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.

In situ immobilization is a widely used measure for passivating Cd-contaminated soils. Amendments need to be continuously applied to achieve stable remediation effects. However, few studies have evaluated the impact of consecutive application of amendments on soil health and the microecological environment. A field experiment was conducted in a Cd-contaminated paddy (available Cd concentration 0.40 mg kg-1) on the Chengdu Plain to investigate the changes in soil Cd availability and response characteristics of soil bacterial communities after consecutive application of rice straw biochar (SW), fly ash (FM) and marble powder (YH) amendments from 2018 to 2020. Compared with control treatment without amendments (CK), soil pH increased by 0.6, 0.5 and 1.5 under SW, FM and YH amendments, respectively, and the soil available Cd concentration decreased by 10.71%, 21.42% and 25.00%, respectively. The Cd concentration in rice grain was less than 0.2 mg kg-1 under YH amendment, which was within the Chinese Contaminant Limit in Food of National Food Safety Standards (GB2762-2022) in the second and third years. The three amendments had different effects on the transformation of Cd fractions in soil, which may be relevant to the specific bacterial communities shaped under different treatments. The proportion of Fe-Mn oxide-bound fraction Cd (OX-Cd) increased by 11% under YH treatment, which may be due to the promotion of Fe(III) and Cd binding by some enriched iron-oxidizing bacteria, such as Lysobacter, uncultured_Pelobacter sp. and Sulfurifusis. Candidatus_Tenderia and Sideroxydans were enriched under SW and FM amendments, respectively, and were likely beneficial for reducing Cd availability in soil through Cd immobilization. These results revealed the significance of the bacterial community in soil Cd immobilization after consecutive application of amendments and highlighted the potential of applying YH amendment to ensure the safe production of rice in Cd-contaminated soil.

Wheat (Triticum aestivum L.) is one of the most important crops worldwide and a major source of human Cd intake. Limiting grain Cd concentration (Gr_Cd_Conc) in wheat is necessary to ensure food safety. However, the genetic factors associated with Cd uptake, translocation, distribution, and Gr_Cd_Conc in wheat are poorly understood. Here, we mapped quantitative trait loci (QTL) for Gr_Cd_Conc and its related transport pathway using a recombinant inbred line (RIL_DT) population derived from two Polish wheat varieties (dwarf Polish wheat [DPW] and tall Polish wheat [TPW]). We identified 29 novel major QTLs for grain and tissue Cd concentration; 14 novel major QTLs for Cd uptake, translocation, and distribution; and 27 major QTLs for agronomic traits. We also analyzed the pleiotropy of these QTLs. Six novel QTLs (QGr_Cd_Conc-1A, QGr_Cd_Conc-3A, QGr_Cd_Conc-4B, QGr_Cd_Conc-5B, QGr_Cd_Conc-6A and QGr_Cd_Conc-7A) for Gr_Cd_Conc explained 8.16-17.02% of the phenotypic variation. QGr_Cd_Conc-3A, QGr_Cd_Conc-6A and QGr_Cd_Conc-7A pleiotropically regulated Cd transport; three other QTLs were organ-specific for Gr_Cd_Conc. We fine-mapped the locus of QGr_Cd_Conc-4B and identified the candidate gene as Cation/Ca exchanger 2 (TpCCX2-4B), which was differentially expressed in DPW and TPW. It encodes an endoplasmic reticulum membrane/plasma membrane-localized Cd efflux transporter in yeast. Overexpression of TpCCX2-4B reduced Gr_Cd_Conc in rice. The average Gr_Cd_Conc was significantly lower in TpCCX2-4BDPW genotypes than in TpCCX2-4BTPWgenotypes of the RIL_DT population and two other natural populations, based on a KASP marker derived from the different promoter sequences between TpCCX2-4BDPW and TpCCX2-4BTPW. Our study reveals the genetic mechanism of Cd accumulation in wheat and provides valuable resources for genetic improvement of low-Cd-accumulating wheat cultivars.

With advances in plastic resource utilization technologies, polystyrene (PS) and sulfonated polystyrene (SPS) microplastics continue to be produced and retained in environmental media, potentially posing greater environmental risks. These plastics, due to their different physicochemical properties, may have different environmental impacts when compounded with other pollutants. The objective of this study was to investigate the combined toxic effects of PS and SPS on wheat using cadmium (Cd) as a background contaminant. The results demonstrated that Cd significantly impeded the normal growth of wheat by disrupting root development. Both PS and SPS exhibited hormesis at low concentrations and promoted wheat growth. Under combined toxicity, PS reduced oxidative stress and promoted the uptake of essential metal elements in wheat. Additionally, KEGG pathway analysis revealed that PS facilitated the repair of Cd-induced blockage of the TCA cycle and glutathione metabolism. However, high concentrations of SPS in combined toxicity not only enhanced oxidative stress and interfered with the uptake of essential metal elements, but also exacerbated the blocked TCA cycle and interfered with pyrimidine metabolism. These differences are related to the different stability (Zeta potential, Hydrodynamic particle size) of the two microplastics in the aquatic environment and their ability to carry heavy metal ions, especially Cd. The results of this study provide important insights into understanding the effects of microplastics on crops in the context of Cd contamination and their environmental and food safety implications.

Microplastics (MPs) have become pervasive in marine ecosystems, exerting detrimental effects on marine life. The concurrent presence and interaction of MPs and heavy metals in aquatic environments could engender more insidious toxicological impacts. This study aimed to elucidate the potential impacts and underlying mechanisms of polystyrene microplastics (PS-MPs), cadmium (Cd), and their combined stress (MPs-Cd) on sea cucumbers (Apostichopus japonicus). It focused on the growth, Cd bioaccumulation, oxidative stress responses, immunoenzymatic activities, and metabolic profiles, specifically considering PS-MPs sizes preferentially ingested by these organisms. The high-dose MPs (MH) treatment group exhibited an increase in cadmium bioavailability within the sea cucumbers. Exposure to PS-MPs or Cd triggered the activation of antioxidant defenses and immune responses. PS-MPs and Cd exhibited a synergistic effect on lysozyme (LZM) activity. A total of 149, 316, 211, 197, 215, 619, 434, and 602 differentially expressed metabolites were identified, distinguishing the low-dose MPs (ML), high-dose MPs (MH), low-dose Cd (LCd), low-dose MPs and low-dose Cd (MLLCd), high-dose MPs and low-dose Cd (MHLCd), high-dose Cd (HCd), low-dose MPs and high-dose Cd (MLHCd), high-dose MPs and high-dose Cd (MHHCd) groups, respectively. Metabolomic analyses revealed disruptions in lipid metabolism, nervous system function, signal transduction, and transport and catabolism pathways following exposure to PS-MPs, Cd, and MPs-Cd. Correlation analyses among key differentially expressed metabolites (DEMs) underscored the interregulation among these metabolic pathways. These results offer new perspectives on the distinct and synergistic toxicological impacts of microplastics and cadmium on aquatic species, highlighting the complex interplay between environmental contaminants and their effects on marine life.

In previous studies, iron-based nanomaterials, especially biochar (BC)-supported sulfidized nanoscale zero-valent iron (S-nZVI/BC), have been widely used for the remediation of soil contaminants. However, its potential risks to the soil ecological environment are still unknown. This study aims to explore the effects of 3% added S-nZVI/BC on soil environment and microorganisms during the remediation of Cd contaminated yellow-brown soil of paddy field. The results showed that after 49 d of incubation, S-nZVI/BC significantly reduced physiologically based extraction test (PBET) extractable Cd concentration (P < 0.05), and increased the immobilization efficiency of Cd by 16.51% and 17.43% compared with S-nZVI and nZVI/BC alone, respectively. Meanwhile, the application of S-nZVI/BC significantly increased soil urease and sucrase activities by 0.153 and 0.446 times, respectively (P < 0.05), improving the soil environmental quality and promoting the soil nitrogen cycle and carbon cycle. The results from the analysis of the 16S rRNA genes indicated that S-nZVI/BC treatment had a minimal effect on the bacterial community and did not appreciably alter the species of the original dominant bacterial phylum. Importantly, compared to other iron-based nanomaterials, incorporating S-nZVI/BC significantly increased the soil organic carbon (OC) content and decreased the excessive release of iron (P < 0.05). This study also found a significant negative correlation between OC content and Fe(II) content (P < 0.05). It might originate from the reducing effect of Fe-reducing bacteria, which consumed OC to promote the reduction of Fe(III). Accompanying this process, the redistribution of Cd and Fe mineral phases in the soil as well as the generation of secondary Fe(II) minerals facilitated Cd immobilization. Overall, S-nZVI/BC could effectively reduce the bioavailability of Cd, increase soil nutrients and enzyme activities, with less toxic impacts on the soil microorganisms.

The green and efficient remediation of soil cadmium (Cd) is an urgent task, and plant-microbial joint remediation has become a research hotspot due to its advantages. High-throughput sequencing and metabolomics have technical advantages in analyzing the microbiological mechanism of plant growth-promoting bacteria in improving phytoremediation of soil heavy metal pollution. In this experiment, a pot trial was conducted to investigate the effects of inoculating the plant growth-promoting bacterium Enterobacter sp. VY on the growth and Cd remediation efficiency of the energy plant Hybrid pennisetum. The test strain VY-1 was analyzed using high-throughput sequencing and metabolomics to assess its effects on microbial community composition and metabolic function. The results demonstrated that Enterobacter sp. VY-1 effectively mitigated Cd stress on Hybrid pennisetum, resulting in increased plant biomass, Cd accumulation, and translocation factor, thereby enhancing phytoremediation efficiency. Analysis of soil physical-chemical properties revealed that strain VY-1 could increase soil total nitrogen, total phosphorus, available phosphorus, and available potassium content. Principal coordinate analysis (PCoA) indicated that strain VY-1 significantly influenced bacterial community composition, with Proteobacteria, Firmicutes, Chloroflexi, among others, being the main differential taxa. Redundancy analysis (RDA) revealed that available phosphorus, available potassium, and pH were the primary factors affecting bacterial communities. Partial Least Squares Discriminant Analysis (PLS-DA) demonstrated that strain VY-1 modulated the metabolite profile of Hybrid pennisetum rhizosphere soil, with 27 differential metabolites showing significant differences, including 19 up-regulated and eight down-regulated expressions. These differentially expressed metabolites were primarily involved in metabolism and environmental information processing, encompassing pathways such as glutamine and glutamate metabolism, α-linolenic acid metabolism, pyrimidine metabolism, and purine metabolism. This study utilized 16S rRNA high-throughput sequencing and metabolomics technology to investigate the impact of the plant growth-promoting bacterium Enterobacter sp. VY-1 on the growth and Cd enrichment of Hybrid pennisetum, providing insights into the regulatory role of plant growth-promoting bacteria in microbial community structure and metabolic function, thereby improving the microbiological mechanisms of phytoremediation.

The interaction between microplastics (MPs) and cadmium (Cd) poses a threat to agricultural soil environments, and their effects on plant growth and rhizosphere microbial community functions are not yet clear. In this study, energy sorghum was used as a test plant to investigate the effects of two types of MPs, polystyrene (PS) and polyethylene (PE), at different particle sizes (13 μm, 550 μm) and concentrations (0.1%, 1% w/w), and Cd, as well as their interactions, on the growth of sorghum in a soil-cultivation pot experiment. The results showed that the combined effects of MP and Cd pollution on the dry weight and Cd accumulation rate in sorghum varied depending on the type, concentration, and particle size of the MPs, with an overall trend of increasing stress from combined pollution with increasing Cd content and accumulation. High-throughput sequencing analysis revealed that combined MP and Cd pollution increased bacterial diversity, and the most significant increase was observed in the abundance-based coverage estimator (ACE), Shannon, and Sobs indices in the 13 μm 1% PS+Cd treatment group. Metagenomic analysis based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways revealed that 19 groups of metabolic pathways, including microbial metabolism and methane metabolism, differed significantly under combined MP and Cd pollution. Hierarchical clustering results indicated that Cd treatment and combined MP and Cd treatment affected the abundances of sorghum rhizosphere soil nitrogen (N) and phosphorus (P) cycling genes and that the type of MP present was an important factor affecting N and P cycling genes. The results of this study provide a basis for exploring the toxic effects of combined MP and Cd pollution and for conducting soil environmental risk assessments.

Hepatic oxidative stress is an important mechanism of Cd-induced hepatotoxicity, and it is ameliorated by TMP. However, this underlying mechanism remains to be elucidated. To investigate the mechanism of the protective effect of TMP on liver injuries in mice induced by subchronic cadmium exposure, 60 healthy male ICR mice were randomly divided into five groups of 12 mice each, namely, control (CON), Cd (2 mg/kg of CdCl2), Cd + 100 mg/kg of TMP, Cd + 150 mg/kg of TMP, and Cd + 200 mg/kg of TMP, and were acclimatized and fed for 7 d. The five groups of mice were gavaged for 28 consecutive days with a maximum dose of 0.2 mL/10 g/day. Except for the control group, all groups were given fluoride (35 mg/kg) by an intraperitoneal injection on the last day of the experiment. The results of this study show that compared with the Cd group, TMP attenuated CdCl2-induced pathological changes in the liver and improved the ultrastructure of liver cells, and TMP significantly decreased the MDA level (p < 0.05) and increased the levels of T-AOC, T-SOD, and GSH (p < 0.05). The results of mRNA detection show that TMP significantly increased the levels of Nrf2 in the liver compared with the Cd group as well as the HO-1 and mRNA expression levels in the liver (p < 0.05). In conclusion, TMP could inhibit oxidative stress and attenuate Cd group-induced liver injuries by activating the Nrf2 pathway.

Antioxidant responses of juvenile sole exposed to seawater acidification (SA) and Cd were investigated. SA increased lipid peroxidation (LPO) in the fish, independent of Cd concentrations. Cd at medium and high levels inflated LPO under no or moderate SA conditions. This effect was absent under high SA levels, due to SA effect exceeding and obscuring Cd effect. SA and Cd collaborated to provoke LPO, with SOD and CAT being stimulated to defend against oxidative stress, while those related to GSH redox cycle were inhibited under SA exposure. Responses of GSH-related antioxidants to Cd impact varied contingent on their interactions with SA. This defensive strategy was insufficient to protect fish from increased LPO. Antioxidants responded more sensitively to SA than Cd exposure. GSH, GR, SOD and CAT are sensitive biomarkers for SA conditions. The findings offer insights into assessing fish\'s antioxidant defense strategy under Cd and SA circumstances in natural habitats.