李艷靜,張素坤,馮桂賢,任明忠*張漫雯,許振成,張入元,完顏華 (.環(huán)境保護(hù)部華南環(huán)境科學(xué)

李艷靜1,2,張素坤1,馮桂賢1,任明忠1*張漫雯1,許振成1,張入元2,完顏華2(1.環(huán)境保護(hù)部華南環(huán)境科學(xué)

采集了機(jī)械爐排焚燒爐和循環(huán)流化床焚燒爐兩種典型生活垃圾焚燒爐排放煙氣樣品,應(yīng)用高分辨氣相色譜/高分辨質(zhì)譜(HRGC/HRMS)同位素內(nèi)標(biāo)稀釋法分別測(cè)定了煙氣不同相樣品中17種2,3,7,8-位氯取代的PCDDs/PCDFs同類物的含量.結(jié)果表明,兩種爐型中PCDDs/PCDFs同類物及毒性當(dāng)量貢獻(xiàn)率在冷凝水相中所占的比例均在85%以上,遠(yuǎn)遠(yuǎn)高于在濾筒相和XAD-2樹脂相中所占的比例,機(jī)械爐排爐焚燒排放煙氣中∑PCDFs與∑PCDDs的比值為0.77;而循環(huán)流化床焚燒排放煙氣∑PCDFs與∑PCDDs的比值為5.28.機(jī)械爐排爐焚燒煙氣三相中OCDD為優(yōu)勢(shì)分布,尤其是濾筒相中OCDD的百分比含量高達(dá)51.1%.流化床焚燒爐焚燒煙氣濾筒、樹脂、冷凝水相中沒有出現(xiàn)某個(gè)單體對(duì)總濃度具有絕對(duì)優(yōu)勢(shì)的貢獻(xiàn).機(jī)械爐排焚燒爐和循環(huán)流化床焚燒爐排放的煙氣中PCDFs的毒性當(dāng)量貢獻(xiàn)最大,尤其是單體2,3,4,7,8-PeCDF對(duì)總毒性當(dāng)量的貢獻(xiàn)均在30%以上.

生活垃圾焚燒；機(jī)械爐排爐；循環(huán)流化床；二；分布特征

本文采用EN1948[11]非稀釋采樣方法采集了兩種典型生活垃圾焚燒爐焚燒排放煙氣中的樣品,利用高分辨氣相色譜/高分辨質(zhì)譜同位素內(nèi)標(biāo)稀釋法對(duì)玻璃纖維濾筒相、XAD-2樹脂相和冷凝水相中的17種二同類物進(jìn)行了測(cè)定.

1 實(shí)驗(yàn)部分

1.1 主要儀器與試劑

高分辨氣相色譜/高分辨雙聚焦磁式質(zhì)譜聯(lián)用儀(Agilent 6890N-Autospec Premier,);EN1948非稀釋法自動(dòng)等速煙道氣采樣器(ISOSTACK BASIC型,意大利 Tecora公司);旋轉(zhuǎn)蒸發(fā)儀(R-215型,瑞士 Buchi公司);MGS氮吹儀(MG-2200型,日本Eyela公司);加速溶劑萃取儀(ASE300型,美國Dionex公司);液液萃取自動(dòng)震蕩器(MMV-1000W型,日本Eyela公司),真空干燥器(Vacucenter VC50型,瑞士SalvisLAB公司).

農(nóng)殘級(jí)正己烷、甲苯、二氯甲烷、丙酮、甲醇購自美國B&J公司及美國J.Tbaker公司.高純度中性硅膠(80～200目)、高純度堿性氧化鋁(100～200目)和弗羅里硅土(Florisil)購自德國Merck公司及美國 Sigma-Aldrich公司.XAD-2樹脂購自美國 Sigma-Aldrich公司,玻璃纖維濾筒購自日本Toyo Roshi Kaisha公司.

PCDDs/PCDFs系列用標(biāo)樣(CSV)、13C標(biāo)記采樣內(nèi)標(biāo)(EPA23 SSS 5種)、提取內(nèi)標(biāo)(EPA23 IS 10種, EPA1613 LCS 15種)及進(jìn)樣內(nèi)標(biāo)(EPA23 RS 2種)均購自加拿大Wellington實(shí)驗(yàn)室.

1.2 樣品的采集和凈化

1.2.1 樣品的采集 玻璃纖維濾筒使用前在馬弗爐中450℃高溫灼燒4h;XAD-2樹脂依次用去離子水和丙酮清洗3遍,真空干燥后以甲苯為溶劑用ASE凈化;采樣器各關(guān)鍵連接部分使用前依次用去離子水、甲醇、丙酮、二氯甲烷、甲苯和正己烷清洗.處理后的采樣用品用容器密封和錫箔紙包裹運(yùn)輸至采樣點(diǎn).采用意大利TECORA公司ISOSTACK BASIC型采樣系統(tǒng),根據(jù)煙氣工況參數(shù)進(jìn)行自動(dòng)等速采樣.采樣前在 XAD-2樹脂中添加EPA23SS采樣內(nèi)標(biāo).經(jīng)檢驗(yàn)確認(rèn)采樣系統(tǒng)不漏后開始采樣,采樣時(shí)間約 2h,采樣量標(biāo)況量約 3m3.采樣完成后密封低溫保存運(yùn)回實(shí)驗(yàn)室.生活垃圾焚燒爐的主要運(yùn)行參數(shù)見表1.

表1 兩種類型垃圾焚燒爐主要參數(shù)Table1 Major parameters for the two typical municipal waste incinerators

1.2.2 樣品提取與凈化 冷凝水和濾筒提取前添加 EPA1613ISS內(nèi)標(biāo)混合液,而樹脂提取液添加EPA23ISS內(nèi)標(biāo)混合液,添加量為1～2ng/樣品.冷凝水樣品中的二,以二氯甲烷為溶劑使用分液漏斗進(jìn)行液-液萃取.濾筒和樹脂充分干燥后,分別以甲苯為溶劑進(jìn)行索氏抽提.所有樣品的凈化流程相同,樣品提取液經(jīng)旋轉(zhuǎn)蒸發(fā)濃縮后,依次通過酸性硅膠柱、多段硅膠柱、堿性氧化鋁和弗羅里硅土復(fù)合柱凈化,用不同配比的正己烷和二氯甲烷溶劑淋洗和洗脫,收集含 PCDDs/ PCDFs的洗脫液[12],將洗脫液旋轉(zhuǎn)蒸發(fā)濃縮后,用高純氮吹掃濃縮定容至 20μL,加入進(jìn)樣內(nèi)標(biāo)低溫保存,最后HRGC/HRMC儀器分析.

1.3 分析條件

HRGC/HRMS的分析條件如下:升溫程序,初始溫度為140℃,保持2min,然后以8℃/min升至220℃, 1.4℃/min升至260℃,4℃/min升至310℃,保持4min,載氣流速為 1.0mL/min,色譜柱為 DB-5MS (60m× I.D.0.25mm×0.25μm filter),無分流進(jìn)樣,進(jìn)樣量為1μL,進(jìn)樣口溫度為250℃;質(zhì)譜條件:電離能為35eV,阱電流為 600μA,EI模式,離子源溫度為 300℃;分辨率＞10000,選擇性離子監(jiān)測(cè)(SIM),傳輸線溫度為300℃.

1.4 質(zhì)量保證與質(zhì)量控制

采樣空白和實(shí)驗(yàn)室空白未檢出目標(biāo)物,13C標(biāo)記采樣標(biāo)回收率＞70%,提取內(nèi)標(biāo)回收率在60%～130%,符合EPA23A[13]和EPA1613B[14]方法的定量要求,方法檢出限為0.002～0.032 ng/m3.

2 結(jié)果與討論

2.1 PCDDs/PCDFs的相態(tài)分布特征

就濃度而言,機(jī)械爐排爐焚燒濾筒相和冷凝水相中∑PCDFs的濃度低于∑PCDDs的濃度,并且高氯代DFs/DDs在上述兩相中為優(yōu)勢(shì)分布,樹脂相的分布特征與上述兩相不同,∑PCDFs的濃度略高于∑PCDDs的濃度,且低氯代DFs的含量略高于高氯代DFs含量,高氯代PCDDs略高于低氯代PCDDs的含量,將三相合并在一起,煙氣中∑PCDFs與∑PCDDs的比值為0.77;循環(huán)流化床焚燒排放煙氣三相中低氯代DFs/DDs的濃度低于高氯代的濃度,三相綜合在一起∑PCDFs與∑PCDDs的比值為5.28,∑PCDFs的濃度明顯高于∑PCDDs的濃度.根據(jù)Everaert和aeyens的研究結(jié)果,本研究中的機(jī)械爐排焚燒爐焚燒排放煙氣中的PCDDs/PCDFs可能主要來自“從頭合成”過程[16],即碳、氫、氧和氯等元素通過基元反應(yīng)生成二.而流化床焚燒爐焚燒煙氣中PCDDs/PCDFs主要是由前驅(qū)體機(jī)制合成的[3].

表2 PCDDs/PCDFs在不同相中的比例(%)Table 2 Concentration percentages of PCDDs/PCDF congeners among different phases in stack gas(%)

圖1 不同相PCDDs/PCDFs單體對(duì)總濃度的貢獻(xiàn)率Fig.1 Ratios of concentration contributions by 2,3,7,8-PCDDs/PCDFs congeners in different phases

就毒性當(dāng)量而言,機(jī)械爐排焚燒爐濾筒相、XAD-2樹脂相、冷凝水相中∑PCDDs對(duì)I-TEQ平均貢獻(xiàn)率分別為29.34%、28.92%、23.84%,該結(jié)果明顯高于循環(huán)流化床焚燒爐不同分配相中∑PCDDs對(duì) I-TEQ的貢獻(xiàn)率,其結(jié)果分別為13.81%、17.28%、14.41%,∑PCDFs對(duì)I-TEQ的貢獻(xiàn)率則循環(huán)流化床焚燒爐高于機(jī)械爐排焚燒爐.

楊志軍等[8]對(duì)我國東北某循環(huán)流化床焚燒爐排放煙氣樣品進(jìn)行的相態(tài)研究結(jié)果表明, PCDDs/PCDFs主要分布于濾筒相中,與本研究結(jié)果不同,但上述研究并沒有提到冷凝水相中PCDDs/PCDFs的分布情況,也未提應(yīng)用的采樣方法.Chi等[17]對(duì)臺(tái)灣兩種垃圾焚燒爐排放煙氣中的二的相態(tài)分布特征的研究表明,氣相中二貢獻(xiàn)比例最大,與本研究結(jié)果相似.

2.2 PCDDs/PCDFs單體的相態(tài)分布特征

由圖 1可見,機(jī)械爐排爐焚燒煙氣三相中OCDD為優(yōu)勢(shì)分布,尤其是濾筒相中OCDD的百分比含量高達(dá) 51.1%.流化床焚燒爐焚燒煙氣濾筒、樹脂、冷凝水相中含量最豐富的分別是1,2,3,4,6,7,8-HpCDF、2,3,7,8-TCDF 和 2,3,4,7, 8-PeCDF,與其相對(duì)應(yīng)的數(shù)值分別為 23.0%、15.6%和18.9%.由此可見在流化床焚燒爐不同相中沒有出現(xiàn)某個(gè)單體對(duì)總濃度具有絕對(duì)優(yōu)勢(shì)的貢獻(xiàn).機(jī)械爐排焚燒爐在濾筒、樹脂、冷凝水中PCDDs對(duì)總濃度的貢獻(xiàn)要高于流化床焚燒爐PCDFs對(duì)總濃度的貢獻(xiàn)則相反.

無論是機(jī)械爐排爐還是循環(huán)流化床焚燒爐排放的煙氣中PCDFs的毒性當(dāng)量貢獻(xiàn)最大,其中單體2,3,4,7,8-PeCDF對(duì)總毒性當(dāng)量的貢獻(xiàn)最大,均在30%以上.

3 結(jié)論

1,2,3,7,8,9-HxCDF外,兩爐型PCDDs/PCDFs各個(gè)單體在冷凝水中均是最大,且遠(yuǎn)遠(yuǎn)高于濾筒和樹脂,大部分在 90%左右,樹脂和濾筒則均不到10%,表明爐型對(duì)焚燒過程中產(chǎn)生的 PCDDs/ PCDFs在不同相中的分配影響較小.

3.3 不同分配相中∑PCDFs對(duì)總毒性當(dāng)量的貢獻(xiàn)均高于∑PCDDs.同一爐型不同相間∑PCDFs/∑PCDDs的比值相差不大,但兩爐型間差別較大,說明爐型對(duì)∑PCDFs/∑PCDDs比值的大小有影響,流化床中呋喃類對(duì)毒性當(dāng)量的貢獻(xiàn)大于機(jī)械爐排焚燒爐.

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Multiphase distribution characteristics of PCDDs/PCDFs from two typical municipal waste incinerators.

LI Yan-jing1,2, ZHANG Su-kun1, FENG Gui-xian1, REN Ming-zhong1*, ZHANG Man-wen1, XU Zhen-cheng1, ZHANG Ru-yuan2, WANYAN hua2(1.South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou 510655, China;2. Institute of Environment and Municipal Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China). China Environmental Science, 2011,31(10)：1632～1636

Samples of stack gas were collected from two typical municipal waste incinerators, i.e., mechanical stoker incinerator and fluidized-bed incinerator, and the concentrations of PCDDs/PCDFs in these samples were determined with internal standard-calibrated isotope dilution method in combination with high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). Average percentages of PCDDs/PCDFs and their toxicity equivalents were both above 85% in condensate water phase, which were much higher than that in filter thimble phase and in XAD-2 resin phase for the two incinerators; the ratio of ∑PCDFs to ∑PCDDs was as low as 0.77 in stack gas from mechanical stoker incinerator, but turned out to be as high as 5.28 in stack gas from fluidized bed incinerator. Among the three phases of stack gas from the mechanical stoker incinerator, the PCDDs/PCDFs were found to be dominated by OCDD, with the concentration of OCDD being up to 51.1% particularly in the filter thimble phase. However, among the three phases of stack gas from the fluidized-bed incinerator, the PCDDs/PCDFs were found to be not dominated by a single congener. In stack gas from both incinerator types, PCDFs showed the highest contribution to toxicity equivalent (I-TEQ), and particularly, 2,3,4,7,8-PeCDF made higher than 30% contribution to the total toxicity equivalent.

municipal waste incineration；mechanical stoker incinerator；fluidized bed incinerator；dioxin；distribution characteristics

研究所,廣東 廣州 510655；2.蘭州交通大學(xué)環(huán)境與市政工程學(xué)院,甘肅 蘭州 730070)

X502

A

1000-6923(2011)10-1632-05

2011-01-25

國家“863”項(xiàng)目(2009AA061603)

* 責(zé)任作者, 副研究員, renmingzhong@scies.org

李艷靜(1985-),女,河南內(nèi)黃縣人,碩士,主要從事垃圾焚燒二排放特征研究.發(fā)表論文3篇.