RCEES OpenIR  > 环境水质学国家重点实验室
给水管网输配过程金属元素的累积释放风险评价
刘泉利
Subtype博士后
Thesis Advisor石宝友
2019-07
Degree Grantor中国科学院生态环境研究中心
Place of Conferral北京
Degree Name理学
Degree Discipline环境科学与工程
Keyword金属 元素 管网 输配过程 Drinking Water Distribution Systems r Isk Assessment Morphology Mobilization 沉积物 特征 风险评价 迁移转化 Metal
Abstract

        饮用水安全关系到人的 身体健康 和 社会稳定,是 环境科学与工程领域的一个重要研究方向 。 同水源保护、水厂处理一样, 管网输配 过程 是饮用水安全保障的一个关键环节。 给水管网内壁普遍存在着 类型 多样 、组成复杂的 沉积物 。 管网沉积物的存在 不仅直接导致 管网输水能力 的 下降 ,还会影响供水管网 水质 的化学 和生物 稳定性,造成用户端水质 下降 甚至 有时 会 引起 红水 、 黑水 等 现象可能 存在健康风险 。
        本研究以给水管网输配过程中 金属 元素的累积 释放风险 评估 为 主题 在系统 分析管网沉积物 金属 元素污染 特征及赋存形态的基础 上 ,借鉴 在河流、湖泊水体沉积物重金属生态风险评价 领域 应用广泛的基于重金属浓度的一致性沉积物质量基准法( CBSQGs 、 基于重金属赋存形态的风险评估指数法( RAC 及 单个污染指数( ICF )、综合污染指数 GCF )等风险评价方法 开展 了给水管网 重金属风险评估 探讨 了 关键水质参数变化对管网沉积物 金属 元素稳定性的影响及其再释放 迁移的风险 ,并 通过典型案例 研究 了 实际 管网 输配水过程中 金属 元素在沉积物中 的累积 释放 风险 。 取得的 主要 研究 结果 如下:
        (1) 通过对集中供水的北方某城市管网中的沉积物进行调研发现, 管网沉积物中富集 的 金属 元素 种类较多, 硬质 管垢与疏松沉积物中含量最高的 金属 元素为 Fe 其次为 Al 、 Mn 和 Ba ,同时含有 多种 微量重金属 。管网沉积物中 金属 元素 的赋存形态以残渣态为主,部分 Cu 、 Mn 、 Pb 、 Zn 、 Co 和 Ba 以 Fe Mn 氧化物的形式存在。 硬质 管垢与疏松沉积物中的 13 种 金属 元素 的形态分级特征差异较小。 形貌与比表面积分析结果表明 无论是 硬质 管垢还是疏松沉积物,都具有明显的有利于吸附和容纳污染物的多孔结构( 比表面积的 最大值为 52.94 m 2 /g高于天然吸附剂)。 元素组成与晶体结构分析 结果 表明 沉积物 样品中含有丰富的 具有 吸 附重金属 能力 的物质,如 Fe 3 O 4 。
       (2) ICF 评估发现 疏松沉积物中 Cu 的 ICF 值均较高 ,高于 I CF 评价标准高风险基准值 6 ,具有很高的生态风险 。所有样品中的 As 、 V 和 Co 的 生态 风险较低,而 Cd 、 Cr 、 Pb 和 Ni 等无机污染物具有中等风险。 GCF 评估 结果表明:大部分采样点 的 GCF 值大于 12 ,存在较高的生态风险,最高的 GCF 值达到 101.8远高于 GCF 评估 方法 的高风险基准值( 24 。 RAC 评估 结果表明 硬质管垢 与疏松沉积物的高风险性均与 Cd 相关, 大部分采样点 Cd 的 RAC 值 大于 30 ,达到高风险水平。 Ba 在 硬质管 垢 样品中具有中等风险,而在疏松沉积物 具有 较 高风险 。 CBSQGs 评估结果表明 疏松沉积物 中重金属的风险高于 硬质管垢 样品,Ba 在所有重金属中的 生态 风险最高 。
        (3 )探讨了沉积物样品 对 典型重金属的吸附能力,发现沉积物样品对 Pb 2+ 、Cd 2+ 、 Cr 6+ 、 Ba 2+ 、 Cu 2+ 和 Zn 2+ 的最大吸附量分别达到 18.2 、 34.9 、 94.5 、 255.4 、699 .0 、 668.1 μg/g 。 当水体 pH 值从 6 变化到 10 时,沉积物样品中重金属释放 趋势 具有相同的 变化 规律 。 沉积物样品中 Cu 、 Cr 、 As 、 Pb 和 Cd 的最大释放量分别为 0.56 、 0.51 、 1.82 、 0.84 和 0.72 μ g/g 。虽然重金属的释放量较低,但 释放过程 中 重金属 的 形态分布 特征 发生了变化,以不稳定形态存在的比例增加, 水质条件变化时 更 易发生释放 。此外,腐殖酸的存在加速了样品中有机质的溶解。这进一步证明,沉积物存在形式不稳定,易受水质条件变化的影响,应予以重视。
        (4) 针对 输配水管网长度较长、人口分散、管网水质 问题 突出的城乡一体化供水模式下农村用户端水质研究 发现, 农村地区龙头水存在 较严重的 二次污染现象,输配水过程中 金属 元素有明显的累积 释放 现象 ,研究区域龙头水 中的主要污染物为 F e 、 Al 和 Ba 。对龙头水残余铝形态、随距离变化规律 的 研究表明长距离输水易造成颗粒铝在管网输配过程中的累积,并且在水力扰动下易发生释放,引起龙头水总铝与浊度升高。 采用美国环境保护署( USEPA )推荐的危害 熵值( HQ )和致癌风险指数 CR )模型对龙头水 金属 元素的健康风险进行评价结果表明 Al 、 Fe 、 Mn 、 Zn 、 Cu 、 Ba (非致癌金属)和 Cr 、 As (致癌金属 8种 金属 元素 对当地居民的非致癌风险可以忽略不计,但输配水过程中 金属 的累积效应不容忽视。 As 在研究区域的致癌风险较高,对儿童的潜在 健 康 风险更大。
 

Other Abstract

        Safe and high quality drinking water is an important part of human life.Drinking water saf ety is an important research direction in the field of environmental science and engineering. Like water source protection and water plant treatment, drinking water distribution system is a key link of drinking water safety. There are various types of sedi ments in the pipe network. The presence of sediment s in the pipe network not only directly reduces the water delivery capac ity, but also affects the chemical and biological stability of the water quality, resulting in the decline of water quality at the ta p water , and even sometimes causes problems such as "red water","black water" and other events
         This work mainly focused on the accumulation, speciation and risk assessment of metals found in pipe scales and loose deposits. Consensus based sediment quality guidelines (CBSQGs) CBSQGs), risk assessment code (RAC) and global contamination factor (GCF) were adopted for the potential heal th risk assessment of contaminants. The risk assessment method ology and index system of heavy metals in water supply network are esta blished. The objective of this study i s to evaluate the pollutant enrichment capacity of pipe scale and to identify speciat ion changes in heavy metals under variations in water quality. The accumulation/release risk of metals in pipe scales and loose depos its during drinking water distribution system was studied through typical cases. To provide theoretical basis and technical support for drinking water safety assurance based on waterplant pipe network coordination. The main conclusions are as follows:
        (1)Through the investigation of the pipe scales and loose deposits in the pipe network, it wa s found that there were many kind s of metals enriched in the pipe network sediments. The metals with the highest content in pipe scales and loose deposits were Fe, fo llowed by Al, Mn and Ba, and some trace heavy metals. The Tessier sequential extraction method was used to study the specia tion distribution of metals in fourteen samples (six pipe scale samples, eight loose deposit samples)collected from real drinking wa ter distribution systems. Mn, Cu, Pb, Zn, Ni, Co and Ba in the samples were mainly associated with the Fe Mn oxides fractio n, which indicated Fe Mn oxides might play an important role in the accumulation and release of these metals . Fe, Al, As, Cr, V and C d mainly existed in the residual fraction, which indicated their low mobility. Morphology and surface areas analytical resu lts showed that the pipe scale samples have porous structures, and the resulting, relatively large,specific surface area (maximum wa s 52.94 m 2 /g, higher than natural adsorbents) might result in the ability of pipe scale samples to adsorb contaminants. XRD results also showed that pipe scale samples were rich in substances with heavy metal adsorption capacities, such as Fe 3 O 4
        (2)The I CF evaluation found that Cu in loose deposits had a higher ICF value 6), indicating a high ecological risk. The ecologica l risks of As, V and Co in all samples were relatively low, while heavy metals such As Cd, Cr, Pb and Ni presented moderate risks. GC F evaluation results showed that GCF value of most sampling points was greater than 12, which presented a high ecological r isk. The highest GCF value reached 101.8, which was much higher than the high risk baseline value (24)assessed by GCF. The RAC evaluation results showed that the high risk of pipe scales and loose depos its was related to Cd, and the RAC value of Cd in mos t sampling sites was greater than 30, reaching the high risk level. Ba was of moderate risk in pipe scale samples and of high risk in loose deposits. CBSQGs evaluation results showed that the risk of hea vy metals in loose deposits was higher than that in p ipe scale samples, and Ba was the highest risk among all heavy metals
           (3)The maximum adsorption capacity of Pb 2+2+, Cd 2+2+, Cr 6+6+, Ba 2+2+, Cu 2+ and Zn 2+ reached 18.2, 34.9, 94.5, 255.4, 699 and 668.1 μg/g, r espectively. When the pH changed from 6 to 10, the ch anges in amounts of released heavy metals were consistent under different pH conditions, and there was no significant difference. The maximum release amounts of Cu, Cr, As, Pb, Cd were 0.56, 0.51, 1.82, 0.84 and 0.72 μg/g, respectively, under pH=8. Althoug h the amounts were small, the speciation distributions of heavy metals changed, and the proportion of unstable fractions increased, which aggravated the release risk of pipe scale samples. The presence of humic acid a ccelerated the dissolution of organic m atter in the pipe scale samples,which might be combined with metals. This further proved that the pipe scales were unstable and susceptible to water quality conditions, which should be taken seriously.
            (4 ) The water quality of rural users under the mode o f integrated urban and rural water supply wa s selected as the research object. The change of eight metals (Al, Fe, Mn, Zn, Cu, Ba, Cr, As) were investigated from the finished water (water treated by drinking water tre atment process before entering distribu tion process) to tap water of 10 water treatment plants in 5 cities of eastern China. The metal concentration in the tap water was mostly higher than the finished water and almost no samples remained constant with fin ished water indicating that the water q uality could deteriorate during DWDS in the rural areas. Both the HQ values and HI values for all studied elements were far below 1, indicating there were negligible non carcinogenic risks for inhabitants (adults and children) due to water intake. Carcinog enic risk values showed that As in studied areas was up to 1.94×10 4 and the value was higher than 1×10 4 .Trace amounts of As could accumulate in drinking water distribution system. There were obvious variations in t he heavy metals between finished water and tap water, and the accumulation and re release effect of metals in drinking water distribution system could not be ignored.

Pages86
Language中文
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/42291
Collection环境水质学国家重点实验室
Recommended Citation
GB/T 7714
刘泉利. 给水管网输配过程金属元素的累积释放风险评价[D]. 北京. 中国科学院生态环境研究中心,2019.
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