西辽河不同粒级沉积物的氨氮吸附-解吸特征

为估算辽河吸附态氨氮人海通量,采用平衡吸附-解吸法研究了西辽河不同粒级沉积物对氨氮的吸附-解吸特征.结果表明:不同粒级沉积物对氨氮的吸附-解吸特征均符合Langmuir和Freundlich吸附-解吸等温式；黏粒级和粉粒级沉积物的氨氮饱和吸附量较大,分别为3 643.82和2 693.71 mg/kg,相当于粗砂的8.04和5.94倍；西辽河冲泻质泥沙黏粒和粉粒所携载的吸附态氨氮的人海通量分别为170.10和164.52 mg/kg.占沉积物氨氮吸附总量的14.99％；黏粒级和粉粒级沉积物的氨氮解吸比例较小,分别为30.66％和42.04％,人海后可分别为上覆水提供氨氮52.15和69.16 mg/kg;黏粒级和粉粒级沉积物所吸附的氨氮是氮素循环的重要组成部分；黏粒和粉粒级沉积物的腐殖质含量远远高于粗沙,在其所形成的团聚体结构中存在的孔隙填充方式——氨氮吸附是导致黏粒和粉粒级沉积物饱和吸附量较大、解吸比例较低的根本原因.

Sorption and Desorption of Ammonium Nitrogen on Sediments of Different Grain Sizes in Western Liao River

In order to estimate the flux of ammonia adsorbed by the Liao River and entering into the sea,sorption and desorption characteristics of ammonium nitrogen on sediments with different grain sizes in the Western Liao River were investigated by batch experiments of equilibrium sorption-desorption.The results indicated that sorption and desorption of sediments with different grain sizes conformed to the Freundlich and Langmuir isotherms.The sorption capacities of clay and silt were 3643.82 and 2693.71 mg/kg respectively,which were 8.04 and 5.94 times higher than those of the coarse sand.Furthermore,the sorption state ammonium nitrogen carried by clay and silt from the Western Liao River to the sea was 170.10 and 164.52 per kilogram suspended sediments,respectively,which represented 14.99% of the total ammonium nitrogen absorbed by the sediment.The desorption ratios of clay or silt were low,reaching 30.66% and 42.04% respectively.Clay and silt provided the overlying water with 52.15 and 69.16 mg ammonium nitrogen per kilogram sediments,respectively.Furthermore,the sorption state ammonium nitrogen carried by clay and silt was a vital part of the sediment nitrogen cycling.The humus content in clay or silt was much higher than that in the coarse sand,because there was a micro-hole filling sorption mechanism in the aggregate structure.The higher the clay or silt sediment sorption capacity,the lower the desorption ratio.