【作者】 徐梦侠；

【导师】 严建华； 岑可法； 李晓东；

【作者基本信息】 浙江大学 ， 能源环境工程， 2009， 博士

【摘要】 近年来,垃圾焚烧技术凭借高温无害化、减容和减重的优点,在我国大陆经济发达地区得到了迅速的推广和应用。然而,城市生活垃圾焚烧厂兴建和长期运行可能带来的二次污染问题,尤其是二恶英排放的环境毒性及其健康危害已引起了社会的广泛关注。为了建立有效的措施控制二恶英的排放,亟需了解我国大陆城市生活垃圾焚烧厂周边二恶英的污染状况。本文以杭州某城市生活垃圾焚烧厂为研究对象,通过模拟计算(复杂工业源扩散模型和混合库模型)、环境监测和统计分析(因子分析和化学质量平衡分析)相结合的方法,对焚烧厂周边土壤、大气和潜在污染源二恶英污染水平和指纹特征、大气二恶英气固相分配规律、环境二恶英发生源解析以及焚烧厂周边居民二恶英环境暴露风险等进行了系统的研究,得到了如下主要结论：2006和2007年土壤二恶英总浓度(毒性当量)分别为54.1-285 ng kg-1 (0.39-5.04 ng I-TEQ kg-1)和73.6-377 ng kg-1 (0.60-6.38 ng I-TEQ kg-1); 2006-2007年土壤总浓度和毒性当量分别增加了30%和31%(中位值),其中有3个采样点的增幅超过1 ngI-TEQ kg-1。土壤同系物、有毒异构体浓度和毒性当量指纹特征较为相似,OCDD是最主要的同系物,且呋喃浓度随氯代数的增加而减少；除OCDD外,浓度贡献较大的有毒异构体包括1,2,3,4,6,7,8-HpCDD、1,2,3,4,6,7,8-HpCDF和OCDF; 2,3,4,7,8-PeCDF是毒性当量的最大贡献者(2006和2007年平均分别为31%和30%)。大气二恶英总浓度(毒性当量)变化范围为3.96-164 pg m-3 (0.059-3.03 pg I-TEQm-3),其浓度的空间分布与土壤动态变化趋势相一致；几乎所有大气样品呈现出TCDF占主导地位(20-41%)的同系物指纹特征,其特点是同系物浓度随氯代数的增加而减少(除了OCDD)；和土壤相似,2,3,4,7,8-PeCDF是毒性当量贡献最大的有毒异构体(30-53%)；相反,大气有毒异构体浓度指纹特征不尽相同,主要贡献者为OCDD. OCDF和1,2,3,4,6,7,8-HpCDF中的一个,并随时间和空间而异。2007年生活垃圾焚烧厂烟气二恶英排放浓度相对较低(0.083-0.795 ng I-TEQNm-3),而离散的排放源浓度较高,如以木材为燃料的开水锅炉烟气(HWB-W)和露天布料焚烧(OB-C)下风向空气二恶英浓度分别为1.95 ng I-TEQ Nm-3和6.14 pgI-TEQ m-3;排放源同系物指纹特征较为相似,即二恶英和呋喃浓度比小于1；相反,排放源有毒异构体浓度指纹特征各异,如HWB-W以2,3,4,7,8-PeCDF为主,而OB-C则以OCDD、1,2,3,4,6,7,8-HpCDF和OCDF为主；尽管如此,2,3,4,7,8-PeCDF是大部分排放源毒性当量的主要贡献者(49-75%)。大气二恶英固相百分比(φ)随氯代数目增加和环境温度降低而增加,全年平均变化范围为：C14DD/Fs (37-56%), Cl5-6DD/Fs (58-86%)和Cl7-8DD/Fs (86-98%);总体上Junge-Pankow (PLo)吸附模型和Harner-Bidleman (Koa)吸收模型预测值和观测的φ(除了冬季)匹配度较好,对于PLO模型,采用气相色谱保留指数(GC-RIs)方法得到的匹配度要优于熵值法,而基于GC-RIs方法的Koa模型的匹配度要优于对应的PLO模型；冬季高总悬浮颗粒物浓度下φ的低匹配度很大程度上归结于低温下化合物气固相交换过程延缓引起的非平衡状态,而非滤膜表面的气相吸附误差。因子分析表明露天垃圾焚烧、开水锅炉烟气和机动车尾气是引起土壤二恶英动态变化和大气二恶英污染的主要来源,相反,生活垃圾焚烧厂烟气排放对周边环境的影响较小,四者对大气二恶英毒性当量的平均贡献率(基于化学质量平衡模型)分别为63%、18%、12%和7%；复杂工业源扩散模型和混合库模型的模拟结果表明生活垃圾焚烧厂烟气排放对大气二恶英毒性当量的平均贡献率为2%,对周边0-250、500-750和1500-3000 m范围内土壤二恶英毒性当量增量的平均贡献率分别为64%、8.5%和1.1%；对于二恶英排放达到国家标准(1 ng I-TEQ Nm-3)的现代化生活垃圾焚烧厂,其长期运行对周边土壤,特别是远离焚烧厂区域(d>1 km)的影响是有限的。生活垃圾焚烧厂周边儿童和成人的环境暴露量范围为3.45×10-5到1.77×10-4ngI-TEQ kg-1 day-1和2.61×10-3到1.35×10-2 ng I-TEQ kg-1 day-1;呼吸是环境暴露的主要途径,分别占儿童和成人暴露量的87-99%和88-99%；儿童和成人的环境暴露非致癌风险指数范围分别是8.63-44.3×10-3和6.53-33.8×10-3,致癌风险指数范围分别是5.17×10-6到2.65×10-5和3.91×10-6到2.02×10-5,其中来自生活垃圾焚烧厂烟气排放的贡献率仅为7%。更多还原

【Abstract】 Recently, due to the advantages of high-temperature detoxification, significant volume and mass reduction of municipal solid waste, the incineration technology has been booming and applied in developed regions in China’s mainland. However, the construction and operation of municipal solid waste (MSW) incineration plant has stirred public concerns due to the potential secondary pollution from the facility, especially the environmental toxics and associated adverse health effects of the emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). In order to establish effective countermeasures to control the emissions of PCDD/Fs, it is urgent to understand the pollution status of PCDD/Fs around the MSW incineration plant. In this study, by combination of the modeling procedures, i.e., Industrial Source Complex Short Term Version 3 (ISCST3) model and Reservoir Mixing (RM) model, environmental monitoring and statistical analysis (Factor Analysis and Chemical Mass Balance Analysis), we investigated the levels and profiles of PCDD/Fs in soil, air and potential sources around an MSW incineration plant in Hangzhou, the gas/particle partitioning of PCDD/Fs in ambient air, the source identification of PCDD/Fs in environmental media and the environmental exposure risk of PCDD/Fs for residents living around the facility.The total concentration (I-TEQ value) of soils in 2006 and 2007 ranged from 54.1 to 285 ng kg-1 (0.39 to 5.04 ng I-TEQ kg-1) and from 73.6 to 377 ng kg-1 (0.60 to 6.38 ng I-TEQ kg-1), respectively. On the other hand, the temporal variations (2006-2007) of the total concentration and I-TEQ value in soils increased by 30% and 31%(median value), respectively, with three sampling sites exceeding 1 ng I-TEQ kg-1. Similar homologue, congener concentration and congener I-TEQ profiles were found among the soils. As for homologues, OCDD was the dominant contributor and the concentrations of PCDF homologues decreased with increasing level of chlorination. With respect to congener concentration profile,1,2,3,4,6,7,8-HpCDD,1,2,3,4,6,7,8-HpCDF and OCDF were the main contributor besides OCDD. With regard to congener I-TEQ fingerprint,2,3,4,7,8-PeCDF was the dominant contributor, accounting for 31% and 30%(mean value) in 2006 and 2007, respectively.The atmospheric PCDD/F concentration ranged from 3.96 to 164 pg m-3 (0.059 to 3.03 pg I-TEQ m-3). The spatial distribution of atmospheric PCDD/F levels was in line with those observed in soils (temporal variations). Almost all ambient air samples showed a TCDF-dominant (20-41%) homologue pattern, characterized by decreasing concentrations with increasing levels of chlorination (except for OCDD). Similar to soils,2,3,4,7,8-PeCDF (30-53%) was the dominant contributor of I-TEQs to ambient air. By contrast, the dominant congener in terms of concentration profiles showed temporal and spatial variations among OCDD, OCDF and 1,2,3,4,6,7,8-HpCDF.The PCDD/F emission levels of the MSW incineration plant in 2007 were relatively low (0.083-0.795 ng I-TEQ Nm"3). By contrast, the diffuse emission sources showed high dioxin levels. For instance, the concentrations of flue gas from wood-fueled hot water boiler (HWB-W) and the ambient air leeward of open burning of cloth (OB-C) were 1.95 ng I-TEQ Nm-3 and 6.14 pg I-TEQ m-3, respectively. The homologue profiles of emission sources were similar, with PCDDs/PCDFs ratio less than 1. In comparison, the congener concentration patterns were distinct from each other, e.g., the HWB-W was dominated by 2,3,4,7,8-PeCDF whereas OB-C was dominated by OCDD,1,2,3,4,6,7,8-HpCDF and OCDF. Nevertheless,2,3,4,7,8-PeCDF was the dominant contributor to I-TEQ (49-75%) for most emission sources.The fraction of particle-bound PCDD/Fs (φ) increases as the chlorination level increases and/or the ambient temperature decrease, and the annual averaged values were as follows:C14DD/Fs (37-56%), Cl5-6DD/Fs (58-86%) and Cl7-8DD/Fs (86-98%). Generally, good agreements were obtained (except for winter) between measuredφand theoretical estimates of both the Junge-Pankow (PLo) adsorption model and the Harner-Bidleman (Koa) absorption model. Models utilizing PLo estimates, derived from gas chromatographic retention indices (GC-RIs), were more accurate than that of entropy-based. Moreover, the Koa-based model using the GC-RIs approach performed better than that of PLo-based. The disagreement found between the modeled and observed values during winter under high concentration of total suspend particles was more attributed to the non-equilibrium partitioning of PCDD/Fs that had slowed down the exchange between gaseous and particulate fractions than the gas adsorption artifact of filter.The results from a congener-specific factor analysis revealed that the emissions from the open burning of wastes, hot water boilers and motor vehicles were the major sources that accounted for the temporal variations of PCDD/Fs in soils and atmospheric PCDD/F pollution. By contrast, the impact of emissions from the MSW incineration plant was limited. The average contributories to atmospheric I-TEQ values from the above mentioned four emission sources (based on CMB model) were 63%,18%,12%and 7%, respectively. On the other hand, the results from ISCST3 and RM modeling indicated that the average contribution of emissions from the MSW incineration plant to atmospheric levels and soil temporal variations (I-TEQ) in three sub-regions, i.e., within a radius of 250,500-750 and 1500-3000 m from the stack were 2%,64%,8.5% and 1.1%, respectively. For a modern MSW incineration plant that meets the national PCDD/F emission standard, i.e.,1 ng I-TEQ Nm-3, the impact of a long-term operation of the facility on surrounding soils, especially those far away(d>1km) from the facility, is limited.The environmental exposure to PCDD/Fs ranged from 3.45×10-5 to 1.77×10-4 ng I-TEQ kg-1 day-1 and 2.61×10-5 to 1.35×10-4 ng I-TEQ kg-1 day-1 for children and adults living in the vicinity of the MSW incineration plant. Inhalation is the dominant pathway, accounting for 87-99% and 88-99% of environmental exposure for children and adults, respectively. The non-carcinogenic and carcinogenic risk of environmental exposure was 8.66-44.3×10-3 and 5.17-26.5×10-6 for children and 65.3-33.8×10-3 and 3.91-20.2×10-6 for adults, respectively, among which only 7% was from the emissions of the MSW incineration plant.更多还原