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多环芳烃(polycyclic aromatic hydrocarbons,PAHs)是一类全球普遍存在的半挥发性有机污染物[1 − 3]. 研究表明,大气中的PAHs组分的致突变活性在大气污染物各组分中占比为35%—82%,且主要来自人为源[4 − 5]. 煤炭在当前我国能源消费结构中仍处于重要地位,但煤炭燃烧也是造成我国雾霾频发的重要因素之一[6 − 8]. 在煤炭燃烧过程中,会通过低温挥发和高温自由基缩合反应等途径生成和释放PAHs[9 − 11]. 认清燃煤电厂PAHs的排放特征是其污染控制及环境影响评价的基础和前提,但对于燃煤电厂烟气排放过程PAHs在细颗粒物中的迁移转化行为尚缺乏系统的研究.
特征比值法常被用来解析环境中PAHs的来源,但是由于PAHs异构体具有较大的内源变异性,且其降解转化和大气迁移过程也会改变PAHs的分子组成,使分析结果具有较大不确定性[12 − 14]. 单体稳定同位素分析法已普遍应用于环境痕迹调查,研究者通过分析不同燃烧源(如木材、甘蔗的燃烧、柴油车和汽油车尾气)PAHs的单体同位素值构建了人为源PAHs单体同位素数据库[15 − 18],并探讨了13C生成途径,为其环境来源解析提供了有力证据. 研究表明,与PAHs特征比值较大的差异性不同,PAHs单体同位素比值(δ13C)受生物降解及光降解的作用不明显[19],表明出较强的源解析能力. 前期研究表明,燃煤电厂排放烟气中PAHs的含量和组成与锅炉类型、燃烧条件(如给煤性质、锅炉负荷、操作条件等)以及污染物控制过程等因素密不可分;燃煤产物(如飞灰、底灰、脱硫石膏等)中PAHs的赋存特征受其物化性质(包括粒径、残留碳和矿物种类)等因素控制[20 − 22]. 本次对安徽淮南3家粉煤炉电厂排放烟气中的可吸入颗粒物(PM2.5–10、PM1–2.5、PM1)中PAHs的含量、组成及PAHs单体同位素值进行了系统研究.
粉煤炉电厂烟气颗粒物中多环芳烃的赋存特征及源解析意义
Occurrence of polycyclic aromatic hydrocarbons in inhalable particulate matters emitted from pulverized coal boilers of coal-fired power plant and source apportionment implications
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摘要: 针对安徽淮南3家粉煤炉燃煤机组排放的烟气,分析了可吸入颗粒物(PM2.5–10、PM1–2.5、PM1)中多环芳烃(PAHs)的浓度和组成及PAHs单体同位素的值. 研究表明,烟气颗粒物中PAHs排放浓度主要受锅炉类型、燃烧参数和大气污染控制设施等因素的影响. 细颗粒物易富集PAHs,且对高分子量PAHs的富集程度更高. 不同粒度颗粒物中PAHs特征比值的变化幅度较小,但对不同燃煤源排放的PAHs仍有较大的不确定性. PAHs单体碳同位素值有效区别燃煤锅炉源、生物质燃烧和车辆尾气排放源,但对于粉煤炉的不同燃烧过程指示不明显.Abstract: The concentrations, distributions, and stable carbon isotope compositions of polycyclic aromatic hydrocarbons (PAHs) in inhalable particulate matters (PM2.5–10, PM1–2.5, and PM1) emitted from three pulverized coal boilers of coal-fired power plants (CFPPs) in Anhui, China were investigated. Results indicate that PAH concentrations and distributions in PM2.5–10, PM1–2.5, and PM1 were affected by the boiler type and operating conditions of air pollution control devices. The fine particles tended to enrich high molecular weight PAHs compared to coarse particles. The diagnostic ratios of PAHs varied insignificantly among different boilers, suggesting a potential to trace CFPP-based combustion sources in the environment. However, they can not be used to trace emission sources from different types of coal boilers of CFPPs due to their large variations. The stable carbon isotope compositions of PAHs showed significant variations among the emission sources of CFPPs, biomass burning, and vehicle exhaust. They varied insignificantly in the processes of PAH formation during coal combustion from pulverized coal boilers and the subsequent transfer of flue gas.
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表 1 本实验采样的基本信息
Table 1. Basic information of sampling
参数
Parameter粉煤炉类型
Pulverized coal furnace typeHPA-1 HPA-2 HPA-3 HPB-1 HPB-2 HPC-1 运行条件 亚临界 亚临界 亚临界 亚临界 亚临界 超临界 燃煤机组容量/MW 300 300 300 600 600 600 大气污染控制设施 ESPs ESPs ESPs+WFGD ESPs ESPs+WFGD ESPs+WFGD 烟气流速/(m·s–1) 8.7 11.4 9.3 9.8 7.9 10.1 烟气温度/℃ 69.4 67.2 72.3 74.5 68.5 73.5 表 2 不同采样点烟气颗粒物中PAHs的含量
Table 2. PAHs concentrations in particulate matters of flue gas at different sampling sites
PAHs PM2.5-10/(µg·m−3) PM1-2.5/(µg·m−3) PM1/(µg·m−3) 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 Nap 0.43 0.29 0.32 0.27 0.22 0.17 0.31 0.29 0.36 0.25 0.25 0.15 0.28 0.17 0.23 0.18 0.13 0.13 Acy 0.34 0.32 0.28 0.23 0.26 0.18 0.48 0.47 0.24 0.26 0.24 0.21 0.45 0.53 0.23 0.28 0.23 0.19 Ace 0.25 0.23 0.19 0.15 0.17 0.13 0.15 0.16 0.12 0.13 0.15 0.13 0.19 0.21 0.13 0.21 0.18 0.13 Flu 0.29 0.18 0.17 0.14 0.14 0.12 0.3 0.29 0.17 0.18 0.12 0.14 0.28 0.31 0.15 0.18 0.13 0.18 Ant 0.31 0.31 0.16 0.19 0.20 0.12 0.33 0.31 0.16 0.18 0.18 0.13 0.31 0.26 0.18 0.19 0.15 0.19 Phe 0.17 0.19 0.11 0.16 0.15 0.09 0.26 0.25 0.14 0.15 0.12 0.11 0.26 0.23 0.20 0.21 0.19 0.14 Fla 0.93 1.0 0.89 0.87 0.61 0.45 1.4 1.3 0.93 0.88 0.82 0.48 2.0 1.8 1.4 1.8 1.1 0.72 Pyr 0.77 0.87 0.69 0.58 0.38 0.28 1.3 1.3 0.86 0.96 0.64 0.46 1.6 1.7 0.91 1.4 0.78 0.58 BaA 0.5 0.36 0.43 0.44 0.37 0.32 0.96 0.96 0.57 0.83 0.48 0.37 1.9 1.7 1.1 1.2 0.87 0.67 Chr 0.47 0.47 0.22 0.29 0.28 0.18 0.93 1.1 0.61 0.94 0.49 0.32 1.4 1.6 1.0 1.2 1.0 0.59 BbF 0.63 0.51 0.25 0.38 0.16 0.19 1.1 1.0 0.51 0.71 0.41 0.28 1.6 1.2 1.3 1.2 0.66 0.56 BkF 0.47 0.37 0.19 0.33 0.18 0.16 0.63 0.68 0.34 0.34 0.21 0.17 0.97 0.96 0.54 0.69 0.37 0.27 BaP 0.41 0.31 0.13 0.29 0.13 0.10 0.95 0.94 0.39 0.54 0.34 0.26 1.7 1.6 1.2 1.2 0.74 0.53 DahA 0.52 0.35 0.16 0.23 0.12 0.11 0.64 0.45 0.33 0.42 0.17 0.18 0.78 0.94 0.49 0.74 0.52 0.39 InP 0.55 0.38 0.16 0.29 0.11 0.14 0.74 0.74 0.38 0.69 0.28 0.21 1.2 1.1 0.63 1.1 0.58 0.35 BghiP 0.41 0.31 0.17 0.44 0.11 0.12 0.79 0.63 0.31 0.56 0.24 0.22 1.4 1.3 0.87 1.3 0.68 0.48 总含量 7.45 6.45 4.52 5.28 3.59 2.86 11.27 10.87 6.42 8.02 5.14 3.82 16.32 15.61 10.56 13.08 8.31 6.10 注:1:HPA-1,2:HPA-2,3:HPA-3,4:HPB-1,5:HPB-2,6:HPC-1 表 3 原料煤和烟气颗粒物中单体PAHs同位素(δ13C, ‰)组成
Table 3. Molecular isotopic compositions (δ13C, ‰) of individual PAHs in raw coal and particulate matters
PAHs Coal HPA-1 HPA-2 HPA-3 HPB-1 HPB-2 HPC-1 Phe −24.6 −27.8 −27.6 −28.1 −27.8 −28.2 −28.2 Ant −24.2 −28.1 −27.8 −28.0 −28.0 −28.3 −28.2 Fla −25.2 −28.4 −28.4 −28.4 −28.6 −28.5 −28.7 Pyr −25.3 −28.3 −28.5 −28.5 −28.3 −28.4 −28.6 BaA −25.4 −28.5 −28.3 −28.7 −28.5 −28.6 −28.7 Chr −25.3 −28.6 −28.4 −28.6 −28.5 −28.5 −29.1 BkF −25.4 −28.3 −28.2 −28.6 −28.7 −28.7 −29.3 BaP −26.2 −29.0 −28.7 −29.5 −29.4 −29.4 −29.7 InP −26.2 −29.2 −29.0 −29.9 −30.0 −30.1 −30.4 BghiP −26.5 −29.5 −29.4 −30.0 −29.8 −30.0 −30.2 -
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