全氟烷基乙醇 (FTOHs) 和全氟烷基乙烯 (FTOs) 土-气分配过程机理及其低温时土-气分配行为特性研究

Highly fluorinated compounds are special in that they have a much smaller van der Waals interaction energy per molecular contact area than nonfluorinated compounds. So their soil-air partitioning behaviors are different from those of nonfluorinated compounds. Meanwhile, the relationship between soil-air partitioning coefficient and temperature are different between low (subzero) temperatures and high (above zero) temperatures. Flurotelomer alcohols (FTOHs) and flurotelomer olefins (FTOs) are two main kinds of semi-volatile highly fluorinated compounds, which are usually detected in the soil and air samples, whereas, it is very important to study the mechanism for the soil-air partitioning behavior of flurotelomer alcohols (FTOHs) and flurotelomer olefins (FTOs) and their special partitioning behavior at low temperature. In this study, investigations on levels of FTOH and FTOs in soil and air samples are conducted in Liaoning Province, Jilin Province, Heilongjiang Province at first and then, with the results of ambient measurements, the laboratory experiments are carried out to determine the soil-air partition coefficient (KSA) of flurotelomers with novel equipment called fugacity meter. Different flurotelomers (FTOH or FTOs), types of soil and ambient temperatures are chosen in the laboratory experiments to finger out the potential impact factors for the KSA of FTOH or FTOs. As a result, a quantitative relationship between the thermodynamical parameter of KSA and physical-chemical parameters of the chemicals, physical-chemical parameters of the soil and temperatures (-30~30 оC) is set up. The objective of this study is to gain a mechanistic understanding of the processes determining the partition behavior of FTOH and FTOs between soil and air and in particular to decipher how they are influenced by low temperatures. The results of this study enable scientists to better understand the distribution of FTOH and FTOs in natural environment; to forecast the fate of these chemicals in soil and air environment; and to assess the ecological risk. Furthermore, this study will provide scientific evidences for the "cold condensation" of flurotelomers (as well as other fluorochemicals, for example, perfluorocarboxylate) in the cold regions of the global.

高氟化合物单位分子接触面积上的范德华相互作用能明显低于非氟化合物，因此该类化合物在土壤-空气间的分配行为必将区别于非氟化合物，而低温时 (温度小于零度) 半挥发性有机污染物的土-气分配规律更有别于高温时 (温度大于零度) 的情况，所以研究含氟调聚物土-气分配过程的机理及其低温时分配行为的特性具有重要意义。本项目以中国东北地区为拟研究区域，以FTOHs和FTOs 在环境中土-气分配状况指导实验室模拟实验，建立该类化合物土-气分配系数 (KSA) 与理化性质参数、土壤性质参数和环境温度 (-30~30 оC) 定量关系模型，探讨含氟调聚物土-气分配行为的机理及低温时的特殊分配机制，为定量了解、模拟和预测该地区含氟调聚物的迁移、归趋以及生态风险提供理论基础，同时为该类化合物及其他含氟化合物 (如全氟烷基羧酸，FTOH和FTOs的降解产物) 在全球低温地区潜在的"冷浓缩"提供科学依据。

采用固相逸度计的方法测定了3种全氟烷基乙醇（FTOHs）和2种全氟烷基乙烯（FTOs），在一种稻田土上-30℃~0℃温度范围内7个温度点的土-气分配系数（KSA），结果显示：全氟己基乙醇（6:2 FTOH）的log KSA在-1.31~2.13，全氟辛基乙醇（8:2FTOH）的log KSA在-0.41~3.86，全氟癸基乙醇（10:2FTOH）的log KSA在0.86~4.43，全氟癸基乙烯（10:2 FTO）的log KSA在-0.82~2.87，全氟十二烷基乙烯（12:2FTO）的log KSA在-0.61~3.10，数据跨5.25个数量级。与其他半挥发性有机污染物相比，FTOHs和FTOs的KSA较低，这可能是高氟化合物单位分子接触面积上的范德华相互作用能低于非氟化合物的原因。.温度依附性实验中，所研究3种FTOHs和2种FTOs，-30℃~0℃的log KSA与绝对温度倒数均呈良好的线性关系，斜率分别在6.60~7.41和7.64~8.06之间。说明FTOHs和FTOs的log KSA随温度降低而显著增大。与文献相比，它们的温度依附性仅低于部分有机氯农药（OCs），高于多氯联苯（PCBs）和多环芳烃（PAHs）。FTOHs同系物间的比较结果显示，随分子量增大，其log KSA的温度依附性增强。.碳原子个数对土-配系数影响实验结果表明，FTOHs每增加一个-CF2-CF2-基团，其log KSA增加1.25±0.25，FTOs每增加一个-CF2-CF2-基团，其log KSA增加0.30±0.14。log KSA与log KOA呈线性关系，相关系数平方为0.887，但拟合直线的斜率为2.43，明显偏离于1，所以对于FTOHs这类化合物，在土壤上的分配与在辛醇上的不同，Karickhoff方程不能用于预测该类物质的土-气分配系数。.本研究填补了低温下全氟烷基化合物土-气分配数据的空白，进而加深了人们对该类化合物在低温下土壤中环境行为的理解。