NTA-enhanced Pb remediation efficiency by the phytostabilizer Athyrium wardii (Hook.) and associated Pb leaching risk.

Abstract

Nitrilotriacetic acid (NTA), a biodegradable chelant, has been promoted to effectively assist Pb phytoextraction, while a few researches available on the phytostabilizer of Athyrium wardii (Hook.). In this study, two incubation experiments and a subsequent column experiment were conducted to investigate the effects of application of NTA on Pb availability in soils and Pb accumulation in A.wardii and associated leaching risk. The application of NTA significantly increased the exchangeable Pb and Pb bound to carbonates along with a decreased pH, leading to enhanced Pb availability in soils. It was more effective in enhancing Pb availability in soils by adding 2mmolkg-1 NTA into soils at once for 7d, thus demonstrating potential for enhancing Pb uptake by A.wardii. After the addition of 2mmolkg-1 NTA for 7d, Pb concentrations in roots of A.wardii was enhanced by 23.8%, along with 10.6% of increase for Pb accumulation in roots. No significant changes were observed for the biomass of A.wardii. Meanwhile, the available Pb and TCLP-extractable Pb in 0-20cm soils increased by 11.1-23.4% and 7.1-31.2%, thus promoting Pb leaching in 0-20cm soils. However, there were no changes for Pb leaching risk levels of 20-40cm soils. No Pb was detected in the leachates from all columns. The application of 2mmolkg-1 NTA at once for 7d is therefore proved to show greater potential in enhancing Pb remediation efficiency by the phytostabilizer of A.wardii without increasing Pb leaching risk into groundwater.