Cd Bioconcentration Factor Research Articles

Significant alleviation of cadmium toxicity in Thalassiosira weissflogii through the combined effect of high silicon and zinc supplementation

Cadmium (Cd), a prevalent pollutant in near-shore seawater ecosystems, poses a significant threat to marine biota. Zinc (Zn) and Cd can have interchangeable physiological effects in marine plankton, and both can influence the synthesis of siliceous walls. Consequently, the concentrations of zinc and silicon may jointly impact the toxicity of Cd. This study endeavors to elucidate the combined effect of silicon (Si) and zinc (Zn) on the growth and physiological responses of the marine diatom species Thalassiosira weissflogii when subjected to Cd-induced stress conditions (190.7 μg L−1). Our results reveal statistically improvements (p<0.05) in biomass production, reductions (p<0.05) in superoxide dismutase (SOD) activity and extracellular secretion in T. weissflogii when high concentrations of Si (172 µmol L−1) and Zn (18.3 nmol L−1) were applied simultaneously. Additionally, examination of Cd bioconcentration factors (BCF) derived from Cd uptake kinetics and intracellular Cd content measurements underscores the ability of elevated Si and Zn concentrations to reduce intracellular Cd accumulation (p<0.05). The ability of Si and Zn to mitigate Cd toxicity was further evidenced by increased cellular biosilica content and maintenance of cell morphology, suggesting a protective role in preserving structural integrity and growth. Our findings underscore the synergistic benefits of Si and Zn in enhancing the resilience of T. weissflogii to Cd stress, providing valuable insights into the potential use of nutrient amendments as a strategy for mitigating heavy metal contamination in marine environments.

Characteristics of Soil Selenium-cadmium Migration and Accumulation and Its Bioeffectiveness in Typical Geological High Background Area

The prevalence of selenium-cadmium （Se-Cd） symbiosis in soils of geologically high background areas directly affects the safe utilization of Se-rich land resources. To investigate the migration and accumulation characteristics and bio-effectiveness of Se-Cd in the soil-crop system in typical geological high background areas of Southwest China and to realize the safe use of natural Se-rich land resources in geological high background areas, we collected 84 samples of agricultural crops （maize） and their supporting root systems and analyzed the Se-Cd content and physicochemical properties. Se-Cd accumulation characteristics, influencing factors, and bio-effectiveness of the soil-crop system were evaluated using geostatistics, bioenrichment factors, and geographic detectors. The results showed that the Se-Cd content in the study area was significantly higher than the background value of the soil in the whole country and in Yunnan Province. Influenced by the geological background, secondary enrichment in the process of soil formation, and agricultural activities, the accumulation and enrichment characteristics of Se in the root soil varied from no enrichment to slightly enriched, and the occurrence form was dominated by the residue state. The accumulation index of soil Cd was mainly in the medium pollution level, and the occurrence form was mainly in the residual state and the combined state of iron and manganese. The Se-enrichment rate of crop seeds reached 98.8% （DB 50/T 524-2013 standard）, and the average value of bioconcentration factor was 5.8%. The exceeding rate of Cd content in crop seeds was only 1.19% （GB 2762-2022 standard）, and the average value of Cd bioconcentration factor was 2.11%, so the ecological risk of heavy metal Cd in crop seeds was relatively low. In the Se-Cd symbiosis area under geological background, the weak alkaline environment of the soil could effectively reduce the bioavailability of Cd in crop seeds, and the Se-rich soil could inhibit the uptake of Cd by the crops to a certain extent. Correlation analysis showed that the migration and accumulation of Se and Cd from soil to crop seeds in the soil-crop system were affected by the elemental accumulation pattern and the physical and chemical properties （pH） of the soil, and at the same time, there was a certain synergistic-antagonistic effect between Se and Cd in the soil-crop system. Correlation analysis showed that the migration and accumulation of Se and Cd from soil to crop seeds in the soil-crop system was influenced by the occurrence of elements, soil physicochemical properties （pH）, and other factors, and there was also a certain synergistic-antagonistic interaction between Se and Cd in the soil-crop system.

Melatonin mitigates cadmium toxicity by promoting root development, delaying root senescence, and regulating cadmium transport in cotton

Cd ions are absorbed and transported from the soil by crop roots, which are the first organ to be exposed to Cd. This results in an increase in cadmium ions in crops, significantly affecting crop growth and yield. Exogenous melatonin (MT) can help reduce cadmium (Cd) stress in cotton, but the specific contribution of roots to this process remains unclear. In order to address this knowledge gap, an in-situ root phenotyping study was conducted to investigate the the phenotype and lifespan of roots under cadmium stress (Cd) and melatonin treatment (Cd + MT). The results showed that MT alleviated the decreases in plant height, leaf area, SPAD value, stem diameter, stomatal conductance and net photosynthetic rate under Cd stress, which further promoted the biomass accumulation in various cotton organs. What is more, the Cd + MT treatment increased root volume, surface area, and length under Cd stress by 25.63 %, 10.58 %, and 21.89 %, respectively, compared with Cd treatment. Interestingly, compared to Cd treatment, Cd + MT treatment also significantly extended the lifespan of roots and root hairs by 6.68 days and 2.18 days, respectively. In addition, Cd + MT treatment reduced the transport of Cd from roots to shoots, particularly to bolls, and decreased the Cd bioconcentration factor in bolls by 61.17 %, compared to Cd treatment. In conclusion, these findings show that applying MT externally helps reduce Cd stress by delaying root senescence, promoting root development and regulating Cd transport. This method can be an effective approach to managing Cd stress in cotton.

Biochar with KMnO4-hematite modification promoted foxtail millet growth by alleviating soil Cd and Zn biotoxicity

The excessive accumulation of Cd and Zn in soil poisons crops and threatens food safety. In this study, KMnO4-hematite modified biochar (MnFeB) was developed and applied to remediate weakly alkaline Cd-Zn contaminated soil, and the heavy metal immobilization effect, plant growth, and metal ion uptake of foxtail millet were studied. MnFeB application reduced the phytotoxicity of soil heavy metals; bioavailable acid-soluble Cd and Zn were reduced by 57.79% and 35.64%, respectively, whereas stable, non-bioavailable, residual Cd and Zn increased by 96.44% and 32.08%, respectively. The chlorophyll and total protein contents and the superoxide dismutase (SOD)activity were enhanced, whereas proline, malondialdehyde, the H2O2 content, glutathione reductase (GR), ascorbate peroxidase (APX) and catalase (CAT) activities were reduced. Accordingly, the expressions of GR, APX, and CAT were downregulated, whereas the expression of MnSOD was upregulated. In addition, MnFeB promoted the net photosynthetic rate and growth of foxtail millet plants. Furthermore, MnFeB reduced the levels of Cd and Zn in the stems, leaves, and grains, decreased the bioconcentration factor of Cd and Zn in shoots, and weakened the translocation of Cd and Zn from roots to shoots. Precipitation, complexation, oxidation-reduction, ion exchange, and π-π stacking interaction were the main Cd and Zn immobilization mechanisms, and MnFeB reduced the soil bacterial community diversity and the relative abundance of Proteobacteria and Planctomycetota. This study provides a feasible and effective remediation material for Cd- and Zn-contaminated soils.

Enhancing zinc biofortification and mitigating cadmium toxicity in soil–earthworm–spinach systems using different zinc sources

Cadmium (Cd) pollution poses significant threats to soil organisms and human health by contaminating the food chain. This study aimed to assess the impact of various concentrations (50, 250, and 500 mg·kg–1) of zinc oxide nanoparticles (ZnO NPs), bulk ZnO, and ZnSO4 on morphological changes and toxic effects of Cd in the presence of earthworms and spinach. The results showed that Zn application markedly improved spinach growth parameters (such as fresh weight, plant height, root length, and root-specific surface area) and root morphology while significantly reducing Cd concentration and Cd bioconcentration factors (BCF-Cd) in spinach and earthworms, with ZnO NPs exhibiting the most pronounced effects. Earthworm, spinach root, and shoot Cd concentration decreased by 82.3 %, 77.0 %, and 75.6 %, respectively, compared to CK. Sequential-step extraction (BCR) analysis revealed a shift in soil Cd from stable to available forms, consistent with the available Cd (DTPA-Cd) results. All Zn treatments significantly reduced Cd accumulation, alleviated Cd-induced stress, and promoted spinach growth, with ZnO NPs demonstrating the highest Cd reduction and Zn bioaugmentation efficiencies compared to bulk ZnO and ZnSO4 at equivalent concentrations. Therefore, ZnO NPs offer a safer and more effective option for agricultural production and soil heavy metal pollution management than other Zn fertilizers.

Potential toxic elements distribution and phytoextraction status of Avicennia marina in eastern coast of Sri Lanka

This research sought to evaluate the phytoextraction capability of Avicennia marina plants for potentially toxic elements (Cr, Ni, Co, Cu, As, Cd and Pb) in Batticaloa and Uppar lagoons along the east coast of Sri Lanka, thereby investigating its potential application in ecological restoration and coastal management. An experiment was conducted to identify the elemental concentration in roots above and below water level, stem and leaves of well grown Aicennia marina plants and sediment samples obtained along a transect from the plant to the deeper levels of the lagoon in six selected locations. The grain size distribution of sediments and organic geochemical proxies of sediments and plants were correlated with elemental distributions to identify their effect on the mobility. The average clay and silt contents of these lagoons are <1.03% with high contents of fine to medium size sands (about 66%). The pollution load indices (PLI) for both lagoons are low to moderate, however, Ni concentration exceeds Effect Range-median limit for some locations. The ecological risk indices and toxicity response of the sediments are in low risk levels may be due to the low development state of the region and sedimentary distributions. The elemental concentration in roots are high for Cr, Ni, Co, Cu and As compared to the stem and leaves of Avicennia marina whereas, Cd and Pb shows high values in stem parts regardless of the C/S and C/N ratios. The average bio concentration factor for Cr, As, Co, Ni, Cu, Pb and Cd are 31.77, 19.98, 17.33, 15.38, 4.57, 3.53 and 2.77 respectively indicating significant values compared to the most other studies which might be controlled by the climate.

Unveiling the variability in cadmium accumulation and tolerance characteristics: a comparative study of Basma and Yunyan 87 tobacco varieties

ABSTRACT Tobacco (Nicotiana tabacum L.) shows promise for remediating Cd-contaminated soil due to its significant Cd accumulation capabilities. Although various tobacco varieties exhibit distinct Cd bioaccumulation capacities, a comprehensive understanding of the underlying mechanisms is lacking. This study, conducted using hydroponics, explores differences in Cd accumulation and tolerance mechanisms between two tobacco varieties, Basma and Yunyan 87. The results showed that Cd stress reduced the dry weight, tolerance index, and root morphology for both varieties. Basma exhibited a relatively smaller decline in these indices compared to Yunyan 87. Moreover, Basma demonstrated a higher Cd bioconcentration factor (BCF), concentration, and accumulated content, signifying its superior tolerance and bioaccumulation capacity to Cd compared to Yunyan 87. The Carbonyl Cyanide3-ChloroPhenylhydrazone (CCCP) addition resulted in reduced Cd accumulation and BCFs in both tobacco species. This effect was more pronounced in Basma, suggesting that Basma relies more on an active transport process than Yunyan 87. This could potentially explain its enhanced bioaccumulation ability. Subcellular Cd distribution analysis revealed Basma's preference for distributing Cd in soluble fractions, while Yunyan 87 favoured the cell wall fractions. Transmission electron microscope showed that Basma's organelles were less damaged than Yunyan 87's under Cd stress, possibly contributing to the superior tolerance of Basma. Therefore, these results provided a theoretical foundation for development of Cd-contaminated soil tobacco remediation technology.

NH4+-N and Low Ratios of NH4+-N/NO3−-N Promote the Remediation Efficiency of Salix linearistipularis in Cd- and Pb-Contaminated Soil

(1) Background: the utilization of fast-growing trees for phytoremediation in heavy-metal-contaminated soil is increasingly recognized as an effective remediation method. Nitrogen (N) fertilizer enhances plant tolerance to heavy metals, yet the impact of various N levels and ammonium (NH4+-N)/nitrate (NO3−-N) ratios on the remediation of cadmium (Cd) and lead (Pb) by trees remains unclear. (2) Methods: the efficiency of Salix linearistipularis in remediating Cd- and Pb-contaminated soil was investigated using a pot experiment with three N levels (60, 120, 200 kg hm−1 year−1) and five NH4+-N/NO3−-N ratios (6/0, 4/2, 3/3, 2/4, 0/6) employed, resulting in 16 treatments including a control. (3) Results: the levels and ratios of NH4+-N/NO3−-N significantly affected the Cd and Pb uptake by S. linearistipularis. The highest increases in Cd and Pb in S. linearistipularis were observed for the N120-6/0 treatment, which increased by 104.36% and 95.23%, respectively. In addition, in the N120-6/0 treatment, the stem and leaf bioconcentration factors of Cd were significantly enhanced by 28.66% and 40.11%, respectively. Structural equation modeling revealed that the uptake of Cd and Pb was predominantly influenced by plant traits (biomass and root traits) rather than soil properties. (4) Conclusions: Our findings highlight the potential of the NH4+-N/NO3−-N ratio to regulate plant traits, thereby improving the phytoremediation efficiency of heavy-metal-contaminated soil.

Adesmia pinifolia, a Native High-Andean Species, as a Potential Candidate for Phytoremediation of Cd and Hg.

This study highlights Adesmia pinifolia, a native high-Andean species, as a potential candidate for the phytoremediation of soils contaminated with Cd and Hg. In this work, a semi-hydronic assay with different doses of Cd (3, 4.5, and 6 mg L-1) and Hg (0.8, 1.2, and 1.6 mg L-1) was analysed to evaluate the establishment of plants, antioxidant defence systems, oxidative stress, and the ability to accumulate heavy metals. The results indicate high survival rates (>80%); however, Cd significantly reduced shoot and root biomass, while Hg increased root biomass with the 1.6 mg L-1 treatment. Cd and Hg tend to accumulate more in roots (2534.24 µg/g and 596.4 µg g-1, respectively) compared to shoots (398.53 µg g-1 and 140.8 µg g-1, respectively). A significant decrease in the bioconcentration factor of Cd and Hg in roots was observed as metal levels increased, reaching the maximum value at 3 mg L-1 (805.59 ± 54.38) and 0.8 mg L-1 (804.54 ± 38.09). The translocation factor, <1 for both metals, suggests that translocation from roots to shoots is limited. An overproduction of reactive oxygen species (ROS) was observed, causing lipid peroxidation and oxidative damage to plant membranes. Tolerance strategies against subsequent toxicity indicate that enhanced glutathione reductase (GR) activity and glutathione (GSH) accumulation modulate Cd and Hg accumulation, toxicity, and tolerance.

Overexpression of vacuolar transporters OsVIT1 and OsVIT2 reduces cadmium accumulation in rice.

Excessive cadmium in rice grain in agricultural production is an important issue to be addressed in some southern regions of China. In this study, we constructed transgenic rice overexpressing OsVIT1 and OsVIT2 driven by 35S promoter in the cultivar ZH11. Compared with ZH11, OsVIT1 expression in leaves was significantly increased by 3-6.6 times and OsVIT2 expression in leaves was significantly increased by 2-2.5 times. Hydroponic experiments showed that overexpression of OsVIT1 and OsVIT2 increased the tolerance to Fe deficiency, significantly reduced Cd content in shoot and xylem sap, and had no effect on Cd tolerance in rice. Two years of field trials showed that the Fe content in the grain of OsVIT1 and OsVIT2 overexpressed materials was significantly reduced by 20-40% and the straw Fe content was significantly increased by 10-45%, and the grain Fe content distribution ratio was significantly decreased and the straw Fe distribution ratio was significantly increased compared with the wild type. The OsVIT1 and OsVIT2 overexpressed materials significantly reduced the Cd content of grain by 40-80% and the Cd content of straws by 37-77%, and the bioconcentration factor of Cd was significantly reduced in both grains and straw of OsVIT1 and OsVIT2 overexpressed materials. Overexpression of OsVIT1 and OsVIT2 did not affect the concentration of other metal ions in rice straw and grain. qRT-PCR analysis showed that the expression of the low affinity cation transporter OsLCT1 was significantly downregulated in the OsVIT1 and OsVIT2 overexpressed materials. In conclusion, overexpression of OsVIT1 and OsVIT2 reduced Cd accumulation in straw and grains, providing a strategy for Cd reduction in rice.

Cunninghamia lanceolata (Lambert) Hooker: A Promising Candidate for Phytoremediation of Cd-Contaminated Soils

Cadmium (Cd) is one of the most common toxic heavy metal elements in soil pollution, which can be continuously enriched in the food chain and eventually threaten human health. Phytoremediation, which is using plants to transfer heavy metal elements from soils, is a promising solution for the remediation of heavy metal-contaminated soils. In this study, we evaluated whether Cunninghamia lanceolata (Lambert) Hooker (Chinese fir), a widely planted timber tree worldwide, had the potential to remediate Cd-contaminated soils through 90 days pot of experiments with different Cd concentration soils (0, 5, 10, 20, 50, 100 mg kg−1). C. lanceolata did not show obvious toxic symptoms in Cd-contaminated soils, although Cd inhibited plant growth and decreased net photosynthetic rate slightly. The activities of antioxidant enzymes increased significantly under Cd stress, indicating that C. lanceolata had a strong self-regulation ability and can tolerate Cd stress. The Cd bioconcentration factor (Cd concentration in plant divided by Cd concentration in soil) of C. lanceolata were greater than 1 at all Cd concentrations, indicating that C. lanceolata had a strong ability to absorb Cd, although Cd was mainly accumulated in roots. Our results indicated that C. lanceolata had a strong tolerance and phytostabilization ability of Cd. Considering the wide distribution worldwide, large biomass, and rapid growth of C. lanceolata, it could be a promising candidate for phytoremediation of Cd-contaminated soils.

Chelate facilitated phytoextraction of Pb, Cd, and Zn from a lead–zinc mine contaminated soil by three accumulator plants

This study aims to evaluate the enhancement of phytoextraction of heavy metals (Pb, Cd, and Zn) by species Marrubium cuneatum, Stipa arabica, and Verbascum speciosum, through EDTA amendment. Assisted phytoextraction pot experiments were performed at different EDTA dosages (0, 1, 3, and 5 mmol kg−1 soil). The DTPA-extractable metal content increased in the presence of EDTA, followed by their contents in the tissues of all three studied species. Resulting from oxidative stress, the activity of antioxidant enzymes such as glutathione peroxidase (GPX), superoxide dismutase (SOD), and catalase (CAT) increased when the chelating agent was added. EDTA in higher doses partially decreased chlorophyll concentration, and 5 mmol kg−1 of that reduced the biomass of the studied species. The bioconcentration factor (BCF) for Cd was notably high in all studied plants and considerably elevated for Zn and Pb with the addition of EDTA in M. cuneatum and S. arabica (BCF > 1), whilst an accumulation factor greater than one (AF > 1) was found for Cd in all species and for Pb in the case of S. arabica. In general, the results demonstrated that EDTA can be an effective amendment for phytoextraction of Cd, Zn, and Pb by M. cuneatum, V. speciosum and S. arabica in contaminated soils.

Alkaline humic acid fertilizer alters the distribution, availability, and translocation of cadmium and zinc in the acidic soil–Sauropus androgynus system

Humic acids (HA) are a popular soil additive to reduce metal availability, but they have the drawbacks of reduced effectiveness over time and a significant reduction in soil pH. An alkaline humic acid fertilizer (AHAF) combining alkaline additives with HA was developed to overcome such drawbacks. A field experiment was conducted to investigate the effects of different AHAF application rates on the physicochemical properties, bioavailability, accumulation, and translocation of Cd and Zn heavy metals in Sauropus androgynus grown in acidic soil. Based on our results, the 100AF (100% AHAF) treatment significantly increased soil pH, cation exchange capacity (CEC), and organic matter content (OM) after one year of application. Compared with the control treatment (CK), the application of different rates of AHAF resulted in a 37.1–40.3% decrease in soil exchangeable Cd fractions (Exc-Cd) and an increase in the humic acid-bound Cd fractions (HA-Cd) Fe- and Mn-oxide-bound Cd fractions (OX-Cd), and organic matter-bound Cd fractions (OM-Cd) by 9.5–64.6%, 24.8–45.1%, and 158.8–191.2%, respectively (P < 0.05). The different AHAF treatments decreased the Res-Zn, Exc-Zn, and OM-Zn fractions by 69.6–73.0%, 7.4–23.9%, and 18.1–23.2%, respectively (P < 0.05), and increased the HA-Zn fraction by 8.4–28.1%. In the control treatment, the bioconcentration factors (BCFs) for Cd and Zn in different S. androgynus plant organs were in the following order: (Cd) Leaves > Stems > Branches > Roots > Edible branches; (Zn) Roots > Stems > Leaves > Branches > Edible branches. The transfer factors (TFs) of Cd and Zn in S. androgynus were classified as follows: TF2 > TF1 > TF3 > TF4. Thus, S. androgynus stems, and roots had a strong ability to transport Cd and Zn to the leaves. Compared with CK, the 100AF treatment significantly increased the BCFs for Zn in all plant parts (except BCFedible branches). In contrast, it significantly decreased all BCFs and TFs for Cd and the TF4 for Zn, effectively reducing Cd and Zn accumulation in the edible branches of S. androgynus. Soil pH, CEC, OM, and HA-M fraction were highly and significantly negatively correlated with Cd and Zn content in edible branches (P < 0.001). Stepwise multiple linear regression analysis revealed that the soil HA-M fraction was the key contributing factor for Zn accumulation and translocation in S. androgynus. Moreover, based on our findings, the absorption, uptake, and translocation of Cd and Zn were mainly determined by metal speciation and the pH in the soil. Moreover, the competitive antagonistic mechanisms between Zn and Cd absorption also affected their accumulation in S. androgynus. Thus, AHAF can be used as a soil amendment to sustainably improve acidic soils and effectively reduce Cd and Zn accumulation in edible branches of S. androgynus.

Increased Tolerance of Massion's pine to Multiple-Toxic-Metal Stress Mediated by Ectomycorrhizal Fungi.

Pinus massoniana (Massion's pine), a pioneer tree species, exhibits restoration potential in polluted mining areas. However, the physiological and molecular mechanisms of ectomycorrhizal (ECM) fungi in Massion's pine adaptability to multiple-toxic-metal stress are still unclear. Hence, Massion's pine seedlings inoculated with two strains of C. geophilum, which were screened and isolated from a polluted mine area, were cultivated in mine soil for 90 days to investigate the roles of EMF in mediating toxic metal tolerance in host plants. The results showed that compared with the non-inoculation control, C. geophilum (CG1 and CG2) significantly promoted the biomass, root morphology, element absorption, photosynthetic characteristics, antioxidant enzyme activities (CAT, POD, and SOD), and proline content of Massion's pine seedlings in mine soil. C. geophilum increased the concentrations of Cr, Cd, Pb, and Mn in the roots of Massion's pine seedlings, with CG1 significantly increasing the concentrations of Pb and Mn by 246% and 162% and CG2 significantly increasing the concentrations of Cr and Pb by 102% and 78%. In contrast, C. geophilum reduced the concentrations of Cr, Cd, Pb, and Mn in the shoots by 14%, 33%, 27%, and 14% on average, respectively. In addition, C. geophilum significantly reduced the transfer factor (TF) of Cr, Cd, Pb, and Mn by 32-58%, 17-26%, 68-75%, and 18-64%, respectively, and the bio-concentration factor (BF) of Cd by 39-71%. Comparative transcriptomic analysis demonstrated that the differently expressed genes (DEGs) were mainly encoding functions involved in "transmembrane transport", "ion transport", "oxidation reduction process", "oxidative phosphorylation", "carbon metabolism", "glycolysis/gluconeogenesis", "photosynthesis", and "biosynthesis of amino acids." These results indicate that C. geophilum is able to mitigate toxic metals stress by promoting nutrient uptake, photosynthesis, and plant growth, thereby modulating the antioxidant system to reduce oxidative stress and reducing the transport and enrichment of toxic metals from the root to the shoot of Massion's pine seedlings.

Comprehensive Evaluation of the Efficient and Safe Utilization of Two Varieties of Winter Rapeseed Grown on Cadmium- and Lead-Contaminated Farmland under Atmospheric Deposition

To determine the feasibility of planting rapeseed to safely utilize heavy metals (HMs)-contaminated farmlands surrounding working smelters under atmospheric deposition, a field trial was conducted to analyze the yields, cadmium (Cd) and lead (Pb) concentrations, health risks, and economic benefits of 15 rapeseed cultivars (13 Brassica napus L. and two Brassica campestris L.) in Jiyuan City, Henan Province, China. The results show that the seeds’ Cd concentration was 0.12–0.64 mg·kg−1 and the seeds’ Pb concentration was higher than Cd at 0.49–1.22 mg·kg−1. The Cd bioconcentration factor of B. campestris (0.702–0.822) was higher than that of B. napus (0.246–0.502). Additionally, Cd and Pb transfer factors from the stems to the pods and seeds were 0.34–1.20 and 0.54–4.53, respectively. Combined with a comprehensive analysis of the annual deposition data of Cd and Pb, 16.40 and 345.79 kg·hm−2, respectively, HMs in the seeds were not only derived from those in the soil, but were also derived from the atmosphere. Furthermore, the Cd and Pb levels in rapeseed oil, meal, and straw met the requirements stipulated in the standards for food safety, feeds hygiene, and organic fertilizer in China. Rapeseed–maize rotation yielded a profit of 15,550 CNY·a−1·hm−2, thereby increasing the economic output by 133.8%. A cluster analysis revealed that B. campestris SYH and ZS100 and B. napus ZY-821 showed the greatest comprehensive benefits. In conclusion, rapeseed cultivation is a viable and extendable approach that can achieve the safe utilization of typical HMs-contaminated farmland caused by atmospheric deposition in Northern China.

Assessment of sludge application in maize (Zea mays L.): influence on crop biomass and heavy metals bioavailability

ABSTRACT Increasing population and subsequent increase in waste necessitate recycling of waste products to minimize the environmental burden. This study was conducted in semi-arid tropics of Punjab to evaluate different rates of sludge application as a supplementary source of nutrients to conventional fertilizers in maize. The grain yield was significantly higher with the application of 5 t ha−1 sludge over control and marginally lower than in 10 t ha−1. Cadmium (Cd), chromium (Cr), lead (Pb), and nickel (Ni) in grains were below international standards even after maximum dose of sludge treatment and can be declared as safe for consumption. The bioconcentration factor of Cd and Ni increased by 82% and 49% with 10 t ha−1 over control, respectively while it remained same for Cr and Pb. Significant increase in exchangeable Cd, Pb in carbonate, and easily reducible oxide, Ni and Cr in residual fraction with 10 t ha−1 sludge over control were found. Mobility of only Pb and Cd increased with increasing sludge treatment. Conclusively, sludge application can be beneficial in increasing plant biomass, however heavy metal accumulation in plants may limit its use. Long-term effect of sludge applications as nutrient sources must be evaluated to get more in-depth insights.

NaCl-mediated strategies for the trade-off between Cd bioconcentration and translocation in Solanum nigrum L

Salt interference significantly affects the behavior of heavy metals in the environment. This study compared and analyzed the response process, migration, and transformation of cadmium (Cd) in the hyperaccumulator Solanum nigrum (S. nigrum) under different NaCl levels to reveal the interference mechanisms of salt in plant remediation of Cd-contaminated soil. The results showed that Cd and salt stress significantly inhibited the growth of plants. The stress effect had more potent growth inhibition at the root than aboveground, thus inducing changes in the spatial configuration of the plants (decreased root-to-aboveground biomass ratio). Salt could activate Cd in plants, enhancing the inhibitory effect on plant growth. Salt increased Cd bioavailability due to the rhizosphere acidification effect, increasing plants’ Cd accumulation. The Cd bioconcentration factor in plant roots peaked during the high Cd-high salt treatment (117.10), but the Cd accumulation of plants peaked during the high Cd-low salt treatment (233.04 μg plant−1). Salt additions and increased Cd concentrations enhanced root compartmentalization, inhibiting Cd transport to the aboveground. Changes in Fourier-transform infrared spectroscopy (FTIR) measurements confirmed that the functional groups in plants provided binding sites for Cd. These findings can help guide the phytoremediation of Cd contamination under saline soil conditions.

Exogenous plant growth regulator and foliar fertilizers for phytoextraction of cadmium with Boehmeria nivea [L.] Gaudich from contaminated field soil

As a enrichment plant, ramie can be used for the phytoremediation of cadmium (Cd)-contaminated soil. However, it is worth exploring the role of plant growth regulators and foliar fertilizers in the process of plant growth and development and Cd adsorption. By measuring the agronomic traits, Cd content of aboveground and underground ramie, calculating the Cd transfer coefficient (TF) and Cd bioconcentration factors (BCF), and the correlation between various indicators. This study examined the effects of plant growth regulators and foliar fertilizers on ramie’s capacity for Cd accumulation and transportation. Plant growth regulators and foliar fertilizers increased the Cd content of the aboveground ramie, reduced the Cd content of the underground ramie, and increased the TF. Among them, GA-1 increased the Cd content of the aboveground ramie to 3 times more than that of the control and reduced the Cd content of the underground ramie by 54.76%. Salicylic acid (SA) increased the Cd content of the aboveground ramie to three times more than that of the control. The combination of GA and foliar fertilizer reduced the Cd content of the aboveground and underground ramie and the TF and BCF of the underground ramie. After the hormones were sprayed, the TF of ramie had a significant positive correlation with the Cd content of the aboveground ramie; the BCF of the aboveground ramie had a significant positive correlation with the Cd content and TF of the aboveground ramie. The results indicate that Brassinolide (BR), gibberellin (GA), ethephon (ETH), polyamines (PAs), and salicylic acid (SA) have different effects on the enrichment and transport of Cd in ramie. This study provided an effective method to improve the capacity for ramie to adsorb heavy metals during cultivation.

Spatial Distribution, Migration, and Ecological Risk of Cd in Sediments and Soils Surrounding Sulfide Mines—A Case Study of the Dabaoshan Mine of Guangdong, China

Acid mine drainage (AMD) resulting from metal sulfide mining activities can lead to contamination by potentially toxic elements (PTEs) primarily concentrated around the mining area and gradually spreading outward. However, ecological risks do not correspond directly to PTE concentrations, making it challenging to effectively manage the mining environment and accurately prevent potential ecological impacts. In this paper, we analyzed Cd levels in sediments, soils, and corresponding rice grains sampled from four villages near Dabaoshan Mine of Guangdong, China, in 2017. Our results reveal that Cd is the most prominent pollutant element, exhibiting significant enrichment and spatial heterogeneity in both soil and sediments and higher accumulation levels in rice grains compared to other PTEs. Cd concentrations in soil decrease from the tailings pond to the river terrace, with a slight increase after Taiping River joins and flows into the alluvial plain. However, the concentrations in sediments show the opposite trend. The bioconcentration factor (BCF) for Cd in agricultural soil from the river terrace is lower than that from the alluvial plain and the degree of exceeding the maximum permit level (MPL) of Cd in rice grains increases along the river. Mineral transformation and topography are important factors in controlling the geochemical behavior of PTEs. Remediation efforts alter the physicochemical properties of the river, resulting in the release of PTEs during schwertmannite transformation followed by their adsorption by clay minerals. Furthermore, the random forest (RF) analysis highlights that the bioavailability and potential ecological risk of Cd in soils are governed by the occurrence form of Cd in different topographies, mainly controlled by TFe2O3, Mn, and CaO in the river terrace and CaO, Al2O3/SiO2, and Mn in the alluvial plain. Therefore, considering the impact of topography on mineral compositions, physicochemical properties, and occurrence form of PTEs in soil and sediments is essential for assessing ecological risk in mining areas.

Combined effects of microplastics and cadmium on the soil-plant system: Phytotoxicity, Cd accumulation and microbial activity

Microplastics (MPs), an emerging pollutant of concern, widely cooccurred with heavy metals in soil, however, little is known about the combined effects of the interactions of MPs and cadmium (Cd) on the soil-plant system. In this study, the combined effects of several types of MPs and soil Cd contamination on Brassica juncea growth, Cd uptake, and soil microbial carbon metabolism were investigated in a 50-day pot experiment. Aged polyethylene (PE), aged polypropylene (PP), biodegradable polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) displayed moderate phytotoxicity, with reductions in leaf chlorophyll content and shoot biomass. Compared with the control treatment without MPs or B. juncea, B. juncea growth significantly increased the soil pH by 0.3 pH units, and the growth of B. juncea in the presence of biodegradable PBAT or PLA MPs increased the soil pH by an additional 0.4 or 0.6 pH units, respectively. The presence of PBAT or PLA MPs greatly reduced soil diethylenetriamine pentaacetic acid (DTPA)-extractable Cd concentrations and plant Cd accumulation. The Cd bioconcentration factor was higher in roots than shoots in all treatments except the treatment containing PBAT MPs. The average well color development (AWCD), an indicator of metabolic activity, was highest in the treatment with B. juncea alone and was reduced by both biodegradable and conventional MPs. The microbial utilization efficiency of esters and alcohols was enhanced in the treatment with PBAT MPs, whereas carboxylic acids were preferentially utilized in the treatment with PLA MPs. These findings indicate that co-exposure to MPs and Cd may alter soil microenvironmental characteristics such as soil pH, leading to changes in Cd bioavailability, plant growth and Cd accumulation, and the microbial community's capacity to metabolize carbon. These effects of MPs in soil warrant further exploration.