmental receptor contamination. In this study, parallel factor method analysis (PARAFAC), fluorescence index, and the fluorescence area integral methods were used to analyse the properties of CBM produced water sampled from Shizhuang Block (one of the most active CBM-producing regions in the Qinshui Basin). A culture experiment was designed to determine the effect of discharged CBM produced water on microorganisms in freshwater. Water quality analysis shows the hydrochemistry of most water samples as Na-HCO3 type produced water of CBM appears as a generally weak alkaline (pH 8.69 ± 0.185) with high salinity, high alkalinity, and a high chemical oxygen demand (COD) value. Three individual components were identified by using parallel factor method analysis as humic-like components (C1), fulvic-like components (C2), and amino acid-like substances (C3). The fluorescence characteristic index comprehensively explains that the fluorescent substances in CBM produced water has the characteristics of a low degree of humification and a high recent self-generating source. The region integration results of characteristic peaks show that tyrosine-like and tryptophan-like materials account for more than 67% of fluorescent substances in CBM produced water. The addition of produced water from coalbed methane promotes the growth of freshwater bacteria, and this process is accompanied by the decrease of the proportion of fulvic acid, humic acid, and the increase of the proportion of soluble microbial metabolites. This paper proposes a convenient method for organic matter identification of CBM produced water and provides some theoretical support and reference for the improvement of CBM water treatment and utilization.

Computational Chemistry of Compounds with Donor-Acceptor Interactions

<p>Compounds with donor-acceptor interactions find important applications in catalysis, C-H activation, phosphorus activation, selective oxidation and cyclization. Moreover, they are potential candidates for use in the synthesis of materials, polymers and light-harvesting systems. The efficient use of a chemical entity is possible when we know its structural and bonding properties. This computational study is intended for the same by studying in detail the structure and bonding properties of donor-acceptor complexes of heavier main-group metals with cyclophane ligands and some heterobimetallic complexes. Additionally, we explored the fluorescence characteristics of benzanthrone dyes. The first part (i.e. main group metal complexes) involves the exploration of structural features and thermal properties through DFT optimization and then calculating the change in enthalpy of formation for all the possibilities under consideration. For this purpose we selected the last three elements from each of Groups 13, 14 and 15 to explore their different coordination modes with two cyclophane ligands; [2.2.2]paracyclophane and deltaphane. We opted for chlorides of each metal to allow them to coordinate from outside the phenyl rings of the cyclophane cavity and from the top of the cavity. To see the coordination of the metals with the inner core of the selected cyclophanes, we put metal cations in the centre of the cavity and optimized. Subsequently, the bonding properties of these inclusion complexes have been analysed in detail on the basis of Morokuma-Ziegler energy decomposition analysis. Secondly, we investigated the structure and bonding properties of some indium-zinc heterobimetallic compounds through geometry optimization, NBO analysis and quantum theory of atoms in molecules (QTAIM) analysis--also known as Bader's analysis. We propose that the heterobimetallic reactant involves donor-acceptor bond that cleaves as a result of the addition of mesityl azide. The newly formed complex has In-N and Zn-N bonds. In the final part benzanthrone dyes containing intramolecular donor-acceptor interactions, (and hence, undergoing intramolecular charge transfer) were subject to the computational investigation of the mechanism of fluorescence taking place in them. Electronic excitations and the structure of first excited state in each case has been discussed thoroughly based on the time-dependent density functional theory. To check for the non-radiative loss of energy, we also performed calculations for the vertical excitations of the triplet states of all the molecules under study. To get a deeper insight into the intramolecular charge transfer, we performed NTO analysis that gives us information based on different colours in regions of charge accumulation and charge depletion.</p>

Computational Chemistry of Compounds with Donor-Acceptor Interactions

<p>Compounds with donor-acceptor interactions find important applications in catalysis, C-H activation, phosphorus activation, selective oxidation and cyclization. Moreover, they are potential candidates for use in the synthesis of materials, polymers and light-harvesting systems. The efficient use of a chemical entity is possible when we know its structural and bonding properties. This computational study is intended for the same by studying in detail the structure and bonding properties of donor-acceptor complexes of heavier main-group metals with cyclophane ligands and some heterobimetallic complexes. Additionally, we explored the fluorescence characteristics of benzanthrone dyes. The first part (i.e. main group metal complexes) involves the exploration of structural features and thermal properties through DFT optimization and then calculating the change in enthalpy of formation for all the possibilities under consideration. For this purpose we selected the last three elements from each of Groups 13, 14 and 15 to explore their different coordination modes with two cyclophane ligands; [2.2.2]paracyclophane and deltaphane. We opted for chlorides of each metal to allow them to coordinate from outside the phenyl rings of the cyclophane cavity and from the top of the cavity. To see the coordination of the metals with the inner core of the selected cyclophanes, we put metal cations in the centre of the cavity and optimized. Subsequently, the bonding properties of these inclusion complexes have been analysed in detail on the basis of Morokuma-Ziegler energy decomposition analysis. Secondly, we investigated the structure and bonding properties of some indium-zinc heterobimetallic compounds through geometry optimization, NBO analysis and quantum theory of atoms in molecules (QTAIM) analysis--also known as Bader's analysis. We propose that the heterobimetallic reactant involves donor-acceptor bond that cleaves as a result of the addition of mesityl azide. The newly formed complex has In-N and Zn-N bonds. In the final part benzanthrone dyes containing intramolecular donor-acceptor interactions, (and hence, undergoing intramolecular charge transfer) were subject to the computational investigation of the mechanism of fluorescence taking place in them. Electronic excitations and the structure of first excited state in each case has been discussed thoroughly based on the time-dependent density functional theory. To check for the non-radiative loss of energy, we also performed calculations for the vertical excitations of the triplet states of all the molecules under study. To get a deeper insight into the intramolecular charge transfer, we performed NTO analysis that gives us information based on different colours in regions of charge accumulation and charge depletion.</p>

Response of Chlorophyll Fluorescence Characteristics and Dissolved Organic Matter for Marine Diatom Skeletonema dohrnii under Stress from Penicillin and Zn2+

Skeletonema dohrnii is a good model diatom for studying environmental stress and has promising applications and prospects in various fields. Antibiotics and heavy metals are commonly exceeded in the nearshore marine habitats. In this work, we investigated the effects of an antibiotic (penicillin, 2 µg/L) and a heavy metal ion (Zn2+, 10 µmol/L) stress on marine diatom S. dohrnii, mainly using excitation-emission matrices (EEMs) fluorescence methods and OJIP test. Results indicated that algal cells grown with the antibiotic showed higher biomass, specific growth rate, doubling time, chlorophyll a, and chlorophyll fluorescence variables. Moreover, excess zinc had negative effects on S. dohrnii. We found that zinc not only inhibited the relative photosynthetic electron transfer efficiency but also reduced the Chl a content, which ultimately affected algal growth and organic matter production. In addition, the combined effect of penicillin and Zn2+ further affected the physiological state of S. dohrnii. The dissolved organic matter (DOM) characteristics of the four cultures were also different, including fluorescence indices (fluorescence index, biological index, β/α, and humification index) and fluorescence peaks (peaks A, C, M and T). In brief, characterization of chlorophyll fluorescence characteristics and DOM-related variables are important for understanding the effects of environmental stress on microalgae.