Vertical Distribution Characteristics of Nutrients and Heavy Metals in Sediments of Lake Hongze
洪泽湖沉积物中营养盐和重金属的垂向分布特征研究

In order to understand the vertical distribution characteristics of nutrients and heavy metals in sediments of Lake Hongze, three core sediment samples at 3 sites (one near the Huaihe River inlet of Lake Hongze, one at the western part of the lake and one at the lake center) were collected in June of 2008. By measurement of total nitrogen (TN), total phosphorus (TP) and heavy metals (Cu, Zn, Pb, Cd, Fe, Al, Cr, Hg, Mn, As) and by analyzing of their vertical characteristics, investigation revealed the nutrient evolution processes and pollution history. Sediment near Huaihe river mouth was more polluted by the Huaihe River watershed. The nutrients TN, TP and organic matter (OM) concentrations in this core sample were 390.8-643.7,428.6-538.6,5194.3-9164.9 mg·kg-1 respectively. Zn, Cd, Al, Fe and Mn in the sediment in this area were affected by human activities less than other heavy metals. Western Lake sediment was affected by the Huaihe River, inlet river and human activities in cities along western lake shoreline. TN, TP and OM concentrations in this core sample were 633.4-2677.3, 480.0-1115.9, 7140.8-47849.7 mg·kg-1 respectively. The pollution extents of TN, OM and heavy metals in sediment were exacerbated since the late of 1970s, but the situation was improved since the 1990s. As and Cr in the sediments were influenced by human activities more than other heavy metals. Main pollution source in sediment at the lake center were detritus from the lake watershed. TN, TP and OM concentrations in this core sample were 904.7-1585.4, 526.3-750.1, 10635.6-19020.6 mg·kg-1 respectively. The correlations among nutrients and heavy metals in sediment are significant, and their vertical distribution patterns were similar. The concentrations of nutrients and heavy metals increased from bottom to surface. Nutrients and heavy metal pollution in sediment had the same vertical distribution characteristics which coincided with the lake watershed economic development stage. The sediment in Lake Hongze can be described by the Turbidity Flood Model.