京杭大运河苏南城市段表层沉积物铜、锌吸附特征及理论环境安全吸附容量

Characterization and theoretical environmental capacity of copper and zinc sorption in surface sediments from urban sections of the Grand Canal of China

应用等温吸附法研究京杭大运河苏南三城市段(常州、苏州和无锡)表层沉积物对Cu和Zn的吸附行为,并结合国家地表水环境质量标准(GB3838—2002),估算运河城市段表层沉积物对Cu和Zn的理论环境安全吸附容量(QⅢ)。结果表明:大运河表层沉积物的Cu和Zn等温吸附符合Langmuir模型;表层沉积物Cu最大吸附量(Cu-Qmax)为5.20～9.03 mg·g-1,Zn最大吸附量(Zn-Qmax)为2.40～5.07 mg·g-1;最大吸附量与沉积物的性质密切相关,但与总有机碳质量分数无关。根据Langmuir拟合方程估算,在我国地表水环境质量标准三类水标准阈值时,Cu的理论环境安全吸附容量为沉积物总Cu量的19倍以上,而Zn则为2～6倍。因此,Zn对三城市段大运河沉积物的环境风险要高于Cu。

The isothermal sorption approach was applied to characterize the sorption behavior of Cu and Zn in surface sediments from urban sections（Changzhou,Suzhou and Wuxi） of the Grand Canal,China.Using the class III thresholds of the National Surface Water Environmental Quality Standards of China（GB3838-2002）,we calculated the potential environmental capacity（QIII） of Cu and Zn by the Langmuir model.The QIII was regarded as an indicator to evaluate potential risk of Cu and Zn to surface sediments in urban sections of the Grand Canal.Results indicated that sorption isotherms of Cu and Zn in surface sediments were well fitted by the Langmuir model and the calculated maximum sorption capacities（MSCs） by the model were 5.20-9.03 mg·g-1 for Cu and 2.40-5.07 mg·g-1 for Zn.The sediments had a larger sorption capacity of Cu than that of Zn.Sediment properties,such as pH,electric conductivity（EC）,clay mineral content,specific surface area（SSA）,and average particle size（APS）,showed significant correlations with MSCs of Cu and Zn whereas organic matter（TOC） was not significantly related to MSCs.The calculation of QIII on the basis of Cu and Zn thresholds for the potable water source pointed out that Cu-QIII was over 19 times of the existing total Cu contents in sediments while Zn-QIII was only 2-6 times of the existing total Zn contents.Our study suggests that Zn might impose higher environmental risk to the Grand Canal than Cu.