Health management of Cd-contaminated soil using Ca-Al layered double hydroxide: Response of different vegetables

The green development of stabilizers is an important part of soil health management. Studying the impact of stabilizers on soil cadmium (Cd) adsorption is critical for sustainable agriculture. Calcium-aluminum layered double hydroxides (Ca-Al-LDH) are widely used to detoxify contaminated water and soil. Nevertheless, little is known about the efficacy of Ca-Al-LDH at modulating the heavy metal bioavailability of various crops. Incubation experiments, greenhouse and 3-year field trials were conducted to investigate the effects of Ca-Al-LDH on Cd, lead (Pb), and zinc (Zn) bioavailability in different soil-crop systems. The main soil type was hydragric anthrosols. The results showed that Ca-Al-LDH remediate heavy metal pollution through surface complexation, surface precipitation, and metal cation exchange with alkali. In incubation experiments, the application of 3 % Ca-Al-LDH for 7–42 d significantly decreased soil CaCl2-extractable Cd, Zn, and Pb by 94.38–96.37 %, 77.90–94.22 %, and 7.23–56.79 %, respectively, relative to the control (p < 0.05). It significantly lowered the exchangeable Cd fraction while increasing the carbonate-bound and the iron-manganese oxide-bound Cd fractions in the incubation and pot experiments. It significantly reduced the Cd content in bioaccumulator crops such as spinach, celery, amaranth, Shanghai bok choy, and lettuce-an. The Cd content in low-Cd-accumulation vegetables, such as bok choy, swamp cabbage, and lettuce-ra, increased following Ca-Al-LDH treatment to soil. Ca-Al-LDH activity remained stable for 3 years. The present study demonstrated that Ca-Al-LDH is a highly effective, sustainable, and versatile amendment for planting high-Cd vegetable cultivars. However, it should be avoided in areas with low Cd contamination or cautiously used when growing vegetables with low Cd-accumulation. It provides a theoretical and practical foundation for evaluating stabilizers and soil health management to remediate Cd-contaminated agricultural soils.