Straw return decreases PAHs accumulation in winter wheat and human health risk by enhancing PAHs dissipation in rhizosphere soil

Abstract

Straw return in situ is a common agronomic measure in China that has been widely used not only to increase crop yields and improve soil nutrients but also to remove PAHs from agricultural soil. Nevertheless, the safety risk of food crops grown in PAHs-contaminated agricultural soils and human health risk of wheat grains amended with crop straw remain uncertain. A pot experiment, PAHs-contaminated agricultural soils cultivated with winter wheat amended with different ratios of corn straw (0%, 1%, 2.5%, and 5%, w/w) was conducted. The results showed that PAHs concentrations in rhizosphere soil, roots, straws, and grains were significantly (P < 0.05) decreased by 48.32%–50.01%, 11.85%–42.67%, 9.78%–28.03%, and 14.16%–31.67%, respectively, compared with no corn straw addition (CK). But the transfer factors of PAHs from roots to straws (TFstraw/root) were significantly (P < 0.05) increased. A correlation heatmap showed that PAHs concentrations in roots, straws, and grains were positively (P < 0.01) correlated with those in the rhizosphere soil. These findings indicated that corn straw declined PAHs accumulation in winter wheat due to the increase of PAHs dissipation in the rhizosphere soil, although it enhanced PAHs transfer in winter wheat. The incremental lifetime cancer risk (ILCR) model indicated that corn straw significantly (P < 0.05) declined human health risk by 29.73%–45.05%. Overall, corn straw apparently reduced PAHs accumulation in winter wheat, ecological risk, and human health risk via enhancing PAHs dissipation in the rhizosphere soil. These present findings provide an important scientific basis and theoretical guidance for agricultural safety production.