东洞庭湖弱透水层沉积物磷形态及吸附特性

Speciation and Adsorption Characteristics of Phosphorus on Sediments of Aquitard in East Dongting Lake

湖底弱透水层是湖水-地下水交互的重要场所,其对磷的吸附和释放深刻影响着沉积物与湖水和地下水之间的磷交换。近年来,洞庭湖水体和沉积物中的磷含量呈上升趋势,湖水呈现出轻度富营养化现象,因此以东洞庭湖为研究区,分别采集坝内(J1)、外(J2)钻孔弱透水层沉积物样品,通过连续提取法对沉积物中磷的形态进行分析,并以J2钻孔沉积物为例,通过沉积物对磷的吸附动力学和热力学试验探究弱透水层沉积物对磷的吸附特性。结果表明:J1、J2钻孔沉积物中总磷含量分别为584.59~879 mg/kg、642.94~1482.76 mg/kg,并均以钙结合态磷和闭蓄态磷为主,其含量占总磷含量的百分比均为70%左右;J2钻孔沉积物中平衡吸附磷浓度(EPC0)的范围在0.056~0.252 mg/L之间,通过对弱透水层沉积物中EPC0值与湖水、地下水中溶解性反应磷(SRP)浓度的比较,可以初步判断当地下水补给湖水时,弱透水层沉积物表现为“汇”,而当湖水下渗时,弱透水层沉积物作为“源”,从而对湖水和地下水水质产生一定的影响。

Lake bottom aquitard is an important place for the interaction between lake water and groundwater.Its adsorption and release of phosphorus has a profound impact on the phosphorus exchange between sediments and various water bodies.The content of phosphorus in Dongting Lake water increases with time.With East Dongting Lake as the study area?the sediment samples from boreholes inside(JI)and outside(J2)of the dam were collected.The forms of phosphorus in the sediments were analyzed by continuous extraction method,and the adsorption characteristics of phosphorus explored by adsorption kinetics and thermodynamics experiments using sediment samples of J2.The results show that the contents of total phosphorus in the sediments of JI and J2 boreholes are 584.59〜879 mg/kg and 642.94〜1482.76 mg/kg,respectively,and dominated by authigenic Ca-P(Ca-P)and detrital P(Detr-P)(about 70%).The equilibrium adsorbed phosphorus concentration(EPC0)of sediments of J2 is between 0.047〜0.168 mg/L and 0.056〜0.252 mg/L,respectively.Through Comparing EPC0 with the soluble phosphate(SRP)of lake water and groundwater,it can be concluded that when groundwater recharges the lake water,the sediments of aquitard layer act as"sink",while when the lake water infiltrates,the sediments act as“source”,which has an impact on the water quality of the lake.