Comparative efficiency of silica gel, biochar, and plant growth promoting bacteria on Cr and Pb availability to Solanum melongena L. in contaminated soil irrigated with wastewater

Abstract

Crop irrigation with untreated wastewater is a routine practice in developing countries that causes multiple human health consequences. A comparative study was performed to regulate total Cr and Pb stress in soil and Solanum melongena L. plant. For this purpose, 0.2% chitosan polymerized silica gel (CP-silica gel), 1.5% zinc-enriched biochar (ZnBc), and three bacterial species such as Trichococcus sp. (B1), Pseudomonas alcaligenes (B2), and Bacillus subtilis (B3) were selected. Initially, a biosorption trial was conducted to test the heavy metal removal efficiency of three bacterial species B1, B2, and B3 for 24 h. Hence, B3 showed maximum Cr and Pb removal efficiency among the studied bacterial isolates. Then, a pot study was conducted with 12 different treatments having three replicates. After harvesting, different growth and biochemical parameters such as chlorophyll concentration, proteins, phenolics, reactive oxygen species, and antioxidant enzymes were analyzed. The results demonstrated that wastewater application significantly (p ≤ 0.01) reduced the fresh and dry weights of the root, stem, and leaves due to high total Cr and Pb toxicity. However, CP-silica gel and ZnBc treatments performed best when applied in combination with B3. The concentration of leaf total Cr was significantly decreased (91 and 85%) with the application of ZnBc + B3 and CP-Silica gel + B3, respectively, as compared to control. There was a reduction in stem hydrogen peroxide (87%) and malondialdehyde (81%) recorded with CP-silica gel + B3 treatment due to enhanced activities of antioxidant enzymes viz. ascorbate peroxidase (6-folds) and catalase (7-folds) relative to control. Similarly, leaf total phenolics (3-folds) and protein (6-folds) contents were enhanced with CP silica gel+B3 application relative to control. Overall, CP-silica gel and ZnBc with B3 application proved to be the most appropriate treatments and can be used in developing countries to limit the deleterious effects of total Cr and Pb pollution.

Trichoderma asperellum L. Coupled the Effects of Biochar to Enhance the Growth and Physiology of Contrasting Maize Cultivars under Copper and Nickel Stresses

“…In our previous experiments, we observed that applied biochar with Trichoderma sp. enhanced the porosity and surface area of soil, which increased the sorption or binding of metals and improved the functioning and synthesis of secondary metabolites such as total protein and phenolics which might be attributed to the enhanced water-holding capacity (WHC) of soil ( Figure 4 and Table S1 ) [ 19 , 20 ]. Soliman [ 41 ] also reported that the application of T. harzianum to Cucurbita pepo plants significantly improved the photosynthetic pigments and metabolites under salinity stress.…”

“…Similarly, the utilization of biochar is commonly believed to be an efficient amendment that can reduce the mobility and availability of these metals in polluted soil, hence reducing their accumulation in plants [ 17 , 18 ]. Bioremediation through the value addition processes such as biochar/engineered biochar are recent methods used to mitigate the harmful effects of lead (Pb) and chromium (Cr) toxicity in the soil [ 19 , 20 ]. The T. harzianum sp.…”

Amassing of heavy metals in soils, vegetables and crop plants irrigated with wastewater: Health risk assessment of heavy metals in Dera Ghazi Khan, Punjab, Pakistan

“…To meet water requirements, farmers have a general practice to use sewage and industrial wastewater as irrigation sources which include different heavy metal species including Pb, Zn, Cd, Ni, Fe, Mn, Cr, etc. ( Ali et al., 2014a ; Ali et al., 2014b ; Kanwal et al., 2020 ; Aslam et al., 2021 ; Rabiya et al., 2022 ). Different agrochemicals like synthetic fertilizers and pesticides (xenobiotics) also act as potential sources of heavy metals.…”