Remediation of Pb-polluted Agricultural Soils by Application of Biochar Amendments: Effects on Yield and Toxicological Risk Parameters in Soybean Crops

ARIAS, R. A.; BLANCO A.; PARDO S. D; WANNAZ, E.D.; SALAZAR M.J.

Montevideo

Congreso; SETAC Latin America 15th Biennial Meeting; 2023

Society of Environmental Toxicology and Chemistry

The present work evaluated the use of biochar amendments made from peanut industry residues, using 3 different pyrolysis temperatures, to remediate lead-contaminated agricultural soils. Biochar is a type of organic amendment consisting of a stable, carbon-rich material obtained by the thermal decomposition of organic matter. To evaluate its use for remediation in agricultural soils, an experiment was conducted under controlled greenhouse conditions with contaminated soils, under 4 different treatments: (1) without amendment, (2) with 5% biochar produced at 300°C, (3) with 5% biochar produced at 400°C and (4) with 5% biochar produced at 500°C. A complete growth cycle of soybean (Glycine max (L.) Merrill) was carried out in 9 L pots. The response variables determined included: Pb accumulation in plant organs (acid digestion and atomic absorption spectrometry measurement), morphological state of the plants (length and plant dry weight), and yield of the produced grains (number of seeds and pods, weight of 1000 seed, aborted pods). Moreover, toxicological risk index (target hazard quotient, THQ) was evaluated for Argentinian and Chinese consumers, with the latter being one of the main destinations of Argentinian soybean.The results showed that soybean plants grew better in amended soils, especially regarding plant length and root dry weight. The highest plant length was found in treatment (2), and the highest root dry weight was found in treatment (3). At the yield level, plants from all the amended treatments showed a greater number of seeds than the not amended one, although the seed dry weight per plant and the weight of 1000 seeds did not show differences. Pb accumulation in organs was mainly concentrated in the roots, with no remarkable differences among the treatments analyzed. It is noteworthy that the seeds showed Pb concentrations that exceeded the limit values of international legislation for soybean consumption (circa 1.5 ppm), a situation that was not reversed by the use of the amendment. In this sense, the evaluation of the risk index for consumers showed elevated values for Chinese consumers, although without an effective risk.In conclusion, the use of amendments made from peanut industry residues improved soybean development and yield, but it did not prevent metal accumulation in soybean seeds. For this reason, it is recommended to evaluate amendments from other sources for soybean production in agricultural soils contaminated with Pb.