Toxic Metal Species Research Articles

The emerging application of LC-based metallomics techniques to unravel the bioinorganic chemistry of toxic metal(loid)s

The on-going anthropogenic emission of toxic metal(loid) species into the environment contaminates the food supply and drinking water resources in various parts of the world. Given that inorganic pollutants cannot be degraded, their increased influx into the bloodstream of babies, children and pregnant women is inevitable. Since the ramifications of the ensuing environmental exposure on human health remain poorly defined, fundamentally new insight into their bioinorganic chemistry in organisms is urgently needed. Based on the flow of dietary constituents through organisms, the interaction of toxic metal(loid) species with biomolecules in the bloodstream deserve particular attention as they play an integral role in the mechanisms of their chronic toxicity. Gaining insight into these bioinorganic processes is hampered by the biological complexity of plasma/red blood cells and the low concentrations of the metal(loid) species of interest, but can be overcome by employing LC techniques hyphenated to atomic spectroscopic detectors (i.e. metallomics techniques). This perspective aims to highlight the potential of unconventional hyphenated separation modes to advance our understanding of the bioinorganic chemistry of toxic metal(loid) species in the bloodstream-organ system. Four examples are illustrated. The application of anion-exchange (AEX) and size-exclusion chromatography (SEC) provided new insight into the blood-based bioinorganic mechanisms that direct Cd2+ and MeHg+ to target organs. AEX chromatography also allowed to observe the formation of complexes between Hg2+ and MeHg+ with L-cysteine at pH 7.4, that are implicated in their organ uptake. Lastly, the application of reversed phase (RP) chromatography revealed a possible cytosolic mechanism by which N-acetyl-L-cysteine binds to MeHg+ in the presence of cytosolic glutathione (GSH). New insight into other bioinorganic processes may advance the regulatory framework to better protect public health.

Speciation of toxic metals in metal finishing filter cake by X-ray absorption spectroscopy

The speciation of Cr, Zn, Cu and Pb in two metal finishing filter cakes (TX and ST) was investigated by X-ray absorption spectroscopy (XAS) complemented by X-ray fluorescence (XRF) and X-ray diffraction (XRD). XRF showed that concentrations of Cr, Zn, Cu and Pb were 1.4%, 0.19%, 0.20% and 0.01%, respectively, in TX, and 12.6%, 3.3%, 1.3% and 0.21% in ST. No crystalline phases were detected in TX by XRD whereas ST was dominated by calcite. Cr and Fe K edge XAS showed Cr to be trivalent and octahedrally coordinated, co-precipitated with Fe as CrxFe1-x-(oxy)hydroxides in both filter cakes. Zn, P and Ca K edge XAS showed that 2ZnCO3∙3Zn(OH)2 and Zn3(PO4)2 were the dominant zinc-containing phases, with combined tetrahedral and octahedral coordination; Zn phases were slightly more crystalline in TX than ST. Pb L3 edge X-ray absorption near edge spectroscopy (XANES) found that Pb was likely adsorbed on amorphous SiO2. Cu, Si and S K edge XAS showed that all Cu was divalent, and the dominant copper phases were found to be Cu2Cl(OH)3, Cu(OH)2 and CuSO4·5H2O for ST, whereas Cu appeared to adsorb to amorphous SiO2 for TX, which contained much less Pb. Cr is thus immobilized in the filter cakes in a phase with low solubility at environmentally feasible pH values, whereas Zn, Cu and Pb could be released when the pH decreases below 8 or above 11. These findings are significant for the development of waste management regulations and/or metal recovery methods (e.g., hydro/pyrometallurgy).

Efficacy of Modified Magnolia champaca Bark Powder in Sequestration of Divalent Ions from Aqueous Matrices

Noxious effluents let out from large cum small- scale industries has led to acute adverse environmental impact over a time period. In spite of various types of pollutants present in the discharges, heavy metals have been proven to be lethal to all living organisms, whilst exceeding the tolerance levels. In this regard, their confiscation has become inevitable by adoption of varied suitable methodologies. The current inquest is engrossed on probing the efficiency of an eco-derived material, Magnolia champaca Barks (MCB) to trap Zn(II) / Cd(II) ions from laboratory aqueous medium. This ecofriendly material is acid treated (TMCB), so as to improve its surface nature, evidently favoured by microscopic image study. Fourier Transformation Infra-Red and Scanning Electron Microscopy / Energy Dispersive X-Ray Analysis spectra are recorded for sorbent characterization. The factors which influence the sorptive effectiveness of TMCB include particle sizes, initial concentrations of the sorbate molecules, agitation time frames, dosages, pH values and temperatures. The concentrations of divalent ions in the pre and post run samples are assessed using Atomic Absorption Spectrophotometer. Maximum chelation of 98% Zn(II) and 96% Cd(II) had occurred under aligned parametric conditions, with variations in dosage, concentration and contact time interval. The aforementioned observations support the promising nature of the identified bark to adsorb toxic metal species.

Toward a Mechanism-Driven Integrated Framework to Link Human Exposure to Multiple Toxic Metal(loid) Species with Environmental Diseases.

The ongoing anthropogenic pollution of the biosphere with As, Cd, Hg and Pb will inevitably result in an increased influx of their corresponding toxic metal(loid) species into the bloodstream of human populations, including children and pregnant women. To delineate whether the measurable concentrations of these inorganic pollutants in the bloodstream are tolerable or implicated in the onset of environmental diseases urgently requires new insight into their dynamic bioinorganic chemistry in the bloodstream-organ system. Owing to the human exposure to multiple toxic metal(loid) species, the mechanism of chronic toxicity of each of these needs to be integrated into a framework to better define the underlying exposure-disease relationship. Accordingly, this review highlights some recent advances into the bioinorganic chemistry of the Cd2+, Hg2+ and CH3Hg+ in blood plasma, red blood cells and target organs and provides a first glimpse of their emerging mechanisms of chronic toxicity. Although many important knowledge gaps remain, it is essential to design experiments with the intent of refining these mechanisms to eventually establish a framework that may allow us to causally link the cumulative exposure of human populations to multiple toxic metal(loid) species with environmental diseases of unknown etiology that do not appear to have a genetic origin. Thus, researchers from a variety of scientific disciplines need to contribute to this interdisciplinary effort to rationally address this public health threat which may require the implementation of stronger regulatory requirements to improve planetary and human health, which are fundamentally intertwined.

Translational toxicology of metal(loid) species: linking their bioinorganic chemistry in the bloodstream to organ damage onset.

The quantification of arsenic, mercury, cadmium and lead in the human bloodstream is routinely used today to assess exposure to these toxic metal(loid)s, but the interpretation of the obtained data in terms of their cumulative health relevance remains problematic. Seemingly unrelated to this, epidemiological studies strongly suggest that the simultaneous chronic exposure to these environmental pollutants is associated with the etiology of autism, type 2 diabetes, irritable bowel disease and other diseases. This from a public health point of view undesirable situation urgently requires research initiatives to establish functional connections between human exposure to multiple toxic metal(loid) species and adverse health effects. One way to establish causal exposure-response relationships is a molecular toxicology approach, which requires one to unravel the biomolecular mechanisms that unfold after individual toxic metal(loid)s enter the bloodstream/organ nexus as these interactions ultimately determine which metabolites impinge on target organs and thus provide mechanistic links to diseases of unknown etiology. In an attempt to underscore the importance of the toxicological chemistry of metal(loid)s in the bloodstream, this review summarizes recent progress into relevant bioinorganic processes that are implicated in the etiology of adverse organ-based health effects and possibly diseases. A better understanding of these bioinorganic processes will not only help to improve the regulatory framework to better protect humans from the adverse effects of toxic metal(loid) species, but also represents an important starting point for the development of treatments to ameliorate pollution-induced adverse health effects on human populations, including pregnant women, the fetus and children.

Adsorptive Recovery of Heavy Metal Ions from Aquatic Systems Using Metal‐Organic Frameworks: A Perspective in the Sustainable Development of Nanomaterials

AbstractRapid industrialization in the developing countries has facilitated the unwanted mixing of wastes into the already depleting sources of potable, domestic and industrial water. In particular, the mixing of toxic heavy metal wastes into the aquatic resources have not only increased the scarcity of water at the different levels of usage but also hygiene of the ecosystem is further threatened by the presence of abysmal quality of aquatic environment around the living world. Thus, it has become quite imperative to mitigate such problems through the removal of such water contaminants at the sources before supplied for a specific purpose. In this direction, among the other available mass transfer techniques, specific and efficient adsorption of heavy metal species on the nanomaterials such as metal‐organic frameworks (MOFs) are found to be a promising method of heavy metal ions recovery. This reports targets to provide a new perspective into heavy metal ions removal from wastewater as a rationale for sustainable nanomaterial engineering through the recycling of toxic metal species as precious precursors in the synthesis of nanomaterials. Decades of exploring materials sciences led to the generation of groundbreaking materials of nanoscale regime, which has advanced myriad avenues of science and technology, viz. electronic, energy, biomedical, environmental, agriculture applications, and more. In this regard, nanotechnology has had a global impact by several folds, which can be observed in all day‐to‐day facilities. This perspective aims to conceptualize a strategy of wastewater decontamination through the adsorptive retrieval of heavy metal species to be subsequently recycled in the design of smart nanomaterials.

Role of functionalization in the fluorescence quantum yield of graphene quantum dots

As graphene is sculptured into quantum dots, quantum confinement and edge effects induce a finite energy gap and trigger exotic photoluminescent behavior. However, synthesis of graphene quantum dots (GQDs) with high fluorescence quantum yield and designated emission color remains challenging, due to a lack of knowledge in the exact influences of various structural and chemical factors. Herein, we explore the optical absorption and emission in GQDs with surface functionalization, heteroatom doping, or edge modification. Their fluorescence spectra are systematically compared by time-dependent density functional theory calculations. It shows that the sp3-type surface functionalization by O, OH, or F groups can effectively increase the fluorescence intensity by five orders of magnitude with regard to pristine GQDs, ascribed to the localization of excited carriers that enlarges the transition dipole moment for radiative decay. The functional groups also play a key role in fluorescent sensing of toxic metal species with high selectivity and sensitivity.

Quenching of the Photoluminescence of Gold Nanoclusters Synthesized by Pulsed Laser Ablation in Water upon Interaction with Toxic Metal Species in Aqueous Solution

Sensors for the detection of heavy metal ions in water are in high demand due to the danger they pose to both the environment and human health. Among their possible detection approaches, modulation of the photoluminescence of gold nanoclusters (AuNCs) is gaining wide interest as an alternative to classical analytical methods based on complex and high-cost instrumentation. In the present work, luminescent oxidized AuNCs emitting in both ultraviolet (UV) and visible (blue) regions were synthesized by pulsed laser ablation of a gold target in NaOH aqueous solution, followed by different bleaching processes. High-resolution electron microscopy and energy-dispersive X-ray scattering confirmed the presence of oxygen and gold in the transparent photoluminescent clusters, with an average diameter of about 3 nm. The potentialities of the bleached AuNCs colloidal dispersions for the detection of heavy metal ions were studied by evaluating the variation in photoluminescence in the presence of Cd2+, Pb2+, Hg2+ and CH3Hg+ ions. Different responses were observed in the UV and visible (blue) spectral regions. The intensity of blue emission decreased (no more than 10%) and saturated at concentrations higher than 20 ppb for all the heavy metal ions tested. In contrast, the UV band emission was remarkably affected in the presence of Hg2+ ions, thus leading to signal variations for concentrations well beyond 20 ppb (the concentration at which saturation occurs for other ions). The limit of detection for Hg2+ is about 3 ppb (15 nmol/L), and the photoluminescence intensity diminishes linearly by about 75% up to 600 ppb. The results are interpreted based on the ligand-free interaction, i.e., the metallophilic bonding formation of Hg2+ and Au+ oxide present on the surface of the UV-emitting nanoclusters.

A Robust Strontium Coordination Polymer with Selective and Sensitive Fluorescence Sensing Ability for Fe3+ Ions.

Exploration of sensitive and selective fluorescence sensors towards toxic metal species is of great importance to solve metal pollution issues. In this work, a three-dimensional (3D) strontium coordination polymer of Sr2(tcbpe) (H4tcbpe = 1,1,2,2-tetrakis(4-(4-carboxy-phenyl)phenyl)ethene) has been synthesized and developed as a fluorescent sensor to Fe3+ ions. Sr2(tcbpe) shows a mechanochromic fluorescence with emission shifting from blue of the pristine to green after being ground. Notably, based on a fluorescence quenching mechanism, Sr2(tcbpe) displays a sensitive and selective fluorescent sensing behavior to Fe3+ ions with a detection limit of 0.14 mM. Moreover, Sr2(tcbpe) exhibits high tolerance to water in a wide pH range (pH = 3-13), demonstrating that Sr2(tcbpe) is a potential fluorescent sensor of Fe3+ in water.

Integrative Metallomics Studies of Toxic Metal(loid) Substances at the Blood Plasma–Red Blood Cell–Organ/Tumor Nexus

Globally, an estimated 9 million deaths per year are caused by human exposure to environmental pollutants, including toxic metal(loid) species. Since pollution is underestimated in calculations of the global burden of disease, the actual number of pollution-related deaths per year is likely to be substantially greater. Conversely, anticancer metallodrugs are deliberately administered to cancer patients, but their often dose-limiting severe adverse side-effects necessitate the urgent development of more effective metallodrugs that offer fewer off-target effects. What these seemingly unrelated events have in common is our limited understanding of what happens when each of these toxic metal(loid) substances enter the human bloodstream. However, the bioinorganic chemistry that unfolds at the plasma/red blood cell interface is directly implicated in mediating organ/tumor damage and, therefore, is of immediate toxicological and pharmacological relevance. This perspective will provide a brief synopsis of the bioinorganic chemistry of AsIII, Cd2+, Hg2+, CH3Hg+ and the anticancer metallodrug cisplatin in the bloodstream. Probing these processes at near-physiological conditions and integrating the results with biochemical events within organs and/or tumors has the potential to causally link chronic human exposure to toxic metal(loid) species with disease etiology and to translate more novel anticancer metal complexes to clinical studies, which will significantly improve human health in the 21st century.

CHEMICAL SPECIATION OF SOME HEAVY METALS AND HUMAN HEALTH RISK ASSESSMENT IN WATER AROUND MUNICIPAL DUMPSITES IN JOS, BUKURU AND RAYFIELD, PLATEAU STATE, NIGERIA

The impact of solid waste disposal on water quality is gaining importance worldwide due to seepage of toxic metals through the soil into the groundwater. Urbanization, industrialization and changes in our life styles have compounded the problem of solid waste management in Nigeria. Poor waste management threatens the health of humans and animals, particularly those livingclose to these pollution point sources.The study area covers Jos-Bukuru and environs in North Central Nigeria. This study was aimed at investigating the chemical species present in groundwater as a result of the impact of solid waste dumpsites in the study area and to evaluate the contributions of the dumpsites to the chemical and physicochemical properties of groundwater around the dumps. Five (5) major dumpsites (Bauchi Road Jos, Rukuba Road Jos, Building Materials Market, Rayfield and Bukuru Town) were sampled for this study. Ten water samples from hand dug wells (two from each site) close to the dumpsites and three controls were collected and analysed for chemical composition and further speciation analysis was conducted on the chemical result to assess the various species present in the waters and possible human health related issues. Results show that the mean values of the pH, temperature, EC, TDS, of the water samples all fall within the WHO permissible limits for portable drinking water. Content of trace elements are generally low in the waters but toxic metal species such as Ba+2, Mn+2, Ni+2, Zn+2, Cd+2, and Pb+2 are common to all the water sources. This study shows that different dumpsites have impacted differently on waters in their different environments. There is the need to curtail the excesses of dumping waste in these areas so as not to add to the exiting contents of toxic metal species in the waters.

Cr3+ incorporation into an Al3+ Keggin-type oligomer to form the Al25.7Cr6.3S216+ polycation

The partial hydrolysis of Al 3+ solution by titrating with Cr 3+ salt dissolved in KOH solution formed polycationic Keggin oligomer Al 25.7 Cr 6.3 S 2 16+ (Al 25.7 Cr 6.3 O 8 (OH) 60 (H 2 O) 28 (SO 4 ) 2 ). • Synthesis, crystallization, and chemical characterization of a novel Cr 3+ substituted polycationic Al 3+ Keggin-type oligomer. • Elucidating structure of this Keggin oligomer enhanced the atomistic level understanding of Cr 3+ incorporation in this system. • Formation of this novel Keggin oligomer pointed out important role base cation may play in oligomerization process. Keggin-type aluminum polycations are an important class of compounds from metal-oxo family that includes polyoxometalates and other nanocomplexes. Investigation of the Al 3+ based polycation system is of particular importance given the environmental relevance within acid mine drainage and application in wastewater treatment. Within streams impacted with acid mine drainage, different toxic metal species, including chromium, can incorporate into these soluble polycations and impact the transport of contaminants. Currently, there is a limited understanding about chemical interaction of chromium with Keggin-type aluminum polycations; therefore, the work herein describes the synthesis and characterization Cr 3+ substitution within Keggin-based polyaluminum species. The polyaluminum cations crystallized as [Al 25.7 Cr 6.3 O 8 (OH) 60 (H 2 O) 28 (SO 4 ) 2 ](SO 4 ) 8 (H 2 O) 29 from a partially hydrolyzed Al 3+ solution and structural elucidation obtained by single crystal X-ray diffraction revealed the presence of Cr 3+ within the octahedral sites of the Keggin species. Inductively coupled plasma mass spectroscopy confirmed the presence of Cr 3+ in the structure with Al 3+ /Cr 3+ similar to refined crystal structure. Additional physicochemical characterization, including vibrational spectroscopy, thermogravimetry and powder X-ray diffraction were performed on the isolated crystals and confirm the structural model of the solid phase.

A synthetic health risk assessment based on geochemical equilibrium simulation and grid spatial interpolation for zinc (II) species

Soil heavy metal pollution has become a global issue involving environmental safety and human health risks. This paper quantified the sources of heavy metals by positive matrix factorization (PMF) model and explored the spatial distribution of heavy metals by means of grid scales, with an industrial site as the study area in Suzhou. The PMF identified four pollution sources of heavy metal in soil, and the quantitative results revealed that industrial activities (33.5%) contributed the most to heavy metals, followed by soil parent materials (30.8%) and agricultural activities (19.7%). Zinc (Zn) was screened out as the targeted metal (TM) through the potential ecological risk assessment, the metal species of which was simulated by the geochemical software PHREEQC. This research aimed to determine the dominant metal species of TM with high-risk levels to realize the transformation of toxic metal species. Herein, according to the morphological evolution of metal species, the activity and concentration of the Zn ion species were obtained for both carcinogenic and non-carcinogenic risk assessment. The evaluation of the optimized human health risk demonstrated that the associated health risk of Zn (II) ions depended predominantly on its metal speciation. Overall, the optimized carcinogenic and non-carcinogenic risk value of Zn2S32− for adults was 2.01E-04 and for children was 1.31, resulting in corresponding hazardous risk to humans, which accounted for high-risk levels of 61.5% and 58.5% for adults and children, respectively. The OHRA method can provide a reference for the decision-making of soil heavy metal pollution and remediation for specific heavy metals in polluted areas.

A Simple One-Step Modification of Shrimp Shell for the Efficient Adsorption and Desorption of Copper Ions.

Removing toxic heavy metal species from aqueous solutions is a point of concern in our society. In this paper, a promising biomass adsorbent, the modified waste shrimp shell (MS), for Cu (II) removal was successfully prepared using a facile and simple one-step modification, making it possible to achieve high-efficiency recycling of the waste NaOH solution as the modification agent. The outcome shows that with the continuous increase in pH, temperature and ion concentration, the adsorption effect of MS on Cu (II) can also be continuously improved. Adsorption isotherm and adsorption kinetics were fitted with the Langmuir isotherm model and the pseudo-second-order model, respectively, and the maximum adsorption capacity of Cu (II) as obtained from the Langmuir isotherm model fitting reached 1.04 mmol/g. The systematic desorption results indicated that the desorption rate of Cu (II) in the MS could reach 100% within 6 min, where HNO3 is used as the desorption agent. Moreover, experiments have proven that after five successive recycles of NaOH as a modifier, the adsorption capacity of MS on Cu (II) was efficient and stable, maintaining tendency in 0.83–0.85 mmol/g, which shows that waste NaOH solution can be used as a modification agent in the preparation of waste shrimp shell adsorbent, such as waste NaOH solution produced in industrial production, thereby making it possible to turn waste into renewable resources and providing a new way to recycle resources.

Toxic Metal Species and 'Endogenous' Metalloproteins at the Blood-Organ Interface: Analytical and Bioinorganic Aspects.

Globally, human exposure to environmental pollutants causes an estimated 9 million deaths per year and it could also be implicated in the etiology of diseases that do not appear to have a genetic origin. Accordingly, there is a need to gain information about the biomolecular mechanisms that causally link exposure to inorganic environmental pollutants with distinct adverse health effects. Although the analysis of blood plasma and red blood cell (RBC) cytosol can provide important biochemical information about these mechanisms, the inherent complexity of these biological matrices can make this a difficult task. In this perspective, we will examine the use of metalloentities that are present in plasma and RBC cytosol as potential exposure biomarkers to assess human exposure to inorganic pollutants. Our primary objective is to explore the principal bioinorganic processes that contribute to increased or decreased metalloprotein concentrations in plasma and/or RBC cytosol. Furthermore, we will also identify metabolites which can form in the bloodstream and contain essential as well as toxic metals for use as exposure biomarkers. While the latter metal species represent useful biomarkers for short-term exposure, endogenous plasma metalloproteins represent indicators to assess the long-term exposure of an individual to inorganic pollutants. Based on these considerations, the quantification of metalloentities in blood plasma and/or RBC cytosol is identified as a feasible research avenue to better understand the adverse health effects that are associated with chronic exposure of various human populations to inorganic pollutants. Exposure to these pollutants will likely increase as a consequence of technological advances, including the fast-growing applications of metal-based engineering nanomaterials.

Nigerian Defence Academy Shooting Zone: Soil Speciation of the Kwanar-Doya Military Shooting Range, Kachia, Kaduna State, Nigeria

The speciation of toxic metals of Co, Cr, Cu, Mn, Pb, Zn, Ni and As in Kwanar – Doya Shooting site of the Nigerian Army, Military Training, Base Camp, Kachia, Kaduna State, Nigeria was investigated. The soil physico-chemical parameters, total metal content and sequential extraction methods were determined in duplicates using standard methods. The pH ranged from 3.93–4.51, showing the high acidity of the soil and electro -conductivity gave a mean value of 0.11 ms / cm showing the poor nutrient value of the soil). While the mean total metals values were Zinc: 28.94 mg/kg, Nickel: 13.45mg/kg, Manganese: 78: 12 mg/kg, Lead: 40.6 mg/kg, Arsenic: 305 mg/kg, Chromium: 49.32 mg/kg, Cobalt: 162:50 mg/kg and copper: 7.3 mg/kg. All the metals were above the W.H.O permissible limit for toxic metals in soils except Zinc and Nickel. The sequential partitioning and distribution and variation of toxic metals in the various fractions of the Nigerian Defence Academy Shooting Range soil were in the following order: Cobalt: Residual > Bound to carbonate > Exchangeable > Organic > Fe – Mn Oxide Arsenic: Fe – Mn Oxide > Bound to carbonate > Residual > Organic > Chromium: Bound to carbonate > Exchangeable > Fe – Mn Oxide > Organic > Residual. Nickel: Fe – Mn Oxide > Exchangeable > Bound to carbonate > Residual > Organic. Manganese: Residual > Fe – Mn Oxide > Bound to carbonate > Organic > Exchangeable. Lead: Residual > Organic > Bound to carbonate > Exchangeable > Fe – Mn Oxide. Zinc: Fe – Mn Oxide > Residual > Organic > Bound to carbonate > Exchangeable. Copper: Residual > Fe – Mn Oxide > Exchangeable > Bound to carbonate > Organic. The Toxic metals speciation of the soil samples indicate that the toxic metals were predominately in the non-residual fractions suggestive of input by anthropogenic sources and human activities due to military exercise and are readily available for plant uptake. This could pose serious health risk to the military personnel using the training period. Thus phyto-remediation technique which is cheap and non-destructive is recommended to be applied to remedy the affected toxic metals in the soil for its continual use as a military training ground and also preserve the soil fertility for continued agricultural use of the area when there is no military operation.

Nigerian Defence Academy Shooting Zone: Soil Speciation of the Kwanar-Doya Military Shooting Range, Kachia, Kaduna State, Nigeria

The speciation of toxic metals of Co, Cr, Cu, Mn, Pb, Zn, Ni and As in Kwanar – Doya Shooting site of the Nigerian Army, Military Training, Base Camp, Kachia, Kaduna State, Nigeria was investigated. The soil physico-chemical parameters, total metal content and sequential extraction methods were determined in duplicates using standard methods. The pH ranged from 3.93–4.51, showing the high acidity of the soil and electro -conductivity gave a mean value of 0.11 ms / cm showing the poor nutrient value of the soil). While the mean total metals values were Zinc: 28.94 mg/kg, Nickel: 13.45mg/kg, Manganese: 78: 12 mg/kg, Lead: 40.6 mg/kg, Arsenic: 305 mg/kg, Chromium: 49.32 mg/kg, Cobalt: 162:50 mg/kg and copper: 7.3 mg/kg. All the metals were above the W.H.O permissible limit for toxic metals in soils except Zinc and Nickel. The sequential partitioning and distribution and variation of toxic metals in the various fractions of the Nigerian Defence Academy Shooting Range soil were in the following order: Cobalt: Residual > Bound to carbonate > Exchangeable > Organic > Fe – Mn Oxide Arsenic: Fe – Mn Oxide > Bound to carbonate > Residual > Organic > Chromium: Bound to carbonate > Exchangeable > Fe – Mn Oxide > Organic > Residual. Nickel: Fe – Mn Oxide > Exchangeable > Bound to carbonate > Residual > Organic. Manganese: Residual > Fe – Mn Oxide > Bound to carbonate > Organic > Exchangeable. Lead: Residual > Organic > Bound to carbonate > Exchangeable > Fe – Mn Oxide. Zinc: Fe – Mn Oxide > Residual > Organic > Bound to carbonate > Exchangeable. Copper: Residual > Fe – Mn Oxide > Exchangeable > Bound to carbonate > Organic. The Toxic metals speciation of the soil samples indicate that the toxic metals were predominately in the non-residual fractions suggestive of input by anthropogenic sources and human activities due to military exercise and are readily available for plant uptake. This could pose serious health risk to the military personnel using the training period. Thus phyto-remediation technique which is cheap and non-destructive is recommended to be applied to remedy the affected toxic metals in the soil for its continual use as a military training ground and also preserve the soil fertility for continued agricultural use of the area when there is no military operation.

A functionalized nanocomposite adsorbent for the sequential removal of radioactive iodine and cobalt ions in aqueous media

The need for efficient remediation of the radioactive waste caused by undesirable nuclear accidents and overspending of radionuclides has gained worldwide attention, with extensive recent efforts made to protect the environment from radioactive contamination. Although various treatment processes for the removal of radionuclides and the purification of liquid waste have been reported, the development of a better decontamination method is still necessary for obtaining enhanced desalination performances. Herein, we report a dual-functional composite adsorbent composed of a cellulose acetate membrane as a solid support, gold nanoparticles (AuNPs), and a metal chelating agent which can potentially be used to efficiently remove radioactive iodine and cobalt. In the desalination experiments, the sorption membrane was able to remove cobalt ions rapidly in water. Isotherm data shows that approximately 180 Co2+ atoms were captured per AuNP. Next, the same material was used for the adsorption of iodide anions. Within a few minutes, more than 99% of radioactive iodine was removed even in the presence of other ion species. These findings clearly demonstrate that the desalination method presented in here provides a useful approach for the sequential removal of toxic metal and halogen species in aqueous media.

Pipes could release toxic chromium into tap water

A new study shows that the carcinogen hexavalent chromium can slip into drinking water when commonly used chlorine disinfectants corrode cast-iron water distribution pipes ( Environ. Sci. Technol. 2020, DOI: 10.1021/acs.est.0c03922 ). Until now, most scientists thought that chromium found in drinking water originated from natural sources or industrial pollution. Haizhou Liu and his team at the University of California, Riverside, found another possible source by scraping some of the crusty scale out of two sections of cast-iron pipes from US drinking water systems. Cast iron is widely used in these pipes and contains significant amounts of Cr(0) in the alloy to help prevent corrosion. The scientists incubated the scale samples in a solution of hypochlorous acid, the oxidizing sanitizer commonly used to treat drinking water. The disinfectant-treated scales rapidly cranked out Cr(VI), whereas scales in water with no disinfectant produced none of the toxic metal species. Also, when exposed

Assessment of particulate toxic metals at an Environmental Justice community

Abstract Exposure to particulate matter containing toxic metal species can have negative health implications. The community of Eden Park, Delaware, is surrounded by numerous industrial facilities, the Port of Wilmington, and a highly trafficked freeway, all of which can be sources of toxic metals. The U.S. Environmental Protection Agency's EJ Screen ranks the community in the 88th percentile nationally for the Environmental Justice (EJ) index of cancer risk and the 90th percentile for the EJ index of PM2.5 exposure. To understand the ambient concentrations and sources of toxic metals and particulate matter, we collected hourly PM10 metals measurements using an Xact 625i at a temporary monitoring site in the community. Additionally, PM2.5, wind speed and direction, NOx, SO2, and black carbon were monitored. Conditional bivariate probability function maps and time variation maps were constructed using the OpenAir statistical analysis package, and EPA Positive Matrix Factorization was used to determine the sources of the measured metals. We found that transient concentration events, where arsenic and lead concentrations were more than an order of magnitude larger than the study average, occurred intermittently, but concentrations were generally below health benchmarks. Chromium and nickel had common sources, including a metal plating facility and a chemical additive facility, and unidentified sources were responsible for spikes in chromium levels up to 17 times above average. With Positive Matrix Factorization, three sources were identified: soil/dust, concrete manufacturing dust, and brake wear. During periods of moderate air quality (PM10 = 55–154 μg/m3) concrete dust contributes 32% to PM10 concentrations, while soil dust contributes 12%. Overall, the local industry and intermodal traffic emissions are large contributors to the ambient air pollution in the community, though transient high-concentration events from other sources are also present.