Copper Contamination Research Articles

Clogging modulates the copper effects on microbial communities of streambed sediments

The hyporheic zone, i.e. the water-saturated sediment beneath and alongside the riverbed, is exposed to multiple stressors. Agricultural-watershed rivers are frequently exposed to two concomitant stressors: clogging and copper contamination. However, one stressor exposure can increase sensitivity to a second stressor. The aim of this study was to experimentally test the cumulative effects of these two stressors on copper distribution and structural and functional microbial communities responses in the hyporheic zone. A slow filtration column experiment was conducted to compare the effects of 3 treatments of increasing complexity: 'Reference', 'Copper-contaminated' (dissolved copper added at 191 µg L-1), and 'Clogging+Copper' (dissolved copper + addition of 2 cm of fine sediment). Microbial community structure and activities were studied at 4 column sediment depths. The results showed that clogging did not modify the distribution of copper, which remained fixed in the first few centimetres. In the first few centimetres, clogging had a stimulating effect on microbial activities whereas copper had limited effects mainly on leucine aminopeptidase activity and microbial community tolerance to copper. The subsurface zone thus hosts significant different microbial communities from the communities in the deeper zones that were protected from surface stressors. This experiment confirms the valuable filtering role played by the hyporheic zone and shows that microbial responses are strongly correlated to microhabitat-scale physicochemical conditions in sediment.

Investigation of Cu Adsorption and Migration with Spectral Induced Polarization in Activated Carbon.

In this paper, the adsorption process of copper ions on activated carbon (AC) was simulated in a column test. It was deduced that it is consistent with the pseudo-second-order model. Cation exchange was observed to be the major mechanism of Cu-AC interactions through scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) measurements. Adsorption isotherms were fitted well using the Freundlich model. Adsorption thermodynamics at 298, 308, 318 K demonstrated that the adsorption process is spontaneous and endothermic. Spectral induced polarization (SIP) technique was used to monitor the adsorption process, and the double Cole-Cole model was used to analyze the SIP results. The normalized chargeability was proportional to the adsorbed copper content. Two measured relaxation times from the SIP testing were converted into the average pore sizes of 2, 0.8, 0.6, 100-110, 80-90, and 53-60 µm by the Schwartz equation, which are consistent with the measured pore sizes from both mercury intrusion porosimetry and scanning electron microscopy (SEM). The reduction in the pore sizes by SIP during the flow-through tests suggested that the adsorbed Cu2+ gradually migrated into small pores as with continued permeation of the influent. These results showcased the feasibility of using SIP technique in engineering practice involving the monitoring of copper contamination in land near a mine waste dump or in adjacent permeable reactive barriers.

Gene Regulation and Global DNA Methylation Changes in White Spruce (Picea glauca) in Response to Copper Contaminations

Gene Regulation and Global DNA Methylation Changes in White Spruce (Picea glauca) in Response to Copper Contaminations

Assessment of Wafer‐Level Transfer Techniques of Graphene with Respect to Semiconductor Industry Requirements

AbstractGraphene is a promising candidate for future electronic applications. Manufacturing graphene‐based electronic devices typically requires graphene transfer from its growth substrate to another desired substrate. This key step for device integration must be applicable at the wafer level and meet the stringent requirements of semiconductor fabrication lines. In this work, wet and semidry transfer (i.e. wafer bonding) are evaluated regarding wafer scalability, handling, potential for automation, yield, contamination, and electrical performance. A wafer scale tool is developed to transfer graphene from 150 mm copper foils to 200 mm silicon wafers without adhesive intermediate polymers. The transferred graphene coverage ranges from 97.9 % to 99.2 % for wet transfer and from 17.2 % to 90.8 % for semidry transfer, with average copper contaminations of 4.7 × 1013 (wet) and 8.2 × 1012 atoms/cm2 (semidry). The corresponding electrical sheet resistance extracted from terahertz time‐domain spectroscopy varied from 450 to 550 Ω sq−1 for wet transfer and from 1000 to 1650 Ω sq−1 for semidry transfer. Although the wet transfer is superior in terms of yield, carbon contamination level, and electrical quality, wafer bonding yields lower copper contamination levels and provides scalability due to existing industrial tools and processes. Our conclusions can be generalized to all 2D materials.

Study on the Interaction between the Reduction and Remediation of Dredged Sediments from Tai Lake Based on Vacuum Electro-Osmosis

The treatment of metal-contaminated sediment generated in environmental dredging projects often requires both reduction and remediation, and the electric field has good application prospects in the integration of reduction and remediation. In this study, based on the electro-osmosis, vacuum, and vacuum electro-osmosis methods, a detachable test system was made. Experiments of the three methods were carried out independently on the reduction and remediation of dredged sediment from Tai Lake under pollution-free and Cu-contaminated conditions. The results show that copper contamination weakens the effect of reduction, and the production of copper precipitates makes the soil more prone to cracking and blocking drainage channels, which has the greatest impact on the electro-osmosis method. In terms of copper concentration, vacuum electro-osmosis achieves the transport and discharge of contaminants, and has the best remediation effect. The removal rates at the anode and cathode are 45.1% and 50.0%, respectively. A correlation model based on electrical conductivity, moisture content, and contaminant concentration was established to facilitate the determination of contaminant concentrations in actual projects. Electro-migration plays a dominant role in the remediation process, and the reduction affects the electric field distribution and, thus, the migration efficiency.

Environmental risk assessment of the contamination of river water and sediments from the Bor mining area, East Serbia―Secondary Cu enrichment at the reservoir site

AbstractThe study area is within the Bor copper mining region, Eastern Serbia, where wastewaters from the Bor metallurgical/smelting facilities have caused serious copper (Cu) and arsenic (As) contamination to the Timok river system. The operating conditions at smelting facilities control the pH of the river waters, resulting in highly acidic waters in 2019 than 2015. This study compares the mobility of Cu and As and risk assessment of river water contamination during both years as well as assessing the risks of riverbed sediments contamination and investigating the origins of Cu and As pollution. In the river system, As generally existed as a particulate species in the entire study area during both years and was widely removed from river waters by sorption onto the hydrous ferric oxides (HFO), whereas dissolved Cu was removed from river waters only at neutral pH conditions with hydrous aluminum oxides (HAO) and HFO at the downstream reservoir site of Timok River. Despite the similarity in Cu mobility during both years, the lower pH of river waters in 2019 than 2015 enabled dissolved Cu species to be transported farther downstream, resulting in a higher level of river water pollution. The contamination factor (CF), used to estimate levels of sediment pollution, had higher values for Cu and As compared to Zn, Pb, Co, and Ni. The CF values of Cu were the highest in sediments near the Bor metallurgical/smelting facilities and at downstream reservoir site, whereas the CF values of As were generally high in the entire research field. Additionally, the ecological risk potential (Er) values of Cu were the highest in sediments of the Bor River and Timok River, reflecting an enrichment of Cu at these sites. Finally, a clarification on the origin of Cu pollution and risks of mobilization was inferred from the sequential extraction test. The predominant Cu species in sediments of the upstream region were oxidizable and residual, hosted by copper sulfides originating from the flotation tailings, suggesting a relatively low risk of Cu release from these sediments. However, at the downstream site (especially reservoir sediments), the contribution of acid‐soluble Cu was 34.8%, suggesting a higher risk of Cu release. The highest contributions of acid‐soluble and reducible Cu (18%) at the reservoir site were promoted by the effective settlement of Cu‐sorbing HAO and HFO. The Cu contents of these two fractions were 0.86 wt%, almost three times higher than that of Cu ore in Veliki Krivelj open pit mine.

Arsenic and Copper Contaminant Transport Modelling In Xaysomboun Province, LAO PDR

Arsenic and Copper Contaminant Transport Modelling In Xaysomboun Province, LAO PDR

Environmental Health Risk Analysis of Copper Exposure to Catfish Commonly Consumed By People in Ulak Jermun Village, Ogan Komering Ilir

Catfish cultivated in rivers can be contaminated by heavy metals such as copper (Cu) which come from activities around the river. Copper exposure through the consumption of catfish will be harmful to health. This research aim to analyze the public health risks due to catfish consumption in Ulak Jermun Village, Ogan Komering Ilir. The design of study was cross sectional using the Environmental Health Risk Analysis method. The research respondents were 113 people with 5 samples of catfish taken from the river where the fish were cultivated. The analysis of heavy metal copper using the Atomic Absorption Spectrophotometer (AAS) method. The results showed copper contamination in catfish with an average concentration of 1.67 mg/kg. There were no respondents with RQ value > 1 for realtime non-carcinogenic health risks, but 11 people (9.7%) of respondents with RQ value > 1 for non-carcinogenic health risks in a lifetime. Meanwhile, for realtime carcinogenic exposure 34.5% had ECR values > 10-4 and 100% of respondents had ECR values > 10-4 for carcinogenic effects in lifetime. The conclusion was the people of Ulak Jermun are at risk of experiencing carcinogenic diseases due to copper exposure with the largest percentage of people aged> 32 years, female, and weighing ≤ 57 kg.

Copper in compensated p- and n-type Czochralski silicon: Diffusivity, influence on the majority charge carrier density and mobility

Copper contamination risks are present throughout the whole crystalline silicon solar cell process flow, namely during ingot growth processes using recycled feedstock, wafer sawing and metallisation. Copper is a fast-diffusing impurity which can modify the carrier transport and recombination properties. The aim of this study is to present new insights into the properties of copper-contaminated highly doped and compensated silicon, with a focus on the copper diffusivity and the influence of this impurity on the majority carrier mobility and density. For this, compensated Czochralski silicon ingots were grown from electronic grade feedstock doped with boron and phosphorus, and the wafers intentionally contaminated with copper. Its concentrations were measured by Glow Discharge Mass Spectrometry, while the electrical properties were extracted from Hall Effect measurements. The dopant concentrations were used to compute the effective diffusivity of interstitial copper and important changes in the copper diffusivity are expected in the vicinity of the p-type/n-type transition. For the n-type compensated wafers, a strong migration of copper atoms towards the surface and a reduced copper bulk content were highlighted. Furthermore, the presence of precipitates was experimentally revealed. Both the equilibrium electron density and electron mobility were not influenced by the contamination. In p-type compensated material, copper atoms did not accumulate at the surface, probably due to both the limited copper precipitation in p-type silicon and the lower copper diffusivity. In addition, the equilibrium hole density was not influenced. However, the hole carrier mobility was affected, likely associated to the higher bulk copper content. • Highly doped compensated silicon was intentionally contaminated with copper. • Electrical properties were obtained from Hall Effect measurements. • Large differences in copper diffusivity close to the p-to n-type transition. • Strong migration of copper towards the surface in n-type compensated wafers. • Equilibrium electron density and mobility are not influenced by the contamination.

Screening of zinc, copper and iron in lettuce and Chinese cabbage cultivated in Durban, South Africa, towards human health risk assessment

Human well-being and ecological reliability continue to face a major threat resulting from heavy metal pollution to soils caused by untreated discharge from metropolitan and industrial wastewater. The potential human health risks of zinc (Zn), copper (Cu) and iron (Fe) contamination to native inhabitants through the food chain were assessed in Pinetown, Durban, where their irrigation processes are from the Umgeni River passing through the highly industrialised Pinetown area. River water, vegetables (cabbage and lettuce) and soil were analysed for Zn, Cu and Fe; transfer factor, health risk index and the daily intake of metals were also calculated. The concentrations of heavy metals indicated the pattern trend as Fe>Zn>Cu for both cabbage and lettuce. The levels of transfer factors for heavy metals ranged from 0.02 mg/kg to 1.89 mg/kg. The health risk index (0.0002–01430) was found to be within the recommended range (<1), which poses no human health risk with respect to all heavy metals tested. Significance: The present study has generated data on heavy metal pollution in and around the area and associated risk assessment for consumers’ exposure to the heavy metals. These data can assist decision-makers in understanding the suitability status of vegetable consumption and irrigation by providing an understanding of the human health risk of the studied area. This database can be used as a tool to pinpoint the mechanisms and processes influencing public health implications of heavy metals in foods, soils and water.

Recycling‐Induced Copper Contamination of a 42CrMo4 Quench and Tempering Steel: Alterations in Transformation Behavior and Mechanical Properties

The transformation behavior and the mechanical properties of three laboratory produced steels are presented. To investigate the influence of copper contamination, the reference alloy 42CrMo4 is modified and alloyed with 0.5 and 1.0 wt% copper, respectively. The transformation behavior is investigated through dilatometry that yields continuous cooling transformation diagrams, while the mechanical properties are investigated by hardness measurements as well as Charpy‐V‐notch impact and tensile tests. Accompanying microstructure investigations by means of light optical, scanning electron, and transmissions electron microscopy and thermodynamic simulations (CALPHAD) are performed. It is demonstrated that copper contamination that will be unavoidable when increasing the overall steel recycling fraction may contain the potential for increasing the hardness as well the strength of standard high strength steels, although it is considered to be very detrimental during steel production. Together with reduced environmental footprints and production costs due to the utilization of lower grade scrap with more Cu‐contamination, the development of alternative processing routes for Cu‐contamination‐tolerant high strength steels is pursued.

Molecular mechanism of Cu metal and drought stress resistance triggered by Porostereum spadiceum AGH786 in Solanum lycopersicum L.

Rapid industrialization and global warming have threatened the plants with multiple abiotic stresses, such as heavy metals and drought stress. For crop cultivation, the conventional approach of cleaning the soils by excavation is very costly and not feasible for large scale. Establishing toxin-free and drought-resistant crops is a major challenge in the environment under natural and anthropogenic pressure. In the past decades, copper contamination of agricultural land has become an emerging concern. For dry land reclamation, several new strategies, including bioremediation (phytoremediation and microbial remediation), have been used. Owing to the potential of Cu hyperaccumulators, the current project aims to enhance the drought tolerance and the phytoremediation potential of Solanum lycopersicum L. with the inoculation of copper and 12% polyethylene glycol (PEG)-induced drought stress-tolerant endophytic fungus Porostereum spadiceum AGH786 under the combined stress of copper heavy metal and PEG-induced drought stress. When S. lycopersicum L. was watered with individual stress of copper (Cu) concentration (400 ppm) in the form of copper sulfate (CuSO4.5H2O), 12% PEG-induced drought stress and the combined stress of both negatively affected the growth attributes, hormonal, metabolic, and antioxidant potential, compared with control. However, the multistress-resistant AGH786 endophytic fungus ameliorated the multistress tolerance response in S. lycopersicum L. by positively affecting the growth attributes, hormonal, metabolic, and antioxidant potential, and by restricting the root-to-shoot translocation of Cu and inducing its sequestration in the root tissues of affected plants. AGH786-associated plants exhibited a reduction in the severity of copper (Cu) and drought stress, with higher levels of SlCOPT (Cu transporters) and SlMT (metallothionine) gene expressions in root and shoot tissues, indicating that AGH786 contributed to resistance to copper metal toxicity and drought stress in the host S. lycopersicum L.

Copper induces a downregulation of the Multidrug resistance protein 4 (MRP4) and Copper-transporting ATPase-RAN1 (RAN1) genes in red pine (Pinus resinosa) at low concentrations

ABSTRACT Copper is required in plant tissues at small concentrations for several physiological processes; however, excess metal can cause toxicity. The main objectives of this study were to (1) evaluate Pinus resinosa resistance to different concentrations of copper, and (2) assess changes induced by copper ions on gene expression. The targeted genes include the Multidrug resistance protein 4 (MRP4) and Copper-transporting ATPase-RAN1 (RAN1). P. resinosa seedlings were treated with different concentrations of copper sulphate and corresponding salt controls in growth chamber screening tests. These concentrations include 13, 130 mg and 1300 mg of copper per 1 kg of dry soil. Potassium sulfate and water were used as controls. The expression of MRP4 and RANI genes was assessed using RT-qPCR. All the genotypes tested were resistant to copper. There was a significant suppression of the MRP4 and RANI genes at the lowest concentration of copper (13 mg/kg) in comparison to the water control. Further increases in the copper concentrations (130 mg /kg and 1300 mg/kg) did not induce any significant change in gene expression. Overall, this study showed that P. resinosa is in general resistant to copper contaminants. However, copper ions affect gene expression, even at low concentrations.

Copper Adsorption Potentiality of Bacillus stercoris GKSM6 and Pseudomonas alcaliphila GKSM11 Isolated from Singhbhum Copper Mines

Increasing industrial activities, mining deposits, excessive use of hazardous chemicals, and waste discharges are the driving forces for emerging copper (Cu) contamination. In the present study, two highly Cu-tolerant bacterial isolates, Bacillus stercoris GKSM6 and Pseudomonas alcaliphila GKSM11, were isolated, characterized, and investigated for their copper sorption potential. The Cu2+ tolerable concentrations were found to be 350 mg/L for strain GKSM6 and 400 mg/L for strain GKSM11. The maximum copper uptake capacity of GKSM6 was found to be 35.05 mg/g, whereas it was 31.15 mg/g in case of GKSM11 at optimum conditions of pH 7.0, temperature 35 °C for 24 h. The equilibrium data was well fitted with the Langmuir isotherm model (R 2 = 0.9851 for B. stercoris and R 2 = 0.9954 for P. alcaliphila), indicating a homogenous monolayer adsorption pattern. Electron microscopic analysis confirmed the immobilization of copper ions on the bacterial cell surface. The EDS peak also showed the surface sorption of copper ions, which was confirmed by the presence of various functional groups like carboxyl, hydroxyl, amine, and phosphate. In this prospect, the novelty of this study relies on the biosorption of Cu2+ using Singhbhum copper mines inhabiting bacterial isolates pay as a possible option for the amelioration of copper-contaminated sites.

Mapping risks associated with soil copper contamination using availability and bio-availability proxies at the European scale

Soil contamination by trace elements like copper (Cu) can affect soil functioning. Environmental policies with guidelines and soil survey measurements still refer to the total content of Cu in soils. However, Cu content in soil solution or free Cu content have been shown to be better proxies of risks of Cu mobility or (bio-)availability for soil organisms. Several empirical equations have been defined at the local scale to predict the amount of Cu in soil solution based on both total soil Cu content and main soil parameters involved in the soil/solution partitioning. Nevertheless, despite the relevance for risk assessment, these equations are not applied at a large spatial scale due to difficulties to perform changes from local to regional. To progress in this challenge, we collected several empirical equations from literature and selected those allowing estimation of the amount of Cu in solution, used as a proxy of available Cu, from the knowledge of both total soil Cu content and soil parameters. We did the same for the estimation of free Cu in solution, used as a proxy of bio-available Cu. These equations were used to provide European maps of (bio-)available Cu based on the one of total soil Cu over Europe. Results allowed comparing the maps of available and bio-available Cu at the European scale. This was done with respective median values of each form of Cu to identify specific areas of risks linked to these two proxies. Higher discrepancies were highlighted between the map of bio-available Cu and the map of soil total Cu compared to the Cu available map. Such results can be used to assess environmental-related issues for land use planning.

Molecular markers of cytotoxicity induced with copper-contained pesticides

The applying copper sulphate is a cheap, however it leads to global the environment contamination. Especially, the contamination of the water sources is crucial for fish harvesting and farming. The copper contamination in some areas are caused by decades. The impact of copper ions is dependent on the inhibition of invasive aquatic plants, many microorganisms and protozoa. The family of copper-contained chemicals is frequently used as algaecides in swimming pools. Despite the copper ions are well known as a high toxic for fish in freshwater ponds, the copper sulphate remains one of the prevalent pesticides in fish farming everywhere. High cytotoxicity and accumulation of the copper ions in the sediments require studying and calculation of the optimal dosage to use it as an antiseptic agent that should prevent the detrimental effect in various tissue types of aquatic organisms. The main depicted mechanism, which is associated with cytotoxicity is the generation of oxidative stress.
 Neural tissue cells are extremely susceptible to oxidative damages. Neural damaging is important cause of the CNS disfunction as well as is the critic to the organism vitality. Glial cells maintain the structure and many vital functions of neuronal cells. Glial fibrillary acidic protein (GFAP), transcriptional nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) and poly(ADP-ribose) polymerase (PARP) are critic regulators in a cell response to the environment toxicity. Based on this fact, it could be applied as the boimarkers of heavy metal toxicity. In presented study, we investigated the effects of copper ions on PARP, NF-kB, and GFAP expression in the rainbow trout (Oncorhynchus mykiss) brain tissue. For 96 hours the fishes were exposed to the copper sulphate sublethal concentrations 380 µg/L, estimated as 1/4 of the LC50 value. Western blot analysis of GFAP, NF-kB and PARP was used to assess further effects in the brain tissue.
 The modulatory effect of copper ions on the expression of GFAP was detected in fish brain. Reciprocal changes were observed in respect with 24 hours exposure in compare to both 48 hours and 96 hours treatment. Obtained results demonstrated meaningful disturbance in the expression of transcriptional factor NF-kB in the brain of fish group exposed to copper in compare to control group. Furthermore, the time-depended effect in a range 24 – 96 hours was detected. However, the short time exposure to copper ions initiated no effect in fish group treated 24 hours while in compare to both 48 hours and 96 hours treatment. The similar changes of PARP content in the brain of fish were determined as well. It deserves to be mentioned that all of aforementioned changes of GFAP, NF-kB and PARP expression were accompanied by increasing in reactive oxygen species content. Thus, copper ions cytotoxic effect could be initiated with oxidative injury in a brain tissue.
 On the other hand, the observed effect of copper in the fish brain evidences the unspecific toxicity of this ion in brain tissue cells.
 The results showed that copper ions could induce astroglial response accompanied by modulations of NF-kB and PARP-1 expression. Obtained in presented study data suggest that copper sulphate has significant effect on astrogliosis and DNA damage in the fish brain.

Nitrogen to phosphorus ratio shapes the bacterial communities involved in cellulose decomposition and copper contamination alters their stoichiometric demands.

All living organisms theoretically have an optimal stoichiometric nitrogen: phosphorus (N: P) ratio, below and beyond which their growth is affected, but data remain scarce for microbial decomposers. Here, we evaluated optimal N: P ratios of microbial communities involved in cellulose decomposition and assessed their stability when exposed to copper Cu(II). We hypothesized that (1) cellulose decomposition is maximized for an optimal N: P ratio; (2) copper exposure reduces cellulose decomposition and (3) increases microbial optimal N: P ratio; and (4) N: P ratio and copper modify the structure of microbial decomposer communities. We measured cellulose disc decomposition by a natural inoculum in microcosms exposed to a gradient of N: P ratios at three copper concentrations (0, 1 and 15µM). Bacteria were most probably the main decomposers. Without copper, cellulose decomposition was maximized at an N: P molar ratio of 4.7. Contrary to expectations, at high copper concentration, the optimal N: P ratio (2.8) and the range of N: P ratios allowing decomposition were significantly reduced and accompanied by a reduction of bacterial diversity. Copper contamination led to the development of tolerant taxa probably less efficient in decomposing cellulose. Our results shed new light on the understanding of multiple stressor effects on microbial decomposition in an increasingly stoichiometrically imbalanced world.

A hybrid biocomposite of Thamnidium elegans/olive pomace/chitosan for efficient bioremoval of toxic copper

Immobilized biomaterials have recently attracted researchers' attention in the field of environmental biotechnology due to their effective biosorption performances. In this respect, a novel hybrid biocomposite based on Thamnidium elegans cells, olive pomace, and chitosan (TE-OP@C) was produced and tested for the first time to remove a target pollutant. It was successfully employed to eliminate toxic Cu(II) ions. Uptake efficiency of the biocomposite was significantly greater than that of T. elegans and T. elegans-olive pomace, despite the much lesser amount of biocomposite used. Freundlich model best fitted the equilibrium data, and the pseudo-second-order kinetic model followed Cu(II) uptake. The maximum removal efficiencies in batch and continuous systems were determined to be 96 % and 98 %, respectively. After eight cycles, the biosorption and recovery efficiencies of TE-OP@C were higher than 90 %. Biocomposite was able to remove approximately 90 % and 88 % of Cu(II) from real wastewater in batch and continuous systems, respectively. FTIR analysis, zeta potential measurements, EDX, and SEM findings confirmed the Cu(II) uptake. XRD and BET analysis were also performed for biocomposite characterization. Breakthrough and exhausted points were determined as 80 and 150 min, respectively. The findings potentially lead to a new perspective on the treatment of copper contamination.

The effect of a dam on the copper accumulation in estuarine sediment and associated nematodes in a Mekong estuary

Dam construction across the main flow of an estuary can greatly contribute to a high accumulation of inorganic contaminants. However, it remains unknown to what extend externally available heavy metals are incorporated into biota living in those contaminated environments. In this study, the heavy metal copper was investigated both in the sediment and in the tissues of nematodes taken from the subtidal zone in the Ba Lai estuary where a dam is present, and compared with samples from the dam-free Ham Luong estuary, both part of the Mekong Delta. Samples were taken in the dry season of 2017 in four stations in the Ba Lai estuary with two stations in the downstream part from the dam and two upstream. Similar locations with respect to the distance were sampled in the dam-free estuary. The internal copper concentration in nematodes was measured by applying micro X-ray fluorescence. The results showed that both internal and sediment copper concentrations were different between the two estuaries and among estuarine sections. The highest copper concentration in nematodes was found in the upstream section of Ba Lai estuary where the greatest accumulation of sedimentary copper was observed, while the dammed downstream part was lowest in internal copper accumulation. Moreover, there was more variation in the copper levels between the two sections within the dammed estuary compared to those in Ham Luong. These observations might point to the contribution of the Ba Lai dam to the increase of copper contaminants in the benthic environment leading to accumulation in nematodes.

Mineral Neutralizers as a Tool for Improving the Properties of Soil Contaminated with Copper

In phytoremediation processes implemented in highly contaminated areas, there is a high risk of contaminant toxicity during the germination of freshly sown plants. In such conditions, it is recommended to support phytoremediation by using neutralizing additives. The present study aimed at assessing the effect of the addition of mineral neutralizers (MNs), i.e., limestone, clay, and zeolite, to soil contaminated with copper (0, 200, 400, 600 mg kg−1). Basic soil indicators were analyzed, such as pH, hydrolytic acidity (HAC), total exchangeable bases (TEB), cation exchange capacity (CEC), base saturation (BS), electrolytical conductivity (EC), total organic carbon (TOC), total nitrogen (Ntot), carbon to nitrogen ratio (C:N),, and interactions of soil micronutrients, such as Cu, Zn, Cd, Cr, Ni, Pb, Mn, and Fe with MNs. Copper contamination significantly decreased the soil pH and increased its HAC. A decrease in the share of TEB was found, which resulted in a decrease in the CEC and in BS of the soil. Among the additives, limestone had the most beneficial effect on reducing soil acidity, contributing to a significant increase in TEB, CEC, and BS. The least favorable effect was shown for clay, which generally caused the deterioration of soil properties. The MNs significantly increased the content of Zn, Cr, and Fe and lowered the content of Ni in the soil compared to the control. The demonstrated interactions indicate the diversified activity of MNs at different levels of soil contamination with copper.