Study on the blending of biochar derived from pine bark in lead contaminated soil to reduce lead (Pb) uptake in selected leafy vegetables

Abstract

Purpose In the context of agricultural land being narrowed due to urbanization, together with the level of pollution, especially heavy metal pollution, continuing to rise, the issue of ensuring output and food security is becoming increasingly urgent. Developing solutions to remediate heavy metal-contaminated soil, allowing continued farming on polluted land without compromising consumer health, is a necessary priority. Methods In this study pine bark was investigated as a raw material for producing a novel biochar with high adsorption capacity for Heavy metals. Particularly, pine bark biochar was obtained by pyrolysis at 300 –700 °C. The resulting biochar was then incorporated into lead-contaminated soil at various application rates (2–10%) to determine the optimal proportion for reducing lead uptake and accumulation in the biomass of several commonly cultivated leafy vegetables in Da Lat, Vietnam. These vegetables included spinach (Spinacia oleracea), mustard greens (Brassica juncea), butterhead lettuce (Lactuca sativa var. capitata), green lollo lettuce (Lactuca sativa var. longifolia), and red lollo lettuce (Lactuca sativa var. longifolia). Advanced analytical techniques were employed to characterize the properties of the biochar, the treated soils, and the harvested vegetables. Results The results indicate that pine bark is a promising raw material for producing adsorbents, with superior physicochemical properties compared to other feedstocks; its specific surface area SBET reached 272.447 m².g−1. Biochar application significantly reduced Pb accumulation in leafy vegetables with the highest rate (10%) decreasing Pb concentration by up to 73.3%. Notably in contaminated soil biochar reduced Pb levels in some vegetables below the safetyLimit of 0.3 mg.kg−1. However, excessive biochar may negatively impact plant growth and yield. Applying 8% pine bark biochar to lead-contam inated soils supported healthy growth and development of the studied vegetables while markedly lowering Pb accumulation in their edible parts. Conclusion Pine bark biochar, an abundant local availability and favorable physicochemical properties material could be incorporated into lead contaminated soil to reduce lead accumulations in vegetables. This is a feasible strategy to address the growing problem of agricultural soil pollution, contributing to food security and sustainable agriculture.