title: Spatio-temporal variation of heavy metals in fresh water after dam construction: a case study of the Manwan Reservoir, Lancang River.
abstract: This study investigated temporal heavy metal characteristics over the past 20 years and the spatial variation of heavy metal characteristics at the Manwan Reservoir tail, center, and head in the Lancang River, Yunnan Province, China. The following heavy metals were selected for analysis: Hg, Cd, Pb, Cu, Zn, As, Cr, Fe, and Mn. Multivariate statistical methods, including principal component analysis (PCA) and the Pearson correlation matrix were used to distinguish the main pollution factors and sources before and after dam construction. The results indicate that the average annual values of heavy metals were far lower than the recommended values of the surface water quality standards in China with the exception of Hg. The concentration of metals showed considerable variation by season, where higher levels of metals generally occurred in high flow periods. The results from PCA show that three significant components were extracted, explaining 76.25% of the total variance. The ANOVA results indicate that Pb, Fe, Mn, and Cr had significant spatial variation (P < 0.05) at the reservoir tail, center and head. The enrichment factor (EF) used to compare the accumulation effect of heavy metals indicated that there was no enrichment (EF < 1) of heavy metals with the exception of Mn, which showed minor enrichment (1 < EF < 3) between the reservoir center and head. The spatiotemporal variation and the accumulation effects of water heavy metals were not distinct due to the construction of the Manwan Reservoir.
authors.affiliation: School of Environment, State Key Laboratory of Water Environment Simulation, Beijing Normal University, 19 Xinjiekouwai Street, Beijing, 100875, People's Republic of China.
authors.forename: Qinghe
authors.initials: Q
authors.lastname: Zhao
authors.forename: Shiliang
authors.initials: S
authors.lastname: Liu
authors.forename: Li
authors.initials: L
authors.lastname: Deng
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Yang
authors.forename: Shikui
authors.initials: S
authors.lastname: Dong
authors.forename: Cong
authors.initials: C
authors.lastname: Wang
authors.forename: Zhaoling
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D002681:China; D004784:Environmental Monitoring; D019216:Metals, Heavy / Q000032:analysis*; D025341:Principal Component Analysis; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data
chemical_list: D019216:Metals, Heavy; D014874:Water Pollutants, Chemical