【作者】 李正文；

【导师】 潘根兴；

【作者基本信息】 南京农业大学 ， 土壤学， 2003， 博士

【摘要】 随着人类活动诸如采矿，施肥和和废水利用等，重金属在土壤中的积累呈逐渐增加的趋势，重金属污染会给人类，环境和农业生产带来严重后果。重金属污染具有不可逆性、长期性及隐蔽性等特点，土壤一旦受到污染，在短期内很难得到改善和恢复。据估测，1998年全国污染的耕地面积约占总耕地面积的1／5，其中重金属占污染面积的30～40％，尤其是在城市郊区生产的粮食、蔬菜、水果等食物，Cd、Cr、As、Pb等超标严重。例如太原污染农田中粮食重金属含量超标率60～80％，有汞米、铅米恶性现象发生，导致不能食用。并初步揭示出污染的主要原因是污灌和局部矿冶活动。重金属主要通过土壤进入植物并且直接或者间接地进入人体而对有机体产生毒害作用。减少重金属进入食物链的可能途径之一是调节土壤中重金属的生物有效性，二是利用或培育对重金属吸收量少的作物栽培品种。国内外众多研究者广泛研究了重金属与土壤各组分间的反应；土壤中重金属的赋存形态，生物活性评价，影响生物活性因素，施用各种化学改良剂对降低重金属进入食物链的效果及过量重金属对植物生理生化代谢的影响，也注意到了不同植物种类和植物品种间吸收重金属的差异及生物有效性。我国有较多的对土壤-作物系统重金属分布关系的案例研究报道，但仅停留在静态相关分析上。 本文研究不同性质土壤-水稻系统中重金属的土壤环境释放与迁移(动态生物有效性)和水稻吸收、积累及其器官间分布的动态特点与数量规律，阐明不同生长时期不同重金属在土壤-水稻系统中生物有效性的动态变异特征，建立土壤-水稻系统重金属生物有效性的定量表征的数学模型，为安全优质农产品生产中重金属污染物全程控制，为估计和评价我国稻米消费中食物重金属污染物摄取风险以及区域和国家食物安全评估提供科学依据和技术参考体系。通过大田试验和盆栽试验研究了不同水稻品种积累重金属Pb、Cd的差异以及土壤-水稻系统中植株吸收积累Pb、Cd的生育期动态及成熟收获时Pb、Cd在水稻各器官中的分布与分配，并研究了水稻全生育期中土锡处理下不同水稻品种对两种土壤中铅、镐的吸收及其生育期动态壤重金属各形态及有效态变化，主要结果如下: 1.在江苏省昆山市农业科技示范园区，以太湖地区主要农业土壤之一的乌栅土和57个江苏省当前大田栽培的水稻品种为对象，进行了水稻对土壤重金属吸收积累的大田试验.结果表明，57个水稻品种籽粒的Pb、Cd含量的变化范围分别为0.337土0.078、0.099土0.039mgkg’，，指示不同水稻品种对同一土壤中Pb、cd的吸收及其在籽粒中的积累存在有显著的差异，这种差异对籽粒Cd的影响较强，Pb较弱.杂交水稻比常规水稻有更强的吸收Pb、Cd的能力.水稻对Pb、Cd的吸收积累存在协同作用.大部分样本的Cd含童超出USEPA推荐的人类摄取的籽粒临界含量，少量样本籽粒Pb含蚤超出国家粮食Pb限童标准。 2.以取自中国科学院鹰潭红壤生态站的红壤和取自江苏省昆山市玉山镇农业科技示范园区水稻土(乌栅土)和前期试验中对Pb、Cd吸收有显著差异的苏香粳1号和99一22两个品种为对象进行盆栽试验.结果表明，水稻品种对重金属的积累存在有显著差异，苏香粳l号籽粒累积的Pb、cd显著高于99一22;外加cdl、Zmgkg一土对水稻生物量和籽粒产童没有明显的影响，但极显著增加水稻Cd贮量和植株含全.外加cd促进Pb在水稻体的积累，加cd Zmgkg-，显著增加水稻植株和籽粒Pb的含量.不同水稻品种籽粒对不同土壤中Cd水平的响应关系、转运效率也存在差异.水稻植株和籽粒在红壤中累积的Pb、Cd高于水稻土. 3.水稻中Cd迁移能力大于Pb.说明Cd相对容易在水稻中积累，而Pb不易在水稻中积累.Pb、Cd在水稻不同器官的含量分布是:才卜茎叶>籽粒.不同生长发育期，重金属在水稻各器官的分配和比例不同，水稻植株Pb、Cd含量为前期>后期. 4.红壤和水稻土中Pb、cd各形态含量存在有明显的差异，红壤中Pb、Cd的MgC12提取态、NaA。提取态含量显著高于水稻土;红壤中HCI和DTPA提取态Pb、Cd含童均显著高于水稻土.水稻积累的Cd总量与土壤的MgCI:提取态、NaAc提取态、HCI提取态以及DTRA提取态含量存在显著依变关系.不过，水稻积累的Pb、Cd总童只占土壤有效态库的很小一部分.水稻生长对土体Pb、Cd的形态分布影响甚微. 5.水稻Pb、Cd总童是随生育期的延长而逐渐增加，在生育前期和后期有一个明显积系速度较快的阶段;Pb含量在水稻生长前期有一个上升过程，然后随着生育期的延长下降;Cd含童的变化是随着水稻生育期的延长呈下降趋势.两个水稻品种对摘要重金属的积累差异在整个生育期普遍存在。更多还原

【Abstract】 The increasing concentration and subsequent accumulation of heavy metals in the soil due to human activities such as mining, fertilizers, and sewage waste may have serious consequences for mankind, environment and agriculture. Heavy metals can enter the plants by way of soil and directly or indirectly enter the human body leading to health risks. One of possible ways to reduce the amount of heavy metals entering the plants is to control the uptake by plant roots, in turn, to control the mobility in soils by pH control and addition of organic matter. Another alternative strategy may be the use of species or cultivars having low ability of uptake or translocation specific toxic metals.This study dealt with heavy metal dynamic bioavailibility in soil-rice system by field and pot experiments. The works included the dynamics of heavy metal uptake and accumulation during rice growth period, heavy metal distribution in organs, and heavy metal level of seed at maturity, as well as the dynamics of heavy metal availability in rhizosphere soil. The main results obtained are as follow:1. Field experiment of heavy metal uptake by different cultivars showed that the grain concentrations of Pb, Cd of 57 rice cultivars varied in the range of 0.337 + 0.078, 0.099 + 0.039mg.kg-1 respectively, demonstrating remarkable inter-species difference in heavy metal accumulation in rice grains. Hybrid cultivars had a high ability of uptake Pb and Cd. Co-uptake and accumulation of Pb and Cd in grains was observed for the rice cultivars. The Cd concentration of most of the samples was found over the permissible limitrecommended by USEPA. However, only a few samples showed Grain lead content over national grain standard.2. A pot experiment was conducted on uptake of Pb and Cd under Cd spiking by 2 cultivars in two soils differing in soil properties under continuously submerging condition. The result showed that significant difference of Pb ,Cd uptake and accumulation existed between two cultivars, Cultivar Suxiangjing No. 1 grown in both soils had a higher content of Pb and Cd than the cultivar of 99-22, Although there was no obvious influence on the biomass and yield of rice and no toxicity on rice by spiking Cd to soils, but grain Cd of two cultivars increased sharply with Cd spiking.. Spiking Cd increased grain Pb content. Both cultivars growing on red soil accumulated more Pb, Cd than these of paddy soil with and without Cd spiking. Thus, the bioavailability of Pb, Cd in red soil was higher than that of paddy soil.3.Pot experiment revealed that translocation of Cd was higher than Pb in plant organs. The concentration order of Pb and Cd in rice organs was root > stem and leaf > grain. The distribution and proportion of heavy metals in different organs of rice was different. The content of Pb, Cd of rice plant in early stage was higher than that in later stage.4. Pot experiment showed that the distributions of chemical speciation of Pb, Cd in two soils were obviously different. The amount of Cd accumulated by rice was positively related to fractions extracted by MgCl2, NaAc, HCl and DTPA respectively. The amount of Pb and Cd uptaked by rice only occupied small proportion of the soil total. The change of available concentration was a dynamic process during rice growth. In the whole growth of rice the rice, soil mobility of Pb and Cd was hardly affected by rice growth.5. The total accumulation of Pb and Cd in rice increased with growing time. While the content of Pb and Cd in rice decreased with growing time. The interspecies difference in Pb and Cd uptake was consistently observed in the whole growing period of rice. The content of Pb and Cd in plant was determined by the bioavailability of heavy metal in the soils, the interaction of soil and rice cultivar.更多还原