鸡粪生物炭对土壤铜和锌形态及植物吸收的影响

Effects of chicken manure-derived biochar on Cu and Zn speciation in soil and uptake by plant

300℃制备的鸡粪生物炭既可以固定碳和重金属,又可以克服鸡粪不当处理所产生的环境问题,但由于鸡粪中Cu和Zn的含量较高,因此使用时可能存在重金属污染风险。本文研究了温室大棚中土壤培养和小白菜盆栽下施用鸡粪生物炭对土壤Cu和Zn形态以及植物吸收的影响。结果表明施用鸡粪生物炭可以明显增加土壤pH,减少土壤有效态Cu含量,小白菜盆栽条件下鸡粪生物炭对有效态Cu抑制程度小于土壤培养。空白土壤中施入鸡粪生物炭后有效态锌的含量增加了6.19 mg·kg^(-1),使用鹿粪则可以减少鸡粪生物炭对土壤有效态Zn含量的影响。随着土壤培养时间的延长,施用鸡粪生物炭可降低酸溶态与可还原态Cu的比例,增加残渣态Cu比例,提高施加鸡粪生物炭处理中可氧化态与残渣态Zn比例。高温高湿环境下施用2%鸡粪生物炭能够促进小白菜的生长,增加小白菜干重,减少小白菜根部重金属Cu和Zn含量,降低Cu和Zn的根富集系数,二次盆栽后添加鸡粪生物炭还能够降低小白菜茎叶部Cu和Zn的含量。以上结果说明,鸡粪生物炭施入土壤后可引起短时间的污染风险,且Zn的污染风险大于Cu,但随着时间的延长,鸡粪生物炭既可促进小白菜的生长,减少Zn的释放,又能固定Cu和Zn,从而减少植物对Cu和Zn的吸收。

The chicken manure-derived biochar at 300℃ can immobilize carbon and heavy metals, and decrease the environmental problems caused by improper treatment of chicken manure. However, with the higher content of Cu and Zn in chicken manure, there may be a potential risk of heavy metal pollution owing to the use of biochar. Soil culture and pot experiments using bok choy （Brassica chinensis） in a greenhouse were performed to investigate the effect of chicken manure-derived biochar on Cu and Zn speciation in soil and their uptake by plants. The results showed that the application of chicken manure-derived biochar significantly increased the pH of soil and reduced the content of available Cu in soil. The available Cu content increased by 6.19 mg·kg-1 by adding chicken manure-derived biochar to blank soil, whereas the increase of the available Cu content could be prevented by adding deer manure. With time, the proportions of acid-soluble and reducible Cu were reduced, and the proportion of residual Cu was increased owing to chicken manure-derived biochar addition. For all the treatments with biochar, the proportions of oxidizable and residual Zn in soil were increased. At high temperature and humidity, the application of 2% biochar promoted the growth of bok choy, increased the dry weight, reduced the content of Cu and Zn in the roots, and reduced the accumulation coefficient of Cu and Zn in the roots. In the second pot experiment, the application of biochar reduced the content of Cu and Zn in the stems and leaves of bok choy. These results indicate that the application of chicken manure-derived biochar would cause pollution risk in the short term, and that Zn would cause greater pollution risk than Cu. However, with time, biochar application can promote the growth of bok choy, reduce the release of Zn, and immobilize Cu and Zn. Eventually, the uptake of Cu and Zn by the plants is reduced.