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多环芳烃(polycyclic aromatic hydrocarbons,简称PAHs)具有“三致”效应,对人体健康的影响很大[1]. PAHs与道路灰尘颗粒或大气颗粒物结合,最终通过干湿沉降的方式进入道路灰尘中[2]. 因此,道路灰尘是PAHs累积、迁移和危害人体健康的重要环境介质[3].
道路灰尘由粒径大小不同的颗粒物组成,而PAHs在不同灰尘粒径组分中的组成和分布存在差异[4],受灰尘中的总有机碳、灰尘颗粒的表面积或污染物进入灰尘的方式等因素的影响[5]. 因此,粒径大小是影响道路灰尘环境行为的主要参数[4],也是影响其与人体接触并进入人体消化系统的一个关键因素[6]. 道路灰尘主要通过经口摄入的方式进入人体内[7 − 8],而不同粒径的灰尘进入人体内的概率不同. 与粗颗粒灰尘(粒径>250 μm)相比,细颗粒灰尘(粒径<63 μm)更容易黏附在人体皮肤上,从而更有可能通过手-口途径进入人体的消化系统[9 − 10]. 而且灰尘进入人体消化系统后,PAHs是否能被肠道吸收取决于其生物有效性[11],与PAHs的性质、载体的性质以及消化系统的环境条件等因素有关[11 − 12]. 但随灰尘进入消化系统中PAHs并非都能被人体吸收,近年来,体外消化模型常被用来模拟研究污染物在人体消化系统中的释放和吸收率[13 − 14],以准确测定人体消化系统中污染物的实际吸收率.
目前,对道路灰尘中PAHs的研究大多集中于原灰尘中PAHs的含量、来源以及人体健康风险评估等方面[7, 15],而有关灰尘不同粒径组分中的PAHs在在消化系统中的行为特征及吸收率鲜有报道,对于道路灰尘中PAHs的健康风险评估仍有许多局限性. Lorenzi等通过人体平均每日摄入量评估了城市街道灰尘的6个粒径组分中PAHs的健康风险,认为细粒径灰尘对人体的危害最大[15],但其研究结果是基于灰尘中PAHs总量,并没有考虑有效态PAHs含量. Zhang等在应用体外消化模型评估烟灰中PAHs的生物有效性研究中,利用硅胶片作为肠道中PAHs吸收的汇,通过硅胶片对PAHs吸附造成消化液与固相中PAHs的含量差来促进PAHs从固相残渣表面的解吸,模拟了PAHs在小肠中的被动分子扩散,并将消化液和硅胶片中的PAHs定义为生物有效态,据此计算PAHs生物可利用度(Bioaccessibility),这种研究方法更接近人体消化系统的实际情况[13]. 然而,利用体外消化模型并添加硅胶片的方法评估道路灰尘中PAHs生物可利用度的研究还鲜见报道.
因此,本研究将道路灰尘分成了3个粒径组分(>250 μm、250—53 μm和<53 μm),分析了不同粒径组分中PAHs的含量和组成,并通过体外消化模型研究了不同粒径灰尘中PAHs的生物可利用度和生物有效态PAHs毒性当量值的大小,研究结果有助于深入了解道路灰尘对人体的健康风险.
福州市道路灰尘中多环芳烃粒径分布、生物可利用度及其毒性当量
Distribution, bioaccessability and toxicity equivalence of polycyclic aromatic hydrocarbons in different particle-size fractions of road dust in Fuzhou
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摘要: 以福州道路灰尘为研究对象,研究了不同粒径灰尘(>250 μm、250—53 μm和<53 μm)中多环芳烃(PAHs)的含量和组成,并利用体外消化模型结合固相萃取技术评估了不同粒径灰尘中PAHs的生物可利用度以及有效态PAHs的苯并(a)芘(BaP)毒性当量浓度(TEQBaP). 结果表明,(1)不同粒径灰尘中PAHs总量随粒径减小而增加(>250 μm,0.597 mg·kg−1;250—53 μm,1.235 mg·kg−1;<53 μm,3.931 mg·kg−1). 不同粒径灰尘中PAHs组成基本相同,都为4环(58.5%±0.8%)>5环(21.5%±0.4%)>3环(13.3%±0.9%)>6环(4.8%±0.2%)>2环(2.0%±0.3%);(2)不同粒径灰尘中有效态PAHs总量随粒径减小而增加,但>250 μm粒径灰尘中PAHs的生物可利用度显著高于250—53 μm和<53 μm粒径灰尘 ( P<0.05 ) . 总体上,低环(2环、3环和4环)PAHs生物可利用度要大于高环(5环和6环)PAHs;(3)不同粒径灰尘中有效态PAHs的总TEQBaP值随粒径减小而增大,且不同粒径灰尘中4环和5环PAHs的TEQBaP值都显著高于其他环数PAHs ( P<0.05 ) . 由于不同粒径灰尘中4环PAHs含量都最高,且其具有较高的生物可利用度和TEQBaP值,因而在人体内潜在毒性风险最高.Abstract: The content and composition of polycyclic aromatic hydrocarbons (PAHs) in different particle-size fractions (>250 μm, 250—53 μm and <53 μm) of the road dust from Fuzhou city were studied. Moreover, the bioaccessability of PAHs and the toxic equivalent concentration based on the toxicity of benzo(a)pyrene (BaP) (TEQBaP) of the bioavailable PAHs in different particle-size fractions of the dust were evaluated by an in vitro digestion model combined with solid phase extraction technique. The results showed that: (1) the total contents of PAHs in different particle-size fractions of the dust increased with the decrease of particle size (>250 μm, 0.597 mg·kg−1; 250—53 μm, 1.235 mg·kg−1; <53 μm, 3.931 mg·kg−1). The compositions of PAHs in different particle-size fractions of the dust were basically the same, all of which were in the sequence of 4-ring (58.5%±0.8%)> 5-ring (21.5%±0.4%)> 3-ring (13.3%±0.9%)> 6-ring (4.8%±0.2%)> 2-ring (2.0%±0.3%); (2) The total contents of the bioavailable PAHs in different particle-size fractions of the dust increased with the decrease of particle size, but the bioaccessability of PAHs was significantly higher in the >250 μm dust than in the 250—53 μm and <53 μm dust ( P<0.05). Overall, the bioaccessability of low-ring (2-, 3-, and 4-ring) PAHs was greater than that of high-ring (5-, 6-ring) PAHs; (3) The total TEQBaP value of the bioavailable PAHs in different particle-size fractions of the dust increased with the decrease of particle size, and the TEQBaP values of 4-ring and 5-ring PAHs in different particle-size fractions of the dust were significantly higher than those of other ring number PAHs ( P<0.05 ) . The 4-ring PAH content was the highest in different particle-size fractions of the dust and they also had high bioaccessability and TEQBaP values, thus their potentially toxic risk in human was the highest.
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表 1 供试灰尘理化性质
Table 1. Physico-chemical properties of the tested dust samples
粒径/μm
Particle size总碳/(g·kg−1)
Total carbon全氮/(g·kg−1)
Total nitrogen碳氮比
C/N比表面积/(m²·g−1)
Specific surface area质量百分比/%
Mass percentage原灰尘 11.49 0.72 15.90 0.86 — >250 6.43 0.22 29.77 0.46 62.5 53—250 5.38 0.21 26.16 1.76 32.9 <53 5.61 0.35 15.99 12.01 4.6 注:“—”表示原灰尘中不存在质量百分比.
Note:“—”indicates not applicable for the bulk dust表 2 原灰尘及其粒径组分中15种PAHs含量(mg·kg−1)
Table 2. Contents of 15 PAHs in bulk dust and its particle-size fractions(mg·kg−1)
PAHs 环数
Number of rings原灰尘
Bulk dust粒径/μm
Particle size>250 53—250 <53 Nap 2 0.018 0.011 0.028 0.080 Ace 3 N.D. N.D. N.D. N.D. Flu 3 0.010 0.008 0.013 0.038 Phe 3 0.084 0.071 0.131 0.423 Ant 3 0.009 0.007 0.014 0.037 FluA 4 0.204 0.135 0.284 0.881 Pyr 4 0.148 0.102 0.212 0.652 BaA 4 0.129 0.086 0.176 0.659 Chry 4 0.033 0.023 0.046 0.144 BbF 5 0.101 0.067 0.162 0.521 BkF 5 0.029 0.022 0.042 0.134 BaP 5 0.043 0.034 0.061 0.167 DBA 5 0.005 0.004 0.005 0.016 BghiP 6 0.020 0.019 0.036 0.092 InP 6 0.012 0.010 0.024 0.087 ∑PAH15 0.844 0.597 1.235 3.931 注:N.D.代表未检出.Note:N.D.stands for not detected. -
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