Metal Accumulation Research Articles

Ecological State of Environmental Facilities in the Zone of Influence of the Lipetsk Industrial Agglomeration

It has been found that the accumulation of heavy metals (HM) in environmental facilities of the Lipetsk industrial agglomeration varies significantly and may depend on the technological mode of the companies, the composition of aerosol fallout, soil properties, distance and direction from the emission plume, biological characteristics of plants and other factors. In the area where the Novolipetsk Iron and Steel Works (NLMK) is located, the excess levels of kerosene, gasoline and hydrocarbons in the atmospheric air were detected, as well as increased dust concentrations in the area of the Lipetsk Tractor Plant. At that, the concentrations of gaseous hazardous chemicals in the air of other areas of Lipetsk and agricultural lands at different distances and directions from NLMK did not exceed the established maximum values. The maximum content of HM was recorded in the upper layers of virgin undisturbed soils in the near zone of influence of industrial companies. It was noted that on arable soils the content of HM does not exceed the standard values, with the exception of a number of cases where the content of Fe, Cr, Ni in the grass stand exceeds the permissible level. It was concluded that the research carried out made it possible to identify the main patterns and factors influencing the pollution of environmental facilities, including components of agroecosystems.

A Comparative Study to Explore the Variability of Heavy Metal Concentration in the Teeth of Residents of Non-gated Versus Gated Societies.

Human populations face increasing exposure to heavy metals, which pose significant health risks. Dental tissues, such as dentin and enamel, provide a reliable biomarker for assessing long-term heavy metal exposure due to their stable nature. This study aims to explore the variability of heavy metal concentrations in the teeth dentine of residents living in gated versus non-gated societies near the Yamuna Riveraround the Jamia Millia Islamia, New Delhi, India. Sixty-nine participants were enrolled, 27 from gated societies and 42 from non-gated societies. Participants underwent elective dental extraction,following whichheavy metal concentrations were measured in extracted tooth dentine using atomic absorption spectrophotometry. Demographic data including age, gender, tooth types, and drinking water sources were recorded. Statistical analysis included Mann-Whitney's test, Spearman correlation heatmap, and principal component analysis (PCA). Residents of non-gated societies exhibited significantly (p< 0.005) higher mean concentrations of heavy metals compared to gated societies except for cadmium (p = 0.495). Subgroup analysis based on drinking water sources revealed significant (p<0.001) variations in heavy metal concentrations, suggesting the influence of water quality on environmental exposure. PCA provided insights into underlying trends and correlations among heavy metal variables. This study provides valuable insights into heavy metal contamination among residents living near the Yamuna River, highlighting disparities in exposure based on residential environment and drinking water sources. Participants from non-gated societies exhibited higher mean concentrations of heavy metals compared to those from gated societies, emphasizing the influence of socio-economic factors, urban infrastructure and environmental management practices on heavy metal accumulation. The study's findings underscore the need for targeted interventions to address heavy metal exposure across diverse population groups, improve water quality standards, and enhance access to safe drinking water.

Comparison between Co(II) and Ni(II) cycling at goethite-water interfaces: Interplay with Fe(II)-catalyzed recrystallization

Cobalt (Co) and nickel (Ni) are critical metals for modern renewable energy technologies as well as essential micronutrients for terrestrial plant health and marine primary production. Both metals are commonly surface-adsorbed onto and/or structurally-incorporated into iron (oxyhydr)oxide minerals, such as goethite (α-FeOOH), that are ubiquitously present in soils and sediments at the Earth’s surface. In sub- and anoxic environments, aqueous ferrous iron (Fe(II)) generated from dissimilatory Fe(III) reduction can induce the recrystallization of goethite and subsequently influences the speciation and mobilization of associated metals, e.g., Co(III) being reduced to Co(II). While it is generally considered that divalent Co and Ni behave similarly at goethite-water interfaces, there lacks a direct comparison of their cycling through goethite in response to Fe(II)-catalyzed recrystallization. Here, under circumneutral anoxic conditions with and without addition of aqueous Fe(II), we performed batch reaction experiments on Co(II)-substituted goethite and Co(II) and Ni(II) sorption experiments on pure goethite. The redox state and coordination environment of Co associated with goethite were determined using high energy resolution fluorescence detected X-ray absorption spectroscopy at the Co K-edge, and the distribution of solid-bound Co and Ni in goethite following sorption was revealed by sequential dissolution. Our results show that substitution of Co(II) for Fe(III) in goethite has less negative feedback on Fe(II)-catalyzed recrystallization than Ni(II), which may be related to their differing structural distortions as evidenced by EXAFS. In the absence of Fe(II), aqueous Co(II) is more favourably adsorbed onto and incorporated deeper into goethite than Ni(II), suggesting that Co(II) is more structurally compatible with goethite. The presence of Fe(II) markedly enhances the structural incorporation of both Co(II) and Ni(II) as a result of goethite recrystallization, which in turn can be inhibited by the accumulation of metals at the mineral surface. Furthermore, structurally-incorporated Co(II) is more difficult to be released back into solution (i.e. sum of aqueous and extract fractions) than Ni(II) during Fe(II)-catalyzed goethite recrystallization. Overall, our work highlights the significant differences between Co(II) and Ni(II) in their cycling at goethite-water interfaces and intricate interplay with Fe(II)-catalyzed recrystallization. This improves our understanding of their mobilization and distribution in anoxic goethite-rich systems and can provide useful insights for their enrichment and extraction from natural and artificial laterites generated from the enhanced weathering of ultramafic mine tailings.

Effective soil remediation with fungal Co-inoculation and king grass for robust cadmium and chromium phytoextraction

Bioremediation, an economical and environmentally friendly approach, provides a sustainable solution for mitigating heavy metal contamination in soils. This study identifies four fungal strains—Trichoderma harzianum DAA8, Trichoderma reesei DAA9, Rhizomucor variabilis DFB3, and Trichoderma asperellum LDA4—that exhibit tolerance to cadmium (Cd) and chromium (Cr). These strains were isolated from soils impacted by heavy metal contamination in mining regions. Rigorous examinations of these strains led us to determine their Minimum Inhibitory Concentrations (MICs) and optimal absorption-reduction conditions. Our microscopic data and GC-MS analysis indicate that these strains can accumulate Cd and Cr by generating compounds, such as ketones and imines, in heavy metal environments. We evaluated the remediation efficacy of both single and co-cultures of Rhizomucor variabilis DFB3 and Trichoderma asperellum LDA4 in conjunction with king grass, a plant known for its heavy metal accumulation capabilities. Our findings indicated an impressive 41.9% increase in plant biomass and 47.2% and 64.4% increase in Cd and Cr accumulation respectively. The removal rates of Cd and Cr were 16.5% and 19.0%, respectively, following the co-inoculation of Rhizomucor variabilis DFB3 and Trichoderma asperellum LDA4. These rates represent increases of 37.1% and 33.7% compared to the removal rates achieved with king grass alone. This study not only advances strategies to manage Cd-Cr contamination but also sets a pathway for efficient heavy metal soil remediation using a microbial-plant combined technique.

Influence of municipal waste treated sludge on the quality attributes of African marigold (Tagetes erecta)

Using treated sludge to amend soil in agriculture presents opportunities and challenges, particularly concerning the augmentation of heavy metals in cultivated plants. This research looks into how applying treated sludge affects the buildup of heavy metals in African marigold (Tagetes erecta), a popular ornamental plant that could potentially help with phytoremediation. Several treatment combinations were imposed, out of which treated sludge at 2.5 t/ha showed promising results. The effect of incorporating treated sludge was found to be better in terms of using conventional manures like Farm Yard Manure and Vermicompost in quantitative terms. The sludge processed at the treatment plant underwent strict treatment procedures, resulting in odourless material that can be used as an organic amendment with nutrients. Heavy metal concentrations in plant tissues were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICPMS) to assess the uptake and accumulation of heavy metals by African marigolds. Results indicated that treated sludge application did not significantly influence the accumulation and bioavailability of heavy metals in African marigolds. The treated sludge helped plants grow better and absorb nutrients; it did not cause higher levels of harmful heavy metals like cadmium and lead in the plants. The levels of heavy metals found were lower than what is considered unsafe for plants. In addition, treated sludge can serve as a soil conditioner to enhance the physicochemical properties of the soil.

Impacts of Polyvinyl Alcohol and Chitosan-Modified Biochar on the Anaerobic Digestion of Sewage Sludge and Valuable Resource Recovery

The accumulation of organic dyes and heavy metals (HMs) in sewage sludge (SS) after wastewater treatment is a significant problem due to the non-degradable nature of these pollutants. Moreover, the simultaneous removal of HMs and dyes in the complex process of SS treatment, such as anaerobic digestion (AD), has become attractive. HMs and dyes present in SS can have a detrimental effect on anaerobic digesters. These pollutants not only inhibit the production of methane, which is crucial for biogas generation, but also affect the stability of AD treatment, which can result in failure or inadequate performance of the AD process. This review highlights a novel method of removing HMs and dyes from the AD process of SS through the use of biochar modified with polyvinyl alcohol (PVA) and chitosan (CTS). The applications of conventional biochar have been limited due to poor adsorption capacity. However, modification using PVA/CTS composites enhances properties such as surface functional groups, adsorption capacity, porosity, surface area selectivity, and stability. Furthermore, this modified version can function as an additive in AD of SS treatment to boost biogas production, which is a viable source for heat generation or electricity supply. In addition, the digestates can be further processed through plasma pyrolysis for the removal of HMs and dyes bound to the modified biochar. Plasma pyrolysis generates two major products: syngas and slag. The syngas produced can then be used as a source of hydrogen, heat, and electricity, while the slag can potentially be reused as an AD additive or as a biofertilizer in the agricultural sector. Additionally, this study addresses the challenges associated with this integration and biochar modifications, and offers an outlook on understanding the interactions between the modified biochar properties, microbial dynamics, and the presence of micropollutants to ensure the economic viability and scalability of this technology. This comprehensive review provides insights into the potential of PVA/CTS-modified biochar as an effective additive in AD systems, offering a sustainable approach to SS treatment and valuable resource recovery.

Detangling past and modern zinc anthropogenic source contributions in an urbanized coastal river by combining elemental, isotope and speciation approaches

The accumulation of trace metals in the environmental compartments of coastal rivers is a global and complex environmental issue, requiring multiple tools to constrain the various anthropogenic sources and biogeochemical processes affecting the water quality of these environments. The Valao fluvio-estuarine system (Rio de Janeiro, Brazil) presents a challenging case of a coastal river contaminated by both modern and historical anthropogenic metal sources, located in the land and in the intra-estuary, continuously mixed by tidal cycles. This study employed a combination of spatial distribution analysis of trace metals including gadolinium (Gd), zinc (Zn) isotopic analyses, and X-ray absorption spectroscopy (XAS) to distinguish between these sources. The concentrations of metals in both dissolved (water samples) and surficial sediment compartments (Suspended Particulate Matter and sediment samples) display an overall enrichment trend from upstream to downstream. Multivariate statistical analysis allows to discriminate geogenic elements derived from watershed geology (Ti, K, and Mg) vs anthropogenic contaminants from urban runoff and domestic sewage discharges (Cu, Cr, Pb, Zn, and Gd); and legacy metal contaminants (Zn and Cd) remobilized from ancient metallurgical wastes and transported upstream in the estuary during tidal cycles. The anthropogenic Gd concentration in the dissolved compartment increases along the watercourse, highlighting continuous ongoing sewage discharge. Zinc solid speciation also indicates that Zn contribution from legacy metallurgy waste is primarily associated with sulfide-Zn and Zn-phyllosilicate in the outlet estuary, while in upstream sediments of fluvio-estuarine system, Zn is found bound to organic matter. Zinc isotope systematically reveals a progressive downstream shift to heavier isotope compositions. Upstream, the relatively pristine site and the urbanized section of the river exhibit a relatively uniform δ66/64Zn value (+0.20 ± 0.07 ‰) in suspended particulate matter (SPM) and surficial sediments. These results indicate that domestic sewage discharges contribute to Zn enrichment in sediments of the Valao fluvio-estuarine system but without modifying its isotope signature in sediments. The sediment of the downstream estuarine section shows a heavier δ66/64Zn value (+0.48 ± 0.08 ‰), indicating the strong influence of the intra-estuarine source identified as the historical metallurgic contamination. An integrated view of the geochemical tracers allows thus inferring that the untreated sewage and legacy metallurgical contamination are the primary sources of anthropogenic Zn contamination. It highlights the progressive mixing along the estuarine gradient under tidal dynamics. The influence of the former source continuously expands from the headland towards the estuary.

Comparing the nutritional, phytochemical, and anti-microbial potential of wild and cultivated Tetragonia decumbens mill.: A promising leafy vegetable for bio-saline agriculture in South Africa

Tetragonia decumbens is a neglected edible halophyte that grows naturally in coastal areas of South Africa. Its underutilisation is due to the limited literature on its nutraceutical potential. So, this research was designed to assess the nutritional value, secondary metabolites, and anti-microbial potential of wild and greenhouse cultivated T. decumbens to further support its consumption and potential medicinal use. Samples of T. decumbens were collected from three coastal areas (Strand beach, Muizenberg beach and Blouberg beach) during the dry and wet seasons in Cape Town, and the greenhouse cultivated were subjected to varying salinity doses (0, 50, 100, 150, 200 and 250 mM). Results revealed a considerable increase in minerals (N, P and Mg) and proximate composition (Ash, moisture, and carbohydrates) in greenhouse cultivated plants subjected to 50 mM of salinity while the highest crude fat and neutral detergent fibre were recorded in wild samples. Moreover, heavy metal accumulation (Zn and Fe), phytochemicals, anti-nutrients and anti-microbial activities were more pronounced in wild plants than in cultivated samples. Wild plants collected at Blouberg beach had more heavy metals, anti-nutrients, phytochemicals, and anti-microbial activity. These findings validate for the first time, the relevance of nutritional quality of T. decumbens in assessing its suitability as a source of nutrients and antioxidants with possible medicinal value as shown by the inhibition of harmful bacteria and fungal strains.

Understanding physiological, elemental distribution and bioaccumulation responses of crustose and foliose lichens in the vicinity of coal-based thermal power plant, Raebareli, Uttar Pradesh, India

Environmental pollution, especially from coal-based thermal power plants, poses significant risks to human respiratory health and the environment. This study evaluates the diversity of lichens in the areas. Physiological and bioaccumulation responses of two crustose lichens (Bacidia incongruens and Rindoina sophodes) and one foliose lichen (Pyxine cocoes) in the vicinity of the Feroz Gandhi Unchahar National Thermal Power Corporation, Raebareli, Uttar Pradesh, India were also assessed. These lichens, exposed to emissions including fly ash, greenhouse gases, metals, and particulate matter were analyzed for metal accumulation and physiological responses. Changes in physiological parameters and metal profiles concerning distance from the coal-based thermal power plant to the outskirts were analyzed for B. incongruens, R. sophodes and P. cocoes by utilizing Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The study identified 18 lichen species from 12 genera and 10 families in the area, with Pyxine sorediata newly recorded in Uttar Pradesh. The dominant species, B. incongruens, P. cocoes, and R. sophodes, preferred substrates like Mangifera indica, Acacia nilotica, and Azadirachta indica bark. Physiological analyses revealed variations in pigment concentrations, with significant differences in chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, and chlorophyll degradation, while protein content remained stable. Metal accumulation studies showed nine metals with distinct patterns, B. incongruens had higher concentrations in the west (52730.61 µg g-1) and P. cocoes in the east (23628.32 µg g-1). Correlation analyses indicated significant relationships between paired elements, suggesting specific sources of environmental contamination. This research highlights the significance of integrating physiological and environmental factors to understand lichen responses to coal based thermal power plant.

Interplay of heavy metal accumulation, physiological responses, and microbiome dynamics in lichens: insights and future directions.

Lichens are increasingly recognised as valuable bioindicators for environmental heavy metal pollution due to their sensitivity to spatial and temporal variations in pollution levels and their ability to adapt to diverse and often harsh habitats. This review initially examines the mechanisms of metal absorption in lichens, including particulate entrapment, ion exchange, and intracellular absorption, as well as their physiological responses to abiotic stressors such as heavy metal exposure and desiccation. In the latter part, we compile and synthesise evidence showing that secondary metabolites in lichens are significantly influenced by metal concentrations, with varying impacts across different species. Although extensive research has addressed the broader physiological effects of heavy metal hyperaccumulation in lichens, there remains a significant gap in understanding the direct or indirect influences of heavy metals on the lichen microbiome, possibly mediated by changes in secondary metabolite production. Our review integrates these aspects to propose new research directions aimed at elucidating the mechanisms underlying physiological responses such as resilience and adaptability in lichens. Overall, this review highlights the dynamic interplay between microbiome composition, secondary metabolite variation, and metal accumulation, suggesting that these factors collectively contribute to the physiological responses of lichens in polluted environments.

Quantitative assessment of Cd sources in rice grains through Cd isotopes and MixSIAR model in a typical e-waste dismantling area of Southeast China

Identification of Cd sources and quantification of their contribution to rice grain Cd is crucial for controlling accumulation of this toxic metal in rice grains. However, accurate assessment of the contribution of different Cd sources to grain Cd concentration in rice under actual field conditions is a challenge. In this study, we determined Cd concentration and their isotopic compositions in rice grains with respect to three potential Cd sources around an e-waste dismantling area in Taizhou City, Zhejiang Province, China. Results demonstrated that average Cd concentrations in grains, surface soils, atmospheric deposition and surface water were 0.32, 0.91, 1.99 mg kg−1 and 2.02 μg L−1, respectively. The δ114/110Cd values of grains, surface soils, surface water and atmospheric deposition ranged from 0.00 ‰ to 0.31 ‰, −0.21 ‰ to 0.14 ‰, −0.04 ‰ to 0.47 ‰, and − 0.25 ‰ to −0.18 ‰, respectively. The MixSIAR model indicated that contribution of soils, irrigation water and atmospheric deposition to grain Cd was 56.8 %, 24.8 % and 18.4 %, respectively, demonstrating soils as the major source of grain Cd in the study area. This study also highlighted significant contribution of irrigation water and atmospheric deposition to Cd concentration in rice grains. The Cd isotopic analysis provides a practical approach for source apportionment of grain Cd and data support for controlling Cd accumulation in rice around the e-waste dismantling area.

Phytoremediation potential of seedlings: comparing heavy metal accumulation in Ailanthus, Acer, and Fraxinus species.

This study investigates the phytoremediation potential of non-productive seedlings of Ailanthus altissima, Acer pseudoplatanus, and Fraxinus excelsior for lead, cadmium, and zinc accumulation in contaminated soils of Zanjan Province, an industrial area with significant pollution. The evaluation employed a completely randomized design, with three treatment levels for each element, alongside a control treatment, replicated three times over a two-year period. A total of 810 one-year-old seedlings from the three species were involved in the study. Soil contamination levels, ranging from 0 to 2000mg/kg for lead and zinc and from 0 to 200mg/kg for cadmium, were administered through soil pot irrigation. Sampling of seedling stems and pot soils was conducted in November of 2021 and 2022. The absorption levels of elements in the samples were determined using the dry acid digestion method and an ICP-OES atomic absorption spectrometer. Results indicate species-specific variations in metal absorption, with Ailanthus showing the highest accumulation rates. Findings suggest Ailanthus as a promising candidate for soil improvement in polluted environments, particularly in contaminated soils of Zanjan Province.

Elemental composition and potential toxicity of the riverine macrophyte Podostemum ceratophyllum Michx. reflects land use in eastern North America

Land use influences surface water quality, often alleviating stoichiometric constraints on primary production and altering biogeochemical cycling. However, land use effects on nutrient content and potential trace metal accumulation in aquatic plants remain unclear, and high concentrations of metals and altered nutrient ratios could impact the health of herbivores and detritivores. We tested for land use effects on nutrient and trace metal accumulation in a widespread riverine macrophyte, Podostemum ceratophyllum, collected from 91 locations from Georgia to Maine, USA in 2014–2016. We quantified carbon (C), nitrogen (N), phosphorus (P), their molar and mass ratios, N and C stable isotopes, and 17 additional elements in dried plants collected from each location to estimate relationships between plant tissue content and watershed land use, which we quantified as agriculture, forest, and development. Decreasing forest cover was correlated with increasing δ15N, Mg, Mn, and P in Podostemum tissue. Increasing urban development was correlated with increasing δ15N, Mg and P, while increasing agriculture was correlated with a decrease in C: P and the concentrations of multiple metals, along with increases in P, Mg and δ15N. Decreases in ratios of N: P and C:P with increasing agriculture and urban development in the watershed indicate more rapid P storage relative to C and N in plant tissue, and increased resource quality of the plant to consumers in these watersheds. We also observed potentially toxic dietary concentrations of some trace metals (B, Cd, Tl, Zn) in plant tissue which could be related to the plant's natural herbivory defense system or to land use. We conclude that land use influences the elemental composition of P. ceratophyllum, and potentially the quality and toxicity of the plant to herbivores and detritivores in eastern North American rivers.

Alleviating heavy metal accumulation and pathogens’ abundance through processing proper ratio of duck feces and food waste by Black solider fly larvae

ABSTRACT The efficient and sustainable utilization of duck feces is critically essential in China, given its expansive livestock and poultry breeding industry. While the use of black solider fly (BSF) larvae for composting duck feces has gained recognition, public apprehensions concerning the nutritional value and safety of the resultant by-products remain prevalent. This study presents the inaugural assessment of potential risks and quality of resource-based products derived from various proportions of food waste and duck feces processed by BSF larvae. Our findings indicate that mixed substrate A2 yielded BSF larvae with the highest level of N and P, alongside the lowest accumulation of As, Pb and Cd, as well as reduced total pathogen abundance in the remaining substrate when compared to other mixed substrates (A3 and A4). This suggests that an appropriate nutrient composition ratio in the substrates not only facilitated effective conversion but also diminished heavy metal accumulation by BSF larvae. Additionally, a significant negative correlation was observed between N, P, and Cd (R 2 = −0.989, −0.996, p < 0.01), implying that elevated N and P concentrations in BSF larvae may enhance immune function and while further mitigating heavy metal enrichment. Overall, achieving a suitable nutrient ratio of duck feces and food waste is imperative for their scientific and safe utilization, providing valuable insights for the bioconversion of organic solid waste through BSF larvae.

Macrophytes as Bioindicators of Heavy Metal Pollution in Belarusian Rivers

ABSTRACTMacrophytes are well‐known for accumulating a large number of various substances, including metals, and they may consequently serve as biogeochemical indicators of aquatic system pollution. In general, the sequence of analyzed metal accumulation in river macrophytes is as follows (mg/kg): Mn (141) &gt; Cu (2.53) &gt; V (0.89) &gt; Cr (0.70) &gt; Pb (0.68) &gt; Ni (0.23). Submersed species are conspicuous for their increased metal accumulation capacity, with statistically significant differences compared to other ecological groups. Among the aquatic plant genera examined (Potamogéton, Ceratophýllum, Elodea, Núphar, Butomus, Glycéria, and Spargánium), an increased capacity to accumulate Mn, Cu, and Pb is observed in all submersed macrophytes, while Cr, V, and Ni are particularly accumulated by Ceratophýllum and Elodea. Potamogéton has the largest range of V, Cr, Mn, Ni, and Cu variations. The overall bioaccumulation capability evaluated by the metal accumulation index was ordered as follows: Núphar (6.94) &gt; Potamogéton (5.53) &gt; Butomus (3.48) &gt; Glycéria (2.86) &gt; Spargánium (2.62) &gt; Elodea (2.33) &gt; Ceratophýllum (1.98). Bio‐accumulation factors (BAFs) (macrophytes/sediment) vary depending on the metal and macrophyte ecological groups. For submersed macrophytes, the sequence of BAFs is Mn &gt; Cu &gt; Ni &gt; Pb &gt; Cr &gt; V. In the submersed plants of watercourses taken at the anthropogenic impact sites, the accumulation of Ni, V, Mn, Pb, and Cu is statistically significantly higher compared to those in natural conditions. Compositional data analysis has revealed such biogeochemical signatures of the anthropogenic impact as the formation of the anthropogenic Cr–Ni association, which is associated with the identified multivariate anomalies, as well as an increase in Cu variability and a decrease in Mn.

Comparative assessment of phytoremediation potential of four Ficus spp. under Semi-arid environmental conditions.

Heavy metals have been recognized as a prominent hazard in today's world, causing pollution in the air environment. Woody tree species can play a significant role in the extraction and remediation of metal pollutants from the air, therefore promoting the air quality index. This study investigated the potential of four species of the Ficus genus (F. benjamina, F. microcarpa, F. religiosa, and F. virens) to remediate varying levels of heavy metal contamination in industrial, residential, and highway areas of Faisalabad City, Pakistan. For this purpose, six heavy metals (cadmium, chromium, copper, lead, zinc, and manganese) were assessed in young leaves (YL) as well as old leaves (OL) of subjected tree species at selected study sites. Eight fully expanded leaves were selected from each tree species: two from each cardinal direction from the shoot of the current year (young leaves, YL), as well as from the shoot of the previous year (old leaves, OL). The results showed that the same genus has different capabilities to accumulate different heavy metals, and the overall trend was in the following order: F. virens > F. religiosa > F. benjamina > F. microcarpa at all study sites. The heavy metal contents in both YL and OL of selected tree species decreased in the order of Manganese (Mn)> Zinc (Zn)> Copper (Cu) > Chromium (Cr) > Lead (Pb) > Cadmium (Cd) at all study sites. The metal accumulation index (MAI) values ranged between 2.14-5.42 for F. benjamina, 2.09-3.89 for F. microcarpa, 3.61-7.01 for F. religiosa and 4.77-6.48 for F. virens across all study sites. Among the studied tree species, it has been determined that F. virens and F. religiosa are well-suited for urban areas with significant heavy metal contamination and can be strategically planted in barrier areas to effectively combat atmospheric pollution.

Photoaged tire wear particles hinder the transport of Pb(II) in urban soils under acid rain: Experimental and numerical investigations

Rapid urbanization brought lots of serious environmental contamination, including the accumulation of heavy metals, acid rain, and the emission of tire wear particles (TWPs), with detrimental effects for terrestrial ecosystems. Nevertheless, how naturally aged TWPs affect the mobilization of heavy metals in soils under acid rain is still unclear. Here, we investigate the adsorption and transport mechanisms of Pb(II) co-existing with acid rainwater in soil-TWP mixtures via batch experiments, column experiments and modeling. Results showed that photoaged TWP significantly prolonged the Pb(II) adsorption equilibrium time (1 to 16 h) and enhanced the Pb(II) adsorption capacity of soils. Soil column profiles confirmed that TWP effectively boosted the initial accumulation of lead in the topsoil and thus impeded the downward transport of lead. The retardation factor (R) estimated by the linear two-site sorption model (TSM) fitting the Pb(II) breakthrough curves gradually increased from 1.098 to 16.38 in soils with TWP (0–10 %). Comparative results of linear or nonlinear TSM suggested nonlinear sorption replacing linear sorption as the main Pb(II) sorption mechanism under 1 % and 10 % TWP. This research provides significant insights into the implications of TWP on the Pb(II) retention behaviors and highlights the severer potential remobilization risks of Pb(II) in urban soils under different acid rain environments.

Soilless Production of Lettuce (Lactuca sativa) in the Atacama Desert Using Fog Water: Water Quality and Produce Mineral Composition

Soilless vegetable production in the Atacama Desert of Northern Chile is spreading since it is perceived as an alternative that requires much less water than open field soil production. However, strong competition between mining and urban use for human population consumption exists, forcing growers to use alternative water sources. Fog is commonly present in the coastal areas of Northern Chile; however, little information exists with regards to its chemical composition and the effect on nutrient quality of the produce. To address this knowledge gap, a set of experiments was carried out in Chañaral, a small town located in the Atacama Desert of Northern Chile. There, a 200 m2 greenhouse equipped with twenty deep flow pools was used in two consecutive growing cycles. Water for the mixing of the nutrient solution was collected from the fog using fog-catchers and later stored in 2000-L tanks. Fog water quality (electrical conductivity, pH and mineral content) was monitored directly from the storage tanks. Two types of lettuce, green butterhead and red oak leaf, were compared on their yield and accumulation of nutrients and heavy metals. The results indicate that fog water is of good quality for soilless production, with an electrical conductivity value of 0.65 ± 0.18 and low content of heavy metals. Plants’ heavy metal accumulation is below the recommendation of Food and Agriculture Organization and World Health Organization. Fog water presents as a viable water source for soilless production in Northern Chile.

Genome-Wide Analysis of the Nramp Gene Family in Kenaf (Hibiscus cannabinus): Identification, Expression Analysis, and Response to Cadmium Stress.

Kenaf (Hibiscus cannabinu) is a grass bast fiber crop that has the ability to tolerate and accumulate heavy metals, and it has been considered as a potential heavy metal accumulator and remediation plant. Nramp is a natural resistance-related macrophage, which plays an important role in the transport of divalent metal ions, plant growth and development, and abiotic stress. In this study, the Nramp gene family of kenaf was analyzed at the whole genome level. A total of 15 HcNramp genes were identified. They are distributed unevenly on chromosomes. Phylogenetic analysis classified 15 HcNramp proteins into 3 different subfamilies. All proteins share specific motif 4 and motif 6, and the genes belonging to the same subfamily are similar in structure and motif. The promoters are rich in hormone response, meristem expression, and environmental stress response elements. Under different treatments, the expression levels of HcNramp genes vary in different tissues, and most of them are expressed in roots first. These findings can provide a basis for understanding the potential role of the Nramp gene family in kenaf in response to cadmium (Cd) stress, and are of great significance for screening related Cd tolerance genes in kenaf.

Improving the growth of pea plant by biochar–polyacrylamide association to cope with heavy metal stress under sewage water application in a greenhouse

Sewage water is extensively used for irrigation, serving as a valuable resource for plant growth to enhance agricultural productivity. However, this practice also results in a significant accumulation of heavy metals in the soil, posing potential environmental and health risks. A study was designed to evaluate the combined effect of amendments on heavy metal immobilization in soil and improved growth and yield in pea plants. For this, the soil for each treatment was mixed with biochar (BC) (1% w/w), polyacrylamide (PAM) (0.5% w/w), and also applied in combination. Pea plants were irrigated with tap water (TW), sewage water (SW), and tap + sewage water (TW + SW). A factorial design was applied to analyze data statistically. The combined application of the biochar and polymer showed a positive response by significantly enhancing the plant growth parameters (39%–84%), physiological attributes (67%–69%), and reducing Cd (56%) and Cr (65%) concentration in soil applied with SW and TW + SW. Moreover, treatment with a combined application of BC and PAM significantly reduced Cd concentrations by 43% in roots, 50% in shoots, and 91% in grains. Similarly, Cr concentrations were reduced by 51% in roots, 51% in shoots, and 94% in grains compared to the control. Overall, the study results indicate reduced bioaccumulation and health risks associated with potentially toxic elements (PTEs), supporting the application of the polymer and biochar for irrigating pea plants with TW + SW. Leveraging the combined benefits of polymer and biochar amendments appears to be an effective strategy to remediate PTE-contaminated soil, thereby increasing plant growth and yield.