环境科学研究  2017, Vol. 30 Issue (9): 1398-1405  DOI: 10.13198/j.issn.1001-6929.2017.02.63

引用本文  

石陶然, 田凯, 包环宇, 等. 多环芳烃在冬小麦体内的吸收与转运及富集研究进展[J]. 环境科学研究, 2017, 30(9): 1398-1405.
SHI Taoran, TIAN Kai, BAO Huanyu, et al. Research Advances in Uptake, Translocation and Accumulation of Polycyclic Aromatic Hydrocarbons in Winter Wheat[J]. Research of Environmental Sciences, 2017, 30(9): 1398-1405.

基金项目

国家自然科学基金项目(41571456);河南省高校科技创新人才支持计划项目(14HASTIT048)

责任作者

吴福勇(1973-),男,河南方城人,教授,博士,博导,主要从事土壤植物修复、PAHs毒性机理、健康风险评价及食品质量安全研究,wfy09@163.com

作者简介

石陶然(1986-),女,山西忻州人,shitaoran@126.com

文章历史

收稿日期:2016-12-08
修订日期:2017-05-23
多环芳烃在冬小麦体内的吸收与转运及富集研究进展
石陶然1,2 , 田凯1,2 , 包环宇1,2 , 侯劭炜1,2 , 刘雪平3 , 吴福勇1,2     
1. 西北农林科技大学资源环境学院, 陕西 杨凌 712100;
2. 农业部西北植物营养与农业环境重点实验室, 陕西 杨凌 712100;
3. 河南城建学院市政与环境工程学院, 河南 平顶山 467036
摘要:多年来以煤炭为主的能源消费结构和经济社会持续发展,导致我国PAHs(多环芳烃)排放量居高不下,直接造成土壤和大气PAHs严重污染.为了探明PAHs在冬小麦体内的积累过程和调控机制,在系统分析PAHs在冬小麦体内的吸收、转运和富集的基础上,重点阐述了冬小麦PAHs根系吸收和叶面吸收影响因素方面的最新研究进展.研究发现:① 小麦根系对PAHs的吸收包括主动吸收和被动吸收两种方式,其中主动吸收是一个载体协助、消耗能量、PAHs与H+共运的过程;被动吸收除了在高等植物中普遍存在的简单扩散外,水-甘油通道也参与了该过程. ② PAHs通过气态、颗粒态沉降到小麦叶面角质层或直接通过气孔进入叶片. ③ 影响PAHs根系和叶面吸收的主要因素包括PAHs理化性质、植物生理状况、环境因素等. ④ 小麦根系吸收的PAHs可以向地上部转运,并且与辛醇-水分配系数(KOW)、蒸腾速率、土壤中氮的形态和浓度有关.主要问题:① 对于小麦叶片吸收的PAHs向基运输机理有待进一步研究. ② 农田生态系统中冬小麦往往遭受土壤及大气双重污染,根系吸收及叶面吸收分别对其体内积累PAHs的贡献尚不清楚.因此,需关注韧皮部、木质部在PAHs转运中所起的作用;利用同位素示踪、双光子激发显微镜等先进技术观察和跟踪PAHs如何进入小麦以及在小麦叶中的转移和分布,阐明PAHs叶面吸收的微观机理;注重大田试验研究,为揭示冬小麦对PAHs的吸收、积累及调控机理,同时也为有机污染地区生产安全农产品提供重要依据.
关键词多环芳烃    小麦    根系吸收    叶面吸收    转运机理    
Research Advances in Uptake, Translocation and Accumulation of Polycyclic Aromatic Hydrocarbons in Winter Wheat
SHI Taoran1,2 , TIAN Kai1,2 , BAO Huanyu1,2 , HOU Shaowei1,2 , LIU Xueping3 , WU Fuyong1,2     
1. College of Natural Resources and Environment, Northwest A & F University, Yangling 712100, China;
2. Key Laboratory of Plant Nutrition and the Agri-Environment in Northwest China, Ministry of Agriculture, Northwest A & F University, Yangling 712100, China;
3. School of Municipal and Environment Engineering, Henan University of Urban Construction, Pingdingshan 467036, China
Abstract: Due to continuous economic and social development and the predominant use of coal in energy consumption, emissions of PAHs in China has maintained a high level for years, which has resulted in serious PAHs contamination in atmospheric and soil environments. To evaluate the processes and mechanisms contributing to accumulation and regulation of PAHs in wheat, based on systematic analysis of characteristics and mechanisms of uptake, translocation and accumulation of PAHs in wheat, the present work focused on the effects of root and foliar uptake of PAHs. Previous studies have found that wheat root uptake of PAHs mainly includes active and passive processes, of which active process is a carrier-mediated, energy-consuming and H+-coupled symport process. Besides simple diffusion, which is especially prevalent for passive uptake in higher plants, PAHs could enter into roots via aquaglyceroporin. PAHs could enter into leaves by gas-phase and particle-phase deposition onto the waxy cuticle or via the stomata. Root and foliage uptake of PAHs are governed by the physicochemical properties of PAHs, plant species and environmental conditions. Acropetal translocation of PAHs by root is associated with KOW, transpiration rate, nitrogen form and concentration in soil. Current studies face some challenges. The mechanisms of PAHs translocating from leaves to root need further research. In addition, winter wheat always suffers from the double pollutions of soil and atmosphere under field conditions, and the role of root and foliar uptake of PAHs in the accumulation of PAHs in wheat has not been developed yet. Therefore, more efforts should be devoted to illustrating the effects of phloem and xylem in translocation of PAHs, using powerful techniques such as isotope trace and two-photon excitation microscopy to visualize and track how such compounds enter, move and distribute within wheat foliage, providing insight into PAHs foliar uptake. Paying more attention to field experiments to fully address root and foliar uptake of PAHs will provide logical proofs for revealing mechanisms of uptake, accumulation and regulation of PAHs in wheat and for the safety of agro-products growing in the PAHs-polluted areas.
Keywords: polycyclic aromatic hydrocarbons    wheat    root uptake    foliar uptake    transport mechanism    

PAHs(多环芳烃)是一类具有“三致”(致癌、致畸、致突变)效应的持久性有机污染物,由于其在自然环境中无处不在、对人体危害大而备受关注.我国是全球PAHs排放量最多的国家,2004年高达114 000 t,占全球PAHs排放总量的29%[1],直接造成大气、土壤等自然环境中PAHs含量升高.华北平原空气中ρ(PAHs)高达346 ng/m3[2],分别为伦敦和芝加哥的8.9和4.9倍[3-4].自然界90%以上的PAHs存在于表层土壤[5]. PAHs已经成为我国农田土壤中最为常见的污染物,无论是在东三省、京津地区,还是在长三角、珠三角地区,均发现农田遭受PAHs污染且呈持续恶化趋势[6-7].我国小麦种植面积约占农作物种植总面积的1/4,华中、华北和西北地区既是小麦主产区也是煤炭生产和消费大区,相当面积的小麦种植区位于众多的燃煤发电厂、炼焦厂、城市供热厂等燃煤企业周边区域.调查结果[8-12]显示,济南(7.6~ 495.2 μg/kg)、太原(161.5 μg/kg)和天津(177 μg/kg)小麦籽粒内PAHs含量均远高于美国加利福尼亚和西班牙加泰罗尼亚小麦籽粒内PAHs含量(10.3~27.9 μg/kg).通常情况下,膳食摄入是人体暴露PAHs的主要途径[8-9].小麦是我国北方和中原地区大多数居民的主食,成人日均消耗250 g左右,其中河南省成年居民日均消耗量达376~547 g[13].太原居民膳食暴露PAHs致癌风险较高,通过小麦摄入的PAHs占膳食摄入总量的48.3%~53.5%[12].因此,进行野外采样和模型模拟探讨PAHs在环境-植物系统中的富集规律,以及利用显微镜、光谱、热重分析和元素分析等技术探明PAHs在植物体内的行为,对于研究PAHs从土壤、大气等自然环境到小麦的吸收、转运、积累过程的机理和影响因素,预测农产品有机污染、降低农作物污染风险、确保农产品安全生产至关重要.

1 小麦对PAHs的吸收和积累

PAHs既可以通过土壤-根系也可以通过空气-叶面进入小麦体内[14],即根系从土壤中吸收PAHs进入木质部,随蒸腾流向茎叶传输的根系吸收;PAHs通过叶面角质层或气孔进入小麦体内的叶面吸收[15].有研究[16]认为,与叶面吸收相比,根系对疏水性有机物(HOCs)的吸收是主要的;也有研究[17]认为,由于PAHs易与土壤有机质结合,并且根系吸收后很难转运至地上部分,因此植物暴露器官中的PAHs主要来自叶面吸收.进一步探讨根系、叶片对HOCs的吸收以及在植物体内的积累、转移,对于治理PAHs污染土壤、确保食品安全、模拟潜在吸收量及进行风险评估等至关重要[18].

1.1 PAHs的根系吸收

小麦根系对PAHs的吸收包括主动和被动吸收两种方式.主动吸收量约占吸收总量的40%,并且受PAHs/H+协同载体的影响[19]. PAHs与H+形成共运对进入细胞内部后会导致细胞质pH降低[19],而细胞质pH通常呈中性或偏碱性,这就存在一个pH变化和稳定的过程.进一步研究细胞内pH自我调控机制对农产品安全保障和PAHs污染土壤修复具有重要意义.由于大多数有机污染物均系人工合成,植物体内没有相应的运输载体,因此大多数有机污染物进入植物体主要是通过被动运输.被动运输除了简单扩散,还与水-甘油跨膜输送蛋白通道有关[20].小麦根系对菲的吸收过程可分为快速吸收和慢速吸收两个阶段.当小麦根部浸到含有PAHs的营养液中,快速吸收立即进行,这一阶段主要受吸收作用、扩散作用和质量流量的影响.随后是一个慢相循环阶段,以载体为媒介且受新陈代谢的影响[19].与快速吸收阶段的吸收速率相比,慢速吸收阶段的吸收速率要低1个数量级[21],但是对于其他种类PAHs是否具有与菲相同的吸收特征尚不明确.用双光子激发显微镜(TPEM)直接观察PAHs被小麦根系的吸收、存储和代谢,发现蒽和菲最初结合在根系表皮,随后穿过表皮细胞到达皮层. PAHs呈放射状进入表皮,然而一旦接触皮层细胞就变为缓慢的横向运输[22].这可能与PAHs进入表皮、皮层细胞的原生质,并且滞留在原生质中,然后通过胞间连丝进入内皮层、中柱和韧皮部有关.

1.2 PAHs的叶面吸收

空气中的PAHs以气态或颗粒态沉降至植物叶面,一部分结合在叶面角质层的脂质中,扩散穿过脂质层,最终被韧皮部运输至其他部位;另一部分向叶片内部迁移,扩散至细胞间隙,然后再分配到邻近组织的液相或脂相中[23].此外,叶片表面还分布着许多气孔,这些气孔为有机污染物进入植物体提供了另一个途径[15].污染物从空气到叶片吸收包括3个步骤[24](见图 1):① 污染物穿过大气和叶之间的湍流带;② 污染物穿越边界层;③ 污染物与叶片表面反应.植物叶片角质层对PAHs具有一定的屏障作用,PAHs在角质层上会发生团聚现象,表明角质层对PAHs的吸附并非是均匀的[25].但经过一段时间后PAHs可以渗透至角质层,跨过细胞膜进入叶肉细胞,累积在液泡组织内[26]. Wild等[27]在观察玉米叶片内荧蒽在96 h的运动轨迹时发现,叶片中的荧蒽穿过上表皮蜡质和角质层后到达表皮细胞的细胞质,在这一阶段,荧蒽存在于叶片的5个部位,即上表皮蜡质-薄扩散层(约5 μm)、从上表层蜡质穿过角质层到达表皮细胞的细胞壁-厚扩散带(约28 μm)、上表皮细胞壁外表面、上表皮细胞壁内表面及上表皮细胞的细胞质. PAHs在叶片中的存储位置影响其在植物体内的迁移转化和最终归趋.如果滞留于表皮蜡质和角质层中,可能发生光降解、再挥发或从角质层脱落[28];如果进入到表皮细胞壁或者细胞质中,则易发生代谢作用[29].此外,Wild等[29]发现菲以气态沉降进入玉米叶片气孔,出现在气孔的保卫细胞,但是在气孔内表面和气孔下腔并没有检测到菲,因此推断菲没有通过气孔而是被叶蜡所吸收. Barber等[30]认为,当角质层较难穿透且气孔密度较大时,气孔吸收途径相对重要;而当角质层极易穿透时,气孔的作用几乎为零.目前,对于活体小麦叶片吸收PAHs的可视化实时追踪研究相对较少.小麦叶片对PAHs的吸收是角质层途径为主还是气孔途径为主,至今尚不清楚.

图 1 疏水性有机污染物从大气到叶角质层的吸收过程[24] Figure 1 The uptake process of hydrophobic organic compounds from air onto leaf cuticles
1.3 籽粒对PAHs吸收

由于PAHs本身的疏水特性,Briggs等[31]认为小麦籽粒内的PAHs主要来源于大气而不是土壤.然而,DU等[32]通过野外Lymimeter试验追踪14C标记的菲在小麦体内的积累发现,根系吸收的PAHs可以通过向顶运输进入茎、叶、籽粒和颖壳.有研究[33]发现,小麦籽粒内积累的主要为2~4环PAHs,并且萘含量最高.裸露的小麦籽粒对PAHs吸收速率大于有外壳的籽粒,可能是外壳阻碍了PAHs向籽粒的扩散.大田中的小麦籽粒从形成到收获大致需要一个月,对于气态PAHs的吸收处于动力学限制阶段且达不到平衡浓度[34].小麦籽粒PAHs浓度与接触大气的PAHs浓度有关,其关系受吸收时间和大田条件的影响[34],但是目前关于二者之间的关系缺乏定量研究,需要创建合适的动力学吸收模型,从而确定有效的途径降低籽粒引起的PAHs膳食暴露风险.农田中的小麦经常遭受土壤及大气双重污染,因此叶面吸收及根系吸收PAHs分别对籽粒积累PAHs的贡献是当前亟待解决的科学问题.

2 小麦对PAHs的吸收和积累的影响因素 2.1 根系吸收PAHs的影响因素 2.1.1 PAHs理化性质

PAHs能否进入植物根系,依赖于其KOW(辛醇-水分配系数)、水溶解度(S)、亨利系数(H)、分子量(MW)等理化性质.对于不同种类PAHs,根系对其吸收、转运速率不同[35]. Chiou等[36]提出了限制分配模型用于定量预测植物对有机物的积累:

$ {C_{{\rm{pt}}}} = {\alpha _{{\rm{pt}}}}[{C_{\rm{s}}}/({f_{{\rm{som}}}}{K_{{\rm{som}}}})][{f_{{\rm{pw}}}} + {f_{{\rm{ch}}}}{K_{{\rm{ch}}}} + {f_{{\rm{lip}}}}{K_{{\rm{OW}}}}] $ (1)

式中:Cpt为植物体内污染物的浓度,mg/kg;αpt为准平衡因子;Cs为污染物在土壤中的浓度,mg/kg;fpw为植物中无机组分的含量,%;fch为植物中碳水化合物的含量,%;flip为植物中脂类的含量,%;fsom为土壤有机质的质量分数,%;Kch为污染物在碳水化合物和水间的分配系数;Ksom为污染物在土壤有机质和水间的分配系数.

由式(1) 可知,KOW是植物根系吸收有机污染物的主要限制因子.有研究认为小麦根系对PAHs的吸收量随KOW的增加而增加[31],也有研究认为小麦根系PAHs富集系数与KOW没有线性关系[14],原因是大多数lg KOW>4的PAHs分配到根的表皮或土壤颗粒而不会被根系或木质部吸收.因此,KOW对小麦根系吸收PAHs的影响尚需深入系统研究. PAHs随着分子量的增加其挥发性降低[37].植物根系对不同Mw的PAHs吸收转运能力不同.小麦根系对4环PAHs吸收最多,其次是2环、3环、5~6环PAHs[14]. Wild等[22]观察同分异构体菲和蒽在小麦根系的迁移过程时发现,菲的吸收和迁移速率比蒽快.这可能与二者不同的水溶性有关:在25 ℃下菲和蒽在水中的溶解度分别为1.65、0.075 mg/L[38].

然而,对于一些PAHs理化性质精确的测量非常困难.定量结构-活性关系(quantitatives structure activity relationship QSAR)指化合物的分子结构与其活性之间的关系,目前已从个别的、定性的描述方式发展到一般的、定量的数学模型表达[39].利用定量结构-活性关系可以对PAHs理化性质、环境归趋和生物毒性进行预测,弥补数据的缺失,降低昂贵的测试费用.目前对PAHs的定量结构-活性关系研究主要集中在光解活性[40]、生物可降解性[41]和生物毒性[42]等方面,对其吸附-解吸等环境行为的研究相对缺乏.预测的理化性质参数代入多介质逸度模型,可得到理想环境状态下PAHs在多环境介质中的分配归趋,为了解PAHs在环境中的迁移转化提供了简便的途径.

2.1.2 植物生理状况

植物种类及其生理学特性(包括脂肪或水分含量及蒸腾速率等)都会影响植物对有机污染物的吸收[43].研究[44]表明,小麦根系对PAHs的吸收与根部脂肪含量、根表面积有关.吸附剂的极性也会显著影响其对有机物的吸附能力,小麦根细胞的极性与PAHs吸收速率呈负相关[45].植物体主要由水、脂肪、碳水化合物、蛋白质、纤维素等物质构成,这些成分对有机污染物的亲和力不同[46].研究[47]表明,KOW < 10的有机污染物,根系水吸收占主导作用(85%以上);KOW=10的有机污染物,根系水和脂肪作用各占50%;KOW>1 000的有机物,植物对有机污染物的吸收几乎都来自根系脂肪对有机物的分配.植物不同生育期由于生命代谢活动强度不同,吸收污染物的能力也不同.在不同生长期小麦各组织器官低环、中高环PAHs分布有显著差异[48].此外,不同的根系类型、根表面积、根系分泌物、菌根细菌等在种类和数量上的差异导致根际对PAHs的吸收、降解能力不同[49].

2.1.3 土壤理化性质

YANG等[50]发现,土壤DOM(可溶性有机质)不仅能明显地促进小麦对菲的吸收和富集,而且还能促进根系吸收的菲向地上部转运.这可能是由于DOM改变了PAHs的理化性质,如水溶解度和KOW,从而提高了PAHs的生物有效性,进而促进了植物对菲的吸收[50].但是小麦根系吸收PAHs与土壤有机碳(SOC)含量呈负相关(P < 0.01)[14].低的pH促进根吸收PAHs,研究[20]表明根系对菲的主动吸收是以H+共运方式进行的. K+也会促进小麦根系对菲的吸收,K+激活了质膜H+-ATPase[44].植物对PAHs的吸收与土壤中PAHs的浓度和植物组分有关[51],研究表明[14]小麦根中PAHs浓度与土壤中PAHs的浓度呈正相关.另外,阳离子表面活性剂能显著增强土壤对有机污染物的吸附[52],而且能够抑制作物吸收土壤中的PAHs[53].土壤粒径组成影响其对有机污染物的吸附和利用能力.粗砂和黏粒对芘的吸附能力较大,细砂和粉砂相对较小[54].此外,土壤中氮的浓度和形态也会影响小麦根系对PAHs的吸收[55].

2.2 叶面吸收PAHs的影响因素 2.2.1 PAHs理化性质

植物叶片对PAHs的吸收和转移与PAHs本身的理化性质有关,如环数、分子量、水溶解度、辛醇-水分配系数、辛醇-气分配系数、形态(气态/颗粒态)、亨利系数等.气态的PAHs容易在叶片角质层扩散而被吸收,而大部分颗粒态PAHs只是嵌入到角质层,很容易被脱附[56].蒽和苯并[k]荧蒽混合喷施对生菜地上部分产生的积累效应和单独喷施有明显差异[57].车前草叶内部PAHs含量随PAHs分子量的增加而减少[58];然而也有研究[59]认为,植物叶中PAHs以5、6环为主,根中以2~4环为主.挥发性、半挥发性有机污染物在植物叶片和空气之间的分配与其辛醇-气分配系数密切相关[43].

2.2.2 植物生理状况

不同种类植物叶片性质存在差异,如形态、叶面积、角质层、叶片数量、气孔大小及密度、叶毛长度与密度、疏水性等[60].植物叶片拦截颗粒态PAHs与其叶向、叶面积、叶毛有关[24].研究表明,植物暴露器官中的PAHs主要来自叶的吸收[17],影响叶片角质层吸收PAHs的主要因素是暴露于大气中的叶面积[61].此外,叶毛可以提高叶片清除和黏附大气颗粒物的能力,因为它们具有更大的表面积并且会在叶表面的边缘形成相对静态空气[56].然而也有研究[62]表明,表面光滑的叶片比表面粗糙的叶片更易于吸附颗粒物.因为叶子越粗糙,防水性能就越好,所以对叶子表面颗粒物的黏附作用减弱[56].因此,叶毛对叶片吸收大气颗粒物的影响还没有统一的结果.叶脂含量也是影响植物吸收和滞留大气持久性有机污染物(POPs)的一个重要的因素[52].在这些因素中,哪些是影响PAHs穿过角质层被小麦吸收的主要因素有待进一步研究.

2.2.3 环境因素

植物从空气中吸收PAHs受温度、空气中污染物的浓度、暴露时间等影响. PAHs通过气孔在叶片和大气之间交换与大气温度有关[63],因为温度影响气孔的开启和闭合.在温度较低的秋冬季节,PAHs由大气向植物迁移,而在温度较高的夏季,部分PAHs又通过挥发作用回到大气中[64].叶面对PAHs的吸收量还取决于叶面周围大气中PAHs的浓度[65].由于暴露时间的不同,老叶积累的PAHs量往往大于新叶[66].

3 PAHs在小麦体内的分布和迁移 3.1 向顶运输

植物根系吸收的有机污染物一部分固定在根的脂质中,一部分则穿过根系不透水硬组织带进入内表皮层到达管胞和导管组织,并通过木质部随蒸腾流向地上部分迁移,最终在茎叶中分布[43].小麦根系吸收的PAHs可以通过向顶运输进入茎叶[14].有研究[67]认为,蔬菜地上部大分子量PAHs主要来源于根系的转运.小麦地上部不同环数的PAHs的分布特征与大气中的PAHs的分布有显著的差异,表明地上部PAHs来自于根系的转运[14].

小麦对PAHs的向顶运输与PAHs的理化性质有关,芴倾向于在小麦根部积累,而菲被转运到地上部分[68].有研究[14]表明小麦根吸收PAHs向地上部转运与lg KOW呈负相关. lg KOW≤1的有机物易溶于水,可以在木质部和韧皮部流动;1 < lg KOW≤4的有机物易被根系吸收,可以在木质部流动,但不能在韧皮部流动;lg KOW>4的有机物可以在根部大量积累,但不能向顶运输.因此,1 < lg KOW≤4的有机污染物更适合于植物修复[69].向顶运输还与植物的蒸腾速率[70]及土壤中营养盐有关,如小麦根吸收PAHs后向地上部运输与土壤中氮的浓度和形态有关[55].

3.2 向底运输

由于PAHs较高的疏水性和较低的溶解性,植物根系表皮吸收后难以运输到根的内部或木质部[71],因此推断植物体内的PAHs可以通过地上部吸收后运输至根部.在土壤菲浓度很低的情况下,三叶草和黑麦草根部检测到高浓度的菲,很大程度上证明地上部吸收的菲被转移至根部[72].然而也有研究[51]表明,植物(如大豆、空心菜等)地上部从大气中积累的菲和芘没有被运输到根部.用同位素示踪法研究豌豆体内荧蒽的转运发现:荧蒽通过韧皮部存在向基、向顶运输,尤其是在植物新生部位如茎尖及根尖积累[73].目前,小麦叶面吸收PAHs是否会向根部运输还没有明确的结论,有待进一步的研究.

4 结论

a) 目前,关于小麦对PAHs吸收和转运的模型在风险评价、植物修复等方面应用得很多,然而,缺乏PAHs在小麦体内转运过程的直接证据.研究韧皮部、木质部运输动力学对确定可食部分-小麦籽粒积累的PAHs主要来自根系吸收还是叶片吸收,从而采取有效的农艺措施阻控PAHs进入食物链是必要的.

b) 小麦处于自然状态下PAHs是如何进入其叶片,如何在叶片中转移和/或与叶肉组织结合尚不清楚.采用先进技术探讨小麦叶面吸收、转运PAHs的微观机理,如利用同位素示踪法、双光子激发显微镜等技术跟踪和观察PAHs在小麦叶片的吸收和转移,有望为宏观调控植物吸收PAHs获得安全农产品提供科学依据.

c) 大多数研究致力于室内盆栽试验,因为受自然环境等不可控因素的影响小于田间试验而利于机理的研究,但是植物吸收PAHs的大田试验的经验对于完全理解植物-环境体系的宏观关系也是必要的.探讨影响PAHs在小麦体内的吸收、转运和富集过程的因素,除了污染物性质、植物特征和土壤性质(尤其是土壤有机质)外,小麦生长环境的污染史也需要考虑在内.

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