修正案
化学
镉
高岭石
环境化学
针铁矿
生物利用度
铁酸盐
土壤水分
吸附
伊利石
粘土矿物
矿物学
吸附
土壤科学
环境科学
生物
法学
有机化学
生物信息学
政治学
作者
Jiawei Yan,Matthew Fischel,Hongping Chen,Matthew G. Siebecker,Peng Wang,Fang‐Jie Zhao,Donald L. Sparks
标识
DOI:10.1016/j.envpol.2020.115944
摘要
Cadmium bioavailability in paddy soils is strongly affected by flooding-draining cycle. In this study, we used synchrotron-based X-ray absorption spectroscopy and a stirred-flow method to investigate the effects of flooding-draining and amendments of CaCO3 and CaSO4 on Cd speciation and release kinetics from a Cd-spiked paddy soil (total Cd concentration of 165 mg kg−1). Extended X-ray absorption fine structure analysis showed that Cd was predominantly bound to non-iron-clay minerals (e.g. Cd-kaolinite, Cd-illite, and Cd-montmorillonite, accounting for 60–100%) in the air-dried soil and 1- or 7-day flooded samples. After prolonged flooding (30 and 120 days), Cd-iron mineral complexes (e.g. Cd bound to ferrihydrite and goethite) became the predominant species (accounting for 52–100%). Stirred-flow kinetic analysis showed that both prolonged flooding and the amendments with CaCO3 and CaSO4 decreased the maximum amount and the rate coefficient of Cd release. However, the effect of prolonged flooding was reversed after a short period of draining, indicating that although Cd was immobilized during flooding, it became mobile rapidly after the soil was drained, possibly due to pH decrease and rapid oxidation of CdS. The effects of the amendments on Cd uptake in rice plants were tested in a pot experiment using the same paddy soil without Cd spiking (total Cd 2.1 mg kg−1). Amendment with CaCO3 and, to a lesser extent, CaSO4, decreased the Cd accumulation in two cultivars of rice. The combination of CaCO3 amendment and a low Cd accumulating cultivar was effective at limiting grain Cd concentration to below the 0.2 mg kg−1 limit.
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