Heavy Metals In Aquatic Environment Research Articles

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 ± 32g, 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.

Application of Membrane Separation Technology in Electroplating Wastewater Treatment and Resource Recovery: A Review

The rapid development of industry has led to the generation of a large amount of electroplating wastewater. The direct discharge of untreated electroplating wastewater may lead to the formation of toxic metal-organic complexes, which is a challenging problem for human health and the living environment of organisms. Due to the high solubility of heavy metals in aquatic environments and their easy absorption by organisms, effective treatment of electroplating wastewater is of great significance. The ultimate goal of electroplating wastewater treatment should be to recover metals and water from electroplating wastewater. In indoor experiments, pilot tests, and industrial applications of electroplating wastewater treatment, membrane treatment technology commonly used in wastewater terminal treatment has attracted great attention. Membrane treatment technology seems to be the most promising method for removing heavy metals and organic pollutants from electroplating wastewater. This article reviews the membrane treatment technologies for electroplating wastewater, introduces the advantages and disadvantages of various membranes in the treatment of electroplating wastewater, the removal efficiency of pollutant types, and their comparison. The focus is on the treatment effects of nano-filtration membrane, ultra-filtration membrane, micro-filtration membrane, reverse osmosis membrane, ceramic membrane, biofilm, etc., on electroplating wastewater. Compared with a single treatment method, the combination of different processes shows higher efficiency in removing various pollutants.

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

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

Highly Sensitive Whole-Cell Mercury Biosensors for Environmental Monitoring.

Whole-cell biosensors could serve as eco-friendly and cost-effective alternatives for detecting potentially toxic bioavailable heavy metals in aquatic environments. However, they often fail to meet practical requirements due to an insufficient limit of detection (LOD) and high background noise. In this study, we designed a synthetic genetic circuit specifically tailored for detecting ionic mercury, which we applied to environmental samples collected from artisanal gold mining sites in Peru. We developed two distinct versions of the biosensor, each utilizing a different reporter protein: a fluorescent biosensor (Mer-RFP) and a colorimetric biosensor (Mer-Blue). Mer-RFP enabled real-time monitoring of the culture's response to mercury samples using a plate reader, whereas Mer-Blue was analysed for colour accumulation at the endpoint using a specially designed, low-cost camera setup for harvested cell pellets. Both biosensors exhibited negligible baseline expression of their respective reporter proteins and responded specifically to HgBr2 in pure water. Mer-RFP demonstrated a linear detection range from 1 nM to 1 μM, whereas Mer-Blue showed a linear range from 2 nM to 125 nM. Our biosensors successfully detected a high concentration of ionic mercury in the reaction bucket where artisanal miners produce a mercury-gold amalgam. However, they did not detect ionic mercury in the water from active mining ponds, indicating a concentration lower than 3.2 nM Hg2+-a result consistent with chemical analysis quantitation. Furthermore, we discuss the potential of Mer-Blue as a practical and affordable monitoring tool, highlighting its stability, reliance on simple visual colorimetry, and the possibility of sensitivity expansion to organic mercury.

Simultaneous removal of ciprofloxacin and Cr (VI) from contaminated water by polymer-supported nanoscale zero-valent copper: Performance and mechanism

Coexistence of organic compounds and heavy metals in aquatic environments is a widespread problem. In this study, the applicability of resin-supported nano zero-valent copper (nZVC@D201) for the simultaneous removal of ciprofloxacin (CIP) and Cr (VI) was systematically investigated. nZVC with sizes of 10–20 nm was uniformly dispersed on the resin using the ion exchange-liquid phase reduction method. The CIP and Cr (VI) removal rates of the nZVC@D201 composite were 78.68% and 94.98%, respectively. Practicability experiments of nZVC@D201 exhibited high efficiency even after five cycles and a generalized removal capacity for different pollutants. Combined with electron spin resonance (ESR), free radical quenching experiments, X-ray photoelectron spectroscopy (XPS), and liquid chromatography-mass spectrometry (LC-MS), a possible reaction pathway and mechanism for CIP oxidation and Cr (VI) removal were proposed. Cr (VI) was removed through a comprehensive process including adsorption/coprecipitation and reduction, whereas CIP was effectively degraded by hydroxyl radicals (·OH) produced from the Fenton-like reactions, producing a series of intermediates. These results demonstrate that nZVC@D201 is a promising alternative composite for the simultaneous removal of Cr (VI) and the degradation of CIP from wastewater.

Comparison of the efficiency of traditional MICP and two-step MICP method for immobilizing heavy metals in aquatic environments

The application of the microbial-induced carbonate precipitation (MICP) method for remediating heavy metals (i.e., HMs) has recently garnered significant attention. Nevertheless, the inhibition of urease activity by toxic Cd2+, Pb2+, Zn2+, and Cu2+ poses a challenge for MICP-based remediation of HMs contamination. This study: (1) first performs the traditional MICP tests (in which the bacterial solution, urea solution, and HMs are mixed simultaneously), and investigates the toxic effect of HMs on the urease activity and the immobilization efficiency, (2) analyzes the toxicity and immobilization mechanism during the MICP process by combining the simulation and XRD tests, (3) conducts the two-step MICP tests (which initially mix the bacterial solution and urea solution to promote urea hydrolysis, then add the HMs solutions for HMs precipitation) to improve the immobilization efficiency. The tube experiments and simulations were investigated in the HMs concentration range from 1 to 10mM. Indicators including ammonium concentration, HMs concentrations, and pH were measured/ recorded during the tests. The results show that soluble HMs exhibit a concentration-dependent inhibition of urea hydrolysis during the traditional MICP process, resulting in a decreasing immobilization efficiency. The two-step MICP method can effectively immobilize almost the Cd2+ and Zn2+ when the initial urea hydrolysis period exceeds 1~2h. In addition, a high immobilization rate of over 90% can be achieved for Cu-contaminated solutions at the optimal first-step reaction time. Compared with the traditional MICP procedure, the effective two-step MICP method exhibits more promising application prospects for the immobilization of soluble HMs in aquatic environments.

Risk Assessment and Sources Apportionment of Toxic Metals in Two Commonly Consumed Fishes from a Subtropical Estuarine Wetland System.

The widespread occurrence of heavy metals in aquatic environments, resulting in their bioaccumulation within aquatic organisms like fish, presents potential hazards to human health. This study investigates the concentrations of five toxic heavy metals (Pb, Hg, Zn, Cu, and Cr) and their potential health implications in two economically important fish species (Otolithoides pama and Labeo bata) from a subtropical estuarine wetland system (Feni estuary, Bangladesh). Muscle and gill samples from 36 individual fish were analyzed using energy dispersive X-ray fluorescence (EDXRF). The results revealed that the average quantities of heavy metals in both fishes' muscle followed the declining order of Zn (109.41-119.93 mg/kg) > Cu (45.52-65.43 mg/kg) > Hg (1.25-1.39 mg/kg) > Pb (0.68-1.12 mg/kg) > Cr (0.31-5.82 mg/kg). Furthermore, Zn was found to be present in the highest concentration within the gills of both species. While the levels of Cu, Zn, and Cr in the fish muscle were deemed acceptable for human consumption, the concentrations of Pb and Hg exceeded the permissible limits (>0.5 mg/kg) for human consumption. Different risk indices, including estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI), and carcinogenic or target risk (TR), revealed mixed and varying degrees of potential threat to human health. According to the EDI values, individuals consuming these fish may face health risks as the levels of Zn, Cu, and Cr in the muscle are either very close to or exceed the maximum tolerable daily intake (MTDI) threshold. Nevertheless, the THQ and HI values suggested that both species remained suitable for human consumption, as indicated by THQ (<1) and HI (<1) values. Carcinogenic risk values for Pb, Cr, and Zn all remained within permissible limits, with TR values falling below the range of (10-6 to 10-4), except for Zn, which exceeded it (>10-4). The correlation matrix and multivariate principal component analysis (PCA) findings revealed that Pb and Cr primarily stemmed from natural geological backgrounds, whereas Zn, Cu, and Hg were attributed to human-induced sources such as agricultural chemicals, silver nanoparticles, antimicrobial substances, and metallic plating. Given the significance of fish as a crucial and nutritious element of a balanced diet, it is essential to maintain consistent monitoring and regulation of the levels and origins of heavy metals found within it.

Adsorption properties and mechanism of Cu(II) on virgin and aged microplastics in the aquatic environment.

Microplastics (MPs) migrate by adsorbing heavy metals in aquatic environments and act as their carriers. However, the aging mechanisms of MPs in the environment and the interactions between MPs and heavy metals in aquatic environments require further study. In this study, two kinds of materials, polyamide (PA) and polylactic acid (PLA) were used as target MPs, and the effects of UV irradiation on the physical and chemical properties of the MPs and the adsorption behavior of Cu(II) were investigated. The results showed that after UV irradiation, pits, folds and pores appeared on the surface of aged MPs, the specific surface area (SSA) increased, the content of oxygen-containing functional groups increased, and the crystallinity decreased. These changes enhanced the adsorption capacity of aged MPs for Cu(II) pollutants. The adsorption behavior of the PA and PLA MPs for Cu(II) conformed to the pseudo-second-order model and Langmuir isotherm model, indicating that the monolayer chemical adsorption was dominant. The maximum amounts of aged PA and PLA reached 1.415 and 1.398 mg/g, respectively, which were 1.59 and 1.76 times of virgin MPs, respectively. The effects of pH and salinity on the adsorption of Cu(II) by the MPs were significant. Moreover, factors such as pH, salinity and dosage had significant effects on the adsorption of Cu(II) by MPs. Oxidative complexation between the oxygen-containing groups of the MPs and Cu(II) is an important adsorption mechanism. These findings reveal that the UV irradiation aging of MPs can enhance the adsorption of Cu(II) and increase their role as pollutant carriers, which is crucial for assessing the ecological risk of MPs and heavy metals coexisting in aquatic environments.

The Unseen Threat of the Synergistic Effects of Microplastics and Heavy Metals in Aquatic Environments: A Critical Review

Abstract Purpose of Review The synergistic effects of microplastics (MPs) and heavy metals are becoming major threats to aquatic life and human well-being. Therefore, understanding synergistic interactions between MPs and heavy metals is crucial to comprehend their environmental impacts. Recent Findings The mechanisms such as electrostatic attraction, surface interactions, ion exchange, hydrogen bonding, hydrophobic forces, and π–π interactions behind the synergistic effects of MPs and heavy metals were critically reviewed and justified. In addition, the roles of surface chemistry in these interactions were also emphasized. Finally, efficient remediation techniques aligning with a circular economy-based initiative to promote sustainable solutions were recommended to mitigate plastic-heavy metal pollution to achieve a cleaner environment. Summary This review examines the combined impact of MPs and heavy metals in aquatic ecosystems, detailing their mechanistic interactions, and consequences with proposed sustainable solutions. Additionally, this review highlights the MP-heavy metal contamination risks and emphasizes the need for further research to safeguard aquatic life and human health.

Toxic effect of chromium on nonspecific immune, bioaccumulation, and tissue structure of Urechis unicinctus.

The contamination of toxic heavy metals in aquatic environments has garnered significant global attention due to its detrimental effects on marine organisms and human health. Hexavalent chromium is a typical environmental and occupational heavy metal pollutant, identified as carcinogenic heavy metal. This study aimed to assess the impact of different Cr (VI) concentrations (0.05-2.5 mg/L) on Urechis unicinctus (U. unicinctus) by investigating bioaccumulation, antioxidant defense system, expression of resistance-related genes, and histological issues. A clear concentration-effect relationship was observed in the bioaccumulation of Cr (VI) in muscle tissues of U. unicinctus. Moreover, exposure to Cr (VI) can alter the activities of lysozyme (LSZ), catalase (CAT), and superoxide dismutase (SOD) to enhance cellular defense mechanisms in U. unicinctus. Likewise, maintained the normal protein structure and functional stability by regulating protein folding. The heat shock cognitive protein (HSC70) gene showed an upward and then downward trend after Cr (VI) exposure. At 12 h, the HSC70 gene expression reached the maximum values of 4.75 and 4.61-fold in the 0.1 and 1.5 mg/L groups, respectively. The organism produced a large number of free radicals, and elevated level of metallothionein (MT) was used to scavenge free radicals and alleviate oxidative stress. Additionally, histopathological examination revealed disorganization in the midgut, atrophic changes in intestinal connective tissue, uneven distribution in respiratory tissues, and irregular shape with a significant reduction in epithelial cells within the gastric cavity. These findings can serve as a valuable reference for elucidating the toxicity mechanisms of heavy metals towards marine benthic organisms and enhancing water environment monitoring strategies.

Heavy Metals Pollution and Other Physicochemical Parameters in the Crude Oil-Impacted Santa Barbara River and Environs, Bayelsa State, Nigeria

Higher levels of heavy metals in aquatic environments are most likely influenced by crude oil spills which may induce significant risk of heavy metal toxicity in aquatic species and humans. This research evaluated the levels of heavy metals and other physicochemical parameters in the crude oil-impacted Santa-Barbara River and environs of Bayelsa State, Nigeria. Heavy metals and other physicochemical parameters were examined using standard methods. Heavy metal pollution status was then deduced with standard pollution indicators. The water and fish samples collected from crude oil-impacted Santa Barbara River were heavily and moderately contaminated with iron, respectively (Igeo index = 4.29 and 2.87 for water and fish, respectively) and highly polluted with examined heavy metals (PLI = 4.29 and 1.13 for water and fish, respectively). The water samples from hand-dug wells were moderately contaminated with iron (Igeo index = 2.87) with overall low pollution by heavy metals (PLI = 0.46), while fish sold in neighboring communities was moderately contaminated with iron (Igeo index = 2.98) with overall moderate pollution by heavy metals (PLI = 0.86). However, potential ecological risks mediated by examining heavy metals in all water and fish samples were generally low (RI &lt; 40). The total dissolved solids, biochemical oxygen demand, nitrate and phosphate concentrations in all water samples were within permissible limits of WHO and FEPA. The ecological risks associated with water and fish from all sampling locations were deduced as low, mainly because iron was the most abundant heavy metal contaminant with no significant toxic response.

Co-adsorption of tetracycline and copper by the thiourea-modified porous sodium alginate microspheres

The gradual increase of antibiotics and heavy metals in aquatic environments poses a serious threat to human health and ecosystems, and finding effective methods for simultaneous removal of antibiotics and heavy metals has attracted increasing concern. In this study, a novel porous structure of thiourea-modified sodium alginate microspheres (UA-Ca) was synthesized by modification with thiourea, epichlorohydrin, and calcium chloride, and was applied for the simultaneous removal of tetracycline (TC) and Cu(II) from water. The results indicated that the UA-Ca material with 1:2 mass ratio of thiourea and sodium alginate showed the highest removal of TC and Cu(II) under the reaction condition of pH= 7. The removal process of both TC and Cu(II) follows the pseudo-second-order adsorption model and Langmuir isotherm model. UA-Ca had a high adsorption capacity toward TC and Cu(II) with the maximum value of 1.099 mmol/g and 2.793 mmol/g based on the Langmuir model at 298 K, respectively. Thermodynamical parameters revealed that TC and Cu(II) adsorption is spontaneous with endothermic nature. Competing ionic cations (Ca2+、Mg2+、NH4+) and organics (sulfamethoxazole, hygromycin) had a certain inhibitory effect on the removal of TC and Cu(II) by UA-Ca, whereas the anionic ions (CO32-、PO43-、SO42-) all had little effect on its removal. Fourier transform infrared spectra and X-ray photoelectron spectroscopy analyses showed that the removal of TC and Cu(II) by UA-Ca was mainly due to electrostatic adsorption and surface complexation. This work provides a promising UA-Ca material for the effective removal of TC and Cu(II) in contaminated water.

Recent Advances in the Application of Bionanosensors for the Analysis of Heavy Metals in Aquatic Environments.

Heavy-metal ions (HMIs) as a pollutant, if not properly processed, used, and disposed of, will not only have an influence on the ecological environment but also pose significant health hazards to humans, making them a primary factor that endangers human health and harms the environment. Heavy metals come from a variety of sources, the most common of which are agriculture, industry, and sewerage. As a result, there is an urgent demand for portable, low-cost, and effective analytical tools. Bionanosensors have been rapidly developed in recent years due to their advantages of speed, mobility, and high sensitivity. To accomplish effective HMI pollution control, it is important not only to precisely pinpoint the source and content of pollution but also to perform real-time and speedy in situ detection of its composition. This study summarizes heavy-metal-ion (HMI) sensing research advances over the last five years (2019-2023), describing and analyzing major examples of electrochemical and optical bionanosensors for Hg2+, Cu2+, Pb2+, Cd2+, Cr6+, and Zn2+.

Effects of copper and cadmium on stream leaf decomposition: evidence from a microcosm study.

We seek to understand how copper and cadmium act on leaf litter decomposition by their effects on microbial conditioning and litter fragmentation by invertebrates. In this study, we evaluated, in an integrated manner, different biological elements responsible for functioning of streams. Thus, we performed a microcosm assay with different concentrations for the two metals and their combination, evaluating their effects on fungi sporulation rate, consumption rate by shredders, and, consequently, the leaf litter decomposition rates. Sporulation rates were affected by all copper concentrations tested 10 × = 16µg L-1 and 25 × = 40µg L-1) but significantly reduced only at the highest concentration of cadmium (25 × = 22.5µg L-1). Increased copper and cadmium concentrations reduced the consumption of leaf litter by Phylloicus at 60%. The concentrations (10 × and 25 ×) of both metals resulted in a reduction in decomposition rates. When combined, copper and cadmium negatively affected microbial conditioning, consumption by shredders, and leaf litter decomposition. Increases in concentrations of copper and cadmium directly affected organic matter decomposition in aquatic environments. Thus, the presence of a high concentration of heavy metals in aquatic environments alters the functioning of ecosystems. As trace-elements occur in a combined manner in environments, our results show that the combined effects of different metals potentiate the negative effects on ecosystem processes.

Influence of extracellular polymeric substances on arsenic bioaccumulation and biotransformation in biofilms

It is well recognized that biofilms can biosorb and biotransform heavy metals in aquatic environments. However, the effects of extracellular polymeric substance (EPS) on inorganic arsenic (As) bioaccumulation and biotransformation in biofilms are still unrevealed and need to be investigated. In order to explore the above scientific issues, the As accumulation and speciation in EPS-containing or EPS-free biofilms and growth medium under As(V)/As(III) exposure conditions were measured. After the removal of EPS, the amount of As uptake (Asup) and As adsorption (Asad) in biofilms were significantly reduced, no matter whether exposed to As(V) or As(III). FTIR analysis further suggested that the interaction between these functional groups with As was limited after the removal of EPS. In the EPS-containing biofilms, the Asad was mainly As(V) with low toxicity. However, after the removal of EPS, the Asad was mainly As(III) with high fluidity, and no methylated As was found. Moreover, the removal of EPS inhibited As(III) oxidation and methylation by biofilms, resulting in the decrease of As(V) and methylated As in the growth medium. The findings of this study emphasized the essential impact of EPS on the biosorption and biotransformation of As in biofilms. This study provides a unique understanding of the role of biofilms in As biogeochemical cycle, and water quality purification function in water environments.

Investigation of dissolved organic matter's influence on the toxicity of cadmium to the cyanobacterium Microcystis aeruginosa by biochemical and molecular assays.

Rapid economic development has increased the accumulation of dissolved organic matter (DOM) and heavy metals in aquatic environments. In addition,Microcystis aeruginosa can cause the outbreak of cyanobacteria bloom and can produce microcystin, which poses a threat to human water safety. Therefore, this study analyzed the biochemical and molecular assays of DOM (0, 1, 3, 5, 8, 10 mg C L-1) extracted from four different sources on the toxicity of cadmium (Cd) to M. aeruginosa. The results showed that the addition of different concentrations of DOM from sediment, biochar, and humic acid alleviated the toxicity of Cd to M. aeruginosa. But the addition of rice hulls DOM at high concentrations (8 and 10 mg L-1) significantly reduced the normal growth and metabolic activities of M. aeruginosa. DOM from four different sources promoted the expression level of microcystin-related gene mcyA and the production of microcystin-leucine-arginine (MC-LR), and mcyA was positively correlated with MC-LR. DOM from biochar, sediment, and humic acid were able to bind Cd through complexation. The results will help to understand the toxic effects of heavy metals on toxic-producing cyanobacteria in the presence of DOM, and provide certain reference for the evaluation of water environmental health.

Development of cellulose/hydroxyapatite/TiO2 scaffolds for efficient removal of lead (II) ions pollution: Characterization, kinetic analysis, and artificial neural network modeling

The utilization of nano-biodegradable composites for removing pollutants and heavy metals in aquatic environments has been widespread. This study focuses on synthesizing cellulose/hydroxyapatite nanocomposites with titanium dioxide (TiO2) via the freeze-drying method for the adsorption of lead ions in aquatic environments. The physical and chemical properties of the nanocomposites, including structure, morphology, and mechanical properties, were analyzed through FTIR, XRD, SEM, and EDS. In addition, parameters affecting the adsorption capacity, such as time, temperature, pH, and initial concentration, were determined. The nanocomposite exhibited a maximum adsorption capacity of 1012 mg⸱g−1, and the second-order kinetic model was found to govern the adsorption process. Additionally, an artificial neural network (ANN) was created using weight percentages (wt%) of nanoparticles included in the scaffold to predict the mechanical behavior, porosity, and desorption of the scaffolds at various weight percentages of hydroxyapatite (nHAP) and TiO2. The results of the ANN indicated that the incorporation of both single and hybrid nanoparticles into the scaffolds improved their mechanical behavior and desorption, as well as increased their porosity.

Source-oriented ecological and resistome risks associated with geochemical enrichment of heavy metals in river sediments

Heavy metals (HMs) pose ecological and resistome risks to aquatic systems. To efficiently develop targeted risk mitigation strategies, apportioning HM sources and assessing their source-oriented risks are essential. Although many studies have reported risk assessment and source apportionment of HMs, yet few have explored source-specific ecological and resistome risks associated with geochemical enrichment of HMs in aquatic environments. Therefore, this study proposes an integrated technological framework to characterize source-oriented ecological and resistome risks in the sediments of a plain river in China. Several geochemical tools quantitatively showed Cd and Hg had the highest pollution levels in the environment, with 19.7 and 7.5 times higher than their background values, respectively. Positive matrix factorization (PMF) and Unmix were comparatively used to apportion sources of HMs. Essentially, the two models were complementary and identified similar sources including industrial discharges, agricultural activities, atmospheric deposition and natural background, with contributions of 32.3–37.0%, 8.0−9.0%, 12.1−15.9% and 42.8−43.0%, respectively. To analyze source-specific ecological risks, the apportionment results were integratively incorporated into a modified ecological risk index. The results showed anthropogenic sources were the most significant contributors to the ecological risks. Particularly, industrial discharges majorly contributed high- (44%) and extremely high (52%) ecological risk for Cd, while agricultural activities posed a greater percentage of considerable-(36%) and high- (46%) ecological risk for Hg. Furthermore, the high-throughput sequencing metagenomic analysis identified abundant and diverse antibiotic resistance genes (ARGs), including some carbapenem-resistance genes and emerging genes such as mcr-type in the river sediments. Network and statistical analyses displayed significant correlations between ARGs and geochemical enrichment of HMs (ρ > 0.8; P-value <0.01), indicating their important impacts on resistome risks in the environment. This study provides useful insights into risk prevention and pollution control of HMs, and the framework can be made applicable to other rivers facing environmental challenges worldwide.

Applying synchronous fluorescence spectroscopy combined with Gaussian band fitting and two-dimensional correlation to characterize interactions of copper (II) with dissolved organic matter from urban river sediments

Dissolved organic matter (DOM) and heavy metals can form strong complexes, which might determine distribution, toxicity, bioavailability, and environmental trend of heavy metals in aquatic environment. Synchronous fluorescence spectroscopy combined with Gaussian band fitting and two-dimensional correlation (2DCOS) was applied to characterize Cu2+ interactions with DOM fractions from sediments in Xihe River. DOM from four layers was mainly associated with tyrosine-like (TYLF), tryptophan-like (TRLF), microbial humic-like (MHLF), fulvic-like (FLF), and humic-like fluorescence (HLF) substances based on Gaussian band fitting. At the first layer, the f value of FLF was the highest among five components, while TRLF at the second and third layers represented the highest f values. Besides, at the fourth layer, the f value of TYLF was the highest. According to 2DCOS and moving window 2DCOS, the decreasing binding sensitivities were HLF→MHLF→TYLF→TRLF→FLF in the first layer, which almost represented high efficiencies at 40 μM Cu2+. The binding order was MHLF→HLF→FLF→TRLF→TYLF in the second layer, where TYLF and TRLF shared the identical efficiencies at 120 μM Cu2+. For the third layer, the varying order was TYLF→FLF→TRLF→MHLF→HLF, whose high efficiencies occurred at 10 μM Cu2+. In the fourth layer, the order was TYLF→FLF→MHLF→TRLF→HLF, whose efficiencies almost covered whole titrate concentrations. At a given layer, structural equation model showed Cu2+ concentration negatively affected the fluorescence intensity of DOM components except FLF at the substrate layer. This study might provide an effective method to illustrate the interaction mechanism of the heavy metals and DOM fractions.

Pollution status and risk assessment of heavy metals in the sediment of a historically contaminated lake treated by oxidation pond in China.

Sediment plays animportant role in controlling biogeochemical cycling of heavy metals in aquatic environment. The Ya-Er Lake is a typical lake which was historically contaminated by heavy metals in Hubei province, China. After industries surrounding the Ya-Er Lake being shut down, oxidation pond treatment and dredging program were conducted for pollution management since 1970s. To date, the Ya-Er Lake has been used for aquaculture for several decades. However, the status of heavy metal levels and ecological risks in this lake remains unclear. Herein, concentrations, chemical fractions, and risk assessment of heavy metals were investigated in the Ya-Er Lake sediment. Results showed that concentrations of heavy metals in the Ya-Er Lake sediment were higher than other reported lake systems, suggesting that heavy metal pollution in the Ya-Er Lake is still serious. Relatively higher proportions of carbonates bound form of Cd and Ni indicated high-risk potential of these two heavy metals, and Cd and Ni should be listed as the primary heavy metal pollutants in the Ya-Er Lake according to the results of potential ecological risk index (PERI) and sediment quality guidelines (SQGs). The risk assessment code (RAC) analysis showed that Ni and Cd poses higher bioavailability and mitigation potential, and may affect the Ya-Er Lake ecosystem and downstream aquatic environment. These findings reflected that oxidation pond treatment and dredging sediment to near place are not effective to control heavy metal pollution, and a long-term ecological risk is still posed to surrounding aquatic environment. Our study provides scientific basis on pollution control and management in aquatic system contaminated by heavy metals.