Effect of nanoparticles of rice husk ash on the bioavailability of lead to Indian mustard (Brassica juncea) in lead spiked soil

Heavy metal contamination in croplands has been a serious concern because of its high health risk through soil food chain transfer. A screen house experiment was conducted to study effect of rice husk ash and its nanosized particles on bioavailability and accumulation lead (Pb) by Indian mustard in a loamy sand soil amended with Pb. The soil was spiked with four rates of Pb ranging from 0 to 200 mg kg⁻¹ and amended with rice husk ash (RHA) and nano size RHA (NRHA) at four rates ranging from 0 to 4% (dry weight basis). The effectiveness of treatments in stabilizing metals was assessed on the basis of decrease in DTPA extractable metal level and content of metal in plant. Application of RHA at the highest level decreased the DTPA extractable Pb content in soil by 33.2, 27.5 and 26.5% and in plant by 46.5, 34.9 and 38.0% at 50, 100 and 200 mg Pb kg⁻¹ soil, respectively. NRHA was significantly more effective in comparison to normal RHA, which resulted in a decrease of 45.6, 46.4 and 40.3% for DTPA extractable Pb and its content in mustard by 73.7, 60.2 and 59.7% at 50, 100 and 200 mg Pb kg⁻¹ soil, respectively. Application of RHA increased the dry matter yield (DMY) significantly and maximum increase was observed at the highest contamination level of 200 mg Pb kg⁻¹ where increases in DMY by RHA and NRHA were 89 and 99%, respectively. Results revealed that NRHA outperformed RHA in every aspect. The study concluded that RHA, an agro-industrial waste, has potential for managing heavy metal contaminated soils.