Human health and ecological risk assessment of heavy metals in topsoil of different peatland use types

Peatlands, known for their ability to retain and immobilize heavy metals due to unique waterlogged conditions and organic matter, face challenges when subjected to disturbances such as land use changes. These disruptions alter the organic matter, redox potential, and pH of the peatsoil, potentially influencing the migration, mobilization, and increased availability of stored heavy metals. Peatsoil samples from various peatland use types (improved and semi-natural grassland, forest, industrial cutaway bog) were collected to assess the human health and ecological risk associated with heavy metals (Cd, Cu, Hg, Pb, and Zn) in Co-Offaly, Ireland. Results reveal variations in heavy metal concentrations across peatland use types, with Cd, Hg, and Pb in improved and semi-natural grassland peatsoils exceeding the World Health Organization (WHO) permissible safety limits. Contamination factors (CF) were higher in improved grassland, especially for Cd and Pb, exceeding one. Hakanson potential ecological risk assessment indicates acceptable overall risk levels, though variations exist between improved grassland, unimproved grassland, forest, and industrial cutaway bog. Combined exposure routes (dermal, ingestion and inhalation routes) to all heavy metals do not exceed safe exposure levels (indicating low non-carcinogenic risks. However, the cancer risk (CR) exceeds acceptable thresholds across all use types, with higher CR in improved grassland, especially for children. Overall, the findings emphasize the need for careful consideration of heavy metal risks associated with land use changes in peatlands, particularly in the improved grassland areas.

Organic Materials Promote Rhododendron simsii Growth and Rhizosphere Soil Properties in a Lead-Zinc Mining Wasteland

The mining of metal minerals generates considerable mining wasteland areas, which are characterized by poor soil properties that hinder plant growth. In this study, a field plot experiment was carried out in the mining wasteland of the Lanping lead-zinc mine in Yunnan Province to study the effects of applying three organic materials-biochar (B), organic fertilizer (OF), and sludge (S)-at concentrations of 1% (mass fraction), on promoting the soil of mining wasteland and the growth of two plant varieties (Huolieniao and Yingshanhong). The results showed that the amount of available nutrients in the surface soil of a mining wasteland could be considerably increased by S and OF compared to the control check (CK). In the rhizosphere soils of two Rhododendron simsii varieties, the application of S increased the available phosphorus (P) content by 66.4% to 108.8% and the alkali-hydrolyzed nitrogen (N) content by 61.7% to 295.5%. However, the contents of available cadmium (Cd) and available lead (Pb) were reduced by 17.1% to 32.0% and 14.8% to 19.0%, respectively. Moreover, three organic materials increased the photosynthetic rate and biomass of two R. simsii varieties. Specifically, OF and S were found to significantly increase the biomass of R. simsii. Organic materials have direct impacts on the increased plant height and biomass of R. simsii. Additionally, organic materials indirectly contribute to the growth of R. simsii by reducing the content of available Cd and available Pb in rhizosphere soil while increasing the content of available nutrients according to the structural equation model (SEM). Overall, S can stabilize Cd and Pb, increase soil nutrient contents, and promote the growth of R. simsii effectively, and has great potential in the vegetation reconstruction of mining wasteland.

Transfer and transformation characteristics of Zn and Cd in soil-rotation plant (Brassica napus L and Oryza sativa L) system and its influencing factors

Rice-rape rotation is a widely practiced cropping system in China. However, changes in soil properties and management could change the bioavailability of Cd, In order to explore the occurrence state, transportation and transformation characteristics of heavy metals Cd and Zn in rice-rape rotation system in Guizhou karst area with high background value of Cd. In the karst rice-rape rotation area, the physical and chemical properties of soil, chemical specifications and activities of Cd and Zn at different soil depths and during various crop growth stages, and the bioaccumulation of Cd and Zn in different tissues of rice and rape were studied by field experiment and laboratory analysis. The bioaccumulation of Cd and Zn and the effects of physical and chemical soil properties on the activities and bioavailabilities of Cd and Zn during rice-rape rotation were explored. The findings revealed that soil particle size, composition, pH, redox potential, soil organic matter, and Cd and Zn contents varied dramatically, especially in deep soils. The physical and chemical properties of the deep and surface soils were significantly related to the bioaccumulation of Cd and Zn. Cd and Zn are activated during crop rotation. Cd was easier to be enriched in rice, while Zn was easier to be enriched in rape. The correlation between Cd and Zn contents in Brassica campestris L and their enrichment abilities were not significant, but that in Oryza sativa L were significant. During rice-rape rotation, the chemical speciations and activities of Cd and Zn changed with the changes of soil properties and waterlogging environment. This study had important basic guiding significance for the evaluation, prevention and control of heavy metal pollution, and improving soil quality in different rotation systems in karst areas, and was conducive to promoting the safe production of rape and rice.

Mobility, bioaccumulation in plants, and risk assessment of metals in soils

Heavy metal contamination of soils is one of the main factors contributing to soil quality decline and loss of biodiversity, which is also associated with plant contamination, as metals accumulate in the surface layer of soils and then enter the trophic chain. The aims of the study were to assess the mobility and bioavailability of metals in soils to plants, and to estimate the ecological and health risks associated with heavy metal content in soils. 320 topsoil and 206 plant samples were collected. Fractional analysis showed that for most of the samples, there was no or low risk associated with the mobility of Cr, Pb, Cu, Ni, Zn, and low and medium for Cd. High and very high metal release risk was only shown for Cd (28 % of samples), and Zn and Pb (2 % of samples). The bioaccumulation factor found moderate levels of accumulation for Cd, Zn, Cu, Ni. High accumulation of Cd and Zn was found in 38 % and 15 % of plant samples. Alivibrio fischeri proved to be a more sensitive indicator of soil ecotoxicity compared to Sinapis alba. In the 81 % of the soil samples found a low probability of adverse effects on ecological receptors associated with exposure to soilborne metals. In the case of human health risk, no harmful health effects were observed due to accidental ingestion of metal-containing soils in the study area. In assessing metal risks, the choice of indicators is crucial. Moreover, the properties of soils have a significant impact on the mobility of metals and their bioaccumulation by plants. This means that the more varied the choice of indicators, the more comprehensive, reliable and close to reality the risk assessment of heavy metals in soils will be.

Phytoaccumulation of Heavy Metals by Sodom Apple (Calotropis procera (Aiton) W. T. Aiton) along an Urban–Rural Gradient

Heavy metals (HMs) are widely recognized for their toxicity and have serious environmental implications as technology advances and public pressure mounts to guarantee the safest and healthiest environment. This study evaluates the phytoremediation potential of HMs i.e., Copper (Cu), Zinc (Zn), Lead (Pb), and Cadmium (Cd) by Calotropis procera (Aiton) W.T. Aiton, also known as Sodom apple, along an urban–rural gradient and its effect on communities’ diversity, forage and medicinal quality in semi-arid region of Khyber Pakhtunkhwa Pakistan. The HM concentration was investigated along with the urban–rural gradients by sampling C. procera and soil samples. Acid-digested samples were tested for metal concentration using an atomic absorption spectrophotometer (AAS). We used principal component analysis and cluster analysis to identify the pattern of metal distribution in plants and soil. To comprehend the species’ diversity of plant communities in polluted sites, the species’ composition of C. procera communities was explored. Our results showed that the concentration of HMs in the soil and plant decreased from Zn to Cd (Zn > Cu > Pb > Cd). Likewise, more than half of the soil metal accumulated in the roots and aerial part of the plant, indicating the bioaccumulation potential of the plant species for these metals. Zn, Cu, Pb, and Cd translocation ratio varied from root > stem > leaf > flower. Root to stem transfer of metal was poor, but strongly mobilized to the leaves when available in the stems. Carthamus lanatus, Sonchus asper, Cynodon dactylon, Xanthium strumarium, and Silybum marianum were the leading species in three groups of 36 plant species. Pearson’s correlation revealed a significant relationship between HM concentrations and diversity indices. Zn and Cu content in the soil influenced plant species richness, Shannon–Wiener index (H′), and evenness index (Eh). Given the environmental toxicity of HMs, Cd concentrations in soil exceeded the permissible level, suggesting residents should be warned about potential health risks. As a result, the species chosen for this study can be employed as a biomonitor and phytoremediator of soil contaminated by these HMs, as it can accumulate HMs to a toxic level.

Bioaccumulation of metals, total phenolic and flavonoid contents and antioxidant activity of Rumex acetosella L. from tailings in Žitkovac (Kosovo & Metohija)

The aim of this study was to determine the bioaccumulation of the metals in Rumex acetosella L. collected from the tailings of abandoned mine in Žitkovac (near Kosovska Mitrovica, Kosovo and Metohija), and to establish the possibility of using those plants for medicinal purposes. Concentrations of heavy metals (Mn, Fe, Pb, Ni, Cr, Cu, Cd, Zn, Ca and Mg) in soil, roots and aboveground parts of R. acetosella were determined by wet mineralization with nitric and perchloric acid. The results of the research indicate that R. acetosella accumulates large amounts of Ni, Cu, Pb, Zn, Cr, and Mn. The total phenol content, the total amount of flavonoids and the antioxidant activity of three different extracts of the root and aboveground parts of R. acetosella were determined by spectrophotometric methods. The acetone extracts contain the highest concentration of phenols and flavonoids. Ethyl acetate has proven to be a solvent that releases the least amount of phenols and flavonoids. The methanol extract of aboveground parts has the highest, while acetone root extract has the lowest antioxidant activity. Rumex acetosella can be used for medicinal purposes, but only collected from uncontaminated soil.

A Combined Remediation Strategy of Arsenic and Cadmium in the Paddy Soil of Polymetallic Mining Areas

The combined pollution of arsenic (As) and cadmium (Cd) are quite common in the polymetallic mining areas located in southern China. In the present study, field experiments were established for the purpose of exploring a simultaneous remediation strategy of rice variety-water management-contaminant immobilization on the As and Cd contamination in paddy soil. The obtained results revealed that the Maba Yinzhan was the best low-accumulation rice variety, with As and Cd concentrations of 0.54 and 0.16 mg kg^-1, respectively, in the rice grains. On the basis of water management during heading stage, the treatment using 0.15 wt% lime plus 0.5 wt% ferro-ferric oxide (FO) decreased the As and Cd concentrations by 64.02% and 34.78%, respectively, in the grains. The results of this study potentially provide an effective remediation solution for the As/Cd contaminated soils in polymetallic mining areas.

Plant Species Diversity of Plant Communities and Heavy Metal Accumulation in Buffer Zone of Momianhe Stream Along a Long-Term Mine Wastes Area, China

The species composition of eight shrub communities were investigated in order to understand the species diversity of plant communities in buffer zone and wetland of Momianhe stream along a long-term mine waste area, Lanping county, Yunnan province, China. Dominant plant species and soil samples were collected to analysis heavy metal (Cu, Zn, Pb and Cd) accumulation characteristics. The results showed that 100% samples for Zn, Pb, Cd, and 87.5% samples for Cu in the investigated area exceeded the Yunnan geochemical background value of the heavy metals in the soil. There were 36 plants species in communities, among which Epilobium pyrricholophum, Elsholtzia argyi, Artemisia vestita, Tripogon chinensis were the dominant species. Plant species, the number of individuals, Ecological Dominance (Do), Shannon-Wiener index (H'), Simpson diversity index (Dsi) and Pielou evenness index (Epi) were affected by Cd and Cu contents of the soil and sediment. Therefore, the results indicate that Cu and Cd contents and ecological risk in the process of long-term vegetation restoration of small catchment in lead-zinc mine waste area should pay more attention.

Pioneer plant species and fungal root endophytes in metal-polluted tailings deposited near human populations and agricultural areas in Northern Mexico

As a consequence of industrial mining activity, high volumes of tailings are scattered around Mexico. Frequently, tailings contain heavy metals (HM) which entail threats against all organisms. The aim of this research was to identify plants and root fungal endophytes in polymetallic polluted tailings with the potential to be used in strategies of bioremediation. Four deposits of mine wastes, situated in a semi-arid region near urban and semi-urban populations, and agricultural areas, were studied. The physical and chemical characteristics of substrates, accumulation of HM in plant tissues, root colonization between arbuscular mycorrizal (AMF) and dark septate endophyte (DSE) fungi, and the identification of DSE fungi isolated from the roots of two plant species were studied. Substrates from all four sites exhibited extreme conditions: high levels in sand; low water retention; poor levels in available phosphorus and nitrogen content; and potentially toxic levels of lead (Pb), cadmium (Cd), and zinc (Zn). The native plants Lupinus campestris, Tagetes lunulata, and Cerdia congestiflora, as well as the exotic Cortaderia selloana and Asphodelus fistulosus, demonstrated a relevant potential role in the phytostabilization and/or phytoextraction of Pb, Cd, and Zn, according to the accumulation of metal in roots and translocation to shoots. Roots of eleven analyzed plant species were differentially co-colonized between AMF and DSE fungi; the presence of arbuscules and microsclerotia suggested an active physiological interaction. Fourteen DSE fungi were isolated from the inner area of roots of T. lunulata and Pennisetum villosum; molecular identification revealed the predominance of Alternaria and other Pleosporales. The use of native DSE fungi could reinforce the establishment of plants for biological reclamation of mine waste in semi-arid climate. Efforts are needed in order to accelerate a vegetation practice of mine wastes under study, which can reduce, in turn, their potential ecotoxicological impact on organisms, human populations, and agricultural areas.

Uptake of Cd, Pb, U, and Zn by plants in floodplain pollution hotspots contributes to secondary contamination

Willows, woody plants of genus Salix common in floodplains of temperate regions, act as plant pumps and translocate the Cd and Zn in the soil profiles of uncontaminated and weakly contaminated floodplains from the sediment bulk to the top strata. We suggest this process occurs because the Cd and Zn concentrations in willow leaves exceed those in the sediments. Senescing foliage of plant species common in floodplains can increase the Cd and Zn ratios as compared to other elements (Pb and common 'lithogenic elements' such as Al) in the top strata of all floodplains, including those that have been severely contaminated. The top enrichment is caused by the root uptake of specific elements by growing plants, which is followed by foliage deposition. Neither the shallow groundwater nor the plant foliage shows that Cd, Zn, and Pb concentrations are related to those in the sediments, but they clearly reflect the shallow groundwater pH, with the risk element mobilised by the acidity that is typical for the subsurface sediments in floodplains. The effect that plants have on the Pb in floodplains is significantly lower than that observed for Cd and Zn, while U can be considered even less mobile than Pb. Groundwater and plant leaves can contribute to secondary contamination with Cd and Zn from floodplain pollution hotspots, meaning that plants can accumulate these elements on the floodplain surface or even return them back to the fluvial transport, even if bank erosion would not occur. For Pb and U at the sites studied, these risks were negligible.

Variation, distribution, and diversity of canonical ammonia-oxidizing microorganisms and complete-nitrifying bacteria in highly contaminated ecological restoration regions in the Siding mine area

Canonical ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB) and complete-nitrifying bacteria (comammox) exist in a variety of ecosystems. However, little is known about AOA, AOB and comammox or their contributions to nitrification in the soils of heavily degraded and acidic mine regions. In the present study, the activity, richness, diversity and distribution patterns of AOA, AOB and comammox in the Siding mine area were investigated. Nemerow's multifactor pollution index (P_N) values indicated that the soil in all three areas in the Siding mine area was highly contaminated by Cd, Pb, Zn, Mn and Cu. The AOA, AOB and comammox amoA gene copy numbers exhibited significant positive correlations with Pb and Zn levels and P_N values, which indicated that the populations of AOA, AOB and comammox underwent adaptation and reproduction in response to pollution from multiple metals in the Siding mine area. Among them, the abundance of AOA was the highest, and AOA may survive better than AOB and comammox under such severely pollution-stressed and ammonia-limited conditions. The phyla Thaumarchaeota and Crenarchaeota may play vital roles in the soil ammonia oxidation process. Unlike AOA, AOB may use soil available phosphorus to help them compete for NH₃ and other limiting nutrients with AOA and heterotrophs. Moreover, soil organic matter was the main factor influencing the species diversity of AOB, the β-diversity of AOB and comammox, and the community composition of AOA, AOB and comammox. Our research will help to explain the role and importance of AOA, AOB and comammox in the different ecological restoration regions in the Siding mine area.

Enhancement of exchangeable Cd and Pb immobilization in contaminated soil using Mg/Al LDH-zeolite as an effective adsorbent

In the present study, experiments using zeolite and Mg/Al LDH-zeolite for immobilization of Cd and Pb ions in artificial soil were conducted. The conditions which affect Cd and Pb ion immobilization in soil were evaluated, namely soil pH (5-7), the mass ratio of adsorbents (1%, 3% and 5%), incubation time (15 days, 30 days and 45 days) and soil moisture (30%, 50% and 70%). The results indicated that the optimal soil pH, mass ratio of adsorbents, incubation time and soil moisture for immobilization of Cd and Pb ions by the adsorbent were, respectively, 7.0, 3%, 30 days and 70%. The exchangeable Cd ion content in the contaminated soil dropped from 22.17 mg kg-1 (87.65%) to 11.03 mg kg-1 (43.48%) and 6.47 mg kg-1 (26.36%) on incubation with zeolite and Mg/Al LDH-zeolite, respectively, while the exchangeable Pb content fell from 23.28 mg kg-1 (90.02%) to 14.12 mg kg-1 (54.04%) and 9.47 mg kg-1 (35.24%) using zeolite and Mg/Al LDH-zeolite as absorbents in contaminated soil, respectively. Fe-Mn oxide occluded (F2), carbonate bound (F3) and organically complexed (F4) were the main forms for immobilization of the exchangeable Cd and Pb when the zeolite and Mg/Al LDH-zeolite absorbents were separately cultivated into soil. Precipitation, co-precipitation and electrostatic attraction were the main mechanisms of exchangeable Cd and Pb immobilization onto the Mg/Al LDH-zeolite to form carbonate metals (CdCO3 and PbCO3). This was due to the surface functional groups of the adsorbent and the presence of Fe and Al oxyhydroxides, Mn oxides, and Si and O elements in the Mg/Al LDH-zeolite's constituents. The efficiency of Cd and Pb immobilization by the Mg/Al LDH-zeolite was higher than that by zeolite from 1.5 to 1.6 times. The Mg/Al LDH-zeolite showed an enhanced ability of exchangeable Cd and Pb immobilization in contaminated soil.

Heavy Metals and Pesticides Toxicity in Agricultural Soil and Plants: Ecological Risks and Human Health Implications

Environmental problems have always received immense attention from scientists. Toxicants pollution is a critical environmental concern that has posed serious threats to human health and agricultural production. Heavy metals and pesticides are top of the list of environmental toxicants endangering nature. This review focuses on the toxic effect of heavy metals (cadmium (Cd), lead (Pb), copper (Cu), and zinc (Zn)) and pesticides (insecticides, herbicides, and fungicides) adversely influencing the agricultural ecosystem (plant and soil) and human health. Furthermore, heavy metals accumulation and pesticide residues in soils and plants have been discussed in detail. In addition, the characteristics of contaminated soil and plant physiological parameters have been reviewed. Moreover, human diseases caused by exposure to heavy metals and pesticides were also reported. The bioaccumulation, mechanism of action, and transmission pathways of both heavy metals and pesticides are emphasized. In addition, the bioavailability in soil and plant uptake of these contaminants has also been considered. Meanwhile, the synergistic and antagonistic interactions between heavy metals and pesticides and their combined toxic effects have been discussed. Previous relevant studies are included to cover all aspects of this review. The information in this review provides deep insights into the understanding of environmental toxicants and their hazardous effects.

Implications of the Phytoremediation of Heavy Metal Contamination of Soils and Wild Plants in the Industrial Area of Haina, Dominican Republic

The study evaluates pollution by Pb, Zn, and Cr, and a possible sustainable solution through phytoremediation technologies, in the surroundings of Haina, a very polluted area of the Dominican Republic. Soils and plants were analyzed at 11 sampling points. After sample processing, the elemental composition was analyzed by ICP-OES. Soil metal concentrations, contaminating factors, pollution load indexes, and the Nemerow pollution index were assessed. Soil metal concentrations showed Pb > Zn > Cr, resulting in very strong Pb pollution and medium-impact Zn pollution, with an anthropogenic origin in some sites. This means that some agricultural and residential restrictions must be applied. Accumulation levels in plant tissues, bioaccumulation factors in roots and shoots, and translocation factors were determined for Acalypha alopecuroidea, Achyranthes aspera, Amaranthus dubius, Bidenspilosa, Heliotropium angiospermum, Parthenium hysterophorus, and Sida rhombifolia. The vast majority of the plants showed very low levels of the potentially toxic elements studied, although it may be advisable to take precautions before consumption as they are all considered edible, fodder, and/or medicinal plants. Despite their low rate of bioaccumulation, most of the plants studied could be suitable for the application of phytoremediation of Zn in the field, although further studies are needed to assess their potential for this.

Cadmium Bioavailability and Accumulation in Rice Grain are Controlled by pH and Ca in Paddy Soils with High Geological Background of Transportation and Deposition

Cadmium (Cd) threatens rice quality and human health, yet this risk remains uncertain in paddy fields with high geological background of transportation and deposition. In this study, we collected 31 pairs of soil and rice grain samples in Doumen and Xinhui Districts in Guangdong province, China and investigated which factors controlled Cd bioavailability in soil and accumulation in rice. Soil samples were mostly acidic and contained a range of organic matter. Total Cd in soil varied from 0.10 to 1.03 mg kg^- 1 and was positively correlated with those of calcium (Ca), manganese (Mn) and iron (Fe), suggesting that these elements shared same sources and Cd was most likely originated from parent material. The activity ratio (AR, CaCl₂-extractable Cd/soil Cd) and bioconcentration factor (BCF, rice grain Cd/soil Cd) of Cd were negatively correlated with soil pH. The coupling relationship between soil and rice grain Cd could be described by a linear model, which was used to predict soil Cd threshold values to keep rice grain Cd concentration from exceeding the Chinese limit (0.2 mg kg^- 1). In summary, Cd pollution was not very severe in the paddy soils of studied area but the risk could not be neglected when soil was acidified, which could increase Cd bioavailability and accumulation in rice grain.

Potential of Grasses in Phytolith Production in Soils Contaminated with Cadmium

Cadmium (Cd) is a very toxic heavy metal occurring in places with anthropogenic activities, making it one of the most important environmental pollutants. Phytoremediation plants are used for recovery of metal-contaminated soils by their ability to absorb and tolerate high concentrations of heavy metals. This paper aims to evaluate the potential of grasses in phytolith production in soils contaminated with Cd. The experiments, separated by soil types (Typic Quartzipsamment, Xanthic Hapludox and Rhodic Hapludox), were conducted in a completely randomized design with a distribution of treatments in a 3 × 4 factorial scheme with three replications. The factors were three grasses (Urochloa decumbens, Urochloa brizantha andMegathyrsus maximus) and four concentrations of Cd applied in soils (0, 2, 4 and 12 mg kg⁻¹). Grass growth decreased and increased Cd concentration in shoots of grasses with the increased Cd rates in soils. The toxic effect of Cd resulted in production and Cd occlusion in phytoliths produced in shoots of the grasses. Grasses showed potential for phytolith production, independent of soil type, providing phytoextraction of Cd in phytoliths. Megathyrsus maximus was the grass with the highest tolerance to Cd, evidenced by higher production and Cd capture in phytoliths for the evaluated soils. Phytolith production by grasses in Cd-contaminated soils is related to genetic and physiological differences of the evaluated grasses and Cd availability in soils.

Endosperm prevents toxic amounts of Zn from accumulating in the seed embryo – an adaptation to metalliferous sites in metal-tolerant Biscutella laevigata

The pseudometallophyte Biscutella laevigata adapts to metalliferous soils by allocating excess metal(loid)s to the endosperm (E) of seeds to protect embryonic tissues and improve reproductive success.

Environmental risk related to presence and mobility of As, Cd and Tl in soils in the vicinity of a metallurgical plant - Long-term observations

Analysis of the content of As, Cd and Tl accompanying Zn-Pb ores was performed using soil material sampled around the zinc-works in Miasteczko Śląskie. It was found that the total content of As, Cd and Tl was considerably higher than the values recorded at the same sites 20 years earlier. This clearly confirms considerable pollution of the environment which continues despite pro-ecological actions taken by the zinc-works. The analysis of the spatial distribution of pollution revealed that the zinc-works itself is no longer the main source of contamination as was the case in 1998. Instead, in 2018 the main sources of As, Cd and Tl emissions were the erosion and deflation processes in old, unprotected mining and industrial waste dumps located near the zinc-works. The most polluted soil layers are the top layers in the soil profile. The content of As, Cd and Tl determined in them was 10 times greater than in the deep layers. There was also a positive change in environmental conditions, which occurred over the preceding 20 years, namely an increase in the content of sparingly soluble fractions, fractions bound with organic matter, and residual fractions. It was also found that depending on the geochemical background and readily mobile fraction values used in the calculations, there is still very high contamination and very high ecological risk with respect to As, Cd and Tl after 20 years. However, when using the quantity of phytoavailable elements as well as the quantity of cations on ion exchange positions and bound to carbonates to calculate the risk assessment code, the analysis showed that environmental conditions improved.

Metal(loid) induced toxicity and defense mechanisms in Spinacia oleracea L.: Ecological hazard and Prospects for phytoremediation

A pot study was conducted to assess the phytoremediation potential of Spinach plants along with their physiological and biochemical response when grown in soil contaminated with heavy metal(loid)s (HMs). Plants were grown under different doses of Pb, Cd and As; and their metal(loid) accumulation efficiency was studied upon harvest; expressed in terms of bioabsorption coefficient (BAC), bioconcentration factor (BCF) and translocation factor (TF). Results showed significant (p ≤ 0.05) difference in physiological and biochemical mechanisms of plants as detected through decrease in concentration of cellular constituents (pigments, carbohydrates, total nitrogen content); and increase in antioxidants (both enzymatic and non-enzymatic). Despite of accumulating high amount of HMs in tissues, no visible signs of toxicity were seen; and hence the efficient survival and defense mechanism shown by spinach plants conclude that they are a viable option to be used for phytoremediation of sites contaminated with Cd and Pb. Since the content of Cd and Pb in edible part was higher than safe limits prescribed by USEPA, the present investigation also highlights the ecological hazards that may result upon cultivation of spinach in contaminated soil for agricultural purpose; or its accidental exposure to food chain when grown for phytoremediation.

Phytoremediation potential and physiological response of Miscanthus × giganteus cultivated on fertilized and non-fertilized flotation tailings

A 2-year field experiment was carried out with aim to assess the phytoremediation potential of Miscanthus × giganteus cultivated on the flotation tailings and to evaluate the effects of mineral NPK fertilizer on metal accumulation and plant physiological parameters and growth. Flotation tailings of the mine Rudnik (Serbia) are burdened with Pb, Cu and Zn and cause heavy metal pollution and deterioration of the surrounding ecosystems. In the second year of growth, plants retained the major portion of metals within their roots, with bioconcentration factor > 1 for Cu and Zn and < 1 for Pb. Their translocation factors were far below 1, showing that M. × giganteus acts as excluder of Cu, Zn and especially Pb. Higher amounts of Pb and Zn in leaves reduced the photosynthetic rate and total antioxidative capacity, but increased lipid peroxidation level. Changes at physiological level resulted in pronounced leaf senescence, reduced plant growth rate and annual biomass yield. Fertilization enhanced metal uptake by plant roots, but had no effect on their translocation to leaves. It improved chlorophyll a content, potential efficiency of Photosystem II photochemistry and biomass yield. Overall results indicate that M. × giganteus can be cultivated on the abandoned flotation tailings and that fertilization had positive effects on its physiology and growth.

A review on global metal accumulators-mechanism, enhancement, commercial application, and research trend

The biosphere is polluted with metals due to burning of fossil fuels, pesticides, fertilizers, and mining. The metals interfere with soil conservations such as contaminating aqueous waste streams and groundwater, and the evidence of this has been recorded since 1900. Heavy metals also impact human health; therefore, the emancipation of the environment from these environmental pollutants is critical. Traditionally, techniques to remove these metals include soil washing, removal, and excavation. Metal-accumulating plants could be utilized to remove these metal pollutants which would be an alternative option that would simultaneously benefit commercially and at the same time clean the environment from these pollutants. Commercial application of pollutant metals includes biofortification, phytomining, phytoremediation, and intercropping. This review discusses about the metal-accumulating plants, mechanism of metal accumulation, enhancement of metal accumulation, potential commercial applications, research trends, and research progress to enhance the metal accumulation, benefits, and limitations of metal accumulators. The review identified that the metal accumulator plants only survive in low or medium polluted environments with heavy metals. Also, more research is required about metal accumulators in terms of genetics, breeding potential, agronomics, and the disease spectrum. Moreover, metal accumulators' ability to uptake metals need to be optimized by enhancing metal transportation, transformation, tolerance to toxicity, and volatilization in the plant. This review would benefit the industries and environment management authorities as it provides up-to-date research information about the metal accumulators, limitation of the technology, and what could be done to improve the metal enhancement in the future.

Effects of manganese stress on phenology and biomass allocation in Xanthium strumarium from metalliferous and non-metalliferous sites

Xanthium strumarium is an annual pseudometallophyte. To reveal the mechanisms of this species to adapt to metallicolous environmental conditions, phenological traits and biomass allocation of metallicolous and non-metallicolous populations of X. strumarium under six Mn²⁺ concentrations by pot culture experiments were performed. The results showed that both time to bolting and time to fruit setting in the metallicolous population were earlier than those in the non-metallicolous population. The number of flowers, fruits, seeds and 1000-seed weight in the metallicolous population were higher than those in the non-metallicolous population under Mn stress. Reproductive allocation and harvest index in the metallicolous population were higher than those in the non-metallicolous population. Furthermore, all the Mn concentrations in leaves, stems, roots, and fruits of the metallicolous population were higher than the counterparts of non-metallicolous population. These results suggested that metallicolous population had higher tolerance to Mn stress than non-metallicolous population, the earlier flowering and fruiting, and the enhancement in reproductive allocation may contribute to plant tolerance to Mn toxicity for X. strumarium.

Micro- and macroelement contents in the liver of farm and wild animals and the health risks involved in liver consumption

The paper presents the macroelement (Al, Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn) and microelement (As, Cd, Co, Cr, Hg, Mo, Ni, Pb, and Sn) contents found in the liver of wild animals (boar and deer) and farm animals (rabbit, chicken, duck, cow, goat, and turkey). Statistically, the differences in element contents between the two groups were not significant (at p = 0.05), with the exception of Fe, K, Mg, Cd, Hg, Mo, and Pb. The liver of farm animals contained more Al, Cu, K, Mg, Na, Cr, and Sn, while the content of the remaining elements was higher in wild animals. An analysis of correlations between element content and age in wild animals (boar) showed that Pb and Al content increases with age, while Na and Cr contents decrease significantly. Comparisons between the test results and the maximum limits allowed by law showed that, in the case of wild animals, the regulatory limits were exceeded in 18% (for Cd and Cu) and 9% (for Hg) of the liver samples analyzed. In the case of farm animals, the limits for micro- and macroelement contents were not exceeded. The hazard index (HI) values for farm animals were lower than for wild animals, with regard to consumption by both children and adults. Based on the HI values calculated, it seems recommendable that consumption of the liver (preferably from farm animals) by children be limited to once weekly. For adults, the liver can be a valuable source of elements such as Zn, Fe, and Cr, which may be an indication for more frequent consumption.