Assessment of goethite modified biochar on the immobilization of cadmium and arsenic and uptake by Chinese cabbage in paddy soil

The combined remediation of cadmium (Cd) and arsenic (As) in paddy soils faces many challenges due to their opposite behavior. A pot study was conducted to evaluate the impact of biochar (BC), goethite (G), and goethite modified biochar (GBC) at a 1% application rate on the Chinese cabbage growth, uptake and immobilization of Cd and As in co-contaminated paddy soil. GBC composites were prepared at two different initial mass ratios (1:1 and 2:1) of iron/biochar (Fe/BC). Goethite modified biochar composite at Fe/BC initial mass ratios of 1:1 and 2:1 were labeled as GBC1 and GBC2, respectively. The results showed that GBC amendments significantly improved Chinese cabbage growth, chlorophyll content, and gas exchange attributes compared to BC and G applied singly. Biochar decreased Cd uptake by Chinese cabbage shoots and roots while increased As uptake by shoots and roots. The GBC1 amendment reduced Cd and As uptake by Chinese cabbage shoots (47.27% and 35.20%) and roots (36.80% and 41.12%), respectively, and reduced Cd and As bioaccessibility by 40.09% and 39.35%, respectively, compared to unamended soil. GBC is generally simple to synthesize from crop residue and is an environmentally acceptable material when used for Cd and As remediation in co-contaminated paddy soil.