Multivariate analysis of heavy metal and nutrient concentrations in sediments of Taihu Lake, China

Taihu Lake is one of the largest freshwater lakes in China. The Lake is ver y shallow with a mean depth of 1.9 m and an area of 2428 km(2). Nutrient co ncentrations (Org-C, Tot-N and Tot-P) and heavy metal concentrations (Ag, A s, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sr, Zn, etc.) in the lake's surface sediment s were sampled at 13 locations. This was done to determine if industrialize d areas along the lake's coastline were impacting the nutrient and heavy me tal distribution of the lake's surface sediments. Principal Component Analy sis (PCA) was used to assess the degree of contamination and spatial distri bution of heavy metals and nutrients in different areas of Taihu Lake. A distinctive spatial distribution of heavy metals and nutrients was observ ed. Sediments from a large embayment of Taihu Lake called Lake Wulihu had s ignificantly higher nutrient concentrations (Org-C, 2.05-3.83%; Tot-N, 0.28 -0.54%; Tot-P, 0.10-0.33%) than any other area of Taihu Lake. These high nu trient levels were associated with the input of untreated domestic sewage f rom the large (circa one million people) City of Wuxi, which discharges its effluents into the Liangxi River. As a result, Lake Wulihu is the most eut rophic area of Taihu Lake. The nearby Meiliang Bay suffered from the worst heavy metal contamination in Taihu Lake (e.g. As, 64.0; Ag, 4.2; Cd, 0.93; Co, 14.2; Cr, 155.0; Cu, 144.0; Hg, 0.25; Ni, 79.8; Pb, 143.0 and Zn, 471 m g kg(-1)). These high heavy metal concentrations were ascribed to the disch arge of untreated and partially treated industrial waste water from Changzh ou and Wujin via the Zhihugang River. Surface sediment samples from the eas t basin of Taihu Lake were characterized by high Org-C (1.0-2.3%) and Tot-N (0.18-0.37%) and low Tot-P (0.048-0.056%) concentrations. It is likely tha t macrophytes removal accounts for a major reduction of phosphorus in the s ediments of the east basin of Taihu Lake.