Antagonistic Effects, Sources, and Distribution of Selenium and Toxic Metals in Fish from Selenium-Rich and High Cadmium Areas, Dashan Region, China.

The Gongxin River is one of the main rivers in the Dashan Region of Anhui Province in China, which is a Se-rich and high-Cd area, but no research has focused on the concentration, source, antagonism, and health risks of Se and TMs in fish. In this study, 120 fish samples (14 species), 24 sediment samples, and 24 water samples were collected to investigate the antagonistic effects, sources, and health risks of TMs and Se in fish from a typical selenium-rich and high cadmium region. Zn and Se in fish from the Gongxin River were higher than in the background, which might be attributed to the different feeding habits of different fish species. The apparent antagonism between Se and Cu, Pb, and Cd was explored, and the results showed that 30%, 75%, and 100% of the Se/Cu, Se/Pb, and Se/Cd ratios were greater than one, indicating that Cu, Pb, and Cd in fish might be combined with or detoxicated by Se. The source analysis of the elements showed that the geological background was the source of TMs and Se in fish samples. The amounts of Se and TMs were all within China's acceptable level guidelines, signifying no harm to citizens from eating fish.

CO2 Gasification Kinetics and Structural Characteristics of Tri-High Coal Char Prepared at Elevated Temperature.

The combined effects of surface area, pore structure, degree of graphitization, and number of carbon functional groups on the gasification kinetics of tri-high coal char prepared at an elevated temperature were studied by a thermogravimetric analyzer and various characterization methods [scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) theory, X-ray diffraction (XRD), Raman spectroscopy, and Fourier transfer infrared spectroscopy]. In the kinetic analysis, the CO2 gasification of high-ash coal was not adequately described by the random pore model because ash influenced the char structure during pyrolysis and gasification. Meanwhile, the SEM and BET results indicated the promotion of micropore formation and mesopore expansion of the coal char during pyrolysis. The XRD, Raman, and FTIR results evidenced a significant increase of large aromatic groups during the pyrolysis process, attributable to the cracking of aliphatic groups and the polycondensation of the cracking residues. Overall, the porous structure and aromatic groups of coal char developed during the pyrolysis process improved the CO2 gasification kinetics of the tri-high coal char.

Structure Characterization and CO2 Gasification Kinetics of Tri-High Coal-Chars Derived from High-Temperature Pyrolysis.

The pore structures and chemical composition features of two kinds of tri-high coal and their char samples prepared at a 750 °C temperature were analyzed. The results showed that the pyrolysis process has a great influence on the pore structure and the chemical composition of the char, and the influence is highly related to the coal ranks. The gasification kinetics of the two chars in pure CO2 atmosphere was also studied. The results indicated that the classical random pore model (RPM) cannot be used to explain the gasification kinetics throughout the char gasification. A modified RPM, considering the inhibitory effect of ash on the gasification kinetics, was adopted to estimate the kinetics, and the kinetic constants and the corresponding activation energies were calculated. It was observed that it was necessary to include the effect of ash on the variations of char structures during the char gasification to get an accurate description of reaction rate versus carbon conversion throughout the gasification of the tri-high coal chars.