【作者】 高阳；

【导师】 吴水平；

【作者基本信息】 厦门大学 ， 环境科学， 2022， 硕士

【摘要】 变电站是电力传输系统的核心环节,承载有转换电流电压、接受及分配电能等重要作用。为保证设备的正常运行,变电站内存有大量变压器油、电缆等易燃材料,一旦发生火灾,除了造成严重经济损失外,火灾现场残留物及燃烧过程产生的有害物质也会通过大气作用进入到周围环境介质中,最终进入人体造成潜在的健康威胁。目前对变电站火灾残留物中有害物质如多环芳烃(Polycyclic Aromatic Hydrocarbons,PAHs)的污染特征研究较少,对其导致的次生环境问题研究仍处于起步阶段。基于此,本研究开展了变电站电气设备火灾排放烟尘、消防废水及土壤中PAHs的污染特征分析,并基于火灾情景分析对其烟羽扩散与沉降进行模拟,最后对其可能导致的环境健康风险进行评估,可为进一步环境治理与修复提供参考。取得的主要结果如下:(1)搭建燃烧模拟平台,确定变电站可燃物燃烧生成的烟尘及负载PAHs排放因子,为烟羽扩散模型的建立提供源强参数。变压器油、电缆绝缘护套和油浸绝缘纸板三种可燃物稳定状态下的烟尘排放因子均值依次为29.7±2.3 mg/g、55.0±3.0mg/g 和 3.0±0.2mg/g;ΣPAHs 排放因子依次为 148.1±6.8 μg/g、41.4±11.3μg/g和0.7±0.1μg/g。排放因子差异性受可燃物自身结构、燃烧方式以及燃烧条件等因素影响,变压器油燃烧时出现轰燃,有利于PAHs的生成。三种可燃物烟尘中PAHs的谱分布接近,均表现为4环的荧蒽(Flua)与芘(Pyr)占较大贡献(30%～43%)。(2)以厦门东园110 kV变电站作为火灾模拟场景,基于WRF-CALPUFF扩散模型确定火灾烟羽扩散下风向沉降至土壤中的PAHs浓度。考虑到可燃物体量及PAHs排放因子差异性,以变压器油燃烧进行火灾情景构建。设定2020年1月21日、6月23日、9月11日、10月21日对应的4种气象条件作为火灾发生气象场。受风速及下风向下垫面影响,9月11日对应气象条件下(风速为3.2 m/s,主导风向为西南风),下风向关注高度(2m)处最大烟尘颗粒浓度(3654.8μg/m3)及沉降通量(0.17 μg/m2/s)均高于其他气象条件。根据烟尘沉降量和负载PAHs浓度,计算其携带PAHs进入土壤中的浓度,表现为随距离增加,PAHs浓度值呈快速下降后保持稳定波动的趋势,二者之间满足二阶指数衰减(y=1.233e-x/0.719+1.203e-x/0.713+3.795×10-6;R2=0.998)。(3)根据全尺寸变压器火灾试验,确定火灾现场近距离土壤中PAHs污染特征。土壤中PAHs浓度表现出随距离的增加而缓慢下降的趋势(满足y=-0.308ln(x)+1.543;R2=0.813)。不同于变压器油,土壤中PAHs组成以菲(Phe)和蒽(Ant)为主(约占49%),ΣBaPeq均值为0.02±0.01 μg/g,低于农用地土壤BaP风险筛选值(0.55 μg/g)。紧靠变压器的采样站点,土壤中PAHs来源除火灾烟尘外还包括消防废水、可燃物燃烧残渣等。分析现场消防废水PAHs组成也以Phe和Ant占较大优势(64%);ΣBaPeq为0.03±0.04 ng/mL,远高于地表水BaP的含量阈值(0.0028 ng/mL),接近《污水综合排放标准》BaP最高允许排放值(0.03ng/mL)。另外,通过土壤淋滤实验,得到进入地下水的ΣPAHs总浓度为0.78±0.60 ng/mL,占烟尘颗粒中ΣPAHs浓度的比例为0.001%,低环芳烃的纵向迁移能力更强,水体中苊烯占到全部检出PAHs的一半以上。(4)建立变电站电气设备火灾残留物中PAHs的人体健康风险评估体系。设定火灾发生情景为风速3.2m/s,主导风向西南风,基于模型输出值、现场实测值与距离,采用OriginPro拟合得到土壤中PAHs浓度随距离变化的函数(y=3.143e-x/0.042+0.871e-x/0.109;R2=0.997)。进入土壤中的 PAHs 按照土壤残留 60.6%,进入蔬菜39.4%和渗入地下水0.001%进行分配,消防废水携带PAHs进入地表水环境按照浓度为0.0053 mg/L,进行变电站火灾残留物中PAHs的人体健康风险评估。得到PAHs不同暴露途径对健康风险的贡献率为:经口摄入>皮肤接触>呼吸摄入;成人的致癌风险.(CR)和非致癌风险(HI)均大于儿童;风险值与距离之间满足指数衰减规律,对成人而言,火灾原点处CR为2.3×10-4,在23～160 m范围内,风险值处于[10-6,10-4],1000 m后降为10-18;儿童风险范围相应缩小,在10 m和143 m处分别达到10-4和10-6。非致癌风险整体小于0.01,可忽略不计。基于毒性当量评价(ΣBaPeq),在距离火灾原点106m后,土壤、食物及地下水中ΣBaPeq均低于国家标准。综合以上三种评估结果,确定火灾106m范围内土壤需重点管控,160m之后风险可接受。整体评价流程和方法可用于后续真实变电站电气设备火灾残留物PAHs人体健康风险评价。更多还原

【Abstract】 Substations are very important in the process of power transmission,carrying the functions of converting,receiving and distributing current and voltage.In the event of a fire,in addition to economic losses,a large number of toxic and harmful substances were released into the environment,causing potential human health threats.However,few studies had been done on the formation of polycyclic aromatic hydrocarbons(PAHs)from substation fire residues;the research on related secondary environmental issues was also in its infancy.Therefore,this study analyzed the pollution characteristics of PAHs in smoke,fire-fighting wastewater and soil from substation fires;then the smoke plume diffusion and settlement were simulated based on the fire scenario analysis;Finally,the environmental health risks that it may cause were evaluated,which could provide reference for further environmental governance.The main conclutions were as follows:(1)To provide parameters for the the diffusion model,the emission factors of smock and the PAHs in the substation fire were determined by building a combustion simulation platform.The mean values of smock emission factors of transformer oil,cable insulation sheath and oil-impregnated insulating board were 29.7±2.3 mg/g、55.0±3.0 mg/g and 3.0±0.2 mg/g;ΣPAHs emission factors were 148.1±6.8 μg/g、41.4±11.3 μg/g and 0.7±0.1 μg/g.The difference of emission factors was affected by the structure of combustibles,combustion methods and combustion conditions,etc.The violent combustion of transformer oil was conducive to the generation of PAHs.Spectral distribution of PAHs in the three kinds of combustible soot were similar,and the 4-ring fluoranthene(Flua)and pyrene(Pyr)accounted for a larger contribution(30%～43%).(2)Taking Xiamen Dongyuan 110 kV substation as an example,the fire plume diffusion process was determined based on the WRF-CALPUFF diffusion model.Transformer oil combustion was selected to construct a fire scenario.The four weather conditions corresponding to January 21,June 23,September 11,and October 21,2020 were used as the fire occurrence weather field.Among them,affected by the wind speed and the underlying surface,on September 11,the maximum particle concentration(3654.8 μg/m3)and deposition flux(0.17 μg/m2/s)in the downwind direction were the highest(wind speed:3.2 m/s;wind direction:southwest wind).The concentration of PAHs entering the soil was calculated according to the sedimentation flux,satisfying y=1.233e-x/0.719+1.203e-x/0.713+3.795×10-6.With increasing distance,the concentration of PAHs decreases rapidly and then maintains a stable fluctuation.(3)According to the full-scale transformer fire test,the characteristics of PAHs pollution in the soil near the fire site were determined.The concentration of PAHs in soil decreased slowly with increasing distance(y=-0.3081n(x)+1.543;R2=0.813).Different from transformer oil,PAHs in soil were mainly composed of 3-ring phenanthrene(Phe)and anthracene(Ant)(49%);EBaPeq is 0.02±0.01 μg/g,which is lower than the BaP risk screening value(0.55 μg/g).In addition to fire smoke,the sources of PAHs in soil included fire-fighting wastewater and combustible residues.Analyzing fire-fighting wastewater,the composition of PAHs was similar to soil;TheΣBaPeq was 0.03±0.04 ng/mL,which was much higher than the BaP content threshold in surface water(0.0028 ng/mL),and was close to the maximum allowable discharge value of BaP in the national standard.Meanwhile,the soil leaching experiment showed that ΣPAHs entering the groundwater was 0.78±0.60 ng/mL,accounting for 0.001%of the ΣPAHs in the smock particles.The longitudinal migration ability of low-ring aromatic hydrocarbons was stronger(acenaphthylene accounted for more than half).(4)Finally,a human health risk assessment system for PAHs in electrical equipment fire residues was established.The fire occurrence scenario was set as the wind speed of 3.2 m/s,southwest wind.Based on the output value of WRF-CALPUFF and the measured value in the field,the relationship between the concentration of PAHs in soil and distance was obtained by fitting with OriginPro(y=3.143e-x/0.042+0.871ex/0.109).The PAHs entering the soil were distributed according to the soil residue 60.6%,the vegetable 39.4%and the groundwater 0.001%;the concentration of the PAHs entering the surface water is calculated as 0.0053 mg/L.The health risks of the PAHs under the different exposure routes were as follows:oral intake>skin contact>respiratory intake.The carcinogenic risk(CR)and non-carcinogenic risk(HI)of adults were greater than those of children.The relationship between the risk value and thedistance accords with the exponential decay law.For adults,the CR value at the fire spot was 2.3×10-4,decreased to 10-4 at 23 m,10-6 at 160 m and 10-18 at 1000 m.For children,the risk value of CR was 10-4 and 10-6 at 10 m and 143 m,respectively.HI was very low(<0.01)and negligible.According to the total toxic equivalent(ΣBaPeq),the values in soil,food,and groundwater werelower than the national standards at a distance larger than 106 m and after fire treatment techniques should be carried out to reduce the environmental risk.The established evaluation procedure can be used for environmental risk assessment of PAHs in electrical equipment fire residue in electrical substation.更多还原