Municipal sewage sludge compost promotes Mangifera persiciforma tree growth with no risk of heavy metal contamination of soil

Shuangshuang Chu,Can Lai,Daoming Wu,Shucai Zeng,Liyin L Liang,Yaping Hu,Xinsheng Hu,Fengdi Zhong

doi:10.1038/s41598-017-13895-y

Shuangshuang Chu, Can Lai + Show 6 more

Open Access

https://doi.org/10.1038/s41598-017-13895-y

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Abstract

Application of sewage sludge compost (SSC) as a fertilizer on landscaping provides a potential way for the effective disposal of sludge. However, the response of landscape trees to SSC application and the impacts of heavy metals from SSC on soil are poorly understood. We conducted a pot experiment to investigate the effects of SSC addition on Mangifera persiciforma growth and quantified its uptake of heavy metals from SSC by setting five treatments with mass ratios of SSC to lateritic soil as 0%:100% (CK), 15%:85% (S15), 30%:70% (S30), 60%:40% (S60), and 100%:0% (S100). As expected, the fertility and heavy metal concentrations (Cu, Zn, Pb and Cd) in substrate significantly increased with SSC addition. The best performance in terms of plant height, ground diameter, biomass and N, P, K uptake were found in S30, implying a reasonable amount of SSC could benefit the growth of M. persiciforma. The concentrations of Cu, Pb and Cd in S30 were insignificantly different from CK after harvest, indicating that M. persiciforma reduced the risk of heavy metal contamination of soil arising from SSC application. This study suggests that a reasonable rate of SSC addition can enhance M. persiciforma growth without causing the contamination of landscaping soil by heavy metals.

Highlights

Municipal sewage treatment projects often produce a considerable amount of sludge each year across the world[1], especially in developing countries[2]
If M. persiciforma grows well in sewage sludge compost (SSC)-amended soil and is able to take up a desirable amount of heavy metals, landscaping with the application of SSC would become practical in the tropics and subtropics
When the amount of applied SSC was less than 60%, the heavy metal concentrations in the substrates are lower than the tier II level (Cu < 50 mg·kg−1, Zn < 200 mg·kg−1, Pb < 250 mg·kg−1, and Cd < 0.3 mg·kg−1) of the “Environmental Quality Standards for Soil of China” (GB 15618–1995)[33]

Summary

Introduction

Municipal sewage treatment projects often produce a considerable amount of sludge each year across the world[1], especially in developing countries[2]. As reviewed by Liu[19], toxic effects were often caused by high concentrations of heavy metals in SSC and unrealistically high amounts of SSC amendments This suggested that controlling the amount of sludge application may be an effective way to reduce the phytotoxicity of the heavy metals. Previous studies indicated that woody plants, such as Salix spp.[29,30] and Populus spp.[31], were well adapted to SSC and were effective in taking up the heavy metals in sludge These results suggested that selecting suitable woody plants that have high biomass and heavy metals tolerance can be an effective way to ensure the ecological safety of SSC utilization as soil amendments in landscaping. The growth response of M. persiciforma to SSC and the fate of heavy metals in the SSC are still poorly understood

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