西安市大气降尘污染特征研究

发布时间：2018-01-02 04:28

本文关键词：西安市大气降尘污染特征研究　出处：《长安大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着我国工业化和城镇化的深入推进,人类活动使得城市区域的大气降尘污染问题日益突出。而城市范围内的大气干、湿沉降降尘,其产生的污染不仅仅局限于大气环境,同时也是城市地表径流的一个重要污染来源。研究大气降尘污染对改善城市环境空气质量和地表水环境质量均具有非常重要的意义。本文选择对西安市区不同功能区域大气降尘污染特征以及生态风险进行细致研究和讨论,以期揭示该地区降尘污染特征和变化规律,探明大气降尘对城市路面径流污染的贡献,对以后制定大气环境和水环境保护对策和污染防治措施提供科学依据。主要研究结论和结果如下:通过采集西安市常年累积的大气降尘样品,研究大气降尘污染特征、重金属的形态及其生物有效性、西安市大气降尘生态风险评价及重金属源解析等内容,得到以下结论:(1)西安市大气降尘中的总COD、淋溶COD、无机氮素以及金属元素元素的质量浓度变化较大,且在空间分布上极不均匀,除COD以外,它们的污染程度均随着功能区的洁净程度而不断减弱。降尘中的无机氮主要由氨氮和硝态氮这两种形态组成,氨态氮与硝态氮的比值普遍大于2;Cu、Pb、Zn这三种城市元素的浓度在工业区最高,Ni和Cd元素主要集中于工业、商业和居民文教区且各区的浓度变化不大,西安市大部分地区遭受Cd污染。(2)西安市大气降尘中Pb、Cr和Ni主要以残渣态形式存在,重金属比较稳定。Cu主要以残渣态和可氧化态为主,Zn主要以残渣态和酸溶态存在,降尘中的Cd酸溶态较高。由计算的生物有效性系数可知,Zn和Cd的生物有效性系数K均大于0.2,其可迁移部分、生物可利用部分高,对环境的影响较大。(3)西安市大气降尘中的Cu、Zn、Cr和Ni生态风险指数较小,生态危害等级低;其次,Pb和As生态风险等级为中等;Cd的生态风险指数远远高于其他重金属,其生态危害最为严重。由富集因子的计算结果亦可知,Cd在各功能区富集因子均大于20,在所有重金属中最高,富集程度较强。而Pb和Zn的富集因子在4-10之间,富集显著。(4)由主成分分析得出,Cu、Fe、Cr和Zn以上元素可能来源于金属冶炼、机械制造、汽车尾气排放以及轮胎、发动机等机械磨损;Cd、Pb以及As是由燃煤及工业生产因子贡献;Al、Ca、Ni则来自于地壳土壤和扬尘,属于自然来源。通过采集西安市2014年全年的大气降尘样品,对大气降尘量的时空分异特征和大气降尘污染的时空分异特征进行细致讨论,得到以下结论:(1)西安市各功能区在冬春两季降尘量超标严重;夏秋两季降尘相比参考标准增量也较大,污染比冬春两季稍弱。西安市大气降尘通量在不同季节有显著差异,在总体上表现出:冬季春季夏季秋季。而不同功能区降尘量也存在显著性差异,总体来看,降尘量在功能区的变化为:工业区商业区居民区旅游区。(2)西安市大气降尘中各形态氮素的浓度存在明显季节性差异,硝态氮在冬季氨氮浓度为全年最高,而对于氨氮的增加不太明显。西安市大气降尘中各金属元素在四个季度的质量浓度差异明显,主要表现为冬春两季高,夏秋两季较低,且夏秋两季含量差距很小。西安市不同功能区各形态氮素的浓度存在明显差异,且在不同季节内均表现出相似的分布特征。即:工业区商业区≈居民区旅游区。四个功能区的氨氮浓度占有绝对优势,说明西安市的无机氮沉降以氨态氮为主。(3)西安市大气降尘中金属元素在不同功能区的浓度分布有较大的差异。Cu、Pb、Zn、Cd在工业区的含量比其他功能区高出1.3-1.4倍,而As、Ba、Fe的浓度则比其他功能区低,除Cu、Pb、Ba外,商业区,居民区和旅游区各金属元素元素含量相对均匀。各金属元素的浓度从高到低依次为AlFeBaZnPbCrAsCuNiVCd,这与常年累积降尘中金属元素浓度的高低规律基本一致。
[Abstract]:Along with our country industrialization and further promote urbanization, human activities makes the city regional atmospheric dust pollution problems have become increasingly prominent. The city within the scope of the air dry, wet deposition of dust, the pollution is not limited to the atmospheric environment, but also an important source of pollution is also a city of surface runoff. Research on atmospheric dust the pollution is very important to improve air quality of city environment and surface water environment quality of Xi'an city. This paper chooses the atmosphere in different function areas of dust pollution characteristics and ecological risk of detailed research and discussion, in order to reveal the dust pollution and the variation characteristics of atmospheric dust on the City, proven pavement runoff pollution the contribution to provide a scientific basis for the future development of the atmospheric environment and water environment protection and pollution prevention measures. The main conclusions and results are as follows: through collecting Dust samples fall in Xi'an perennial accumulation of atmospheric dust pollution, feature reduction of atmospheric heavy metals, forms and bioavailability of dust, ecological risk assessment and source analysis of heavy metal contents such as reducing atmosphere of Xi'an City, obtained the following conclusions: (1) the total COD in dust in the atmosphere of Xi'an city and the change of inorganic nitrogen leaching COD the concentration of metal elements is large, and the spatial distribution is extremely uneven, except for COD, they are with the degree of pollution clean degree function area decrease. Reduction of inorganic nitrogen in dust is mainly composed of ammonia and nitrate in the two forms of composition, ratio of ammonia nitrogen and nitrate nitrogen generally more than 2; Cu, Pb, Zn concentration of these three elements in the highest city industrial zone, Ni and Cd elements are mainly concentrated in the industrial, commercial and residential district and cultural concentration changed little, Cd pollution suffered in most areas of Xi'an city. (2) the atmosphere of Xi'an City Dust in the Pb, Cr and Ni are mainly in residual form, the metal is relatively stable.Cu mainly in residual fraction and oxidizable fraction, Zn mainly in residual fraction and acid soluble, reducing Cd acid dust in soluble high. By biological effectiveness coefficient shows the calculation of the biological effectiveness coefficient K Zn and Cd are greater than 0.2, which can transfer part, the bioavailable fraction is high, a greater impact on the environment. (3) dust in the atmosphere of Xi'an city Cu, down Zn, Cr and Ni ecological risk index is small, ecological hazard level is low; secondly, Pb and As ecological risk level for secondary students; state risk index of Cd is much higher than other heavy metals, the most serious ecological hazard. By calculating the enrichment factor results also showed that Cd in each functional area of the enrichment factor is greater than 20, the highest among all heavy metals, the enrichment degree of strong. And the enrichment factors of Pb and Zn in 4-10, significantly enriched (4). By principal component analysis The Cu, Fe, Cr and Zn more elements may be derived from metal smelting, machinery manufacturing, automobile exhaust and tyre, engine and other mechanical wear; Cd, Pb and As are contributed by coal and industrial production factor; Al, Ca, Ni from the crust of soil and dust, which belongs to natural sources. By collecting Xi'an city in 2014 the year of the atmospheric dust samples, space-time dust on atmospheric variation characteristics of atmospheric dust pollution and the differentiation characteristics of the detailed discussion, get the following conclusions: (1) the functional district of Xi'an city in the winter two season of dustfall exceed the standard is serious; the summer two season of dust compared to reference the standard increment is large, pollution than in the two season. Xi'an dustfall flux has a significant difference in different seasons showed in general: spring summer autumn and winter. The amount of dust in different functional areas there are also significant differences, overall, the amount of dust in the function Area change: Industrial District Business District residential area tourist area. (2) there are obvious seasonal differences in concentrations of different forms of nitrogen in dust in the atmosphere of Xi'an City, the nitrate concentration of ammonia nitrogen is the highest in winter, and for the addition of ammonia is not obvious. Xi'an dustfali in metal element the mass concentration in the four quarter of the differences, mainly in the two season, summer two season is relatively low, and the summer two season in the gap is very small. There were significant differences among different functional areas of different forms of nitrogen concentration in Xi'an, and in different seasons showed similar distribution characteristics. Namely: Industrial zone the business district is residential area of tourist area. The ammonia concentration of four functional areas have absolute advantage, that of inorganic nitrogen in Xi'an city on the settlement of ammoniacal nitrogen. (3) Xi'an City Atmospheric metal elements in dust has a larger difference in the concentration of.Cu, different functional areas of the distribution of Pb, Zn, C D in the industrial area in 1.3-1.4 times higher than that in other areas of As, Ba, Fe concentration is low than that in other areas, in addition to Cu, Pb, Ba, the business district, the metal element content is relatively uniform residential and tourist area. The metal element concentration from high to low AlFeBaZnPbCrAsCuNiVCd, which is consistent with the level of law perennial accumulation reduced metal elements in dust concentration.

【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X513

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