# Sustainable remediation of heavy metal contaminated soil through phytostabilization with the in-situ immobilization by mercapto-based palygorskite

## TL;DR

This study shows that using mercapto-based palygorskite with a specific grass improves soil remediation by reducing cadmium and lead toxicity and enhancing soil health.

## Contribution

The novel use of mercapto-based palygorskite combined with Chrysopogon zizanioides for phytostabilization is proposed as an effective remediation strategy.

## Key findings

- MPAL application significantly reduced Cd and Pb concentrations in plant roots and shoots.
- MPAL combined with C. zizanioides reduced DTPA-extracted Cd and Pb in soils by up to 89.22% and 51.18%.
- Soil enzyme activities and microbial diversity increased with MPAL and C. zizanioides treatment.

## Abstract

Phytostabilization has been widely applied to remediate mining soils contaminated with heavy metals, but the high soil toxicity often restricts plant growth and remediation efficiency. In this experiment, we investigated the effect of mercapto-based palygorskite (MPAL, applied at 2% and 4% w/w) on cadmium (Cd) and lead (Pb) phytostabilization by Chrysopogon zizanioides in soils contaminated with Cd and Pb. The results showed that soil pH did not vary under the application of MPAL but decreased during the cultivation of C. zizanioides. Compared with planting C. zizanioides alone, the application of MPAL significantly promoted the growth of C. zizanioides, enhanced its antioxidant enzyme activities, and decreased Cd and Pb concentrations in roots and shoots. Compared with CK, the addition of 4% MPAL, cultivated with C. zizanioides, reduced DTPA-extracted Cd and Pb in soils by 89.22% and 51.18%, respectively, at the highest level (p < 0.05). Moreover, urease, cellulase, and sucrase activities in soils treated with MPAL and cultivated with C. zizanioides were enhanced, with maximum increases of 37.70%, 110.22%, and 42.99%, respectively (p < 0.05). The interaction of MPAL and C. zizanioides increased bacterial richness and diversity but did not alter the bacterial community. This study demonstrated that the use of MPAL in combination with C. zizanioides could serve as a potential strategy for Cd and Pb immobilization and improvement of soil microecological properties.

Illustration depicting the role of phytostabilization in reducing cadmium (Cd) and lead (Pb) in soil using C. zizanioides. Arrows indicate the uptake and immobilization process within plant roots. Text highlights MAPL's positive interactions with soil micro-ecology. Bar graphs show urease activity and cadmium levels for different treatments, with labels for significance. A community bar plot illustrates microbial diversity.