Effect of uncontrolled fertilization and heavy metal toxicity associated with arsenic(As), lead(Pb) and cadmium (Cd), and possible remediation

Risk assessment of potentially toxic elements, microplastics, and microorganisms in groundwater around municipal solid waste landfill

Risk assessment of potential toxic elements (PTEs), microplastics (MPs) and microorganisms in groundwater around landfills is critical. Waste from landfills seeps into groundwater contaminating water quality, threatening groundwater safety, and negatively affecting the ecosystem. This study explored spatial and temporal changes in PTEs, MPs, and microorganisms in the groundwater around a closed landfill. The results showed that Mn and Cr were the most predominant PTEs in the groundwater, average Mn and Cr concentrations in June being 1.16 and 4.51 times higher than in November, respectively. The Risk assessment of PTEs in groundwater Mn was heavily contaminated, Cr was moderately contaminated. The abundance of MPs the average value of MPs in June was 1.55 times higher than that in November; the MPs indicated that groundwater is more heavily contaminated, especially in the downstream areas. The Proteobacteria is the main phylum, and PLS-PM, PTEs were positively correlated with the phylum of microorganisms, negatively correlated with the genus of microorganisms and the abundance of MPs. This study emphasizes the importance of environmental management of landfills, provide new insights into the monitoring and identification of groundwater contamination as well as scientific guidance on appropriate remediation strategies for leachate-contaminated groundwater.

Sustainable Pb(II) Removal and Recovery from Wastewater Using a Bioinspired Metal-Phenolic Hybrid Membrane with Efficient Regeneration

High-performance adsorbents often require efficient selectivity in wastewater, recoverability, and ease of multiple regeneration cycles, but achieving this remains a significant challenge. We report a new strategy for the efficient removal of lead (Pb(II)) from contaminated water streams using an innovative tannic acid (TA)-Fe(III)-based metal-phenolic network (MPN) hybrid membrane (MPN-PAM). This novel membrane exploits the tunable pH-sensitive coordination structure of the MPN to achieve selective removal and recovery of Pb(II) while enabling efficient membrane regeneration by filtration. This membrane demonstrates superior selectivity for Pb(II) with a removal efficiency of up to 98 % and an adsorption capacity of approximately 117.58 mg/g, even in the presence of high salinity, as well as coexisting heavy metals. The membrane maintains high Pb(II) removal efficiency over 20 consecutive cycles and 95 % efficiency over 10 regeneration cycles. Under continuous operation, it treats approximately 85 L per m2 of membrane, reducing Pb(II) concentrations to trace levels (~40 μg/L), meeting electroplating wastewater standard (GB21900-2008). Additionally, even low concentrations of Pb(II) (<5 mg/L) are efficiently purified to below WHO drinking water standard (10 μg/L). The operational cost for treating Pb(II)-contaminated wastewater is about $0.13 per ton, highlighting the cost-effectiveness and potential for large-scale application in wastewater treatment.

Wood biochar induced metal tolerance in Maize (Zea mays L.) plants under heavy metal stress

Due to metal toxicity, widespread industrialization has negatively impacted crop yield and soil quality. The current study was aimed to prepare and characterize biochar made from wood shavings of Pinus roxburghii and to determine the plant growth promoting and heavy metal detoxification of cadmium (Cd) and chromium (Cr) contaminated soil. FTIR SEM coupled with EDX characterization of biochar was performed; Cd and Cr were used at a rate of 20 mg/kg. Biochar was used at the rate of 50 mg/kg for various treatments. The completely randomized design (CRD) was used for the experiment and three replicates of each treatment were made. Various agronomic and enzymatic parameters were determined. The results indicated that all growth and enzymatic parameters were enhanced by the prepared biochar treatments. The most prominent results were observed in treatment T5 (in which shoot length, root length, peroxidase dismutase (POD), superoxide dismutase (SOD) catalyzes (CAT), and chlorophyll a and b increased by 28%, 23%, 40%, 41%, 42%, and 27%, respectively, compared to the control). This study demonstrated that biochar is a sustainable and cost-effective approach for the remediation of heavy metals, and plays a role in plant growth promotion. Farmers may benefit from the current findings, as prepared biochar is easier to deliver and more affordable than chemical fertilizers. Future research could clarify how to use biochar optimally, applying the minimum amount necessary while maximizing its benefits and increasing yield.

Genome-wide analysis of miR172-mediated response to heavy metal stress in chickpea (Cicer arietinum L.): physiological, biochemical, and molecular insights

BACKGROUND

Chickpea (Cicer arietinum L.), a critical diploid legume in the Fabaceae family, is a rich source of protein, vitamins, and minerals. However, heavy metal toxicity severely affects its growth, yield, and quality. MicroRNAs (miRNAs) play a crucial role in regulating plant responses to both abiotic and biotic stress, including heavy metal exposure, by suppressing the expression of target genes. Plants respond to heavy metal stress through miRNA-mediated regulatory mechanisms at multiple physiological, biochemical, and molecular levels. Although the Fabaceae family is well represented in miRNA studies, chickpeas have been notably underrepresented. This study aimed to investigate the effects of heavy metal-induced stress, particularly from 100 µM concentrations of cadmium (Cd), chromium (Cr), nickel (Ni), lead (Pb), and 30 µM arsenic (As), on two chickpea varieties: ILC 482 (sensitive) and Azkan (tolerant). The assessment focused on physiological, biochemical, and molecular parameters. Furthermore, a systematic characterization of the miR172 gene family in the chickpea genome was conducted to better understand the plant's molecular response to heavy metal stress.

RESULTS

Variance analysis indicated significant effects of genotype (G), treatment (T), and genotype-by-treatment (GxT) interactions on plant growth, physiological, and biochemical parameters. Heavy metal stress negatively impacted plant growth in chickpea genotypes ILC 482 and Azkan. A reduction in chlorophyll content and relative leaf water content was observed, along with increased cell membrane damage. In ILC 482, the highest hydrogen peroxide (H₂O₂) levels in shoot tissue were recorded under As, Cd, and Ni treatments, while in Azkan, peak levels were observed with Pb treatment. Malondialdehyde (MDA) levels in root tissue were highest in ILC 482 under Cd and Ni exposure and in Azkan under As, Cr, and Cd treatments. Antioxidant enzyme activities, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX), were significantly elevated under heavy metal stress in both genotypes. Gene expression analysis revealed upregulation of essential antioxidant enzyme genes, such as SOD, CAT, and APX, with APX showing notable increases in both shoot and root tissues compared to the control. Additionally, seven miR172 genes (miR172a, miR172b, miR172c, miR172d, miR172e, miR172f, and miR172g) were identified in the chickpea genome, distributed across five chromosomes. All genes exhibited conserved hairpin structures essential for miRNA functionality. Phylogenetic analysis grouped these miR172 genes into three clades, suggesting strong evolutionary conservation with other plant species. The expression analysis of miR172 and its target genes under heavy metal stress showed varied expression patterns, indicating their role in enhancing heavy metal tolerance in chickpea.

CONCLUSIONS

Heavy metal stress significantly impaired plant growth and physiological and biochemical parameters in chickpea genotypes, except for cell membrane damage. The findings underscore the critical role of miR172 and its target genes in modulating chickpea's response to heavy metal stress. These insights provide a foundational understanding for developing stress-tolerant chickpea varieties through miRNA-based genetic engineering approaches.

Fe3O4/Mulberry Stem Biochar as a Potential Amendment for Highly Arsenic-Contaminated Paddy Soil Remediation

Magnetite-loaded biochar has recently received attention owing to its ability to remove arsenic from contaminated soil. In this study, mulberry stem biochar (MBC) and Fe3O4-loaded mulberry stem biochar (Fe3O4@MBC) were produced and used in a 100-day incubation experiment to investigate their performance in the stabilization of arsenic in paddy soil severely polluted by the As (237.68 mg·kg-1) mechanism. Incubation experiments showed that Fe3O4@MBC was more effective in immobilizing As after incubation for 100 days. Moreover, adding Fe3O4@MBC facilitated the transformation of exchangeable heavy metals into organic-bound and residual forms, thereby reducing As available concentrations, mobility, and bioavailability in the soil, and elevating slightly the soil pH and dissolved organic carbon (DOC). The concentration of TCLP-extractable As (AsTCLP) in contaminated soil was reduced from 93.85 to 7.64 μg·L-1 within 10 d, below the safety limit for drinking water set by the World Health Organization (WHO). The characterization results of Fe3O4@MBC after incubation indicated that the mechanisms for As passivation are linked to redox reactions, complexation, electrostatic attraction, surface adsorption, and coprecipitation. Conclusively, Fe3O4@MBC is a promising amendment in highly As-contaminated soil and provides a theoretical reference in such polluted paddy soil remediation.

Public health and economic burden of heavy metals in Ethiopia: Review

Heavy metals pose a significant threat to public health and economic stability in Ethiopia, contaminating various environmental media, including water, soil, and air. This paper aimed to provide an overview of the public health and economic burden of heavy metals in Ethiopia. Exposure to heavy metals such as lead, mercury, cadmium, and arsenic has been linked to numerous adverse health effects, including neurological disorders, renal failure, cardiovascular diseases, and cancer. In Ethiopia, populations are particularly vulnerable to heavy metal exposure due to various factors, such as artisanal mining, industrial activities, agricultural practices, and inadequate waste management systems. The economic burden of heavy metal contamination manifests through increased healthcare costs, loss of productivity, and environmental remediation expenses. Furthermore, the impact extends to sectors such as agriculture and tourism, affecting national development goals and exacerbating poverty levels. Efforts to mitigate the public health and economic burdens of heavy metals in Ethiopia require multidisciplinary approaches, including policy interventions, regulatory enforcement, public awareness campaigns, and investment in sustainable development practices. Strengthening monitoring systems, implementing pollution control measures, and promoting research on alternative technologies for waste management are essential steps toward addressing this pressing issue. In conclusion, addressing the public health and economic challenges posed by heavy metal contamination in Ethiopia necessitates concerted efforts from the government, industry, academia, and civil society to safeguard human health, preserve the environment, and promote sustainable development.

Root exudate-assisted phytoremediation of copper and lead contamination using Rumex acetosa L. and Rumex K-1

Heavy metal pollutants can be effectively removed from soil through phytoremediation using root exudates. Herein, experiments were conducted to assess the phytoremediation capabilities of Rumex acetosa L. and Rumex K-1 root exudates for copper (Cu) and lead (Pb) contamination. Results indicated that these root exudates effectively adsorbed Cu and Pb. Furthermore, the optimal adsorption conditions of Cu by the root exudates of both plants were as follows: light duration of 36 h, light intensity of 8000 Lx, temperature of 25 °C and CO(NH2)2 concentration of 0 %. Moreover, the optimal adsorption conditions of Pb by Rumex acetosa L. and Rumex K-1 root exudates were light duration of 48 h and 24 h, respectively, light intensity of 8000 Lx, temperature of 25 °C and CO(NH2)2 concentration of 0 %. In addition, the root exudates from both plants enhanced the enrichment and transport of Cu and Pb. Moreover, the root was found to be the main accumulation site of Pb, while the stems and leaves were the main accumulation sites of Cu. With the application of root exudates, plant growth increased, with growth indices in Rumex acetosa L. and Rumex K-1 groups treated with exudates being 1.08-1.81-fold and 1.06-1.9-fold higher, respectively, compared with the untreated ones; physiological indexes showed 1.14-2.62-fold and 1.14-2.71-fold improvements, respectively. Remediation efficiency indexes showed 1.05-1.62-fold and 1.10-1.89-fold improvements, respectively. Rumex acetosa L. and Rumex K-1 exhibited promising potential for the phytoremediation of Cu and Pb, with root exudates playing a critical role in metal adsorption and stabilisation, suggesting their potential for enhancing remediation capabilities. This study sheds light on the mechanisms of root exudate-assisted phytoremediation and provides insights into alleviating heavy metal pollution.

A nationwide study of heavy metal(loid)s in agricultural soils and the soil-grown black morel Morchella sextelata in China

The accumulation of heavy metal(loid)s (HMs) in soil-grown mushrooms poses potential health risks. Morchella sextelata (black morel) is a typical soil-grown mushroom with a rapidly expanding cultivation area. This study investigated the distribution of arsenic, cadmium, chromium, copper, mercury, nickel, lead, and zinc in 213 pairs of soil and morel samples collected from 29 provincial administrative regions in China, together with the nutritional contents in the morel samples. The HM contents in the arable soils used to cultivate morels were 2.4-33.1 times higher than those in desert soils, while the HM contents in arable-soil morels were 2.9-155.9 times higher than desert morels. The HM contents of morels and their cultivation soils were significantly correlated (0.465 ≤ R ≤ 0.778, P < 0.001). Furthermore, the enrichment factors of most HMs were higher in arable soils than in desert soils (P < 0.05), except Hg. A considerable proportion of the arable soils produced morels with HMs exceeding the risk control standards (RCSs) for food and the health-risk thresholds of dietary intake. In comparison, HMs in morels from desert soils were far below the RCSs and health-risk thresholds. In addition, desert morels contained higher contents of crude proteins, total polysaccharides, and free amino acids (P < 0.001). These findings indicate that growing morels in desert soils is a way of green production that provides mushroom products with improved safety and nutrition.

Fertilized soils enhance the efficiency of phytoremediation by tropical grasses in cadmium-contaminated soils

The effectiveness of phytoremediation in Cd-contaminated soils is crucial for enhancing nutrient availability and plant tolerance to Cd. We simulated soil contamination with varying textures and fertilization conditions. Two experiments were conducted: one without liming and fertilization and another with soil fertilization for grasses. The soil types used were Oxisol and Entisol, and the grasses tested were Megathyrsus maximus and Urochloa brizantha at three Cd levels: 0 mg kg-1 (Control), 2 mg kg-1 (Low), and 12 mg kg-1 (High). Soil amendments and fertilization did not significantly change Cd availability. Soil chemical attributes were unaffected by Cd contamination but were influenced by fertilization, which kept the pH below optimal levels. Cd availability was higher in more contaminated soils, with Entisol showing greater concentrations than Oxisol. Dry matter production of the grasses decreased with higher contamination, with U. brizantha being more productive than M. maximus in fertilized soils. Cd accumulation was higher in highly contaminated soils, particularly for U. brizantha. The bioconcentration factor was higher in Entisol, while the translocation factor exceeded 1.0 only for M. maximus in low-contamination Oxisol. Fertilization can mitigate Cd contamination effects, with U. brizantha showing greater tolerance and accumulation capacity in fertilized soils.

Ferrocene-based metal-organic frameworks with dual synergistic active sites for selectively electrochemical removal of arsenic from contaminated water

The effective removal of trace levels of the highly toxic arsenite (As(Ⅲ)) from groundwater is crucial to address the threat to drinking water supply. Herein, we developed an electrochemical separation system utilizing redox-active ferrocene-based metal-organic frameworks (termed Fe-DFc) for selective removal of As(III). This system leveraged 1,1'-ferrocenedicarboxylic acid as a ligand coordinated with iron, enabling the highly selective capture and conversion of As(III) from groundwater. The Fe-DFc electrode-based electrochemical system not only effectively removed As(III) even in the presence of a 1250-fold excess of competing electrolytes, but also converted about 96 % of the adsorbed As(III) into the less toxic As(V), surpassing the results of those documented in the current literature. X-ray absorption fine structure analysis and density functional theory calculations demonstrated that the high selectivity of Fe-O6 moiety and the exceptional redox activity of Fc synergistically contributed to the efficient removal of As(III). Moreover, the electrochemical separation system enabled the remediation of arsenic-contaminated groundwater at a low energy cost of 0.033 kWh m-3 during long-term operation, highlighting the application potential of the electrochemical technology for arsenic removal from contaminated water.

Effects of nitrogen forms on Cd uptake and tolerance in wheat seedlings

Hydroponic experiment was conducted to explore the effects of two nitrogen (N) levels with five nitrate nitrogen (NO3--N) and ammonium nitrogen (NH4+-N) ratios on the growth status and Cd migration patterns of wheat seedlings under Cd5 and Cd30 level. Results showed that higher Cd were detrimental to the growth, absorption of K and Ca, expression of genes mediating NO3--N and NH4+-N transport, which also increased the content of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in shoots and roots of wheat seedlings. Higher N treatment alleviated the inhibitory effects of Cd stress on the biomass, root development, photosynthesis and increased the tolerance index of wheat seedlings. The ratio of NO3--N and NH4+-N was the main factor driving Cd accumulation in wheat seedlings, the combined application of NH4+-N and NO3--N was more conducive for the growth, nitrogen assimilation and Cd tolerance to the Cd stressed wheat seedlings. Increased NO3--N application rates significantly up-regulated the expression levels of TaNPF2.12, TaNRT2.2, increased NH4+-N application rates significantly up-regulated the expression levels of TaAMT1.1. The high proportion of NO3--N promoted the absorption of K, Ca and Cd in the shoots and roots of wheat seedlings, while NH4+-N was the opposite. Under low Cd conditions, the NO3--N to NH4+-N ratio of 1:1 was more conducive to the growth of wheat seedlings, under high Cd stress, the optimal of NO3--N to NH4+-N was 1:2 for inhibiting the accumulation of Cd in wheat seedlings. The results indicated that increasing NH4+-N ratio appropriately could inhibit wheat Cd uptake by increasing NH4+, K+ and Ca2+ for K and Ca channels, and promote wheat growth by promoting N assimilation process.

Heavy metal impacts on antioxidants in cow blood from wastewater-irrigated areas

The aim of the present research was to investigate the presence of heavy metals such as lead (Pb), copper (Cu), chromium (Cr), and cadmium (Cd) in blood samples from cows raised with irrigated wastewater, as well as in the wastewater itself, in the North-western region of Pakistan. A total of 60 blood samples were collected from five different locations in Kohat, namely Tappi Road (TR), Pindi Road (PR), Gul Malik Road (GMR), Markaz Road (MR), and a control group. The samples of both i.e. cow blood and wastewater were analyzed for the concentrations of heavy metals. The highest concentration of Cd was detected in the MR site with a mean value of 0.03 mg/L, and the highest concentration of Cu (0.04 mg/L) was recorded in the TR site, while the lowest level was found in the control group with a mean of 0.002 mg/L in blood samples. The highest Cr and Pb concentrations were found at the PR site, with mean values of 0.03 and 0.07 mg/L, respectively, whereas the control group had the lowest concentrations, with mean values of 0.002 and 0.01 mg/L. Similarly, heavy metal concentrations were analyzed in wastewater used for irrigation in the study area. Results indicated elevated concentrations of Cu and Cr in wastewater, although they remained below the World Health Organization (WHO) recommended values except for Cr (0.13 mg/L) in the GMR site, which exceeded permissible limits. Cd and Pb concentrations in wastewater were relatively low, but Cd concentration surpassed WHO limits, particularly with a mean concentration of 0.08 mg/L in the TR site. Comparison between heavy metal concentrations in blood and wastewater revealed higher values of Cd and Pb in blood samples than in wastewater, while Cu and Cr concentrations were higher in water compared to blood. Additionally, elevated levels of Super Oxide Dismutase (SOD), antioxidant enzyme Catalase (CAT), and oxidative stress marker malondialdehyde (MDA) were detected in blood samples. Cluster and principal component analyses were employed to assess heavy metal toxicity among the groups, indicating potential long-term adverse health effects on animals, transfer to humans, and toxicity in living organisms.

The Effectiveness of Time in Treatment with Vitamin C and Broccoli Extract on Cadmium Poisoning in Mice: Histological Changes of Testicular Tissue and Cell Apoptotic Index

The growth rate of reproductive system disorders caused by heavy metals is undeniable. The effect of time and interfering compounds are also of paramount importance. The main objective of this study was to compare the effects of broccoli extract and vitamin C in the context of cadmium poisoning on various reproductive parameters in mice, with a specific focus on the influence of time. A total of one hundred and forty-four male mice were randomly assigned to six groups. The control (C) group received only water and a standard diet without any interventions. The Cd group received a single intraperitoneal dose of cadmium chloride at 1.5 mg/kg. The cadmium intervention groups were administered broccoli extract at dosages of 100 mg/kg (Cd + B100), 200 mg/kg (Cd + B200), and 300 mg/kg (Cd + B300), respectively. Additionally, the Cd + VC group was treated with cadmium and vitamin C at 200 mg/kg intraperitoneally for a duration of 28 days. At the end of each week (four stages), five animals were randomly chosen from each group. Epididymal sperm were subjected to analysis for sperm parameters, while testicular tissue sections were examined for histological studies, apoptosis index, and markers of oxidative stress. The influence of time on body and testis weight gain was notably significant in the Cd + B300 and Cd + VC groups (p = 0.001). In all groups, except for Cd + B100, there were marked increases in spermatogenic cell lines and the Johnson coefficient compared to the Cd group (p = 0.001). These changes were particularly pronounced in the Cd + VC and Cd + B300 groups with respect to time (p < 0.001). Furthermore, there was a discernible positive impact of time on sperm count in the high-dose broccoli and vitamin C groups, although this effect did not reach significance in terms of sperm motility and vitality. Over time, the levels of superoxide dismutase (SOD) and catalase (CAT) enzymes increased, while malondialdehyde (MDA) levels decreased in the Cd + VC, Cd + B200, and Cd + B300 groups (p = 0.001). The apoptosis index in testicular tissue reached its highest level in the Cd group and its lowest level in the Cd + B300 and Cd + VC groups during the fourth week (p < 0.05). Linolenic acid, indole, and sulforaphane were identified as the most potent compounds in broccoli during this intervention. Consequently, vitamin C and broccoli extract at a dosage of 300 mg/kg demonstrated significant enhancements in reproductive performance in cases of cadmium poisoning. Overall, the influence of time significantly amplified the process of spermatogenesis and sperm production, with no observable changes in sperm viability and motility.

Accumulation and translocation of lead in vegetables through intensive use of organic manure and mineral fertilizers with wastewater

In many countries with wastewater irrigation and intensive use of fertilizers (minerals and organics), heavy metal deposition by crops is regarded as a major environmental concern. A study was conducted to determine the impact of mineral fertilizers, cow manure, poultry manure, leaf litter, and sugarcane bagasse on soil's trace Pb content and edible parts of vegetables. It also evaluated the risk of lead (Pb) contamination in water, soil, and food crops. Six vegetables (Daucus carota, Brassica oleracea, Pisum sativum, Solanum tuberosum, Raphanus sativus, and Spinacia oleracea) were grown in the field under twelve treatments with different nutrient and water inputs. The lead concentrations in soil, vegetables for all treatments and water samples ranged from 1.038-10.478, 0.09346-9.0639 mg/kg and 0.036-0.26448 mg/L, The concentration of lead in soil treated with wastewater in treatment (T6) and vegetable samples was significantly higher, exceeding the WHO's permitted limit. Mineral and organic fertilizers combined with wastewater treatment reduced lead (Pb) concentrations in vegetables compared to wastewater application without organic fertilizers. Health risk indexes for all treatments except wastewater treatment (T6) were less than one. Pb concentrations in mineral fertilizers, cow manure, poultry manure, leaf litter, and sugarcane bagasse treated were determined to pose no possible risk to consumers.

Effect of fertilization on the accumulation and health risk for heavy metals in native Andean potatoes in the highlands of Perú

Soil infertility is a global problem, amendments such as organic fertilizers and mineral fertilizers are used to improve crop yields. However, these fertilizers contain heavy metals as well as essential mineral elements. The objective of the study was to determine the effect of organic and inorganic fertilizer on the accumulation and health risk of heavy metals in tubers. The plants were cultivated at an altitude of 3970 m using four treatments (poultry manure, alpaca manure, island guano and inorganic fertilizer) and a control group. Soil contamination levels and the degree of metal accumulation in the tubers were also determined. As a result, it was found that the use of inorganic fertilizer and poultry manure increased the values of Cu and Zn in soils, exceeding the recommended standards. The accumulation of heavy metals in potato tubers did not exceed the maximum recommended limits with the exception of Pb, which exceeded the limit allowed by the FAO/WHO (0.1 mg kg-1). Poultry manure contributed to the highest accumulation of Zn, Cu and Pb in tubers with 11.62±1.30, 3.48±0.20 and 0.12 ±0.02 mg kg-1 respectively. The transfer of metals from the soil to the tubers was less than 1. Individual and total non-carcinogenic risk values were less than 1, indicating a safe level of consumption for children and adults. The cancer risk was found to be within an acceptable range. However, poultry manure and inorganic fertilizer treatments had the highest total cancer risk values in both age groups, suggesting a long-term carcinogenic risk.

The Cd immobilization mechanisms in paddy soil through ureolysis-based microbial induced carbonate precipitation: Emphasis on the coexisting cations and metatranscriptome analysis

Microbial induced carbonate precipitation (MICP) can immobilize metals and reduce their bioavailability. However, little is known about the immobilization mechanism of Cd in the presence of soil cations and the triggered gene expression and metabolic pathways in paddy soil. Thus, microcosmic experiments were conducted to study the fractionation transformation of Cd and metatranscriptome analysis. Results showed that bioavailable Cd decreased from 0.62 to 0.29 mg/kg after 330 d due to the MICP immobilization. This was ascribed to the increase in carbonate bound, Fe-Mn oxides bound, and residual Cd. The underlying immobilization mechanisms could be attributed to the formation of insoluble Cd-containing precipitates, the complexation and lattice substitution with carbonate and Fe, Mn and Al (hydr)oxides, and the adsorption on functional group on extracellular polymers of cell. During the MICP immobilization process, up-regulated differential expression urease genes were significantly enriched in the paddy soil, corresponding to the arginine biosynthesis, purine metabolism and atrazine degradation. The metabolic pathway of bacterial chemotaxis, flagellum assembly, and peptidoglycan biosynthesis and the expression of cadA gene related to Cd excretion enhanced Cd resistance of soil microbiome. Therefore, this study provided new insights into the immobilization mechanisms of Cd in paddy soils through ureolysis-based MICP process.

Novel findings from arsenic‑lead combined exposure in mouse testicular TM4 Sertoli cells based on transcriptomics

Arsenic (As) and lead (Pb) exist widespread in daily life, and they are common harmful substances in the environment. As and Pb pollute the environment more often in combination than in isolation. The TM4 Sertoli cell line is one of the most common normal mouse testicular Sertoli cell lines. In vitro, we found that the type of combined action of As and Pb on TM4 Sertoli cells was additive action by using the isobologram analysis. To further investigate the combined toxicity of As and Pb, we performed mRNA and miRNA sequencing on TM4 Sertoli cells exposed to As alone (4 μM NaAsO2) and AsPb combined (4 μM NaAsO2 and 150 μM PbAc), respectively. Compared with the control group, 1391 differentially expressed genes (DEGs) and 6 differentially expressed miRNAs (DEMs) were identified in the As group. Compared with the control group, 2384 DEGs and 44 DEMs were identified in the AsPb group. Compared with the As group, 387 DEGs and 4 DEMs were identified in the AsPb group. Through data analysis, we discovered for the first time that As caused the dysfunction of cholesterol synthesis and energy metabolism, and disrupted cyclic adenosine monophosphate signaling pathway and wingless/integrated (Wnt) signaling pathway in TM4 Sertoli cells. In addition to affecting cholesterol synthesis and energy metabolism, AsPb combined exposure also up-regulated the antioxidant reaction level of TM4 Sertoli cells. Meanwhile, the Wnt signaling pathway of TM4 Sertoli cells was relatively normal when exposed to AsPb. In conclusion, at the transcription level, the combined action of AsPb is not merely additive effect, but involves synergistic and antagonistic effects. The new discovery of the joint toxic mechanism of As and Pb breaks the stereotype of the combined action and provides a good theoretical basis and research clue for future study of the combined-exposure of harmful materials.

Biological roles of soil microbial consortium on promoting safe crop production in heavy metal(loid) contaminated soil: A systematic review

Heavy metal(loid) (HM) pollution of agricultural soils is a growing global environmental concern that affects planetary health. Numerous studies have shown that soil microbial consortia can inhibit the accumulation of HMs in crops. However, our current understanding of the effects and mechanisms of inhibition is fragmented. In this review, we summarise extant studies and knowledge to provide a comprehensive view of HM toxicity on crop growth and development at the biological, cellular and the molecular levels. In a meta-analysis, we find that microbial consortia can improve crop resistance and reduce HM uptake, which in turn promotes healthy crop growth, demonstrating that microbial consortia are more effective than single microorganisms. We then review three main mechanisms by which microbial consortia reduce the toxicity of HMs to crops and inhibit HMs accumulation in crops: 1) reducing the bioavailability of HMs in soil (e.g. biosorption, bioaccumulation and biotransformation); 2) improving crop resistance to HMs (e.g. facilitating the absorption of nutrients); and 3) synergistic effects between microorganisms. Finally, we discuss the prospects of microbial consortium applications in simultaneous crop safety production and soil remediation, indicating that they play a key role in sustainable agricultural development, and conclude by identifying research challenges and future directions for the microbial consortium to promote safe crop production.

An integrated overview of metals contamination, source-specific risks investigation in coal mining vicinity soils

Heavy metals in soil are harmful to natural biodiversity and human health, and it is difficult to estimate the effects accurately. To reduce pollution and manage risk in coal-mining regions, it is essential to evaluate risks for heavy metals in soil. The present study reviews the levels of 21 metals (Nb, Zr, Ag, Ni, Na, K, Mg, Rb, Zn, Ca, Sr, As, Cr, Fe, Pb, Cd, Co, Hg, Cu, Mn and Ti) in soils around Barapukuria coal-mining vicinity, Bangladesh which were reported in literature. An integrated approach for risk assessments with the positive matrix factorization (PMF) model, source-oriented ecological and health hazards were applied for the study. The contents of Rb, Ca, Zn, Pb, As, Ti, Mn, Co, Ag, Zr, and Nb were 1.63, 1.10, 1.97, 14.12, 1.20, 3.13, 1.22, 3.05, 3.85, 5.48, and 7.21 times greater than shale value. About 37%, 67%, 12%, and 85% of sampling sites posed higher risks according to the modified contamination factor, Nemerow pollution index, Nemerow integrated risk index, and mean effect range median quotient, respectively. Five probable metal sources were computed, including industrial activities to coal mining (17%), agricultural activities (33%), atmospheric deposition (19%), traffic emission (16%), and natural sources (15%). Modified Nemerow integrated risk index reported that agricultural activities, industrial coal mining activities, and atmospheric deposition showed moderate risk. Health hazards revealed that cancer risk values computed by the PMF-HHR model with identified sources were higher than the standard value (1.0E-04) for children, adult male, and female. Agricultural activities showed higher cancer risks to adult male (39%) and children (32%) whereas traffic emission contributed to female (25%). These findings highlight the ecological and health issues connected to potential sources of metal contamination and provide useful information to policymakers on how to reduce such risks.

Use of La-Co@NPC for Sulfite Oxidation and Arsenic Detoxification Removal for High-Quality Sulfur Resources Recovery in Desulfurization Process

Ammonia desulfurization is a typical resource-recovery-type wet desulfurization process that is widely used in coal-fired industrial boilers. However, the sulfur recovery is limited by the low oxidation rate of byproduct (ammonium sulfite), leading to secondary SO2 pollution due to its easy decomposability. In addition, the high toxic arsenic trace substances coexisting in desulfurization liquids also reduce the quality of the final sulfate product, facing with high environmental toxicity. In this study, nitrogen-doped porous carbon coembedded with lanthanum and cobalt (La-Co@NPC) was fabricated with heterologous catalytic active sites (Co0) and adsorption sites (LaOCl) to achieve sulfite oxidation and the efficient removal of high toxic trace arsenic for the recovery of high-value ammonium sulfate from the desulfurization liquid. The La-Co@NPC/S(IV) catalytic system can generate numerous strongly oxidizing free radicals (·SO5- and ·O2-) for the sulfite oxidation on the Co0 site, as well as oxidative detoxification of As(III) into As(V). Subsequently, arsenic can be removed through chemical adsorption on LaOCl adsorption sites. By using the dual-functional La-Co@NPC at a concentration of 0.25 g/L, the rate of ammonium sulfite oxidation reached 0.107 mmol/L·s-1, the arsenic (1 mg/L) removal efficiency reached 92%, and the maximum adsorption capacity of As reached up to 123 mg/g. This study can give certain guiding significance to the functional material design and the coordinated control of multiple coal-fired pollutants in desulfurization for high-value recovery of sulfur resources.

Fertilization of Microbial Composts: A Technology for Improving Stress Resilience in Plants

Microbial compost plays a crucial role in improving soil health, soil fertility, and plant biomass. These biofertilizers, based on microorganisms, offer numerous benefits such as enhanced nutrient acquisition (N, P, and K), production of hydrogen cyanide (HCN), and control of pathogens through induced systematic resistance. Additionally, they promote the production of phytohormones, siderophore, vitamins, protective enzymes, and antibiotics, further contributing to soil sustainability and optimal agricultural productivity. The escalating generation of organic waste from farm operations poses significant threats to the environment and soil fertility. Simultaneously, the excessive utilization of chemical fertilizers to achieve high crop yields results in detrimental impacts on soil structure and fertility. To address these challenges, a sustainable agriculture system that ensures enhanced soil fertility and minimal ecological impact is imperative. Microbial composts, developed by incorporating characterized plant-growth-promoting bacteria or fungal strains into compost derived from agricultural waste, offer a promising solution. These biofertilizers, with selected microbial strains capable of thriving in compost, offer an eco-friendly, cost-effective, and sustainable alternative for agricultural practices. In this review article, we explore the potential of microbial composts as a viable strategy for improving plant growth and environmental safety. By harnessing the benefits of microorganisms in compost, we can pave the way for sustainable agriculture and foster a healthier relationship between soil, plants, and the environment.

Influence of Fertilization on Growth and Lead Content of Pepper under Lead Stress

To investigate the effect of fertilization on Pb content in vegetables, pepper was planted in L1645 (the 5 influencing factors are fertilizers (N, P, K), organic fertilizers (sheep manure) and Pb2+; the 4 levels are blank, low, medium and high; a total of 16 treatments) pot orthogonal experiment. The effects of fertilizers on the growth and Pb content in various parts of pepper under Pb stress were analyzed. The results showed that: (1) The Pb content in pepper fruit ranged from 0.011 mg·kg-1 to 0.085 mg·kg-1, which did not exceed the limit value (0.1 mg·kg-1) in the National Standard for Food Safety-Limit of Contaminants in Food (GB2762-2017); (2) The effect order of fertilization on pepper fruit weight was P2O5 > sheep manure > N > K2O; The horizontal combination of factors that promoted the maximum fruit weight of pepper was N (0.15 g·kg-1), P2O5 (0.225 g·kg-1), K2O (0.15 g·kg-1) and sheep manure (9 g·kg-1); (3) The order of fertilizer effects on Pb content in pepper fruit was Pb2+ > K2O > N = sheep manure > P2O5; the factor level combination that resulted in the maximum Pb content in pepper fruits was N (0.15 g·kg-1), P2O5 (0 g·kg-1), K2O (0.45 g·kg-1), sheep manure (6 g·kg-1) and Pb2+ (350 mg·kg-1); (4) Based on the soil fertility characteristics of Urumqi, the recommended optimal fertilizer application rate was: high phosphorus fertilizer P2O5 (495 kg·hm-2), low-level potassium fertilizer K2O (330 kg·hm-2), medium-level nitrogen fertilizer N (660 kg·hm-2) (or low-level nitrogen fertilizer N (330 kg·hm-2) + high-level organic manure sheep manure (19,800 kg·hm-2), which can achieve high yield while ensuring that the Pb content in the fruits does not exceed the standard. Strengthening control of effective and reasonable fertilization methods in Urumqi agricultural land is helpful to reduce the Pb content in vegetables.

Improvement of cadmium immobilization in contaminated paddy soil by using ureolytic bacteria and rice straw

Cadmium (Cd) in paddy soil can be immobilized via microbially induced carbonate precipitation (MICP), but it poses a risk to the properties and eco-function of the soil. In this study, rice straw coupled with Sporosarcina pasteurii (S. pasteurii) was used to treat Cd-contaminated paddy soil with minimizing the detrimental effects of MICP. Results showed that the application of rice straw coupled with S. pasteurii reduced Cd bioavailability. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed that Cd immobilization efficiency was increased in the rice straw coupled with S. pasteurii treatment via co-precipitating with CaCO₃. Moreover, rice straw coupled with S. pasteurii enhanced soil fertility and ecological functions as reflected by the high amount of alkaline hydrolysis nitrogen (AN) (14.9 %), available phosphorus (AP) (13.6 %), available potassium (AK) (60.0 %), catalase (9.95 %), dehydrogenase (736 %), and phosphatase (214 %). Further, the relative abundance of dominant phyla such as Proteobacteria and Firmicutes significantly increased when applying both rice straw coupled with S. pasteurii. The most significant environmental factors that affected the composition of the bacterial community were AP (41.2 %), phosphatase (34.2 %), and AK (8.60 %). In conclusion, using rice straw mixed with S. pasteurii is a promising application to treat Cd-contaminated paddy soil due to its positive effects on treating soil Cd as well as its ability to reduce the detrimental effects of the MICP process.

Metal-tolerant and siderophore producing Pseudomonas fluorescence and Trichoderma spp. improved the growth, biochemical features and yield attributes of chickpea by lowering Cd uptake

Industrialization and human urbanization have led to an increase in heavy metal (HM) pollution which often cause negative/toxic effect on agricultural crops. The soil-HMs cannot be degraded biologically however, microbe-mediated detoxification of toxic HMs into lesser toxic forms are reported. Considering the potentiality of HMs-tolerant soil microbes in metal detoxification, Pseudomonas fluorescence PGPR-7 and Trichoderma sp. T-4 were recovered from HM-affected areas. Under both normal and cadmium stress, the ability of both microorganisms to produce different plant hormones and biologically active enzymes was examined. Strains PGPR-7 and T-4 tolerated cadmium (Cd) an up-to 1800 and 2000 µg mL^-1, respectively, and produced various plant growth regulating substances (IAA, siderophore, ACC deaminase ammonia and HCN) in Cd-stressed condition. The growth promoting and metal detoxifying ability of both strains were evaluated (either singly/combined) by applying them in chickpea (Cicer arietinum L.) plants endogenously contaminated with different Cd levels (0-400 µg kg^-1 soils). The higher Cd concentration (400 µg kg^-1 soils) negatively influenced the plant parameters which, however, improved following single/combined inoculation of P. fluorescence PGPR-7 and Trichoderma sp. T-4. Both microbial strains increased the growth of Cd-treated chickpeas however, their combined inoculation (PGPR-7 + T-4) caused the most positive effect. For instance, 25 µg Cd Kg^-1 + PGPR-7 + T4 treatment caused maximum increase in germination percentage (10%), root dry biomass (71.4%) and vigour index (33%), chl-a (38%), chl-b (41%) and carotenoid content (52%). Furthermore, combined inoculation of P. fluorescence PGPR-7 and Trichoderma sp. T-4 maximally decreased the proline, MDA content, POD and CAT activities by 50%, 43% and 62%, respectively following their application in 25 µg Cd kg^-1 soils-treated chickpea. Additionally, microbial strains lowered the plant uptake of Cd. For example, Cd-uptake in root tissues was decreased by 42 and 34% when 25 µg Cd Kg^-1- treated chickpea plants were inoculated with P. fluorescence PGPR-7, Trichoderma sp. T-4 and co-inoculation (PGPR-7 + T4) of both strains, respectively. Therefore, from the current observation, it is suggested that dual inoculation of metal tolerant P. fluorescence and Trichoderma sp. may potentially be used in detoxification and reclamation of metal-contaminated soils.