| Plateau Lakes in Yunnan Province are the most important natural resources for its economic development. In this study,74surface sediment samples were collected from three typical plateau Lakes-Dianchi, Fuxian, and Lugu Lakes. BCR sequential extraction procedures were used to reveal the spatial distribution of total concentration and speciation of heavy metals Cu, Cr, Pb in surface sediments. Physicochemical properties such as pH, particle size distribution, and element analysis of surface sediments were analyzed. The relationships among physicochemical properties, total concentration, and speciation were revealed by Pearson correlation analysis, principal components analysis, and hierarchical cluster analysis. The pollution characteristics and ecological risk of heavy metals were evaluated by, the index of geoaccumulation(Igeo), pollution load index(PLI), the Potential Ecological Risk Index(RI), and the sediment quality guidelines (SQGs). Hopefully the results can be used as guidelines to assess heavy metals pollution of surface sediments of Plateau Lakes, and to restoration of ecological systems of Plateau Lakes. The results were showed as follows:(1) The mean values of pH of surface sediments in Dianchi, Fuxian and Lugu Lakes were7.32,7.72and7.54indicating a weak alkaline nature. The particle size distribution indicated that the fine particles including clay and silt were the main component of Dianchi Lake, Fuxian Lake and Lugu Lake. The average percentage of C, N, S, and H in surface sediments of Dianchi Lake was8.93%,0.73%,0.99%and1.92%. respectively. Whereas the average percentage of C, N, S, and H in surface sediments of Fuxian Lake was3.38%,0.2%,0.19%and1.05%. For Lugu Lake the average content of C, N, S, and H in surface sediments was5.59%,0.33%,0.21%and1.32%, respectively.(2) The speciation of Cu in surface sediments of Dianchi Lake decreased as follows: the reducible fraction F2> the residual fraction F4> the oxidizable fraction F3> the acid-soluble fraction F1.The speciation of Cr in surface sediments of Dianchi Lake decreased as follows:the reducible fraction F2> the residual fraction F4> the oxidizable fraction F3> the acid-soluble fraction F1. The speciation of Pb in surface sediments of Dianchi Lake decreased as follows:the reducible fraction F2> the residual fraction F4> the oxidizable fraction F3> the acid-soluble fraction F1. The heavy metals associated with different fractions in surface sediments of Fuxian Lake follow the order, Cu:the residual fraction F4> the reducible fraction F2> the oxidizable fraction F3> the acid-soluble fraction F1; Cr:the residual fraction F4> the reducible fraction F2> the oxidizable fraction F3> the acid-soluble fraction F1; Pb: the reducible fraction F2> the residual fraction F4> the oxidizable fraction F3> the acid-soluble fraction Fl. The fraction of Cu in surface sediments of Lugu Lake was in the descending order of the reducible fraction F2> the residual fraction F4> the oxidizable fraction F3> the acid-soluble fraction F1.The fraction of Cr in surface sediments of Lugu Lake was in the descending order of the reducible fraction F2> the residual fraction F4> the oxidizable fraction F3> the acid-soluble fraction F1. The fraction of Pb in surface sediments of Lugu Lake was in the descending order of the reducible fraction F2> the residual fraction F4> the oxidizable fraction F3> the acid-soluble fraction Fl.(3) The bioavailable fraction of heavy metals in the surface sediments of Dianchi Lake, based on the mean value, was in the following order:Cu (84.41%)> Pb (74.29%)> Cr (82.05%). For Fuxian Lake, the bioavailable fraction of heavy metals was in the following order:Pb (61.68%)> Cr (54.04%)> Cu (51.85%). While the bioavailable fraction of heavy metals in surface sediments of Lugu Lake followed a decreasing order as Pb (76.98%)> Cu (68.65%)> Cr (60.43%).(4) The trace elements Cu, Cr, and Pb in surface sediments of Dianchi Lake were significantly and positively correlated with each other. Therefore, Cu, Cr, and Pb may come from similar sources. However, heavy metals Cu and Cr in surface sediments of Fuxian Lake were significantly and positively correlated with each other, then Cu, and Cr may have common sources. Pb had no significant correlation with Cu and Cr, this indicated that Pb had a different origin. Heavy metals Cu, Cr and Pb in surface sediments of Lugu Lake had no significant correlation with each other, this meant heavy metals Cu, Cr and Pb may have different origin.(5) The entire lake average Igeo of Cu, Cr and Pb in surface sediments of Dianchi Lake was0.79,-1.50and0.99. The Igeo class of Cu and Pb was unpolluted to moderately polluted, Cr was practically unpolluted. While the average Igeo of Cu, Cr and Pb in surface sediments of Fuxian Lake was-1.80,-2.85and-1.15respectively. Cu, Cr and Pb was practically unpolluted. The average Igeo of Cu, Cr and Pb in surface sediments of Lugu Lake was-0.24,-1.75and-2.31respectively. The Igeo class of Cu, Cr and Pb was practically unpolluted. The average Pollution Load Index of Dianchi Lake, Fuxian Lake and Lugu Lake was2.33,0.54and0.73, respectively, PLI was in the following order:Dianchi Lake> Lugu Lake> Fuxian Lake. The calculated mean Potential Ecological Risk Index of Dianchi Lake, Fuxian Lake and Lugu Lake was83.44,13.73and19.95, all RI were less than150indicated heavy metals Cu, Cr, and Pb were in low potential ecological risk. the mean Potential Ecological Risk Index followed the order:Dianchi Lake> Lugu Lake> Fuxian Lake.(6) The heavy metals Cu, Cr, and Pb concentration was compared with three sets sediment quality guidelines (SQGs) such as TEL and PEL, LEL and SEL, ERL and ERM. The results showed that Cu and Pb posed adverse biological effects on sediment-dwelling organisms in surface sediments of Dianchi Lake.The data from the SQGs suggested that Cu and Pb were found to have adverse biological effects on sediment-dwelling organisms of surface sediments of Fuxian Lake. While, Cu and Cr were observed to be associated with adverse biological effects for surface sediments of Lugu Lake. |
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