【作者】 陕红；

【导师】 刘荣乐； 李书田；

【作者基本信息】 中国农业科学院 ， 植物营养学， 2009， 博士

【摘要】 土壤镉污染对生态系统、粮食安全及人体健康具有巨大的潜在危害,已成为当今全球共同关注的重大环境问题。我国有机物资源丰富,通过施用有机物降低镉的危害既适合我国国情,也符合农业可持续发展要求。然而有机物对土壤镉有效性的影响还存在一定的争议,不同有机物的作用效果和机制也不一致。秸秆和畜禽粪便是最主要的有机资源,因此,有必要研究其对镉有效性的影响及机理,从而为其合理利用提供理论依据。本研究以作物秸秆和猪粪为材料研究有机物施入土壤后:对土壤镉生物有效性的影响;对土壤镉形态转化的影响;对土壤镉形态和生物有效性影响的机理。取得如下主要结果与进展:1.利用樱桃萝卜和冬小麦进行盆栽试验研究未经腐熟的小麦秸秆或腐熟猪粪施入土壤后对镉生物有效性的影响和机理。结果表明,在潮土和红壤上,施用秸秆显著增加第一茬樱桃萝卜叶和根的镉浓度,并促进镉向可食部位根的转移,但可显著降低第二茬樱桃萝卜叶和根的镉浓度,并抑制镉向可食部位的转移。施用猪粪显著降低樱桃萝卜各部位镉浓度,同时抑制镉向可食部位的转移。在潮土和黄棕壤上,施用秸秆或猪粪均可显著降低小麦各部位镉浓度及镉向可食部位籽粒的转移。在降低植株Cd浓度的效果上,猪粪好于秸秆,猪粪施入红壤或黄棕壤后对植株Cd浓度的降低作用大于施入潮土后的效果。2.采用土壤培养和盆栽试验研究施用未腐熟秸秆或腐熟猪粪对土壤镉形态的动态影响。结果表明,在非种植条件下,在潮土和红壤上施用秸秆45天后,可显著提高交换态镉含量,降低低活性态镉含量,但45天后这种作用随培养时间逐渐减弱,到90天后作用不显著。猪粪在整个培养期间均显著降低交换态镉含量,增加低活性态镉含量。在潮土和红壤上种植樱桃萝卜的情况下,施用秸秆到第一茬樱桃萝卜收获时交换态镉含量增加,低活性态镉含量下降,到第二茬收获时,交换态镉含量下降,低活性态镉含量增加。施用猪粪后,两茬樱桃萝卜收获时高活性的交换态镉含量均降低,其他低活性态镉含量则增加。在潮土和黄棕壤上种植小麦的情况下,施用秸秆或猪粪均降低交换态镉含量。回归分析表明,樱桃萝卜和小麦体内镉浓度的变化主要与土壤交换态和有机质结合态镉含量有关,且与交换态镉含量呈显著正相关而与有机质结合态镉含量呈显著负相关。说明秸秆和猪粪可通过土壤镉形态的变化来影响植株对镉的吸收。猪粪施入红壤或黄棕壤后对交换态Cd含量的降低作用大于施入潮土后的效果。3.采用土培试验和盆栽试验表明,施用秸秆或猪粪可不同程度地影响土壤pH。施用秸秆后,潮土和黄棕壤的pH变化不显著,而红壤pH增加。施用猪粪后,潮土pH显著降低,而红壤和黄棕壤pH显著增加。相关分析表明,秸秆施入潮土、红壤和黄棕壤及猪粪施入潮土后,土壤pH与交换态镉含量呈显著正相关。猪粪施入红壤和黄棕壤后,土壤pH与交换态镉含量呈显著负相关。说明只有当猪粪施入红壤和黄棕壤后可通过pH的改变降低镉的有效性。4.施用秸秆或猪粪均可显著增加土壤胡敏酸(HA)和富里酸(FA)含量,但其对HA/FA比的影响不同。非种植条件下,施用秸秆可降低潮土和红壤的HA/FA,但该作用随培养时间逐渐减弱。种植樱桃萝卜情况下,施用秸秆到第一茬收获时,潮土和红壤中HA/FA降低,但第二茬收获后土壤HA/FA则增加。种植小麦情况下,施用秸秆可增加潮土和黄棕壤上HA/FA。无论是否种植作物,猪粪施入土壤后均可增加土壤HA/FA,猪粪对土壤HA/FA的增加作用大于相同碳用量的秸秆,且猪粪施入红壤和黄棕壤后对HA/FA的增加作用大于在潮土上的作用。回归分析表明,施用秸秆和猪粪后,交换态镉含量与HA/FA呈显著负相关关系。采用施用外源HA和FA的土壤培养试验进一步证明,增加土壤HA/FA可显著降低交换态镉含量,增加碳酸盐结合态及铁锰氧化物结合态镉的含量。综上所述,无论施用秸秆还是猪粪可通过改变土壤HA/FA影响土壤镉的活性,从而影响植物对镉的吸收是有机物影响土壤镉形态及镉生物有效性的主要机制。因此,利用有机物降低土壤镉活性时,应将有机物充分腐熟,增加HA/FA比,达到降低镉活性和生物有效性的目的。更多还原

【Abstract】 Cadmium contamination has great potential thread to ecosystem, food safety and human health. It has been an important environmental problem widely concerned. There are abundant organic materials in China. Application of organic materials to reduce mobility of cadmium not only adapts to national conditions of China but consists with the demand of sustainable agriculture. However, the effect of organic materials on the availability of cadmium and the related mechanisms is still unclear and inconsistent. Straw and manure are the main organic materials in China. So, it is necessary to study the effect of straw or manure on the availability of cadmium in soils and the related mechanisms in order for appropriate application of organic materials in reducing the availability of cadmium in contaminated soils.In this study, crop straw or pig manure was applied in Cd contaminated soils to investigate: the effect of straw or pig manure amendment on the bioavailability of cadmium in soils; the effect of straw or pig manure amendment on changes of cadmium fractions in soils; the mechanisms of the effect of straw or pig manure on cadmium availability. The main findings were obtained as follows:1. Pot experiments with cherry-red radish and winter wheat were conducted to study the effect of wheat straw or compost pig manure amendment on phytoavailability of cadmium in Cd contaminated soils and the mechanisms. Results showed that cadmium concentrations in radish tissues and the distribution of cadmium to edible part increased for the first harvest when straw was applied to calcareous soil and acidic red soil. But cadmium concentrations in radish tissues and the distribution of cadmium to the edible part decreased for the second harvest after the application of straw. Application of pig manure reduced cadmium concentrations in radish tissues and the distribution of cadmium to the edible part in both soils. Straw or pig manure amendment in Fluvo-aquic soil and yellow brown soil significantly reduced cadmium concentrations in wheat tissues and Cd distribution to the edible part (grain). The reduced effect of pig manure amendment on cadmium concentrations in plants was more significant than that of straw application. The reduced effect of manure on cadmium concentrations in plant tissues in red soil and yellow brown soil was more significant than in Fluvo-aquic soil.2. A soil incubation experiment and pot experiments were conducted to study the effect of straw or pig manure amendment on changes of cadmium fractions in soils. In soil incubation experiment, exchangeable cadmium in Fluvo-aquic soil and red soil increased significantly and other fractions decreased during the first 45 days after the application of straw. This increasing effect decreased with the incubation time and was not significant after incubation for 90 days. During the whole incubation period of 90 days exchangeable cadmium decreased and other fractions increased when pig manure was applied. When planting cherry-red radish exchangeable cadmium increased and other cadmium fractions decreased by the first harvest when straw was applied to Fluvo-aquic soil and red soil. Whereas exchangeable cadmium decreased and other cadmium fractions increased by the second harvest after the application of straw. While application of pig manure decreased exchangeable cadmium and increased other cadmium fractions by both harvests. When winter wheat was planted the exchangeable cadmium decreased and other cadmium fractions increased whether straw or pig manure was applied to Fluvo-aquic soil and yellow brown soil. Stepwise multiple regression analysis indicated that cadmium concentrations in radish and wheat tissues could be explained by the variations of exchangeable and/or organic bound cadmium in soils. Cadmium concentrations in radish and wheat tissues were positively correlated with the content of exchangeable cadmium and negatively correlated with the content of organic bound cadmium in soils. These results showed that straw or pig manure could affect cadmium concentrations in plants by changing cadmium fractions in soils. The reduced effect of pig manure on exchangeable cadmium in red soil and yellow brown soil was more significant than in Fluvo-aquic soil.3. Soil pH was affected by the application of straw or pig manure. The change of soil pH in Fluvo-aquic soil and yellow brown soil was not significant and the pH in red soil significantly increased after the application of straw. The pH in Fluvo-aquic soil significantly decreased, whereas the pH in red soil and yellow brown soil significantly increased when manure was applied. When straw was applied to Fluvo-aquic soil, red soil and yellow brown soil, a significant positive relationship existed between soil pH and exchangeable cadmium fraction. But when composted pig manure was applied to red soil and yellow brown soil, there was a significant negative relationship between soil pH and the exchangeable cadmium fraction. These results suggested that cadmium availability be reduced by changes of soil pH only when pig manure was applied to red soil and yellow brown soil.4. Although humic acid and fulvic acid increased when straw or pig manure was added to the soils, the changes of soil HA/FA ratio were different. The HA/FA ratio of soils without planting decreased when straw was applied to Fluvo-aquic soil or red soil but this reduced effect diminished with incubation time. When cherry-red radish was planted soil HA/FA ratio decreased by the first harvest and increased by the second harvest after application of straw to Fluvo-aquic soil and red soil. When wheat was planted soil HA/FA ratio increased when straw was applied to Fluvo-aquic soil and red soil. Amendment of pig manure increased soil HA/FA ratio in soils with or without planting. The effect of pig manure on the increase of soil HA/FA ratio was more than that of straw and this effect in red soil and yellow brown soil was more than that in Fluvo-aquic soil. Stepwise multiple regression analysis indicated that exchangeable cadmium fraction which was regarded as the most available form in soils was negatively correlated with HA/FA ratio and can be explained by the variation of HA/FA ratio in soils. Soil incubation experiment by the addition of HA or FA in soils further demonstrated that the exchangeable cadmium decreased while carbonated bound and oxide bound cadmium increased by increasing soil HA/FA ratio.In summary, the main mechanism for the effect of organic material on phytoavailability of cadmium in soils was that amendment of straw or pig manure changed soil HA/FA ratio which affected cadmium fractions especially the exchangeable Cd fraction. This result suggested that organic materials should be composted to increase the ratio of HA/FA before using to reduce the availability of cadmium in soils.更多还原