Metal Contamination Research Articles

Assessment of Heavy Metal Contamination and Ecological Risk in Soil within the Zheng–Bian–Luo Urban Agglomeration

As urbanization accelerates, the contamination of urban soil and the consequent health implications stemming from urban expansion are increasingly salient. In recent years, a plethora of cities and regions nationwide have embarked on rigorous soil geological surveys with a focus on environmental quality, yielding invaluable foundational data. This research aims to develop scientifically robust and rational land-use planning strategies while assessing the levels of heavy metal pollution and associated risks. The urban agglomeration encompassing Zhengzhou, Luoyang, and Kaifeng (referred to as Zheng–Bian–Luo Urban Agglomeration) in Henan Province was designated as the study area. Leveraging the Nemerow comprehensive index method alongside the Hakanson potential ecological risk assessment method, this study delved into the pollution levels and potential ecological ramifications of nine heavy metals, namely Cr, Mn, Ni, Cu, Zn, As, Cd, Pb, and Co. Research indicates that the hierarchy of individual potential ecological risks ranges from most to least significant as follows: Cd > Pb > Cr > Ni > Cu > Zn > As > Mn > Co. The concentrations of Cd in both Zhengzhou and Kaifeng surpassed the established background levels. Furthermore, the mean single-factor pollution index values for the heavy metals Cd and Zn exceeded 1, signifying a state of minor pollution. The Nemerow comprehensive index P of Cd and Zn is between 1 < Pcomp ≤ 2, which is considered mild pollution. The comprehensive P values of the other seven metal elements are all less than 0.7, reaching a clean (alert) level. Predominantly, the primary potential risk factor in the superficial soil of the Zheng–Bian–Luo urban agglomeration is Cd, while the ecological risk implications associated with other heavy metal elements are comparatively minimal. The soil environmental quality within the designated study area remains secure, although certain localized areas pose potential risks of heavy metal pollution. A comprehensive assessment of the current state of soil heavy metal pollution is essential to establish a theoretical foundation and provide technical support for soil environmental protection, pollution mitigation, and sustainable utilization.

Assessing the Ecological Risks and Spatial Distribution of Heavy Metal Contamination at Solid Waste Dumpsites

Assessing the Ecological Risks and Spatial Distribution of Heavy Metal Contamination at Solid Waste Dumpsites

Heavy Metals In Bivalves From Coastal Municipalities Of C apiz,P hilippines

This research study is based on the current status of heavy metal contamination in bivalves within the coastal areas of Capiz, Philippines, drawing insights from accessible data. The findings shed light on the contamination’s extent, potential threats to human health, and the pollution’s origins. The researchers acknowledge the study’s limitations. As per the findings, elevated levels of heavy metals, such as lead, mercury, cadmium, arsenic, and chromium, in bivalves collected from Capiz’s coastal regions. Variations in metal concentrations are observed among different bivalve species and sampling sites, with identified geographical distribution patterns and potential contamination hotspots. An assessment of conformity to regulatory limits and guidance for heavy metal levels in shellfish consumption is conducted, identifying any exceedances or areas of concern. The research aims to establish the extent to which bivalves from Capiz aligns with legal requirements. Potential health risks allied to the bivalve consumption are evaluated based on the detected heavy metal levels, considering various exposure routes, population characteristics, and toxicity reference values. The research scrutinizes the impact of human activities, including industrial discharges, agricultural practices, and urban runoff, on heavy metal contamination in coastal ecosystems. The ongoing discussion underscores the need for further investigation and underscores the importance of addressing the issue to ensure the environmental sustainability and safety of coastal resources in Capiz.

LCMS-Metabolomic Profiling and Genome Mining of Delftia lacustris DSM 21246 Revealed Lipophilic Delftibactin Metallophores.

Bacteria have evolved various strategies to combat heavy metal stress, including the secretion of small molecules, known as metallophores. These molecules hold a potential role in the mitigation of toxic metal contamination from the environment (bioremediation). Herein, we employed combined comparative metabolomic and genomic analyses to study the metallophores excreted by Delftia lacustris DSM 21246. LCMS-metabolomic analysis of this bacterium cultured under iron limitation led to a suite of lipophilic metallophores exclusively secreted in response to iron starvation. Additionally, we conducted genome sequencing of the DSM 21246 strain using nanopore sequencing technology and employed antiSMASH to mine the genome, leading to the identification of a biosynthetic gene cluster (BGC) matching the known BGC responsible for delftibactin A production. The isolated suite of amphiphilic metallophores, termed delftibactins C-F (1-4), was characterized using various chromatographic, spectroscopic, and bioinformatic techniques. The planar structure of these compounds was elucidated through 1D and 2D NMR analyses, as well as LCMS/MS-based fragmentation studies. Notably, their structures differed from previously known delftibactins due to the presence of a lipid tail. Marfey's and bioinformatic analyses were employed to determine the absolute configuration of the peptide scaffold. Delftibactin A, a previously identified metallophore, has exhibited a gold biomineralizing property; compound 1 was tested for and also demonstrated this property.

Microbiologically induced calcite precipitation (MICP) in situ remediated heavy metal contamination in sludge nutrient soil

Microbiologically induced calcite precipitation (MICP), as a newly developing bioremediation technology, could redeem heavy metal contamination in diverse scenarios. In this study, MICP bacterium Sporosarcina ureilytica ML-2 was employed to suppress the pollution of Pb, Cd and Zn in municipal sludge nutrient soil. After MICP remediation, the exchangeable Cd and Zn in sludge nutrient soil were correspondingly reduced by 31.02 % and 6.09 %, while the carbonate-bound Pb, Cd and Zn as well as the residual fractions were increased by 16.12 %, 6.63 %, 13.09 % and 6.10 %, 45.70 %, 3.86 %, respectively. In addition, the extractable Pb, Cd and Zn either by diethylenetriaminepentaacetic acid (DTPA) or toxicity characteristic leaching procedure (TCLP) in sludge nutrient soil were significantly reduced. These results demonstrated that the bio-calcite generated via MICP helped to immobilize heavy metals. Furthermore, MICP treatment improved the abundance of functional microorganisms related to urea cycle, while reduced the overall abundance of metal resistance genes (MRGs) and antibiotic resistance genes (ARGs). This work confirmed the feasibility of MICP in remediation of heavy metal in sludge nutrient soil, which expanded the application field of MICP and provided a promising way for heavy metal pollution management.

Pistia Stratiotes based heavy metals phytoremediation of a Himalayan river impacted by hydroelectric plant in an Indo Burma hotspot region

ABSTRACT Present study attempts to study the impact of Serlui-B hydroelectric dam on water quality (‘water-energy nexus’) of a Himalayan river and to devise possible phytotechnology for heavy metals remediation. Physico-chemical characteristics of water were analyzed using ‘American Public Health Association (APHA)’ methods while Atomic Absorption Spectrophotometer (AAS) was used for estimation of heavy metals. To this end, concentrations of Fe and Ni were recorded above permissible limit which can impose public health risks. Therefore, phytoremediation experiments were performed by using Pistia stratiotes L. (water lettuce) and effects of Fe and Ni concentrations (1.0, 2.0, and 5.0 mg/L) on photosynthetic pigments were observed. Phytoremediation investigations using 24 aquaria (of 40.5 L) revealed that P. stratiotes was an effective hyperaccumulator of Fe and Ni with maximum removal efficiency of 96.2% and 92%, respectively. In relation to bioaccumulation indices, the bioconcentration factor (BCF) values decreased with increase in Fe and Ni concentrations, whereas the translocation factor (TF) was noted higher at low concentrations and vice versa. Furthermore, the total chlorophyll content and carotenoid levels in P. stratiotes demonstrated negative significant correlation with the rise in Fe/Ni concentrations that may be considered as an adaptive biochemical strategy to mitigate metals induced oxidative stress. The present study can further be extrapolated to field phytoremediation for ameliorating both physico-chemical and metallic contaminants. Last, the role of microbial biodiversity associated with P. stratiotes should be elucidated in future to help achieve SDG 6 and environmental sustainability.

Characteristics of Secang Jelly Drink as Functional Drink with the Addition of Red Ginger Extract for Antioxidant Source

Secang wood (Caesalpinia sappan L.) and red ginger can be used as alternative functional drinks in form of jelly drinks, due to the antioxidant properties contained in these two ingredients. In this study, we wanted to know the characteristics of secang jelly drinks with addition of red ginger extract at various concentrations. The research was conducted with ginger extract concentrations of 20% (J1), 25% (J2), 30% (J3), 35% (J4), and 40% (J5) executed completely random. The results of the research regarding the characteristics of secang jelly drink with the addition of red ginger extract have significant differences (p<0.05) for viscosity, pH value, antioxidant activity, and sensory as well as hedonic quality. The best treatment is obtained from red ginger extract concentration of 35% with an average viscosity of 986.7 cP, pH of 4.47, antioxidant activity with an IC50 value of 72.97 (strong), sensory score for aroma, texture, and taste is 5, hedonic quality score for aroma, texture, and taste is 4. This treatment also results in average total flavonoid content of 24.29 mg/100 g. No heavy metal contamination was found and total plate number was <102 colonies/mL. Keywords: Antioxidant, Functional drink, Jelly drink, red ginger, Secang woods.

Glutathione-Mediated Metal Tolerance in an Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis).

The spread of the amphibian chytrid fungus Batrachochytrium dendrobatidis, which causes the disease chytridiomycosis, has resulted in amphibian declines and extinctions worldwide. Some susceptible amphibian species can persist in contaminated habitats, prompting the hypothesis that B. dendrobatidis might be sensitive to heavy metals. We tested a panel of 12 metals to rank their toxicity to B. dendrobatidis zoospores and zoosporangia during a 6-h exposure. To better understand the mechanism for metal detoxification, we also evaluated whether glutathione is required for metal tolerance by depleting cellular glutathione before metal exposure. In addition, we investigated whether prior exposure to low metal concentrations impacted tolerance of subsequent exposure, as well as identifying metal combinations that may act synergistically. Silver (Ag), cadmium (Cd), and copper (Cu) were particularly toxic to B. dendrobatidis, with zoospore minimum lethal concentration values of 0.01 mM (Ag), 0.025 mM (Cd), and 0.5 mM (Cu). These three metals along with zinc (Zn) were also inhibitory to zoosporangia, with minimum inhibitory concentration values of 0.005 mM (Ag), 0.04 mM (Cd), 0.075 mM (Cu), and 0.04 mM (Zn). The fungicidal effects of several metals was reduced when assays were conducted in nutrient medium compared with synthetic pond water, highlighting the need for careful in vitro assay design and interpretation. Glutathione depletion strongly influenced tolerance of Cd and Ag (85% and 75% less growth, respectively) and moderately influenced tolerance of Cu, Zn, and lead (37%, 18%, and 14% less growth, respectively), indicating the importance of glutathione for metal detoxification. In general, the minimum metal concentrations that inhibited growth of B. dendrobatidis far exceeded values detected in contaminated amphibian habitats in Australia, suggesting that metal contamination alone may not have a strong protective effect against chytridiomycosis. We discuss future research directions to futher understand the potential for dissolved metals to create chytrid refuges. Environ Toxicol Chem 2024;43:1583-1591. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Contamination Status of Residential and Farmland Surface Soils Within the Sunyani Municipality of Ghana

Exposure to heavy metals poses serious human health and ecological threats, especially in developing countries where ecological risk assessment and remediation are often ignored. While many studies have reported heavy metal toxicities in rapidly urbanizing cities with increased anthropogenic activities, limited information exists on metal toxicities and their ecological risks in soils within the Sunyani Municipality. Top soils were sampled from residential and farmland surface soils and analyzed for the concentration and potential risks for nine heavy metals within Sunyani Municipality. Apart from As and Mn, the two study sites generally recorded elevated levels of all metals than the pristine soil samples from the University of Energy and Natural Resources botanical garden. Levels of chromium, copper, lead, and zinc were however marginally higher in residential surface soils than in the farmlands. The soil contamination factor and geoaccumulation index both revealed moderate As, Hg, and Mn contamination at the two study locations. Furthermore, the soil enrichment factor showed significant enrichment for arsenic and moderate enrichment for cadmium in residential soils, while the farmland soils revealed moderate enrichment of As, Hg, and Mn. The potential ecological risk indices also showed considerable risk at both study locations, while the pollution load index revealed higher cumulative pollution in residential areas (PLI = 0.48) compared to the farmland surface soil (PLI = 0.40). The study therefore recommends the regulation of human activities and the use of chemicals that are possible sources of metal contamination to maintain the metals’ baseline levels in the soil, and reduce their health and environmental impacts.

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.

Effect of domestic heat processing techniques on the trace metals concentration in imported frozen fish products in Bayelsa State, Nigeria, and health risk assessment

IntroductionTrace metals in fish play different important roles, both for the fish itself and humans who consume them. However, some of these metals are toxic at low concentrations, and are considered as health hazards. In this study, the concentration of six trace metals (Pb, Cd, Ni, Cu, Mn and Zn) were determined in imported frozen fish species available in Bayelsa State, Nigeria. The effect of domestic heat processing techniques (cooking, frying and smoking) on the trace metals concentration, and the potential risk due to consumption of these metals in fish were also evaluated. MethodsSix different species of imported frozen fish species were purchased from wholesale and retail outlets, and were prepared as raw, cooked, fried and smoked samples. A mixture of acids was used for digestion of fish samples, while Flame atomic absorption spectrometer was used for quantification of metals. The hazard index was employed for evaluating the non-carcinogenic risk of metals in fish. ResultsThe average trace metals concentration in the raw fish samples followed the order: Zn > Cu > Cd > Ni > Mn. Pb was undetected in all fish samples. The concentration of the detected trace metals ranged as follows - Cd: 3.45–9.40 mg/kg, Ni: <0.001–13.13 mg/kg, Cu: 6.10–9.95 mg/kg, Mn: <0.001–1.05 mg/kg, and Zn: 14.50–43.65 mg/kg. The Cd concentration in all raw fish species greatly exceeded its permissible limits. The effect of domestic heat processing techniques on trace metals concentration in fish did not follow any regular pattern, and only Cd concentrations exceeded its permissible limit in all heat processed fish samples. The hazard quotient (HQ) values showed that only Cd had HQ values >1 for both child and adult exposure scenarios. ConclusionThe results suggest trace metal contamination of fish samples by Cd, with significant potential non-carcinogenic risk. Since Cd is toxic, continuous screening of imported fish products is necessary, in order to safeguard public health.

Modeling risk assessment of soil heavy metal pollution using partial least squares and fuzzy logic: A case study of a gully type coal-based solid waste dumpsite

Continuous release and migration of heavy metals from coal-based solid waste (CSW) dumpsites often results in significant encroachment on ecological lands and pollution of natural environments. As a result, there is an urgent need for long-term and rapid monitoring, analysis, and assessment to control environmental risks associated with large CSW dumpsites. We constructed a new composite model (PLS-FL) that uses partial least squares regression (PLSR) and fuzzy logic inference (FLI) to accurately predict heavy metal concentrations in soils and assess pollution risk levels. The potential application of the PLS-FL was tested through a gully type CSW case study. We compared 20 modeling strategies using the PLS-FL: five types heavy metals (Cd, Zn, Pb, Cr and As) * four spectral transformation methods (first derivative (FD), second derivative (SD), reverse logarithm (RL), and continuum removal (CR)) * one variable selection method (competitive adaptive reweighted sampling (CARS)). The results showed that the combination of derivative transformation and CARS was recommended for estimation, with R2C > 0.80 and R2P > 0.50. When comparing the PLSR model with four traditional machine learning methods (Support Vector Machines (SVM), Random Forests (RF), Extreme Learning Machines (ELM), and KNN), the PLSR model demonstrated the highest average prediction accuracy. Additionally, the FLI process no longer relies on human perception and expert opinion, enhancing the model's objectivity and reliability. The evaluation results revealed that the heavy metal contamination areas of the CSW dumpsite are concentrated at the bottom of the gully, with more severe contamination in the north. Furthermore, a high-risk zone exists in the interim storage area for CSW to the east of the dump. These findings align with the initial detections at the sampling sites and highlight the need for targeted monitoring and control in these areas. The application of the model will empower regulators to quickly assess the overall situation of large-scale heavy metal pollution and provide scientific program and data support for continuous large-scale pollution risk monitoring and sustainable risk management.

Bacterial-fungal interactions and response to heavy metal contamination of soil in agricultural areas.

Long-term heavy metal contamination of soil affects the structure and function of microbial communities. The aim of our study was to investigate the effect of soil heavy metal contamination on microorganisms and the impact of different heavy metal pollution levels on the microbial interactions. We collected soil samples and determined soil properties. Microbial diversity was analyzed in two groups of samples using high-throughput sequencing technology. Additionally, we constructed microbial networks to analyze microbial interactions. The pollution load index (PLI) < 1 indicates that the area is not polluted. 1 < PLI < 2 represents moderate pollution. PLI was 1.05 and 0.14 for the heavy metal contaminated area and the uncontaminated area, respectively. Cd, Hg, Pb, Zn, and Cu were identified as the major contaminants in the contaminated area, with the contamination factors were 30.35, 11.26, 5.46, 5.19, and 2.46, respectively. The diversities and compositions of the bacterial community varied significantly between the two groups. Compared to the uncontaminated area, the co-occurrence network between bacterial and fungal species in the contaminated area was more complex. The keystone taxa of the co-occurrence network in the contaminated area were more than those in the uncontaminated area and were completely different from it. Heavy metal concentrations played a crucial role in shaping the difference in microbial community compositions. Microorganisms adapt to long-term and moderate levels of heavy metal contamination through enhanced interactions. Bacteria resistant to heavy metal concentrations may play an important role in soils contaminated with moderate levels of heavy metals over long periods of time.

Assessment of three different approaches for integrating phosphorus recovery from sewage sludge and derived products in existing wastewater treatment plants

Three different technological solutions, namely acidogenic fermentation and chemical extraction (alkaline or acidic), followed by precipitation with 1% Ca(OH)2, were investigated in the view of integrating phosphorus recovery into existing wastewater treatment plants. Experiments were conducted at the lab-scale using (i) sludge taken from biologically and chemically promoted phosphorus removal activated sludge processes and (ii) ashes obtained from sludge muffle incineration. Results highlighted the benefits of enhanced biological phosphorus removal (EBPR) systems rather than chemically promoted phosphorus removal in not only phosphorus extraction (up to 40% with EBPR) and recovery directly from secondary sludge (P precipitation between 66 and 92%), but after sludge incineration as well (P extraction up to 96% and precipitation above 96%). Acidogenic fermentation ensured the highest phosphorus release from EBPR sludge (equal to a concentration in solution of 122 mg/L P-PO43−), while the derived ashes had a lower level of metal contamination (particularly Fe and Al content < 2%). The phosphorus-rich product obtained by means of the recovery process showed relevant metal contamination (Cu, Zn, and Ni) under some operating conditions, suggesting the need for further treatments.

Synergistic effect on simultaneous treatment of Cr(VI) and chloramphenicol using a non-thermal plasma technology

Toxic organic and heavy metal contaminants commonly exist in industrial waste stream(s) and treatment is of great challenge. In this study, a dielectric barrier discharge (DBD) non-thermal plasma technology was employed for the simultaneous treatment of two important contaminants, chloramphenicol (CAP) and Cr(VI) in an aqueous solution through redox transformations. More than 70% of CAP and 20% of TOC were degraded in 60 min, while Cr(VI) was completely removed in 10 min. The hydroxyl radicals were the main active species for the degradation. Meanwhile, the consumption of hydroxyl radicals was beneficial to the reduction of Cr(VI). The synergistic effect was investigated between CAP degradation and Cr(VI) reduction. The reduction of Cr(VI) would be enhanced in the presence of CAP with a low concentration and could be inhibited under a high concentration, because part of hydroxyl radicals could be consumed by the low-concentration CAP and the obtained intermediates with a higher kinetic rate. However, CAP with a high concentration could react with such reductive species as eaq− and •H, which could compete with Cr(VI) and inhibit the reduction. In addition, the presence of Cr(VI) enhanced the degradation and mineralization of CAP; the study of obtained intermediates indicated that the presence of Cr(VI) changed the degradation path of CAP as Cr(VI) would react with reductive species, enhance the generation of hydroxyl radicals, and cause more hydroxylation reactions. Moreover, the mechanism for the simultaneous redox transformations of CAP and Cr(VI) was illustrated. This study indicates that the DBD non-thermal plasma technology can be one of better solutions for simultaneous elimination of heavy metal and organic contaminants in aquatic environments.

Carbon shell derived from bottle waste PET on α-Fe2O3/Fe3O4 heterostructure core as synergetic Fenton-like catalyst for degradation of antibiotics

In this work, two approaches to environmental sustainability have been followed including the synthesis of an efficient and easily recyclable catalyst for Fenton-like degradation of antibiotics from water, and the upcycling of waste polyethylene terephthalate (PET) into the value-added product through a feasible procedure. For this purpose, the Fe2O3/Fe3O4 mixture coated by the carbon layer derived from the bottle waste PET was synthesized for boosting the Fe3+/Fe2+ cycle in the Fenton-like reaction. The FeCl3 can act as a catalyst for graphitization process and also the precursor of metal oxide nanoparticles. The catalytic efficiency was evaluated for the degradation reaction of amoxicillin and azithromycin antibiotics. Complete conversion of amoxicillin and azithromycin (15 mg/L) was observed in the presence of 5 µL of H2O2, at pH=3 for 30 min. Also, the mineralization of amoxicillin and azithromycin was evaluated by TOC analysis, which was obtained as 77 and 89 %, respectively. The high activity of the catalyst can be attributed to the presence of a mixture of iron oxide nanoparticles for the catalysis of Fenton-like reactions and activation of H2O2, as well as the coating of nanoparticles with a carbon layer to stabilize and prevent metal leakage and contamination of the mixture. In addition, due to the good electrical conductivity of carbon layer, it can act as electron donors to enhance Fe3+ reduction.

Development of a new series of thioacetal based fluorescence chemosensors for highly sensitive determination of Hg2+ in environmental samples and cell imaging

Mercury ion is one of the most harmful metal ions with significant hazards to the environment and human health. Thus, the development of innovative, sensitive, and selective sensors to help address the detrimental impacts of heavy metal contamination is necessary. In this work, we present three new chemosensors based on the deprotection reaction of the thioacetal group for distinguishing Hg2+ in environmental samples. These chemosensors show good photophysical properties with high quantum yield in aqueous medium. These prepared chemosensors were employed as fluorometric sensors for the determination of Hg2+ through the quenching of fluorescence emission due to the Hg2+-induced hydrolysis of the thioacetal to the aldehyde group. In the presence of Hg2+, chemosensors showed an emissive color transformation from blue fluorescence to non-fluorescence under UV light, which was readily seen by the visual eye. These chemosensors also exhibited highly distinctive selectivity toward Hg2+ over other interfering metal ions, with detection limits of 1.1 ppb, 13.4 ppb, and 12.7 ppb. Moreover, the practical applicability of chemosensor was successfully demonstrated in real water samples and herb extract samples.

Adsorption Potential, Speciation Transformation, and Risk Assessment of Hg-, Cd-, and Pb-Contaminated Soils Using Biochar in Combination with Potassium Dihydrogen Phosphate.

The objective of this study is to develop a remediation technology for composited heavy metal-contaminated soil. Biochars (BC300, BC400, and BC500) derived from corn were combined with potassium dihydrogen phosphate (KH2PO4) to immobilize and remove heavy metal ions, including mercury (Hg2+), cadmium (Cd2+), and lead (Pb2+). The adsorption kinetics of metal ions in aqueous solutions with different concentrations was tested, and the fitting effects of the two models were compared. The findings demonstrate that the joint application of biochar and KH2PO4 could markedly enhance the immobilization efficacy of Pb2+, whereas the utilization of KH2PO4 on its own exhibited a more pronounced immobilization impact on Cd2+. Furthermore, the present study underscores the shortcomings of various remediation techniques that must be taken into account when addressing heavy metal-contaminated soils. It also emphasizes the value of comprehensive remediation techniques that integrate multiple remediation agents. This study offers a novel approach and methodology for addressing the intricate and evolving challenges posed by heavy metal contamination in soil. Its practical value and potential for application are significant.

Deep dewatering of sludge and resource recovery of hydroxyapatite: A recyclable approach via ionic liquid biphasic system and hydrogen bonds reformation

Deep dewatering of Waste Activated Sludge (WAS) through mechanical processes remains inefficient, primarily due to the formation of a stable hydrogen bonding network between the biopolymers and water, which consequently leads to significant water trapped by Extracellular Polymeric Substances (EPS). In this study, a novel and recyclable treatment for WAS based on Ionic Liquids (ILs) was established, named IL-biphasic aqueous system (IL-ABS) treatment. Specifically, the IL-ABS formed in WAS facilitated rapid and efficient in-situ deep dewatering while concurrently recovering hydroxyapatite. The water content decreased from an initial 98.27 % to 65.35 % with IL-ABS, formed by 1-Butyl-3-methylimidazolium bromide (BmimBr) and K3PO4 synthesized from waste H3PO4. Moreover, the recycled BmimBr maintaining the water content of the dewatered sludge consistently between 65.61 % and 67.25 % across five cycles, exhibited remarkable reproducibility. Through three-dimensional excitation-emission matrix, lactate dehydrogenase analyses and confocal laser scanning microscopy, the high concentration of BmimBr in the upper phase effectively disrupted the cells and EPS, which exposed protein and polysaccharide on the EPS surface. Subsequently, the K3PO4 in the lower phase led to an enhanced salting-out effect in WAS. Furthermore, FT-IR analysis revealed that K3PO4 disrupted the original hydrogen bonds between EPS and water. Then, BmimBr formed numerous hydrogen bonds with the sludge flocs, leading to deep dewatering and agglomeration of the sludge flocs during the unique phase separation process of IL-ABS. Notably, sludge-derived hydroxyapatite product exhibited remarkable adsorption capacity for prevalent heavy metal contaminants such as Pb2+, Cd2+ and Cu2+, with efficiencies comparable to those of commercial hydroxyapatite, thereby achieving the resource utilization of waste H3PO4. Moreover, economic calculations demonstrated the suitability of this novel treatment. This innovative treatment exhibits potential for practical applications in the non-mechanical deep dewatering of WAS.

Influencing Factors, Risk Assessment, and Source Identification of Heavy Metals in Purple Soil in the Eastern Region of Guang’an City, Sichuan Province, China

Soil heavy metal contamination poses a significant threat to both environmental health and ecological safety. To investigate the influencing factors, ecological hazards, and sources analysis of heavy metals in purple soil, 27 sets of soil samples were collected from varying genetic horizons within Guang’an City, and the contents of As, Cd, Cu, Cr, Hg, Ni, Pb, and Zn were analyzed. The results indicated higher concentrations of heavy metals in soil A horizon, compared to that of C horizon. The relevance analysis indicated that the soil’s heavy metals were strongly correlated with the soil’s physicochemical properties. The enrichment factor, pollution load index, and potential risk index highlighted slightly to severely polluted levels of soil Cd and Hg, which significantly contribute to the ecological hazards posed by soil heavy metals. The potential source of heavy metals analyzed using the APCS-MLR model identified both anthropogenic inputs and natural sources as primary contributors to heavy metal presence in soils. The Cu, Cr, Ni, Pb, and Zn contents in the samples from different genetic horizons were chiefly influenced by natural sources, such as soil matrix erosion and weathering, while the concentrations of Cd and Hg were largely affected by anthropogenic activities, specifically coal combustion and agriculture. Conversely, the As content was found to be influenced by a combination of both factors. Anthropogenic activities greatly impacted soil heavy metals at various depths within the study area, thereby underscoring the importance of monitoring these heavy metals. The findings gained from this research can give a scientific basis for the potential utilization of purple soil.