Heavy metal biomagnification and genotoxic damage in two trophic levels exposed to mine tailings: a network theory approach

Trophic transfer of heavy metals across a food chain in a wastewater-irrigated agroecosystem

Wastewater irrigation is often practiced in arid regions, which can increase the chance of heavy metals contaminating the agricultural system. This contamination poses risks to both the environment and human health. This research looked into how cadmium (Cd), lead (Pb), copper (Cu), and zinc (Zn) move through a food chain involving soil, plants, and arthropods. The study was conducted in El-Gabal El-Asfar, Egypt, comparing treated and untreated wastewater irrigation areas. Six soil-irrigated sites and one reference site were sampled for soil, alfalfa (Medicago sativa), two grasshopper species (Aiolopus thalassinus and Calephorus compressicornis), and a wolf spider (Hogna ferox). The samples were analyzed for their heavy metal content. Metal concentrations in all components of the wastewater irrigated system were significantly higher compared to the reference site. The wolf spider and the soil contained the highest levels of Cd, Pb, and Cu, while the greatest concentrations of Zn were found in the spider and grasshoppers. Despite limited transfer from soil to plant, trace elements biomagnified within the terrestrial food chain, specifically from grasshoppers to wolf spiders. The correlation analysis of metal levels between soils, plants, and arthropods in the present study reflects its transfer across the trophic levels. It suggests that dietary intake is the main source of metal accumulation in arthropods. The present study, therefore, quite clearly indicated the possibility of heavy metal biomagnification in terrestrial food chains of wastewater-irrigated agroecosystems. Continuous monitoring and management of such systems are advocated to avoid environmental and public health risks.

Effects of land reclamation on soil organic carbon and its components in reclaimed coal mining subsidence areas

The accumulation of soil organic carbon (SOC) is crucial for the development and ecosystem function restoration of reclaimed mine soils (RMSs). To optimize reclamation management practices, this study aims to explore the factors and underlying mechanisms influencing the recovery of SOC and its components in RMSs from a systemic perspective using complex network theory (CNT). This study focused on coal mining subsidence areas in the eastern mining regions of China, comparing reclaimed cultivated land with surrounding non-subsided cultivated land. Soil samples were collected at depths of 0-20 cm, 20-40 cm, and 40-60 cm, and 25 soil indicators were measured. CNT was applied to explore the intricate relationships between soil indicators and to identify the key factors and underlying mechanisms influencing SOC and its components in RMSs. The results revealed that the compaction-induced soil structural damage during the reclamation process led to a chain reaction, resulting in increased soil bulk density (11.92 % to 15.03 %), finer soil particles (5.00 % to 9.88 % more clay and silt), and enhanced SOC mineralization (SOC decreased by 10.70 % to 15.62 % with a lower C/N ratio by 2.30 % to 28.55 %). Microbial activity also decreased, with a 6.25 % to 13.16 % drop in MBC and a 0.91 % to 27.68 % decrease in enzyme activity. The utilization of active SOC fractions by more adaptable bacterial communities was crucial within this chain reaction process. The intermediate role of soil structure in the RMS ecosystem, particularly in carbon cycling, becomes more prominent. RMSs exhibited heightened sensitivity to soil structure changes, with the response of microorganisms and enzymes to soil structure changes being pivotal. In the carbon cycling process of RMSs, microbial-driven enzyme activity in response to soil structure was more critical during SOC transformation, while the role of physical-chemical protection and microbial inhibition mediated by iron‑aluminum oxides became more pronounced in stabilizing SOC.

Screening of natural surface waters of the Almaty region of the Republic of Kazakhstan for toxic and mutagenic activity

Natural aquatic ecosystems are a habitat for many organisms, a source of drinking water, and a resource for human economic activity. However, natural surface waters have been subjected to intense anthropogenic pressure in recent decades. The current study was dedicated to investigating genotoxic potential in 15 rivers and 2 lakes of Almaty agglomeration (Kazakhstan) using a battery of bioassays. Non-diluted surface water samples were tested for mutagenic potential using Lux-based bacterial biosensors and a chromosome aberration test on Hordeum vulgare and Mus musculus. The studies involved lux-biosensors pRecA-lux, pColD-lux, pSoxS-lux, pKatG-lux did not find any genotoxic and oxidative effects. However, the mutagenicity of the studied water samples was detected by using plant and animal tests (Hordeum vulgare and Mus musculus). Mutagenic (increase in the frequency of chromosomal aberrations) activity of the water samples was observed. Among 17 sample collection points, surface waters of 12 were considered to possess mutagenic activity when tested on Hordeum vulgare. The results of the cytogenetic assay on mice bone marrow are alarming, as the survey proposed the strong genotoxic potential of water for mammals. Among 17 sample collection points, surface waters of 7 were considered to possess mutagenic activity when tested on Mus musculus. This comprehensive study indicates that the contamination of the surface natural waters poses a threat to river dwellers and the human population in the rivers and lakes areas.

Bioremediation of Endocrine Disrupting Chemicals- Advancements and Challenges

Endocrine Disrupting Chemicals (EDCs), major group of recalcitrant compounds, poses a serious threat to the health and future of millions of human beings, and other flora and fauna for years to come. A close analysis of various xenobiotics undermines the fact that EDC is structurally diverse chemical compounds generated as a part of anthropogenic advancements as well as part of their degradation. Regardless of such structural diversity, EDC is common in their ultimate drastic effect of impeding the proper functioning of the endocrinal system, basic physiologic systems, resulting in deregulated growth, malformations, and cancerous outcomes in animals as well as humans. The current review outlines an overview of various EDCs, their toxic effects on the ecosystem and its inhabitants. Conventional remediation methods such as physico-chemical methods and enzymatic approaches have been put into action as some form of mitigation measures. However, the last decade has seen the hunt for newer technologies and methodologies at an accelerated pace. Genetically engineered microbial degradation, gene editing strategies, metabolic and protein engineering, and in-silico predictive approaches - modern day's additions to our armamentarium in combating the EDCs are addressed. These additions have greater acceptance socially with lesser dissonance owing to reduced toxic by-products, lower health trepidations, better degradation, and ultimately the prevention of bioaccumulation. The positive impact of such new approaches on controlling the menace of EDCs has been outlaid. This review will shed light on sources of EDCs, their impact, significance, and the different remediation and bioremediation approaches, with a special emphasis on the recent trends and perspectives in using sustainable approaches for bioremediation of EDCs. Strict regulations to prevent the release of estrogenic chemicals to the ecosystem, adoption of combinatorial methods to remove EDC and prevalent use of bioremediation techniques should be followed in all future endeavors to combat EDC pollution. Moreover, the proper development, growth and functioning of future living forms relies on their non-exposure to EDCs, thus remediation of such chemicals present even in nano-concentrations should be addressed gravely.

Environmental damage caused by coal combustion residue disposal: A critical review of risk assessment methodologies

Coal combustion generates almost 40% of world's electricity. However, it also produces 1.1 billion tons of coal combustion residues (CCR) annually, half of which end up in landfills. Although current regulations require proper lining and monitoring programs, the ubiquitous old, abandoned landfills are often not lined nor included in these programs. In addition, the total number of coal ash disposal sites and their status in the world is unknown. Therefore, this article reviews the environmental damage caused by CCR and three commonly used risk assessment methodologies: leaching assessment, groundwater assessment, and toxicity testing. Leaching methods are usually the first step in coal ash risk assessment, however, a large number of methods with different parameters make a comparison of data difficult. Groundwater pollution is commonly detected near coal ash disposal sites, but other anthropogenic activities may also exist nearby. Therefore, multivariate statistical methods and isotope traces should be used to differentiate between different sources of pollution. So far, both stable (δ¹⁸O, δD, δ¹¹B, δ³⁴S, δ⁷Li) and radiogenic (⁸⁷Sr/⁸⁶Sr, ²⁰⁶Pb/²⁰⁷Pb) isotopes have been successfully used as coal ash pollution tracers. Coal ash also negatively affects biota, reduces the diversity of organisms, affects children's health, and increases the risk for developing various diseases. Toxicity studies are great for early screening of coal ash safety; however, they provide no insights into mechanisms causing the adverse effects. Future directions are also proposed, such as the development of new 'low-level' detection methods for coal ash pollution and sustainable and selective method for recovery of critical elements.

Using Statistical Modeling for Assessing Lettuce Crops Contaminated with Zn, Correlating Plants Growth Characteristics with the Soil Contamination Levels

The aim of the study was to identify new mathematical models and strategies that can characterize the behavior of pollutants accumulating in the soil over time, considering the special characteristics of these chemicals that cannot be degraded or destroyed easily. The paper proposes a statistical model for assessing the accumulation of Zn in the lettuce (Lactuca sativa L.), based on three indicators that characterize the development of lettuce plants over time. The experimental data can be used to obtain interpolated variations of the mass increase functions and to determine several functions that express the time dependence of heavy metal accumulation in the plant. The resulting interpolation functions have multiple applications, being useful in generating predictions for plant growth parameters when they are grown in contaminated environments, determining whether pollutant concentrations may be hazardous for human health, and may be used to verify and validate dynamic mathematical contamination models.

Insights into decontamination of soils by phytoremediation: A detailed account on heavy metal toxicity and mitigation strategies

In the current era of rapid industrialization, the foremost challenge is the management of industrial wastes. Activities such as mining and industrialization spill over a large quantity of toxic waste that pollutes soil, water, and air. This poses a major environmental and health challenge. The toxic heavy metals present in the soil and water are entering the food chain, which in turn causes severe health hazards. Environmental clean-up and reclamation of heavy metal contaminated soil and water are very important, and it necessitates efforts of environmentalists, industrialists, scientists, and policymakers. Phytoremediation is a plant-based approach to remediate heavy metal/organic pollutant contaminated soil and water in an eco-friendly, cost-effective, and permanent way. This review covers the effect of heavy metal toxicity on plant growth and physiological process, the concept of heavy metal accumulation, detoxification, and the mechanisms of tolerance in plants. Based on plants' ability to uptake heavy metals and metabolize them within tissues, phytoremediation techniques have been classified into six types: phytoextraction, phytoimmobilization, phytovolatilization, phytodegradation, rhizofiltration, and rhizodegradation. The development of research in this area led to the identification of metal hyper-accumulators, which could be utilized for reclamation of contaminated soil through phytomining. Concurrently, breeding and biotechnological approaches can enhance the remediation efficiency. Phytoremediation technology, combined with other reclamation technologies/practices, can provide clean soil and water to the ecosystem.

Heavy metal bioaccumulation and morphological changes in Vachellia campechiana (Fabaceae) reveal its potential for phytoextraction of Cr, Cu, and Pb in mine tailings

Vachellia campechiana (Mill Seigler & Ebinger) is widely distributed in Mexico and is a dominant species of tailings in Huautla, in the state of Morelos, Mexico. Mining activities carried out in this region generated about 780 thousand tons of bioavailable heavy metal waste (HMs) that were deposited in the environment without any treatment. This study evaluates the bioaccumulation capacity and morphological changes of V. campechiana growing during 1 year in control or tailing substrates (treatments) under greenhouse conditions. The concentration of six HMs was also measured in roots, leaves, and seeds by atomic absorption spectrophotometry. Five metals showed a similar bioaccumulation pattern in the roots and leaves of V. campechiana grown in both substrates: Pb > Fe > Cr > Cu > Zn. The concentrations of Cr, Cu, and Pb were significantly higher in the roots and leaves of individuals growing on the exposed substrate. The presence of essential metals (Cu, Fe, Zn) was only recorded in the seeds, with similar concentrations in both treatments. Seventeen of 18 morphological characters evaluated in V. campechiana decreased in plants exposed to metals. Pb, Cu, and Fe showed a bioconcentration factor greater than one in roots and leaves. The translocation factor showed the following pattern: Cr > Cu = Pb. In conclusion, V. campechiana is a candidate species to phytoremediate environments contaminated with Pb, Cr, and Cu due to its ability to establish itself and turn into the dominant plant species in polluted sites, its ability to bioaccumulate non-essential metals in roots and leaves, and its high rate of HMs translocation.

Characterization of Fungal Endophytes Isolated from the Metal Hyperaccumulator Plant Vachellia farnesiana Growing in Mine Tailings

Heavy metal pollution has become an environmental and health problem worldwide. With the aim of finding novel strategies for metal bioremediation, endophytic fungi from the heavy metal hyperaccumulator plant Vachellia farnesiana were isolated and characterized. The plants were growing in mine tailings, rich in Zn, Pb, and Cu. Morphological and phylogenetic analyses indicated that the fungal strains belonged to Neocosmospora and Aspergillus genera. The Neocosmospora isolate belongs to the Fusarium solani species complex (FSSC) that groups phytopathogen species. However, in this case the plants from which it was isolated did not show any signs of disease. Both fungal strains were able to remove significant amounts of heavy metals from liquid cultures, either in a mixture of the three metals or each metal in a single culture. In response to lead exposure, the Neocosmospora sp. strain secreted specific novel phenolic compounds other than anthraquinones or naphtoquinones, which have been described in similar situations. The Aspergillus sp. dropped the pH in the medium. High-performance liquid chromatography determinations indicated that this strain secreted mainly glutamic acid in response to lead, a novel mechanism, which has not been reported elsewhere. Malic and succinic acids were also produced in response to lead exposure. Possibly, glutamic and succinic acids (synthesized in the Krebs cycle) can be used to cope with metal toxicity due to the plant providing photosynthates to the fungus. These fungi showed the potential to be used for bioremediation or restoration of metal-polluted environments.

Temperature-driven variation in the removal of heavy metals from contaminated tailings leaching in northern Norway

High amounts of tailings with a low recycling rate are generated during mining and smelting processes, and a lot of environmental problems were caused by heavy metal leaching from tailings. Temperature is a key point in heavy metals leaching, and knowing the effects of temperature on tailings leaching is useful for tailings management. A small-scale batch leaching experiment was conducted at different temperatures to test temperature-driven heavy metal leaching from tailings in the arctic area. The variation in the leaching of heavy metals from tailings was investigated by a small-scale batch leaching experiment. Results showed that 10 °C is a threshold temperature for the leaching activity of the tested elements. Fe, Cr, and Cu are significantly correlated with temperature in the leaching. Leaching rates of Cr, Cu, and Ni increase as temperature rises. Leaching rates of Cr, Cu, Ni, V, and Zn change by a polynomial model with temperatures, whereas that of Fe changes with a linear model. V shows an antagonistic relationship with Cu, Fe, and Ni in the leaching. However, Cu, Cr, Ni, and Fe show a synergistic relationship. Discovering the threshold temperature of leaching tailings in the arctic area and concluding the influence factors and the relationship between heavy metals leaching and temperature are useful for tailings management.