关键词: 黄河, 重金属, 发育毒性, 神经递质, 运动行为

Abstract:

The Yellow River, the second-longest river in China, has been a subject of widespread concern regarding its ecological health. With the implementation of the “Yellow River Protection Law” of the People’s Republic of China, it has become crucial to assess the characteristics of heavy metal concentrations in key sections of the river and evaluate their ecological risks. This study focuses on the Sanmenxia section of the Yellow River, which connects the Sanmenxia and Xiaolangdi Reservoirs. This study aims to investigate the concentration of 13 heavy metals in the river water, along with their potential ecological risks to aquatic organisms. Using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), this research analyzed the concentration of 13 heavy metals in the river water, i.e., Pb, Cd, Cr, Cu, Zn, As, Ni, Co, Mn, Fe, Al, V, and Ag. The results indicated that Pb concentrations exceeded the Class II standard thresholds for surface water at some sampling sites, while concentrations of Cd, Cr, Cu, Zn, and As were below the Class II thresholds. To further understand the ecological risks posed by these heavy metals, we designed three concentrations of compound exposure gradients for a mixture of six representative heavy metals (Cd, Cr, Cu, Zn, Pb, Ni). These gradients were used to evaluate the effects of heavy metal pollution on the development of zebrafish embryos (Danio rerio), as well as the content of neurotransmitters and precursor substances in zebrafish larvae, and their motor behavior. The study specifically aimed to determine the toxicity of heavy metal mixtures at environment-related concentrations and their potential impact on aquatic life. The experimental results revealed that exposure to environmentally relevant and high-concentration combined exposures significantly reduced the hatching rate of zebrafish embryos by 15.8% and 31.3%, respectively, while malformation rates increased by 140% and 256%. These findings suggest that even environment-related concentrations of heavy metal mixtures can have adverse effects on the development of aquatic organisms. In addition, heart rates at 84 hours post-fertilization increased by 16.3%, 15.9%, and 21.7% in the combined exposure groups, highlighting potential physiological disruptions caused by the heavy metal exposure. Further analysis of the neurotoxic effects of heavy metal exposure revealed significant increases in the concentrations of neurotransmitters and their precursor substances in the zebrafish. These included gamma-aminobutyric acid, glutamate, phenylalanine, tyrosine, and tryptophan. In the high-concentration exposure group, these neurotransmitters and their precursor substances increased by 8.4%, 23.3%, 77.1%, 111%, and 104%, respectively, compared to the control group. Furthermore, zebrafish larvae exhibited an increase in motor activity under both continuous light and light-dark stimulation, suggesting that the heavy metal exposure led to excessive excitation of the nervous system. This neurotoxic response may have significant implications for the health of aquatic organisms exposed to mixed heavy metal contamination in natural environments. The findings of this study provide a comprehensive analysis of the heavy metal concentrations in the water of the Sanmenxia section of the Yellow River. The study also highlights the potential negative impacts of low-concentration heavy metal mixtures on aquatic organisms, particularly during critical stages of development. Even though the concentrations of most heavy metals in the water were below regulatory limits, the results suggest that these pollutants can still pose a significant ecological risk, particularly in the form of developmental toxicity, neurotoxicity, and physiological disruptions in aquatic species. This study contributes to the growing body of knowledge on the toxicity of heavy metal mixtures and expands our understanding of how low-concentration pollution may still result in harmful effects on aquatic life. It underscores the need for a more comprehensive approach to environmental monitoring, particularly in regions where pollution may not exceed regulatory thresholds but still presents significant risks to the ecosystem. The results of this study are important for the management and protection of water quality in the Yellow River, as well as other river systems that may experience similar levels of pollution. The findings also have broader implications for environmental policy and pollution control. Despite the fact that most of the heavy metals analyzed in this study were within acceptable limits, the negative effects observed in zebrafish embryos and larvae suggest that regulatory standards may not fully account for the cumulative or synergistic effects of multiple pollutants. Thus, it is critical to reconsider how environmental standards are set, particularly for complex mixtures of pollutants that may have unforeseen ecological consequences. This research advocates for a more nuanced approach to environmental regulation that takes into account the cumulative effects of pollutants, even at low concentrations, in order to protect aquatic ecosystems and biodiversity. Furthermore, the study provides important insights for the management and mitigation of heavy metal pollution in the Yellow River Basin. Although the pollution levels in the water currently comply with regulatory standards, this study highlights the potential risks of low concentrations of heavy metals. It is important to continue monitoring these pollutants and to implement strategies for reducing their input into the river. These strategies could include improving waste treatment processes, controlling agricultural runoff, and promoting sustainable industrial practices that reduce the release of heavy metals into the environment. In future research, it would be valuable to investigate the long-term effects of low-concentration heavy metal mixtures on different aquatic species and ecosystems. Additionally, studies should explore the synergistic effects of various pollutants, as this could provide a more comprehensive understanding of the environmental risks associated with complex contamination scenarios. Future research should also focus on the development of more effective pollution control technologies and strategies that can mitigate the risks posed by heavy metal pollution in the Yellow River and other major river systems in China. In conclusion, this study provides significant insights into the ecological risks posed by heavy metal pollution in the Yellow River, particularly in the Sanmenxia section. It emphasizes the need for ongoing monitoring and management of low-concentration heavy metal pollution, as even these levels can have significant negative effects on aquatic organisms. The findings of this study are crucial for informing future environmental policies and pollution control efforts, and they underscore the importance of developing more comprehensive and effective strategies for protecting the health of aquatic ecosystems and biodiversity.

Key words: Yellow River, heavy metals, developmental toxicity, neurotransmitters, locomotor behavior