[Distribution and pollution characteristics of nutrients and heavy metals in sediments of Hedi Reservoir].

Core sediments were collected from the riverine, transition and lacustrine zones of Hedi Reservoir in southern China to investigate the spatial distributions of nutrients and heavy metals and assess the potential ecological risk of heavy metals. The total nitrogen (TN) contents of the sediments at three sampling sites are between 2.314-2.427 mg x g(-1), while total phosphorus (TP) contents range from 0.591 mg x g(-1) to 0.760 mg x g(-1), TN contents of the surface sediments increase from the riverine zone to the lacustrine zone, but the TP content in the transition zone is higher than that in the other two sites (riverine zone and lacustrine zone). The mean contents of heavy metals are: 31.094, 46.85, 75.615, 385.739, 0.624 and 0.171 mg x kg(-1) respectively, except Cr, the contents of heavy metals in sediment of lacustrine zone are higher than the sediment of transition zone. In all core sediments, the contents of nutrients and heavy metals decrease from the surface to the bottom of core sediments. Inorganic phosphorus (IP) is the dominant fraction of phosphorus in the sediment and the NaOH-P is the main forms of inorganic phosphorus. The potential ecological risk assessed by using of the highest environmental background values before industrialization as the reference indicates that each single heavy metal only causes slightly pollution, but two heavy metals (Cd and Hg) cause heavy pollution based on the soil environmental background values of Guangdong province. In spite of the slight difference between two kinds of risk assessment, all demonstrated that Cd and Hg resulted in more serious pollution than the other metals and these two metals contributed most to the RI values.