Search Results (129)

Cadmium (Cd) contamination in paddy soils poses a severe threat to food safety. Although straw incorporation is a key approach to sustainable agriculture, the mechanisms underlying its regulatory effects on safe rice production in Cd-contaminated fields remain unclear. This field study, conducted at two Cd-contaminated sites with two rice cultivars differing in Cd accumulation (low-Cd ZLY8612 and high-Cd YXY2115), evaluated five wheat straw management practices: straw removal (CK), straw mulching (SM), straw incorporation (SI), straw incorporation with organic fertilizer (SOI), and straw-derived biochar incorporation (SBI). The primary findings revealed that SOI and SBI could effectively reduce Cd availability and promoted Cd transformation to residual fractions, with SBI showing superior immobilization effects. SBI also enriched beneficial taxa (Bacillus, Sphingomonas, and Flavisolibacter), increased Proteobacteria, and reduced Chloroflexi and Acidobacteriota. All treatments enhanced rice yield; however, only SBI reduced grain Cd in the high-Cd cultivar to <0.2 mg/kg with high-Cd soil. Collectively, the combined application of straw-derived biochar incorporation and low-Cd-accumulating rice cultivar is a reliable and recommendable agronomic strategy for safe grain production and sustainable straw recycling in Cd-contaminated rice–wheat rotation fields. Full article

To investigate the contamination status, sources, spatial distribution, and health risks of heavy metals in paddy soils of Hexian County, 63 surface soil samples were analyzed for eight metals. Multiple pollution indices and multivariate statistical methods were applied to evaluate contamination levels and identify potential sources. Source apportionment was conducted using principal component analysis (PCA) combined with correlation analysis and spatial distribution characteristics. Results showed variable concentrations of heavy metals, with arsenic, copper, and lead exhibiting relatively higher single-factor pollution indices. The Nemerow pollution index (PN) ranged from 0.86 to 3.05 (mean = 1.16), indicating overall slight to moderate pollution, with localized areas showing higher pollution levels. The potential ecological risk index (RI) ranged from 28.06 to 66.45 (mean = 35.66), which was well below the threshold of 150, indicating a low ecological risk. Health risk assessment indicated negligible non-carcinogenic risks for both children and adults. Although carcinogenic risks remained within acceptable limits, children exhibited higher susceptibility, suggesting potential long-term concerns. Overall, these findings provide scientific evidence for targeted pollution control and risk-based agricultural management in Hexian County, and offer practical implications for mitigating heavy metal contamination and protecting agricultural sustainability in regions along the lower Yangtze River. Full article

Cadmium (Cd) contamination in paddy soils threatens food security by accumulating in rice grains. This study aimed to elucidate Cd-accumulation mechanisms using major japonica cultivars from Liaoning Province, a key northern Chinese rice-producing region where systematic comparisons remain limited. Four Liaoning japonica varieties (low-Cd: YF47, SN9903; high-Cd: QTXT, TJ) were analyzed for Cd accumulation, physiological responses, including malondialdehyde (MDA), superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and expression of Cd-related transporter genes under Cd stress. Cd distribution in rice plants followed the following order: root > stems and leaves > grain. Varietal differences were attributed to root-to-shoot transport rather than root uptake, as low-Cd varieties exhibited lower transport coefficients and higher root Cd retention. Low-Cd varieties showed smaller MDA increases and significantly higher SOD and CAT activities under Cd stress. Notably, OsLCD was significantly down-regulated in low-Cd varieties but up-regulated in high-Cd varieties, an opposite regulation pattern that clearly distinguishes the two groups. The root-to-shoot translocation process and the OsLCD expression pattern are key determinants differentiating low- from high-Cd japonica varieties. These findings provide region-specific mechanistic insights and screening indicators for breeding low-Cd rice in northern China. Full article

Cadmium (Cd) contamination in rice paddies poses serious threats to food safety. This study investigated the effects of bamboo biochar, a microbial agent, and their combination on Cd accumulation, soil properties, and rhizosphere microbial communities in the rice cultivar ‘Ning 47’ (Oryza sativa L.) under Cd stress (20 mg·kg⁻¹). Cd stress significantly reduced plant height, root length, and yield. However, combined treatment with biochar and microbial agent (CdMB) effectively mitigated these effects, reducing Cd content in grains, stems, and roots by 85.98%, 88.66%, and 73.89%, respectively, compared to Cd treatment alone. The CdMB treatment also significantly increased soil organic matter and total nitrogen content while decreasing soil Cd levels by 88.38%. Network analysis identified Flavisolibacter as a keystone taxon under CdMB treatment, indicating enhanced microbial network stability. This also provides a theoretical reference for the management of heavy metal contamination in agricultural soils. By reducing grain Cd contamination and enhancing soil health, this integrated approach addresses key targets of the United Nations Sustainable Development Goals, including SDG 2 (Zero Hunger), SDG 3 (Good Health and Well-being), and SDG 15 (Life on Land). Full article

Thallium (Tl) and cadmium (Cd) are highly toxic heavy metals that frequently co-occur in sulfide ores, posing a serious food safety risk through accumulation in rice. Although calcium-based (Ca-based) amendments have been widely applied to remediate heavy metal-contaminated soils, their effectiveness in Tl–Cd co-contaminated paddy soils remains unclear. A pot experiment was conducted to evaluate four Ca-based amendments—limestone powder, dolomite powder, hydrated lime, and oyster shell powder—on Tl and Cd bioavailability and uptake in paddy soil near a mining area. Ca-based amendments effectively reduced Tl and Cd bioavailability, with DTPA-Tl reducing by 11.2–17.2% and DTPA-Cd by 8.9–21.3%. These reductions were attributed to increased soil pH and decreased DOC, Fe, and Mn in the pore water. Additionally, Ca-based amendments shifted Tl and Cd from acid-extractable to residual fractions, reducing mobility. Additionally, Ca-based amendments promoted Fe/Mn plaque formation on rice roots, reducing Tl and Cd uptake. Consequently, Tl and Cd concentrations in brown rice decreased by over 14%, with the lowest levels observed under oyster shell powder. However, Cd concentrations still exceeded the maximum permissible limit, indicating that, although Ca-based amendments show considerable potential for in situ remediation of Tl–Cd co-contaminated paddy soils, further optimization and additional measures are required to achieve safe production. Full article

The release of heavy metals into the environment due to human activities is increasing, and this has led to concern about heavy-metal contamination on farmland. Prior studies have primarily focused on short-term investigations or specific pollution sources, lacking systematic monitoring of cadmium’s long-term input-output fluxes and their mass balance at the scale of a complete farmland ecosystem. This study clarified the cadmium (Cd) pollution trends for a typical paddy system in southern China. A six-year long-term monitoring study (2019–2024 inclusive) of a Cd-contaminated paddy system in Ningxiang City, Hunan Province, China, was conducted. The Cd flux dynamics for three input pathways (atmospheric deposition, irrigation water, and fertilizer) and three output pathways (crop harvesting, surface runoff, and subsurface infiltration) were investigated. The results showed that atmospheric deposition is the primary source of Cd input, accounting for 76% of total inputs, and leads to persistent net accumulation of soil Cd. Straw removal serves as the dominant output mechanism, facilitating substantial Cd removal, representing 77% of total Cd exports, while straw retention significantly reduces export fluxes. The study found that the net Cd fluxes from 2019 to 2024 were 1.994, 2.624, 8.984, 11.299, 9.944, and 20.162 g·(hm²·a)⁻¹, straw removal was primarily adopted during the period. A net flux analysis showed that progressive soil Cd accumulation had occurred over the study period. The results suggest that science-based straw management is critical when attempting to mitigate soil Cd pollution and enhance safe land utilization. These findings can be used to improve region-specific pollutant source control strategies and soil management policies. Full article

Cadmium (Cd) contamination in paddy soils threatens rice production and food safety. This study investigated the effects of manganese (Mn)-enriched biochar on soil Cd immobilization and Cd accumulation in rice using a pot experiment with Cd-contaminated soil. Unenriched biochar and Mn-enriched biochar prepared from rice straw were applied at two rates (0.5% and 1.0%). Both biochar types significantly increased soil pH and organic matter and promoted the transformation of Cd from labile fractions to more stable residual forms, thereby reducing Cd bioavailability. As a result, Cd accumulation in rice tissues, including straw and brown rice, was significantly reduced. Correlation analysis further indicated that increased soil pH was associated with reduced Cd mobility and plant uptake. Mn-enriched biochar markedly increased Mn accumulation and uptake efficiency in rice while decreasing Cd uptake efficiency, indicating a strong antagonistic interaction between Mn and Cd in the soil–plant system. Notably, a low application rate of Mn-enriched biochar (0.5%) achieved Cd reduction effects comparable to those of a higher dose of unenriched biochar (1.0%). These results suggest that Mn-enriched biochar is an effective and potentially cost-efficient strategy for reducing Cd bioavailability in paddy soils and mitigating Cd accumulation in rice. Full article

Rice is a globally important food crop, and its production is often affected by extreme climates such as drought and high temperatures. This study investigated how drought applied at different growth stages affects cadmium (Cd) uptake and accumulation in rice, as well as the underlying mechanisms. The results showed that drought treatments generally increased soil organic matter and alkali-hydrolyzed nitrogen content but decreased pH and available phosphorus content. The available Cd content in soil under the grain-filling stage drought treatment was lower than that under other treatments. Speciation analysis showed that under grain-filling stage drought, exchangeable Cd decreased by 3.04%, and residual Cd increased by 2.67%. Furthermore, drought treatments significantly enhanced soil urease and sucrase activities. Rice plant height and yield were significantly affected by the timing of drought, with the grain-filling stage drought treatment yielding the highest, while full growth stage and tillering stage drought treatments resulted in significantly lower yields. Cd content in various organs followed the order: root > stem > leaf > brown rice, with the brown rice Cd content being the lowest under grain-filling stage drought. In conclusion, drought treatment during the grain-filling stage had the least effect on Cd content in various rice tissues while maintaining a relatively high yield, providing a theoretical basis for water management in Cd-contaminated paddy fields. Full article

The co-occurrence of microplastics (MPs) and cadmium (Cd) in agricultural soils poses ecological risks, yet their interactions in flooded rice paddies remain unclear. Therefore, this study investigated the individual and combined effects of polyethylene MPs (mPE) and Cd on rice (Oryza sativa L.) growth, Cd accumulation, and soil microbial communities. Combined stress (5 mg/kg Cd + 1% mPE) significantly reduced rice growth (4.1–13.8% in plant height) and increased Cd accumulation in roots, stems, and seeds, driven by MP-enhanced Cd bioavailability. MPs altered soil pH, organic matter (OM), and moisture content (MC), indirectly suppressing yield. Microbial analysis revealed decreased bacterial alpha diversity (0.86–8.36%), favoring Cd-tolerant taxa (e.g., Solirubrobacteraceae), while fungal responses were weaker under flooding. Structural equation modeling indicated that Cd exerted direct toxicity through tissue accumulation, whereas MPs acted indirectly by modifying soil properties and inducing oxidative stress. Under co-exposure, MPs intensified Cd-induced oxidative stress, enhancing both direct and indirect toxicity pathways. Mantel tests identified DTPA-extractable Cd (r = 0.70) and OM (r = 0.55) as key drivers of Cd uptake. These findings highlight the complex interplay of MPs and Cd in rice paddies, with implications for managing co-contaminated agroecosystems. Full article

This study investigated the remediation effects of iron-modified biochar (FeBC-1 and FeBC-2) on arsenic (As) and cadmium (Cd) co-contaminated paddy soil and elucidated the underlying mechanisms from the perspectives of rhizosphere microbial ecology and plant As and Cd accumulation. A pot experiment with rice was conducted, comprising a control (CK) and iron-modified biochar treatments (FeBC-1 and FeBC-2). Parameters such as As and Cd speciation in rhizosphere soil, bacterial community composition, and the abundance of As-related functional genes were analyzed. The results demonstrated that iron-modified biochar reduced As and Cd accumulation in rice grains by promoting the formation of iron plaques on root surfaces. Meanwhile, the iron-modified biochar significantly enhanced the alpha diversity of bacterial communities and altered their composition. Quantitative analysis of functional genes revealed that the abundance of the As oxidase gene (aioA) increased from 3.54 × 10⁵ in the CK treatment to 7.20 × 10⁵ in FeBC-1 and 7.14 × 10⁵ in FeBC-2, and the abundance of the As efflux gene (arsA) decreased in the biochar-treated groups. These results indicate reduced As bioavailability in the rhizosphere and enhanced transformation of As(III) to As(V). Full article

To explore the effects of Fe/P-loaded biochar on neutral Cd-contaminated paddy soils and the potential synergistic effects between biochar and modifying materials, a pot experiment was conducted using neutral paddy soil with a total Cd concentration of 1.10 mg/kg. Ball milling was employed for modified biochar production. Specifically, iron-loaded biochar (PBCFe) and phosphorus-loaded biochar (PBCP) were prepared using Fe₂O₃ and K₃PO₄, respectively. Results showed that PBCP significantly increased rice biomass while effectively inhibiting Cd uptake and accumulation in rice grains. Compared to the control (CK), P (K₃PO₄), and PBC treatments, the Cd content in rice grains under PBCP treatment decreased by 69.20%, 52.13%, and 56.06%, respectively. Moreover, compared with the treatments using single modifiers, PBCP and PBCFe effectively reduced Cd uptake and accumulation in rice tissues, especially in leaves and stems. In contrast, PBCP was more effective than PBCFe in enhancing iron plaque formation and Cd adsorption onto iron plaque. This promoted Fe uptake in rice roots, which might inhibit the upward translocation of Cd from roots to stems. Further analysis with FTIR and XPS results indicated that PBCP might be more compatible in immobilizing Cd in soil by inducing Cd-P co-deposition. Therefore, phosphorus-loaded biochar (PBCP) could be a more promising amendment for remediating Cd-contaminated alkaline rice paddy soils and improving rice quality. Full article

Microplastics (MPs) enter terrestrial ecosystems through various pathways, including the use of plastic mulching films, treated sewage sludge, and chemical and organic fertilizers. Polypropylene (PP) and polyethylene (PE) are the dominant polymers found in both traditional and facility-based farmland soils. MPs negatively impact soil microbial communities and harm soil invertebrates such as earthworms, nematodes, and springtails. In plants, MPs can induce oxidative stress, damage cells and inhibit growth. Polystyrene (PS) is often identified as the most hazardous polymer, frequently linked to reduced plant growth, which is the most commonly reported effect of soil MP contamination. This review provides novel insights beyond those reported in the previous literature, revealing that greenhouse-based cultivation, vegetable crops, orchards, and vineyards are significant contributors to increased microplastic soil contamination. Furthermore, the findings underscore pronounced global heterogeneity in microplastic concentrations within paddy soils, with recorded levels varying widely from 16 to 10,300 items kg⁻¹. Oxidative stress and additive leaching are the dominant mechanisms driving soil microplastic toxicity across exposed organisms. Quantitative studies of fungal-mediated microplastic biodegradation report mean degradation efficiencies of ~7.5% after 50 days, with mass losses of ~23.8% after 30 days and 35–38% after 90 days. Full article

Polyethylene (PE) mulching has been widely practiced in agriculture for decades, but its short-term impacts on heavy metal dynamics and crop safety under field conditions remain poorly understood. In this study, a one-season field trial was carried out in Cd-contaminated paddy to evaluate how PE mulching influences rhizosphere microbial communities, soil physicochemical properties, and Cd accumulation in rice. Results showed that PE mulching improved rice performance, increasing dry grain weight by 14.47% and thousand-grain weight by 1.10 folds, while reducing grain Cd concentration from 0.2307 to 0.1727 mg/kg, below the national safety threshold of 0.2 mg/kg. These effects were closely linked to elevated soil pH, decreased redox potential, and the enrichment of metal-reducing (Geobacteraceae, Desulfuromonadia) and sulfate-reducing (Desulfosporosinus, Methanospirillum) taxa, which promoted Cd immobilization into less bioavailable forms. A structural equation model (SEM) further confirmed that microbial abundance and Cd speciation were key factors associated with Cd uptake by rice. However, PE mulching also reduced microbial diversity and functional redundancy, disrupted co-occurrence networks, and potentially weakened rhizosphere ecosystem stability and resilience in the short term. This study provides field-based evidence that PE mulching reduces food safety risks and improves yield but destabilizes soil microbial communities, highlighting its short-term double-edged ecological effects and the need for balanced management to sustain productivity and soil health. Full article

Rice (Oryza sativa L.) readily accumulates cadmium (Cd), posing dietary exposure risks in populations dependent on rice-based diets. This study investigated how sulfur (S) redox processes regulate Cd mobility in S-deficient, Cd-contaminated paddy soil under waterlogged conditions. A pot experiment was conducted with two S treatments (−S and +S, 30 mg kg⁻¹) throughout the rice growing season. S addition markedly increased pore water S²⁻ concentrations during early growth (tillering) and mid-season (booting) and suppressed the diffusion of SO₄²⁻ from non-rhizosphere to rhizosphere at later stages (filling–maturity). Consequently, Cd in soil pore water was significantly lower in +S than −S treatments at all stages. Sulfur-amended soil showed a redistribution of Cd from labile fractions (exchangeable and carbonate-bound) to more stable fractions (Fe/Mn oxide-bound). Sulfur application also altered the rhizosphere microbiome: the relative abundance of sulfate-reducing bacteria (SRB) increased at the booting and filling stages, while sulfur-oxidizing bacteria (SOB) became more dominant at maturity. Additionally, +S enhanced Cd sequestration on rice root iron plaque by 32–67% during the grain-filling and maturity stages compared to −S. Throughout the rice growing period, redox-driven shifts in the S²⁻/SO₄²⁻ ratio emerged as a key control on Cd behavior, with low pe + pH (strongly reducing conditions) promoting Cd sulfide precipitation and high pe + pH (more oxidizing conditions) causing Cd remobilization. Full article

Arsenic (As) contamination in paddy soils poses a serious risk to rice safety and human health. To mitigate this issue, we developed a low-temperature, partially pyrolyzed Fe/Mn/Mg-modified biochar (FMM-BC) and evaluated its performance and mechanisms for remediating As-contaminated soil through a pakchoi–rice rotation pot experiment, aiming to reduce As accumulation in rice grains and pakchoi. The results indicated that FMM-BC application altered soil physicochemical properties and As speciation, reducing both water-soluble and bioavailable As and promoting its transformation from exchangeable to more stable organic-bound and residual fractions. Compared with the control, FMM-BC application reduced arsenic content in rice stems, leaves, and brown rice to 1.94 mg∙kg⁻¹, 5.24 mg∙kg⁻¹, and 1.21 mg∙kg⁻¹, respectively. In contrast, unmodified biochar (BC) increased As bioavailability and plant uptake, underscoring the importance of Fe/Mn/Mg modification. FMM-BC also enhanced the translocation of Fe, Mn, and Mg within rice plants, thereby modifying internal As transport dynamics and suppressing its accumulation in aboveground tissues. Under FMM-BC treatment, arsenic content in pakchoi stems and leaves decreased to 1.19 mg∙kg⁻¹ (vs. 1.96 mg∙kg⁻¹ in the control), and brown rice declined to 0.27 mg∙kg⁻¹ (vs. 1.49 mg∙kg⁻¹ in the control)—well below the national food safety threshold (0.35 mg∙kg⁻¹). These findings demonstrate that FMM-BC effectively stabilizes As in contaminated soils and reduces its transfer to edible plant parts, with Fe/Mn/Mg playing a key role in enhancing As immobilization and limiting its mobility within the soil–plant system. Full article