长江河口水库沉积物磷形态、吸附和释放特性

为了对长江河口青草沙水库沉积物磷形态分布、磷吸附特性和磷释放特性进行分析,2011年4月~2012年1月对沉积物进行实地调查分析.磷形态分析结果表明沉积物总磷含量范围为535.07~910.9 mg·kg-1,以无机磷为主,有机磷含量相对较低.无机磷主要以钙结合态的磷存在,钙结合态磷占总磷的75.57%.磷吸附特性结果表明沉积物磷的等温吸附特征符合修正的Langmuir模型,沉积物磷的最大吸附量为9.78~39.84 mg·kg-1,沉积物-水界面平衡浓度EPC0(equilibrium phosphorus concentration)范围为0.024~0.12 mg·L-1,均高于上覆水体中相应的磷含量,因此,沉积物有向上覆水体释放磷的趋势.磷的释放特性结果表明沉积物最大释放量为11.03 mg·kg-1,在6 h左右达到最大值.沉积物磷释放量来自沉积物的铁/锰结合态的磷、钙结合态磷和有机磷,其中,铁/锰结合态磷和沉积物释放量呈相关性(P0.01).总体上,青草沙水库沉积物呈现释放状态,影响水库水体磷含量.

Phosphorus Fractions, Sorption Characteristics and Its Release in the Sediments of Yangtze Estuary Reservoir, China

To analyze the sediment phosphorus (P) fractions and sorption characteristics and P release from sediment of reservoir in Yangtze estuary, the sediment was investigated during April, 2011 to January, 2012. Results of chemical fractionation analysis showed that total P (TP) content in sediment ranged from 535.07 to 910.9 mg·kg^-1, inorganic P (IP) was a dominant component of TP and the content of organic P (OP) was low. IP presented in the form of P bounded to calcium (HCl-P) and dominated 75.57% of TP. The batch experiments showed that sediments had the maximum P adsorption capacity from 9.78 to 39.84 mg·kg^-1, sorption data fitted the modified Langmuir isotherm model. However, EPC₀ (equilibrium phosphorus concentration) in all sampling sites was higher than the soluble-reactive P concentration in water column, which was from 0.024-0.12 mg·L^-1. Accordingly, the sediments from those sampling sites would release phosphorus into the overlying water as a P release source. The maximum released amount from sediment was 11.03 mg·kg^-1 about 6 hours. Correlation between P released amount and NaOH-P was found (P<0.01), and sediment P release would mainly originate from the NaOH-P, OP and HCl-P fraction. It is evident that the inherent phosphorus present in sediments would be a major threat to the water quality in Yangtze River estuary reservoir.