【作者】 蓝兰；

【导师】 涂仕华；

【作者基本信息】 四川农业大学 ， 植物营养， 2010， 硕士

【摘要】 重金属镉(Cd)是最危险的环境污染物之一,它通过食物链在人体内积累并危害人体健康。在土壤重金属污染中,我国土壤的Cd污染相对较为广泛,农产品Cd含量超标的情况常有发生。小麦是粮食作物中易于吸收和累集Cd的作物,因此,即使土壤Cd含量处于污染临界值以下,也会出现小麦籽粒Cd含量超过国家规定的食品安全限量指标的情况。作物从土壤中吸收Cd的多少,主要取决于土壤有效Cd含量的高低和促进无效Cd向有效Cd转化的因素。因此,开展Cd污染土壤上影响土壤Cd有效性的变化因子及其调控措施,对我国的食品安全和人类健康,意义重大。钙(Ca)、镁(Mg)、硫(S)、铁(Fe)、锰(Mn)、硼(B)、锌(Zn)、钼(Mo)和铜(Cu)等元素是植物生长的必需营养元素,硅(Si)和硒(Se)等为植物生长的有益元素。施用这些肥料品种会影响土壤的某些理化性状,从而影响镉的形态变化及植物对镉的吸收和积累。在过去的研究中,国内外作者已对上述提到的一些中、微量元素和有益元素如Ca、Zn、Si、Se进行了研究,但在同一条件下这些元素对土壤重金属生物有效性的影响的系统比较的研究鲜见报道。因此,本试验的目的旨在系统研究不同中微量及有益元素对土壤镉有效性的影响及其对小麦生长和吸收镉的影响。本研究采用土壤室内培养试验研究了不同中微量及有益元素肥料对土壤镉有效性的影响,采用小麦网室土壤栽培试验对不同中微量及有益元素肥料对小麦生长及吸收镉的影响进行研究,在此基础上初步提出了小麦优化施肥技术。本试验取得的主要研究结果如下：1.采用土壤培养方法研究了不同中微量元素及有益元素对镉污染土壤pH和镉(Cd)有效性的影响。结果表明,不同中微量元素和有益元素肥料对土壤pH和Cd有效性的影响差异显著,但同一元素的盐酸盐和硫酸盐对土壤Cd有效性的影响差异不明显。在65-100%田间持水量的培养过程中,5d后土壤pH显著下降,有效Cd提取量明显上升。在这些被测试的元素/物质中,Ca、Mg、Cu、硼酸和硫磺粉显著降低了土壤pH,而碳酸钙和硅酸钠增加了土壤pH；除Mg外,这些元素或物质导致的土壤pH变化与Cd的有效性呈负相关。Fe、Mn、Mg、Si、Se对土壤Cd的有效性表现为拮抗关系,而Ca、Zn、Cu则表现为协同关系。根据本试验的研究结果,建议在镉污染的旱作土壤上施用中微量元素及有益元素肥料时,要避免施用硫磺粉、硼酸、氯化钙、锌肥和铜肥；宜施用铁、锰、镁肥及硼砂、硅酸钠及亚硒酸钠,以降低土壤Cd的有效性。2.采用盆栽试验,研究了不同中微量元素及有益元素对小麦生长和吸收Cd的影响。结果表明,与对照相比,硫酸钙、硫酸锰和氯化铜处理提高了小麦籽粒产量,而氯化镁、硫磺粉、硫酸铜、硫酸亚铁和硼酸处理却显著降低了小麦籽粒产量。在受Cd污染的土壤上施用不同中微量及有益元素肥料对土壤Cd的有效性具有一定的调节作用。镁、锰、铁、硼砂、硅酸钠和亚硒酸钠处理降低小麦对Cd的吸收；而钙、铜、锌和硼酸处理增加了小麦对Cd的吸收,特别是氯化钙。中量及微量元素的盐酸盐比硫酸盐处理促进小麦对Cd的吸收；小麦秸秆中Cd的积累量远远大于籽粒。因此,建议在Cd污染的旱作土壤上要避免施用硫磺粉、硼酸、氯化钙、锌肥和铜肥；施用铁、锰、镁肥及硼砂、硅酸钠和亚硒酸钠对降低土壤Cd的活性有明显效果,能在一定程度上降低小麦对Cd的吸收。3.在土壤全镉含量很高(0.92mg kg-1,远远超过了国家土壤环境质量二级污染标准(0.3mg kg-1)的情况下,施用的某些中微量及有益元素虽能显著降低土壤中Cd的有效性,从而降低小麦籽粒中的Cd含量,但未能控制到国家规定的食品镉污染限量标准(0.2mg kg-1)以下,说明在Cd污染严重的土壤上,单独的一般施肥措施很难把小麦籽粒中的Cd降至国家安全限量标准。更多还原

【Abstract】 The heavy metal cadmium (Cd), one of the most toxic contaminants in the environment, can be accumulative in human body to an extent that becomes harmful to health through food chains. Among the different types of heavy metal pollution, the area of soil polluted by Cd is relatively larger than any other heavy metals in China, resulting in frequently reported Cd pollution of foodstuffs. Wheat is the crop that is prone to take up Cd from soil and susquently accumulate in the plant, and thus, lead to high Cd content in grains that surpasses the safe threshold set by the State. The quantity of Cd taken up by crops mainly depends on the quantity of soil available Cd and factors that promote transformation of non-available soil Cd to the available forms. Therefore, it is of great importance to conduct research on the factors that can reduce quantity of soil available Cd and the measures that can control soil Cd availability to safeguard food safety and human health.Calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manganese (Mn),boron (B), molybdenum (Mo), and cupper (Cu) are the necessary nutrients of higher plants, and silicon (Si) and selenium (Se) are classified as beneficial elements of higher plants. Addition of these elements to soils tends to affect some of the soil physio-chemical properties, and further alter forms of soil Cd and plant uptake and accumulation as well. Past research on some of the above-mentioned elements has been conducted both at home and abroad, however, there is lack of systematic studies with comparisons between these elements affecting the availability of soil Cd under the same conditions. Thus, the objectives of this study were to systematically investigate effects of secondary, micro-and beneficial elements on availability of soil Cd and Cd uptake by wheat. The availability of soil Cd and Cd uptake by wheat as affected by different secondary, micro-and beneficial elements were investigated by incubation studies and pot experiments as well. On the basis of these studies, some optimized fertilizer practices that are effective in controlling Cd availability on the Cd polluted soil were concluded.1. Effects of different fertilizers of secondary, micro-and beneficial elements on soil pH and extractable Cd were examined in an incubation study using a Cd contaminated soil. Results revealed that these fertilizers had significant effects on soil pH and amounts of Cd extracted. The amounts of Cd extracted by the compounds of an element bearing Cl- or SO42- were not highly different. During the incubation at 65-100% field capacity it encountered a significant drop in soil pH and a rise in soil extractable Cd. Among the elements and materials studied, Ca, Mg, Cu, boric acid and elemental S significantly decreased soil pH, while calcium carbonate and sodium silicate significantly increased soil pH. Except Mg, the soil pH changes induced by addition of these elements or materials were negatively correlated with amounts of Cd extracted. An antagonistic effect was observed between Fe, Mn, Mg, Si, Se and soil extractable Cd, but a synergistic effect between Ca, Zn, Cu and soil extractable Cd. The results sμggest that when applying fertilizers of secondary, miro-and beneficial elements to a Cd polluted upland soil, use of elemental S,boric acid, Ca, Zn or Cu should be avoided, while Fe, Mn, Mg as well as borax, sodium silicate and sodium selenite are preferred.2. Effects of secondary, micro-and beneficial elements on wheat growth and cadmium (Cd) uptake were investigated in a pot experiment. The results showed that calcium sulfate, manganese sulfate and cupper chloride obviously increased wheat grain yield while magnesium chloride, elemental sulfur, cupper sulfate, ferrous sulfate and boric acid significantly enhanced wheat grain yield compared to the CK treatment. On the cadmium (Cd) polluted soil, application of secondary, micro-and beneficial elements played a regulatory role on soil Cd availability. Among the fertilizers and elements studied, Mg, Mn, Fe, borax, sodium silicate and sodium selenite reduced Cd uptake, while Ca as calcium chloride in particular, Cu, Zn and boric acid promoted Cd uptake by wheat. The chlorides of the secondary and micro-elements favored Cd uptake more than their counterpart sulfates. The Cd accumulated in wheat straw was far more than in grain. Thus, it is sμggested that on the Cd polluted upland soil it necessitates to avoid applying elemental sulfur, boric acid, Zn and Cu fertilizers but to use Fe, Mn, Mg, borax, sodium silicate and sodium selenite that favor lowering the activity of soil Cd and depress Cd uptake by wheat to a certain extent.3. On the soil that contains rather high amount of total Cd (0.92mg kg-1, much higher than the threshold value (0.3mg kg-1) of the soil environmental quality set by the State), thoμgh applying some of the secondary, micro-and beneficial elements could significantly reduce amounts of soil available Cd and Cd uptake by wheat, the reduction still failed to bring Cd content in wheat grains below the food safety threshold for wheat grains as set by the State. This further indicates that on the soil severely polluted by Cd, use of only one single measure appeared not effective enoμgh to reduce the Cd content in wheat grains below the food safety threshold.更多还原