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全氟化合物(perfluoroalkyl substances,PFASs)是一类碳原子连接的氢原子全部被氟原子取代的有机化合物,因其优良的理化性能,被广泛用于化工、皮革和医药等工业及日常生活领域中[1]. 近年来已在大气、水和土壤等[2-4]环境介质及生物体中[5]被广泛检出. 现有的研究已经充分证明PFASs具有内分泌毒性、致癌性、神经毒性及生殖毒性等毒理效应,对环境和生物均存在潜在风险[6-7],因此2009年和2019年,全氟辛烷磺酸(perfluorooctane sulfonate,PFOS)及其盐类、全氟辛酸(perfluorooctanoic acid,PFOA)先后被列入《斯德哥尔摩公约》并加以限制生产和使用. 然而由于经济和生产需求,PFASs的生产逐步转移到亚洲,尤其是中国[8]. PFASs一旦进入环境后能够随着大气发生长距离迁移,到达海拔较高的地区发生“高山冷凝效应”,从而导致高海拔地区成为污染物的“接收器”[9].
现有的研究证实,树木能够有效截留大气中的有机污染物[10],对有机污染物的全球迁移及分布有重要影响[11-12]. 近年来,树木年轮因其分布广泛、样本易得、连续性强等特点,已经作为环境监测的一种手段[13]. 已有学者利用树木年轮作为指示研究大气环境中的多环芳烃、多溴联苯醚等持久性有机污染物(persistent organic pollutants, POPs)[14-15]的迁移及污染特征. 然而,PFASs不同于传统的持久性有机污染物,具有高表面活性、水溶性强等特点,能否用树木年轮来指示大气中的PFASs,并且对其污染历史进行反演,目前尚不清楚. 因此,有必要展开相关研究,探讨树木年轮对大气中PFASs的指示及污染历史重建,以期为偏远地区PFASs的生态风险评估提供科学依据. 目前公认的PFASs在全球的蓄积库为海洋沉积物,而森林植被占陆地面积的31%[16],若对PFASs有富集,其蓄积量不能忽视. 然而目前鲜有研究报道PFASs在森林中的蓄积能力,因此,本研究以横断山区雅砻江下游的云南松(Pinus yunnanensis)年轮为研究对象,分析其PFASs的污染特征与来源,反演PFASs在该地区的污染历史,并计算PFASs在云南松树干中的积累量,明确森林植被对PFASs迁移蓄积的重要性.
横断山区河谷云南松中全氟化合物的历史反演及赋存特征
Historical inversion and occurrence of perfluoroalkyl substances in Pinus yunnanensis in Valley of Transverse Mountain Area
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摘要: 为研究森林树木对全氟化合物(PFASs)污染的历史变化及积累,采集了横断山区河谷云南松(Pinus yunnanensis)年轮,采用超高效液相色谱-质谱联用仪分析了树木年轮中12种PFASs的浓度水平. 分析结果表明,年轮中共有6种PFASs检出,ΣPFASs浓度范围为nd—75.7 ng·g-1,其中检出率最高的物质是PFOA(91.8%)和PFPeA(89.8%). 以PFOA、PFPeA、PFUnDA和PFHxA为主要标志物的2个主成分可以解释该地区年轮中84.4%的PFASs来源,主要来源于PFASs及其前体物的大气长距离迁移. 年轮中PFPeA含量随时间变化不符合其生产使用历史,主要受前体物的生物转化和光化学转化影响. 单位面积内云南松树干的积累量在高低海拔分别为91.3 g·km-2和22.6 g·km-2,说明云南松已成为PFASs在环境中的重要蓄积库之一,今后应进一步加强对横断山区和高海拔地区森林树木的研究,为环境中PFASs的管控提供基础数据.
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关键词:
- 全氟化合物(PFASs) /
- 横断山区河谷 /
- 云南松 /
- 历史反演 /
- 赋存.
Abstract: In order to study the historical change and accumulation of perfluoroalkyl substances in forest trees, twelve PFASs in Pinus yunnanensis’s tree rings collected in Valley of Transverse mountain area were analyzed by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). The results showed that only six PFASs were detected in the tree rings, and ΣPFASs concentrations ranged in nd— 75.7 ng·g-1, with the greatest detection frequency found in PFOA (91.8%) and PFPeA (89.8%). Two principal components with the main markers of PFOA, PFPeA, PFUnDA and PFHxA could explain 84.4% of the sources of PFASs in the growth rings in this region, which mainly came from the long-distance atmospheric migration of PFASs and their precursors. The temporal distribution of PFPeA concentrations in tree rings was not consistent with its production and use history, which was mainly affected by the biotransformation and photochemical transformation of its precursors. The accumulation of Pinus yunnanensis trunk per unit area were 91.3 g·km-2 and 23.3 g·km-2 at high and low altitudes, respectively, indicating that Pinus yunnanensis has become one of important reservoirs of perfluoroalkyl substances in the environment. Future research on the Transverse mountain area and high altitude areas should be carried out to provide basic data for the control of perfluoroalkyl substances in forest vegetation. -
表 1 树芯样本信息
Table 1. The information of tree core samples
树芯
Tree cores位置Location 海拔/m
Altitude胸围/cm
DBH树干高度/m
Tree height定年
Dating经度Longitude 纬度Latitude E1 101°41′E 26°53′N 1300 76 12 1993—2012 E2 1300 76 12 1992—2011 E3 1300 73 9 1993—2010 N1 101°39′E 26°55′N 2045 101 16 1992—2011 N2 2045 97 15 1991—2010 表 2 PFASs在年轮中的检出限及回收率
Table 2. Detection limits and recoveries of PFASs in tree rings
目标物
Objects检出限/(ng·g−1)
MDL回收率/%
Recovery(Avg±SD)加标2 ng
Add standard 2 ng加标20 ng
Add standard 20 ngPFBA 0.003 98.0±1.1 96.1±0.3 PFPeA 0.007 78.9±10.3 74.5±3.0 PFHxA 0.022 100.7±0.6 89.2±1.7 PFHpA 0.002 98.1±4.9 96.5±8.7 PFOA 0.012 98.2±3.2 88.8±1.0 PFNA 0.004 97.0±1.6 86.2±0.5 PFDA 0.011 100.4±1.7 90.1±1.8 PFUnDA 0.006 98.5±5.4 86.2±1.9 PFDoDA 0.006 98.0±1.8 87.5±1.5 PFBS 0.012 76.3±6.8 72.5±8.1 PFHxS 0.008 99.3±5.9 98.9±1.4 PFOS 0.005 97.1±1.8 92.0±1.1 -
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