Dam construction reshapes sedimentary pollutant distribution along the Yangtze river by regulating sediment composition. (1st January 2023)

• Record Type: Journal Article
• Authors: Guo, Jiaxun; Xie, Yu; Guan, Aomei; Qi, Weixiao; Cao, Xiaofeng; Peng, Jianfeng; Liu, Huijuan; Wu, Xinghua; Li, Chong; Wang, Dianchang; Qu, Jiuhui
• Is Part Of: Environmental pollution. Volume 316(2023)part 2
• Publication Date: 2023-01-01
• Subjects: Nutrients -- Heavy metals -- Polycyclic aromatic hydrocarbons (PAHs) -- Fluvial sediments -- Spatial trajectory -- Yangtze river; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2022.120659
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Dam construction has far-reaching impacts on pollutant accumulation and the pollutant-induced quality of aquatic environments. Nonetheless, its large-scale effects on pollutant distribution in sediments, which greatly contribute to the environmental impacts of coexisting pollutants, remain poorly understood. We collected sediments from the Yangtze River during the dry and normal seasons (with 'normal' defined in terms of precipitation level), and examined how dam construction alters the spatial trajectories of both inorganic and organic pollutants in the sediments. Sediment composition exhibited linear variation from the upper to the lower reaches, with clay and silt particles dominating the sediment in the Three Gorges Reservoir and sand particles dominating in the middle–lower reaches. Accordingly, upstream of the Three Gorges Dam (TGD), sedimentary carbon, nitrogen, phosphorus, heavy metal, polycyclic aromatic hydrocarbons (PAHs), and oxygenated PAHs (OPAHs) contents increased toward the TGD owing to its regulation of the spatial variation in sediment particle size. The TGD caused upstream sedimentary accumulation of pollutants to be higher nearer to the TGD than in the upper reaches by 17%–129% for carbon, nitrogen, and phosphorus, 7%–51% for heavy metals, 30% for PAHs, and 140% for OPAHs. Pollutant content was sharply lower below the TGD, by 0.58–11.15 times for carbon, nitrogen, and phosphorus, 0.1–2.6 times for heavy metals, 1.7 times for PAHs, and 5.6 times for OPAHs. Upstream of the TGD, levels of NH4 + -N, the main form of N in the interstitial water of the Yangtze River, increased lineary toward the TGD, whereas those of NO3 − -N and NO2 − -N decreased. Sedimentary organic matter source contributions were consistent along the Yangtze River, being on an average 46% for C3 plants and 28% for soil organic substances, further confirming the dam's regulatory effect on pollutants. These findings provide a foundation for future assessments of the environmental impact of dam-induced river fragmentation and hydrological alterations, and for developing advanced watershed pollutant management strategies. Graphical abstract: Image 1 Highlights: Sediment composition exhibited a linear variation in the Yangtze River. Up(down)stream of dam, pollutant level increased (decreased) to the dam. The levels of NH4 + -N and NOx − -N increased and decreased lineary to the TGD. Sedimentary organic matter derived from C3 plants and soil organic matter.