Cadmium (Cd) is a toxic element that can easily enter the human body through the food chain. Rice grain is the main contributor to dietary Cd intake, especially for those populations who consume rice as the staple. Therefore, reducing Cd accumulation in rice is of significance for food safety and human health. In this review, we summarized the major factors underlying the biogeochemical processes controlling Cd availability in soils. Soil pH is one of the most important factors affecting soil Cd availability. An increase in soil pH can dramatically decrease soil Cd solubility; thus, liming is often found to be an effective and economical method in acidic contaminated soils to reduce grain Cd accumulation. The voltaic effect between Cd-sulfide and other metal sulfides formed during soil flooding regulates the remobilization of Cd during soil drainage. Therefore, addition of small amounts of ZnSO₄ or MnSO₄ to soils can form a protective voltaic cell partner against the oxidative dissolution of Cd sulfides, thereby decreasing Cd remobilization during soil drainage and Cd accumulation in rice grain. The voltaic effect is expected to be more important than their direct competition between Zn²⁺ and Cd²⁺. Besides, water management practices markedly affect soil Cd availability by altering the redox status of soils; continuous flooding and delaying drainage of paddy soils during the grain filling period can effectively reduce grain Cd accumulation. These effective biogeochemical strategies can be used singly or combinedly to reduce soil Cd availability and subsequent Cd uptake/accumulation in rice to ensure food safety.

镉（Cd）是一种有毒元素，可以很容易地通过食物链进入人体。稻米是膳食中Cd摄入的主要来源，特别是对于那些以稻米为主食的人群。因此，减少水稻中Cd的积累对食品安全和人类健康具有重要意义。在这篇综述中，我们总结了控制土壤中Cd有效性的生物地球化学过程的主要因素。土壤pH值是影响土壤Cd利用率的最重要因素之一。土壤pH值的升高会显着降低土壤Cd的溶解度。因此，通常发现在酸性污染土壤中撒石灰是一种有效而经济的方法，可以减少谷物中Cd的积累。在土壤淹没过程中形成的硫化镉和其他金属硫化物之间的伏特效应调节了土壤排水过程中镉的迁移。因此，添加少量的ZnSO₄或MnSO ₄进入土壤可形成保护性的伏打电池伴侣，以防止Cd硫化物的氧化溶解，从而减少土壤排水过程中Cd的迁移和水稻籽粒中Cd的积累。期望其伏打效应比其在Zn ²⁺和Cd ²⁺之间的直接竞争更为重要。此外，水管理措施通过改变土壤的氧化还原状态，显着影响土壤镉的利用。灌浆期水稻土的持续淹水和延迟排水可有效减少Cd的积累。这些有效的生物地球化学策略可以单独使用或组合使用，以减少土壤中Cd的利用率以及随后稻米中Cd的吸收/积累，以确保食品安全。