土壤-水稻/小麦重金属吸收机制与安全调控

王成尘,田 稳,向 萍*,徐武美,管冬兴,马奇英

土壤-水稻/小麦重金属吸收机制与安全调控

王成尘1,田 稳1,向 萍1*,徐武美2,管冬兴3,马奇英3

(1.西南林业大学生态与环境学院,环境修复与健康研究院,云南 昆明 650224；2.云南师范大学能源与环境科学学院,云南 昆明 650500；3.浙江大学环境与资源学院,浙江 杭州 310058)

为掌握我国水稻和小麦作物的重金属污染情况,收集了我国粮食主产区水稻/小麦-土壤系统中的砷(As)、镉(Cd)、铬(Cr)和铅(Pb)含量,综述了其吸收、转运、积累机制和有效的修复措施.结果表明,我国粮食主产区水稻及小麦籽粒的Cd超标率达31.3%和22.2%,Pb的超标率达26.2%和32.1%,污染情况较为突出;降低As、Cd、Cr和Pb的生物有效性,控制其在水稻/小麦植株中的吸收,能够有效减少籽粒中的积累;土壤-作物系统中重金属的吸收可通过水肥管理、化学改良、植物修复、生物修复和遗传学方法等有效调控,从而实现安全生产.今后,应形成多学科交叉互融的全要素格局来完善我国的土壤污染研究,开发农产品安全生产的污染土壤利用技术,从而更好地保障国家粮食安全生产.

重金属；水稻；小麦；转运机制；积累；安全生产

水稻和小麦处于食物链的开端,需要从土壤中吸收必需和非必需元素,因此有毒金属元素也会进入水稻和小麦,随着食物链运输传递最终进入人体[1].研究表明,作物中低浓度的重金属也可能会损害人体健康[2].因此,研究农作物(水稻和小麦)对重金属As、Cd、Cr、Pb的吸收、迁移和积累具有重要的现实意义.近几十年来,水稻/小麦的重金属污染受到了广泛关注,许多学者对土壤-水稻/小麦系统中的重金属污染进行了大量研究[3-4].然而,大多数的研究都集中在小范围内,针对全国尺度上的水稻/小麦重金属污染研究鲜有报道.

粮食主产区的粮食作物重金属含量很大程度上反映了我国的总体粮食重金属污染水平.本文回顾了我国粮食主产区水稻/小麦籽粒中As、Cd、Cr、Pb污染的研究文章,分析计算其重金属的浓度水平;同时,总结水稻/小麦中重金属的吸收、积累机制和阻控措施,展望了未来研究前景,以期为全面了解中国粮食主产区水稻/小麦重金属污染状况,制定合理有效的防治策略提供参考.

1 研究区域和数据收集

我国粮食主产区是指拥有适宜种植粮食作物的地理区位、土壤条件、气候、技术等,且种植比例大,粮食产量高,能够满足省内粮食消费需求之余还能大量外调的特定粮食产区[5].从粮食种植的分布情况看,粮食主产区主要集中在东北地区、黄淮海地区以及长江中下游地区,包括黑龙江、吉林、辽宁、山东、河北、内蒙古、河南、江西、四川、湖南、湖北、江苏和安徽省.

粮食主产区的水稻和小麦重金属数据来自于Web of Science (WoS)核心合集和中国知网 (CNKI),使用关键词“水稻(rice)”、“小麦(wheat)”、“重金属(heavy metals)”、“砷(As)”、“镉(Cd)”、“铬(Cr)”、“铅(Pb)”、“中国(China)”等,时间设置为2000～2021年,选定的文献应符合以下标准:1)粮食主产区范围内现场或当地水稻/小麦取样,2)研究区域位置清晰或具有相关信息,3)水稻/小麦籽粒重金属含量数据至少包含As、Cd、Cr、Pb其中一种,4)使用科学准确的测定重金属含量的方法,如电感耦合等离子体质谱法(ICP-MS)或原子吸收光谱法(AAS)等.经过人工筛选文献后共收集水稻籽粒样品数据6078份,小麦籽粒样品数据3024份,及相关土壤样点数据10178份.

2 结果与讨论

2.1 我国粮食主产区水稻和小麦籽粒的重金属污染情况

2.1.1 水稻籽粒的重金属污染与来源 据统计,水稻籽粒中的As含量在0.016～0.31mg/kg范围内,与《食品安全国家标准-食品中污染物限量》(GB2762-2017)[6]谷物及其制品中的稻谷限值(£0.2mg/kg)相比,超标率约10.3%;Cd含量处于0.0007～1.42mg/kg之间,约31.3%的水稻籽粒超过限值(£0.2mg/kg);Cr含量在0.046～0.8mg/kg范围内,所有水稻籽粒皆未超过限值(£1mg/kg);Pb含量在0.006～1.35mg/kg范围内,26.2%的水稻籽粒超过限值(£0.2mg/kg)(图1a).由此可知,我国粮食主产区水稻籽粒的Cd及Pb超标情况较为突出,其中,Cd含量超标的地区集中在长江流域,包括湖南、湖北和江西省,而Pb含量超标的地区集中在江苏省(图2).据湖南省湘潭市水稻籽粒Cd 超标的文献报道,该地水稻Cd的主要来源包括灌溉水、化肥和大气沉降,其中,大气沉降输入占总输入通量的76.4%～ 98.3%,显著高于灌溉水和化肥的输入通量;此外,农家肥是畜禽养殖区水稻Cd的重要来源[7];而湖北恩施的研究发现,该地富硒页岩的风化导致重金属(Cd、Zn、Cu、As等)大量进入土壤,从而造成了重金属复合污染,其中,Cd在土壤中具有极高的生物利用度,这与水稻籽粒中Cd的高积累相对应[8];江西的水稻籽粒Cd超标的一份文献表明,稻渔综合种养示范区的土壤Cd值与稻谷中的含量不具有显著相关性,说明其污染源不仅限于土壤,可能还包括化学肥料和农药的使用[9];江苏省水稻籽粒Pb超标地区的研究显示,该区域Pb来源主要是汽车尾气和肥料的应用[10].

图1 全国粮食主产区水稻和小麦籽粒的重金属含量

图2 我国粮食主产区水稻和小麦籽粒中As、Cd、Cr、Pb的空间分布特征

为了对比本文水稻籽粒超标地区的水稻土Cd、Pb水平,本文同时收集了其他一些国家水稻土重金属含量的相关研究,并列出了《土壤环境质量农用地土壤污染风险管控标准(试行)》(GB 15618-2018)[11](以下简称土壤管控标准)的Cd、Pb风险值(表1).与土壤管控标准相比,本研究中水稻土壤的Cd和Pb浓度均超出风险值.相较于前人的研究报道,除泰国外,湖南水稻土中的Cd含量远远超出其他国家和地区,虽然这种差异可能是由于报告分布的不均匀,如在矿山或工业场所周边的稻田中研究的文献较多,但是该数据也应引起重点关注,有必要采取有效的治理和控制策略,减少水稻土壤中的Cd污染;而江苏水稻土Pb含量和其他文献相比处于中等水平,低于全国水稻土Pb平均值30.69mg/kg[12],但却产出粮食主产区范围内Pb含量水平最高的水稻籽粒,可能是因为大气沉积或农药化肥的过量施用[10,13],也可能与该区域种植的水稻品种有关.

表1 不同地区水稻/小麦土与水稻/小麦籽粒中Cd和Pb含量对比

注: 括号中的值代表平均数.

2.1.2 小麦籽粒的重金属污染与来源 根据文献统计,小麦籽粒中的As含量在0.0003～0.97mg/kg范围内,与《食品安全国家标准-食品中污染物限量》(GB2762-2017)谷物及其制品中的小麦限值(£0.5mg/kg)相比,超标率约4.76%;Cd含量处于0.0018～0.9mg/kg之间,约22.2%的小麦籽粒超过限值(£0.1mg/kg);Cr含量在0.053～3.1mg/kg范围内,其中,12.5%的小麦籽粒超过限值(£1mg/kg);Pb含量在0.22～3.64mg/kg范围内,32.1%的小麦籽粒超过限值(£0.2mg/kg)(图1b).由此可知,我国粮食主产区小麦籽粒的Pb及Cd超标情况较为突出,其中,Cd含量超标的地区集中在江苏和四川省,而Pb含量超标的地区集中在江苏、湖北和安徽省(图2).据报道,江苏地区小麦籽粒Cd超标可能是因为小麦在有氧条件下更有利于对Cd的吸收,此外,不同的加工处理也会导致小麦中Cd含量的差异,由于麸皮中往往含有较高浓度的Cd,打磨过程可以有效地降低Cd含量,而该研究采集到的小麦未经打磨[14];江苏省小麦籽粒Pb超标的文献表明,研究区域属于传统农业生产区,且在取样时避开了工业区和交通要道,因而其重金属源主要来自农药化肥投入[15];湖北大冶的研究结合土壤Pb形态分布和作物中Pb在壳部的富集情况,证实了该地土壤和作物主要受大气沉降的污染[16];而安徽省的小麦籽粒Pb超标可能是因为该样点的农民大量使用了复合肥,在短时间内不被作物吸收,因此导致局部土壤Pb含量增加,此外,该区域的烟花炮竹生产业也会造成土壤Pb含量的升高[17].

由表1可以看出,本研究中江苏、四川、湖北和安徽省皆有部分小麦土壤的Cd浓度超出土壤管控标准,但是土壤Pb浓度都低于管控值.与其他国家的数据相比,四川、湖北的小麦土中的Cd含量处于较高水平,而江苏的土壤Cd含量并不高,可能是由于在本文的文献采集标准下,江苏省的数据点较多,四川、湖北的数据点相对较少,且文献多偏向污染区域的研究,因此产生了样点浓度的差异.而江苏、湖北和安徽省的小麦土Pb含量和其他文献相比处于中等水平,但小麦籽粒中的Pb含量却高于其他地区,造成这一情况的原因很复杂,可能与土壤的pH值、有机质含量、小麦品种、气候条件、农业活动和污水灌溉等相关[3].

2.2 土壤-水稻/小麦系统中的重金属吸收与转运机制

农田土壤环境在一定程度上决定着农产品的质量和产量.土壤中的微量元素含量分布受成土母质、土壤理化性质、土壤类型、水分动态等共同作用影响.而水稻和小麦植株各部位微量金属元素的摄取和积累量遵循根>茎/叶>颖壳>籽粒的大小顺序,其总浓度取决于暴露水平.

2.2.1 水稻中的重金属吸收与转运机制 水稻对As的吸收积累随生长周期而变化.在分蘖期,根、茎、叶的As含量迅速增加,在拔节期显著降低,孕穗期和灌浆期再次微幅上升,成熟期达到最大;而稻穗中的As浓度在孕穗期最大,灌浆期急速下降、成熟期微幅上升却低于孕穗期[27].水稻籽粒中As的形态以一甲基砷(MMAV)、二甲基砷(DMAV)和无机砷(iAs)为主,其中,iAs主要包括亚砷酸盐As(III)和砷酸盐As(V)[28](图3a).据报道,水稻在淹水缺氧环境下具有高度吸收和易位As(III)的能力[29].As(III)在水稻体内的运输主要通过Nod26-like内在蛋白(NIPs)、硅(Si)流入和流出转运体OSLsi1/OSLsi2,从而有效地将As转运到水稻植株的各个部位[30].而磷酸盐吸收系统是As(V)进入水稻植株的主要途径[31].研究表明,水稻植株能够降低其根部的As(V),且将As(III)有效地上传至木质部汁液中[29].与木质部途径相比,韧皮部的一些功能也会对籽粒As含量产生较大影响[32].不同的水稻品种和水稻基因型在As积累方面存在显著差异[33],然而,稻根中As的较高吸收和积累的实际机制尚不清楚,据学者推测,这可能是因为在水稻根际表面形成的铁氧化物(铁斑块)吸附了As,从而限制了其进一步转移到植株的地表组织中去[34].

与As相比,水稻中Cd的主要吸收转运过程包含根系吸收、通过木质部流动进行的根向茎/叶的迁移、节间维管传递和籽粒积累等(图3b).在Cd吸收过程中,木质部在Cd从根到茎的运输中起着重要作用[35],而韧皮部则是运输Cd到籽粒的主要途径[13].在水稻植株中,Cd从根到茎的吸收、迁移和积累通常由ZIP(OsIRT1)转运体推进[36].这些ZIP转运体对水稻的生长过程至关重要,而水稻植株关键的微量金属元素的积累能力与ZIP的表达水平有关.据报道,OsIRT转运体在通过稻田根部的Cd摄取中发挥了重要作用[13],而NRAMP3和NRAMP4(金属转运蛋白)转运体及其共同转运体在Cd转运、体内平衡以及抵抗水稻植物Cd毒性作用中也起着至关重要的作用[37].

相较As和Cd,研究土壤-水稻系统中Cr吸收机制的文献较少.存在于土壤中的Cr 主要为Cr(III)和Cr(VI),其中,Cr(VI)具有较高可溶性和毒性;而Cr(III)的毒性较小[38].水稻植株容易吸收并积累Cr(III)和Cr(VI),而水稻土壤-水稻系统中的Cr吸收机制仍然有待进一步深入研究.一般来说,植物通过特定的转运蛋白吸收所需的微量元素,从而维持其生理代谢活动[39],但在吸收过程中,也会同时吸收有害金属元素.研究发现,植物系统中的Cr(III)吸收通常通过被动运输机制发生,由于Cr(VI)与磷酸盐(Pi)/硫酸盐(ST)的结构相似,因此,水稻植株会主动吸收Cr(VI)[40](图3c).

而Pb可通过多种途径进入水稻植物,如质子泵、共转运体、反转运体和离子通道等[13](图3d).据研究报道,Pb2+在水稻根系的吸收并不均匀,其中,在新生细胞中吸收最强[41].同时,蒸腾作用对Pb2+通过木质部从根细胞到地上部,及通过维管束从地上部到茎叶部的推动也起着重要作用;然而,Pb从植株其他部位向水稻籽粒的易位机制尚不清楚[13].此外,研究证实,植株吸收的大部分Pb被保留在水稻根细胞中;根细胞进一步限制了Pb的质外体和共质体运输,阻碍了Pb向地上组织的运输[42].因此,仅有一小部分被吸收的Pb被转移到地上部分,并被重新分配到植株的不同部分.

图3 水稻/小麦-土壤系统中As、Cd、Cr和Pb的吸收、易位及积累机制

2.2.2 小麦中的重金属吸收与转运机制 自然界中的As主要以As(III)、As(V)、MMA和DMA等4种形态被植株吸收[43](图3e).不同品种的小麦茎秆和籽粒对As的积累能力差异较大.其中.As(V)是低pH值或好氧/氧化条件下As的主要形态,它与磷酸根共用转运蛋白,即As(V)的吸收是通过H2AsO4-或H2PO4-与2H+协同运输并进入木质部导管[44].As(V)在根细胞内由砷酸还原酶(AR)转化为亚砷酸盐As(III)[45].As(III)是高pH值、厌氧/还原条件下的主要形态,由于其吸附能力低,能迅速从土壤矿物脱附,并被Nod26-like内在蛋白(NIPs)吸收[46],从而进入植物体内.

与As不同,土壤酸化提高了植物Cd的生物有效性,且根系分泌物会增加其溶解度[47].Cd可以通过质外体和共质体途径在根、茎和叶中运输[48](图3f).此外,小麦中的镉Cd还可以通过3个主要转运体到达根细胞:(1)锌铁转运蛋白(ZIP),如AtIRT1是一种在重金属积累中发生中介的质膜转运体,对二价金属具有广泛的特异性[49],研究发现,当AtIRT1转运体位于根的外层时,它会从土壤中吸收Cd;而当TcZNT1/TcZIP4位于根中时,TcZNT1转运体可介导高亲和力的Zn转运和低亲和力的Cd摄取[50];(2)自然抗性相关巨噬细胞蛋白家族(NRAMP),如OsNRAMP1、OsNRAMP5和AtNRAMP6,其中,OsNRAMP1和OsNRAMP5铁转运蛋白也被称为质膜中的Cd2+内流转运蛋白[51];(3)低亲和力的钙转运体,如TaLCT1[52].Cr在小麦的摄取和转运机制尚未完全清楚.由于Cr是植物的非必要元素,因此植株本身不具有吸收Cr的特定机制,通常是其他离子的转运载体参与其吸收过程[53].Cr(VI)的吸收转运途径是一种涉及必需离子载体(如硫酸盐ST)的主动运输过程[54],而Cr(III)的吸收途径是被动转运过程[55].据报道,根细胞摄入Cr(IV)后会立即还原为Cr(III)[56],Cr主要通过木质部运输传递,从而到达茎秆、叶片和籽粒[53](图3g).一般的,重金属总是大量积累在植物体的根中,少量存在于营养器官和生殖器官[57].据猜测,植物根Cr积累较高可能是因为Cr被固定在植株根细胞的液泡中,其毒性降低,从而维持自身的正常生理过程[58].

有关小麦Pb的分子吸收机制文献较少.据报道,Pb通常以两种方式进入小麦植株,一种是通过根从土壤中吸收Pb,第二种是通过叶片吸收大气沉降中的Pb[59].从土壤中吸收的Pb会积累在根、茎、叶和种子等部位,其中,大部分留存于根中,主要分布在外根冠、覆盖于根冠表面的粘液、根表皮细胞和内皮层的细胞壁中,只有一小部分向上转移到地上组织[60],很少有Pb能够穿透根系内皮层进入中柱部分,因此,内皮层是Pb传递到新芽/茎的屏障[61](图3h).

2.3 降低水稻/小麦重金属污染的安全生产措施

现阶段发现的与重金属积累相关的因素包括土壤-植物重金属吸收的动态过程、与吸收和易位相关的遗传标记和作物收获后的管理活动,而这些因素的有效运作取决于该作物的品种、生长环境和栽培管理的有机结合[22].为此,国内外开展了一系列广泛研究,表2和表3分别列举了降低水稻/小麦重金属污染的方法.主要包括:(1)农业管理方法:水管理、外源添加物(化学改良)、养分管理和土壤改良剂;耕作方式管理;(2)生物修复法:植物修复和微生物修复;(3)遗传学方法等.上述方法的选择主要依赖于水稻/小麦的品种(类别)、环境条件、吸收机制和积累特征等.

2.3.1 农业管理方法 农业管理方法是通过改善土壤的物理化学性质从而固定污染土壤中的重金属.水管理方法的应用是基于土壤水分状况能够决定土壤pH值和氧化还原电位,并影响养分的溶解性和有效性[62].研究发现,在营养期采取干湿交替的灌溉方法能够降低秸秆和籽粒中的As浓度[63],且并不会大幅影响作物产量[64].而水稻在抽穗期前后分别采取干湿交替条件,能够改变重金属的有效性,有效降低植株对Cd的吸收[65].

外源添加物和养分管理属于化学改良.由于As(III)与硅酸的化学性质相似,二者从土壤到根细胞的吸收采用相同的转运体系[66],这导致了水稻吸收和转运过程中Si和As(III)的点位竞争,因此,施用Si可以有效降低As(III)含量.但是也有研究指出,由于Si和As在土壤表面的阴离子吸附存在位点竞争,因此土壤外部施用Si有时会增加土壤溶液中的As浓度,导致根细胞吸收更多的As[67].在水分亏缺条件下施用含P、Fe和/或Si的肥料能够显著提高粮食产量[68].

土壤改良剂通过沉淀、吸附、阳离子交换和表面络合作用固定重金属[69].生物炭具有很高的孔隙率和比表面积,适合从污染水体或土壤中吸附污染物,因此,众多学者开展了大量生物炭运用于土壤改良、植物养分保留、重金属钝化(如As、Cd、Pb等)研究.

耕作方式的改变也能改善水稻和小麦植株的重金属含量.例如,油菜等高积累作物间作可降低水稻Cd含量[70];减耕措施可确保土壤中有机质含量的提高,从而增强Cd等重金属的吸附和络合作用[71].但是相对而言,间作种植不利于机械化操作,比较费工费时.

2.3.2 生物修复法 生物修复法是通过种植超积累植物、耐性微生物或引入富集动物(如蚯蚓)等,利用生物吸附、生物萃取或根系过滤等方式,将土壤重金属转移到生物体或降低重金属的生物有效性,从而达到土壤修复改良的目的.

种植超积累植物能同时降低土壤中几种重金属含量,且生物量大、生长迅速、根系发达,即使在重金属浓度较低时也有较高的积累速率.已发现多种超积累植物,如蜈蚣草具有很强的As富集特性,能够有效去除土壤和土壤孔隙水中的As[72].此外,拟南芥、龙葵和夜蛾也被定义为Cd超积累植物.但是,使用超积累植物进行修复之后,应着重考量其植株的安全处置方式.

微生物在影响水稻和小麦生态系统中As转化和生物有效性方面起着重要作用.它可以影响亚砷酸盐氧化、呼吸、还原和甲基化等[73].例如,侧孢短杆菌(AMF)通过加速As(III)的氧化,从而缓解As(III)在水稻中的毒性[74];接种AMF可促进水稻生长,降低Cd和Pb对地上部的潜在毒性[75].

生物修复技术一度被众多学者认为是最具前景的土壤重金属修复改良方法,但从目前的研究来看,微生物和动物修复依然局限于实验室阶段,在实际应用方面存在诸多痛点难点;反观植物修复,虽然全球已发现700余种超积累植物,一些也已开展广泛的实际应用操作,但是植物吸收/吸附土壤重金属后的处置方法成为了植物修复研究的难题.因此,迫切需要对超积累植物回收的技术原理进行更系统、更深入的研究,以提高其回收效率和利用价值,避免二次污染.

2.3.3 遗传学方法 与上述两种方法相比,遗传学方法是降低水稻/小麦籽粒重金属积累的有效途径之一.基因组编辑技术的最新进展已经取代了传统育种方法,开启了一个新的作物改良时代.例如,水稻能够降低As从根细胞向地上部吸收转运,因此,具有As“抵御”机制的水稻品种(铁斑的发育、根系孔隙度和径向氧损失)与铁斑结合更多,从而减少了As的吸收[76];通过转基因技术加入Cd转运蛋白已成功用于减少Cd污染土壤中的Cd积累[77];在Pb污染的土壤中,可尽量选择在根中储Pb能力强,而在植株的其他部位易位少的品种种植.因此,转基因或非转基因水稻(突变体)可以成为降低水稻Cd含量的潜在技术[13].

表2 降低水稻重金属含量的方法

通过探索调控不同水稻和小麦性状的基因和数量性状基因座(QTLs),成功实现了杂交、选择和杂交育种等常规技术[78].分子育种的方法主要是基于与基因/QTLs连锁的分子标记的鉴定,以及随后的标记辅助选择(MAS)[79].然而,这种育种应用完全依赖于初级基因库中的自然变异.随着遗传学的发展,基因组编辑技术又替代了常规育种的复杂操作,例如水稻ROS1基因与胞嘧啶DNA去甲基化和植物表观遗传改变有关.随着锌指核酸酶(ZFNs)、转录激活效应核酸酶(TALENs)和CRISPR相关核酸内切酶(CRISPR/Cas)技术的发展,这些技术被诸多学者应用于修改谷类作物的特定基因/位点[79].其中,CRISPR/Cas9技术由于其广泛接受性、高性价比以及靶向编辑效率高等优势被有效地应用于作物植株,尤其是谷类作物[80].研究推测,基因组编辑工具的重大改进有望消除转基因技术的缺陷和担忧,并有望取代转基因的开发方法[78].因此,基因组编辑技术在水稻和小麦作物改良方面的应用,为培育高产、优质的新品种提供了更多可能性.

表3 降低小麦重金属含量的方法

5 结论及展望

5.1 我国粮食主产区水稻籽粒的Cd及Pb含量相对较高,相较国家食品安全值超标情况较为突出;水稻土的Cd和Pb浓度均超出我国农用地国家标准值,其中,湖南水稻土中的Cd超标情况最为明显;小麦籽粒的Pb及Cd超标情况较为突出,江苏、四川、湖北和安徽省皆有部分小麦土壤的Cd浓度超出土壤管控标准,但是土壤Pb浓度都低于我国农用地土壤管控标准.未来,水稻/小麦生产的农艺管理活动应分别针对污染和非污染区域因地制宜地提出建议,以高度适应具体地点的需要,减少对全国区域建议的依赖.水稻/小麦政策制定者需要将其关注范围扩大到点源污染之外,并提出管理措施建议,综合考虑多种污染物在毒性和生物有效性方面的潜在差异.

5.2 As、Cd、Cr和Pb等有毒和潜在有毒金属不仅存在于土壤环境中,而且通过不同的转运蛋白在水稻/小麦系统中吸收、转运和积累.今后仍迫切需要在多方位、多层次、多学科地深入研究相关分子机制.为了更深入地阐明重金属在作物中的转运机制,稳定同位素可以作为示踪剂,以便更好地理解其吸收机制.另外,有必要进一步探讨极端环境条件(如频繁的洪水、酸雨和全球变暖)对水稻/小麦土-水系统中重金属形态和迁移的影响.

5.3 综述了水稻和小麦的农业管理方法、生物修复法和遗传学方法.今后可在农艺实践、土壤管理到基因操作等各个层面探索合理的安全生产措施,以确保作物的安全生产.

5.4 迫切地需要农业、环境和医学领域的研究人员紧密合作,以全面评估这些重金属在土壤-植物-人体系统中已发生的和潜在的健康影响;应从农艺实践、土壤管理到基因操作等各个层面探索更为合理有效的重金属胁迫补救策略,以确保粮食作物的安全生产.

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Mechanism of heavy metal uptake and transport in soil-rice/wheat system and regulation measures for safe production.

WANG Cheng-chen1, TIAN Wen1, XIANG Ping1*, XU Wu-mei2, GUAN Dong-xing3, Lena Q. MA3

(1.School of Ecology and Environment/Institute of Environmental Remediation and Human Health, Southwest Forestry University, Kunming 650224, China；2.School of Energy and Environment Science, Yunnan Normal University, Kunming 650500, China；3.College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China)., 2022,42(2)：794～807

To master the heavy metal pollution in rice and wheat crops from main production regions in China, we collected the data from existing literature and analyzed the concentrations of arsenic (As), cadmium (Cd), chromium (Cr) and lead (Pb) in soil-rice/wheat system, summarized their underlying mechanisms of target heavy metals absorption, transport, and accumulation. In addition, effective remediation measures for safe production were also introduced. The results showed that 31.3% and 22.2% of Cd, 26.2% and 32.1% of Pb in rice and wheat grains are over the value of China National Standard (GB2762-2017). Reducing the bioavailability of As, Cd, Cr and Pb and controlling their absorption in the soil-rice/wheat system could effectively decrease their accumulation in grains. The heavy metals uptake in soils-crop systems can be effectively decreased by water and fertilizer management, chemical modification, phytoremediation, bioremediation and genetic methods to achieve safe production. In the future, we should form a multi-disciplinary and integrated all factor pattern to improve the soil pollution research in China. Furthermore, developing the contaminated soil utilization technology for the safe production of agricultural products, so as to better ensure the national food safety production.

heavy metals；rice；wheat；transport mechanism；accumulation；safety production

X131.3

A

1000-6923(2022)02-0794-14

王成尘(1988-),女,新疆石河子人,西南林业大学博士研究生,主要从事环境污染与人体健康研究.发表论文2篇.

2021-07-12

云南省创新团队项目(202005AE160017);国家自然科学基金资助项目(41967026);国家林业和草原局林草科技创新青年拔尖人才项目(2020132613);云南省高层次人才引进计划项目(YNQR-QNRC- 2018-049);云南省教育厅科学研究基金资助项目(2021Y231)

* 责任作者, 研究员, xiangping@swfu.edu.cn