Abstract：
Cadmium (Cd) and arsenic (As) co-contamination has threatened rice production and food safety. It is challenging to mitigate Cd and As contamination in rice simultaneously due to their opposite geochemical behaviors. Mg-loaded biochar with outstanding adsorption capacity for As and Cd was used for the first time to remediate Cd/As contaminated paddy soils. In addition, the effect of zero-valent iron (ZVI) on grain As speciation accumulation in alkaline paddy soils was first investigated. The effect of rice straw biochar (SC), magnesium-loaded rice straw biochar (Mg/SC), and ZVI on concentrations of Cd and As speciation in soil porewater and their accumulation in rice tissues was investigated in a pot experiment. Addition of SC, Mg/SC and ZVI to soil reduced Cd concentrations in rice grain by 46.1%, 90.3% and 100%, and inorganic As (iAs) by 35.4%, 33.1% and 29.1%, respectively, and reduced Cd concentrations in porewater by 74.3%, 96.5% and 96.2%, respectively. Reductions of 51.6% and 87.7% in porewater iAs concentrations were observed with Mg/SC and ZVI amendments, but not with SC. Dimethylarsinic acid (DMA) concentrations in porewater and grain increased by a factor of 4.9 and 3.3, respectively, with ZVI amendment. The three amendments affected grain concentrations of iAs, DMA and Cd mainly by modulating their translocation within plant and the levels of As(III), silicon, dissolved organic carbon, iron or Cd in porewater. All three amendments (SC, Mg/SC and ZVI) have the potential to simultaneously mitigate Cd and iAs accumulation in rice grain, although the pathways are different.
摘要：
镉（Cd）和砷（As）的共污染已威胁到水稻的生产和食品安全。由于水稻的相反地球化学行为，同时减轻Cd和As污染具有挑战性。首次使用对As和Cd具有出色吸附能力的Mg负载生物炭修复Cd/As污染的水稻土。此外,首先研究了零价铁（ZVI）对碱性水稻土中谷物As形态积累的影响。水稻秸秆生物炭（SC）的效果，载镁稻草生物炭(Mg/SC)，在盆栽试验中，研究了ZVI对土壤孔隙水中Cd和As形态及其在水稻组织中积累的影响。添加SC,Mg/SC和ZVI对土壤的影响使水稻籽粒中的Cd浓度降低了46.1％，90.3%和100%,和无机砷(iAs)下降35.4%，33.1%和29.1%，分别,并将孔隙水中的Cd浓度降低了74.3%，96.5%和96.2%,分别。Mg/SC和ZVI修正剂观察到孔隙水iAs浓度降低了51.6％和87.7％，但不是SC。孔隙水和谷物中的二甲基arsinic酸（DMA）浓度分别增加了4.9和3.3倍，ZVI修正案这三个修正案影响了iAs的谷物浓度，DMA和Cd主要通过调节它们在植物内的转运和As(III)的水平，硅，溶解的有机碳，孔隙水中的铁或镉。所有三项修正案(SC，Mg/SC和ZVI）具有同时减轻稻粒中Cd和iAs积累的潜力，虽然路径不同。
