Effect of Biochar and Zeolite on Cadmium Uptake in Green bell Pepper (Capsicum Annuum) and Leaching in Saline-alkaline Soil

The effect of various biochars and nano-clay on Cd immobilization and uptake by plants has been widely studied, but few studies have focused on the migration of different Cd fractions in saline-alkaline soils. Moreover, the remediation potential of biochar and nano-clay in saline soils polluted with heavy metals is still to be studied. Therefore, it was hypothesized that the Cd movement is influenced by biochar and nano-clay application in soil contaminated with the matter. The aim of the present study was to evaluate the effects of biochar and zeolite on the uptake of cadmium by green bell pepper (Capsicum annuum) and its downward movement in saline-alkaline and cadmium-contaminated soils.

The present study was carried out under two soil modification materials including wheat straw biochar (Triticum ( and zeolite nanoparticles at the level of 5 g/kg of cadmium-contaminated soil. The soil was collected at 0 to 30 cm depth from a plain in Sejzi, Esfahan. The soil was air-dried and stones, as well as plant litter, were removed, and then the soil was passed through a 5 mm sieve and prepared for the experiment. The heavy metal contaminated soil was created by placing 500 g air-dried soil into a 2 L glass beaker and mixing it with 250 mL cadmium nitrate (1.2 g Cd, Cd(NO3)2· 4H2O). In the Sejzi plain area, three plots were filled with biochar and zeolite at the level of 5 g/kg of cadmium-contaminated soil. After preparing the contaminated soils, green bell peppers (Capsicum annuum) were planted in them under natural conditions. 

The results showed that biomass of green bell pepper increased significantly by 79.2% and 18.3% using biochar and zeolite, respectively. The concentration of cadmium in green bell pepper’s fruit in biochar application was reduced by almost 30% compared to both control and soil treatments with zeolite. Cadmium absorbed by green bell pepper stems was about 50% of the total plant cadmium. Application of 5 gr of biochar and zeolite per kg of soil increased 42% and 78% of soil cadmium in topsoil (0-12 cm), respectively, compared to the subsoil.

According to the results, it can be stated that green bell pepper can be introduced as a cadmium absorber. The results also show the superiority of zeolite treatment over biochar treatment in reducing contamination transfer to the underlying layers of saline and alkaline soils and the addition of biochar caused a greater increase in green bell pepper biomass compared to zeolite nanoparticles in cadmium-contaminated soil.