Pyroligneous acid influenced the bioavailability of heavy metals in contaminated paddy soil

초록

Utilization of pyroligneous acid known as wood vinegar (WV) benefited crop productivity through improved growth and development by supplying nutrients and crop protection. Its effect on the mobility and availability of heavy metals in soil-plant continuum is rarely studied therefore its potential as an organic amendment for ameliorating contaminated paddy soils was evaluated. Pot experiments using heavy metal spiked-paddy soil were conducted with the treatments: control, contaminated soil (CS); CS + 100x-WV, CS + 250x-WV, and CS + 500x-WV. Plant growth and yield parameters in rice were promoted by WV application at 500-x dilution. All WV treatments have comparable effects on Cu, Pb, and Zn contents in rice grains which are below the permissible values for consumption. Sequential extraction of heavy metals in soil showed the highest concentration of Cu and Zn in the residual fractions which are relatively stable and unavailable for plant uptake. A moderately high percentage of Pb and Zn in the Fe-Mn oxide fraction was observed which could be mobilized under reducing and acidic conditions. The changes in the percentage of metals in each fraction indicated that WV could displace ions and enhance mobility thus affecting the distribution in soil and plants. These findings indicate that WV (0.2%) can mitigate possible harmful effects of heavy metals and ensure food safety. Further investigation is warranted to fully understand the long-term effects of WV applications under field conditions.

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