【作者】 杨志群；

【导师】 高宏；

【作者基本信息】 兰州大学 ， 环境科学， 2010， 硕士

【摘要】 水环境底泥沉积物是有机污染物迁移、转化的重要介质,与人类生产生活密切相关,在环境污染物归趋、生物可利用性中起着重要的作用。而环境污染物在水环境中的行为和归宿,受到降解、吸附、迁移等过程的影响,这些过程是相互联系和彼此制约的。随着科学的进步和环境污染日趋严重,有关持久性有机污染物环境行为方面的研究已日益成为热点研究内容之一。首批12种受控制的POPs中有9种为有机氯农药,其中六六六、滴滴涕是最常见的两种。兰州地区具有大量使用这两种农药的历史,黄河兰州段有机氯农药主要来自农业的使用和生产农药的企业的排放,以废水、雨水的形式进入黄河水环境。水环境沉积物对有机氯农药的吸附、解吸是它在沉积物-水环境中归宿的主要因素之一。因此,研究有机氯农药的黄河水环境吸附、解吸行为特性,对于了解有机氯农药的区域环境过程、进行生态风险评价及水污染治理具有重要的意义。本论文选择典型持久性有机氯农药六六六(1,2,3,4,5,6-hexachlorocyclohex-ane,HCH)和滴滴涕(2,2-bis(4-Chlorophenyl)-1,1,1-trichloroethane, DDT)作为吸附质,采用黄河兰州段相对清洁的表层沉积物作为吸附剂,进行了吸附解吸模拟实验研究,并同时对有机氯农药在腐殖酸和蒙脱石上的吸附特性也进行了比较研究。对表层沉积物、腐殖酸和蒙脱石吸附HCH和DDT的动力学实验数据进行了拟合；测定了其吸附速率：利用Henry、Fruendlich和Langmuir吸附等温模型描述各个固相介质对农药的吸附热力学数据,探讨表层沉积物、腐殖酸和蒙脱石吸附HCH和DDT的热力学特征和影响因素,比较研究各种吸附剂对HCH和DDT吸附特性的异同及其吸附机理。研究结果表明：(1)表层沉积物、腐殖酸和蒙脱石吸附HCH和DDT的动力学过程均可分为快反应和慢反应两个阶段；各吸附剂对吸附质的吸附量随着时间的延长而增加；各吸附剂对HCH和DDT吸附达到平衡的时间为12～24小时之间；腐殖酸和蒙脱石对HCH和DDT的吸附速率较快；在农药的吸附解吸过程中,吸附解吸作用实际上是同时发生的,各吸附剂对农药的吸附速率常数大于解吸速率常数,解吸存在滞后性,造成农药在环境中长距离迁移。(2)利用Henry、Freundlich和Langmuir吸附模型对各吸附剂在所研究条件下吸附HCH和DDT的吸附热力学数据进行拟合,结果表明：在所研究的浓度范围内,Henry、Freundlich和Langmuir吸附模型均可较好的拟合HCH和DDT在表面沉积物上吸附的热力学数据,这体现了其吸附行为的复杂性；由相关系数可知,Henry线性模型对HCH和DDT在腐殖酸、蒙脱石上吸附的热力学数据拟合较好。各吸附剂对HCH和DDT的吸附结果的比较研究显示,各吸附剂对DDT的吸附量大于对HCH的吸附量；各吸附剂对HCH的吸附能力为腐殖酸>蒙脱石>表层沉积物；对DDT的吸附能力为,蒙脱石>腐殖酸>表层沉积物,说明沉积物中腐殖酸和粘土矿物含量越多,沉积物的吸附能力更强。(3)通过正交设计法,讨论吸附质浓度、吸附剂浓度、温度、pH值等对HCH和DDT的吸附行为影响实验中发现,各吸附剂对吸附质HCH的单位吸附量并无显著性差异；表面沉积物吸附DDT的影响因素中,吸附质和吸附剂含量有显著性差异,吸附质与单位吸附量正相关,吸附剂与单位吸附量呈负相关；腐殖酸和蒙脱石吸附DDT的影响因素中,吸附剂含量存在显著性差异。其他因素如温度、酸度、沉积物粒度、有机质含量也有一定的影响。更多还原

【Abstract】 The sediment in aquatic environment is not only the main media for organic pollutants to transport and transform, but also playing an important role in environmental fate and bioavailability, which also closely related to the human life. In addition, the pollutants sorption, degradation and transport on the sediment will have an important effects on their behavior and fate in aquatic environment, furthermore, these processes are connected and influenced to each other.With the scientific advances and growing environmental pollution, persistent organic pollutants become more hot spot involving in their environmental bebavior research. Organochlorine pesticides (OCPs) are mostly used as insecticides and mainly include HCH and DDT, in addition, nine organochlorine pesticides are listed in the prefered controlled POPs. Lanzhou actually has a long history for using these two OCPs and the OCPs of Yellow River in Lanzhou mainly come from the waste water of agricultural pesticide use and the emissions of enterprises production to rain. The behavior and fate of OCPs in the aquatic environment are influenced by degradation, sorption, desorption and transport processes. Therefore, to study the sorption and desorption behaviors has a significant theoretical worth for understanding their environmental fate, assessing the ecological risk and water pollution control in the study area.In this shesis, we chooseγ-HCH and p,p’-DDT as the representative of OCPs to study the characteristics for sorption and desorption of typical persistent organic pollutants by using the cleaner sediments of up Yellow River in Lanzhou as the sorbent.Meanwhile, different characteristics of sorption and desorption on the humic acid and montmorillonite were also investigated. The proper model was used to fit the sorption dynamics data ofγ-HCH and p,p’-DDT on the sorbents and the sorption velocities were also determined. In addition, Henry、Fruendlich and Langmuir model were used to fit thermodynamic date, and tried to figure out the differences and similarities of the sorption behaviors on different sorbent. The study results are summarized as follows:(1) All kinetic sorption behaviors ofγ-HCH and p,p’-DDT on sediments, the humic acids and montmorillonites exhibited distinguished two stages:fast and slow. The sorption amount ofγ-HCH and p,p’-DDT were increased with increasing time and the contact time of 12-14h was sufficient for sediments, humic acids and montmorillonites to achieve equilibrium. In addition, the sorption velocities ofγ-HCH and p,p’-DDT were faster on humic acids and montmorillonites than those on sediments. The sorption and desorption processes happened simultaneously at the procedure of sorption of pesticides, and the sorption rates were higher than that of desorption, which indicated that the desorption was delayed and the pollutants can transported over a long distance in aquatic environment.(2) The study results also showed that Henry、Fruendlich and Langmuirthe model were all fitted for describing the sorption behavior ofγ-HCH and p,p’-DDT on the sediments in the study concentrations range, which exhibited the complicacy of sorption behavior of these two compounds. Furthermore, Henry model was better for sorption ofγ-HCH and p,p’-DDT on humic acids and montmorillonites by comparing the different correlation coefficient. In addition, from the study results we deduced that the sorption capability of p,p’-DDT onto sorbents was stronger than that ofγ-HCH. and the sorption capability on different sorbents from large to small as follows:forγ-HCH, humic acids> montmorillonites>surface sediments; for p,p’-DDT, montmorillonites> humic acids>surface sediments, which indicated the more humic acid and clay mineral content in sediment would result in the stronger sorption capacity of sediment.(3) In this paper, the effects of some influence factors on sorption behaviors including initial concentration of sorbate and sorbent, water temperature, pH and so on were also invastigated by using orthogonal experimental design. The study results showed that different sorbents did not have the significant effect on the sorption amounts per unit of y-HCH. Furthermore, the initial concentration of sorbate and sorbent were obviously very to the sorption of p,p’-DDT on surface sediments, which exhibited a positive correlation in sorbates and a negative correlation in sorbents. Moreover, the sorption of p,p’-DDT on humic acids and montmorillonites were related with the concentration of sorbent, and other effects of temperature, pH, granularity of sediments and content of organic matter were observed in this paper.更多还原