Straw return decreases polycyclic aromatic hydrocarbon (PAH) accumulation in winter wheat and human health risk by enhancing PAH dissipation in rhizosphere soil

Straw return in situ, a common agronomic measure in China, has been widely used not only to increase crop yields and improve soil nutrients but also to remove polycyclic aromatic hydrocarbons (PAHs) from agricultural soils. Nevertheless, the safety risks of food crops (i.e., human health risk of wheat grains) grown in PAHs-contaminated agricultural soils amended with crop straw remain uncertain. A pot experiment was conducted in a PAHs-contaminated agricultural soil cultivated with winter wheat under different ratios of corn straw addition (0% (control, CK), 1%, 2.5%, and 5%, weight/weight). Results showed that corn straw addition significantly (P < 0.05) decreased PAH concentrations in rhizosphere soil, roots, straws, and grains by 48.32%–50.01%, 11.85%–42.67%, 9.78%–28.03%, and 14.16%–31.67%, respectively, compared with CK, whereas the transfer factors of PAHs from roots to straws were significantly (P < 0.05) increased. A correlation heatmap showed that PAH concentrations in roots, straws, and grains were positively (P < 0.01) correlated with those in rhizosphere soil. These indicated that corn straw decreased PAH accumulation in winter wheat due to the increase of PAH dissipation in the rhizosphere soil, although it enhanced PAH transfer in winter wheat. The incremental lifetime cancer risk (ILCR) model indicated that corn straw significantly (P < 0.05) decreased the human health risk of winter wheat grains by 29.73%–45.05%. Overall, corn straw apparently reduced PAH accumulation in winter wheat, ecological risk, and human health risk via enhancing PAH dissipation in the rhizosphere soil. These findings provide an important scientific basis and theoretical guidance for agricultural safety production.