The Residual Impact of Goethite-Modified Biochar on Cadmium and Arsenic Uptake by Maize in Co-Contaminated Soil

Cadmium (Cd) and arsenic (As) are toxic elements that threaten plants and human health. Due to the opposite transformations of Cd and As, their simultaneous immobilization poses numerous concerns. Thus, there is an urgent need to simultaneously reduce Cd and As mobility and plant uptake in co-contaminated soil. Our previous work found that goethite-modified biochar amendments effectively reduced Cd and As uptake by Chinese cabbage; however, their residual impact on subsequent crops must be investigated. In the current work, the following maize (Zea mays L.) was grown after Chinese cabbage in Cd and As co-contaminated soil amended by biochar (BC), goethite (G), and goethite-modified biochar (GBC) at a 1% application rate. The synthesis of GBCs involved two different initial mass ratios of iron/biochar (Fe/BC), with GBC1 having a Fe/BC ratio of 1:1 and GBC2 having a Fe/BC ratio of 2:1. The current study assessed the residual impacts of BC, G, and GBC amendments on Cd and As mobility, uptake by maize, and their impacts on maize growth. The results revealed that GBC amendments enhanced maize growth, chlorophyll content, and gas exchange parameters compared to raw BC and G. Moreover, the GBC1 amendment lowered Cd and As uptake by maize shoots (29.48% and 61.56%) and roots (33.07% and 37.32%), respectively, compared to unamended soil (CK). The GBC1 amendment decreased the bioaccessibility of Cd and As by 24.37% and 37.44%, respectively, compared with CK. In general, the results demonstrated that GBC has a significant residual impact on maize growth and Cd and As uptake in co-contaminated soil.