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室内降尘是诸多有毒污染物质的运载体和反应床。其中所携带重金属可以通过手-口摄食、呼吸摄入、皮肤接触等途径进入人体并在脂肪和内脏组织中积累,可能引发癌症、皮肤病、心血管疾病和糖尿病等健康损伤[1-3]。手-口摄食是室内降尘的人体暴露主要途径[4],因此对经胃肠道的降尘中重金属的健康风险评价尤为重要。目前降尘中重金属健康风险评价的研究多基于总量分析,即通过测定降尘中重金属的总暴露剂量以评价其人体健康风险。然而,降尘进入胃肠道环境后,其中的重金属并不能完全溶出,从而被人体吸收并造成危害。仅通过分析重金属的总量,可能会导致降尘中重金属的人体健康风险被高估。因此,需考虑重金属的生物有效性(bioavailability),从而更加真实、准确地评估室内降尘中重金属的人体健康风险[5]。
重金属的生物有效性测定常需开展动物实验,然而动物实验多存在费用高、周期长、重复性差等问题,同时也容易引起伦理方面的争议,限制了其广泛应用[6-7]。因此,目前普遍采用体外提取的方法测定重金属的生物可给性(bioaccessibility)。传统的体外提取方法众多,主要包括单步溶剂提取法、连续提取法和体外胃肠道模拟消化法。单步溶剂提取法的提取剂(如CaCl2和EDTA等)成本较低,操作简便,但试剂用量需要针对不同情况进行调整,提取量与实际生物可给性部分只存在统计学关系[8]。连续提取法(如Tessier法和BCR法等)可分析降尘中重金属的赋存形态,有较好的重现性,在一定程度上能反映大气降尘中重金属的生物有效性。但其缺少统一的操作规范,且提取剂的选择性差,各提取态之间存在交叉影响[9]。体外胃肠道模拟消化法的分析结果通常与动物实验相关性高,是目前优选的生物可给性分析法。然而,不同体外胃肠道模拟消化法所采用的消化液组分、pH值和消化时间等参数各不相同,结果缺乏可比性,并且操作较为复杂[1]。
软饮料是人们日常生活中的常见饮品,具有廉价易得的优势。特别是已有研究表明软饮料可作为提取剂,用于土壤中重金属生物可给性的分析。Schnug等[10]发现,普通可乐作为提取剂可用于分析基于作物生长情况的农田土壤中重金属的生物可给性,其分析结果与EDTA提取法存在着较好的相关性。Lottermoser等[11]进一步以3种可乐作为提取剂,分析铀废矿土壤中铀的生物可给性,发现其分析结果与传统的DTPA和CaCl2提取法均具有较好的相关性。然而,目前尚未有基于软饮料提取法对降尘中重金属生物可给性分析的研究。
综上所述,本文对中国南北方的典型地区室内降尘开展如下研究:(1)采用HNO3-HCl消解法对室内降尘中重金属进行总量测定,并对其污染水平进行评价;(2)采用改进的BCR连续提取法分析室内降尘中重金属的形态;(3)采用一种典型的体外胃肠道模拟法(solubility bioavailability research consortium, SBRC)和磷酸单步提取法分析重金属生物可给性;(4)以软饮料(普通可乐和零度可乐)作为提取剂,构建新型室内降尘中重金属的生物可给性模型。
基于软饮料法分析室内降尘重金属生物可给性
Research on bioaccessibility of heavy metals in indoor dusts based on soft drink extraction
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摘要: 近年来,生物可给性被广泛用于降尘中重金属的健康风险评价,然而传统的生物可给性分析方法存在诸多局限性。鉴于软饮料具有廉价易得的优势,本研究以室内降尘为研究对象,在对其重金属总量、形态和传统生物可给性分析的基础上,进一步通过相关性分析,探讨基于软饮料的新型室内降尘中重金属生物可给性分析方法的可能性。结果表明,室内降尘样品中重金属V、Cr、Co、Ni、Cu、As、Mo、Cd和Pb的总量平均值分别为44.92、76.06、10.05、51.88、108.73、19.94、5.62、3.49、106.09 mg·kg−1。地积累指数法表明室内降尘中Cd为严重污染。9 种重金属形态占比最高的均为F4(残渣态)。各生物可给性分析方法总体提取率由大到小依次为SBRC提取法>磷酸提取法>零度可乐提取法>普通可乐提取法。软饮料提取法(特别是零度可乐法)的重金属提取量分别与BCR法中的生物可利用态(F1+F2+F3)和SBRC提取法的提取量均呈现显著相关(P < 0.05),具有较大的实用价值和可行性。本研究以期为降尘中重金属的健康风险评价提供更为详实的理论基础。Abstract: Recently, bioaccessibility has been widely applied in health risk assessment of dusts, while the traditional analysis methods for bioaccessibility have many limitations. Since the soft drinks have the low-cost advantage, the contents, chemical fractions, and bioaccessibility based on the traditional methods of heavy metals in the indoor dusts were firstly analyzed in this study, and then a new bioaccessibility analysis method based on soft drink extraction was established by correlation analysis. The results showed that the average contents of heavy metals (including V, Cr, Co, Ni, Cu, As, Mo, Cd and Pb) in the indoor dusts were 44.92, 76.06, 10.05, 51.88, 108.73, 19.94, 5.62, 3.49, 106.09 mg·kg−1, respectively. The geoaccumulation index showed that Cd was heavily contaminated in China. Among the chemical fractionations of all the heavy metals, the residual fraction (F4) had the highest concentration. For the extraction rates, the four different methods were ranked in the following order, SBRC > phosphoric acid extraction method > Coke Zero > Coca Cola Classic. The heavy metal concentrations extracted by soft drinks, especially Coke Zero, were well correlated with those extracted by BCR (F1+F2+F3) and SBRC (P < 0.05) methods, which showed that Coke Zero has greater practical value for the determination of bioaccessibility. This research will provide more theoretical basis for the health risk assessment of heavy metals in dusts.
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Key words:
- indoor dust /
- heavy metal /
- bioaccessibility /
- soft drinks
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表 1 室内降尘中重金属总量(mg·kg-1)
Table 1. Heavy metal contents in the indoor dusts (mg·kg-1)
V Cr Co Ni Cu As Mo Cd Pb 室内降尘
(n=18)最小值 21.44 16.13 5.85 13.87 7.33 5.82 0.66 0.14 11.73 最大值 79.16 330.60 18.76 180.59 318.01 43.67 22.09 11.54 282.20 平均值 44.92 76.06 10.05 51.88 108.73 19.94 5.62 3.49 106.09 中位数 42.43 56.32 9.05 37.67 96.66 17.17 3.90 2.43 92.83 标准差 15.24 70.75 3.58 45.35 84.01 11.44 5.80 3.27 70.96 变异系数/% 35.92 125.62 39.55 120.39 86.91 66.61 148.81 134.63 76.44 全国-非工业区[17] — 132.82 — 42.51 116.12 38.16 — 3.31 170.97 全国-工业区[17] — 206.97 — 50.06 332.67 369.39 — 22.02 861.72 中国土壤背景值[16] 82.4 61.0 12.7 26.9 22.6 11.2 2.0 0.097 26.0 表 2 重金属不同提取态间的相关系数(n=16)
Table 2. Correlation coefficients for heavy metal concentrations detected in different extracts (n=16)
V Cr Co Ni Cu As Mo Cd Pb SBRC-F1 0.621** 0.465 0.847** 0.930** 0.879** 0.876** 0.974** 0.901** 0.881** SBRC- (F1+F2+F3) 0.787** 0.395 0.925** 0.956** 0.861** 0.846** 0.977** 0.968** 0.906** 磷酸-F1 0.423 0.616* 0.889** 0.988** 0.967** 0.879** 0.975** 0.953** 0.943** 磷酸- (F1+F2+F3) 0.588* 0.598* 0.923** 0.938** 0.868** 0.843** 0.965** 0.894** 0.740** SBRC-磷酸 0.447 0.456 0.897** 0.904** 0.770** 0.943** 0.943** 0.898** 0.776** 普通可乐-F1 0.641** 0.497 0.464 0.837** 0.802** 0.816** 0.976** 0.843** 0.921** 普通可乐-(F1+F2+F3) 0.778** 0.562* 0.416 0.732** 0.731** 0.812** 0.972** 0.765** 0.666** 普通可乐-SBRC 0.734** 0.293 0.535* 0.810** 0.810** 0.842** 0.964** 0.772** 0.762** 普通可乐-磷酸 0.547* 0.193 0.540* 0.815** 0.730** 0.956** 0.931** 0.877** 0.932** 零度可乐-F1 0.687** 0.807** 0.775** 0.909** 0.749** 0.864** 0.797** 0.838** 0.925** 零度可乐-(F1+F2+F3) 0.717** 0.546* 0.754** 0.909** 0.732** 0.840** 0.805** 0.770** 0.754** 零度可乐-SBRC 0.588* 0.525* 0.720** 0.885** 0.845** 0.882** 0.858** 0.769** 0.723** 零度可乐-磷酸 0.594* 0.342 0.689** 0.888** 0.632** 0.967** 0.677** 0.862** 0.951** 零度可乐-普通可乐 0.922** 0.734** 0.877** 0.875** 0.949** 0.971** 0.888** 0.988** 0.917** **P < 0.01;*P < 0.05. -
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