Abstract
The distribution and fractionation of nine heavy metals (Cr, Co, Ni, Cu, Cd, Zn, V, Pb and As) in the sediments of Lake Chaohu,
a shallow eutrophic lake, were investigated using the BCR sequential extraction procedure. The level of pollution attributed to
these nine heavy metals was evaluated employing the potential ecological risk index (RI) and geoaccumulation index (Igeo). Metal
concentrations in sediments ranged from 65.00~104.00 for Cr, 14.50~21.70 for Co, 28.50~50.90 for Ni, 25.40~51.30 for Cu,
0.30~1.27 for Cd, 96.80~436.00 for Zn, 89.00~126.00 for V, 37.80~102.00 for Pb and 9.63~16.61 for As. Cr, As, Ni, V and Cu
were present mainly in the residual fraction, with proportions of 73.75%, 73.54%, 67.80%, 73.24% and 59.46%, respectively,
while Co, Pb, Zn and Cd were associated with the non-residual fractions (soluble, reducible and oxidizable fractions) dominantly,
with total non-residual fraction proportions of 56.54%, 70.97%, 65.55% and 91.6%, respectively. The results of correlations
analysis between different heavy metals showed that the heavy metals studied have different origins and distributions, which
were divided into five categories: (1) Cu, Zn and Ni, (2) Co and V, (3) Pb and Cd, (4) Cr and (5) As. The rank order of potential
ecological risk indices for these heavy metals was Cd> As> Pb> Co> Cu> Ni> Zn> V> Cr. Cd had high potential ecological risk
and contributed the most to the potential ecological risk index as compared to the other heavy metals. The Igeo values suggested
“unpolluted” levels for Cr, V, As and Ni (mean Igeo< 0), “unpolluted to moderately polluted” levels for Co, Cu, Zn and Pb (0<
mean Igeo <1), and “moderately polluted” levels for Cd (1< mean Igeo <2).