Acute laboratory toxicity tests were carried out to assess the individual and combined toxic effects of metals including cadmium (Cd), lead (Pb) and the metalloid arsenic (As) in Phaeozem on the seed germination and seedling growth of soybean, Glycine max. Seeds were exposed to varied concentrations of Cd, Pb and As individually and in mixtures including Cd + Pb, Cd + As, Pb + As and Cd + Pb + As. The sum of toxic units (TU) for medium effective concentration of the mixture (EC 50mix ) was calculated based on the dose (TU-based)-response relationship using the Trimmed Spearman-Karber method. Binary metal combinations of Cd + Pb, Cd + As and Pb + As produced additive, synergistic and antagonistic effects, respectively, on shoot growth and synergistic, synergistic and antagonistic effects on root growth. Ternary combination of Cd + Pb + As had a synergistic effect on shoot growth and an additive effect on root growth. Bioaccumulation of metals was observed in soybean and inhibited or enhanced bioaccumulations of individual metals were found in mixtures due to different combinations of metals.

Purpose Applications of mineral and organic fertilizer increased soil cadmium (Cd) and could enhance Cd concentrations in edible crops, respectively. Although red mud (RMD) effectively decreased metal bioavailability in soil, the influence of RMD addition on vegetable growth and metal accumulation under high fertilization conditions has rarely been addressed. The aim of this study was to investigate the effects of raw RMD addition on cole growth, quality, and nutrition and Cd accumulation under high fertilization conditions. Materials and methods Pot experiments with cole (Brassica campestris L.) were carried out in a greenhouse. Three treatments, CK (with no mineral fertilizer and RMD addition), CT (more than 2.5 times conventional level of mineral fertilizer applied without any RMD), and RM (more than 2.5 times conventional level of mineral fertilizer applied with RMD added at 0.4 % w/w), were established. After 40 days, the cole plants and soils of every replicate of all treatments were sampled. The Cd, biomass, vitamin C (VC), and total nitrogen and phosphorus of the cole plant samples and the Cd, pH, nitrate, and phosphorus of the soil samples were determined. Results and discussion In contrast to the CT treatment, RM treatment did not significantly influence the biomass and nitrate concentration of the aboveground cole. However, it significantly reduced the Cd content in cole shoots and its bioaccumulation factors by 30.0 and 28.5 %, respectively. The reduction of bioavailable Cd in soil by RMD sorption and the competition with calcium released from RMD led to low Cd assimilation by root. Finally, less Cd was transported to aboveground plant parts in the RM treatment compared with the CT treatment. RMD addition markedly enhanced the total nitrogen in cole shoots by >16.0 %, and the VC by 20.9 %. The promotion of bacterial abundance and soil enzyme activity by RMD addition and calcium release from RMD generated substantial plant available nitrogen. Conclusions With large rate of mineral fertilizer application to the soil, RMD (0.4 %, w/w) addition did not significantly influence the biomass, nitrate, and VC of aboveground cole; however, it significantly reduced the Cd and markedly enhanced the total nitrogen in cole shoots. This study provides valuable information for the safe application of RMD in vegetable production.