Remediation of Cadmium- and Lead-contaminated Soil by Using Modified Phosphogypsum

The effect of modified phosphogypsum on the remediation of cadmium (Cd)- and lead (Pb)-contaminated soil was explored to realize the safe production of agricultural crops. A field experiment was conducted with three treatments: control (without modified phosphogypsum), T1 (with modified phosphogypsum applied at 3 000 kg·hm^-2) and T2 (with modified phosphogypsum applied at 6 000 kg·hm^-2). Compared with the original phosphogypsum, the modified phosphogypsum had a rougher surface texture, looser structure, and more biochar particles attached to the surface. The T2 treatment greatly increased the pH, EC, organic matter content, and soil available nutrient content and greatly reduced the soil effective states of Cd/Pb, and maize kernel Cd/Pb contents compared with the T1 treatment. Additionally, T2 treatment gave the largest increases in the maize yield per, 100-kernel weight, crude protein percentage, calcium percentage, phosphorus percentage, and chlorophyll content, by 33.73%, 21.43%, 20.21%, 52.63%, 19.35%, and 24.66%, respectively, compared with the control group. Correlation analysis show that the maize silage yield was significantly positively correlated with the soil pH, EC, organic matter, alkali-hydrolyzed nitrogen, available phosphorus, and available potassium content. It was also significantly and negatively correlated with the soil effective states of Cd/Pb. In summary, the application of modified phosphogypsum at a dose of 6 000 kg·hm^-2 can effectively remediate and improve Cd/Pb-contaminated soil to enhance soil fertility and reduce Cd/Pb uptake by crops. The results of this study provide a theoretical basis for the safe production of agricultural crops in Cd/Pb-contaminated soil, promote recycling of resources, and reduce environmental pollution.