上覆水性质对滇池沉积物释放滴滴涕的影响

Effect on the release of DDTs from the sediments of Dianchi Lake by the properties of the overlying water

以滇池沉积物为基质,制备p,p＇-DDE污染沉积物,通过模拟悬浮态释放试验,研究了上覆水性质对滇池沉积物释放滴滴涕（DDT）的影响。结果表明：在25℃悬浮状态下,沉积物中的p,p＇-DDE可逐步释放出来,表现出初阶段释放速度较快、而后变缓的特点;水体温度与沉积物释放p,p＇-DDE呈正相关,水温40℃时的平衡释放量是10℃时的5.2倍;在p H=3～11的范围内,偏碱性的水体有利于p,p＇-DDE从沉积相向水相中迁移,水体p H=11的平衡释放量是p H=3的2.3倍;高水平的离子强度对沉积物中p,p＇-DDE的释放有抑制作用,1 mol/L Ca Cl2溶液的平衡释放量是0.01 mol/L时的44.6%;水体中的溶解性有机质对沉积物释放p,p＇-DDE有显著的＂增溶效应＂,溶解性有机质质量分数为1%时的平衡释放量是0.1%的8.5倍。研究表明,在评价湖泊水环境中DDT的生态风险时,上覆水的理化性质是一个需要考虑的因素,水温、p H值、离子强度和溶解性有机质等因素可通过提供吸热反应的动力、改变沉积物有机质形态、增加水中胶体物质的形成等途径影响沉积物中DDT向水相的迁移行为。

This paper is inclined to present the results of our study of the effects of the properties of overlying water on the release of DDTs from the sediments of Dianchi Lake,Kunming,Yunnan. As is known,Dianchi Lake is one of the typical heavily polluted lakes by DDTs release both of endocrine disrupting chemicals（ EDCs） and the long-lasting persistent organic pollutants（ POPs）. While our previous research indicated that p,p＇- DDE had been the dominant chemical compound in accordance with the results of our previous exploration and investigation,what we would like to focus our attention in the given investigation is to the releasing tendency of DDTs from the sediments resulted by the water diversion project of Niulan River both in the water and the sludge sediments. Therefore,the entire study focus of the present paper is to be put on the basis of the sediment matrix of the Lake,including p,p＇- DDE,and the other main influential factors,such as the water temperature,the p H value,the ironic concentration and the content rate of the dissolved organic matters through simulating the suspension state in combination with the field sampling and home simulation. The results of our simulation research and on-spot investigation and observation demonstrate that the said p,p＇- DDE release tends to be done gradually from the sediments as the result of being promptly accumulated during the later slow-going process under the comprehensive impacts of the temperature of water and the release of the other compounds in a positive correlative manner,at the balanced temperature at about 40℃,perhaps in a releasing amount of 5. 2 times at a temperature of10 ℃ higher than as usual on the average. Needless to say,higher p H is favorable for the release of the compounded pollutants in a range of p H value of 3- 11,with the release amount of balance at p H = 11 being 2. 3 times higher than at p H = 3. On the other hand,highly concentrated ionic strength tends to reveal somewhat inhibitive or negative impact on the release of p,p＇- DDE,for the balanced releasing amount of the 1 mol / L Ca Cl2 may account for just 44. 6%as much as of 0. 01 mol / L Ca Cl2. On the other hand,the presence of the dissolved organic matters in the water is inclined to reveal a significant＂strengthened dissolution effect＂on the release of p,p＇- DDE,which may account for the liability to increase the releasing amount of DOM in the water from 0. 1% to 1%,that is,8. 5 times as much as its original amount. The results of our study also imply that the physicochemical properties of the overlying water can be regarded as an influential factor to be taken into account when we estimate the eco-risks of DDT in the lake environment,along with the other factors which tend to affect the migration behaviors of DDTs by way of supporting the power of endothermic reactions,and transformation process of the organic matters into inorganic ones in the formation of sediments,thus bringing about the increased formation of the colloidal materials.