Can soil remediation agents synergistically mitigate rice Cd content and CH4 emission from karst paddies?

Abstract

Rice (Oryza sativa L.) paddies are increasingly threatened by cadmium (Cd) pollution, and potentially serve as CH₄ emitters to the atmosphere. Remediation agents widely mitigate Cd pollution in paddy soil, however, we know little about their regulations on CH₄ emission. Here, via adding biochar (B), sulfhydryl-modified palygorskite (SMP), and selenium foliar fertilizer (SFF), we conducted a pot experiment to investigate soil and rice Cd contents together with in-situ CH₄ fluxes. Compared to CK, the addition of SMP, SFF, and B-SMP reduced Cd in brown rice by 25% to 50%, 25%, and 50% to 75%, respectively. Agents 7% B, 7% B-0.01% SMP, and SFF reduced CH₄ emissions by 8.46%, 5.30%, and 4.11%, respectively. CH₄ emission increased gradually along the growing season, with the cumulative CH₄ fluxes ranging between 338.82 and 619.13 kg hm⁻². Our results highlight that mixed 7% B-0.01% SMP and SFF showed collaborative effects on Cd remediation and CH₄ emission. This study reveals the feasibility of reducing Cd pollution and CH₄ emission in karst rice paddies, which hopes to supplement the knowledge of collaborative controls on soil remediation and carbon emission.