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全氟烷基酸(perfluoroalkyl acids,PFAAs)是由完全氟化的烷基链和酸性官能团组成的化合物,因其兼具疏水性和疏油性等化学特性,常作为工业助剂和表面活性剂而应用于工业和消费品生产领域,如金属电镀、半导体、家具和烹饪器具等[1]。在2009年,PFAAs被列入斯德哥尔摩公约的新型持久性有机污染物。PFAAs易在生物体内聚集,能够长距离迁移、沉积和附着,一旦进入人体后很难通过代谢降解方式排出体外,可对肝脏、内分泌、神经系统和免疫性能等方面产生毒性危害[2]。PFAAs家族成员PFOA和 PFOS因其稳定性,应用最为广泛,且作为全氟化合物前体的最终降解物质,在自然环境中检测频率最高[3]。随着氟化工产业的快速发展,中国逐渐成为氟化产品生产和使用大国。秦交友等[4]的研究表明,我国东南地区主要河流表层水体中PFAAs质量浓度为0.90~231.52 ng·L−1,部分河段PFOA和PFOS的生态风险熵大于1,主要排放源为工业污水排放。LI等[5]研究表明,小清河流域道PFAAs总质量浓度高达325.280 µg·L−1。
由于PFAAs在水环境中广泛检出,故有关PFAAs的去除方法备受学者们关注。目前的去除方法集中在微波降解法、膜处理法、高级氧化法、吸附法和植物富集等。其中化学方法大多数条件复杂、能耗高,比较经济实用的方法主要为吸附法和植物吸收法[6-7]。用于处理含氟水体的吸附剂主要包括金属氧化物、离子交换树脂、沉积物、碳材料和矿物材料等,在pH、温度、吸附时间和离子强度等因素的干扰下,各吸附剂对PFAAs的吸附容量有较大波动[8]。植物修复已作为富营养化水体的常用修复技术。有研究[9]表明,除了氮磷等营养盐外,一些具有耐盐和耐毒性植物还可以直接吸收水体中的有机污染物和重金属并将其富集于体内。YIN等[10]的研究表明,芦苇床对水体中PFAAs的去除率最高可达42%~49%;孔潇潇等[11]发现,金鱼藻对PFOS的去除率可达90%以上;在实际河岸湿地植物调查中发现,凤眼莲对PFOA的生物浓缩系数最高,并且具有纤维生根系统的植物对PFOA积累量更高[12]。
已有研究表明,水生植物对单一的营养盐或全氟烷基酸污染的水体具有一定的修复效果,但关于其对于含有这些污染物复合污染水体的研究较少。基于此,本研究针对营养盐和全氟烷基酸复合污染水体的处理问题,选取4种水生植物进行室内静态水培实验,对比研究了不同水生植物对复合污染水体的修复效果,以期为水生植物在水体治理修复工程中的应用提供参考。
Removal effect of nutrient salts and perfluoroalkyl acids in waterbody with combined pollutants by 4 aquatic plants
- Received Date: 09/11/2021
- Available Online: 10/02/2022
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Key words:
- phytoremediation /
- polluted waterbody /
- nutrients salts /
- perfluoroalkyl acids
Abstract: In recent years, the exposure, source identification and removal of perfluoroalkyl acids have received extensive attentions. The existing studies mainly focused on the purification effect of perfluoroalkyl acid polluted waterbody by plants, however, few studies paid attention to the nutrient salts and perfluoroalkyl acids polluted waterbody. In this study, Tectorum, Phragmites australis, Phragmites australis and Potamogetonpusillus was selected as research objects. Laboratory hydroponic experiments were conducted to study the removal effect of nitrogen, phosphorus and perfluoroalkyl acids(PFAAs) by four plants. The results showed that all four plants had good purification effect on nutrients and perfluoroalkyl acids (PFAAs) in waterbody with combined pollutants, and different plants presented different removal effects. The removal rates of TN, TP, PFOA and PFOS were (56.36±4.83)%~(79.90±4.79)%, (47.36±2.18)%~(64.52±4.78)%, (38.25±3.25)%~(67.33±5.58)% and (46.23±3.93)%~(83.14±5.49)%, respectively. Iris tectorum showed the best removal effect of TN and TP, and the corresponding removal rates were (79.90±4.79)% and (64.52±4.78)%, respectively, but the removal rates of Iris tectorum on PFOA and PFOS were only (38.25±3.25)% and (46.23±3.93)%, respectively. Phragmites australis showed the best removal effect of perfluoroalkyl acids, the PFOA and PFOS enrichment in the plants were up to (31.56±1.01) µg·g−1 and (37.15±1.54) µg·g−1, respectively. The enrichment effect of PFOS in all plants was better than that of PFOA, and in emergent plants, PFOS was more inclined to accumulate in plant roots than PFOA.