静态扬尘对呼吸途径健康风险评价的影响研究

发布时间：2018-12-22 09:00

【摘要】：以湖南省中部某废弃化工厂区和沙场堆场区对研究对象,通过布点和采集土壤样品,测定重金属(Cd、As、Cr、Ni和Hg)含量,结合空气动力学气固两相理论,重点对露天污染场地建立堆场PM10浓度预测模型,并纳入暴露评估模型和健康风险评估模型,研究静态扬尘对暴露评估和健康风险评价的影响。因此,本文为厂区和沙场堆场区及周边地区土壤污染预防、防治以及治理提供理论基础,为健康风险评价提供一种简便且符合实际情况的参数确定方法。得出了以下几个主要结论:(1)污染场地表层土壤中重金属含量及垂直分布特征:5种重金属的平均含量除Cr和Ni,其余3种均超出国家土壤环境质量二级标准(GB15618-1995)和湖南省土壤背景值。As的含量最高,Cd的含量次之,样品超标率在58.54%以上,Cd、As和Hg的全距及变异系数均比较大。厂区土壤中Cr、As、Hg的含量基本上高于同一深度沙场堆场区的含量,在0~2.0 m深度,沙场堆场区和厂区土壤中多数重金属(除了Ni)的垂直分布表现出从表层向下降低的趋势,而有些重金属沿垂直方向增加或含量变化不大。(2)近地面的PM10浓度受气象因素(如风向、风速)影响较大,夏季受S、SSE、SSW风影响,且平均风速最大,厂区北方居住区和商业区PM10浓度最大达到0.30 mg/m3,全年受NW和NNW风的影响,旅游区PM10浓度超过0.15 mg/m3。PM10浓度在厂区和沙场堆场区及其附近较大,且随着扩散面积的增大而迅速降低。(3)基于人体特征、时间—活动行为和摄入率的呼吸途径暴露评估结果表明:每日暴露量(ADI)与PM10浓度呈正比,与扩散面积呈反比,在污染源区域内及附近暴露人群的每日暴露量都迅速增大,人群易受到污染物的危害。由于理特性、行为方式、生活规律等方面的原因,儿童的暴露剂量高于成年人,使得儿童更容易受到污染物的危害。(4)重金属的单项非致癌危害商(HQ)、总危害指数(HI)和终生超额致癌风险(R)与PM10浓度呈线性增加趋势。污染源区内及附近受风力、风速等的影响,PM10浓度高,对暴露人群健康威胁最大。Cd和As存在非致癌风险,这两者对总危害指数(HI)的贡献率较大,分别达到56.73%和37.78%以上。当PM10浓度超过0.125 mg/m3时,HQ(Cd)1;当PM10浓度超过0.175 mg/m3时,HQ(As)1。Cd、Cr、As具有致癌风险,当PM10浓度0.050 mg/m3时,3种重金属的R10-6,且致癌风险水平AsCrCd。儿童的非致癌风险和致癌风险都高于成年人。Ni对成年人致癌风险水平较低,而对于儿童,当PM10达到0.400 mg/m3时,R(Ni)超过风险阈值,具有致癌风险。(5)两类暴露人群的Cd、As、Cr、Ni、Hg的HQ和R的概率分布十分接近,Cd和As的HQ在安全阈值内的概率分别为69%和61%,其余3种重金属概率分布100%都在风险阈值之内。4种无阈重金属致癌风险值都有超过阈值(10-6)的概率分布,可靠程度分别达到53%、84%、96%、4%。重金属浓度和PM10浓度是影响Cd、As、Cr、Ni和Hg通过呼吸途径进入人体单位体重的日均暴露剂量、非致癌风险水平和终生致癌风险水平大小的主要因素。因此,为了防止该区域风险事故的发生,因对污染源区的土壤中重金属进行控制和修复。(6)在风险表征结果基础上,通过反演计算得出污染场地土壤重金属Cd、Cr、As和N i的风险控制值分别为2.13 mg/kg、0.046 mg/kg、0.89 mg/kg和10.15mg/kg。
[Abstract]:The contents of heavy metals (Cd, As, Cr, Ni and Hg) were determined by distributing and collecting soil samples in a waste chemical plant area and a sand yard area in the central part of Hunan Province, and the two-phase theory of aerodynamics and gas-solid was combined. The model of PM10 concentration of storage yard is set up for open-air pollution site, and the model of exposure assessment and health risk assessment are included to study the effect of static dust on exposure assessment and health risk assessment. Therefore, this paper provides the theoretical basis for the prevention, treatment and treatment of the soil pollution in the plant area and the area of the sand yard and the surrounding area, and provides a simple and practical parameter determination method for the health risk evaluation. The main conclusions are as follows: (1) The heavy metal content and vertical distribution in the surface soil of the contaminated site: the average content of the five heavy metals is the same as that of Cr and Ni, and the remaining 3 species are in excess of the national soil environmental quality secondary standard (GB15618-1995) and the soil background value of Hunan Province. As the content of As is the highest, the content of Cd is the second, the overproof rate of the sample is over 58. 54%, and the full-distance and coefficient of variation of Cd, As and Hg are all larger. The content of Cr, As and Hg in the soil of the plant area is higher than that of the same depth sand yard area, and the vertical distribution of most heavy metals (in addition to Ni) in the soil of the sand yard and the plant area shows a downward downward trend from the surface layer. while some heavy metals increase in the vertical direction or the content change is not large. (2) The PM10 concentration of the near ground is affected by the meteorological factors (such as wind direction and wind speed), and is affected by the S, SSE and SSW wind in the summer, and the average wind speed is the largest. The concentration of PM10 in the northern and commercial areas of the plant is at the maximum of 0.30mg/ m3, and the whole year is affected by the NW and NNW wind. The concentration of PM10 in the tourist area is more than 0. 15 mg/ m3. The concentration of PM10 is larger in the plant area and the area of the sand yard and its vicinity, and the concentration of PM10 decreases rapidly with the increase of the diffusion area. (3) The results showed that the daily exposure (ADI) was proportional to the concentration of PM10, inversely proportional to the diffusion area, and the daily exposure to the exposed population in the area of the pollution source and the nearby exposed population increased rapidly. The population is vulnerable to contaminants. The exposure dose of the child is higher than that of the adult, which makes the child more vulnerable to the contaminants due to the reasons of the physical characteristics, the behavior pattern, the life rule, and the like. (4) The single non-carcinogenic hazard quotient (HQ), the total hazard index (HI) and the life-long excess carcinogenic risk (R) of heavy metals are linearly increasing with the concentration of PM10. The concentration of PM10 is high, and the health threat to exposed population is the most. The non-carcinogenic risk of Cd and As, the contribution rate of the two to the total hazard index (HI) was 56. 73% and 37. 78%, respectively. When the concentration of PM10 exceeds 0.125 mg/ m3, HQ (Cd) 1; when the concentration of PM10 exceeds 0.175 mg/ m3, HQ (As) 1. Cd, Cr, As has a carcinogenic risk, and when the concentration of PM10 is 0.050 mg/ m3, R10-6 of three heavy metals and the level of cancer risk AsCrCd. The non-carcinogenic and carcinogenic risk of children is higher than that of adults. Ni has a low level of cancer risk for adults, and for children, when PM10 reaches 0.400 mg/ m3, R (Ni) exceeds the risk threshold and has an oncogenic risk. (5) The probability distribution of HQ and R of Cd, As, Cr, Ni and Hg in two types of exposed population is very close, and the probability of the HQ of Cd and As in the safety threshold is 69% and 61%, respectively. The probability distribution and reliability of the four non-threshold heavy metal carcinogenic risk values were respectively 53%, 84%, 96% and 4%, respectively. The concentration of heavy metals and the concentration of PM10 are the main factors that affect the daily exposure dose, non-carcinogenic risk level and the level of life-long oncogenic risk of Cd, As, Cr, Ni and Hg in the body weight of human body through the breathing path. Therefore, in order to prevent the occurrence of the regional risk accident, the heavy metal in the soil of the pollution source area is controlled and repaired. (6) The risk control values of the heavy metal Cd, Cr, As and Ni in the contaminated site were 2.13 mg/ kg, 0.046 mg/ kg, 0.89 mg/ kg and 10. 15mg/ kg, respectively, on the basis of the risk characterization results.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X823;X513

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