High Concentrations Of Heavy Metals Research Articles

Complex resistivity spectrum of pollutant soils with low-concentration heavy metals

Soil contamination by heavy metals occurs globally, with varying degrees of severity, especially in agricultural fields. Investigating the frequency response characteristics of different types of heavy metal pollutants through induced polarization can provide valuable evidence for surveys based on this method. Soil specimens with varying low concentrations of copper (Cu), chromium (Cr), cadmium (Cd), and lead (Pb) heavy metals were prepared for this study, and parameters including complex resistivity, amplitude-frequency, and resistivity phase were measured. Our findings reveal the following trends: Complex resistivity decreases as heavy metal concentrations increase, demonstrating significant shifts within lower concentration ranges but presenting limitations for assessing pollution in high-concentration areas. Conversely, amplitude-frequency increases with higher heavy metal concentrations, displaying excellent performance in high-concentration scenarios. The differences in complex resistivity and amplitude-frequency among different types of heavy metal pollutants are distinct. In contrast, the absolute phase decreases with rising heavy metal concentrations. The resistivity phase spectra for various heavy metal pollutants exhibit unique patterns. For example, copper-contaminated soil exhibits phase peaks in the frequency range of 8–32 Hz, whereas chromium-contaminated soil shows phase peaks at 16–64 Hz. Cadmium-contaminated soil displays phase peaks ranging from 0.25 Hz to 2 Hz, while lead-contaminated soil exhibits phase peaks within the 0.5 Hz–4 Hz range. Leveraging the frequency range corresponding to phase peaks as an identification method for heavy metal pollution types proves effective. The frequency response characteristics of induced polarization vary significantly among different types and concentrations of heavy metal pollutants, providing important foundations for the application of induced polarization method in the field of heavy metal pollution detection.

HPO-empowered machine learning with multiple environment variables enables spatial prediction of soil heavy metals in coastal delta farmland of China

Machine learning (ML) models have been widely used for predicting spatial variability of soil heavy metals. However, it is impossible to explore the entire hyperparameter space of ML models by artificially trial-and-error experimentation. Here, an auto hyperparameter optimization-based machine learning (HPO-ML) method with three search algorithms and random forest (RF) and extreme gradient boosting (XGBoost) models was developed to predict the heavy metal content in soil with multiple environmental variables. The tree-structured Parzen estimator (TPE) algorithm outperformed other search algorithms in identifying the optimal hyperparameters of RF and XGBoost models. The model prediction results showed that the TPE-XGBoost had the highest accuracy for predicting the As (RMSE = 3.06 mg kg−1 and R2 = 70.35%), Cd (RMSE = 0.10 mg kg−1 and R2 = 75.43%), Cr (RMSE = 13.86 mg kg−1 and R2 = 82.11%), Ni (RMSE = 3.19 mg kg−1 and R2 = 75.20%), Pb (RMSE = 3.75 mg kg−1 and R2 = 74.79%), and Zn (RMSE = 6.83 mg kg−1 and R2 = 70.05%) contents. The TPE-XGBoost mapping result showed that areas with high concentrations of soil heavy metals were concentrated in the central and eastern areas (As), the mainstream of the Yellow River (Cd), the northeast area (Cr), the ancient watercourse of the Yellow River (Ni and Pb), and the central and northeastern areas (Zn). The SHapley additive explanation (SHAP) and structural equation model (SEM) were used to interpret the drivers of environmental variables. It is found that the variables with the highest contributions were CO, PM2.5, O3, PC3, PC1, and PC4 for predicting the As, Cd, Cr, Ni, Pb, and Zn contents, respectively, and there was a significant source-receptor coupling path. The results demonstrate the feasibility of using the HPO-ML approach in hyperparameter-limited conditions, which providing data-driven pathways and options to support the high-quality development of agriculture and the protection of farmland soil ecosystem.

Impacts of climate change and coastal salinization on the environmental risk of heavy metal contamination along the odisha coast, India.

Climate change-mediated rise in sea level and storm surges, along with indiscriminate exploitation of groundwater along populous coastal regions have led to seawater intrusion. Studies on groundwater salinization and heavy metal contamination trends are limited. Present study investigated the heavy metal contamination, associated risks and provided initial information on the impacts of groundwater salinization on heavy metals along the coastal plains of Odisha, India. Total 50 groundwater samples (25 each in post- and pre-monsoon) were collected and analysed. Concentrations of Fe (44%), Mn (44%), As (4%) and Al (4%) in post-monsoon and Fe (32%), Mn (32%), As (4%), B (8%) and Ni (16%) in pre-monsoon exceeded Bureau of Indian Standards (BIS) drinking water limits. High concentrations of heavy metals (Fe, Sr, Mn, B, Ba, Li, Ni and Co) and high EC (>3000 μS/cm) indicated that the groundwater-seawater mixing process has enhanced the leaching and ion exchange of metallic ions in central part of the study area. Multivariate statistical analysis suggested leaching process, seawater intrusion and agricultural practices as the main heavy metal sources in the groundwater. 4% of samples in post- and 16% in pre-monsoon represented high heavy metal pollution index (HPI). Pollution indices indicated the central and south-central regions are highly polluted due to saline water intrusion and high agricultural activities. Ecological risks in the groundwater systems found low (ERI <110) in both seasons. Children population found more susceptible to health risks than adults. Hazard index (HI > 1) has shown significant non-carcinogenic risks where Fe, Mn, As, B, Li and Co are the potential contributors. Incremental lifetime cancer risk (ILCR >1.0E-03) has suggested high carcinogenic risks, where As and Ni are the major contributors. The study concluded that groundwater salinization could increase the heavy metal content and associated risks. This would help policymakers to take appropriate measures for sustainable coastal groundwater management.

Comparative study of electroplating sludge reutilization in China: environmental and economic performances.

Harmless disposal and reutilization of electroplating sludge (ES) attract growing interests due to the high content of heavy metals, which requires economical-affordable and environmentally friendly processing technologies. Main reutilization alternatives in China, i.e., acid leaching, bioleaching, smelting, ironmaking blast furnace co-processing (IBFC), and cement kiln co-processing (CKC), were evaluated and compared via life cycle assessment (LCA) and life cycle costing (LCC) methods. In addition, the heavy metal recovery potential of these scenarios was also evaluated to focus on the sustainable use of metal resources. LCA results show that acid leaching outperforms other scenarios due to the environmental benefits originating from recovering heavy metals, while smelting exhibits the worst due to high energy consumption. The environmental contribution analysis reveals that the product nickel sulfate has a significant positive impact on acid leaching and bioleaching scenarios, and energy consumption is the key factor for smelting, IBFC, and CKC. LCC results show that bioleaching outperforms others, while CKC performs the worst because only inorganic materials are utilized. Bioleaching has the lowest externality cost while CKC has the highest. The heavy metal recovery assessment indicates that bioleaching exhibits the greatest potential with recovery rates of 99%, 99%, 93%, 96%, and 95% for Cu, Cr, Ni, Zn, and Fe, respectively. In contrast, the target heavy metal recovery rate for both acid leaching and smelting is 93%. Acid leaching and bioleaching scenarios are more advantageous from a comprehensive comparison.

Gene knockout of glutathione reductase results in increased sensitivity to heavy metals in Acidithiobacillus caldus.

Acidithiobacillus caldus plays an important role in bioleaching of low-grade metal ore. It can promote the release of heavy metals in mining-associated habitats and survive in high concentrations of heavy metals. Functions of glutathione reductase (GR) in cell defense against reactive oxygen species caused by heavy metals have been elucidated in some eukaryotic cells and bacteria; however, no information is available in A. caldus. In this research, the methods of bioinformatics, gene expression, GR activity assays were used to detect and characterize the glutathione reductase gene from the A. caldus MTH-04 strain. Then, A. caldus gr knockout mutant and gr overexpression strain were constructed, and the heavy metal tolerant properties and transcriptional levels of ROS related genes of them were compared to study the function of GR. The results showed that, a putative gr gene F0726_RS04210 was detected in the genome of A. caldus MTH-04. The purified recombinant protein of F0726_RS04210 showed remarkable GR activity at optimal pH 7.0 and 30°C using in vitro assay. The evolutionary relationship of GR from A. caldus MTH-04 was close to that from Escherichia coli K12. Gene knockout or overexpression of gr in A. caldus did not affect the growth rate on S0 medium, suggesting that GR did not play a key role in the activation of sulfur. Deletion of gr resulted in increased sensitivity to heavy metals (Cu2+ and Zn2+) in A. caldus, and the gr overexpression strain showed enhanced tolerance to heavy metals. Furthermore, transcription analysis also revealed strong correlations between GR and the antioxidant pathway. The above results suggest that GR can play an important role in heavy metal tolerance in A. caldus.

Negligible emissions and highly efficient recovery of Mo, V, and Al from spent hydroprocessing catalysts through alkaline leaching and solvent extraction

Spent petroleum hydroprocessing catalysts (HPCs) are considered hazardous waste due to their high content of heavy metals and organic pollutants, posing a risk of environmental pollution and significant loss of valuable metals if not properly disposed. This study aimed to characterize the spent HPCs using optical microscopy, SEM-EDS, XRF, C & S analyzer, XRD, and XPS. Additionally, the effectiveness of six organic solvents in removing the black oil covering the surface of spent HPCs was investigated. Furthermore, the recovery of Mo, V, and Al from the spent HPCs was examined through stepwise leaching using NaOH + NaClO2 and NaOH, followed by the separation of Mo, V, and Al via selective precipitation of Al and solvent extraction using Aliquat 336. The results indicated that toluene and tetrahydrofuran exhibited the highest efficiency in removing the black oil. Under the optimized oxidizing alkaline leaching conditions (0.09 g/mL NaOH + 0.05 g/mL NaClO2, 90 °C, 1 h), Mo, V, and Al achieved leaching efficiencies of 99.9 %, 99.9 %, and 20.1 %, respectively. Subsequently, Al in the residue was recovered through leaching with NaOH, resulting in a total leaching efficiency of 95 % under the optimized alkaline leaching conditions (0.12 g/mL NaOH, 180 °C, 3 h). The Al in both leaching solutions was precipitated by adjusting the pH to 8.60. For the subsequent Mo/V separation, the best conditions involved either four stages of counter-current extraction or two stages of cross-current extraction using a solution of 21 wt% Aliquat 336 dissolved in a mixture of kerosene and isooctanol (volume ratio 9:1) at a pH of 8.60. Finally, a hydrometallurgical flowchart for the recovery of Mo, V, and Al from spent HPCs was proposed.

Heavy Metals and Microbial Diversity: A Comparative Analysis of Rivers Swat and Kabul

Water contamination with heavy metals seriously affects water and sediment quality and may affect the aquatic biota. This study assessed the impact of heavy metals on the morphological characteristics of aquatic microorganisms in potentially contaminated water. Different physicochemical parameters and heavy metals contents were analyzed for toxicological assessment along with microbial diversity in the rivers Swat and Kabul. The pH of River Swat water was neutral to slightly alkaline, while River Kabul was neutral to slightly acidic. The results showed substantial variations in heavy metal concentration across different sampling points. In both River Swat and River Kabul water samples, Cu and Zn concentrations were below the permissible limits for surface and drinking water qualities while the rest of the heavy metals exceeded the permissible limit with Cd being the most abundant heavy metal. Similarly, in sediment samples all the heavy metals were below the permissible limits except for Cd that exceeded the Environment Canada (EC) limits in River Swat and EC and NOVA limits in River Kabul. The rest of the heavy metals concentrations were within the permissible limits, with few exceptions. The results showed that in River Swat, most of the contamination was of geogenic origin, while the main source of contamination in River Kabul was anthropogenic. Results of microbial analysis showed that River Swat has more diversity than River Kabul, which may be due to the low contamination profile of River Swat. It was further observed that high heavy metal concentrations negatively impact the morphological characteristics of microorganisms. The heavy metals concentration and microbial diversity were closely related to each other.

Enhancing environmental monitoring: utilizing plant and soil assays to track pollution in a Turkish organized industrial zone

The aim of the current investigation was to determine the concentration of different metals in Mentha spicata L. subsp. tomentosa plants and soils in order to highlight the pollution level in a Turkish Organized Industrial Zone in Dilovasi District, in Kocaeli City. The concentration of metals in plant and soil samples were examined. When the soil values were examined, the highest cadmium, chromium, copper, iron, nickel, and lead levels were collected from the location which is hosting numerous industrial facilities. All elements except boron and copper, exceeded normal limits in the leaf samples while cadmium, chromium, iron, nickel, lead, and zinc reached “toxic levels” in leaf samples. Heavy metals were accumulated in leaves more than rhizomes. Mineral element uptake and accumulation were affected from heavy metal amounts, especially in rhizomes. Although washing procedure notably reduced the concentration of some heavy metals in leaves samples, the reduced values were higher than acceptable levels in some locations of the district. According to the data, it may be said that the region, especially its industrialized parts are heavily polluted by heavy metals. Moreover, in the accordance with the fact that, the highest values of elements were determined in regions having considerable industrial activity such as metal and plastic processing facilities. Additionally, Mentha spicata plants exhibited higher heavy metal values in areas with high heavy metal content in the soil, and lower heavy metal values in areas with low heavy metal concentration. These findings indicate that Mentha spicata, a plant known for its medicinal and culinary uses, can be considered as an effective biomonitor for heavy metal pollution in the region. Consequently, constant inspection is required to prevent the excessive buildup of metals in the region and similar areas with comparable characteristics in terms of human life.

Evaluating the effects of geochemical and anthropogenic factors on the concentration and treatability of heavy metals in Awash River and Lake Beseka, Ethiopia: arsenic and molybdenum issues

In the Awash River basin (Ethiopia), massive urbanization and industrialization, driven by rapid development and human settlement, are detrimental to the environment and human health as pollutants such as heavy metals (HMs) find their way into water bodies without proper treatment. The purpose of this study was to assess the HMs content and pollution sources within the basin. In this context, a total of 205 samples were collected from 21 surface water sampling stations. Heavy metal concentrations were measured using the Perkin Elmer NexION 350 ICP-MS with inductively coupled plasma. Findings demonstrate that high levels of HMs, such as Al, Mn, Mo, As, V, Fe, and Ba were exhibited with the value of 1257 μg/L, 626.8 μg/L, 116.7 μg/L, 61.2 μg/L, 100.5 μg/L, 1082.7 μg/L, and 211.7 μg/L, respectively. Among 20 HMs analyzed, 20% of the parameters within the study area were above the WHO limit for drinking water; Al (157 μg/L), V (100.5 μg/L), Fe (1082.7 μg/L), Mn (626.8 μg/L), and Mo (103.8 μg/L) were exhibited at sites along the river system. Likewise, 57% of water samples showed high values of As at many stations down the river systems. In particular, high HM concentrations seen in the upper Awash are primarily controlled by anthropogenic activities such as untreated industrial, agricultural, and domestic discharges, while the high HM concentrations in the middle Awash samples were likely due to the influence from the Lake Beseka that has high HM concentrations due to geological process. In conclusion, securing potable water for the rapidly increasing population in Addis Ababa and in the watersheds of Awash is unsafe to sustain the environment and the human health.

Effect of ultrasound-assisted EDTA and citric acid washing on heavy metal removal, residual heavy metal mobility, and sewage sludge quality.

We investigated the effects of ultrasound-assisted ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) washing on heavy metal (HM) removal, residual HM mobility, and sewage sludge quality. EDTA and CA washing of sewage sludge successfully reduced the total concentration of HMs after one round of washing, but the mobility of residual HMs increased significantly. The eluate had a high concentration of HMs and nutrients (nitrogen, phosphorus, potassium, and total organic carbon), although the nutritional content of the sludge remained high. The three-phase ratio of the sludge after six rounds of washing by CA was closest to the ideal three-phase ratio, and the degree of influence on the physical structure of the soil after a land application was reduced, according to the fluctuation of generalized soil structure index (GSSI) and soil three-phase structure distance (STPSD) values. The results indicate that CA as an environmental-friendly washing agent can be the superior choice for sludge HM washing; single washing of sewage sludge may increase the mobility of residual HMs, so multiple washings should be considered for land application of sludge.

Stress induced by soil contamination with heavy metals and their effects on some biomarkers and DNA damage in maize plants at the vicinity of Ferronikel smelter in Drenas, Kosovo

The Ferronikel smelter in Drenas is one of the main industrial areas in the Kosovo and pollution by heavy metals causes serious threat for all living organisms on this area. The objective of this study was to determine the concentration of some heavy metals (Fe, Cu, Mn, Cr, Cd, Ni and Pb) in agricultural soils and in maize plants, and their potential toxic effects on this plant through some sensitive biochemical and molecular markers. Maize seedlings growth in nine soil samples from different locations of this area. The highest concentrations of heavy metals in soils and maize leaves were conducted close to the Ferronikel smelter, and in some locations, the nickel and chromium concertation in soils exceeded 800 mg kg−1. A significant effects of heavy metals induced toxicity resulted in the, build-up aminolevulinic acid and reduced activity of δ-aminolevulinic acid dehydratase, and chlorophyll content in the maize leaves. In general, maize seedlings growth in polluted locations showed an increase in nuclear DNA content and in G2M phase. We concluded that locations close to the smelter are affected by soil heavy metals pollution and these biochemical and molecular analysis would be a powerful ecotoxicological tool in biomonitoring of heavy metal pollution.

Co-disposal of hazardous waste incineration fly ash and bottom ash through alkaline-activation: Effects of added CaO on solidification of heavy metals

Hazardous waste incineration fly ash (HFA) and bottom ash (HBA) are considered hazardous due to their high concentrations of heavy metals, which drew much attention about their safe disposal. Geopolymers have emerged as promising materials for solidifying heavy metals. With HBA having relatively high content of aluminosilicates, it presents a potential opportunity to convert both HFA and HBA into geopolymer through alkali activation, thus effectively solidifying heavy metals. However, HBA is often regarded as having lower reactivity, necessitating the addition of reactive calcium (Ca) to enhance alkali activation. In this study, we investigated the impact of incorporating a small amount of CaO on heavy metal solidification in geopolymer. The results demonstrate that the addition of CaO can effectively reduce the leaching concentration of heavy metals in geopolymer when the HBA content exceeds 40 wt% and meets the limits specified by the Chinese standard (GB18598–2019). Characterization using transmission electron microscopy (TEM) and micromeritics instrument corp (MIP) reveals that the addition of CaO reduces the porosity of the geopolymer from 23.59 % to 14.30 %, and resulted in a more uniform distribution of hydration products on the particle surface. This enhanced distribution contributes to a stronger encapsulation effect, effectively enveloping and sealing heavy metal ions within HFA and HBA particles. Consequently, the geopolymer incorporating CaO in the HFA and HBA mixture is deemed suitable for the safe treatment mandated by GB18598–2019. This study offers valuable insights for the comprehensive disposal of these hazardous waste types.

Elucidating the Potential of Dye-Degrading Enterobacter cloacae ZA14 for Cultivation of Solanum lycopersicum Plants with Textile Effluents

The presence of textile effluents in water bodies is a matter of concern due to toxicity caused by textile dyes, associated heavy metals and salts. Endophytic bacteria have been reported to reduce the phytotoxicity of textile wastewater (TWW) and improve crop potential. The purpose of this study was to sequester dye-degrading endophytic bacteria with the ability to remediate textile effluents and promote tomato plant growth. Six strains showing the highest dye decolorization were screened from the dye decolorization assay. Selected strains also showed plant growth-promoting traits and improved tolerance to heavy metals and salt. The results revealed that Enterobacter cloacae ZA14 showed the highest decolorization (90%) using 200 mg L−1 of dye concentration, high minimum inhibitory concentration (MIC) of heavy metals and improved salt tolerance. In a sand culture experiment, the T4 (25% TWW (consisting of 25 mL TWW with 75 mL distilled water) + ZA14) treatment showed an increase in root length (9.3%), shoot length (5.5%), improved chlorophyll contents (7%), and membrane stability index (5%), whereas maximum oxidative stress was indicated by T10 (100% TWW) with an increase of 122% in MDA and 80% in H2O2 as compared to T1. An increase of 41% in ascorbate peroxidase (APX), 37% increase in sodium oxide dismutase (SOD), 27% in peroxidase (POD), and 24% in catalase (CAT) by T4 treatment showed the least production of antioxidants as compared to plants receiving 50%, 75% and 100% TWW along with ZA14 application. These results suggested that 25% TWW is beneficial for crop production with the use of an appropriate approach like Enterobacter cloacae ZA14 to mitigate textile effluents efficiently and to improve crop production.

Occurrence and Health Risk Assessment of Heavy Metals in Lychee (Litchi chinensis Sonn., Sapindaceae) Fruit Samples

This study aimed to assess the occurrence of eight heavy metals in lychee (Litchi chinensis Sonn.) fruit samples collected from orchards of the Dehradun and Haridwar districts in Uttarakhand, India. Lychee fruit samples were collected from ten (10) sampling locations from May to June 2023 and analyzed using inductively coupled plasma optical emission spectroscopy (ICP-OES). Results showed that lychee fruit samples showed varying levels of selected heavy metals, i.e., Cd (0.009–0.095 mg/kg), Cr (0.079–0.960 mg/kg), Cu (0.095–0.258 mg/kg), Fe (0.254–0.531 mg/kg), Pb (0.000–0.011 mg/kg), Mn (0.862–1.903 mg/kg), Ni (0.166–0.310 mg/kg), and Zn (0.076–0.149 mg/kg). It was observed that lychee fruit sampling sites near urban and industrial areas had higher concentrations of heavy metals as compared to those in rural and agricultural areas. In addition, principal component analysis (PCA) and clustered heatmap dendrogram results showed that several sites had significant similarities in terms of heavy metal availability. Overall, the levels of all heavy metals were below the safe limits as suggested by health risk studies. The selected indices such as daily intake of metals (DIM), health risk index (HRI), and target hazard quotient (THQ) did not exceed the standard limit which indicated consumption of lychee fruit was safe at all sampling sites. The results of this study emphasize the need to regularly monitor lychee heavy metal levels and implement sustainable agricultural and environmental practices to reduce contamination sources.

HEAVY METAL CONTENT IN WATER AND SEDIMENT OF SHRIMP FARMS OF SATKHIRA, BANGLADESH

Toxic contaminants moving along with runoff usually contaminates shrimp farms in most areas of Satkhira district, southwest Bangladesh. An investigation was carried out to assess the Physico-chemical properties and heavy metal concentration of sediments and water in shrimp farms from Satkhira district, southwest Bangladesh during December 2020 to March 2021. Twelve water and sediment samples were collected from six Ghers of two Upazilla e.g., Debhata and Assasuni of Satkhira. Physico-chemical attributes such as temperature, DO, BOD5, pH, TDS, EC, turbidity, salinity, HCO3-/CO3-, SO4-, NO3-, PO4- were estimated. The concentration attributes such as TDS (2280-5250 mg/l), EC (4380-9670 µs/cm), Turbidity (50.8-348 NTU), HCO3-/CO3- (219.6-445.3 mg/l), NO3- (0.3635-1.94 mg/l) were observed to be higher than the allowable standards recommended by WHO and FAO. Five trace metals such as chromium (Cr), cadmium (Cd) copper (Cu), lead (Pb) and Zinc (Zn), were measured in sediments and water by Atomic Absorption Spectrometer. The range of metal concentrations in sediment were as follows: Cr (1.95–3.43 mg/l), Zn (205.76-265.71 mg/kg), Cu (0.60–1.1mg/kg), Cd (3.8-4.1 mg/kg), and Pb (0.92-1.11mg/kg wet weight. The range of metal concentration in water were as follows: Cr (0.1-0.8 mg/l), Zn (0.003-0.34 mg/l), Cu (0.10-0.13 mg/l), Cd (0.07-0.08 mg/l), and Pb (0.23-0.34 mg/l). Higher concentrations of metal were recorded in most of the sediment and samples of water of the studied Ghers except Cr and Cu, those were below standard as prescribed by WHO and FAO. The concentration of Cu ranges from 0.602 to 1.113 mg/kg and 0.10 to 0.13 mg/l and range of Cr concentration were 1.95 to 3.43 mg/kg and 0.156 to 0.807 mg/l in sediment and water respectively. However, Cd, Zn and Pb were higher than the allowable standard as recommended by WHO and FAO. The higher heavy metal concentrations in water and sediment of shrimp Ghers suggest that shrimp could be contaminated by these heavy metals as well.

Heavy metals concentration in zooplankton (copepods) in the western Bay of Bengal.

Along the coastline, urbanisation and industrialization pose significant challenges to marine habitats and biodiversity. Most wastewater that reaches the marine environment contains toxic metals, which, as they are non-biodegradable, accumulate in the biota and enter the marine food chain. This study presents the concentration of nine heavy metals (Fe, Zn, Cu, Co, Cr, Mn, Ni, Pb, and Cd) in zooplankton (copepods) during the Spring Intermonsoon/Pre-Monsoon (April 2019) in the western Bay of Bengal (BoB). Higher Fe concentrations were found in copepods both nearshore (42,352µg/g) and offshore (9835µg/g). However, the relative amounts of heavy metals in copepods from 16 locations (eight nearshore and eight offshore) varied in the order of Fe > Zn > Cu > Co > Cr > Mn > Ni > Pb > Cd. The copepods in the nearshore locations had higher concentrations of heavy metals than those offshore. Compared to earlier data on heavy metals, particularly those that are physiologically non-essential and toxic, the current study demonstrates higher amounts of these metals in copepods in the inshore BoB [Ni (avg. 58.7 ± 5.5µg/g), Pb (avg. 25.6 ± 4.7µg/g), and Cd (avg. 16.4 ± 0.9µg/g)]. Considering the strong East India Coastal Currents in the western BoB, trace metal-concentrated copepods could be transported too far along the Indian coastline from the current study area.

Smokeless Tobacco Harbors Bacteria Involved in Biofilm Formation as Well as Salt and Heavy Metal Tolerance Activity.

In our previous culture-independent study on smokeless tobacco products, we have observed a strong positive correlation between several bacteria and genes involved in nitrate/nitrite reduction, biofilm formation, and pro-inflammation. Therefore, the present investigation was carried out to analyze the inhabitant bacterial population of the Indian ST products for assessing the health-associated risk attributes using culture-dependent approach. Traditional cultivation approaches recovered several bacterial isolates from commercial ST products on different culture media. A high colony formation unit (CFU) count was observed that ranged from 173 × 104 to 630.4 × 105 per gram of ST products. Of the 74 randomly selected and distinct bacterial isolates, 17 isolates showed a significantly enhanced growth (p-value < 0.05) in the presence of the aqueous tobacco extract. On biochemical characterization, these bacteria were identified as the member of Bacillus, Enterobacter, Micrococcus, Providencia, Serratia, Pantoea, Proteus, and Pseudomonas. Most of these bacteria also exhibited biofilm-forming activity, where eight bacterial isolates were identified for strong biofilm-forming action. 16S rRNA-based molecular characterization of these bacteria identified them as Bacillus subtilis, Bacillus paralicheniformis, Enterobacter sp., Serratia marcescens, Pantoea anthophila, and Enterobacter cloacae. Moreover, these bacteria also exhibited the potential to withstand high salt and heavy metal concentrations. The findings demonstrate that Indian ST products are heavily populated with wide bacterial species exhibiting potential in biofilm formation, heavy metal resistance, and salt tolerance.

Quantitative determination of heavy metal contaminants in edible soft tissue of clams, mussels, and oysters.

Aquatic environments are important sources of healthy and nutritious foods; however, clams, mussels, and oysters (the bivalves most consumed by humans) can pose considerable health risks to consumers if contaminated by heavy metals in polluted areas. These organisms can accumulate dangerously high concentrations of heavy metals (e.g., Cd, Hg, Pb) in their soft tissues that can then be transferred to humans following ingestion. Monitoring contaminants in clams, mussels and oysters and their environments is critically important for global human health and food security, which requires reliable measurement of heavy-metal concentrations in the soft tissues. The aim of our present paper is to provide a review of how heavy metals are quantified in clams, mussels, and oysters. We do this by evaluating sample-preparation methods (i.e., tissue digestion / extraction and analyte preconcentration) and instrumental techniques (i.e., atomic, fluorescence and mass spectrometric methods, chromatography, neutron activation analysis and electrochemical sensors) that have been applied for this purpose to date. Application of these methods, their advantages, limitations, challenges and expected future directions are discussed.

Modification of phases evolution and heavy metal immobilization in alkali-activated MSWI FA by the incorporation of converter steel slag

Municipal solid waste incineration fly ash (MSWI FA) poses serious environmental concerns due to its high content of hazardous organics, heavy metals, and soluble salts. This study aimed to solidify the harmful components in MSWI FA by alkali activation and explore the influence of converter steel slag on the phase evolution. With the increase of curing time, the amount of C-(A)-S-H gel increased and its microstructure shifted to a high crystalline and crosslinked state, accompanied by the increase of Ca/Si ratio. The addition of steel slag was beneficial to the formation of C-(A)-S-H gel and enhanced its crystallinity and crosslinking degree. Compared with alkali-activated MSWI FA, NaCl and KCl content decreased more significantly with curing time and Friedel ’salts were found in the matrix modified by steel slag. The leaching toxicity of heavy metals in alkali-activated matrix was reduced as curing time increased. The increase of C-(A)-S-H gel content and changes of its microstructure were conducive to the stabilization of heavy metals and chlorides. The refinement of pore size and improvement of compressive strength contributed to the physical encapsulation of heavy metals and chlorides.

The first ecological contamination study of avian mercury and lead in southeast Iran, Hamun International Wetlands.

The concentrations of mercury (Hg) and lead (Pb) in feather samples of nine bird's species (n = 65) were determined from southeastern areas of Iran, Hamun International Wetlands. Hg concentrations were ranged from 0.40 to 3.00 mg/kg dry wt and from 0.38 to 1.76 mg/kg for primary and secondary feathers, respectively. Furthermore, Pb concentrations were ranged from 1.43 to 4.10 mg/kg and from 1.28 to 3.65 mg/kg for primary and secondary feathers, respectively. Deposition of metals varied significantly among the primary and secondary feathers of systematic category (families) for Hg and Pb (p < 0.001). It was found that there is a significant difference in feather Hg and Pb concentrations across species (p < 0.001) with highest concentrations in saker falcon (Falconidae) (Hg = 3.00 mg/kg and Pb = 4.10 mg/kg, primary feather) followed by little owl (Strigidae). Grey francolin (Phasianidae) contained the least amount of Hg (0.40 mg/kg) and Pb (1.43 mg/kg) in primary feather. The results showed that the highest concentrations of heavy metals were related to carnivores. Fish predators, omnivores, and insectivores were examined at the next level of metal concentration, with herbivores having the lowest concentrations of lead (1.43 mg/kg) and mercury (0.40 mg/kg). Birds with an open grasslands feeding strategy had the highest mercury and lead concentration. The average value for Pb was on the border of harmful effects (4 mg/kg). The results of this study indicate that mercury levels are lower than the threshold level for reproductive and behavioral harm (5 mg/kg).