【作者】 辜娇峰；

【导师】 廖柏寒；

【作者基本信息】 中南林业科技大学 ， 生态学， 2017， 博士

【摘要】 伴随我国工农业的快速发展,我国耕地受Cd和As等重金属污染的问题日益严重。湖南省是有色金属之乡和鱼米之乡,规模化矿业开采与冶炼对矿区生态环境及农业生产带来了严重破坏,严重地制约着湖南省广大地区水稻生产安全和稻米食用安全。如何治理Cd和As复合污染农田,如何控制Cd和As向水稻中转移是一个亟待解决的环境问题。本研究围绕稻田土壤Cd和As复合污染的修复,以郴州柿竹园矿区(A矿区)及湘西州保靖县复兴村矿区(B矿区)不同Cd和As污染程度的稻田土壤为研究对象,通过改良剂筛选实验、水溶液吸附实验、水稻盆栽实验以及大田实验等研究,研发了一种组配改良剂QFJ,系统阐述了应用QFJ降低土壤Cd、As生物有效性和糙米Cd、As含量的机制,提出了一套控制稻田Cd和As生物有效性和迁移转运的有效技术。研究结果如下:(1)研制出以羟基磷灰石、沸石和改性秸秆炭3种物质为主要成分,按一定质量比例组配的改良剂QFJ,确定其作用机制:3种物质具有较大的比表面积,可与溶液中Cd2+和As5+发生表面吸附和孔道吸附,QFJ含有的-OH、-COOH、-Si-O-Si以及C032-基团与溶液中Cd2+、As5+离子发生了交换吸附、共价结合,生成了羧酸盐类、硅酸盐类和碳酸盐类物质,从而将土壤溶液中游离的Cd2+、As3+和As5+原位钝化。(2)施用组配改良剂QFJ改良Cd和As复合污染稻田土壤,水稻盆栽实验显示:根际土壤pH值、CEC和OM含量呈现上升趋势。QFJ的施用使得水稻黄华占和T优272根际土壤中Cd的交换态含量呈现下降趋势,可分别下降12.6%～39.8%和20.6%～70.6%;QFJ施用量在0.5～2.0 g·kg-1之间对As的交换态含量有降低作用,分别降低12.2%～55.1%和7.0%～39.5%,但施用量增加后使得交换态As含量急剧增大。随着QFJ施用量的增加,土壤中Cd的毒性浸出量逐渐下降,As的毒性浸出量先下降后上升。土壤pH值、CEC与土壤中Cd的交换态含量、毒性浸出量及酸提取态含量具有正的线性关系;土壤pH值与土壤中As的交换态含量、毒性浸出量具有负的线性关系。(3)盆栽实验中,施用QFJ改变了 Cd和As的赋存形态,降低了 Cd酸提取态含量,使难溶的有机结合态Cd分别增加6.8%～49.5%和2.5%～56.5%;同时,降低了As交换态含量,使难溶的钙结合态As含量分别增加34.1%～93.4%和2.8%～53.3%;但QFJ施用量超过4.0 g·kg-1时,土壤中交换态As含量增大。(4)盆栽实验中,QFJ施用使得水稻各部位Cd含量均低于对照组CK,糙米中Cd含量可从0.49 mg·kg-1下降到0.11 mg·kg-1;水稻植株各部位Cd的含量大小依次是根>茎叶>糙米>谷壳。QFJ施用量控制在0.5～2.0g·kg-1水平,显著降低水稻地上各部位As含量,且在2.0 g·g-1施用量,2种水稻糙米中As含量从0.27 mg·kg-1、0.28mg·kg-1下降到最低值0.11mg·kg-1、0.16mg·kg-1,但随着施用量的增加,水稻各部位中As含量呈现上升趋势;水稻植株各部位As含量大小依次是根>茎叶>谷壳>糙米。(5)盆栽实验显示,水稻根系对Cd和As的富集系数BAF分别为0.65～1.26和0.024-0.061,根系富集Cd的能力较As强;水稻各部位对Cd的转运系数TF依次是TFCd-hb>TFCd-sh>TFCd-rs,对 As 的是 TFAs-rs>TFAs-hb>TFAs-sh,水稻谷壳对 Cd 的转运能力最强,而根对As的转运能力最强;QFJ的施用降低了水稻植株对Cd和As转运量的系数,有效降低了水稻植株地上部位Cd和As的累积总量。(6)田间实验显示,随着QFJ施用量的增加,2矿区水稻各生育期根际土壤pH值、CEC和OM含量有增大趋势;QFJ的施用在各生育期均可显著降低2矿区土壤中交换态Cd含量,且在水稻分蘖期时,降低土壤交换态Cd含量的幅度最大;而针对土壤交换态As含量2个矿区呈现相反的结果,A矿区有增大风险而B矿区呈现降低风险的趋势。QFJ的施用也可显著降低水稻各生育期2矿区土壤中Cd的毒性浸出量,对B矿区土壤As的毒性浸出量也有降低的作用,但对土壤A矿区中As的毒性浸出量,在4.0 g·kg-1施用量时则有提高的风险。(7)田间实验显示,灌浆期是水稻植株大量累积Cd和As的时期。QFJ的施用可有效降低A矿区(土壤Cd总量3.58 mg·kg-1,As总量124.79 mg kg-1)各生育期水稻各部位中Cd含量,也可降低成熟期水稻各部位中As含量。QFJ施用量在4.0g·kg-1水平时,使成熟期糙米Cd含量从0.46mg·kg-1下降到0.18mg·kg-1,无机As含量从0.22 mg·kg-1降低到0.18 mg·kg-1,糙米中Cd和无机As含量同时低于0.2 mg·kg-1,达到水稻安全生产要求。更多还原

【Abstract】 With the rapid development of China’s industry and agriculture,the pollution problem of cultivated land with heavy metals like Cd and As becomes increasingly grim.As "town of nonferrous metals" and "town of agriculture and fishery",Hunan Province is suffering from the severe pollution and destruction by large-scale mining to adjacent ecological environment and agricultural land,which seriously restricts the rice production and edible safety.How to manage the farmland suffering Cd-As complex pollution and control Cd-As translocation to rice turns to be an urgent environmental task.Surrounding the remediation of paddy soil suffering Cd-As complex pollution,a combined amendment QFJ was developed in this paper through investigating the paddy soil with different Cd-As pollution levels in Mine A(Shizhuyuan Mining Area in Chenzhou)and Mine B(the mining area in Fuxing Village,Baojing County,XiangXi Autonomous Prefecture)based on amendment screening experiment,aqueous solution adsorption experiment,rice pot experiment and field experiment.Furthermore,the mechanisms of QFJ to reduce Cd and As bioavailability in soil as well as their concentrations in brown rice were systematically described,thus providing an effective technique for controlling the bioavailability and translocation of Cd and As in paddy field.Our findings have been expatiated below.(1)The action mechanisms of QFJ,an amendment developed by combining hydroxyapatite,zeolite and biochar according to definite ratios,were determined in our study.Owing to large specific surface area,all these 3 substances could adhere Cd2+ and As5+ in the solution through surface adsorption and channel adsorption.The exchange adsorption and covalent binding of-OH,-COOH,-Si-O-Si and CO32-groups with Cd2+ and As5+ ions would produce carboxylates,silicates and carbonates,thereby realizing the situ immobilization of Cd2+,As3+ and As5+ freeing in the soil solution.(2)The rice pot experiment to verify QFJ improving paddy soil suffering Cd-As complex pollution demonstrated that pH values,CEC and OM contents in the rhizosphere soil followed an increasing trend.QFJ application reduced exchangeable Cd concentrations in the rhizosphere soil of Huanghuazhan and T You 272 by 12.6%～39.8%and 20.6%～70.6%respectively;QFJ application amounts between 0.5 and 2.0 g·kg-1 exerted a lowering effect on exchangeable As by 12.2%～55.1%and 7.0%～39.5%respectively,while increased application levels were associated with dramatically elevated exchangeable As concentrations.With the increase of QFJ application,the TCLP extracted Cd level in soil was gradually reduced,whereas that of As was decreased first and then increased.Soil pH value and CEC were found in a positive linear relationship with the levels of exchangeable Cd,TCLP extracted Cd and acid extractable Cd in soil,while soil pH value exhibited a negative linear relationship with the levels of extractable As and TCLP extracted As.(3)In the rice pot experiment,applying QFJ changed the chemical speciation fraction of Cd and As in soil.It reduced acid extractable Cd concentrations,and promoted transformation of soil Cd from soluble to insoluble ones.As a result,the concentrations of soil organic Cd increased by 6.8%～49.5%and 2.5%～56.5%,respectively.It also promoted transformation of soil As from soluble to insoluble,thus increasing calcium-bonded As concentrations by 34.1%～93.4%and 2.8%～53.3%respectively,and reducing exchangeable As concentrations.However,when the application rate of QFJ reached beyond 4.0 g kg-1,the soil exchangeable As concentrations turned upwards.(4)According to the rice pot experiment,the Cd concentrations in all rice parts were lower than the control group CK,and the Cd concentrations in brown rice were lessened from 0.49 mg·kg-1 to 0.11 mg·kg-1;the Cd concentrations in different rice parts followed the rank of roots>straws>brown rice>husks.QFJ application of 0.5～2.0 g·kg-1 could significantly reduced the As concentrations in each overground rice part.With QFJ application at 2.0 g·kg-1,the As concentrations in brown rice of two varieties were decreased from 0.27 mg·kg-1 and 0.28 mg·kg-1 to the minimum values of 0.11 mg·kg-1 and 0.16 mg·kg-1,respectively.However,with the increase of application amount of QFJ,the As concentrations in all rice parts began to rise.The As concentrations in different rice parts followed the rank of roots>straws>husks>brown rice.(5)The rice pot experiment showed that Cd bioaccumulation factor(BAF)(of rice roots varied in the range of 0.65～1.26,while As BAF in the range of 0.024～0.061,showing obviously that bioaccumulation capacity of the rice roots was greater for Cd than for As.The Cd translocation factors(TF)of rice parts were in the order of TFCd-hb>TFCd-sh>TFCS-rs,whereas As TFs were in the order of TFAs-rs>TFAs-hb>TFAs-sh.These orders suggested that among various rice organs,rice husk was the highest in Cd transferring capacity,while root was the highest in As transferring capacity.Application of QFJ also decreased the rice translocation quantity factor(TQF)of Cd and As,and then decreased the total accumulation quantity of rice plants of Cd and As in the overground.(6)The field experiment showed that the pH value,CEC and OM contents in the rhizosphere soil at different growing stages were increased with QFJ applying amounts in both mining areas.The QFJ application could significantly reduce the exchangeable Cd concentrations at different rice growing stages in both mining areas,with the highest reduction amplitude reported at the tillering stage.Contrary results were observed between two mining areas in terms of exchangeable As in soil,where Mine Area A exhibited increased risk while Mine Area B showed a risk-reducing tendency.QFJ application could also significantly decrease the TCLP extracted Cd levels in soil at different rice growing stages in both mining areas;the similar function was observed in the TCLP extracted As levels in Mining Area B,but the application amount of 4.0 g·kg-1 was associated with increased risk in Mining Area A.(7)The field experiment demonstrated that QFJ application could not only effectively reduce the Cd concentrations in all rice parts at different growing stages,but also lessen the As concentrations in all rice parts at the maturing stage.At QFJ application amount of 4.0 g·kg-1,the Cd concentration in brown rice was decreased from 0.46 mg·kg-1 to 0.18 mg·kg-1,whereas inorganic As from 0.22 mg·kg-1 to 0.18 mg·kg-1;both the Cd and inorganic As concentrations in brown rice were less than 0.2 mg·kg-1,which met the requirement set in the National Food Standards(GB 2762-2012).更多还原