【作者】 赵转军；

【导师】 南忠仁；

【作者基本信息】 兰州大学 ， 环境科学， 2010， 博士

【摘要】 在农业土壤的污染物中,重金属污染物所引发的农产品安全问题已经受到了全球各界的高度关注。长期的污水灌溉、化肥使用以及工业废渣的堆放是造成重金属元素在农用土壤表层积累的最主要原因。河西走廊是我国干旱区绿洲农业最发达的区域,在该地区,以有色金属冶炼和化工业为主的第二产业的发展对当地经济起到了极大的推动作用,但对环境的负面影响也非常突出。在原本匮乏的水资源利用条件下,污水灌溉现象在当地普遍存在,加之农药和化肥的大量使用,造成重金属污染物残存在动植物以及人类的生存环境中,对人类健康构成严重威胁。在河西走廊地区,重金属在土壤-蔬菜系统中的化学污染行为研究工作开展起步较晚,系统的试验研究以及元素复合污染研究几乎是一片空白。本文通过野外盆栽试验,选择干旱区绿洲土壤,以油菜、芹菜、胡萝卜三种蔬菜为供试材料,以Cd、Pb、Zn、Ni四种重金属为基线,探讨与Cd共存的Pb、Zn、Ni在分别与之作用时的土壤、蔬菜污染化学行为表现,掌握特殊生境对四种重金属单独作用和共存作用下的影响,明确蔬菜对Cd及其共存元素的吸收和累积特征,并通过合理的数理统计分析构建土壤重金属总量和重金属形态、蔬菜吸收之间的关系模型,为建立干旱区土壤重金属在土壤-蔬菜系统中迁移转化基础数据库、改善干旱区绿洲土壤环境质量、控制蔬菜重金属污染、建设绿色蔬菜生产基地、保障农产品质量安全提供理论支撑。论文主要研究结果如下：(1)在未添加外源污染的干旱区绿洲土壤中种植油菜、芹菜、胡萝卜三种蔬菜后,土壤中Cd主要以铁锰氧化物结合态存在,可交换态含量和比例非常小；而在添加可溶性Cd后,三种蔬菜土壤中Cd的可交换态对外界浓度胁迫响应最大,残渣态对胁迫响应最小,说明试验浓度下蔬菜从生长到成熟的短期过程对可溶性Cd的固定作用不大,更多的量以相对活性的状态参与了土壤-蔬菜系统中的各种迁移。五种形态中碳酸盐结合态是Cd在各种胁迫水平下的主要存在形态。(2)在添加了Pb、Zn、Ni的Cd污染土壤中,Cd元素的形态分配规律和单独作用时一致。它们对Cd的作用是：Pb会提高Cd在油菜、胡萝卜土壤中的活性,抑制Cd在芹菜土壤中的活性；Zn会抑制Cd在油菜和胡萝卜土壤中的活性,提高Cd在芹菜土壤中的活性,Ni会降低油菜和芹菜土壤中Cd的活性而提高胡萝卜土壤中Cd的活性。三种组合下,Cd和添加元素活性的对比结果是：Cd>Pb,Cd＞Zn,Cd>Ni。(3)三种蔬菜土壤中,单Cd胁迫下,土壤中Cd的可交换态、碳酸盐结合态、铁锰氧化物结合态、有机物结合态和胁迫量显著相关,它们的变化方程以线性模型为主,其次是幂大于1的乘幂模型。而添加了Pb、Zn、Ni的Cd污染土壤中：加入Pb后,三种土壤可交换态、碳酸盐结合态、铁锰氧化物结合态Cd以及油菜土壤中的有机物结合态Cd和胁迫量显著相关,除了胡萝卜土壤中碳酸盐结合态Cd呈对数模型变化外,其余各形态均以线性和幂大于1的乘幂模型变化；加入Zn后,土壤中可交换态、碳酸盐结合态、铁锰氧化物结合态、有机物结合态Cd和胁迫量显著相关,描述形态随胁迫量的变化模型时,除了油菜土壤中可交换态和有机物结合态Cd以及芹菜土壤中铁锰氧化物结合态Cd的拟合方程分别为幂大于1的乘幂形式、S型曲线、对数形式外,其余形态Cd的拟合方程均为线性。加入Ni后,除了残渣态的其他四种形态Cd均和胁迫量显著相关,各形态Cd的变化以线性模型为主,其次是对数和幂小于1的乘幂模型。(4)Cd单独胁迫下,当浓度较低时,抑制作用主要体现在蔬菜各部分重量和地上部长度上,当胁迫浓度较高时(Cd＞4.9mg／kg),其对地下部长度的抑制作用比较明显。三种蔬菜对Cd胁迫的耐受程度排序为：油菜>胡萝卜>芹菜。Cd在油菜和胡萝卜各部位积累量分布规律为：地上部>地下部,芹菜正好相反。三种蔬菜各部位积累Cd量的大小排序是油菜>芹菜>胡萝卜。油菜各部位、芹菜地下部对Cd具有明显的富集作用,阻碍油菜迁移Cd的主要场所在地下部-地上部迁移界面,阻碍芹菜迁移Cd的主要场所在土壤-地下部迁移界面。胡萝卜对Cd无明显的富集,各界面在富集转移Cd方面的能力相当。三种蔬菜对Cd的富集能力大小为：油菜>芹菜>胡萝卜；转移能力大小为油菜>胡萝卜>芹菜。(5)在添加了Pb、Zn、Ni的Cd污染土壤中种植三种蔬菜,发现当Pb浓度较高时(Pb≥450mg／kg),可以弱化Cd对三种蔬菜生物量的抑制作用；Zn可以弱化Cd对芹菜,胡萝卜地上部长度的抑制,较高浓度(Zn≥500mg／kg)时也可以弱化Cd对芹菜地下部鲜重以及胡萝卜地上部鲜重的抑制；Ni会弱化Cd对芹菜地上部长度和地上部鲜重的抑制,较高浓度(Ni≥600mg／kg)时也会减弱Cd对芹菜地上部鲜重、胡萝卜地上部长度和地上部鲜重的抑制。(6)三种元素的介入没有改变Cd在蔬菜体内的分配规律,但造成了蔬菜对Cd积累量、富集能力和转移能力的显著差异,这些差异的产生是介入元素的作用结果。Pb、Zn、Ni对Cd在三种蔬菜中的积累作用影响因浓度、蔬菜种类、蔬菜部位的不同而出现拮抗或者协同。对比Cd、Pb、Zn、Ni四种元素在同种蔬菜中的富集、转移系数可知,Cd是最容易在蔬菜中富集并且转移的元素,其次为Zn,Ni和Pb相对较差。(7)外源Cd总量对蔬菜各部位积累Cd的影响可以用线性模型、乘幂模型(幂小于1)和对数模型来描述,后两种模型提示了蔬菜(油菜地上部以及芹菜各部位)适应外界浓度干扰时采取了自我保护措施。而Cd在蔬菜内部迁移时的变化方程提示,油菜和芹菜中Cd的迁移动态为幂小于1的乘幂模型,而胡萝卜中为线性模型,这可能是前两种蔬菜耐Cd性较强的原因之一。添加了Pb、Zn、Ni的Cd污染胁迫下,蔬菜积累Cd的变化仍然可用线性、乘幂、对数模型描述,但其中乘幂模型的幂基本均≥1(Cd,Pb复合下油菜,芹菜各部位以及胡萝卜地下部积累Cd; Cd, Zn复合下油菜地下部积累Cd; Cd, Ni复合下芹菜地上部和胡萝卜地下部积累Cd),说明复合作用下胁迫浓度越高,这些蔬菜相应部位积累Cd的增量越大。Cd与其他三种元素复合作用下蔬菜内部迁移动态可用线性、对数和乘幂模型来模拟。其乘幂模型的幂均接近1；对数模型适用于Cd, Zn复合以及Cd, Ni复合的Cd在胡萝卜内部的迁移。更多还原

【Abstract】 Among pollutants in agricultural soil, safety issues of agro-products caused by heavy metal pollutants have attracted high attention from all walks of life in the world. Long term sewage irrigation, fertilizer use, and piled-up industrial solid waste are the primary reasons for metallic elements’accumulation in surface layer of agricultural soil. Hexi Corridor is the most developed area on oasis farming in arid region of China. In this area, development of secondary industry, which gives priority to nonferrous metallurgy and chemical industry, plays a greatly improving role in local economy increase, but such development also has a distinctly adverse impact on environment. In the originally water-short conditions, sewage irrigation is used widely in locality, along with slathering of pesticide and fertilizer, thus, making heavy metal pollutants remain in bodies of animals and plants, and living environment, as poses severe threats to human health.Researches on heavy metal behaviors of chemical pollution in soil-vegetable system were started late in Hexi Corridor, leaving empty on studies of systematic experiments and multi-element pollution. Pot experiment, for which coles, celeries and carrots are experimental materials and the four heavy metals, Cd, Pb, Zn, and Ni, are the baseline, is conducted in oasis soil of arid regions. By the experiment, the paper explores behavioral expressions of pollution chemistry of soil and vegetables effected by Pb, Zn, Ni while coexisting with Cd; finds out the special habitats’effect on the single and combined contamination of these four elements; figures out vegetables’absorption and accumulation features to Cd and other coexistent elements. With statistical analysis, the paper builds a relation model between amounts and forms of soil heavy metals and vegetable absorption, offering theory supports to setting up basic database of heavy metals’transference and conversion in soil-vegetable system of arid districts, improving environmental quality of oasis soil, dominating heavy metal pollutions on vegetables, building green-vegetable production base, and guaranteeing qualities of agricultural products safety. The primary results are as follows:1) In oasis soil without contamination, coles, celeries and carrots were planted. Then, Cd in the soil mainly existed in Fe-Mn oxides fractions, while the proportion of exchangeable fractions was quite small. Soluble Cd added into soil, we found that exchangeable fractions response most strongly to concentration stress and residual forms response most weakly to such stress in the three-vegetable soil, demonstrating vegetables from growth to maturity conduct little fixed actions to Cd in the concentration range of experiment and that most Cd in relatively active patterns participates in various transferences in soil-vegetable system. Among the five patterns, carbonates fraction was the primary one while Cd was under diversified stresses. 2)In Cd pollution soil with Pb, Zn and Ni added, appearance and distribute regulation of Cd accords with the one in single action. These three elements’effects on Cd were as follows:Pb improved Cd activity in cole and carrot soil while restraining the one in celery soil; Zn acted completely opposite to Pb; Ni decreased Cd activity in cole and celery soil while increasing the one in carrot soil. Via the three kinds of combination, the comparative result of activity of Cd and other adding elements was Cd>Pb, Cd>Zn, Cd>Ni.3)Among the three-vegetable soil, exchangeable, carbonates, Fe-Mn oxides and organic matter fractions of Cd had notable correlations with stress degree under single Cd stress. Most of relative variation equations were linear model, more-than-1 power model in the second place. As to the Cd pollution soil with Pb, Zn, Ni added:Pb added, Cd of exchangeable, carbonates, and Fe-Mn oxides fractions in the three soil and Cd of organic matter fractions in cole soil had notable correlations with the stress degree. Each form changes in linear and more than 1 power model patterns, excepted that Cd of carbonates fractions in carrot soil varies in level-log model; Zn added, Cd of exchangeable, carbonates, Fe-Mn oxides and organic matter fractions in soil has significant connection with the stress degree. When it comes to fractions-stress model, fitted equations of Cd in different forms were linear, excepted that those of Cd of exchangeable and organic matter fractions in cole soil and Cd of Fe-Mn oxides fractions in celery soil were more than 1 power model, sigmoid curve and logarithm model in turn; Ni added, Cd in all forms, except for residual fractions, was closely related to stress degree. Most variation of Cd in each form is consistent with linear model, level-log and less than 1 power models in the next place.4)Under single Cd stress, when Cd concentration was low, inhibiting effect was primarily reflected on weight of each vegetable portion and length of aboveground parts; when Cd concentration was high (Cd≥4.9mg/kg), inhibiting effect on length of underground parts was rather distinct. The rank order of these three vegetables’tolerance level to Cd stress was cole>carrot>celery. The distribution regularity of accumulation amounts in each portioin of cole and carrot was aboveground parts>underground parts, while celery was right adverse. The rank order of Cd accumulation amounts in each portion of the three vegetables was cole>celery>carrot. There is obvious enrichment to Cd in every portion of cole and underground parts of celery. The main site that impeded Cd transference in cole was the migration boundary up and below the ground and the one that impeded Cd transference in celery was the migration boundary between soil and underground parts. Carrots did not enrich Cd much, and the capabilities in Cd enrichment of each migration boundary were fair. The ability in Cd enrichment of the three vegetables was cole>celery>carrots, and the one in transference was cole>carrot>celery.5)The three vegetables were planted in Cd contaminated soil with Pb, Zn and Ni added. The results indicated that when in high concentration (Pb≥450mg/kg), Pb could weaken Cd inhibiting effects on biomass of the three vegetables, that Zn could weaken Cd inhibiting effects on aboveground length of celery and carrot and when in high concentration (Zn>500mg/kg), Zn could also weaken Cd inhibiting effects on fresh weight of celery underground portions and carrot aboveground parts, and that Ni could weaken Cd inhibiting effects on length and fresh weight of celery aboveground portions and when in high concentration(Ni≥600mg/kg), Ni can also soften Cd inhibiting effects on fresh weight of celery and carrot aboveground portions and length of carrot aboveground parts.6)The three intervening elements did not change distribution rule in vegetables, but led to significant variations of accumulation amounts and capabilities in enrichment and transference what vegetables responsed to Cd. These variations were due to actions of intervening elements. Effects of Pb, Zn and Ni on Cd accumulation in the three vegetables might present antagonistic or synergistic as results of differences in concentration, species and portions of vegetables. Comparing accumulation and transference coefficients of Cd, Pb, Zn and Ni in homogeneous vegetables, we concluded Cd was the most feasible element that accumulates and transfers in vegetables, Zn in the next place, and that Ni and Pb were relatively less feasible.7)Effects of amounts of exogenous Cd on its accumulation in each portion of vegetables could be described by linear, less-than-1 power and logarithm models. The last two models pointed out self-protection of vegetables (cole aboveground parts and every portion of celery) against exoteric concentration interference. The variation equation of Cd transference in vegetables demonstrates that regular patterns of Cd transference in cole and celery were consistent with less-than-1 power model, while in carrot, the model was linear, as was possibly one reason why cole and celery are more tolerant to Cd. Under Cd pollution stress with Pb, Zn and Ni added, the variations of Cd accumulation in vegetables could still be described by linear, power and logarithm models, but in power models, the power was more than 1 (Cd and Pb compounded, Cd was accumulated in each portion of celery and underground parts of carrot; Cd and Zn compounded, Cd was accumulated in underground parts of cole; Cd and Ni compounded, Cd was accumulated in aboveground parts of celery and underground parts of carrot). All of these showed that the higher stress concentration in compounded actions, the larger increment of Cd accumulation in relevant portions of these vegetables. Cd and the other three concomitant heavy metals, live migration in vegetables could be imitated by linear, level-log and power models. The powers in all power models come near 1, the level-log models are suitable for compounded Cd and Zn, and Cd compounded with Ni transfers in carrot.更多还原