Investigating industrial by-product for soil conditioning addressing environmental risk and waste reduction alternatives

Condisoil is an innovative soil conditioner formulated from industrial by-products specifically Water Leach Purification and Neutralisation Underflow residues derived from rare-earth processing. This study investigates its potential to improve sandy soils for paddy cultivation, a vital sector for Malaysia's food security. Unlike conventional soil amendments, Condisoil promotes sustainability by repurposing industrial by-products and addressing disposal challenges. However, due to its origin, assessing elemental distribution and soil-to-rice grain transfer factors is essential to ensure its agricultural safety. Activity concentrations of naturally occurring radionuclides (NORM) ²²⁶Ra, ²²⁸Ra, and ⁴⁰K in Condisoil-treated soils ranged from 66.5 to 143.1, 49.7 to 70.6, and 391.6 to 432.2 Bq/kg, respectively, over two paddy planting seasons. In rice grains, NORM levels were significantly lower, ranging from 0.93 to 9.20 (²²⁶Ra), 0.03 to 0.53 (²²⁸Ra), and 89.14 to 147.95 (⁴⁰K) Bq/kg. Heavy metal As, Sb, Cr, Cd, and Pb concentrations in soils remained below Malaysian safety standards, while rice grains contained in the range of 0.2-1.4, 0.7-3.0, 0.1-0.1, and 0.5-1.8 mg/kg, respectively. TF values for radionuclides and heavy metals ranged from 0.00 to 0.00-0.30 and 0.01-1.0, respectively. The estimated annual effective dose from rice consumption remained below the 1.0 mSv/year safety threshold. While the uptake of most elements was minimal, lead (Pb) and antimony (Sb) exhibited HI values > 1, and the TF value of cadmium (Cd) was > 1, indicating potential health risks. Therefore, environmental monitoring is essential before large-scale application. This study highlights Condisoil's potential in sustainable agriculture and waste valorization, though strict heavy metal monitoring protocols are necessary to ensure long-term food safety when using industrial by-products as soil conditioners.