Short communicationGypsum alleviated hydroxyl radical-mediated oxidative damages caused by alkaline bauxite residue in leaves of Atriplex canescens

The present study investigated pH, electrical conductivity (EC), Al level, and exchangeable sodium percentage (ESP) in a range of alkaline bauxite residue (ABR) treatments. Also investigated was the content change of reactive oxygen species (ROS), malondialdehyde (MDA), and protein carbonyl (PCO) in leaves of Atriplex canescens [L.] challenged by ABR in the presence/absence of gypsum (Gy). Local cinnamon soil (CS) was used to improve the nutrient status and physical condition of ABR. Analysis revealed that CS/ABR (2:1, w/w) induced much more hydroxyl radical (OH) accumulation, lipid peroxidation (LPO), and protein oxidation (PO) than CS/ABR/Gy (6:3:1, w/w) did. While superoxide radical (O2−) and hydrogen peroxide (H2O2) accumulation showed little difference between CS/ABR and CS/ABR/Gy treatments. Further, exogenous OH aggravated LPO and PO in a way similar to CS/ABR treatment, which was impaired by OH scavengers such as proline and mannitol. Taken together, the data indicate that OH  is more connected with severe oxidative damages than O2− and H2O2 in this case. The caustic properties of ABR can be ameliorated by gypsum to support vegetation.