Heavy Metals Cr Research Articles

Influence of vegetation on heavy metal Cr release process from bottom sediment under unidirectional flows and regular waves

As human activities become more intensive, a substantial number of heavy metals are discharged into estuarine or wetland environments. Due to the poor degradability, heavy metals are prone to adsorption and deposition on suspended particles in bottom sediments. Subsequently, under the influence of disturbances, there is a potential for their re-release, causing secondary pollution. To investigate the release process of the heavy metal Cr from sediment, laboratory experiments were conducted under both unidirectional flow and regular wave conditions. At the initial stage, the temporal trends of particulate (CrP) and dissolved (CrD) Chromium concentrations were both characterized by initial increments followed by stabilization and continuous escalation. Vertically, the stable concentrations of CrP and CrD increased with the presence of vegetation and the enhancement of hydrodynamics. The Elovich equation, pseudo-second-order kinetic equation, Double constant equation (Freundlich model), and parabolic diffusion equation were employed to predict the release process of CrD from bottom sediment. The Elovich equation proved most suitable for describing the release process of CrD, with an R2 exceeding 0.9. In order to assess the influence of vegetation on the Cr release process, the Stem-Reynolds were introduced to modify the Elovich equation. The final maximum error was 12 % (excluding the initial stage), which was much lower than that using the original Elovich equation (maximum error of 32 %). The study findings provide practical support for estuarine and wetland managers to formulate effective heavy metal management measures, which contribute to the conservation and sustainable management of aquatic ecosystems.

Estimation of heavy metals in sediments and aquatic plant species in two rivers of Punjab, Pakistan

This research highlights the distribution of heavy metals (Ni, Cu, Zn, Cr, Co and Mn) in Ravi and Chenab and assesses their effect on ecosystem health. Samples of plant species and sediments at eight sampling sites were collected and analysed by the PIXE technique. Heavy metal concentrations (µg/g) of Zn (7.98–411.23), Ni (12.59–209), Cu (3.74–38.77) and Mn (0–730.21) in river Ravi and concentrations of Zn (49.32–274.30), Ni (1.05–141.21) and Mn (41.66–519.47) in river Chenab were found to be high but Heavy metal concentration in the two compartments were in the following order plants > sediments. Heavy metals of sediments and plants depict that there are significant correlations between Cu (0.994), Zn (0.986) and Cr (0.978) in river Ravi and Ni (1.000), Zn (.990) and Cr (.978) in river Chenab. The results show the potential of heavy metals from plants in two rivers of Pakistan.

Pollution assessment and index properties of Okpulor soils, Rivers State, Nigeria: geochemical characterization, geotechnical and geoenvironmental implications

This study assessed soil pollution and index properties in Okpulor through geochemical, geotechnical, and geoenvironmental analyses. Twenty samples, comprising 14 surface and 6 shallow subsurface ones, underwent geochemical analysis for heavy metals (Fe, Cr, Cu, Zn, Ni, and Pb). Five geochemical indices, including the Geoaccumulation Index (Igeo), Enrichment Factor (EF), Contamination Factor (CF), Metal Pollution Index (MPI), and Potential Ecological Risk Index (PERI), were utilized. Simultaneously, six subsurface samples underwent geotechnical analysis for Natural Moisture, Grain Size, Specific Gravity, Bulk Density, and Atterberg Limits, following Unified Soil Classification System (USCS) and American Association of State Highway and Transportation Officials (AASHTO) guidelines. The Igeo highlighted significant heavy metal contamination in Okpulor soils, particularly Cd. EF values exceeding 1.5 underscored a strong anthropogenic influence, with CF indicating Cd's substantial contribution to overall contamination. PERI underscored the ecological risks associated with Cd contamination. Natural moisture content, ranging from 18.21% to 21.45%, indicated a notable presence of water in the soil during the dry season, potentially leading to increased leaching and migration of water-soluble contaminants. Bulk density values suggested moderate to lightly packed soils, impacting porosity and permeability, and influencing contaminant movement. Atterberg limits indicated low soil plasticity, impacting moisture retention and contaminant behaviour. Grain size analysis revealed poorly graded soils with a close sand-to-clay ratio, affecting water drainage. These geotechnical properties and heavy metal contamination reveal the intricate interplay between soil characteristics and contamination risks in the Okpulor area, emphasizing the need for targeted interventions to safeguard the environment.

Assessment of metals and metalloids agglutinated to airborne suspended particulate matter in selected plant species during the pre-and post-monsoon in the urban area

The elemental accumulation has emerged as a major environmental concern due to various anthropogenic sources such as vehicles, road dust, and industrial activities, contributing to the agglutination of elements to airborne Suspended Particulate Matter (SPM). SPM-bound elements accumulate on plant surfaces impact air quality and human health due to their noxiousness. Therefore, plants' ability to capture and mitigate air pollutants plays a crucial role in urban areas. This study aimed to investigate the levels and distribution of twenty-six elements, comprised of heavy metals (Cd, Pb, Cr, Cu Zn, Co, Ni, Fe, Mn, Ag, Mo, V, Ga, and Bi), light metals (B, As, Te, and Se), and metalloids (Al, Li, Sr, K, Mg, Na, Ca, and Ba) accumulated on the surface and inside the leaves of dominant plant species during the pre-and post-monsoon at six categorized (commercial, traffic-prone, residential, educational, greenbelt and industrial areas) locations in Delhi, India. In addition, the Metal Accumulation Index (MAI) was determined, and the statistical analysis was conducted using two-way ANOVA, Principal Component Analysis (PCA), and Hierarchical Cluster Analysis (HCA). In the pre-and post-monsoon, two-way ANOVA revealed significant differences (P < 0.05) in metal concentrations. During the pre-monsoon plants exhibited the highest metal accumulation (∼21%) at the Anand Vihar (commercial) in Delhi, with the maximum average concentrations of Cr (118.25 mg/kg), Cu (204.38 mg/kg), Zn (293.27 mg/kg), and Fe (2721.17 mg/kg). Ficus benghalensis L exhibited the maximum 213.73 MAI at the Anand Vihar in the pre-monsoon. Ni and Cr indicated the highest correlation (P < 0.05, r = 0.82) in the PCA test. HCA test revealed similarity (∼87.7%) at ITO (traffic-prone) and Okhla Phase-2 (industrial) in F. religiosa regarding metal concentration patterns. Findings highlighted seasonal elemental pollutants uptake dynamics of plant species and explored species-specific metal accumulation, revealing potential implications of metal-tolerant plants for urban greenbelt.

Performance of the silica adsorbent from snake fruit peel for removing heavy metals of Ag, Cu, Mn, and Cr in SCW

Silver crafts wastewater (SCW) typically contains environmentally harmful heavy metals, including Ag, Cu, Mn, and Cr, necessitating treatment before disposal. This study explores a promising solution using silica (SiO2) adsorbents derived from snake fruit peel through acidic activation with HCl concentrations of 2, 4, and 6 M. Qualitative analysis of the adsorbent involved Fourier-transform infrared spectrometer (FTIR) and x-ray fluorescence (XRF) techniques. XRF analysis revealed major compositions of Si (26%) and Cl (71.46%), with minor elements such as Ca (0.91%), P (0.42%), K (0.37%), Fe (0.12%), and others. FTIR analysis indicated the presence of siloxane (Si-O-Si) and silanol (Si-OH) on the adsorbent. The SiO2 adsorbent demonstrated effectiveness in removing heavy metals (Ag, Cu, Mn, and Cr) from SCW, achieving removal percentages of approximately 16.96%, 24.38%, 19.34%, and 9.82%, respectively. This research contributes to the development of an environmentally friendly approach for SCW treatment using silica adsorbents derived from agricultural waste.

Soil-forming accumulation of heavy metals in geological high background areas: Constraints of structure, lithology, and overlying soil geochemistry

Heavy metals (HMs) are often abnormally enriched in soils in geologically high background areas, posing a serious threat to the ecosystem and human health. However, the material origin of HMs in overlying soils is unclear. In this paper, we studied the accumulation control and formation process of HMs (Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn) in soils overlying bedrock from different geological periods in a typical anticline structure area in southwest of Guizhou province. The results revealed that the content of HMs in the bedrock were ranked as Carboniferous carbonate rocks < Permian carbonate rocks < Triassic clastic rocks, while the opposite trend was observed for the HMs content in the overlying soil. The slopes of the EF-Q values of HMs in the soils overlying the Carboniferous, Permian, and Triassic rocks were 0.003, 0.007, and 0.83, respectively, which suggests that HMs enrichment or leaching was more complicated in the process of carbonate weathering soil-forming, whereas it was mainly in situ weathering during the process of clastic weathering soil-forming. The soils overlying the bedrock of the three geological periods experienced similar weathering processes and had the same source of soil-forming matrices, as it was observed that their Fe2O3-Al2O3, Hf-Zr, Nb-Ta, Th/Sc-Zr/Sc and Y/Ho-Y contents were significantly correlated (with R2 values of 0.80, 0.94, 0.72, 0.60, and 0.76, respectively) with very similar REE assignment patterns. The results corroborated the causes of the high background geological heterogeneity of HMs in the overlying soils in karst areas and supported the theory of the source of weathering soil-forming materials from carbonate rocks in karst areas.

Hyperbranched polymeric membranes for industrial water purification

This work aims at the preparation and characterization of dual-layer (DL) nano-fibrous mat (NFM) of hydrophobic and mechanical stable polyacrylonitrile (PAN) nano-fibers (NFs), as a supporter, and polyamide 6 (PA)/chitosan (Ch) NFs as a top hydrophilic coating layer.PAN and PA fibers, as residual wastes from textile processes, were collected and dissolved in their proper solvents. PAN was electro-spuned under certain conditions of electro-spinning (voltage, flow rate, and distance between spinneret and collector) to obtain PAN-NFM. Different ratios of PA/Ch composite were prepared and then electro-spun above the PAN-NFM that was previously prepared to obtain hydrophobic/hydrophilic functional dual-layer nano-fibrous membrane (DLNFM). The efficiency of the prepared DLNFM for capturing dye residues and heavy metals from wastewater was investigated.The viscosities of the prepared composite solutions were measured. The prepared dual-layer nano-fiber membranes (DLNFMs) were chemically and physically characterized by Fourier transform infrared spectroscopy, scanning electron microscope, X-ray diffraction, and thermogravimetric analyzer. The potential of the prepared mats for the adsorption of some heavy metal ions, i.e., Cu+2, Cr+3, and Pb+2 cations in addition to dyes from wastewater was evaluated. The effect of using different concentrations of PA/Ch composite as well as the thickness of the obtained DLNFM on the filtration efficiency was studied.The results of this study show the success of functional DLNFM in dye and heavy metal removal. The maximum removal efficiency of acid dyes was reached to 73.4 % and of reactive dye was approximately 61 % for PAN/PA-1.25%Ch DLNFM after 3 days at room temperature. The removal efficiency percent of heavy metal ions reached to 54 % by DLNFM. Additionally, the results showed that 0.08 mm is the ideal thickness for maximum absorption capacity. This value is correlated with the membrane's highest Ch percentage, which is (PAN/PA-1.25%Ch). Furthermore, the results demonstrate that the presence of the Ch polymer strengthened the produced bi-layered membrane to achieve the highest thermal stability when compared to the other nano-fibrous membranes (NFMs), with the breakdown temperature of the Ch functionalized dual-layer membranes (DLMs) reaching approximately 617 °C and a maximum weight loss of 60 %.

Adsorption of Cr(VI) and Cr(III) on layered pipe scales and the effects of disinfectants in drinking water distribution systems

Pipe scales in drinking water distribution systems (DWDS) potentially adsorb chromium (Cr). Meanwhile, the fate of Cr in pipe scales and water could be influenced by the disinfectants used in DWDS since they might influence the valence state of Cr. Therefore, the adsorption of Cr (Cr(VI) and Cr(III)) on pipe scales, the transformation between different valence states, and the effects of disinfectants present in DWDS are important research topics for improving tap water quality but have not yet been sufficiently investigated. This study investigated the properties of layered pipe scales and conducted adsorption kinetic experiments in single and binary Cr(VI) and Cr(III) systems, as well as experiments related to the oxidation and adsorption of Cr(III) under the influence of decaying disinfectants. According to the results, pipe scales exhibited distinct layered structures with varying mechanisms for the adsorption of Cr(VI) and Cr(III). Cr(VI) was adsorbed through surface complexation on the surface and porous core layers, while redox reactions predominantly occurred on the shell-like layer. Furthermore, Cr(III) was adsorbed via surface precipitation on the three-layer pipe scales. Importantly, disinfectants promoted the transformation of Cr(III) to the less readily released Cr(VI) in pipe scales, reducing the Cr exposure risk from the pipe scale phase. Pipe scales also decreased the Cr(VI) concentration in water (almost 0 mg/L), enhancing the safety of DWDS. This study provides theoretical guidance on the safe operation of DWDS.

Bioaccumulation of heavy metals in Capoeta tinca fish and health risk assessment

The This study evaluates the potential human health risks associated with five heavy metals (Zn, Pb, Cu, Cd, and Cr) in Capoeta tinca fish. It assesses the heavy metal burden in the muscle, gill, and liver tissues of C. tinca, and estimates the potential health risks for consumers by employing estimated daily intake (EDI) and standard hazard ratios (THQ) related to heavy metal consumption. Fish and water samples were taken from three different Regions as Sincan Brook (Sivas–Hafik), Habeş Brook (Sivas–Zara), and Tozanlı Brook (Sivas–Hafik), Turkey. The heavy metal concentrations in the brook water were found to be higher than the established safe for safety threshold in all the sampling points. Besides that, the values were observed to be lower than the allowed limits. Considering the fish tissues, the Pb, Cd, and Cr concentrations were found to be higher than the safe limits predicted by WHO. The findings indicate that the liver of C. tinca fish exhibited the highest accumulation of heavy metals across all sampling areas. The highest heavy metal concentrations found in fish muscles were found to be (Cu) 2.51 ± 0.91 μg·g-1, (Cr) 0.45 ± 0.03 μg·g-1, (Cd) 0.88 ± 0.04 μg·g-1, (Pb) 2.04 ± 0.03 μg·g-1, and (Zn) 13.12 ± 1.08 μg·g-1. The descending order of heavy metal accumulation in gills was found to be Zn &gt; Cu &gt;Pb &gt; Cd &gt; Cr. Moreover, for each heavy metal, the Bio–concentration factor (BCF) index, Acceptable Daily Intake, EDI, and THQ (&lt;1) values were found to be lower than the limits set in the international standards, indicating that no elements posing a threat to public health were encountered, thus not posing a short–term risk.

Atomic Absorption Spectroscopic Analysis of Heavy Metals in Cancerous Breast Tissues Among Women in Jos, Nigeria

Breast cancer is prevalent in northern Nigerian women most especially Jos, Plateau State owing to anthropogenic activities such as solid earth mineral mining. In this study, Atomic Absorption Spectrometry was used to determine the levels of eight heavy metals (Cd, As, Cr, Cu, Fe, Pb, Ni and Zn) in cancerous and non-cancerous breast tissues of Jos Nigerian Women. The concentration of heavy metals ranged from 1.08 to 29.34 mg/kg, 0.29 to 10.76 mg/kg, 0.35 to 51.93 mg/kg, 5.15 to 62.93 mg/kg, 11.64 to 51.10 mg/kg, 0.42 to 83.16 mg/kg, 2.08 to 43.07 mg/kg and 1.67 to 71.53 mg/kg for Cd, As, Cr, Cu, Fe, Pb, Ni and Zn respectively. Using MATLAB R2016a, significant differences (t&amp;lt;sub&amp;gt;v&amp;lt;/sub&amp;gt; = 0.0041 – 0.0317) existed between the levels of all the heavy metals in cancerous and non-cancerous breast tissues except Fe. At 0.01 level of significance, positive significant correlation existed between Pb and Fe, Pb and Cu, Pb and Fe, Ni and Fe, Cr and Pb, as well as Ni and Cr (r = 0.583 – 0.998) in cancerous breast tissues. Using ANOVA, significant differences also occurred in the levels of these heavy metals in cancerous breast tissues (p = 1.910510×10&amp;lt;sup&amp;gt;-26&amp;lt;/sup&amp;gt;). The relatively high levels of the cancer-induced heavy metals (Cd, As, Cr and Pb) compared with control indicated contamination or exposure to heavy metals which could be the major cause of cancer in these female subjects.

Assessment of genotoxicity of air pollution in urban areas using an integrated model of passive biomonitoring

Atmospheric pollution is a major public health issue and has become increasingly critical for human health. Urban atmospheric pollution is typically assessed through physicochemical indicators aligned with environmental legislation parameters, providing data on air quality levels. While the effects of pollution on sensitive organisms serve as a warning for public health decision-makers, there remains a need to explore the interpretation of environmental data on pollutants. The use of species adapted to urban environments as sentinels enables continuous and integrated monitoring of environmental pollution implications on biological systems. In this study, we investigated the use of the plant species Tradescantia pallida as a biomonitor to evaluate the genotoxic effects of atmospheric pollution under diverse vehicular traffic conditions. T. pallida was strategically planted at the leading urban intersections in Uberlândia, Brazil. During COVID-19 pandemic lockdowns, we compared indicators such as physical, biological, and traffic data at different intersections in residential and commercial zones. The reduction in vehicular traffic highlighted the sensitivity of plant species to changes in air and soil pollutants. T. pallida showed bioaccumulation of heavy metals Cd and Cr in monitored areas with higher traffic levels. Additionally, we established a multiple linear regression model to estimate genotoxicity using the micronucleus test, with chromium concentration in the soil (X1) and particulate matter (PM) in the atmosphere (X2) identified as the primary independent variables. Our findings provide a comprehensive portrait of the impact of vehicular traffic changes on PM and offer valuable insights for refining parameters and models of Environmental Health Surveillance.

Adsorption and distribution of heavy metals in aquatic environments: The role of colloids and effects of environmental factors

The study investigated the distributions of heavy metals (Cd, Cr, Cu, Mn, and Pb) between dissolved fraction (<0.7 µm) and particles (>0.7 µm) during the adsorption process. The dissolved fraction was further separated into truly dissolved (<3 kDa) and colloidal (3 kDa-0.7 µm) fractions. Significant metal adsorption occurred on the colloids, resulting in their aggregation into particles, which in turn influenced the particle adsorption kinetics. Colloids could either accelerate or inhibit the transformation of metal ions into particulates, depending on their stability. Competitive metals for colloids (Pb and Cr) were more susceptible to the effects of colloids than other elements. DOM was the predominant environmental factor influencing colloid behavior. The XDLVO theory showed that DOM enhanced the negative charge of colloids and made the colloid surface more hydrophilic, inhibiting the aggregation of colloids. DOM resulted in substantial increases in the concentrations of colloidal Pb and Cr from 0.31 μg/L and 4.58 μg/L to 20.52 μg/L and 43.51 μg/L, respectively, whereas the increment for less competitive metals (Cd and Mn) was smaller. These findings suggest that the distribution of heavy metals is influenced not only by adsorption from particles and ions but also by the complex dynamics of colloids.

Assessment of dumpsites leachate, geotechnical properties of the soil, and their impacts on surface and groundwater quality of Sunyani, Ghana

Leachate from sanitary landfill and dumpsites have potential to cause soil and groundwater contamination, and disrupt ecosystems. However, there is little information about dumpsite leachates and geotechnical properties and their impacts on surface and groundwater in Bono region, Ghana. This study assessed dumpsites leachate, geotechnical properties of the soil, and their impacts on surface and groundwater quality in Sunyani. Six triplicate leachates, eleven triplicate groundwater and three triplicate surface water samples were taken at (up-stream, mid-stream and down-stream) urban dumpsite, and eight triplicate groundwater samples taken around peri-urban dumpsite. Water samples were stored (<4°C) in polyethylene bottle for laboratory analysis. Physicochemical properties of leachate and water samples were analyzed using standard methods. Heavy metals (Cd, Hg, Pb, Zn, Cr, Fe, Cu, and Ni) were determined using atomic absorption spectroscopy. Water quality index (WQI) and leachate pollution loads (LPL) were investigated, while plasticity index (Ip) and liquid index (Il) were determined using Atterberg limit test. The results showed that all leachate samples were heavily polluted with mean concentrations of chlorides ranged between (2830±220 and 63810±340), biochemical oxygen demand (358±36 to 820±80), ammonium ions (82.8±2.2 to 267.6±62), and cadmium (0.49±0.02 to 5.32±1.0); with their leachate pollution index (LPI) and LPL exceeding their leachate disposal standards (LDS>100). WQI ranged from 6.51 to 289, indicating excellent to heavily polluted groundwater sources. Surface water was heavily polluted with WQI between 0.84 and 776.75, with majority having WQI>100. The heavily polluted samples were located 75-155 m away from urban dumpsite. Moderate significant negative association was established between (WQI-P and WQI-H) and distance with multiple R2=0.4709, p=0.0191 and R2= 0.4482, p=0.02425 respectively. Statistically, strong significant negative association between (WQI-P & WQI-H) and Ip (p < 0.05). This implies that when plasticity index and distance from groundwater sources to dumpsite increased, WQI values decreased, and groundwater quality improved.

Simultaneous Removal of Setazol Navy Blue and Cr(VI) By Mixed Microbial Culture Isolated from the Çubuk Stream

Water samples taken from the Çubuk Stream (Ankara, Turkey) were inoculated into nutrient broth media containing Setazol Navy Blue SBG (SNB), an organic pollutant, and heavy metal Cr(VI), an inorganic pollutant, to obtain a pollutant-resistant mixed microbial culture. Experiments were conducted with this culture to remove SNB and heavy metal. The optimum conditions, where the mixed bacterial culture removed the pollutants most effectively, were determined, showing that the highest capacity for removal took place at pH 8 with removal percentages 96.3% for Cr(VI) and 78.5% for SNB. In media with 50.4 mg/L SNB and 9.7 mg/L Cr(VI), the SNB removal was 87.3%, and the Cr(VI) removal was 96.6% at the end of the 7-day incubation period. The highest removal was observed with a biomass concentration of 8% (v/v) of mixed culture [50 mg/L SNB dye+25 mg/L Cr(VI)]. The removal was 100% for both Cr(VI) and the SNB dye. The bacteria with the highest removal were isolated and identified using 16S rDNA gene sequence analysis as Microbacterium oxydans and Leucobacter aridicollis. The role of various functional groups and the structures of the microorganisms that might be involved in the removal mechanisms were discussed using their FTIR spectra. This report is the first study that investigates a mixed bacterial culture and pure cultures (M. oxydans and L. aridicollis) isolated from that mixed culture, removing both SNB and Cr(VI) simultaneously.

Isolation of Multidrug-Resistant Bacteria from Raw Hides, Salted Hides, and Tannery Wastewater and Their Heavy Metal (Cr) Tolerance

Numerous leather products are created from cattle hides and skins. However, the processing of these products can release toxic heavy metals, including chromium into the environment, leading to health hazards and environmental pollution. This study aims to isolate and identify multidrug-resistant bacteria from rawhide, salted hides, and tanneries in different areas of the Savar region in Dhaka City, Bangladesh. The secondary objective is to determine the heavy metal tolerance and Minimum Inhibitory Concentration (MIC) of Cr against all isolated bacteria. The study found 206 bacterial isolates from three areas: Polashbari Kathaltola, Polashbari Bazar, and Savar Hemaythpur. Rawhide yielded 100 (48.54%) bacterial isolates, salted hide yielded 80(38.83%) isolates, and tannery wastewater yielded only 26 (12.62%) isolates. Further, Bacillus spp. (60) was the most common isolated bacteria. The other identified bacteria were Pseudomonas spp. (46), Staphylococcus spp. (40), Proteus spp. (40), and Escherichia coli (20). The isolated strains showed multidrug resistance, with Staphylococcus spp. Being highly resistant to Erythromycin (100%), followed by Trimethoprim (95%) and Tetracycline (88%). Pseudomonas spp. Were highly resistant to Azithromycin (100%) and Gentamycin (100%). The MIC and the MIC breakpoint determined the screening and evaluation of Cr tolerance against bacteria, and among the isolated bacterial isolates, Bacillus spp. showed a MIC breakpoint of 600 ppm (11.52mM) for Cr tolerance. The isolated heavy metal-resistant bacteria are useful in the bioremediation process and can aid in recovering and removing heavy metals from environmental effluents, thus preventing adverse effects on humans and animals. The government and leather companies should take legal responsibility for proper leather processing to ensure a preventative approach for safe public health. Otherwise, carcinogenic heavy metals can cause cancer in humans.

Synthesis of a novel tertiary amine chloride type cationic covalent organic framework at room temperature for rapid removal of Cr(Ⅵ)

Persistent toxic heavy metal Cr(Ⅵ) oxyanions is increasingly damaging to the environment and human life safety. In this study, a novel tertiary amine chloride type cationic covalent organic framework with high yield (>95%) was synthesized using a one-step Schiff base reaction by room temperature standing two functional monomers. The adsorbent was characterized by SEM, EDS, FTIR, NMR, PXRD, BET, TGA and pHPZC. And a series of adsorption experiments were conducted to verify the removal effect for Cr(Ⅵ). It exhibited excellent adsorption performance and the adsorption equilibrium time was within 10 min, superior to most adsorbents. The adsorption conformed to the pseudo-second-order kinetics and the Langmuir adsorption isothermal models based on the values of R2 and RMSE in the corresponding four models. The impact of pH was significant, and the maximum adsorption capacity was 161.4 mg/g at a pH of 2. The adsorbent had good adsorption selectivity for Cr(Ⅵ) oxyanions in the presence of coexisting ions (Cl−, SO42−, NO3−, and PO43−), and good recyclability with only decrease of removal rate from 98.3% to 91.5% after five cycles. The mechanism for Cr(Ⅵ) adsorption was mainly attributed to ion exchange, and hydrogen bonding also played a subordinate role. In the Cr(Ⅵ)-MO binary system, the increase for Cr(VI) adsorption results from the new active sites in methyl orange. This work highlights the mild synthetic conditions, fast adsorption rate, and good adsorption of Cr(Ⅵ), which make it a promising prospect.

Interspecific barrier effect driven by heavy metals makes soil bacterial functional assembly more stochastic

Residual heavy metals in soils will destroy microbial community stability and influence its aggregation. However, exploring microbial ecology under heavy-metal stress still requires a conjoint analysis of bacterial interspecies communication and the community diversity maintenance mechanism. In this study, soil samples were collected from a heavy-metal-contaminated site in China to investigate the ecological response of indigenous microbial communities through high-throughput sequencing. Results showed that bacterial taxa and functions generated unusual decoupling phenomena. There were no significant differences in the diversity of species with the increase in concentration of heavy metals (Hg, Se, and Cr), but the functional diversity was lost. Also, the average niche breadth of bacterial species increased from 1.70 to 2.28, but community stability declined and the species assembly was always a deterministic process (NST <0.5). After the bacterial functional assembly changed from a stochastic process to a deterministic process (NST <0.5), it was transformed into a stochastic process (NST >0.5) again under the stress of high-concentration heavy metals, indicating that the collective stress resistance of bacterial communities changed from positive mutation into passive functional propagation. The research results can provide new insight into understanding the adaptive evolution of communities and ecosystem restoration under the stress of soil heavy metals.

Evaluation of physicochemical parameters and heavy metal concentrations in shrimp (&lt;i&gt;Penaeus monodon&lt;/i&gt;), sediment and surrounding water of the Mangrove Swamps, Rivers State, Nigeria

The study focused on the evaluation of the physiochemical and heavy metal concentration in shrimp (P. monodon), sediments and surface water of Ikpukulu, Kalio, and Ogoloma swamps in Okrika Local Government Area, Rivers State, Nigeria. The following parameters were examined: temperature, potential hydrogen, electrical conductivity, salinity, dissolved oxygen, biochemical oxygen demand, total dissolved oxygen, temperature, and the content of heavy metals (Cd, Cu, and Cr) in surface water, sediments, and shrimp. The pH values (p &gt; 0.05) did not significantly differ amongst the stations. The three sampling station readings of pH were below WHO and FEPA (standards). The temperature data from the three stations did not show any significant differences (p &gt; 0.05), but when compared to the standards, all of the readings were much lower. Result from Ogoloma showed that it had lowest electrical conductivity ratings of the three stations, although overall, the values were higher than the norms. At Kalio, the highest Total Dissolved Solids value (9348.6 ± 67 mg/L) was recorded. When compared to the standards, the salinity values of the three stations were noticeably higher. For Biological oxygen demand, there was no significant (p&gt;0.05) difference between the three stations, but comparing the values to the standards they were all significantly (p&gt;0.05) lower. Heavy metal analysis showed that in the sediment, Copper concentration at Ogoloma was significantly (p&gt;0.05) higher among the three metals in the three stations. Copper and chromium concentrations in the three stations were much higher than the standard. Among the three metals found in the water at the three stations, copper had the highest quantities; the content of copper in Ogoloma was noticeably greater than the standard. Of the threelocations, Ogoloma exhibited a noticeably greater concentration of copper for Shrimp. Thefindings highlight the necessity for preventative action by pointing to an increase in heavy metalconcentrations in the Mangrove swamp area.

Different behavior of two strains of the arbuscular mycorrhizal fungus Rhizophagus intraradices on Senecio bonariensis Hook. & Arn. against heavy metal soil pollution: a pilot-scale test

Arbuscular mycorrhizal fungi (AMF) have different biological mechanisms to alleviate stressful conditions in heavy metals (HMs) polluted soil. These mechanisms were widely assessed under controlled/greenhouse conditions, but scarcely studied at pilot or territory scale. The aim of this study was to evaluate the response of two Rhizophagus intraradices strains isolated from soils with different histories of pollution, in association with Senecio bonariensis plants, growing in an engineering vegetal depuration module filled with artificially HMs polluted substrate. Plants inoculated with GC3 strain uptook low amounts of HMs and translocated them to shoot biomass. Heavy metals (Mg, Zn, Mn, Cr, Cu and Ni) and macronutrients (Ca, K, S and P) were accumulated in roots of S. bonariensis when inoculated with GB8 strain, limiting their translocation to the shoot. Uninoculated plants showed high translocation of all studied elements to shoot tissues. Concluding, tested R. intraradices strains have exhibited different phytoprotection mechanisms under extremely toxic concentrations of HMs. Moreover, the development of the assay at such a high Technological Readiness Level represents a novel contribution in this field of study.

New sustainable strategy for rehabilitating phosphate mining sites using phosphate industry by-products and sludge integrating Argan, Carob, and Olive trees

In semi-arid context, the development of anthroposol from phosphate industry by-products and sewage sludge could be a new approach for sustainable phosphate mining soils. The objective of this 2 years field study carried out at Benguerir phosphate mine, was to evaluate nutrients and heavy metals dynamics in the soil-plant system of three species planted on anthroposol consisting of a mixture of 65% phosphogypsum (PG), 30% phosphate sludge (PS), and 5% sewage sludge (SS). The experimental layout was a randomized complete block design with six replicates and three species: argan, olive, and carob. No fertilizer was applied to the different plots. Heights and diameters of the different species were measured. Species were pruned, and leaves and stems were separated. The nutrients (N, P, K, Ca, and Mg) and heavy metals (Cd, Cu, Cr, Pb, Ni and Zn) contents in both soil and plant part were determined. The results of the Pearson correlation showed significant correlations between height and diameter of the different species. The strongest correlation was observed for the argan tree. Furthermore, nutrient contents in the rhizosphere of species were significantly reduced, excepted Ca. Also, nutrient contents in leaves were significantly higher than those in the stems. In addition, the concentration of heavy metals in argan, olive and carob leaves, were below international standards. In semi-arid contexts, argan tree could be the best candidate for revegetating mining sites and this anthroposol (65% PG – 30% PS – 5% SS) could be a new approach to rehabilitate mining site on large scale.