污泥施用下团花与鹅掌藤鲜叶和凋落叶重金属变化

Changes of heavy metal in fresh and litter leaves of Neolamarckia cadamba and Schefflera arboricola under sewage sludge application

该研究通过单种鹅掌藤(Schefflera arboricola)、单种团花(Neolamarckia cadamba)和混种团花与鹅掌藤的大根箱实验,跟踪分析表施2%(W/W)污泥后3个月(2020年9月、10月和11月)的鲜叶和凋落叶Cu、Zn、Cd和Hg含量以及凋落叶产量变化,分析鲜叶与凋落叶重金属含量关系以及凋落叶重金属回归量变化。结果表明:(1)污泥施用下团花鲜叶和凋落叶Cu含量均显著高于鹅掌藤,而Zn和Cd含量均显著低于鹅掌藤。(2)鹅掌藤鲜叶Zn含量在11月最低,而Hg含量在11月最高。(3)单种和混种团花鲜叶Zn、Cd和Hg含量在11月最高。(4)混种的团花凋落叶Hg含量随污泥施用时间延长而显著增加,而Cu、Zn和Cd含量变化不明显。(5)9月和11月鹅掌藤鲜叶Cd含量均与凋落叶Hg和Cd含量显著正相关。(6)鹅掌藤和团花凋落叶产量及Cu、Zn、Cd和Hg回归量分别在污泥施用1个月后(9月)和2个月后(10月)最高。综上所述,污泥施用时间对团花和鹅掌藤的鲜叶重金属含量影响较大,而对凋落叶重金属含量影响较小;鹅掌藤鲜叶Cd含量与凋落叶Cd和Hg含量存在正相关;鹅掌藤和团花分别在污泥施用1个月后(9月)和2个月后(10月)凋落叶重金属污染风险较高。该研究为污泥园林利用和凋落叶的合理处置提供了借鉴。

This study conducted a large root box experiment with Schefflera arboricola monoculture,Neolamarckia cadamba monoculture,and co-planting of Schefflera arboricola and Neolamarckia cadamba.The dynamic changes in Cu,Zn,Cd,and Hg contents in fresh and litter leaves of Schefflera arboricola and Neolamarckia cadamba and their litter leaves yield were analyzed for three months(September,October,and November 2020)after the surface application of 2%(W/W)sewage sludge(SS).The relationship between the heavy metal contents of fresh and litter leaves and the changes in the heavy metal return amount in litter leaves were further analyzed.The results were as follows:(1)N.cadamba had significantly higher Cu contents in fresh and litter leaves than those of S.arboricola,while had significantly lower Zn and Cd contents than those of S.arboricola.(2)The fresh leaves of S.arboricola had the lowest Zn content and the highest Hg content in November.(3)The fresh leaves of monoculture and co-planting Neolamarckia cadamba had the highest Zn,Cd,and Hg contents in November.(4)The Hg content in the litter leaves of co-planting of N.cadamba increased significantly with the time of SS application,while those of Cu,Zn,and Cd contents showed no significance.(5)The Cd content in fresh leaves was significantly and positively correlated with the Hg and Cd contents of litter leaves in Schefflera arboricola in both September and November.(6)The highest yield of litter leaves and the highest return amount of Cu,Zn,Cd,and Hg in S.arboricola occurred one month after SS application(September),while those in Neolamarckia cadamba occurred two months after SS application(October).In summary,the application time of SS showed a greater effect on the heavy metal contents in fresh leaves of N.cadamba and Schefflera arboricola than those in litter leaves;there was a positive correlation between the Cd content in the fresh leaves and the Cd and Hg contents in the litter leaves of S.arboricola;the heavy metal pollution risk of the litter leaves of S.arboricola and Neolamarckia cadamba was easy to occur in one month(September)and two months(October)after SS application,respectively.This study provides a reference for safe SS utilization and reasonable litter disposal in the landscape.