Heavy Metal Concentrations in Water, Sediment, and Fish Species in Chashma Barrage, Indus River: A Comprehensive Health Risk Assessment.

The increasing levels of heavy metals in aquatic environments, driven by human activities, pose a critical threat to ecosystems' overall health and sustainability. This study investigates the bioaccumulation of heavy metals (Pb, Cu, Cr, and Cd) in water, sediment, and three fish species (Catla catla, Labeo rohita, Cirrhinus mrigala) of different feeding zones within Chashma Barrage, located in the Mianwali district of Punjab, Pakistan, on the Indus River. A comprehensive analysis, including an assessment of associated human health risks, was conducted. Thirty samples from all three sites for each fish species, with an average body weight of 160 ± 32 g, were collected from Chashma Barrage. Water quality parameters indicated suitability for fish growth and health. Heavy metal concentrations were determined using an atomic absorption spectrometer. Results indicated elevated levels of Cd, Cr, and Cu in sediment and Pb and Cd in water, surpassing WHO standard limits. Among the fish species, bottom feeder (C. mrigala) exhibited significantly (P < 0.05) higher heavy metal levels in its tissues (gills, liver, and muscle) compared to column feeder (L. rohita) and surface feeder (C. catla). Liver tissues across all species showed higher heavy metal bioaccumulation, followed by gills. Principal component analysis (PCA) revealed strong correlations among heavy metals in sediment, gills, muscle, and water in every fish species. However, the vector direction suggests that Cr was not correlated with other heavy metals in the system, indicating a different source. The human health risk analysis revealed lower EDI, THQ, and HI values (< 1) for the fish species, indicating no adverse health effects for the exposed population. The study emphasizes the bioaccumulation differences among fish species, underscoring the higher heavy metal concentrations in bottom feeder fish within Chashma Barrage.

Comprehensive index analysis approach for ecological and human health risk assessment of a tributary river in Bangladesh.

This study examined the water quality of the Turag River, an important tributary river in Dhaka, Bangladesh in terms of physicochemical characteristics and heavy metal contamination to assess the potential risks to both ecological systems and human health. The majority of the water samples complied with the acceptable limits established by the World Health Organization (WHO) for various parameters including pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), chemical oxygen demand (COD), sodium adsorption ratio (SAR), and magnesium adsorption ratio (MAR), except total hardness (TH). The sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), chloride (Cl-), fluoride (F-), nitrate (NO3 -), and sulfate (SO4 2-) levels in the water samples were found to be within acceptable ranges for most cases. Moreover, heavy metals including lead (Pb), cadmium (Cd), chromium (Cr), nickel (Ni), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), arsenic (As), selenium (Se), and mercury (Hg) were analyzed and their mean concentrations (µg/L) were found in the order of Fe (244.72 ± 214.35) > Mn (28.93 ± 29.64) > Zn (22.97 ± 10.93) > Cu (8.28 ± 5.99) > Hg (8.23 ± 6.58) > As (1.34 ± 0.39) > Ni (1.20 ± 0.38) > Cr (0.67 ± 0.85) > Pb (0.61 ± 0.72) > Se (0.42 ± 0.48) > Cd (0.13 ± 0.09) which were within the acceptable limit, except Hg. The cumulative effect of all heavy metals was assessed through the heavy metal pollution index (HPI), contamination degree (Cd), and nemerow pollution index (PN). The mean value of HPI (682.38 ± 525.68) crossed the critical index value of 100, indicating an elevated level of pollution. The mean value of Cd (8.763 ± 6.48) indicates a low-moderate-significant level of contamination due to an elevated level of Hg, and for the PN it was found 174.27 ± 146.66, indicating a high level of pollution due to high level of Fe. Ecological risk index (ERI) indicated low levels of risk for Pb, Cd, Cr, Ni, Fe, Mn, As, Se, Cu, and Zn but a significantly high risk for Hg. The water was classified as good to excellent based on its physicochemical properties (pH, EC, TDS, COD, DO, F-, Cl-, NO3 -, and SO4 2-) while it was deemed poor to unsuitable for heavy metals according to the water quality index (WQI). Among the carcinogenic constituents, As poses the greatest carcinogenic risk, particularly for children. The mean value of Cr, Mn, and As in the HQingestion for adult and child, and Cd, Hg for child exceeded the threshold value established by the United States Environmental Protection Agency (USEPA), while the HQdermal values remained below the maximum limit for all heavy metals. The value of HI at all locations exceeds the threshold of 1, as specified by USEPA. Principal component analysis (PCA) and cluster analysis revealed that the presence of heavy metals in the Turag River was mainly attributed to anthropogenic sources, including industrial effluent discharge from neighboring industries, domestic wastewater, and agricultural runoff containing agrochemicals from the surrounding lands.

Black shale bedrock control of soil heavy metal typical high geological background in China Loushao Basin: Pollution characteristics, source and Influence assessment based on spatial analysis.

During the process of black shale weathering, multiple heavy metal elements are concentrated in the soil, causing pollution. This study selected soil and black shale bedrock samples from high geological background areas to investigate the control of heavy metal element pollution by bedrock using spatial analysis. The research results indicate that the heavy metal content in black shale bedrock is extremely high, ranging from 2.3 to 13.1 times the background values of rock heavy metal elements. The heavy metal content in the soil formed through weathering is positively correlated with the bedrock, ranging from 1.1 to 21.3 times the background values. The coefficient of variation of rock samples ranges from 1.09 to 7.18, indicating significant variability.The analysis reveals that the control ability of pure rock over heavy metal elements is mainly moderate and high, accounting for over 70 %, with d being the most affected metal element. Except for As, the other seven elements exhibit strong spatial autocorrelation, showing distinct regional distribution characteristics. The soil elements demonstrate high homogeneity, with heavy metal elements from black shale bedrock primarily released through weathering serving as the main source of these elements.

Soil heavy metal pollution promotes extracellular enzyme production by mediating microbial community structure during vegetation restoration of metallic tailing reservoir.

Vegetation restoration in metallic tailing reservoirs is imperative to restore the post-mining degraded ecosystems. Extracellular enzymes determine microbial resource acquisition in soils, yet the mechanisms controlling the enzyme activity and stoichiometry during vegetation restoration in metallic tailing reservoirs remain elusive. Here, we investigated the variations and drivers of C-, N- and P-acquiring enzymes together with microbial community along a 50-year vegetation restoration chronosequence in the China's largest vanadium titano-magnetite tailing reservoir. We found a parabolic pattern in the enzyme activity and efficiency along the chronosequence, peaking at the middle restoration stage (∼30 years) with approximately six-fold increase relative to the initial 1-year site. The enzyme ratios of C:P and N:P decreased by 33 % and 68 % along the chronosequence, respectively, indicating a higher microbial demand of C and N at the early stage and a higher demand of P at the later stage. Soil nutrients directly determined the enzyme activities and stoichiometry, whereas microbial biomass and community structure regulated the temporal pattern of the enzyme efficiency. Surprisingly, increased heavy metal pollution imposed a positive effect on the enzyme efficiency indirectly by altering microbial community structure. This was evidenced by the increased microbial diversity and the conversion of copiotrophic to oligotrophic and stress-tolerant taxa along the chronosequence. Our findings provide new insights into microbial functioning in soil nutrient dynamics during vegetation restoration under increasing heavy metal pollution.

Tanning wastewater restructured nitrogen-transforming bacteria communities and promoted N2O emissions in receiving river riparian sediments.

Physicochemical and toxicological characterization of leather tanning wastewater has been widely documented. However, few reports have examined the response of denitrification N2 and N2O emissions in riparian sediments of tannery wastewater-receiving rivers. In this study, 15N-nitrate labeling was used to reveal the effects of tanning wastewater on denitrification N2 and N2O emission in a wastewater-receiving river (the old Mang River, OMR). OMR riparian sediments were highly polluted with total organic carbon (93.39 mg/kg), total nitrogen (5.00 g/kg) and heavy metals; specifically, Cr, Zn, Cd, and Pb were found at concentrations 47.3, 5.8, 1.6, 4.3, and 2.8 times that in a nearby parallel river without tanning wastewater input (the new Mang River, NMR), respectively. The denitrification N2 emission rates (0.0015 nmol N · g-1 h-1) of OMR riparian sediments were significantly reduced by 2.5 times compared with those from the NMR (p < 0.05), but the N2O emission rates (0.31 nmol N · g-1 h-1) were significantly increased (4.1 times, p < 0.05). Although the dominant nitrogen-transforming bacteria phylum was Proteobacteria in the riparian sediments of both rivers, 11 nitrogen-transforming bacteria genera in the OMR were found to be significantly enriched; five of these were related to pollutant degradation based on linear discriminant analysis (LDA >3). The average activity of the electron transport system in the OMR was 6.3 times lower than that of the NMR (p < 0.05). Among pollution factors, heavy metal complex pollution was the dominant factor driving variations in N2O emissions, microbial community structure, and electron transport system activity. These results provide a new understanding and reference for the treatment of tanning wastewater-receiving rivers.

The accumulation of cadmium and lead in wheat grains is primarily determined by the soil-reducible cadmium level during wheat tillering.

The significant increase in cadmium (Cd) and lead (Pb) pollution in agricultural soil has greatly heightened environmental contamination issues and the risk of human diseases. However, the mechanisms underlying the transformation of Cd and Pb in soil as well as the influencing factors during their accumulation in crop grains remain unclear. Based on the analysis of the distribution trend of Cd and Pb in soil during the growth and development stages of wheat (tillering, filling, and maturity) in alkaline heavy metal-polluted farmland in northern China, this study investigated the response mechanism of soil heavy metal form transformation to soil physicochemical properties, and elucidated the main determining periods and influencing factors for Cd and Pb enrichment in wheat grains. The results showed that an increase in CEC and SOM levels, along with a decrease in pH level, contributed to enhancing the bioavailability of Cd in the soil. This effect was particularly evident during the tillering stage and grain filling stage of wheat. Nevertheless, the effects of soil physicochemical properties on bioavailable Pb was opposite to that on bioavailable Cd. The enrichment of Cd and Pb in grain was significantly influenced by soil pH (r = -0.786, p < 0.01), SOM (r = 0.807, p < 0.01), K (r = -0.730, p < 0.01), AK (r = 0.474, p = 0.019), and AP (r = -0.487, p = 0.016). The reducible form of Cd in soil during the wheat tillering stage was identified as the primary factor contributing to the accumulation of Cd and Pb in wheat grains, with a significant contribution rate of 84.5%. This study provides a greater scientific evidence for the management and risk control of heavy metal pollution in alkaline farmland.

Gender-specific responses in gene expression of Nile tilapia (Oreochromis niloticus) to heavy metal pollution in different aquatic habitats.

Monitoring heavy metal accumulation is essential for assessing the viability of aquatic ecosystems. Our methodology involved integrating analysis of immunological, stress, inflammatory, and growth-related gene expression in male and female Nile tilapia with on-site recordings of physicochemical parameters. Additionally, we assessed the effect of different physicochemical parameters on heavy metal bioavailability and residual concentration in fish and water. Samples of fish and water were gathered from three different localities: Lake Brullus, a brackish lake sited in northern Egypt; Lake Nasser, an artificial freshwater reservoir located in southern Egypt; and El-Qanater El-Khayria, a middle-freshwater location belonging to the Rashid branch of the river Nile. The assessment of heavy metal residues (Fe, Cu, Zn, Mn, and Ni) revealed that their concentrations were higher in fish specimens compared to their counterparts in water (except for Ni). In addition, Lake Brullus emerges as the most polluted area, exhibiting elevated levels of heavy metals concentrations in water and fish specimens. In contrast, Lake Nasser showed the least degree of heavy metals pollution. Gene expression analysis revealed gender-specific responses to heavy metal exposure at the three investigated water bodies. The expression of hepatic antioxidant genes (GST and MT) and inflammatory-related genes (CC-chemokine and TNFα) increased in males compared to females. In females, the immune and pro-inflammatory-related genes (IgM and CXC2-chemokine) transcripts were upregulated. Additionally, growth-related genes were downregulated in both Lake Brullus and El-Qanater; on the contrary, fish samples from Lake Nasser exhibited a normal expression pattern of growth-related genes. Stress-related genes (HSP70 and HSP27) showed significant downregulation in gills of both genders from Lake Brullus. The minimal presence of heavy metal contaminants in Lake Nasser seems to endorse the normal patterns of gene expression across all gene categories. A potential gender-specific gene expression response towards pollution was noticed in genes associated with inflammation and antioxidant activities. This highlights the importance of considering gender-related responses in future environmental assessments.

Peptides Used for Heavy Metal Remediation: A Promising Approach.

In recent years, heavy metal pollution has become increasingly prominent, severely damaging ecosystems and biodiversity, and posing a serious threat to human health. However, the results of current methods for heavy metal restoration are not satisfactory, so it is urgent to find a new and effective method. Peptides are the units that make up proteins, with small molecular weights and strong biological activities. They can effectively repair proteins by forming complexes, reducing heavy metal ions, activating the plant's antioxidant defense system, and promoting the growth and metabolism of microorganisms. Peptides show great potential for the remediation of heavy metal contamination due to their special structure and properties. This paper reviews the research progress in recent years on the use of peptides to remediate heavy metal pollution, describes the mechanisms and applications of remediation, and provides references for the remediation of heavy metal pollution.

A novel and recyclable silica gel-modified biochar to remove cadmium from wastewater: Model application and mechanism exploration.

Water pollution caused by heavy metals is a major environmental problem, threatening water production, food safety, and human health. Cadmium (Cd) pollution is particularly serious because of food-chain biomagnification at toxic concentrations. Modified biochar is promising for heavy metal removal; however, efficient adsorbents for Cd removal are lacking. In the present study, a novel adsorbent, silica gel-modified biochar (SGB), was prepared and applied to treat sewage polluted by Cd. Through the batch adsorption experiments, it is known that SGB possessed outstanding Cd removal ability and recycleability. Furthermore, the adsorption behavior and mechanisms were analyzed by the application of kinetic and isotherm models. The maximum Cd2+ adsorption capacity of SGB was 38.08 mg g-1, and after five recycling processes, the Cd2+ removal rate was still 86.89 %. When the pH of the solution was 7.0, SGB showed the strongest Cd2+ adsorption capacity (29.06 mg g-1). When competitive ions existed, biochar also had high Cd removal efficiency, although the effect of Pb2+ was greater than those of Cu2+ and Zn2+, indicating that SGB was applicable to complex polluted water. Additionally, the main Cd2+ adsorption mechanisms by SGB were electrostatic interactions, π-π interactions, complexation, and co-precipitation. These results showed that SGB can effectively treat Cd-contaminated wastewater as a new adsorbent.

Integrated physiological, biochemical, and transcriptomic analyses of Bruguiera gymnorhiza leaves under long-term copper stress: Stomatal size, wax crystals and composition.

Copper (Cu) is a necessary mineral nutrient for plant growth and development and is involved in several morphological, physiological, and biochemical processes; however, high concentrations of Cu can negatively impact these processes. The role of stomata in responding to various biotic and abiotic stimuli has not been studied in Bruguiera gymnorhiza, particularly in terms of their coordinated interactions at the molecular, physiological, and biochemical levels. Moreover, numerous plants employ strategies such as the presence of thick waxy cuticles on their leaf epidermis and the closing of stomata to reduce water loss. Thus, this study investigates the accumulation of Cu in B. gymnorhiza and its effect on leaf morphology and the molecular response under different Cu treatments (0, 200, and 400 mg L⁻¹, Cu0, Cu200, and Cu400, respectively) during a two years stress period. The results show that Cu stress affected accumulation and transport, increased the activities of peroxidase and ascorbate peroxidase, concentrations of soluble sugar, proline, and H2O2, and decreased the activity of catalase and content of malondialdehyde. Also, Cu-induced stress decreased the uptake of phosphorus and nitrogen and inhibited plant photosynthesis, which consequently led to reduced plant growth. Scanning electron microscopy combined with gas chromatography-mass spectrometry showed that B. gymnorhiza leaves had higher wax crystals and compositions under increased Cu stress, which forced the leaf's stomata to be closed. Also, the contents of alkanes, alcohols, primary alcohol levels (C26:0, C28:0, C30:0, and C32:0), n-Alkanes (C29 and C30), and other wax loads were significantly higher, while fatty acid (C12, C16, and C18) was lower in Cu200 and Cu400 compared to Cu0. Furthermore, the transcriptomic analyses revealed 1240 (771 up- and 469 downregulated), 1000 (723 up- and 277 down-regulated), and 1476 (808 up- and 668 downregulated) differentially expressed genes in Cu0 vs Cu200, Cu0 vs Cu400, and Cu200 vs Cu400, respectively. RNA-seq analyses showed that Cu mainly affected eight pathways, including photosynthesis, cutin, suberin, and wax biosynthesis. This study provides a reference for understanding mangrove response to heavy metal stress and developing novel management practices.

Investigation of heavy metals uptake in root-shoot of native plant species adjoining wastewater channels.

Metal pollution in water, soil, and vegetation is an emerging environmental issue. Therefore, this study investigated the abundance of heavy metals (HMs) within roots and shoots of native plant species i.e., Bromus pectinatus, Cynodon dactylon, Poa annua, Euphorbia heliscopa, Anagallis arvensis, and Stellaria media grown in the adjoining area of municipal wastewater channels of a Pakistani city of Abbottabad. HMs concentrations (mg L-1) in municipal wastewater were: chromium (Cr) (0.55) > nickel (Ni) (0.09) > lead (Pb) (0.07) > cadmium (Cd) (0.03). Accumulation of HMs in both roots and shoots of plant species varied as B. pectinatus > C. dactylon > P. annua > E. heliscopa > A. arvensis > S. media. Irrespective of the plant species, roots exhibited higher concentrations of HMs than shoots. Higher amount of Cr (131.70 mg kg-1) was detected in the roots of B. pectinatus and the lowest amount (81 mg kg-1) in A. arvensis, Highest Cd concentration was found in the shoot of B. pectinatus and the lowest in the E. heliscopa. The highest concentration of Ni was found in the roots of S. media (37.40 mg kg-1) and the shoot of C. dactylon (15.70 mg kg-1) whereas the lowest Ni concentration was achieved in the roots of A. arvensis (12.10 mg kg-1) and the shoot of E. heliscopa (5.90 mg kg-1). The concentration of HMs in individual plant species was less than 1000 mg kg-1. Considering the higher values (> 1) of biological concentration factor (BCF), biological accumulation co-efficient (BAC), and translocation factor (TF), B. pectinatus and S. media species showed greater potential for HMs accumulation than other species. Therefore, these plants might be helpful for the remediation of HM-contaminated soil.

The coupling of sulfide and Fe-Mn mineral promotes the migration of lead and zinc in the redox cycle of high pH floodplain soils.

In this study, we investigated the impact of fluctuating water levels on the distribution of lead (Pb) and zinc (Zn) in soil and sediments at a historical Pb-Zn smelting site along the Xiangjiang River. Despite the high pH levels (7 to 11) in the study area, which generally inhibits heavy metal solubility, we found that regular changes in water levels still affect Pb-Zn movement. Soil analysis revealed distinct redox zones within the unconfined aquifer, as shown by the variable Fe/Mn and Ce/Ce* ratios. Advanced techniques such as Mn K-edge XAFS, Mössbauer spectroscopy, and TOF-SIMS indicated persistent Fe-Mn redox cycling and highlighted the presence of Pb and Zn-rich manganese oxides near sulfur-bearing minerals. These findings suggest that acidic microzones produced by the oxidation of sulfur-bearing minerals become "refuges" for microbial and heavy metal activity. Considering that sulfur-containing minerals are widespread waste types in nonferrous metal smelting sites, these findings are instructive for a better understanding of the transformation mechanisms of heavy metal ions in nonferrous metal smelting-polluted environments and for guiding pollution remediation strategies.

Pollution Characteristics and Risk Assessment of Heavy Metals in the Sediments of the Inflow Rivers of Dianchi Lake, China.

To explore the contamination status and identify the source of the heavy metals in the sediments in the major inflow rivers of Dianchi Lake in China, sediment samples were collected and analyzed. Specifically, the distribution, source, water quality, and health risk assessment of the heavy metals were analyzed using correlation analysis (CA), principal component analysis (PCA), the heavy metal contamination factor (Cf), the pollution load index (PLI), and the potential ecological risk index (PERI). Additionally, the chemical fractions were analyzed for mobility characteristics. The results indicate that the average concentration of the heavy metals in the sediment ranked in the descending order of Zn > Cr > Cu > Pb > As > Ni > Cd > Hg, and most of the elements existed in less-mobile forms. The Cfwas in the order of Hg > Zn > Cd > As > Pb > Cr > Ni; the accumulation of Hg, Zn, Cd, and As was obvious. Although the spatial variability of the heavy metal contents was pronounced, the synthetical evaluation index of the PLI and PERI both reached a high pollution level. The PCA and CA results indicate that industrial, transportation, and agricultural emissions were the dominant factors causing heavy metal pollution. These results provide important data for improving water resource management efficiency and heavy metal pollution prevention in Dianchi Lake.

A comparative study of the risk assessment and heavy metal contamination of coastal sediments in the Red sea, Egypt, between the cities of El-Quseir and Safaga.

This study aimed to assess the influence of pollution on the quality of sediments and the risks associated with El-Qusier and Safaga Cities, Red Sea, Egypt, during 2021, divided into four sectors, using multiple pollution indices. To achieve that, we evaluated the metal pollution index (MPI), contamination factor (Cf), pollution load index (PLI), contamination security index (CSI), and anthropogenicity (Anp%). Moreover, carcinogenic and non-carcinogenic risks are used for human health hazards. Results indicated that Mn and Fe recorded the highest concentrations, whereas Cd had the lowest. El-Quseir City sediments were found the following metal ions: Fe > Mn > Ni > Zn > Cu > Co > Pb > Cd, where the order in the Safaga City was: Fe > Mn > Zn > Ni > Cu > Pb > Co > Cd. MPI > 1, this is alarming in the study area due to heavy metal pollution. In addition, Cf < 1 in all metals except Cd with contamination degree CD ranged from low to considerable contamination in El-Qusier city. In contrast, contamination ranged from significant to very high in Safaga city. PLI < 1 is lower than the reference at all monitored stations. CSI values ranged from relatively low to moderate. Besides Cd, data reflect each element's low environmental danger (EriMe40). This study's risk index (RI) is low to moderate in Sector 1 and high to extremely high in Sector 2. HQ and HI index < 1 means it is safe for human health in order: HI ingestion > HI dermal. CSR for different pathways was recorded as dermal > ingestion, in which total CSR for all paths is considered harmful, and the cancer risk is troublesome and higher than the reference ranges of 1 × 10-6-1 × 10-4. In conclusion, the examined heavy metals provide environmental hazards across the assessed locations.

Assessment of water quality using entropy-weighted quality index, statistical methods and electrical resistivity tomography, Moti village, northern Pakistan.

In this study, twenty-two water samples were collected from boreholes (BH), and streams to evaluate drinking water quality, its distribution, identification of contamination sources and apportionment for Moti village, northern Pakistan. An atomic absorption spectrophotometer (AAS) is utilized to determine the level of heavy metals in water such as arsenic (As), zinc (Zn), lead (Pb), copper (Cu), cadmium (Cd), manganese (Mn), and ferrous (Fe). Groundwater chemistry and its quantitative driving factors were further explored using multivariate statistical methods, Principal Component Analysis (PCA) and Positive Matrix Factorization (PMF) models. Finally, a total of eight electrical resistivity tomographs (ERTs) were acquired across i) the highly contaminated streams; ii) the villages far away from contaminated streams; and iii) across the freshwater stream. In the Moti village, the mean levels (mg/l) of heavy metals in water samples were 7.2465 (As), 0.4971 (Zn), 0.5056 (Pb), 0.0422 (Cu), 0.0279 (Cd), 0.1579 (Mn), and 0.9253 (Fe) that exceeded the permissible limit for drinking water (such as 0.010 for As and Pb, 3.0 for Zn, 0.003 for Cd and 0.3 for Fe) established by the World Health Organization (WHO, 2008). The average entropy weighted water quality index (EWQI) of 200, heavy metal pollution index (HPI) of 175, heavy metal evaluation index (HEI) of 1.6 values reveal inferior water quality in the study area. Human health risk assessment, consisting of hazard quotient (HQ) and hazard index (HI), exceeded the risk threshold (>1),indicating prevention of groundwater usage. Results obtained from the PCA and PMF models indicated anthropogenic sources (i.e. industrial and solid waste) responsible for the high concentration of heavy metals in the surface and groundwater. The ERTs imaged the subsurface down to about 40 m depths and show the least resistivity values (<11 Ωm) for subsurface layers that are highly contaminated. However, the ERTs revealed relatively high resistivity values for subsurface layers containing fresh or less contaminated water. Filtering and continuous monitoring of the quality of drinking water in the village are highly recommended.

Heavy metal accumulation analysis using bivalve, sponge, sea urchin, and gastropod species as bioindicators.

A comparative assessment of heavy metal accumulation potential in four distinct marine benthic bioindicators: the bivalve Perna perna, the sponge Callyspongia fibrosa, the sea urchin Tripneustes gratilla, and the gastropod Purpura bufo were conducted. These organisms were collected from the same location, and the concentration of ten heavy metals was analyzed in water, sediment and various body parts of the organisms. The bioaccumulation potential was evaluated using the bio-water accumulation factor and bio-sediment accumulation factor. There was significant variation in the bioaccumulation potential of each organism with respect to different metals. The sponge proved to be a reliable indicator of Cd with a highest concentration of 2.60 µg/g. Sea urchin accumulated high concentrations of Cr (16.98 µg/g) and Pb (4.80 µg/g), whereas Cu was predominant (21.05 µg/g) in gastropod, followed by bivalve (17.67 µg/g). The concentration of metals in hard parts was found to be lower than in the tissues.

Mechanistic investigation of Pb2+ adsorption on biochar modified with sodium alginate composite zeolitic imidazolate framework-8.

For the serious situation of heavy metal pollution, the use of cheap, clean, and efficient biochar to immobilize heavy metals is a good treatment method. In this paper, SA@ZIF-8/BC was prepared for the adsorption of Pb2+ in solution using sodium alginate (SA) and zeolitic imidazolate framework-8 (ZIF-8) modified corn cob biochar. The results showed that the specific surface area of modified biochar was greatly improved, with good adsorption capacity for Pb2+, strong anti-interference ability, and good economy. At the optimal adsorption pH of 5, the adsorption model of Pb2+ by SA@ZIF-8/BC was more consistent with the pseudo-second-order kinetic model and Langmuir isotherm model. This indicates that the adsorption of Pb2+ by SA@ZIF-8/BC is chemisorption and monolayer adsorption. The maximum adsorption of modified biochar was 300 mg g-1, which was 2.38 times higher than that of before modified BC (126 mg g-1). The shift in binding energy of functional groups before and after adsorption of SA@ZIF-8/BC was studied by XPS, and it was found that hydroxyl and carboxyl groups played an important role in the adsorption of Pb2+. It was demonstrated that this novel adsorbent can be effectively used for the treatment of Pb pollution in wastewater.

Spatial distribution characteristics and pollution evaluation of soil heavy metals in Wulongdong National Forest Park.

To scrutinize the spatial distribution attributes of soil heavy metal content and discern its pollution status within the expanse of Wulongdong National Forest Park, a meticulous investigation is imperative. Three altitude gradients of 900, 1000, and 1069 m were selected on the shady and sunny slopes of Wulongdong National Forest Park, and a total of 300 soil sample points were collected. Soil samples were collected in layers, and the contents of seven soil heavy metal elements, Cr, Cd, Hg, Ni, Se, As, and Pb, were measured. With regard to the national soil element background values, the single factor index method, Nemerow index method, and pollution load index were employed to undertake a thorough assessment of soil heavy metal pollution. (1) The contents of heavy metal elements Cr, Se, As, and Pb in the 0-20 cm soil layer of Wulongdong National Forest Park are lower than the national soil element background value and the Henan soil element background value; the Cd and Hg contents exceed the national soil element background value. The value and Henan soil element background value are 2.2 times and 2.92 times the national soil element background value, and 2.75 times and 9.5 times the Henan soil element background value respectively; Ni content is lower than the Henan soil element background value, but higher than the national soil element background value. The background value is 1.03 times its content. The coefficients of variation of the contents of seven heavy metal elements are all greater than 50%, among which Hg shows extreme variation, and the remaining six are highly variable. (2) In the same soil layer, the Cr and As contents are lower on sunny slopes than on shady slopes, and the contents of Pb, Ni, and Hg are generally higher on sunny slopes than on shady slopes. On sunny slopes, the contents of As, Cd, and Hg decrease with increasing altitude, and the Se content increases with increasing altitude; while on shady slopes, the contents of Cr, Se, and As decrease with increasing altitude, and Pb and Hg content increase with the increase of altitude; the content of heavy metal element As increases with the deepening of the soil layer on shady slopes, and the Hg content decreases with the deepening of the soil layer on sunny slopes. The contents of other heavy metal elements have no obvious regularity among different slope directions, altitudes and soil layers. (3) The single factor index evaluation results show that in the 0 ~ 20c soil layer and on the sunny slope, Hg is heavily polluted, Cd is moderately polluted, Ni is lightly polluted, and Cr, Se, As, and Pb are all non-polluted; On the shady slope, Cd and Hg are moderately polluted, and the other five heavy metal elements are in a non-polluting state. (4) The Nemerow index method evaluation results show that in the 0 ~ 20 cm soil layer, the soil on sunny slopes is significantly more polluted by heavy metals than on shady slopes, and the main pollutants are Ni, Cd and Hg. (5) In the 0 ~ 20 cm soil layer of Wulongdong National Forest Park, the three heavy metal elements Ni, Cd and Hg have reached pollution levels, of which Ni is slightly polluted, Cd and Hg are moderately or above polluted; the sunny slope soil is slightly polluted. Heavy metal pollution, no heavy metal pollution on shady slopes.

Heavy metal induced shifts in microbial community composition and interactions with dissolved organic matter in coastal sediments.

Heavy metals can impact the structure and function of coastal sediment. The dissolved organic matter (DOM) pool plays an important role in determining both the heavy metal toxicity and microbial community composition in coastal sediments. However, how heavy metals affect the interactions between microbial communities and DOM remains unclear. Here, we investigated the influence of heavy metals on the microbial community structure (including bacteria and archaea) and DOM composition in surface sediments of Beibu Gulf, China. Our results revealed firstly that chromium, zinc, cadmium, and lead were the heavy metals contributing to pollution in our studied area. Furthermore, the DOM chemical composition was distinctly different in the contaminated area from the uncontaminated area, characterized by a higher average O/C ratio and increased prevalence of carboxyl-rich alicyclic molecules (CRAM) and highly unsaturated compounds (HUC). This indicates that DOM in the contaminated area was more recalcitrant compared to the uncontaminated area. Except for differences in archaeal diversity between the two areas, there were no significant variations observed in the structure of archaea and bacteria, as well as the diversity of bacteria, across the two areas. Nevertheless, our co-occurrence network analysis revealed that the B2M28 and Euryarchaeota, dominating bacterial and archaeal groups in the contaminated area were strongly related to CRAM. The network analysis also unveiled correlations between active bacteria and elevated proportions of nitrogen-containing DOM molecules. In contrast, the archaea-DOM network exhibited strong associations with nitrogen- and sulfur-containing molecules. Collectively, these findings suggest that heavy metals indeed influence the interaction between microbial communities and DOM, potentially affecting the accumulation of recalcitrant compounds in coastal sediments.

Occurrence, distribution, and ecological risk assessment of heavy metals in Chao Phraya River, Thailand.

Understanding heavy metals in rivers is crucial, as their presence and distribution impact water quality, ecosystem health, and human well-being. This study examined the presence and levels of nine heavy metals (Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn) in 16 surface water samples along the Chao Phraya River, identifying Fe, Mn, Zn, and Cr as predominant metals. Although average concentrations in both rainy and dry seasons generally adhered to WHO guidelines, Mn exceeded these limits yet remained within Thailand's acceptable standards. Seasonal variations were observed in the Chao Phraya River, and Spearman's correlation coefficient analysis established significant associations between season and concentrations of heavy metals. The water quality index (WQI) demonstrated varied water quality statuses at each sampling point along the Chao Phraya River, indicating poor conditions during the rainy season, further deteriorating to very poor conditions in the dry season. The hazard potential index (HPI) was employed to assess heavy metal contamination, revealing that during the dry season in the estuary area, the HPI value exceeded the critical threshold index, indicating the presence of heavy metal pollution in the water and unsuitable for consumption. Using the species sensitivity distribution model, an ecological risk assessment ranked the heavy metals' HC5 values as Pb > Zn > Cr > Cu > Hg > Cd > Ni, identifying nickel as the most detrimental and lead as the least toxic. Despite Cr and Zn showing a moderate risk, and Cu and Ni posing a high risk to aquatic organisms, the main contributors to ecological risk were identified as Cu, Ni, and Zn, suggesting a significant potential ecological risk in the Chao Phraya River's surface water. The results of this study provide fundamental insights that can direct future actions in preventing and managing heavy metal pollution in the river ecosystem.