Mechanism of Garden Aquatic Plants in the Remediation of Heavy Metal-Contaminated Soil

Heavy metals such as cadmium, lead, and mercury are resistant to microbial degradation in soil and persist for extended periods. They can bioaccumulate through the food chain, ultimately impacting human health. This study demonstrates that a combined restoration approach involving soil enhancement and garden aquatic plants, specifically through the application of ferrous sulfate, results in increased dry weight and plant height of these aquatic plants. The enhancement effect is positively correlated with the application rate, peaking at 5%. Additionally, this application significantly reduces cadmium accumulation in garden aquatic plants, with Umbrella grass exhibiting the most substantial reduction of 78%. However, the influence on cadmium migration remains unclear. Ferrous sulfate also lowers the amount of available cadmium in the soil, increases its residual state, and improves the removal efficiency of heavy metals, with Canna showing the highest increase at 5% (34%). In the combined remediation of stabilization treatments, the addition of biochar significantly enhances garden aquatic plants’ biomass and height (P < 0.05). An increase in biochar application correlates with reduced cadmium accumulation in these plants, with the most notable decrease observed in Iris yellow (36%).