Cd Contamination Research Articles

Chloroplast-localized transporter OsNTP1 mediates cadmium transport from root to shoot and sugar metabolism in rice

Cadmium (Cd) is an element with high toxicity to living organisms, and its accumulation in rice grains poses a threat to human health. In this study, we report a novel nickel-transport family protein, OsNTP1, that is involved in Cd transport from root to shoot. Heterologous expression of OsNTP1 in yeast enhanced Ni and Cd tolerance. In rice, the transporter OsNTP1 is localized at the chloroplast and the expression of OsNTP1 was rapidly induced by Cd treatment. Under Cd²⁺ treatment, the Cd content in the shoots of OsNTP1-RNAi lines was significantly increased. Notably, knockdown of OsNTP1 significantly reduces Cd accumulation in the grains, highlighting its critical role in minimizing Cd contamination in edible parts of the plant. In addition, knockout or knockdown OsNTP1 also increased sensitivity to sucrose. Sucrose treatment led to more starch particles at the OsNTP1-RNAi shoot base, and exogenous sucrose can alleviate the inhibitory effects of Cd stress on sugar metabolism and starch synthesis in OsNTP1-RNAi lines. The present study provides a new genetic resource for breeding low-Cd grains and exploring the response mechanisms of sugar metabolism to Cd stress.

NP-bioTech: a circular economy approach to catalyst-based biostabilization of citrus processing waste.

Biowaste accounts for about 40% of total waste. Food-industry waste is one major biowaste stream. The available technological approaches to biowaste treatment are expensive, not circular, unsustainable, and they require pre-treatments such as dehydration, extraction of inhibitors, pH correction, or the addition of other organic matrices. The NP-bioTech process uses a biocatalyst adsorbed onto an inert material enabling accelerated fermentation of critical biomass without pre-treatments, transforming it into biostabilized and pasteurized material, and converting waste into new usable products rapidly. Biocatalysts consist of naturally fortified selections of microbial colonies, enzymes, and fungi that are resistant to the action of d-limonene and other fermentation inhibitors. The NP-bioTech process was able to activate vigorous fermentation of citrus waste without any of the pre-treatments required by other available biowaste-treatment technologies. The horticultural use of the biostabilized output of such process for greenhouse crops was verified. The addition of such output to the growth media was beneficial for plants and did not show negative effects on quality and yield of tomatoes (Lycopersicon esculentum L.). The concentration of Ca, K, Zn, Fe, and polyphenol increased; the average number of berries per plant was improved; the concentration of Pb and Cd contaminants decreased. The NP-bioTech process emits no odors or pollutants. It does not generate leachate, and its output can be used in agriculture. It is capable of reconciling compliance with strict environmental restrictions, industrial feasibility, and economic sustainability. Its potential impact thus aligns well with the circular economy model. © 2025 Society of Chemical Industry.

Effect of Speciation Transformation of Cadmium (Cd) on P-Wave Velocity Under Moisture Regulation in Soils.

This study aims to investigate the influence of cadmium (Cd) speciation transformation on P-wave velocity under different soil moisture conditions, providing critical insights into the subsurface characteristics of contaminated soils. Taking Cd-contaminated soil as the research subject, P-wave velocity and the speciation distribution of Cd in soils with different moisture contents and Cd adsorption levels were measured. The results reveal that when the soil is contaminated by Cd, the porosity is altered and it eventually lead to change P-wave velocity. By increasing the moisture content of soils, the redox potential (Eh) rises and the pH decreases, which lead to the speciation transformation of Cd from carbonate-bound state (CAB), Fe-Mn oxide-bound state (FMO), and organic and sulfide-bound state (ORB) to the exchangeable state (EX). These transformations of Cd to EX result in the increase in soil porosity, which lead to the decrease in P-wave velocity. In addition, linear regression analysis was conducted the P-wave velocity (∆V) and the EX (∆EX) at various Cd adsorption levels. The analysis shows that there is a strong linear relationship between exchangeable Cd content and P-wave velocity, and the determination coefficient is about 0.9, which provides a reliable basis for monitoring soil Cd contamination by using P-wave velocity. This study provides valuable insights into the relationship between the speciation distribution of heavy metals in soil and the properties of acoustic wave.

Molecular and Proteomic Analyses of Effects of Cadmium Exposure on the Silk Glands of Trichonephila clavata.

Cadmium (Cd) is a pervasive heavy metal pollutant released into the environment through industrial activities such as mining, smelting, and agricultural runoff. This study aimed to investigate the molecular and metabolic impacts of Cd exposure on the silk glands of Trichonephila clavata, a species renowned for producing silk with exceptional mechanical properties. Cd accumulation in spider bodies and silk glands was significantly higher in the low- and high-Cd groups compared to controls, with a dose- and time-dependent increase. Oxidative stress markers, including superoxide dismutase, glutathione peroxidase, peroxidase, and malondialdehyde, were significantly elevated, indicating a robust stress response. Proteomic analysis identified 2498 proteins, with 227 differentially expressed between Cd-treated and control groups. Key metabolic pathways, including glutathione metabolism, cysteine and methionine metabolism, and amino acid biosynthesis, were significantly disrupted. Downregulation of enzymes such as glutathione synthase and S-adenosylmethionine synthetase highlighted oxidative imbalance and impaired sulfur metabolism, indicating disruptions in redox homeostasis and energy metabolism critical for silk production. These findings demonstrate that Cd exposure alters oxidative stress responses, disrupts key metabolic pathways, and impairs silk gland functionality at multiple molecular levels. This study advances the understanding of the impact of heavy metal stress on spider physiology and provides a foundation for further research on the ecological implications of Cd contamination.

Identification of Peanut Cultivars with Low Cadmium Contents and Their Rhizosphere Microbial Characteristics in Alkaline and Acidic Cadmium-Contaminated Fields

Employing crop cultivars with low cadmium (Cd) accumulation and high yield is an effective strategy for the sustainable and safe utilization of Cd-contaminated farmland. However, the current understanding of peanut cultivars, particularly under field conditions, is limited. This study identified low-Cd cultivars and their rhizosphere microbial characteristics in acidic and alkaline fields with moderate Cd contamination. The results indicated that cultivars LH11, FH1, LH14, and YH9414 exhibited low Cd accumulation and high yield, with kernel Cd content reduced by 27.27% to 47.28% and yield increased by 9.27% to 14.17% compared with cultivar SLH. Among them, FH1 was validated to achieve safe production in two fields. A unique microbial community was formed by the recruitment of diverse microbes, such as Alphaproteobacteria, Acidobacteria, Gemmatimonadetes, and Chloroflexi, to the rhizosphere soil of FH1, which might be associated with Cd immobilization and the promotion of plant growth. Functional predictions further validated these findings, revealing enhanced functional pathways in the FH1 rhizosphere related to microbial proliferation, Cd stabilization, and detoxification. This study provides valuable germplasm resources for safe agriculture of Cd-polluted soils and elucidates the rhizosphere microbial characteristics of different peanut cultivars under field conditions. These findings are important for the targeted management of contaminated farmland and ensuring safe food production.

Use of Hydroxyapatite Nanoparticles to Reduce Cd Contamination in Agricultural Soils: Effects on Growth and Development of Chenopodium quinoa Willd

Soil contamination and degradation have prompted extensive research into remediation techniques. A promising approach involves the use of nanoparticles, which can mitigate heavy metal contamination, such as cadmium (Cd), without adversely affecting crop development. This study evaluated the effects of hydroxyapatite nanoparticles (HANPs) on the growth of Chenopodium quinoa Willd. in soils contaminated with varying Cd contents (0, 5, 10, 25, and 50 mg/kg). The results indicated that HANPs enhanced early shoot development, particularly in soils with Cd concentrations ≥10 mg/kg, while significantly reducing Cd accumulation in plant tissues. HANPs also decreased Cd mobility in soil, retaining it in fractions less available for plant uptake. Germination rates differed between pot experiments and phytotoxicity assays, although the first demonstrated greater Cd immobilization in HANP-treated soils, resulting in reduced Cd translocation to quinoa shoots. These findings highlight the potential of HANPs as an effective tool for remediating Cd-contaminated soils, thereby improving soil pollution, crop safety, and quality for human consumption.

Evaluating a Soil Amendment for Cadmium Mitigation and Enhanced Nutritional Quality in Faba Bean Genotypes: Implications for Food Safety.

Soil amendments combined with low cadmium (Cd)-accumulating crops are commonly used for remediating Cd contamination and ensuring food safety. However, the combined effects of soil amendments and the cultivation of faba beans (Vicia faba L.)-known for their high nutritional quality and low Cd accumulation-in moderately Cd-contaminated soils remain underexplored. This study investigates the impact of a soil amendment (SA) on agronomic traits, seed nutrition, and Cd accumulation in 11 faba bean genotypes grown in acidic soil (1.3 mg·kg-1 Cd, pH 5.39). The SA treatment increased soil pH to 6.0 (an 11.31% increase) and reduced DTPA-Cd by 37.1%. Although the average yield of faba beans decreased marginally by 8.74%, it remained within the 10% national permissible limit. Notably, SA treatment reduced Cd concentration in seeds by 60% and significantly mitigated Mn and Al toxicity. Additionally, SA treatment enhanced levels of essential macronutrients (Ca, Mg, P, S) and micronutrients (Mo, Cu) while lowering Phytate (Phy)/Ca, Phy/Mg, and Phy/P ratios, thus improving mineral nutrient bioavailability. Among the genotypes, F3, F5, and F6 showed the most favorable balance of nutrient quality, and yield following SA application. This study provides valuable insights into the effectiveness of SA for nutrient fortification and Cd contamination mitigation in Cd-contaminated farmland.

Distinct response of nitrogen metabolism to exogenous cadmium (Cd) in river sediments with and without Cd contamination history.

The role of metal resistance on nitrogen metabolism function and community resilience against Cd is important for elucidating the evolutionary dynamics of key ecological functions in river ecosystems. In this study, the response of nitrogen transforming function to Cd exposure in river sediments from the Yangtze River Basin with varying levels of heavy metal contamination history (Cd-contaminated and Cd-free sediments) was compared to understand how Cd influenced nitrogen metabolism under varying metal resistance conditions. The results showed that chronic and persistent Cd pollution of sediments caused an elevation of transport efflux metal resistance genes (MRGs) and a reduction in the uptake MRGs, leading to a stronger tolerance to Cd for Cd-contaminated sediment than Cd-free ones. Specifically, denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA) respectively responded to Cd through different mechanisms. Exogenous Cd (5-100 mg kg-1) influenced denitrification rates (-70 %-100 % deviation to control group) by regulating key genera (Thiobacillus, Magnetospirillum, Sideroxydans etc.) and gene clusters for denitrification. Both adaptive nature of anammox bacteria and co-regulation of key genera (Candidatus_Scalindua, Candidatus_Jettenia, Planctomyces etc.) and gene hzsA were drivers of differential responses in sediments from various contamination history. Environmental factors rather than contamination history, key genera or genes were probably critical ones determining Cd-resistance in DNRA, being more tolerant to Cd in sediments with higher TOC and NH4+. Stimulation of N2O reduction process (genera Gemmatimonas and Gemmatirosa and genes nosZ) in Cd-contaminated sediments by exogenous Cd lowered N2O emission risk, whereas the reverse was true for Cd-free sediments. These results enrich our understanding about the linkages among MRGs and nitrogen reduction functions in river.

Enhancing Miscanthus floridulus remediation of soil cadmium using Beauveria bassiana FE14: Plant growth promotion and microbial interactions.

Soil heavy metal pollution presents substantial risks to food security and human health. This study focused on the efficiency of plant growth-promoting fungus-Beauveria bassiana FE14 and Miscanthus floridulus on the synergistic remediation of soil Cd contamination. Results revealed that B. bassiana FE14 significantly enhanced the growth of M. floridulus, substantially decreased Cd content in soil by 79.39 %, and modified enzyme activities (superoxide dismutase, peroxidase, and catalase) to alleviate Cd-induced oxidative stress in plants, determined by the physical and chemical indicators and enzyme activities of soil and plant. Based on microbiome analysis, this study also found significant changes in the composition, structure, and molecular ecological network of endophytic bacterial communities in roots, but this study had little effect on the bacterial and fungal communities in rhizosphere soil. In addition, the key genera (including Sphingomonas, unclassified_Comamonadaceae, Massilia, Bradyrhizobium, and Paraglomus) and key genes/enzymes (including cadC, zinc transporter, zinc and cadmium transporter, exoZ/Y/Z, catalase-peroxidase, superoxide dismutase, nitrite reductase, acid phosphatase, etc.) were involved in promoting plant growth and alleviating Cd stress. These findings revealed the potential of B. bassiana FE14 and M. floridulus working in synergy to enhance the phytoremediation efficiency of Cd-contaminated soils, thus presenting a promising approach for integrated plant-microbe remediation strategies.

Accumulation and distribution of cadmium at organic-mineral micro-interfaces across soil aggregates

Soil amendments are crucial in regulating cadmium (Cd) distribution as aggregates of varying sizes have different capacities to retain soil Cd. Directly observing the Cd distribution within aggregates and understanding their interactions with minerals and carbon at the submicron scale remain significant challenges. Pot experiments were conducted to assess the impacts of mineral, organic, and microbial amendments on the Cd distribution in soil aggregates using synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectroscopy and nano-scale secondary ion mass spectrometry (NanoSIMS). Our results revealed that different soil amendments exerted varying effects on Cd accumulation in soil aggregates. The mineral and microbial amendments facilitated the Cd transfer from the macroaggregates to the silt+clay fraction, while the organic amendment increased the Cd loading in the macroaggregates. Additionally, the mineral and microbial amendments reduced the binding of Fe oxides with microbial-derived peptides in the macroaggregates and enhanced the interaction of Fe oxides with plant-derived lignin in the silt+clay fractions. Furthermore, NanoSIMS analysis provided direct evidence that the mineral and microbial amendments decreased the association between Cd with carbon and minerals in the macroaggregates, while they enhanced the binding of Cd and Fe oxides in the silt+clay fractions. Collectively, our findings revealed that the mineral and microbial amendments promoted Cd transfer, enhancing the stability of Cd in the finer soil fractions and offering essential insights for developing agricultural management strategies to alleviate Cd contamination in paddy soils.

A Review of Potentially Toxic Elements in Sediment, Water, and Aquatic Species from the River Ecosystems.

There is concern over potential toxic elements (PTEs) impacting river ecosystems due to human and industrial activities. The river's water, sediment, and aquatic life are all severely affected by the release of chemical and urban waste. PTE concentrations in sediment, water, and aquatic species from river ecosystems are reported in this review. Among the PTEs, chromium (Cr), cadmium (Cd), lead (Pb), and nickel (Ni) revealed high pollution levels in water and aquatic species (fish and shellfish) at many rivers. The Karnaphuli, Ganga, and Lee rivers have high levels of Pb and Cd contamination, while the Buriganga and Korotoa rivers' water had notable Ni contamination. A number of rivers with PTEs showed ecological risk as a consequence of the sediment's potential ecological risk (PER), the pollutant load index (PLI), and the geoaccumulation index (Igeo). A comprehensive study suggests elevated PLI values in river sediments, indicating significant pollution levels, particularly in the Buriganga River sediment, marked by high Igeo values. The PER of the Shitalakshya and Buriganga rivers was marked as very high risk, with an Eir > 320, while the Dhaleshwari and Khiru rivers showed 'high risk', with 160 = Eir < 320. It was found that fish and shellfish from the Buriganga, Turag, and Swat rivers have a high concentration of Cr. PTE pollution across several river sites could pose health toxicity risks to humans through the consumption of aquatic species. The CR value shows the carcinogenic risk to human health from eating fish and shellfish, whereas an HI value > 1 suggests no carcinogenic risk. The occurrence of other PTEs, including manganese (Mn), arsenic (As), and nickel (Ni), significantly increases the ecological risk and concerns to aquatic life and human health. This study emphasises the importance of PTE toxicity risk and continuous monitoring for the sustainability of river ecosystems.

Enhanced Adsorption and Biomineralization of Cadmium and Arsenic in Irrigation Water by Biological Soil Crusts: The Key Roles of Iron/Manganese and Urea

Heavy metal pollution has become increasingly severe, with distinctive physiological characteristics of rice leading to significant accumulation of arsenic (As) and cadmium (Cd) in grains, posing serious health risks. Biological soil crusts (BSC) are common in paddy soils and exhibit a strong capacity to bind trace heavy metals. This study investigated the effects of exogenous iron (Fe)/manganese (Mn) and urea on the effectiveness of BSC (20 mg L−1) in removing As (2 mg L−1) and Cd (100 μg L−1) and analyzed the heavy metal distribution. Fe/Mn addition increased As adsorption by BSC from 51.2% to 83.0% but reduced Cd adsorption from 73.2% to 50.3%, whereas urea inhibited As uptake but enhanced Cd capture. Under co-contamination, the As removal ability of the BSC remained unchanged, but Cd removal improved. As was primarily present in the non-EDTA exchangeable fraction (79.0%), which increased to 96.4% and 85.8% in the presence of Fe/Mn, and urea, respectively. Cd was mainly in the sorbed fraction (51.6%), which increased to 61.0% with urea. These results confirm that BSC exhibits a strong ability to adsorb As and Cd under irrigated water with combined As and Cd contamination, iron/manganese and urea can also enhance this ability. The application of exogenous Fe/Mn providing the raw material for the mineralization process and the presence of urea enhancing the biological activity of the colonies. This study provides an eco-friendly strategy for remediating As and Cd in paddy fields.

Wheat Tends to Accumulate Higher Levels of Cadmium in the Grains than Rice under a Wide Range of Soil pH and Cd Concentrations: A Field Study on Rice-Wheat Rotation Farmland.

Dietary intake is a predominant pathway of human exposure to environmental Cadmium (Cd), but wheat (Triticum aestivum L.) has not received enough concerns for its risk of Cd contamination. A field survey of Cd-contaminated rice-wheat rotation farmlands in China provided detailed comparison of Cd accumulation capacity by rice and wheat grains. The results indicated that Cd-BCF of wheat grains (median values 0.42) were obviously higher than those of rice grains (median values 0.12) under wide soil Cd levels and pH ranges. Soil Cd levels rather than pH played a vital role on Cd accumulation by wheat grains, and high wheat grain Cd concentrations (0.12-0.13 mg kg⁻1) were even observed in mildly alkaline soil that normally have low Cd mobility. Dietary Cd exposure risks were assessed by the crop Cd exposure models considering different soil Cd content, pH and dietary structures of residents. The results indicated that the intake of wheat grains contributed 56.1-86.5% of total crop Cd exposure, with an increase in its contribution with the increase of soil pH. Residents favoring wheat would have a significant Cd exposure risk if consuming crops from soils with Cd levels above 0.41 mg kg⁻1, which was considerably lower than the current soil Cd risk screening value for alkaline soils (0.6 mg kg-1). Our findings indicate a high Cd accumulation capacity of wheat grains and consequent risk of dietary Cd exposure, which deserves further exploration on the correlation among soil Cd screening value, grain Cd limit value and its dietary exposure risk.

Abscisic acid improves the phytoremediation ability of the aquatic accumulator plant Nasturtium officinale R. Br. in cadmium‐contaminated soil

AbstractPrevious studies report significant contamination of farmland soil by cadmium (Cd). Cd contamination increases the risk of diseases after consumption of grain crops with high Cd levels. Hyperaccumulators or accumulators have been widely used to bioremediate Cd‐contaminated farmland soil. Studies report that aquatic hyperaccumulators or accumulators are rarely used in phytoremediation, or their phytoremediation efficiencies are low. A pot experiment was carried out to explore the effects of abscisic acid (ABA) on the Cd accumulation (phytoremediation) of emerged aquatic accumulator plant Nasturtium officinale R. Br. Abscisic acid application increased the shoot biomass, peroxidase (POD) activity, superoxide dismutase (SOD) activity, catalase (CAT) activity, and soluble protein content of N. officinale under Cd‐contamination condition. The application of ABA at 5, 10, and 20 μmol/L increased the chlorophyll and carotenoid contents in N. officinale. The application of ABA also increased the shoot Cd content and shoot Cd extraction of N. officinale. The application of ABA at 1, 5, 10, and 20 μmol/L increased the shoot Cd extraction by 11.65%, 25.27%, 37.91%, and 58.52%, respectively, compared with the control. In addition, ABA concentration had a linear regression relationship with the root biomass, shoot biomass, root Cd extraction, and shoot Cd extraction. Correlation, gray relational, and path analyses showed that the root biomass, shoot biomass, root Cd extraction, root Cd content, POD activity, SOD activity, and soluble protein content were significantly associated with the shoot Cd extraction. These findings indicate that ABA application can improve the phytoremediation ability of N. officinale under Cd‐contaminated flooded fields.

Effects of Cd-Treated Pepper on Gut Microbiota in Herbivore Cutworm Spodoptera litura

The contamination of farmland soil with cadmium (Cd) poses a significant threat to the safety and quality of agricultural products. Herbivorous pests may develop adaptations to survive in Cd-contaminated farmland over time, potentially leading to population outbreaks. The gut microbiota plays a crucial role in this adaptation process, though the mechanisms involved remain unclear. This study examined the effects of two pepper cultivars of Capsicum annuum (Chiyan, CY, and Tianlanse, TLS) under Cd contamination on larval growth, development, food utilization, and gut microbiota of Spodoptera litura larvae. The inherent toxicity of TLS is higher than that of CY, as evidenced by a significant reduction in larvae survival rate in the control. In CY, Cd had a positive effect on larvae at low concentrations and a negative effect at high concentrations. Briefly, 5 mg/kg Cd of CY increased the efficiency of conversion of ingested food (ECI) and relative growth rate (RGR), whereas 10 mg/kg Cd decreased larvae growth and nutritional indices [higher relative consumption rate (RCR), approximate digestibility (AD), and lower efficiency of conversion of digested food (ECD)]. In TLS, Cd had a significant, dose-dependent, negative effect on larvae weight, ECD, and relative growth rate (RGR). Cd thus increased the negative effects of the plant toxins on the larvae. Meta-barcode sequencing of the 16S rRNA gene revealed that microbial diversity was affected by pepper cultivar but not Cd concentration. In larvae fed on CY, the most frequent bacterial genera were Enterococcus and Pluralibacte, whereas Enterococcus was the predominant genus in TLS larvae. Our findings reveal variations in how Cd impacts S. litura larvae across different pepper cultivars and imply that alterations in gut microbial communities could play a role in the joint detoxification of Cd and plant-derived toxins.

Activation of antioxidant enzymes as a mechanism against cadmium stress in Mimosa scabrella

Among the elements that cause serious consequences to the environment and to living beings, cadmium (Cd) is considered one of the most harmful. When reaching high levels of Cd contamination in an area, vegetation suppression can occur. Thus, the objective was to analyze the effects of Cd on morphological and biochemical variables of Mimosa scabrella, in order to evaluate its potential for use in environments polluted by Cd. M. scabrella seedlings were grown in five concentrations of Cd (0, 25, 50, 75 and 100 µM). The morphological variables of leaves and roots, photosynthetic pigments, antioxidant enzyme activity, as well as the content of hydrogen peroxide and lipid peroxidation (MDA) were evaluated. No negative effects were observed on the total length and surface area of roots at concentrations lower than 75 µM Cd. Cd stress activated enzymatic antioxidants, mainly in roots of M. scabrella seedlings, thus causing maintenance in the production of biomass of roots and shoot of seedlings. Thus, the species tolerated high concentrations of Cd and could be recommended for phytoremediation of soils contaminated with cadmium.

Promoters, Key Cis-Regulatory Elements, and Their Potential Applications in Regulation of Cadmium (Cd) in Rice.

Rice (Oryza sativa), a globally significant staple crop, is crucial for ensuring human food security due to its high yield and quality. However, the intensification of industrial activities has resulted in escalating cadmium (Cd) pollution in agricultural soils, posing a substantial threat to rice production. To address this challenge, this review comprehensively analyzes rice promoters, with a particular focus on identifying and characterizing key cis-regulatory elements (CREs) within them. By elucidating the roles of these CREs in regulating Cd stress response and accumulation in rice, we aim to establish a scientific foundation for developing rice varieties with reduced Cd accumulation and enhanced tolerance. Furthermore, based on the current understanding of plant promoters and their associated CREs, our study identifies several critical research directions. These include the exploration of tissue-specific and inducible promoters, as well as the discovery of novel CREs specifically involved in the mechanisms of Cd uptake, transport, and detoxification in rice. Our findings not only contribute to the existing knowledge base on genetic engineering strategies for mitigating Cd contamination in rice but pave the way for future research aimed at enhancing rice's resilience to Cd pollution, ultimately contributing to the safeguarding of global food security.

Ecological risk and chemical speciation of heavy metals in surface sediments of the Pearl River Estuary for comprehensive assessment

The Pearl River Estuary, a vital ecological and economic zone in Southern China, has been heavily impacted by industrial discharges, leading to significant heavy metal contamination. To address the ecological implications of different chemical forms of heavy metals, this study systematically evaluated the total concentrations and chemical speciation of Cu, Zn, Cd, and Pb in surface sediments (0–2 cm) collected from 17 sites. Chemical speciation was determined using a modified BCR sequential extraction procedure, and pollution and ecological risks were assessed via the geo-accumulation index (Igeo), potential ecological risk index (RI), and risk assessment code (RAC). The results showed that all four metals exceeded background values, with Cd presenting the highest enrichment (39 times) and contributing 97% of the ecological risk. Speciation analysis revealed that Cd predominantly exists in bioavailable forms, posing severe ecological threats. This study highlights the urgent need for targeted remediation strategies to mitigate Cd contamination and its ecological impact on the estuary.

Coupling a process-driven model with geographic information system enables the spatial predication of cadmium in paddy soils

Policies on the management of paddy fields are usually made at a broad scale and from a long-term perspective, while predicting the spatial extent of cadmium (Cd) contamination in paddy soils remains challenging. In this study, we developed a process-driven spatial model to quantify the transport of Cd in paddy soils and validated it against observed data from a 10-year regional investigation in southern China. Using a geographic information system and Monte Carlo simulation, the model was then applied to evaluate the effectiveness of different remediation strategies for contaminated paddy fields at field-to-regional scales in a 100-year period. In the last decade, atmospheric emissions have accounted for 43.5 % of the total Cd input in local paddy soils. However, the local clean air act failed to mitigate Cd contamination in 99.8 % of study area over the period of 2020–2120 because straw return became the dominant contributor to Cd inputs. Improving aerosol emission reductions by 3 % per year, stopping straw return to soil, and cleaning irrigation channels would take approximately 30 years (2020–2050) to protect 95 % of local rice production from causing an excessive human Cd kidney burden, especially in the paddy fields located in mining-affected areas.

Enhancing soil quality in soybean cultivation: Mycorrhizal technology combined with intercropping under high cadmium stress.

Cadmium (Cd) contamination presents a serious challenges for sustainable agriculture. This study evaluated the combined impact of arbuscular mycorrhizal fungi (AMF) inoculation and intercropping with Solanum nigrum on soil microbial diversity, enzyme activity, and environmental factors in soybean cultivation under high Cd stress. The combined treatment effectively reduced bioavailable Cd in soil, with the acid-soluble Cd fraction at 19.57 mg/kg and the reducible Cd fraction at 61.35 %, resulting in safe soybean grain Cd levels (2.63 mg/kg, below the 3 mg/kg organic standard). Illumina NovaSeq sequencing analysis revealed that key bacterial taxa, including Bradyrhizobium and PMMR1, were correlated with reduced Cd uptake in grains. Although bacterial α diversity increased, microbial network stability decreased in response to Cd, AMF inoculation, and intercropping. The combined treatment also enhanced soil enzyme activity by regulating the relative abundance of dominant or key genera such as Subgroup_6, Rokubacteriales and Pseudarthrobacter. Notably, catalase activity was 97.25 % higher in the combined treatment compared to monoculture without AMF colonization under high Cd conditions. These findings demonstrate the synergistic potential of AMF inoculation and S. nigrum intercropping as a sustainable approach to mitigate Cd contamination in crops while improving soil health in Cd-contaminated environments.