【作者】 洪春来；

【导师】 魏幼璋；

【作者基本信息】 浙江大学 ， 植物营养学， 2004， 硕士

【摘要】 蔬菜是人们日常生活中不可缺少的食物，蔬菜的生产对保证城市经济发展、社会稳定和人们身体健康起着重要的作用。随着生活水平的提高，人们对清洁蔬菜、无污染蔬菜的要求日益强烈。城市郊区既是蔬菜的主要生产基地，又是城市固体废弃物（垃圾、淤泥等）的主要容纳场所，而且随着工业“三废”的污染和机动车尾气的排放，污水灌溉及农药、除草剂和化肥等的使用，污染了土壤，使蔬菜地铅污染加重，铅在植物根、茎、叶及果实中的大量积累，不仅影响植物的生长和发育，而且会进入食物链，危及人类的健康，因此菜园土壤的重金属铅污染日益受到人们的关注。本试验选用了当地有代表性的叶菜（小白菜）、茎菜（芹菜）、果菜（辣椒）各一种，采用了室内培养试验、溶液培养和土培试验，初步探讨了外源铅在两种菜园土壤的吸附-解吸特性和转化及pH对铅解吸的影响等铅在土壤中的物理化学行为；研究了铅对蔬菜作物生长发育的影响，包括根系形态及体内SOD、MDA，Pro及对铅胁迫的响应及蔬菜根系耐铅胁迫的机制；明确了铅在三种蔬菜体内的吸收积累规律及铅的植物毒性临界值和食品安全土壤临界指标，取得的主要结果如下： 1．两种菜园土壤（青紫泥和黄松土）对铅的吸附等温线均可用Langmuir，Freundlich，Temkin方程来描述，相关系数均为0.90以上，达到极显著水平。由Langmuir方程求得青紫泥和黄松土对铅的最大吸附量分别为14285.7mg／kg，12500mg／kg。而且菜园土壤对铅的解吸量随其相应的吸附量的增加而增加，两者之间有很好的线性相关，相关系数为0.891，0.955，达到极显著水平。连续三次解吸过程中以第一、二次解吸为主，第三次解吸量很小。解吸液pH对两种菜园土壤的铅解吸有很大的影响，随着pH降低，铅的解吸量逐渐增加，当pH≤4时，铅的解吸量迅速增加。 2．随着培育时间的推进，外源铅（Pb（NO₃）₂）的有效性不断降低，当培育12周以后，铅在两种菜园土壤中的转化基本达到了动态的平衡，有效铅含量不再减少。两种土壤对铅都有很强的吸附能力，达到平衡后，约有90％以上的铅不能被1mol／L中性NH₄NO₃浸提。 3．生长介质中低浓度的铅（水培≤1mg／L，土培≤400mg／kg），促进小白菜与芹菜根系发育，增加地上部分的生物量，但随着处理浓度的提高，铅对蔬菜作物的毒性慢慢显现出来，表现为根系发育受阻，根尖发黑，侧根和根毛数减少，主根长，根表面积，根截面积，根体积下降，叶片失绿黄化，叶片容易脱落。辣椒花期延迟，三种蔬菜作物各器官的生物产量（鲜重）减少。当土壤外加铅浓度达到300om叭g时，辣椒已经枯萎死亡.三种蔬菜对铅的耐性表现为芹菜>小白菜>辣椒。4.三种蔬菜根系SOD酶活性随着铅处理浓度的提高表现为先上升，后下降。MDA含量在低铅处理浓度下积累不明显，随着铅处理浓度的升高逐渐上升，而根系脯氨酸的含量则随着铅处理浓度的提高持续的增加。5.铅在根细胞内主要与细胞壁结合，占了90%以上，并且盐酸提取态和醋酸提取态等难溶态占了绝大多数，二者合计也达到90%以上，减少了铅对细胞膜的直接毒害，限制了铅由根部分向地上部分的迁移，减少了对其它器官的毒害。蔬菜对铅的这种耐性，同时增加了铅对人类健康威胁。6.随着铅处理浓度的提高，三种蔬菜各器官中的铅含量逐渐升高，其中以根部含量最高，其次为叶、茎，果实中铅的含量最低，溶液培养和上培试验表明，随着铅处理浓度增加，根系铅含量远大于地上部含量，但由于地上部的生物产量远大于根系，因而地上部分吸收的铅总量大于根系。在相同处理浓度下，由于青紫泥铅的生物有效性大于黄松土，对蔬菜毒害也更大。在同样处理水平下，三种蔬菜作物，其可食部位铅的含量存在很大的差异，表现为小白菜>芹菜>辣椒。7.三种蔬菜作物可食部分的产量与水培铅处理浓度及两种土壤中铅浓度（全童或有效态）呈极显著的负相关。当小白菜地上部分，芹菜茎，辣椒果实减产10%时，通过相关方程计算，在水培条件下，小白菜、芹菜、辣椒的临界铅浓度分别为1 .56m留L、3.55m留L、0.slm叭。在盆栽条件下，小白菜、芹菜、辣椒在相应的青紫泥土壤全铅临界水平为goo.3mg/kg、936.2mg/kg、423.0m留kg;有效铅含量Zo.98mg/kg，、ZI.94mg/kg、l.55mg/kg;在黄松土上的全量铅临界值为1134.9m叭g、14%.sm叭g、443.6m留kg，有效态铅临界值为18.54mg/kg、30.78mg/kg、l.18mg/kg。8.蔬菜可食部位的产量与其组织中铅含量呈显著或极显著的负相关。当小白菜，芹菜，辣椒可食用部位减产10%时，在水培条件下，小白菜、芹菜、辣椒对应组织中铅的含童水平分别为24.71 mg/kg、28.25 mg/kg、0.567mg/kg;在青紫泥栽培条件下为13.1 mg/kg、3.83 mg/kg、0.734 mg/kg;在黄松土培养条件下为31.7 mg/kg、30.0 mg/kg、0.854 mg/kg。9.三种蔬菜作物可食部铅含量与水培溶液铅浓度及两种土壤铅浓度（全量或有效态）呈显著的正相关。以可食部位铅含量达到食品卫生标准（0 .Zmg/kg）为限值，在水培条件下，小白菜、芹菜、辣椒临界铅溶液浓度为0.320 mg/kg、1.42 mg/kg、0·397 mg/kg;土培青紫泥全量铅临界值为537.Zm眺g、595.sm留kg、314.sm留kg，有效态含量为更多还原

【Abstract】 As indispensable food for people’ s life, vegetables also play important roles for the health of human beings. With the improvement of people’ s living standard, the demands for "clean vegetable" or "unpolluted vegetable" become stronger and stronger. Suburbs are areas for the production of vegetables and the disposal of solid refuse by means of landfill as well. And with the pollution of industry exhaust gas, waste residue, waste water and the let of the epilogue of the cars, soils are polluted by the irrigation of waste water, the pesticide, the herbicide and chemical fertilizers. Especially lead pollution in vegetable farm soils is more serious. The accumulation of the heavy metal-Pb in the root, stem, leaf and fruits not only affect the plant growth and development, but also can come into food chains to endanger the health of human beings. Therefore more and more attentions are paid to the heavy metal-Pb pollution in the graden soils. In this study, three representation vegetables-Chinese cabbage(leaf vegetable), Celery(stem vegetable), Pepper (fruit vegetable) were selected. We examined Pb’s adsorption and desorption characteristics, the transformations and the influence of pH for Pb’ s desorption-Pb physical chemistry action in the soil with the addition of Pb in two garden soils by the room culture experiments. Also, by hydroponic culture we studied lead’ s influence on growth and development of vegetable crops, including of the root morphology and the change of SOD, MDA, Pro under Pb’ s stress in the plant. And the thresholds for phytotoxicity or soil toxicity of Pb were studied by soil culture experiments. The main results obtained were summarized as follows: 1.The Isothermal curves of Pb of the adsorption on two garden soils(Qingzi garden soil and Huangsong garden soil)could both be described by either Langmuir, Freundlich or Temkin equation(R>0.90)for each equation, and arrived highly significant. Adsorption maxima calculated from the Langmuir equation were 14285.7 mg/kg, 12500mg/kg soil for Pb. Adsorption Pb by two garden soils increased with increasing adsorption respectively. There were highly positive linear relationships between adsorption and desorption(r=0.891, 0.955), arrived highly significant level.2.The phytoavailability of added Pb (Pb(NO3)2) deceased progressively with the incubation time. After 12 weeks, their transformations in two garden soils reached dynamic equilibrium,and their phytoavailability no longer decreased. After the equilibrium, about 90% Pb could not be extracted by 1 mol/L NH4NO3 (pH7.0)3. Lower concentration Pb in the medium accelerated the root development of Chinese cabbage and Celery, increased the biomass of the shoot. But with the increasing of the treatment concentration, Pb toxicity to vegetable crop gradually showed, and resulted in the inhibition of roots development. Root tip became black, the number of lateral root and root hair decreased, radical length, the root surface area, root volume decreased, leafs became yellow and easily fell off. Also, the florescence of Pepper declayed. All organs’ biomass (fresh weight) of three vegetables decreased. Pepper died when adding 3000mg/kg Pb in soils. The tolerance of three vegetables for Pb is Celery>Chinese cabbage>Pepper.4. The activities of dismutase(SOD) of three vegetables in roots first rose, then declined. While the accumulation of melondialodehyde(MDA) content was not significant when lower Pb concentration. With increasing Pb concentration, MDA content increased gradually, while Pro content persistent increased.5 .The tolerance mechanisms of Pb mainly show that Pb in roots cell combined with cell wall, reached over 90%. Also, HCl-extractable Pb and HAc-extractable Pb became the dominative forms, reached over 90%, so decreased the Pb direct toxicity to cell membrane, restricted Pb transformation from roots to shoots, and decreased the toxicity for other tissues. 6.With the increasing of Pb treatment concentration, Pb content of all organs in three vegetables gradually improved, highest in ro更多还原