Transport Of Heavy Metals Research Articles

ASSESSMENT OF RISKS AND PROVIDING RECOMMENDATIONS TO MINIMIZE THEIR OCCURRENCE DURING TRANSPORTATION OF CARGO BY RAIL TRANSPORT.

Purpose: To assess the risks of emergency situations and provide recommendations for their minimization during the transportation of goods by rail transport. Method. On the basis of the methods of comparative typology, expert evaluations and system analysis for the route that runs through the industrial districts of Kryvyi Rih, using the methods of analysis of the causes and consequences of a key event, the combined diagram of the Ishikawa tree of a key event, risk maps of a key event, the analysis of hidden and direct priorities was determined indicator of the risk of the complex effect of negative factors of emergency situations during the transportation of heavy metals. The results. the authors identified the most likely causes of the emergency situation: 1) A rocket projectile that damaged the track, as a result of which the spontaneous exit of wagons occurred; 2) Exceeding the speed of a tank train; 3) Icy, which led to an increase in the braking distance and an accident; 4) Neglect of obstacles to movement before the movement of tanks, which in turn can lead to a stoppage of the technological process, cargo spillage and financial losses. A probabilistic risk assessment was carried out on the basis of an expert assessment of the risk operator and measures to reduce the occurrence of emergency situations were proposed with annual costs for them, thousand UAH. After that, a map of probabilistic risk assessment and a map of probabilistic assessment of risk management effects were created, which provide an opportunity for effective management and management of the probable cause of an emergency situation and the selection of financial investments for measures to reduce the occurrence of emergency situations. After that, it was proposed to use the combined wagon model 17-975(01) with all the necessary equipment as a means for quick localization and liquidation of the consequences of spills of emissions of hazardous substances during their transportation by railway transport in the event of an accident. The economic feasibility of using the proposed tool was also substantiated. The scientific novelty consists in the created model for the analysis of the risk assessment of an emergency situation, as well as the identification of possible causes and factors of the occurrence of emergency situations during the transportation of dangerous goods by railway transport, as well as the development of recommendations for their reduction. The practical significance is the implementation of the developed recommendations, based on the created model, for the formation of a special wagon, for operational needs, with the selection of the necessary equipment for the rapid implementation of the 1st stage of localization and liquidation measures.

UV/Advanced Oxidation Process for Removing Humic Acid from Natural Water: Comparison of Different Methods and Effect of External Factors

Humic acid (HA) is an organic compound naturally present in aquatic environments. It has been found to have detrimental effects on water color, the transport of heavy metals, and the elimination of disinfection by-products (DBPs), thereby exerting an impact on human health. This study introduced four synergistic ultraviolet/advanced oxidation processes (UV/AOPs) systems aimed at eliminating HA from water. The research explored the effect of solution pH, duration of illumination, initial reactant concentration, and oxidant concentration on the degradation of HA. The results indicated that the mineralization rate achieved by individual UV or oxidant systems was less than 15%, which is significantly lower compared to UV/AOPs systems. Among these methods, the UV/peroxymonosulfate (UV/PMS) process demonstrated the highest effectiveness, achieving a mineralization rate of 94.15%. UV/peroxydisulfate (UV/PDS) and UV/sodium percarbonate (SPC) were subsequently implemented, with UV/sulfite (S(IV)) demonstrating the lowest effectiveness at 19.8%. Optimal degradation efficiency was achieved when the initial concentration of HA was 10 mg/L, the concentration of PMS was 3 mmol/L, and the initial pH was set at 5, with an illumination time of 180 min. This experimental setup resulted in high degradation efficiencies for chemical oxygen demand (COD), UV254, and HA, reaching 96.32%, 97.34%, and 92.09%, respectively. The energy efficiency of this process (EE/O) was measured at 0.0149 (kWh)/m3, indicating the capability of the UV/PMS system to efficiently degrade and mineralize HA in water. This offers theoretical guidance for the engineered implementation of a UV/PAM process in the treatment of HA.

Factors influencing the distribution, risk, and transport of microplastics and heavy metals for wildlife and habitats in “island” landscapes: From source to sink

Microplastics (MPs) and heavy metals (HMs) are important pollutants in terrestrial ecosystems. In particular, the “island” landscape’s weak resistance makes it vulnerable to pollution. However, there is a lack of research on MPs and HMs in island landscapes. Therefore, we used Helan Mountain as the research area. Assess the concentrations, spatial distribution, ecological risks, sources, and transport of MPs and HMs in the soil and blue sheep (Pseudois nayaur) feces. Variations in geographical distribution showed a connection between human activity and pollutants. Risk assessment indicated soil and wildlife were influenced by long-term pollutant polarization and multi-element inclusion (Igeo, Class I; PHI, Class V; RI (MPs), 33 % Class II, and 17 % Class IV; HI = 452.08). Source apportionment showed that tourism and coal combustion were the primary sources of pollutants. Meanwhile, a new coupling model of PMF/Risk was applied to quantify the source contribution of various risk types indicated transportation roads and tourism sources were the main sources of ecological and health risks, respectively. Improve the traceability of pollution source risks. Furthermore, also developed a novel tracing model for pollutant transportation, revealing a unique “source-sink-source” cycle in pollutant transportation, which provides a new methodological framework for the division of pollution risk areas in nature reserves and the evaluation of spatial transport between sources and sinks. Overall, this study establishes a foundational framework for conducting comprehensive risk assessments and formulating strategies for pollution control and management.

The role of soil structure on the cracking and cadmium leaching behavior of biochar-amended fine-grained soils

Biochar has shown promising potential for soil remediation, yet its impact on heavy metals (HMs) immobilization often overlooks soil structure, which could influence soil cracking behavior and HMs transport. To address this gap, this study investigates the role of soil structure (dry density and aggregate size) on the cracking and cadmium (Cd) leaching behavior of biochar-amended fine-grained soils. A series of semi-dynamic leaching tests were conducted on samples with and without wetting-drying (W-D) cycles. Based on the proposed improved method for quantifying the effective diffusion coefficient (De) of Cd in unsaturated soils and microstructural analyses, we found that: (1) Higher dry density and larger aggregate generally resulted in smaller De by decreasing soil pore volume. (2) Biochar could connect isolated pores within large aggregates through its internal pores, yielding greater increases in De (294.8%–469.0%) compared to small aggregates (29.1%–77.4%) with 3% biochar. However, further increases in biochar dosage led to decreased De, primarily due to the dense pore structure. (3) Biochar effectively inhibited soil cracking, achieving the highest reduction of 36.8% in surface crack ratio. (4) After W-D cycles, samples exhibited higher De with increasing dry density, with aggravated cracking being the primary cause, suggesting preferential flow within the cracks, particularly those penetrating the soil. This study highlights the importance of careful consideration of soil structure and cracking potential before in situ field application of biochar as a remediation agent for HMs-contaminated fine-grained soils.

Exploitation of Grafting for Abiotic and Biotic Stress Management in Vegetable Crops: A Review

Growing vegetables is often impacted by various abiotic and biotic stresses that can hinder growth and yield. Abiotic stresses, such as salinity, water stress, and temperature fluctuations, and biotic stresses, including diseases, pests, and nematodes, pose significant threats to agriculture. Grafting, a horticultural technique, offers a promising solution to overcome these challenges. In cases of salinity stress, grafting with salt-tolerant rootstocks can limit the transport of harmful ions to the shoot and help store them in the roots, mitigating ion toxicity. Water stress, including drought and water logging, can be addressed by grafting with drought-tolerant rootstocks, which can reduce yield losses and enhance photosynthesis under adverse water conditions. Grafting can also improve nutrient uptake, translocation of water, and osmoregulation, thereby assisting plants in surviving under water stress. High and low-temperature stresses, which can disrupt plant metabolism, membrane stability, and growth, can also be addressed through grafting. Grafted plants with temperature-tolerant rootstocks may indirectly enhance tolerance to extreme temperatures. Additionally, grafted plants can adapt to varying temperature conditions by promoting root growth, nutrient absorption, and the production of specific compounds that protect against temperature-related damage. Heavy metal stress, which can contaminate crops and impact human health, can be alleviated by using rootstocks that control the uptake and transport of heavy metals, reducing their toxicity to plants. Furthermore, grafting can effectively combat biotic stresses. By selecting disease-resistant rootstocks, plants can be protected against soil-borne diseases, pests, and nematodes, thereby increasing yields and sustainability in agriculture.

Physiological and transcriptome characterization provide new sights into cadmium tolerance and accumulation mechanisms in Tagetes patula L.

Tagetes patula L. (T. patula) is a Cd hyperaccumulator plant with high ornamental value and strong resistance. Understanding the molecular mechanisms of Cd tolerance in hyper-accumulating plants is important for improving phytoremediation efficiency. This investigation studied to how Cd affected T. patula's physiological characteristics and molecular alterations. With the increase of Cd concentration, chlorophyll content, and root biomass decreased; the activities of antioxidant enzymes such as GST, SOD and POD increased. Initially, Cd accumulated mainly in the root and then transferred upward to the leaves. The molecular mechanisms of T. patula after 150 mg/kg and 250 mg/kg treatments were analyzed by transcriptome. In total, 5429 and 6546 differentially expressed unigenes were identified. Phenylpropanoid biosynthesis and phenylalanine metabolism were identified as key pathways in reaction to Cd stress. In addition, many differential genes involved in the response to Cd stress were identified, including heavy metal transporter protein genes, genes and transcription factors related to Cd detoxification. These results indicate that the response of T. patula to Cd was multifaceted, laying the foundation for studies to improve its tolerance to toxic metals.

Synergistic effects of microplastic stability and adsorption rate on co-transport of microplastics and Pb under surfactant

The emergence of microplastics (MPs) and their coexistence with heavy metal contaminants pose potential risks to the safety of the subsurface environment and public health. Therefore, it is crucial to explore the co-transport of MPs (polypropylene (PP), polyethylene (PE), polystyrene (PS), polymethyl methacrylate (PMMA) and polytetrafluoroethylene (PTFE)) with the heavy metal Pb(II) under the surfactant (sodium dodecyl benzene sulfonate (SDBS) and cetyltrimethylammonium bromide (CTAB)). In this study, column experiments were performed to investigate the co-transport of MPs and Pb(II) under surfactants. The co-transport mechanism of MPs with Pb(II) under surfactant was revealed by MPs stability and batch adsorption experiments. Experimental results showed that the presence of Pb(II) did not influence the mobility of MPs under CTAB and SDBS; however, MPs can affect the mobility of Pb(II). Specifically, under CTAB, the MPs increased the recovery rate of Pb(II) from 86% to 87.55%–97.55%. However, under SDBS, the high mobility of PS, PE, and PP inhibited the transport of Pb(II), and the recoveries of Pb(II) decreased from 79% to 57.53%–70.96%. The low mobility of PTFE and PMMA slightly promoted the transport of Pb(II). This could be attributed to two reasons. One aspect is the adsorption rate of Pb(II) by MPs, which plays a pivotal role in influencing the transport tendency of Pb(II) with MPs. Another aspect is the MPs stability, as greater stability enhances their dispersity and accelerates the adsorption rate of Pb(II), thereby facilitating the co-transport of Pb(II) with MPs. This study could provide valuable insights for assessing the transport and environmental impact of MPs and heavy metals in the presence of surfactants.

Central Roles of ZmNAC128 and ZmNAC130 in Nutrient Uptake and Storage during Maize Grain Filling.

Grain filling is critical for determining yield and quality, raising the question of whether central coordinators exist to facilitate the uptake and storage of various substances from maternal to filial tissues. The duplicate NAC transcription factors ZmNAC128 and ZmNAC130 could potentially serve as central coordinators. By analyzing differentially expressed genes from zmnac128 zmnac130 mutants across different genetic backgrounds and growing years, we identified 243 highly and differentially expressed genes (hdEGs) as the core target genes. These 243 hdEGs were associated with storage metabolism and transporters. ZmNAC128 and ZmNAC130 play vital roles in storage metabolism, and this study revealed two additional starch metabolism-related genes, sugary enhancer1 and hexokinase1, as their direct targets. A key finding of this study was the inclusion of 17 transporter genes within the 243 hdEGs, with significant alterations in the levels of more than 10 elements/substances in mutant kernels. Among them, six out of the nine upregulated transporter genes were linked to the transport of heavy metals and metalloids (HMMs), which was consistent with the enrichment of cadmium, lead, and arsenic observed in mutant kernels. Interestingly, the levels of Mg and Zn, minerals important to biofortification efforts, were reduced in mutant kernels. In addition to their direct involvement in sugar transport, ZmNAC128 and ZmNAC130 also activate the expression of the endosperm-preferential nitrogen and phosphate transporters ZmNPF1.1 and ZmPHO1;2. This coordinated regulation limits the intake of HMMs, enhances biofortification, and facilitates the uptake and storage of essential nutrients.

MTP family analysis and association study reveal the role of ZmMTP11 in lead (Pb) accumulation

The metal tolerance protein (MTP) gene family plays an essential role in the transport of heavy metals, however the function of the MTP family in transporting lead (Pb) was still unclear in plants. In this study, we identified and characterized 12 ZmMTPs in the whole genome of maize. These ZmMTP genes were divided into three subfamilies in evolution, namely Zn-CDF, Zn/Fe-CDF, Mn-CDF subfamilies, which showed diverse expression patterns in different tissues of maize. Using gene-based association analyses, we identified a Pb accumulation-related MTP member in maize, ZmMTP11, which was located in plasma membrane and had the potential of transporting Pb ion. Under the Pb treatment, ZmMTP11 showed a generally decreased expression relative to the normal conditions. Heterologous expressions of ZmMTP11 in yeast, Arabidopsis, and rice demonstrated that ZmMTP11 enhanced Pb accumulation in the cells without affecting yeast and plant growth under Pb stress. Remarkably, the increased Pb concentration in the plant roots did not cause changes in Pb content in the shoots. Our study provides new insights into the genetic improvement of heavy metal tolerance in plants and contributes to bioremediation of Pb-contaminant soils.

Effects of atmospheric deposition on heavy metal contamination in paddy field systems under different functional areas in ChangZhuTan, Hunan Province, China

In recent decades, the problem of heavy metal contamination in rice paddies has attracted widespread attention. However, most studies on heavy metal contamination in paddy fields are biased towards soil and/or rice plants, without taking atmospheric deposition into account. In this study, atmospheric deposition, paddy soil, and rice samples were collected from three functional areas (area proximity to factories, along the roadside, and suburban) in ChangZhuTan, Hunan Province. The pollution characterization, translocation, and health risk of heavy metals were reassessed. The findings revealed that Cd and As contamination in the study area's soils was more severe, with point exceedance rates reaching 70 % and 35.9 %, respectively. The highest concentrations of As, Ni, Cd, and Pb in atmospheric deposition were found along the roadside, with 1.42 μg/m2/day, 3.21 μg/m2/day, 0.34 μg/m2/day, and 8.28 μg/m2/day, respectively. In area proximity to factories, As and Ni in atmospheric deposition showed to be lowest, whereas Cd and Pb concentrations showed lowest in suburban areas. Furthermore, the accumulation of Cd and Pb in rice grains in regions proximity to factories was significantly higher than in other regions. The human health risk assessment indicated the health risk caused by rice intake in areas proximity to factories was the highest and requires attention, which was mainly due to Cd accumulation, with HQ value reached 3.19. Correlation tests indicate that atmospheric deposition has a positive effect on heavy metal enrichment in rice grains. Further Random Forest analysis revealed that the transport of heavy metals from atmospheric deposition to leaves and shells were important influencing factors for As, Cd, Ni and Mg accumulation in rice grain. Therefore, more attention should be paid to the effects of atmospheric deposition on the accumulation of heavy metals in paddy fields in order to maintain the production safety of crops.

Comparative transcriptome analysis between two different cadmium-accumulating genotypes of soybean (Glycine max) in response to cadmium stress

BackgroundCadmium (Cd) is extremely toxic and non-essential for plants. Different soybean varieties differ greatly in their Cd accumulation ability, but little is known about the underlying molecular mechanisms.ResultsHere, we performed transcriptomic analysis using Illumina pair-end sequencing on root tissues from two soybean varieties (su8, high-Cd-accumulating (HAS) and su7, low Cd-accumulating (LAS)) grown with 0 or 50 μM CdSO4. A total of 18.76 million clean reads from the soybean root samples were obtained after quality assessment and data filtering. After Cd treatment, 739 differentially expressed genes (DEGs; 265 up and 474 down) were found in HAS; however, only 259 DEGs (88 up and 171 down) were found in LAS, and 64 genes were same between the two varieties. Pathway enrichment analysis suggested that after cadmium treatment, the DEGs between LAS and HAS were mainly enriched in glutathione metabolism and plant-pathogen interaction pathways. KEGG analysis showed that phenylalanine metabolism responding to cadmium stress in LAS, while ABC transporters responding to cadmium stress in HAS. Besides we found more differential expressed heavy metal transporters such as ABC transporters and zinc transporters in HAS than LAS, and there were more transcription factors differently expressed in HAS than LAS after cadmium treatment in two soybean varieties, eg. bHLH transcription factor, WRKY transcription factor and ZIP transcription factor.ConclusionsFindings from this study will shed new insights on the underlying molecular mechanisms behind the Cd accumulation in soybean.

Numerical simulation of heavy metal migration in stabilized soils under multi-field coupling

Heavy metal contamination of soils has become a global issue. In pursuit of a reference for the management of heavy metal pollution, numerical simulations were used here to investigate the migration pattern of heavy metals in soil under multi-field coupling of rainfall, temperature, and hydraulic conductivity. Models were built using TOUGHREACT, and measured and simulated values were compared with those of existing studies to verify the accuracy of the software in simulating coupled water vapor-thermal transport and rainfall infiltration. Taking Nanjing rainfall data as an example, the transport pattern of zinc in soil under multi-field coupling was explored. Although evaporation and rainwater infiltration were found to increase with the temperature, the effects of evaporation and temperature counteracted each other, resulting in a weak influence of temperature on heavy metal transport. The hydraulic conductivity of stabilized soil was the main factor controlling zinc migration, with the saturation and heavy metal concentration clouds of soil columns tending to stabilize when the hydraulic conductivity of solidified soil was under 1 × 10-11 m/s.

The chelation mechanism of neonicotinoid insecticides influencing cadmium transport and accumulation in rice at different growth stage

The combined exposure of heavy metals and organic contaminates can influence the transport and accumulation of heavy metals within the soil−rice system. However, the underlying mechanisms of this process remain largely unknown. Herein, this study investigated the influence of three neonicotinoid insecticides (NIs), including imidacloprid (IMI), clothianidin (CLO), and thiamethoxam (THI), on the Cd transport and accumulation in rice (Oryza sativa) at different growth stages. Particular focus lied on their complex interaction and key genes expression involved in Cd transport. Results showed that the interaction between Cd and NIs was the dominant factor affecting Cd transport and accumulation in rice exposed to NIs. All three NIs chelated with Cd with nitrogen (N) on the IMI and THI nitro groups, and the N on the CLO nitro guanidine group. Interestingly, this chelation behavior varied between the tillering stage and the filling/ripening stages, resulting in diverse patterns of Cd accumulation in rice tissues. During the tillering stage, all three NIs considerably inhibited Cd bioavailability and transport to the above-ground part, lowering Cd content in the stem and leaf. The inhibition was increased with stronger chelation ability in the order of IMI (−0.46 eV) > CLO (−0.41 eV) > THI (−0.11 eV), with IMI exhibiting the highest binding energy for Cd and reducing Cd transfers from root to stem by an impressive 94.49 % during the tillering stage. Conversely, during the filling/ripening stages, NIs facilitated Cd accumulation in rice roots, stems, leaves, and grains. This was mainly attributed to the generation of nitrate ions and the release of Cd2+ during the chelation between Cd and NIs under drainage condition. These findings provide theoretical basis for the treatment of combined contamination in field and deep insights into understanding the interaction of organic contaminants with heavy metals in rice culture process.

The Effects of Mine Waste and Rain Water on the Structure of Bacteria Community of Paddy Soils

ABSTRACT Heavy metal contamination of soil has become one of the most important environmental problems worldwide. Heavy metals can affect growth and lead to changes in microbial community composition, which could influence the growth of crops in the soil. In this study, we conducted an experiment to investigate the distribution profile of heavy metals and bacterial communities in soil with the effects of slag and/or water on the top of the soil. Extra heavy metals, acting as selective pressure, led to the loss of sensitive taxa, with tolerant or less sensitive taxa being more abundant in the community. The results showed that the addition of slag on the top of soils did not change the diversity of bacteria but influenced the relative abundance of indigenous members in the community. Water addition, however, improved the homogeneity of the environment vertically in the soil, which consequently led to a lower variation in the bacterial community. This study mimicked the scenario of tailings and abandoned mines in nature, and aimed to study the effects of mines on the soil microbial community with the influence of precipitation on the distribution of heavy metals in the soil. With the effect of precipitation, the transportation of heavy metals in the slag may influence the local bacterial community and subsequently undermine the quality of soil for agriculture. These observations provide evidence of the effects of heavy metals on the soil around abandoned mines without any treatment. Mining causes both heavy metal and water pollution, which may lead to the accumulation of heavy metals in plants and agricultural production. Therefore, it is necessary to take care of tailings with proper procedures instead of exposing them to nature.

Heavy metal accumulation on microplastics in compost - The role of biofilm

Microplastics, small plastic pieces ( microplastics washed with distilled water > compost free from microplastics > chemically separated microplastic > new macro-plastic, with some exceptions. Heavy metal concentrations were significantly higher in samples from Kochi, due to a larger bio-film formation on the plastics as determined by TOC and SEM analyses. The findings of the study highlight the importance of source segregation and prevention of mixing organic waste with plastic waste in MSW, to avoid heavy metal transport in terrestrial environment through microplastics.

The Effects of Heavy Metal Pollution on Soil Nitrogen Transformation and Rice Volatile Organic Compounds under Different Water Management Practices.

One of the most concerning global environmental issues is the pollution of agricultural soils by heavy metals (HMs), especially cadmium, which not only affects human health through Cd-containing foods but also impacts the quality of rice. The soil's nitrification and denitrification processes, coupled with the release of volatile organic compounds by plants, raise substantial concerns. In this review, we summarize the recent literature related to the deleterious effects of Cd on both soil processes related to the N cycle and rice quality, particularly aroma, in different water management practices. Under both continuous flooding (CF) and alternate wetting and drying (AWD) conditions, cadmium has been observed to reduce both the nitrification and denitrification processes. The adverse effects are more pronounced in alternate wetting and drying (AWD) as compared to continuous flooding (CF). Similarly, the alteration in rice aroma is more significant in AWD than in CF. The precise modulation of volatile organic compounds (VOCs) by Cd remains unclear based on the available literature. Nevertheless, HM accumulation is higher in AWD conditions compared to CF, leading to a detrimental impact on volatile organic compounds (VOCs). The literature concludes that AWD practices should be avoided in Cd-contaminated fields to decrease accumulation and maintain the quality of the rice. In the future, rhizospheric engineering and plant biotechnology can be used to decrease the transport of HMs from the soil to the plant's edible parts.

Influence of conditioner and straw on the herbaceous plant-based phytoremediation copper tailings: a field trial at Liujiagou tailings pond, China.

A field trial was performed to carry out an enhanced phytoremediation technique for multi-metal contaminated copper tailings by Sudan grass (Sorghum Sudanese), ryegrass (Lolium perenne L.), and Bermuda grass (Cynodon dactylon), using conditioner (TH-LZ01) and straw combination into composite amendments as soil amendments, aimed to obtain the maximum of phytoremediation effect. The results showed that compared with untreated herbaceous plants, the application of conditioner and straw planted with herbaceous plants reduced the pH and conductivity and increased the organic matter and water content of the copper tailings to different degrees. With the addition of conditioner and straw, the DTPA-Cd, DTPA-Cu, DTPA-Pb, and DTPA-Zn contents in the copper tailings showed a decreasing trend compared with the untreated group. The herbaceous plants were promoted to reduce the percentage contents of acid soluble fractions Cd, Cu, Pb, and Zn and to increase the percentage contents of reducible, oxidizable, and residual fractions heavy metals (Cd, Cu, Pb, and Zn) in the copper tailings to different degrees. The contents of Cd, Cu, Pb, and Zn in the underground part of herbaceous plants were higher than those in the aboveground part, and the contents of Cd, Cu, Pb, and Zn in the aboveground part and underground part decreased after adding conditioner and straw, which indicated that the conditioner and straw inhibited the transport of heavy metals in the plant. Furthermore, the principal component analysis showed that the application of conditioner and straw with planting ryegrass had more potential for improving the physicochemical properties of copper tailings and reducing heavy metal toxicity, followed by Bermuda grass and Sudan grass.

Cysteine and thiosulfate promoted cadmium immobilization in strain G303 by the formation of extracellular CdS

Bacteria have evolved a variety of strategies to defend themselves against cadmium toxicity, however, the specific mechanisms involved in the enhancement of bacterial cadmium resistance by sulfur sources are unclear. In this study, a novel cadmium (Cd)-tolerant bacterium, Stenotrophomonas geniculata G303, was isolated from activated sludge. The growth of strain G303 under diverse Cd concentrations was investigated, and the minimum inhibitory concentration of Cd was found to be 1 mM. Strain G303 effectively remove 94.7 % of Cd after 96 h of culture. Extracellular CdS was detected using multiple methods, with the CdS formed being aggregated in the biofilm. The addition of cysteine and thiosulfate to the medium significantly enhanced the Cd resistance and removal capacity of strain G303. Integrated genomic and proteomic analyses revealed that heavy metal transporters cooperate to resist Cd stress. Cysteine and thiosulfate improved Cd tolerance in strain G303 by upregulating nitrogen and energy metabolism. Proteins associated with nitrate reduction likely played a pivotal role in cysteine and thiosulfate metabolism. Notably, cysteine synthase and the SUF system played crucial roles in CdS formation. This study systematically explored the impact of cysteine and thiosulfate on the Cd resistance of strain G303, deepening our understanding of the microbial response mechanism to heavy metals.

Heavy metals in centralized drinking water sources of the Yangtze River: A comprehensive study from a basin-wide perspective

Water quality in the Yangtze River Basin (YRB) has received considerable attention because it supplies water to 400 million people. However, the trends, sources, and risks associated with heavy metals (HMs) in water of centralized drinking water sources (CDWSs) in the YRB region are not well understood due to the lack of high-frequency, large-scale monitoring data. Moreover, research on the factors affecting the transportation of HMs in natural water are limited, all of which significantly reduce the effectiveness of CDWSs management. Therefore, this study utilized data on 11 HMs and water quality from 114 CDWSs, covering 71 prefecture-level cities (PLC) in 15 provinces (cities), to map unprecedented geospatial distribution of HMs in the YRB region and examine their concentrations in relation to water chemistry parameters. The findings revealed that the frequency of detection (FOD) of 11 HMs ranged from 28.59% (Hg) to 99.64% (Ba). The mean concentrations are ranked as follows: Ba (40.775 μg/L) > B (21.866 μg/L) > Zn (5.133 μg/L) > V (2.668 μg/L) > Cu (2.049 μg/L) > As (1.989 μg/L) > Mo (1.505 μg/L) > Ni (1.108 μg/L) > Sb (0.613 μg/L) > Pb (0.553 μg/L) > Hg (0.002 μg/L). Concentrations of Zn, As, Hg, Pb, Mo, Sb, Ni, and Ba exhibited decreasing trends from 2018 to 2022. Human activities, including industrial and agricultural production, have led to higher pollution levels in the midstream and downstream of the river than in its upstream. Additionally, the high concentrations of Ba and B are influenced by natural geological factors. Anion concentrations and nutrient levels, play a significant role in the transport of HMs in water. Probabilistic health risk assessment indicates that As, Ba, and Sb pose a potential carcinogenic risk. Additionally, non-carcinogenic risk to children under extreme conditions should also be considered.

Migration patterns of heavy metals from solid waste stockpile soils by native plants for ecological restoration in arid and semi-arid regions of Northwest China

Ecological remediation with native plants is the main measure to control the pollution of solid waste in Northwest China. However, the heavy metal transport characteristics of these native plants are still unidentified. This study analyzed the distribution of 16 heavy metals in native plants in the desulfurization gypsum yard (DGY), the gangue yard (GY) and the fly ash yard (FAY). The results showed that the soil contained many heavy metals in high concentrations. For instance, As concentrations were comparable to the global soil background values, whereas Cr and Mn concentrations in the area were 2–3 times greater than the global soil background values. The content of heavy metals in the plant root system increased first, then decreased as the distance from the yard increased. Ni, Pb, and Cd migrated well in Artemisia frigida Willd and Artemisia sieversiana Ehrhart ex Willd, with A. sieversiana showing a particularly strong migration in GY. A. sieversiana, on the other hand, was more successful at migrating Cd at DGY and had a similar capability for Mg migration in all three locations. Festuca rubra L was potentially suitable for planting in GY for Ni removal. In conclusion, the migration patterns of different heavy metals were not alike for plants in the three landfills. The results provided a basis for plant selection for ecological restoration in arid and semi-arid regions.