全氟羧酸化合物在氟化工园区土壤-植物中的分布及组成特征

Distribution and composition of perfluorocarboxylic acid substances in the soil-plant system around a fluorochemical manufacturing park

本次研究分析了典型氟化学工业园区周边不同植物及其根际和非根际土壤中全氟羧酸(perfluorinated carboxylic acid,PFCA)的含量、组成及分布特征。结果显示,PFCA在根际土壤和非根际土壤的浓度范围分别为9.6~160 ng/g和7.2~300 ng/g。根际土壤(rhizospheric soil,RS)和非根际土壤(non-rhizopsheric soil,NRS)中PFCA的浓度比值(c_(ratio)=c_(RS)/c_(NRS))显示,PFCA并未呈现出根际富集效应。PFCA在植物地上部和根部的浓度范围分别为6.0~630 ng/g和6.1~570 ng/g。全氟辛酸(perfluorooctanoic acid,PFOA)是土壤和植物组织中最主要的全氟羧酸化合物,其浓度在根际土、非根际土、植物根部和地上部分别占总PFCA的(53±18)%、(51±22)%、(80±6.7)%和(34±18)%。短链(C_(4)~C_(8))的PFCA,包括全氟丁酸(perfluorobutyric acid,PFBA)、全氟戊酸(perfluoropentanoic acid,PFPeA)、全氟己酸(perfluorohexanoic acid,PFHxA)、全氟庚酸(perfluoroheptanoic acid,PFHpA)和PFOA,在植物地上部中的浓度及检出率均高于长链(C_(9)~C_(16))的PFCA,说明短链PFCA比长链PFCA更容易在植物组织中富集。植物PFCA组成特征显示,PFBA和PFHxA在植物地上部所占的比例高于根部,说明PFBA和PFHxA等碳链较短的PFCA可能更容易被植物根系吸收并转移至植物地上部;然而PFOA在植物地上部的百分含量低于植物根部,说明PFOA可能趋向于吸附在植物根系表皮而难以往植物地上部迁移。根部到地上部的转运系数与PFCA的碳链长度呈显著负相关关系。

We investigated the distribution and composition of perfluorocarboxylic acids(PFCA)in soils and plants around a fluorochemical manufacturing park.The concentrations of total PFCA in rhizosphere soil(RS)and non-rhizosphere soil(NRS)were in the ranges of 9.6–160 ng/g and 7.2–300 ng/g,respectively.The variation in c_(ratio)(c_(RS)/c_(NRS))among plant species indicated that PFCA was not enriched in the rhizosphere.The concentration of total PFCA ranged from 6.0 ng/g to 630 ng/g in shoots and from 6.1 ng/g to 570 ng/g in roots.The predominance of perfluorooctanoic acid(PFOA)was consistently observed in NRS,RS,roots,and shoots,with percentages of(53±18)%,(51±22)%,(80±6.7)%,and(34±1.8)%,respectively.Short-chained PFCA(C_(4)–C_(8))showed higher concentrations and detection frequencies in shoots than long-chained PFCA(C>8),thereby indicating that short-chained PFCA are more prone to be enriched in plant tissues compared with long-chained PFCA.The higher percentages of perfluorobutanic acid(PFBA)and perfluorohexanoic acid(PFHxA)in shoots than in roots indicated that short-chained PFCA could be absorbed by roots and acropetally transferred to shoots.In contrast,PFOA was adsorbed onto roots and difficult to be translocated to the plant shoots,given that a lower percentage of PFOA was observed in shoots than in roots.These findings are supported by the significant and negative correlation observed between the translocation factor and chain length.The results of this study will help understand the fate of PFCA within the soil-plant system.