【作者】 李霞；

【导师】 荣湘民； 李法云；

【作者基本信息】 湖南农业大学 ， 植物营养学， 2013， 博士

【摘要】 城市污泥是一种以有机成分为主、组分复杂的混合物,其中包含有潜在利用价值的有机质、氮、磷、钾和各种微量元素,可作为肥料或退化土壤的改良剂,实现城市污泥的资源化利用,具有良好的生态环境效益。同时,土地沙漠化导致土壤质量退化,生态系统生产力下降,进而制约当地的生态环境建设与发展。因此,沙地退化土壤的修复已成为21世纪环境发展及生态建设的研究热点。将城市污泥资源化利用与沙地土壤改良结合起来,是环境生态工程领域的新途径。因而,开展城市污泥在退化沙地土壤改良的应用研究具有非常重要的意义。然而,污泥中大量重金属及多种污染物的存在,成为限制污泥土壤改良的主要因素,因此,对于城市污泥施用过程中可能产生的污染风险研究也显得尤为重要。本论文以科尔沁典型退化沙地土壤作为研究对象,以沈阳市城市污泥为试验材料,主要采用分析测试与室内模拟试验相结合的方法,探讨脱水污泥在对退化沙地土壤的改良过程中对土壤及植物的影响,并结合综合效益分析,为城市污泥的资源化利用及退化沙地土壤的改良提供科学依据。研究结果表明,沈阳市3座城市污水处理厂污泥的pH值均呈弱碱性,含水率与溶解性盐类含量较高。污泥中有机质、总氮、总磷、总钾的含量分别为400-531g/kg,14.86-17.58g/kg,13.15-28.54g/kg,6.51-9.13g/kg,显著高于农家肥(猪粪与牛粪),具有较好的土地利用潜力。各污水处理厂污泥中重金属的含量受污水处理厂污水来源、污水处理规模及污水处理工艺等因素影响存在一定的差异,其中污泥中Zn的含量较高,在4285-7154mg/kg,均超出污泥相关的标准限值。污泥中均检出含有四环素类、磺胺类、大环内酯类和喹诺酮类这四类抗生素,其中诺氟沙星和氧氟沙星的含量最高,分别为7.20-9.27mg/kg和0.18-0.85mg/kg,已大大超出我国污水处理厂污泥中此种抗生素的平均含量。其次为四环素类抗生素,其中土霉素的含量在0.40-0.85mg/kg。综合分析各污水处理厂污泥的特征,应选取城市生活污泥作为土壤改良的材料。污泥的施入可显著增加退化沙地土壤表层中氮磷养分含量,利于植物对营养物的吸收。其中土壤中磷素不易发生迁移,而土壤中氮素向下迁移的能力较强,可见城市污泥施用于土壤后氮素淋溶的风险大于磷。污泥的施入对淋出液中氮、磷养分含量也存在显著影响,污泥施用量为30t/hm2时,淋出液中总氮、总磷含量与不施用污泥的对照处理间未存在显著差异(P>0.05),而硝态氮的含量较不施用污泥的对照处理增加11%-33%,对地下水造成污染的风险较小。污泥施用量为60、90t/hm2两个处理中,经淋洗3次后,即累积降雨量达150mm时,淋出液中全氮及硝态氮含量显著增加(P<0.01),其中硝态氮含量超出地下水环境质量标准中Ⅲ类水质标准限值(20mg/L),存在对地下水污染的风险。污泥的施用对pH有显著影响,最终稳定在8.24-8.54。淋出液中Cu、Zn、Pb的浓度变化趋势大体呈现逐渐降低的趋势,在所有的污泥处理中,随淋洗量的增加,并未增加其对地下水的污染风险。而污泥施用量为60、90t/hm2时,在第五次淋洗(即降雨量达250mm)后Cd浓度增加幅度较大,最大浓度达到未施用污泥的对照处理中Cd浓度的3倍左右,已超出地下水质量标准Ⅲ类水质标准限值(Cd≤0.01mg/L),存在污染风险。重金属Cd主要在土壤表层累积,但随降雨量的增加,存在向下层土壤迁移的风险,在污泥施用过程中应重点关注。本研究的结果表明,污泥应用于沙地土壤改良的最佳污泥施用量应控制在30t/hm2范围内,最佳施用期应在降雨量较少的春季。若要提高污泥的施用量,可考虑少量多次的施入,同时要注意避免在降雨频次较多、雨量较大的夏季施用。重金属镉的在短期(1-3d)内可降低土壤中硝态氮、铵态氮、亚硝态氮的浓度,其中3d内的影响最为明显,之后随着作用时间的延长,三种形态氮素浓度的变化趋于缓和。土霉素对土壤的氨化作用产生抑制,抑制程度与土霉素浓度相关,而土霉素对土壤中硝态氮含量的影响不显著。氧氟沙星为10、25mg/kg时,可促进土壤中微生物的硝化作用和氨化作用,但随氧氟沙星浓度的提高呈现出对硝化和氨化的抑制作用。土霉素与氧氟沙星两种抗生素与重金属镉的复合污染对土壤中无机氮转化的影响较各自单一污染的影响程度大。城市污泥的施用可显著促进狼尾草的生长,尤其是在污泥施用量为30t/hm2时,狼尾草的鲜重及叶面积指数分别为未施用污泥处理的3.07倍和2.33倍,随污泥施用量的增加,狼尾草的鲜重及叶面积指数均有所下降,但仍高于未施用污泥的对照处理。污泥的施用使土壤中全氮含量分别增加1.23、2.13、7.10倍,全磷含量分别增加11.94%、44.78%、91.94%。同时,污泥的施用也提高了植物对重金属的吸收,其中对狼尾草中Cd含量影响最大,且与各处理间存在着显著差异。不同处理下Cu、Cd、Pb、Zn的转移系数均小于1,说明狼尾草的根系对重金属有一定的富集能力,其中狼尾草的根对Cd、Pb的富集能力较Cu、Zn的富集能力强。因此控制污泥施用量为30t/hm2范围内,可有效增加土壤肥力,提高狼尾草生物量,且污泥中重金属含量不会影响植物的生长。通过分析城市污泥有机质及N、P、K等营养元素成分含量,能量及经济效益可以看出,污泥应用于退化土壤的改良也是污泥资源化利用的一种较好方法,具有很大的潜力和意义。综上所述,城市污泥应用于退化沙地土壤的改良通过科学的指导与管理,能取得较好的经济效益,并能改善生态环境。同时,对于污泥在改良退化土壤的应用过程中所存在的安全问题可通过时空匹配、避免积累、水土监控及体制监管等方式解决,保证其应用的安全性。更多还原

【Abstract】 Sewage sludge contains organic matter, nitrogen, phosphorus, potassium and trace elements. It can be used as fertilizer or soil conditioner to achieve the resource utilization. Meanwhile, desertification not only causes the degradation of the soil quality and the decline of productivity, but also restricts the construction and development of the local eco-environment. It would be a new way to combine the utilization of municipal sludge with the improvement of the degrading sandy soil. However, the contained heavy metal and organic contaminants in the sewage sludge are the factors limiting land improvement. Therefore, it is really necessary to research the risk of pollution during the utilization of sewage sludge. Korqin Sandy soil was chosen as study objects and the sewage sludge was collected from wastewater treatment plant of Shenyang. The major objective of this work was to investigate the impact of the dewatered sludge on soil and plants during the process of improvement. And combined with the comprehensive benefit analysis, was to provide the reference information for resource utilization of sewage sludge and improvement of degrading sandy soil.The results showed that the pH of the sewage sludge was weak alkaline and high level in moisture contents and dissolved salts. The contents of organism, total nitrogen, total phosphorus and total potassium were400-531g/kg,14.86-17.58g/kg,13.15-28.54g/kg and6.51-9.13g/kg, respectively. These data showed that it was significantly higher than manure (swine manure and cow dung), with high potential in land-use. The content of heavy metal in sludge in different wastewater treatment plants are variety because the source of the sewage, the capacity of wastewater treatment plant and the treatment processes. The highest content in the sewage sludge was Zn, varying from4285mg/kg to7154mg/kg which are all higher than the limits of standard. Moreover, in all the sewage sludge samples of three sewage treatment plants, tetracycline, sulfonamides, macrolides and quinolones were detected. The contents of norfloxacin and ofloxacin are the highest, with7.20-9.27mg/kg and0.18-0.85mg/kg respectively. Followed by tetracycline antibiotics, the content of oxytetracycline is0.40-0.85mg/kg. Combined all characteristics of the sewage sludge in all wastewater treatment plants, municipal sludge was taken as the material to improvement soil.A soil column leaching experiment showed that the different addition rates of the sewage sludge to soil significantly increased the content of nitrogen and phosphorus in topsoil and improved the sandy soil quality. The sewage sludge application rates had a significant effect on nitrogen and phosphorus concentrations in leacheate, but the leaching risk of nitrogen to groundwater was higher than that of phosphorus. The concentrations of total nitrogen (TN) and total phosphorus (TP) in leacheate after applying sewage sludge with30t/hm2had no significant difference compared with the control treatment. The nitrate concentrations were enhanced by11%-33%compared to the control treatment and there was not significant difference between them (P>0.05). The concentrations of nitrogen and phosphorus in leacheate after applied60t/hm2and90t/hm2were significantly increased (P<0.01). The nitrate concentrations were greater than the threshold values for Environmental Quality Standards for Ground Water in China after the third leaching, increasing a potential contamination risk to groundwater.And the application of sludge had an impact on the pH value, eventually stabilized at8.24-8.54. The Cu, Zn, Pb concentrations in leachate decreased as leaching times, it may not pose a risk to groundwater contamination. The soil column leaching experiment results showed that the pH in leachate was opposited to conductivity, and that the pH initially increased and then stabilized with the different addition rates of the sewage sludge to soil. The concentrations of Cd applied sewage sludge60t/hm2and90t/hm2increased with the fifth leaching times, the maximum concentration of Cd in leachate was3times than the control treatment. With the increase of rainfall, Cd accumulated in the top soil was a risk of migration to the subsoil. The results indicated that Cd had contamination risk during soil improvement.The heavy mental of Cd could decrease the concentration of nitrate nitrogen, ammonium nitrogen and nitrite nitrogen in the soil in1-3days. The influence of Cd in three days was the most obvious. And the changes of the concentration of the three forms of nitrogen trend toward a moderation. Oxytetracycline inhibited to the soil ammonification and the level of inhibition is related to the concentration of the oxytetracycline. The condition of10and25mg/kg ofloxacin could promote the nitrification and ammonification. The interaction between oxytetracycline, ofloxacin and Cd would influence on inorganic nitrogen transformation in the soil in a significant way.Application of sewage sludge significantly promoted the growth of Pennisetum alopecuroides. When the application rate was30t/hm2, the fresh weight and leaf area index of P. alopecuroides were3.07and2.33times compared to the control treatment, and then decreased with increased application rate. The concentrations of nitrogen and phosphorus in soil after applied sewage sludge were enhanced by1.23,2.13,7.10times and11.94%,44.78%,91.94%, compared to the control treatment. The uptake ability of P. alopecuroides to heavy metals was promoted, especially Cd, which was significantly different among treatments (P<0.05), while the Cu, Pb, Zn contents in P. alopecuroides were not significant. The transfer coefficient of Cu, Cd, Pb, Zn was less than1, indicating that the roots have the enrichment of heavy metals. Hence, the application rate of30t/hm2can effectively improve soil fertility and increase P. alopecuroides biomass.Analyses on the organic matter, N, P, K and other nutrient ingredients of sewage sludge, and the energy and economy showed that sewage sludge could be widely used in the future. The sludge application to the degraded soil improvement would be a good method. From the economic aspect, application of sewage sludge to degraded sandy soil was feasible, and it could achieve better economic efficiency and improve the ecological environment through scientific guidance and management.更多还原