At present, the methods widely applied to assess ecological risk of heavy metals are essentially single-point estimates in which exposure and toxicity data cannot be fully used and probabilities of adverse biological ...At present, the methods widely applied to assess ecological risk of heavy metals are essentially single-point estimates in which exposure and toxicity data cannot be fully used and probabilities of adverse biological effects cannot be achieved. In this study, based on investigation of concentrations of six heavy metals(As, Hg, Pb, Cd, Cu, and Zn) in the surface seawater and sediment near the outlet of a zinc factory, located in Huludao City, Liaoning Province, China, a tiered approach consisting of several probabilistic options was used to refi ne ecological risk assessment for the individuals. A mixture of various heavy metals was detected in the surface seawater, and potential ecological risk index(PERI) was adopted to assess the potential ecological risk of heavy metals in the surface sediment. The results from all levels of aquatic ecological risk assessment in the tiered framework, ranging from comparison of single effects and exposure values to the use of distribution-based Hazard Quotient obtained through Monte Carlo simulation, are consistent with each other. Briefl y, aquatic Zn and Cu posed a clear ecological risk, while Cd, Pb, Hg, and As in the water column posed potential risk. As expected, combined ecological risk of heavy metal mixture in the surface seawater was proved signifi cantly higher than the risk caused by any individual heavy metal, calculated using the concept of total equivalent concentration. According to PERI, the severity of pollution by the six heavy metals in the surface sediment decreased in the following sequence: Cd>Hg>As>Pb>Cu>Zn, and the total heavy metals in the sediment posed a very high risk to the marine environment. This study provides a useful mathematical framework for ecological risk assessment of heavy metals.展开更多
In high-voltage direct current cable systems,the factory joint of cross-linked polyethylene(XLPE)-insulated cables presents significant electrical breakdown risk.The charge accumulation mechanism at the XLPE-XLPE inte...In high-voltage direct current cable systems,the factory joint of cross-linked polyethylene(XLPE)-insulated cables presents significant electrical breakdown risk.The charge accumulation mechanism at the XLPE-XLPE interface involves the accumulation of opposite charges on both sides of the interface,thereby complicating the comprehension of the interfacial charging phenomenon.This study investigates the fundamental mechanisms of charge accumulation and the associated homo-junction effect in homo-bilayer XLPE(H-XLPE).Space charge analysis,model calculations based on Maxwell's equations,and thermal stimulation depolarisation current(TSDC)measurements were performed.Space charge results show that the homo-junctioninduced charge accumulation causes greater electric field distortion,leading to lower breakdown strength of H-XLPE compared to single-layer XLPE.Model calculations indicate that the density of opposite charges on the interface is attributed to the local gradient of reciprocal conductivity in the H-XLPE interface region.TSDC measurements on XLPE and H-XLPE enabled extraction of trap parameters and analysis of the charge transport process.The findings provide experimental evidence and theoretical clue for elucidating the role of the interface area on the charge accumulation that affects reliability and stability of submarine cable systems.展开更多
基金Supported by the Science and Technology Project of North China Sea Branch of State Oceanic Administration(No.2014B02)
文摘At present, the methods widely applied to assess ecological risk of heavy metals are essentially single-point estimates in which exposure and toxicity data cannot be fully used and probabilities of adverse biological effects cannot be achieved. In this study, based on investigation of concentrations of six heavy metals(As, Hg, Pb, Cd, Cu, and Zn) in the surface seawater and sediment near the outlet of a zinc factory, located in Huludao City, Liaoning Province, China, a tiered approach consisting of several probabilistic options was used to refi ne ecological risk assessment for the individuals. A mixture of various heavy metals was detected in the surface seawater, and potential ecological risk index(PERI) was adopted to assess the potential ecological risk of heavy metals in the surface sediment. The results from all levels of aquatic ecological risk assessment in the tiered framework, ranging from comparison of single effects and exposure values to the use of distribution-based Hazard Quotient obtained through Monte Carlo simulation, are consistent with each other. Briefl y, aquatic Zn and Cu posed a clear ecological risk, while Cd, Pb, Hg, and As in the water column posed potential risk. As expected, combined ecological risk of heavy metal mixture in the surface seawater was proved signifi cantly higher than the risk caused by any individual heavy metal, calculated using the concept of total equivalent concentration. According to PERI, the severity of pollution by the six heavy metals in the surface sediment decreased in the following sequence: Cd>Hg>As>Pb>Cu>Zn, and the total heavy metals in the sediment posed a very high risk to the marine environment. This study provides a useful mathematical framework for ecological risk assessment of heavy metals.
基金supported by Program of Beijing Huairou Laboratory(Grant ZD2022003A).
文摘In high-voltage direct current cable systems,the factory joint of cross-linked polyethylene(XLPE)-insulated cables presents significant electrical breakdown risk.The charge accumulation mechanism at the XLPE-XLPE interface involves the accumulation of opposite charges on both sides of the interface,thereby complicating the comprehension of the interfacial charging phenomenon.This study investigates the fundamental mechanisms of charge accumulation and the associated homo-junction effect in homo-bilayer XLPE(H-XLPE).Space charge analysis,model calculations based on Maxwell's equations,and thermal stimulation depolarisation current(TSDC)measurements were performed.Space charge results show that the homo-junctioninduced charge accumulation causes greater electric field distortion,leading to lower breakdown strength of H-XLPE compared to single-layer XLPE.Model calculations indicate that the density of opposite charges on the interface is attributed to the local gradient of reciprocal conductivity in the H-XLPE interface region.TSDC measurements on XLPE and H-XLPE enabled extraction of trap parameters and analysis of the charge transport process.The findings provide experimental evidence and theoretical clue for elucidating the role of the interface area on the charge accumulation that affects reliability and stability of submarine cable systems.
