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Understanding variations in contaminant concentrations and exploring their driving factors are essential for pollution control and water environment improvement. The Huaihe River Basin, as an important region in the eastern region of China, has attracted much attention to its water environment issues in recent years. Therefore, an in-depth analysis of spatiotemporal patterns of water quality parameters was carried out on the Huaihe River–Hongze Lake system, for the period 1998–2018, using the Mann–Kendall test (MKT) and wavelet transforms (WTs). Significant decrease trends of ammonia nitrogen (AN) and chemical oxygen demand (COD) concentrations were detected in the Huaihe River (HR) before 2008 using the MKT. High concentration in the contaminant load was a result of the effect of increased construction and decreased forest on increasing input of pollutants during this period. The results of the WT showed how factors (e.g., streamflow and water temperature), except land use, affect the variations in AN and COD concentrations. The comparison of spatiotemporal patterns of AN and COD between the HR and Hongze Lake (HL) showed their differences in contaminant transport regimes. The contaminants were rapidly transported downstream along the HR with high streamflow during the wet season, while these in the HL were less responsive due to the long residence time of the water body. In addition, rebounds of contaminant concentrations occurred many times at the confluence between the HR and the HL due to strong river–lake interactions, especially in the flood season. These results have implications for future water environment management in the Huaihe River Basin and in similar settings worldwide. [ABSTRACT FROM AUTHOR]

The current distribution of the grounding electrode in a high-voltage direct current (HVDC) transmission system affects the state of power equipment in its vicinity, which depends on the soil resistivity and shape of the grounding electrode. In this paper, current distribution in the vicinity of an ±800 kV grounding electrode is investigated by simulation and experiments. Firstly, the model to calculate the current distribution with two typical frozen soils is set up, and simulation models and experimental platforms are established; meanwhile, the finite element method (FEM) is used to calculate the current and potential dispersion of linear, cross-shaped, and ring-shaped grounding electrodes in the simulation models. After obtaining the lab current data from the simulation, an innovative method based on a "drainage wire" with a Hall sensor is proposed to measure the current in an experimental setup. The results show that current and potential distribution characteristics are related to the shape of the grounding electrode and soil resistivity. Meanwhile, the current measurement scheme can measure the current in soil with a lower error. This article concludes that these two typical models can reduce the complexity of frozen soil analysis, and the measurement scheme can accurately monitor the current to reduce the damage to the surrounding power equipment. [ABSTRACT FROM AUTHOR]

Nuclear technology benefits humans, but it also produces nuclear radiation that harms human health and the environment. Based on the modified Andreasen and Andersen particle packing model for achieving a densely compacted cementitious matrix, a new magnetite ultra-high-performance concrete (MUHPC) was designed using magnetite fine aggregate as a substitute for river sands with 0%, 20%, 40%, 60%, 80%, and 100% replacement ratios. The comprehensive properties of the developed MUHPC were tested and evaluated. These properties were fluidity, static and dynamic compressive strengths, high-temperature performance, antiradiation behaviors, hydration products, and micropore structures. Experimental results indicate that the developed MUHPC has high work performance and static and dynamic mechanical properties. The gamma ray shielding performance of MUHPC substantially improves with increased magnetite fine aggregate. Corresponding with 100% magnetite fine aggregate substitution, the linear attenuation coefficient of MUHPC is enhanced by 56.8% compared with that of ordinary concrete. Magnetite addition does not change the type of cement hydration products but improves the micropore structures of MUHPC and effectively reduces its total porosity and average pore diameter, thereby contributing to its mechanical and radiation shielding properties. The compressive strength and linear attenuation coefficient of the MUHPC can reach 150 MPa and 0.2 cm−1, respectively. In addition, the MUHPC also exhibits superior mechanical and radiation shielding performance at elevated temperatures (<400 °C). Finally, high strength and antiradiation performance support the use of MUHPC in radiation protection materials in the future. [ABSTRACT FROM AUTHOR]