Use smaller size of straw to alleviate mercury methylation and accumulation induced by straw incorporation in paddy field

Abstract

Straw sizes were found to affect the methylmercury (MeHg) accumulation in rice grains induced by straw incorporation. The mechanism behind, however, still remains unclear. Here, we incorporated rice straw in different sizes (powder, 2 cm and 5 cm) into a Hg-contaminated paddy soil. Our results showed that straw sizes regulated the release of different fractions of organic matter (OM) in straw residues and further Hg methylation in paddy soil. The easily degradable OM (EDOM) was a key driving factor that facilitated net Hg methylation, though it only occupied a small fraction (1.12-3.12%) of the soil OM. Powdered straw reduced the duration of net Hg methylation by 74.39% compared to 5 cm straw, resulting in a strong and rapid net Hg methylation in paddy soil before the rice flowering. After the release of EDOM, the humified OM dominated in paddy soil and bound to MeHg, leading to less MeHg being transported to rice grains during the grain filling. Powdered straw decreased MeHg accumulation by 25.32% in the mature rice grains compared with 5 cm straw. Our study suggests that straw powdering before incorporation provides a feasible pathway for reducing MeHg accumulation in rice grains induced by straw incorporation.

Keywords

Mercury; Mercury methylation; Straw incorporation; Rice; Methylmercury accumulation

Published in

Journal of Hazardous Materials
2022, Volume: 423, article number: 127002Publisher: ELSEVIER

SLU Authors

• Li, Chuxian

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

SDG15 Life on land


UKÄ Subject classification

Agricultural Science


Publication identifier

DOI: https://doi.org/10.1016/j.jhazmat.2021.127002

Permanent link to this page (URI)

https://res.slu.se/id/publ/113790