【作者】 马强；

【导师】 吴启堂；

【作者基本信息】 华南农业大学 ， 农业环境保护， 2019， 博士

【摘要】 随着经济的快速发展,产生的环境污染问题已经严重影响人们的生存环境,其中重金属污染土壤由于具有普遍性、隐蔽性、不可逆转性,危害巨大,导致粮食、蔬菜作物对重金属的过量吸收,从而间接地对人类造成严重健康危害。目前,修复重金属污染土壤的技术多种多样,化学淋洗作为一种操作较简单、快速、高效的污染土壤修复技术,受到持续关注。同时,电动修复技术（EK）作为一种不添加药剂可以把重金属从污染土壤中去除的技术,也受到了研究者的青睐。然而,单一的电动修复技术不能达到满意的效果。针对目前重金属污染土壤修复技术存在的问题,本文以化学淋洗与电动技术联合修复重金属污染土壤,采用田间试验和室内实验相结合的研究方法,分析了天然淋洗剂稻草发酵液、农用钾肥以及常用的化学淋洗剂对土壤重金属的去除效果,并结合电动修复技术,进一步提高土壤中重金属的去除率。本论文主要的研究结果如下:（1）韶关大田试验选择稻草秸秆厌氧发酵、稻草秸秆好氧发酵、氯化钾（KCl）和醋酸（HAc）进行淋洗,经过120 d的处理,不同处理下土壤的p H值变化幅度不明显,KCl对土壤中重金属（Cd、Pb、Cu和Zn）去除效果最好,其中,KCl对Cd的去除率是19.20%,对Pb的去除率是6.84%,对Cu的去除率是7.56%,对Zn的去除率是15.94%。（2）广州大田试验选择FeCl₃、KCl和HAc进行大田淋洗试验,经过120 d的处理,FeCl₃处理土壤的p H下降明显,40天后p H值降至3以下,随着淋洗时间的延长,后期回升至3.2;HAc和KCl也造成土壤p H轻微降低,后期有所回升。FeCl₃对土壤中重金属（Cd、Pb、Cu和Zn）去除效果最好,其中,对Cd的去除率是39.08%,对Pb的去除率是12.41%,对Cu的去除率是28.08%,对Zn的去除率是20.91%。同时淋洗过程中进行地下水监测,监测结果表明,淋洗液没有对地下水造成污染。（3）不同用量KCl（0.2%、0.5%和1%）土柱垂直淋洗实验表明,KCl是一种强离子交换盐,可以从酸性土壤中去除Cd,当KCl的用量从土壤重量的0.2%增加到1%的时候,Cd的去除率从38.6%增加到84.1%。单独使用垂直EK处理不能有效地将重金属从上表层土壤（0-20 cm）迁移到较深层,但是显著增加了阴极附近土壤的p H值,可以钝化重金属,从而阻止水稻或者蔬菜对重金属的吸收。KCl淋洗联合EK提高了表土（0-20 cm）土壤重金属的去除效率,特别是1%KCl+EK处理,Cd的去除效率为94.8%,达到国家农业地土壤标准,值得在现场实验中进一步验证。（4）FeCl₃、Fe（NO₃）₃、KCl、KNO₃以及HCl的振荡淋洗实验结果表明,FeCl₃和Fe（NO₃）₃对土壤中重金属具有较好的去除效果,中性盐KCl和KNO₃去除效果一般;通过比较Fe³⁺、H⁺、K⁺和Cl^-对土壤中重金属Cd、Pb、Cu和Zn的去除效果,不同离子对Cd的去除作用大小为:H⁺的作用>Fe³⁺的作用>K⁺的作用>Cl^-的作用;不同离子对Pb的去除效率为:Fe³⁺的作用>H⁺的作用>K⁺的作用>Cl^-的作用;不同离子对Cu的去除效率为:Fe³⁺的作用>H⁺的作用>K⁺的作用>Cl^-的作用;不同离子对Zn的去除效率为:H⁺的作用>K⁺的作用>Cl^-的作用>Fe³⁺的作用。（5）不同化学淋洗剂振荡淋洗联合电动修复实验表明,在土壤表层0-10 cm的Cd、Pb、Cu和Zn均有向下迁移,但在10-20 cm土层产生积累,不利于农田土壤修复达标,还应采用前述的垂直淋洗联合电动修复技术。更多还原

【Abstract】 With the rapid development of the economy,the environmental pollution problems have seriously affected people’s living environment.The heavy metals contaminations of soils are widespread,hiden and irreversible,and detrimental to environment.Excessive heavy metals in the soils will lead to the excessive absorption of heavy metals by food crops,may indirectly cause serious health hazards to human.At present,there are various technologies for remediating heavy metals contaminated soils.Chemical leaching is a simple,fast and efficient method for soils clean-up,and attracts attention of scientists.At the same time,electrokinetic（EK）remediation can remove heavy metals from contaminated soil without adding chemical,has also been favored by researchers.However,a single electrokinetics can not achieve satisfactory results.Facing to these problems,this paper combines chemical leaching and electrokinetic technology to remediate soils contaminated by heavy metals,by conducting field tests and laboratory experiments,to compare the rice straw fermentation liquid,potassium fertilizer and commonly used chemical washing agents to leach out heavy metals from soil.Furthermore,combining electrokinetic technology with chemical leaching is studied to further increase the removal rates of heavy metals from contaminated soils.The main outcomes of this paper are as follows:（1）The Shaotian field experiment selected anaerobic fermentation of straw straw,aerobic fermentation of straw straw,KCl and HAc for the chemical leaching.After 120days of treatment,the p H value of soil under different treatments was not obvious;KCl had the best removal effect on heavy metals（Cd,Pb,Cu and Zn）in soil.Among them,the removal rate of Cd was 19.20%,the removal rate of Pb was 6.84%,the removal rate of Cu was 7.56%and the removal rate of Zn was 15.94%.（2）The Guangzhou field experiment selected selected FeCl₃,KCl and HAc for the chemical leaching.After 120 days of treatment,the p H of the soil treated with FeCl₃decreased significantly.After 40 days,the p H dropped to below 3,and as the rinsing time prolonged,it rose back to 3.2 in the later stage;acetic acid and KCl also caused a slight decrease in soil p H and a rebound in the later stage.FeCl₃ had the best removal effect on heavy metals（Cd,Pb,Cu and Zn）in soil.Among them,the removal rate of Cd was 39.08%,the removal rate of Pb was 12.41%,the removal rate of Cu was 28.08%and the removal rate of Zn was 20.91%.At the same time,groundwater monitoring was carried out during the leaching process,the monitoring results showed that the eluent did not pollute the groundwater.（3）Vertical leaching experiments with different amounts of KCl（0.2%,0.5%and 1%）showed that KCl is a strong ion exchange salt,which can remove Cd from acidic soil,when the amount of KCl was increased from 0.2%to 1%of the soil weight,the removal rate of Cd increased from 38.6%to 84.1%.When the amount of KCl was increased from 0.2%to 1%of the soil weight,the removal rate of Cd increased from38.6%to 84.1%.The vertical EK treatment alone did not effectively transfer heavy metals from the upper surface soil（0-20 cm）to the deeper layers,but significantly increases the p H of the soil near the cathode,which can passivate heavy metals,thereby preventing the absorption of heavy metals by rice or vegetables.KCl leaching combined with EK improved the removal efficiency of heavy metals in topsoil（0-20 cm）soil,especially 1%KCl+EK treatment.The removal efficiency of Cd was 94.8%,which reached the national agricultural soil standard.It was worth further stuied in the field experiment.（4）Batch experiments of soil washing by FeCl₃,Fe（NO₃）₃,KCl,KNO₃ and HCl showed that,FeCl₃ and Fe（NO₃）₃ had good removal effects on heavy metals in soil,and the neutral salts KCl and KNO₃ were generally removed.By comparing the removal effects of Fe³⁺,H⁺,K⁺and Cl^-on heavy metals Cd,Pb,Cu and Zn,the role of different ions in the removal of Cd followed order:H⁺>Fe³⁺>K⁺>Cl^-,For Pb,Fe³⁺>H⁺>K⁺>Cl^-;For Cu,Fe³⁺>H⁺>K⁺>Cl^-;For Zn,H⁺>K⁺>Cl^->Fe³⁺.（5）Electrokinetic remediation combined with soil washing with different chemicals showed that Cd,Pb,Cu and Zn migrated out-off the topsoil（0-10 cm）,downward to the layer of 10-20 cm and accumulated there,this was unfavorable to clean-up agricultural soils,and the previously proposed vertical leaching and electrokinetic remediation was necessary.更多还原