Cd Pollution Research Articles

Optimal biochar selection for cadmium pollution remediation in Chinese agricultural soils via optimized machine learning

Biochar is effective in mitigating heavy metal pollution, and cadmium (Cd) is the primary pollutant in agricultural fields. However, traditional trial-and-error methods for determining the optimal biochar remediation efficiency are time-consuming and inefficient because of the varied soil, biochar, and Cd pollution conditions. This study employed the machine learning method to predict the Cd immobilization efficiency of biochar in soil. The predictive accuracy of the random forest (RF) model was superior to that of the other common linear and nonlinear models. Furthermore, to improve the reliability and accuracy of the RF model, it was optimized by employing a root-mean-squared-error-based trial-and-error approach. With the aid of the optimized model, the empirical categories for soil Cd immobilization efficiency were biochar properties (60.96 %) > experimental conditions (19.6 %) ≈ soil properties (19.44 %). Finally, this study identified the optimal biochar properties for enhancing agricultural soil Cd remediation in different regions of China, which was beneficial for decision-making regarding nationwide agricultural soil remediation using biochar. The immobilization effect of alkaline biochar was pronounced in acidic soils with relatively high organic matter. This study provides insights into the immobilization mechanism and an approach for biochar selection for Cd immobilization in agricultural soil.

Root cell wall polysaccharides and endodermal barriers restrict long-distance Cd translocation in the roots of Kentucky bluegrass

Soil Cd pollution is a significant environmental issue faced by contemporary society. Kentucky bluegrass is considered a potential phytoremediation species, as some varieties have excellent cadmium (Cd) tolerance. However, the mechanisms of Cd accumulation and transportation in Kentucky bluegrass are still not fully understood. The Cd-tolerant Kentucky bluegrass cultivar ‘Midnight’ (M) exhibits lower Cd translocation efficiency and a higher leaf Cd concentration compared to the Cd-sensitive cultivar ‘Rugby II’ (R). We hypothesized that Cd translocation from roots to shoots in cultivar M is hindered by the endodermal barriers and cell wall polysaccharides; hence, we conducted Cd distribution, cytological observation, cell wall component, and transcriptomic analyses under Cd stress conditions using the M and R cultivars. Cd stress resulted in the thickening of the endodermis and increased synthesis of cell wall polysaccharides in both the M and R cultivars. Endodermis development restricted the radical transport of Cd from the root cortex to the stele, while the accumulation of cell wall polysaccharides promoted the binding of Cd to the cell wall. These changes further inhibited the long-distance translocation of Cd from the roots to the aerial parts. Furthermore, the M cultivar exhibited limited long-distance Cd translocation efficiency compared to the R cultivar, which was attributed to the enhanced development of endodermal barriers and increased Cd binding by cell wall polysaccharides. This study provides valuable insights for screening high Cd transport efficiency in Kentucky bluegrass based on anatomical structure and genetic modification.

Effect of exogenous γ-aminobutyric acid on physiological property, antioxidant activity, and cadmium uptake of quinoa seedlings under cadmium stress.

Increasing cadmium (Cd) pollution has negative effects on quinoa growth and production. Gamma-aminobutyric acid (GABA) confers plants with stress resistance to heavy metals; however, the mechanism remains unclear. We explored the effects of exogenous GABA on the physiological characteristics, antioxidant capacity, and Cd accumulation of quinoa seedlings under Cd stress using hydroponic experiments. Partial least-squares regression was used to identify key physical and chemical indices of seedlings affecting Cd accumulation. Compared with those of the CK group, exposure to 10 and 25 µmol·L-1 Cd significantly reduced the photosynthetic pigment contents, photosynthesis, and biomass accumulation of quinoa seedlings; resulted in shorter and thicker roots; decreased the length of the lateral roots; decreased the activities of superoxide dismutase (SOD) and peroxide (POD); and increased H2O2 and malondialdehyde (MDA) contents. Exogenous GABA reduced the Cd content in the stem/leaves and roots of quinoa seedlings under Cd stress by 13.22-21.63% and 7.92-28.32%, decreased Cd accumulation by 5.37-6.71% and 1.91-4.09%, decreased the H2O2 content by 38.21-47.46% and 45.81-55.73%, and decreased the MDA content by 37.65-48.12% and 29.87-32.51%, respectively. GABA addition increased the SOD and POD activities in the roots by 2.78-5.61% and 13.81-18.33%, respectively, under Cd stress. Thus, exogenous GABA can reduce the content and accumulation of Cd in quinoa seedlings by improving the photosynthetic characteristics and antioxidant enzyme activity and reducing the degree of lipid peroxidation in the cell membrane to alleviate the toxic effect of Cd stress on seedling growth.

Level of heavy metals and environmental pollution index in Ahvaz, Southwest Iran

This study was designed to evaluate the concentration of heavy metals (HMs) in the north of Ahvaz, southwest Iran. The soil samples were collected from the agricultural farm and riverside in Karun, for the investigation of the environmental impacts of the selected HMs in the soil of the Weiss and Arab Assad regions. For soil sampling in a period, nine farms were selected from each region, and 10 samples were taken from each agricultural farm. Zoning was done using GIS. The highest of Contamination Factor, Enrichment factor and geo-accumulation index of HMs for Cd (7.84, 73.92 and 2.38), and the lowest value of this index for Cr (0.21, 1.98 and − 2.82), respectively. Furthermore of the farm soil showed that the most toxic effect is related to Cd. The HMs contamination indices of the soil samples showed that the studied HMs had contaminated the agricultural fields. Moreover, the zoning maps of the Co, Cu, Pb and Cr showed that they had not contaminated the soil of wheat fields, but Cd and Zn revealed high contamination levels. The zoning of Ni concentration distribution showed that this metal contamination came from both anthropogenic aspects and geological activities in the region. According to our findings, the EF illustrated high levels of pollution for Cd, Cu, Cr, Pb, Ni, Fe, Mn, Co, and Zn, which seems to be in accordance with the accumulation of agricultural fertilizers (phosphate and nitrate), industrial and human activities in the region.

Prevalence of Cadmium and Lead Residues in Fried Meat (Suya) Sold in Kaduna Metropolis, Kaduna State, Nigeria

Study’s Novelty/Excerpt This study is novel as it provides the first comprehensive analysis of cadmium (Cd) and lead (Pb) contamination in various types of suya meat in Kaduna, Nigeria, using Atomic Absorption Spectrophotometry. Unlike previous research, this study uniquely examines multiple animal sources and local government areas, offering a detailed comparison of contamination levels across species and regions. Additionally, the findings highlight the widespread public health risk due to Cd and Pb levels exceeding international safety standards, emphasizing the urgent need for regulatory measures to mitigate environmental pollution and protect public health. Full Abstract Heavy metals are of public health concern worldwide due to their damaging effects on human and animal health. The study was aimed at analyzing the presence of cadmium (Cd) and lead (Pb) residues in suya meats; cattle meat (beef), sheep meat (mutton), goat meat (chevon), fowl meat (chicken) and dog meat sold in the Kaduna metropolis, Kaduna State. A descriptive-quantitative research design was used, with fifty samples collected from four Local Government Areas (Chikun, Igabi, Kaduna North and Kaduna South). Atomic Absorption Spectrophotometery was used to analyze and quantify the presence of these heavy metals. Microsoft Excel (Version 2019) and one-way ANOVA are the statistical tools used for result analysis and Cd and Pb were found to be present in all the suya samples analyzed. The results showed statistical significance (p<0.05) between the overall mean concentration of Cd (0.049 mg/kg) and Pb (0.44 mg/kg) in the samples. Even though the mean concentration of Cd in suya samples varied with regards to which the animal originates viz: cattle (0.033 mg/kg), sheep (0.058 mg/kg), goat (0.048 mg/kg), dog (0.04 mg/kg) and chicken (0.078 mg/kg); likewise that of Pb: cattle (0.47 mg/kg), sheep (0.41 mg/kg), goat (0.41 mg/kg), dog (0.39 mg/kg) and chicken (0.51 mg/kg); the animal species from which the meat used in making the suya had no statistically significant influence on the heavy metal content of the meat (p˃0.05). The mean concentration of Cd and Pb obtained within the study areas, in mg/kg were: Chikun (0.046 and 0.43), Igabi (0.044 and 0.43), Kaduna North (0.054 mg/kg) and (0.49 mg/kg), Kaduna South (0.053 mg/kg) and (0.41 mg/kg) respectively. The mean concentration of cadmium and lead in the suya samples was above the permissible limits set by EC and FAO limits of 0.01ug/g lead and 0.003ug/g for cadmium (FAO, 1983), indicating the general contamination of suya meats by heavy metals. The study recommends public measures to minimize environmental pollution and bioaccumulation of Cd and Pb to prevent related ailments and mortality; enforcing regulations governing industrial activities and waste disposal to protect the public from heavy metals pollution.

A novel and recyclable silica gel-modified biochar to remove cadmium from wastewater: Model application and mechanism exploration

Water pollution caused by heavy metals is a major environmental problem, threatening water production, food safety, and human health. Cadmium (Cd) pollution is particularly serious because of food-chain biomagnification at toxic concentrations. Modified biochar is promising for heavy metal removal; however, efficient adsorbents for Cd removal are lacking. In the present study, a novel adsorbent, silica gel-modified biochar (SGB), was prepared and applied to treat sewage polluted by Cd. Through the batch adsorption experiments, it is known that SGB possessed outstanding Cd removal ability and recycleability. Furthermore, the adsorption behavior and mechanisms were analyzed by the application of kinetic and isotherm models. The maximum Cd2+ adsorption capacity of SGB was 38.08 mg g−1, and after five recycling processes, the Cd2+ removal rate was still 86.89 %. When the pH of the solution was 7.0, SGB showed the strongest Cd2+ adsorption capacity (29.06 mg g−1). When competitive ions existed, biochar also had high Cd removal efficiency, although the effect of Pb2+ was greater than those of Cu2+ and Zn2+, indicating that SGB was applicable to complex polluted water. Additionally, the main Cd2+ adsorption mechanisms by SGB were electrostatic interactions, π-π interactions, complexation, and co-precipitation. These results showed that SGB can effectively treat Cd-contaminated wastewater as a new adsorbent.

A meta-analysis and experimental survey of heavy metals pollution in agricultural soils

Heavy metal (HM) pollution in agricultural soils represents a hidden danger to food security worldwide. In this paper, the spatio-temporal trends of heavy metals from eight countries and 50 soil samples from agricultural farmland were evaluated through a combination of field surveys and meta-analysis to provide a comprehensive report on heavy metal pollution. The soil samples were analysed using inductively coupled plasma–mass spectrometry (ICP-MS) (Perkin Elmer Nixon 300Q). The contamination factor (CF) and pollution load index (PLI), and diagnostic tests on the extracted data were calculated. The results of the CF in the soils indicate extreme contamination for Cr, suggesting ecotoxicological effects, while the PLI values range from baseline to moderate pollution for Cd, Hg, Cu, Zn, and Ni, except for Cr, which shows very high pollution, suggesting that the soils have undergone some form of deterioration. The meta-analysis results of the 50 reviewed articles published between 2010 and 2023 showed increasing trends for all the HMs. The weighted mean values of Cd, Cr, Hg, Cu, Zn, As, and Ni were in the range of 0.0-222.7, 0.08-289.2, 0.03-193, 2.94-198.1, 0.0-771.1, 0.0-231, and 1.71-99.75.6 mg/kg, respectively. The mean values of Cd, Hg, Zn and As exceeded two to three times the values of China National Environmental Monitoring Centre (CNEMC) European Union's most cited guideline (MEF), and the rock crust guideline. The results of the correlation matrix heatmap revealed a highly positive correlation between Cr and Ni (R2 = 0.66), suggesting that these elements have the same source and are likely prevalent in agricultural soils. The spatial origin of the publications reveals that 82% of the studies were from China followed by South Africa and Italy accounting for 4% respectively while Nigeria, Egypt, Morocco, Iran, and Turkey account for 2% each. The findings of this study have important implications for environmental regulation on agricultural food protection from heavy metal pollution. Unlike previous meta-analysis studies which often adopt a “silos” method, this study highlights a nexus approach that integrates both meta-analysis and experimental studies which could establish a more comprehensive understanding of heavy metal pollution in agricultural soils.

Assessment of probable health risk of potentially toxic metals in irrigable wetland soils from Ogun and Lagos States, Southwestern Nigeria

ObjectiveThe present study aimed at investigating the probable health risk associated with potentially toxic metals (PTMs) in irrigable wetland soils from Ogun and Lagos states, Southwestern Nigeria. MethodologyA total of 36 composite soil samples were collected from twelve monitoring sites and analyzed for potentially toxic metals [cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), and zinc (Zn)] using atomic absorption spectrophotometry. PTM data underwent inferential and descriptive statistical analysis using IBM SPSS. Health risk indices were assessed for hazard quotient (HQ), hazard index (HI), and cancer risk (CR) using the standard method. Ecological and pollution risks were also assessed. ResultsFe (1465±977 to 47,785±12,049 mg kg−1) was the most abundant metal observed in irrigable wetland soils. The distribution pattern of PTMs in irrigable wetland soils followed the decreasing order of Fe > Zn > Cu > Cr > Pb > Ni > Co > Cd. The pollution index risk indicated values greater than 1.0 for Cd (2.43–133), Zn (1.60–6.32), Cu (1.49–5.89), and Pb (1.15–2.94). Cadmium indicated a considerable ecological risk index (4002), a moderate-to-high pollution level according to the Nemerov integrated pollution index (12.33), and a very high enrichment factor (14.1–227). The HQs of PTMs were generally less than 1.0 for adults, while a HI greater than 1.0 was observed for children. The CRs exceeding the threshold limit of 1.0 × 10−4 were observed for Co, Cd, Cr, and Ni [at one or more sampling sites] in the wetland soils exposed to by adults and children. ConclusionIn this study, the irrigated wetland soils showed high ecological, pollution, and carcinogenic risks of Cd, particularly at the Odo Aro monitoring site. The findings from the study could offer a theoretical basis and data support for pollution monitoring, assessment, and control in the study area.

Investigating the Mechanism of Cadmium-Tolerant Bacterium Cellulosimicrobium and Ryegrass Combined Remediation of Cadmium-Contaminated Soil.

Cadmium (Cd) pollution has been rapidly increasing due to the global rise in industries. Cd not only harms the ecological environment but also endangers human health through the food chain and drinking water. Therefore, the remediation of Cd-polluted soil is an imminent issue. In this work, ryegrass and a strain of Cd-tolerant bacterium were used to investigate the impact of inoculated bacteria on the physiology and biochemistry of ryegrass and the Cd enrichment of ryegrass in soil contaminated with different concentrations of Cd (4 and 20 mg/kg). The results showed that chlorophyll content increased by 24.7% and 41.0%, while peroxidase activity decreased by 56.7% and 3.9%. In addition, ascorbic acid content increased by 16.7% and 6.3%, whereas glutathione content decreased by 54.2% and 6.9%. The total Cd concentration in ryegrass increased by 21.5% and 10.3%, and the soil's residual Cd decreased by 86.0% and 44.1%. Thus, the inoculation of Cd-tolerant bacteria can improve the antioxidant stress ability of ryegrass in Cd-contaminated soil and change the soil's Cd form. As a result, the Cd enrichment in under-ground and above-ground parts of ryegrass, as well as the biomass of ryegrass, is increased, and the ability of ryegrass to remediate Cd-contaminated soil is significantly improved.

Preparation of porous biochar from fusarium wilt-infected banana straw for remediation of cadmium pollution in water bodies

The problem of cadmium pollution and its control is becoming increasingly severe issue in the world. Banana straw is an abundant bio raw material, but its burning or discarding in field not only causes pollution but also spreads fusarium wilt. The objective of this paper is to utilize biochar derived from the wilt-infected banana straw for remediation of Cd(II) pollution while to eliminate the pathogen. The activity of wilt pathogen in biochar was determined by PDA petri dish test. The Cd(II) adsorption of the biochar was determined by batch adsorption experiments. The effects of KOH concentration (0.25, 0.5 and 0.75 M) on the physicochemical characteristics of the biochar were also observed by BET, SEM, FTIR, XRD and XPS. Results showed that pristine banana straw biochar (PBBC) did not harbor any pathogen. The specific surface area (SSA) and Cd(II) adsorption capacity of 0.75 M KOH modified banana straw biochar (MBBC0.75M) were increased by 247.2% and 46.1% compared to that of PBBC, respectively. Cd(II) adsorption by MBBC0.75M was suitable to be described by the pseudo-second-order kinetic model and Freundlich isotherm. After Cd(II) adsorption, the CdCO3 were confirmed by XRD and observed through SEM. The weakness and shift of oxygen-containing functional groups in MBBC0.75M after Cd(II) adsorption implied that those groups were complexed with Cd(II). The results showed that pyrolysis could not only eliminate banana fusarium wilt, but also prepare porous biochar with the wilt-infected banana straw. The porous biochar possessed the potential to adsorb Cd(II) pollutants.

Combined effects of cadmium and simulated acid rain on soil microbial communities in the early cultivation of Populus beijingensis seedlings

The combined cadmium (Cd) and acid rain pollution poses a significant threat to the global ecological environment. Previous studies on the combined adverse effects have predominantly focused on the aboveground plant physiological responses, with limited reports on the microbial response in the rhizosphere soil. This study employed Populus beijingensis seedlings and potting experiments to simulate the impacts of combined mild acid rain (pH=4.5, MA) or highly strong acid rain (pH=3.0, HA), and soil Cd pollution on the composition and diversity of microbial communities, as well as the physiochemical properties in the rhizosphere soil. The results showed that Cd decreased the content of inorganic nitrogen, resulting in an overall decrease of 49.10 % and 46.67 % in ammonium nitrogen and nitrate nitrogen, respectively. Conversely, acid rain was found to elevate the content of total potassium and soil organic carbon by 4.68 %-6.18 % and 8.64–19.16 %, respectively. Additionally, simulated acid rain was observed to decrease the pH level by 0.29–0.35, while Cd increased the pH level by 0.11. Moreover, Cd alone reduced the rhizosphere bacterial diversity, however, when combined with acid rain, regardless of its intensity, Cd was observed to increase the diversity. Fungal diversity was not influenced by the acid rain, but Cd increased fungal diversity to some extend under HA as observed in bacterial diversity. In addition, composition of the rhizosphere bacterial community was primarily influenced by the inorganic nitrogen components, while the fungal community was driven mainly by soil pH. Furthermore, “Metabolism” was emerged as the most significant bacterial function, which was markedly affected by the combined pollution, while Cd pollution led to a shift from symbiotroph to other trophic types for fungi. These findings suggest that simulated acid rain has a mitigating effect on the diversity of rhizosphere bacteria affected by Cd pollution, and also alters the trophic type of these microorganisms. This can be attributed to the acid rain-induced direct acidic environment, as well as the indirect changes in the availability or sources of carbon, nitrogen, or potassium.

Transcription factors involved in plant responses to cadmium-induced oxidative stress

Cadmium (Cd) is a heavy metal highly toxic to living organisms. Cd pollution of soils has become a serious problem worldwide, posing a severe threat to crop production and human health. When plants are poisoned by Cd, their growth and development are inhibited, chloroplasts are severely damaged, and respiration and photosynthesis are negatively affected. Therefore, elucidating the molecular mechanisms that underlie Cd tolerance in plants is important. Transcription factors can bind to specific plant cis-acting genes. Transcription factors are frequently reported to be involved in various signaling pathways involved in plant growth and development. Their role in the resistance to environmental stress factors, particularly Cd, should not be underestimated. The roles of several transcription factor families in the regulation of plant resistance to Cd stress have been widely demonstrated. In this review, we summarize the mechanisms of five major transcription factor families–WRKY, ERF, MYB, bHLH, and bZIP–in plant resistance to Cd stress to provide useful information for using molecular techniques to solve Cd pollution problems in the future.

Potential toxic elements (PTEs) in rhizosphere soils and crops under a black shale high geological background: Pollution characteristics, distribution and risk assessment

The LouShao Basin in Hunan Province is covered with two sets of black rock series containing various potential toxic heavy metal elements. The rock series are rich in various potential toxic heavy metal elements, and the weathered black shale is the main formation of local farmland soil, making it a typical area with high geological background in China. The purpose of this study is to assess the regional ecological and health risks by studying the correlation between the content of heavy metal elements enriched in rhizosphere soil, non-rhizosphere soil, and crops, and the concentration of heavy metal elements in the main source, black shale rocks. The results show that the elements in the black shale far exceed the world average of rock, severely affecting soil element concentrations. Se element is the most severely polluted in rhizosphere soil, exceeding the background value by 7 times. The concentration of heavy metals between rock-non-rhizosphere soil-rhizosphere soil-crops decreases linearly. The distribution of pollution has strong spatial autocorrelation, and the high geological background is the main reason. Pollution index results show significant pollution of Se, Cr, Hg, and Cd in crops, with the pollution of heavy metal element Cr in corn being extremely serious with Igeo = 6.71. The ecological risk order is Se > Cd > Cr > As > Pb > Hg. Humans mainly contact elements through skin contact and food chain intake. The HI value of heavy metal element Cd is greater than 1, indicating a high carcinogenic risk. Human exposure to Cd through skin contact and food chain intake may lead to related diseases such as kidney stones, and pose greater harm to children.

Remediation of heavy metal cadmium polluted water by a variety of garden plant schemes

With the advancement of urbanization and industrialization in China, more and more urban and rural areas are experiencing varying degrees of cadmium (Cd) pollution in water and soil. Biological treatment is one way to eliminate Cd pollution in water bodies, and plants such as Loropetalum chinense var. rubrum, Triarrhena lutarioriparia L. Liu var. lutarioriparia, and Phalaris arundinacea var. picta can purify heavy metal pollution. So this study attempts to select six common garden plants and conduct experiments to analyze the absorption effect on Cd in this polluted water body. The aim is to find a planting plan for garden plants that has a stronger purification effect on Cd polluted water bodies. The experimental results showed that in a water environment with a Cd concentration of 50 mg/L, the enrichment coefficients of Cd in the roots of Polygonum chinense L., Gardenia jasminoides Ellis, Loropetalum chinense var. rubrum, Triarrhena lutarioriparia L. Liu var. lutarioriparia, Phalaris arundinacea var. picta, and Euonymus japonicus Thunb. were 0.735, 0.938, 0.784, 0.827, 3.168, and 0.597, respectively. In a water environment with a Cd concentration of 10 mg/L, the enrichment coefficients of Cd in the roots of Polygonum chinense L., Gardenia jasminoides Ellis, Loropetalum chinense var. rubrum, Triarrhena lutarioriparia L. Liu var. lutarioriparia, Phalaris arundinacea var. picta, and Euonymus japonicus Thunb. were 1.549, 0.729, 1.081, 0.924, 1.420, and 0.690, respectively. In a water environment with a Cd concentration of 5 mg/L, the enrichment coefficients of Cd in the roots of Polygonum chinense L., Gardenia jasminoides Ellis, Loropetalum chinense var. rubrum, Triarrhena lutarioriparia L. Liu var. lutarioriparia, Phalaris arundinacea var. picta, and Euonymus japonicus Thunb. were 1.238, 0.473, 0.566, 0.695, 0.431, and 1.236, respectively. In a water environment with a Cd concentration of 0 mg/L, the enrichment coefficients of Cd in the roots of Polygonum chinense L., Gardenia jasminoides Ellis, Loropetalum chinense var. rubrum, Triarrhena lutarioriparia L. Liu var. lutarioriparia, Phalaris arundinacea var. picta, and Euonymus japonicus Thunb. were 1.030, 0.452, 0.954, 0.695, 0.826, and 0.958, respectively. Due to the significant decrease of Cd in the roots and significant increase of Cd in the stems and leaves of Polygonum chinense L. in the water with a Cd of 50 mg/L, the cultivation time increased from 10d to 30d. The plant species Polygonum chinense L. exhibited a notably high Cd enrichment potential, as evidenced by its substantial enrichment and transport coefficients. In the experiments, the plant's ability to accumulate and transport Cd was demonstrated quantitatively. Under controlled conditions, the highest Cd enrichment coefficients in root, stem, and leaf were 0.735, 2.900, and 1.581, respectively. These results indicated the plant's capacity for efficient Cd uptake and translocation, making it a promising candidate for phytoremediation efforts in Cd-contaminated environments. However, in the high Cd environment, the root enrichment coefficient of Phalaris arundinacea var. picta was the highest, making it more suitable as a container for collecting Cd ions in Cd contaminated water. Under other concentration conditions, the average Cd enrichment coefficient of various parts of Polygonum chinense L was still the highest. The experimental results prove that Polygonum chinense L. has the ability to treat Cd polluted water bodies through absorption.

Toxic effects and mechanisms of chronic cadmium exposure on Litopenaeus vannamei growth performance based on combined microbiome and metabolome analysis

Cadmium (Cd) pollution seriously affects marine organisms' health and poses a threat to food safety. Although Cd pollution has attracted widespread attention in aquaculture, little is known about the toxic mechanisms of chronic Cd exposure on shrimp growth performance. The study investigated the combined effects of chronic exposure to Cd of different concentrations including 0, 75, 150, and 300 μg/L for 30 days on the growth performance, tissue bioaccumulation, intestinal microbiology, and metabolic responses of Litopenaeus vannamei. The results revealed that the growth was significantly inhibited under exposure to 150 and 300 μg/L Cd2+. The bioaccumulation in gills and intestines respectively showed an increasing and inverted "U" shaped trend with increasing Cd2+ concentration. Chronic Cd altered the intestinal microflora with a significant decrease in microbial richness and increasing trends in the abundances of the potentially pathogenic bacteria Vibrio and Maribacter at exposure to 75 and 150 μg/L Cd2+, and Maribacter at 300 μg/L. In addition, chronic Cd interfered with intestinal metabolic processes. The expressions of certain metabolites associated with growth promotion and enhanced antioxidant power, including N-methyl-D-aspartic acid, L-malic acid, guanidoacetic acid, betaine, and gluconic acid were significantly down-regulated, especially at exposure to 150 and 300 μg/L Cd2+, and were negatively correlated with Vibrio and Maribacter abundance levels. In summary, chronic Cd exposure resulted in severe growth inhibition and increased Cd accumulation in shrimp tissues. Increased levels of intestinal pathogenic bacteria and decreased levels of growth-promoting metabolites may be the key causes of growth inhibition. Harmful bacteria Vibrio and Maribacter may be associated with the inhibition of growth-promoting metabolite expression and may be involved in disrupting intestinal metabolic functions, ultimately impairing shrimp growth potential. This study sheds light on the potential toxicological mechanisms of chronic Cd inhibition on shrimp growth performance, offering new insights into Cd toxicity studies in aquaculture.

Natural colonizers effectively restore heavy metal polluted wasteland

In India, ∼30% of total land is degraded due to pollution, salinization, and nutrient loss. Change in soil-quality at urban waste-dumping site prior and after cow-dung amendment was compared with control agriculture soil. The soil at waste-dumping site had elevated pH, EC, temperature and lowered OC and NPK concentrations when compared to control. Polymetallic pollution of Cr, Cd, Pb, and Ni beyond permissible limits was obtained. Cow-dung amendment restored soil physicochemical properties at the waste-dumping site, with increasing soil moisture, CEC and OC; however, a slight change in soil bulk-density and heavy-metal concentration post-amendment was noted. The seven natural colonizers present at the waste-dumping site accumulated more metals in roots than shoots. Datura innoxia had maximum bioaccumulation of Cr, Calotropis procera of Cd and Ni and Parthenium hysterophorus of Pb in roots. All these plants had Bioacccumulation factor (BAfroot )>1 and translocation factor (Tf) <1 for Cd and serve as its phytostabilizer except Calotropis procera which had BAfroot >1 and Tf >1 and is identified as a phytoextractor for Cd. Cow-dung amendment alone appeared to be insufficient and additionally the revegetation of natural colonizers is recommended for effective reduction in heavy metal load and improving overall soil health at wasteland. Such eco-restoration may also minimize risks to biodiversity in India.

Study on Adsorption of Cd in Solution and Soil by Modified Biochar-Calcium Alginate Hydrogel.

Contamination with cadmium (Cd) is a prominent issue in agricultural non-point source pollution in China. With the deposition and activation of numerous Cd metal elements in farmland, the problem of excessive pollution of agricultural produce can no longer be disregarded. Considering the issue of Cd pollution in farmland, this study proposes the utilization of cross-linked modified biochar (prepared from pine wood) and calcium alginate hydrogels to fabricate a composite material which is called MB-CA for short. The aim is to investigate the adsorption and passivation mechanism of soil Cd by this innovative composite. The MB-CA exhibits a higher heavy metal adsorption capacity compared to traditional biochar and hydrogel due to its increased oxygen-containing functional groups and heavy metal adsorption sites. In the Cd solution adsorption experiment, the highest Cd2+ removal rate reached 85.48%. In addition, it was found that the material also has an excellent pH improvement effect. Through the adsorption kinetics experiment and the soil culture experiments, it was determined that MB-CA adheres to the quasi-second-order kinetic model and is capable of adsorbing 35.94% of Cd2+ in soil. This study validates the efficacy of MB-CA in the adsorption and passivation of Cd in soil, offering a novel approach for managing Cd-contaminated cultivated land.

Elevated temperature as a dominant driver to aggravate cadmium toxicity: Investigations through toxicokinetics and omics

Despite the great interest in the consequences of global change stressors on marine organisms, their interactive effects on cadmium (Cd) bioaccumulation/biotoxicity are very poorly explored, particularly in combination with the toxicokinetic model and molecular mechanism. According to the projections for 2100, this study investigated the impact of elevated pCO2 and increased temperature (isolated or joint) on Cd uptake dynamics and transcriptomic response in the marine copepod Tigriopus japonicus. Toxicokinetic results showed significantly higher Cd uptake in copepods under increased temperature and its combination with elevated pCO2 relative to the ambient condition, linking to enhanced Cd bioaccumulation. Transcriptome analysis revealed that, under increased temperature and its combination with elevated pCO2, up-regulated expression of Cd uptake-related genes but down-regulation of Cd exclusion-related genes might cause increased cellular Cd level, which not only activated detoxification and stress response but also induced oxidative stress and concomitant apoptosis, demonstrating aggravated Cd biotoxicity. However, these were less pronouncedly affected by elevated pCO2 exposure. Therefore, temperature seems to be a primary factor in increasing Cd accumulation and its toxicity in the future ocean. Our findings suggest that we should refocus the interactive effects between climate change stressors and Cd pollution, especially considering temperature as a dominant driver.

Competitive adsorption of quinary heavy metal ions onto chestnut shell activated carbon

For several decades, heavy metals have been a source of environmental pollution and the scientific community is continually asked for facing this threat. This study investigated the performance of an activated carbon made from chestnut shell (CNS-AC) in adsorbing Cd(II), Cr(VI), Ni(II), Cu(II), and Zn(II) in single and quinary-metal systems. The CNS-AC was characterized using FT-IR, TGA/DTG, FEG-SEM, EDX, and BET. Experimental results revealed that the adsorption follows the pseudo-second order kinetics, both in single and quinary systems. The equilibrium results reflect the Langmuir equilibrium model, with maximum adsorption capacities (mg.g−1) varying from 21.34 for Cd(II) to 73.16 for Zn(II); in single-metal systems, and from 9.80 for Cd(II) to 33.33 for Cu(II); in the quinary-metal systems. The overall maximum adsorption capacity in quinary-metal solution was of 113.22 mg g−1, higher than qm for each single-metal system. Furthermore, it was found that Cd(II) and Zn(II) pollution abatement to the standard limits was achieved in only one stage while two stages were enough to achieve the related pollution abatement for the other metals. A computational investigation was conducted using the Gaussian 09 and Density Functional Theory (DFT) methods, assuming the generation of organometallic complexes between the functionalized activated carbon and the metal ions. CNS-AC's carboxyl and amine functional groups seemed to be involved in the metal ions adsorption. The calculated bonding energies between the adsorbent and metal ions decreased in the following order Cu(II) < Cr(VI) < Ni(II) < Zn(II) < Cd(II). Correspondingly, experimental results revealed an actual competition between heavy metals for adsorption sites where Zn(II), Ni(II), and Cd(II) removal was hindered by the other metal ions occurrence while Cr(VI) and Cu(II) removal rates have remained broadly unchanged. The new insights brought by the theoretical study combined to the experimental investigation highlights the CNS-AC efficacy as adsorbent for Cd(II), Cr(VI), Ni(II), Cu(II), and Zn(II) removal.

Synergistic effects of modified biochar and selenium on reducing heavy metal uptake and improving pakchoi growth in Cd, Pb, Cu, and Zn–contaminated soil

Heavy metal stress poses a significant threat to both crop production and human health. The application of biochar and selenium (Se) to remediate soil Cd pollution and alleviate plant Cd toxicity has been extensively investigated. However, under Cd, Pb, Cu, and Zn stress, the synergistic mechanisms of key components in lignin–based modified biochar (BC) and foliar selenium fertilizer promoting plant growth and development still need further investigation. The results indicated that, compared to the control, the simultaneous application of BC and foliar selenium fertilizer significantly increased the soil dissolved organic carbon, available silicon, and exchangeable magnesium, while reducing the bioavailability of Cd, Pb, Cu, and Zn by 27.35 %, 42.50 %, 14.50 %, and 11.79 %, respectively. The synergistic interaction between silicon silicate minerals in BC and selenium plays a crucial role in enhancing chlorophyll content, improving photosynthesis, and boosting both enzymatic antioxidant systems (CAT and SOD) and non–enzymatic antioxidant systems (GSH). Interestingly, the combined application of BC and Se shows a more pronounced effect, reducing the absorption of Cd, Zn, Pb, and Cu by pakchoi by 56.04 %, 53.21 %, 32.54 %, and 18.22 %, respectively. This study provides an effective and practical approach to alleviate the composite toxicity of plants to multiple metals such as Cd, Pb, Cu, and Zn. The synergistic effects of BC and Se in reducing heavy metal uptake by pakchoi have significant implications for sustainable agriculture and environmental remediation.