施用污泥对鹅掌藤根系生长和重金属吸收的影响

目的 分析表施和混施污泥对鹅掌藤Schefflera arboricola根系生长和重金属吸收的影响，深入认识污泥施用对园林植物根系生长的影响，为污泥在园林中安全利用提供借鉴。方法 采用根箱试验，观测不施、表施和混施10%(w)污泥对常见园林植物鹅掌藤的不同土层根系形态及土壤pH和电导率动态变化的影响，分析根组织密度、根密度和重金属含量，拟合土壤pH、电导率、根系重金属含量与根长的关系。结果 与不施污泥相比，混施污泥明显抑制鹅掌藤根长、根表面积和根密度增长；而表施污泥显著增加鹅掌藤0~20 cm土层的总根长、根体积和根密度。处理240 d后，混施污泥处理的0~20与20~40 cm土层总根长分别为不施污泥的66.37%和51.51%，而表施污泥处理分别为不施污泥的115.43%和98.66%。最大总根长、根体积和根密度均出现在表施污泥的0~20 cm土层，最大根干质量和根组织密度出现在表施污泥的污泥层。混施污泥显著提高了土壤pH和电导率以及植株重金属含量，不同土层根系Cd、Zn、Cu和Ni含量分别是不施污泥的2.32~11.70倍。线性回归拟合分析表明，不施和表施污泥处理的0~20 cm土层鹅掌藤原位扫描总根长均与原位测定土壤pH呈极显著正相关(P<0.001)，鹅掌藤总根长与根系Cd、Zn、Cu和Ni含量均呈极显著负相关(P<0.001)。结论 表施10%(w)污泥可以提高土壤pH并促进鹅掌藤根系生长。混施10%(w)污泥显著增加不同土层根系重金属含量，进而抑制鹅掌藤根系生长。

Effects of sewage sludge application on root growth and heavy metal uptake of Schefflera arboricola

Objective This study aimed to analyze the effect of sewage sludge (SS) surface and mixed application on Schefflera arboricola root growth and heavy metals uptake, to deeply understand the effect of SS application on landscape plant root growth, and to provide a reference for the safe use of SS in the landscape.Method We conducted a root box experiment without SS (no SS) and with the surface application (surface SS) or the mixed application (mixed SS) of 10% SS, to analyze the dynamic changes of S. arboricola root morphology, soil pH, and conductivity in different soil layers. Root tissue density, root density, and heavy metal contents of plant were also analyzed. The relationships between soil pH, soil conductivity, root heavy metal contents, and root length were further established by the linear regression analysis. Result Compared with no SS, mixed SS treatment obviously inhibited the increment of root length, root surface area, and root density. Surface SS treatment significantly increased total root length, root volume, and root density in the 0-20 cm soil layer. After 240 days of treatment, total root length in 0-20 cm and 20-40 cm layers in mixed SS treatment were 66.37% and 51.51% of no SS, respectively. Those for surface SS treatment were 115.43% and 98.66% of no SS, respectively. The maximum root total length, root volume, and root density occurred in the 0-20 cm soil layer in surface SS treatment, while the maximum root dry weight and tissue density occurred in the SS layer in surface SS treatment. Mixed SS treatment significantly increased soil pH, soil conductivity, and heavy metal contents of S. arboricola. The contents of Cd, Zn, Cu, and Ni in roots of different soil layers in mixed SS treatment were 2.32 to 11.70 times higher than those in no SS treatment. The linear regression analysis showed that the in-situ scanning total root length of S. arboricola in 0-20 cm soil layers was significantly positively correlated with in-situ measured soil pH in no SS and surface SS treatment (P<0.001). Total root length of S. arboricola was significantly negatively correlated with the contents of Cd, Zn, Cu, and Ni in roots (P<0.001). Conclusion Surface application of 10% SS increases soil pH and promotes S. arboricola root growth. Mixed application of 10% SS significantly increases root heavy metal uptake in different soil layers and inhibits root growth of S. arboricola.