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区域环境与生态

Effects of pH and salinity on phosphorus sorption and desorption in the surface sediments of the mainstream of the Haihe River

基金项目：天津市科技支撑计划重点项目(No.09ZCGYSF00400);水利部公益性行业科研专项子课题(No.200801135);国家水体污染控制与治理重大专项(No.2009ZX07209-001);国家自然科学基金(No.50479034)

孙淑娟
1. 天津市城市生态环境修复与污染防治重点实验室环境污染过程与基准教育部重点实验室环境科学与工程学院, 南开大学, 天津 300071; 2. 山东农业大学资源与环境学院, 泰安 271018

摘要：采用等温吸附解吸方法,研究大范围pH(2～12)和盐度(2‰～32‰)对海河表层沉积物吸附解吸磷的影响,并与分级提取技术得到的海河沉积物中磷形态分布相结合,进一步探讨磷在沉积物-水界面的迁移转化机理.结果表明,钙磷(Ca-P)和难溶态磷(Re-P)为海河表层沉积物磷的主要形态.沉积物对磷的吸附符合修正的Langmuir吸附等温线(R²>0.90).海河沉积物(8个典型断面)对磷的理论吸附量较大,说明在今后上覆水含磷浓度较高的情况下,沉积物仍能吸附大量的磷污染物.在海河水磷污染较轻的情况下,沉积物中的磷将释放并导致水体发生富营养化.pH对磷的吸附影响呈"U"型,且随着pH增大,磷的解吸量也增大,这是由于OH^-交换能力的增强所致;盐度增大,沉积物对磷的吸附总体呈下降趋势,但在10‰～15‰之间有反复,并且随着盐度增大,磷的解吸量也下降.

Abstract：Phosphorus speciation analysis using sequential extracting methods was combined with phosphorus sorption and desorption experiments to understand the effects of pH and salinity on phosphorus sorption and desorption in the surface sediments of the Haihe River.The results showed that Ca-P and Re-P were the two main fractions of P in the surface sediment of the mainstream of the Haihe River.A modified Langmuir isotherm fitted the phosphorus sorption well(R² > 0.90),and the sorption capacity of sediments from eight locations of Haihe River mainstream were high,which indicated that the Haihe River mainstream sediments will be a source of phosphorus in the future.The pH effect on phosphorus sorption from sediments was U-shaped,so phosphorus desorption from sediments increased with pH,due to displacement of PO₄^3- adsorbed on sediment surfaces by OH^-.Phosphorus sorption decreased with increasing salinity,and phosphorus desorption decreased with increasing salinity,resulting from stronger anion competition.

Key words：Haihe River mainstream surface sediment phosphorus speciation sorption and desorption pH salinity