Hanhua Zhu

Cadmium (Cd) and arsenic (As) co-contamination in paddy soils may lead to their accumulation in rice grains, creating health concerns for humans. While iron (Fe) nutrition has emerged as a promising mitigation strategy, the impact of application timing is not well understood. This study evaluated the effects of chelated iron (EDTA·Na₂Fe) applications at two growth-stage combinations: pre-transplanting + booting and tillering + booting. Both treatments reduced Cd and As concentrations in rice grains; however, the tillering + booting treatment was the more effective, decreasing grain Cd and As levels by 53.2% and 60.7%, respectively. This reduction is linked to decreased Cd (9.6%–29.9%) and As (10.7%–15.3%) soil availability, and restricted translocation within the plant. The tillering + booting treatment specifically limited soil Cd bioavailability and root-to-grain Cd transport, and inhibited As transfer from iron plaques to roots and from vegetative tissues to grains. These findings demonstrate that stage-targeted application of EDTA·Na₂Fe, particularly during the tillering and booting stages, is an effective agronomic strategy for minimizing Cd and As accumulation in rice cultivated on co-contaminated soils.

Planting energy sorghum to remove soil cadmium (Cd) has been selected as an effective phytoremediation method in subtropical farmland in China in recent years. Nevertheless, the effects of energy sorghum species and cropping systems on Cd removal by energy sorghum are still not fully understood. In the present work, biomass sorghum (BS) and sweet sorghum (SS) were planted for screening varieties and comparing the applicability of cropping systems to remove Cd from contaminated soils through batch field experiments. The results indicated that BS had a higher plant height (4.70–75.63%), lower water content in the shoot (4.78–13.49%), greater dry biomass yield (13.21–125.16%), and stronger Cd removal (average 45.71%) compared with SS. Significant differences (p < 0.05) were observed in the agronomic traits and Cd accumulation of energy sorghums with genetic regulation of varieties. Pearson correlation coefficients analysis and the structural equation model (SEM) showed that plant height was the crucial agronomic parameter affecting the dry biomass yield, and Cd concentration in the stem was the key factor for evaluating the Cd extraction ability of energy sorghums, which indirectly determined the removal of Cd by energy sorghum together. Furthermore, the regeneration cropping system was the most suitable because of the adaptation to climatic conditions of energy sorghums in subtropical regions of China, and its Cd removal efficiency increased by more than 49% compared with double cropping and single cropping systems, respectively. Our study provides valuable information for the phytoremediation of Cd-contaminated soil in Chinese subtropical farmland.

Metal transporters, including divalent metal-ion transporter-1 (DMT1), Zrt-/Irt-like protein 8 and 14 (ZIP8 and ZIP14), and ferroportin-1 (FPN1), reportedly participate in cellular cadmium (Cd) uptake, but those in farm animals remain unclarified. This study aimed to examine the growth, plasma biochemical indices, Cd accumulation, and expression of metal transporter genes in the liver, kidney, and muscle of goats exposed to rice paddies contaminated with different levels of Cd. Twenty-four goats were randomly assigned across three dietary treatments: 0.23, 0.63, and 1.07 mg of Cd/kg of dry matter (DM) for 60 days. The results showed that dietary Cd exposure increased (p < 0.05) both Cd accumulation and the mRNA expressions of metal transporter genes (DMT1, ZIP, and FPN1) in the liver and kidney but not in the muscle, suggesting dietary Cd exhibited different deposition rates between goat liver, kidney, and muscle. These outcomes suggest that high levels of dietary Cd stimulated the expression of metal transporter genes and thereby enhanced the uptake and accumulation of Cd in the goat liver and kidney. As such, higher Cd concentrations in the liver and kidney observed with Cd diets could be partly explained by upregulation of metal transport genes expression.