Heavy Metal Uptake Research Articles

Association between heavy metal uptake and growth and reproduction in the anecic earthworm, Alma nilotica (Grube 1855).

Elevated heavy metal concentrations in soils are a cause for concern as they are hazardous to soil organisms including earthworms which are considered as ecosystem engineers. Current ecotoxicity tests predominantly use temperate earthworm species, and thus there is the need to include a broader genera of native species to improve ecological risk assessment. Alma nilotica, is a tropical anecic earthworm species that survives well under laboratory conditions and has potential for use in ecotoxicology testing but lacks published toxicity data for important pollutants. Growth and reproduction bioassays were carried out with A. nilotica to determine the relationship between the concentrations of Cu, Zn, Pb and Cr in spiked soils and their bioaccumulation and toxic effects. Positive linear relationships were found between soil-metal and internal earthworm-metal concentrations. Cu did not inhibit growth up to 35 days of exposure but became toxic with longer exposure duration. Zn was not regulated by A. nilotica although it is an essential metal that is well regulated by Eisenia sp. commonly used in standard ecotoxicity tests, showing differences in metal regulation by earthworms of different ecological categories. Based on bioaccumulation factors (BAFs), growth inhibition and reproduction effects the metals were ranked in decreasing toxicity as Pb > Cr > Zn > Cu. The mean 20% Internal Effects Concentrations (IEC20s) for reproduction were 1.04, 2.9, 8.3 and 224.2 mg metal kg-1 earthworm for Pb, Cr, Zn and Cu respectively. These data can contribute to the improvement of metal risk assessment particularly in tropical contexts.

Analysis of Heavy Metal Impacts on Cereal Crop Growth and Development in Contaminated Soils

The impact of heavy metal presence in soil on cereal crops is a growing concern, posing significant challenges to global food security and environmental sustainability. Cereal crops, vital sources of nutrition, face the risk of contamination with toxic heavy metals released into the environment through human activities. This paper explores key aspects requiring thorough investigation to foster innovation and understand intricate interactions between heavy metals and cereals. Visible symptoms and physiological changes resulting from heavy metal contamination, such as chlorosis and stunted growth, demand further research to devise targeted mitigation strategies and sustainable agricultural practices. Root barrier formation, mycorrhizal symbiosis, and metal-binding proteins emerge as critical defence mechanisms for combating heavy metal stress, offering opportunities for developing metal-tolerant cereal varieties. Research on metal bioavailability and food safety implications in cereal grains is vital to safeguard human health. This paper reveals that multidisciplinary collaboration and cutting-edge technologies are essential for promoting innovation beyond the state of the art in elucidating and mitigating the impacts of heavy metals on cereal crops. Genetic and breeding approaches show promise in developing metal-tolerant cereal varieties, while agronomic practices and soil amendments can reduce metal bioavailability and toxicity. Unravelling the complex mechanisms underlying heavy metal uptake and tolerance is essential for sustainable cereal agriculture and worldwide food sustainability. Embracing the challenges of heavy metal pollution through proactive research and collaboration can secure a resilient future for cereal crops amid evolving environmental conditions.

Potato, a Goldmine, Now a Biological Time Bomb: A Case Study of Uptake of Heavy Metals by Tubers of Potato in Jos-Nigeria

Potato, a Goldmine, Now a Biological Time Bomb: A Case Study of Uptake of Heavy Metals by Tubers of Potato in Jos-Nigeria

Utilization of post-tin mining land for porang (Amorphaphillus oncophyllus) cultivation by application of cow manure compost

Tailing post-tin mining land has a sandy textured and loose structure. Those physical properties can affect the efficiency of fertilization and cause inefficiency of nutrient absorption in plants. That issue can be corrected by the application of organic material such as cow manure compost which has the potential for plant cultivation, especially for “porang” (<em>Amorphaphillus oncophyllus</em> Prain). This study aimed to examine the cultivation of porang plants in post-tin mining tailings by applying cow manure compost and to determine the best dose of cow manure compost for porang cultivation in artificial ex-tin mining land. This study used a single-group randomized design method with the treatment factor being the dose of cow manure compost consisting of five dose levels (5 t ha<strong><sup>-1</sup></strong>, 10 t ha<strong><sup>-1</sup></strong>, 15 t ha<strong><sup>-1</sup></strong>, 20 t ha<strong><sup>-1</sup></strong>, and 25 t ha<strong><sup>-1</sup></strong>). Each treatment level was replicated with five replications, and each replication consisted of five populations so the total population was 125 plants. The results showed that the application of various doses of cow manure compost to artificial post-tin mining land affected the growth and yield of porang plants. The treatment of cow manure compost at a dose of 25 t ha<strong><sup>-1</sup></strong> gave the best growth and yield of porang plants. Heavy metal (Pb) analysis on porang tubers showed that all doses of cow manure compost had a Pb content value of <0.059%, which means that cow manure compost can reduce heavy metal uptake in porang tubers. Porang planted in artificial post-tin mining land is safe for consumption because lead (Pb) content was below the threshold of Indonesia National Standard (SNI) for food.

Biomass Assessment and Optimization of Alcaligenes faecalis Isolated from some Nigerian Mining Sites for Heavy Metal Uptake Using Response Surface Methodology Model

In this study, we investigated the heavy metal absorption of Alcaligenes faecalis strain U.B.I., a bacteria isolated from a mining site, under different environmental conditions. We utilized both conventional and molecular techniques to identify the bacteria and employed response surface methodology (R.S.M.) to determine optimal environmental conditions for heavy metal absorption. Our analysis revealed that the heavy metal-tolerant bacteria belong to the Proteobacteria, specifically the Betaproteobacteria order in the Burkholderiales family. Additionally, the bacteria’s phylogenetic characteristics indicated a close relationship between the Aeromonas sp. cluster and members of the Aeromonadaceae family. Our results showed that the biomass A. faecalis strain U.B.I. had an optimal potential for chromium (Cr+) absorption at 93.0%. We also conducted tests on the biomass under optimized conditions for lead (Pb2+) absorption using R.S.M., resulting in a mean heavy metal uptake of 89.99%. Furthermore, we analyzed the surface functional groups after interaction with heavy metals and observed a significant shift in position of the functional groups. The O-H stretch and H-bonded at the 3268 cm1 position, while C=C stretch and N-O asymmetrical stretch/C-O stretch occurred at positions 2195 cm-1 and 1629 cm-1 of the spectra, respectively. Our findings suggest that the biomass of A. faecalis strain U.B.I. has potential for heavy metal bioremediation and can be used for heavy metal biosorption under various environmental conditions.

Enhancing remediation potential of heavy metal contaminated soils through synergistic application of microbial inoculants and legumes.

Soil microorganisms play a crucial role in remediating contaminated soils in modern ecosystems. However, the potential of combining microorganisms with legumes to enhance the remediation of heavy metal-contaminated soils remains unexplored. To investigate this, we isolated and purified a highly efficient cadmium and lead-tolerant strain. Through soil-cultivated pot experiments with two leguminous plants (Robinia pseudoacacia L. and Sophora xanthantha), we studied the effects of applying this microbial agent on plant nutrient uptake of soil nutrients, heavy metal accumulation, and the dynamics of heavy metal content. Additionally, we examined the response characteristics of inter-root microbial and bacterial communities. The results demonstrated that microorganisms screened from heavy metal-contaminated soil environments exhibited strong survival and adaptability in heavy metal solutions. The use of the Serratia marcescens WZ14 strain-phytoremediation significantly increased the soil's ammonium nitrogen (AN) and organic carbon (OC) contents compared to monoculture. In addition, the lead (Pb) and cadmium (Cd) contents of the soil significantly decreased after combined remediation than those of the soil before potting. However, the remediation effects on Pb- and Cd-contaminated soils differed between the two legumes following the Serratia marcescens WZ14 inoculation. The combined restoration altered the composition of the plant inter-rhizosphere bacterial community, with the increase in the relative abundance of both Proteobacteria and Firmicutes. Overall, the combined remediation using the tolerant strain WZ14 with legumes proved advantageous. It effectively reduced the heavy metal content of the soil, minimized the risk of heavy metal migration, and enhanced heavy metal uptake, accumulation, and translocation in the legumes of S. xanthantha and R. pseudoacacia. Additionally, it improved the adaptability and resistance of both legumes, leading to an overall improvement in the soil's environmental quality. These studies can offer primary data and technical support for remediating and treating Cd and Pb in soils, as well as rehabilitating mining sites.

Tissue localization and the physiological effects induced by an environmentally relevant mix of heavy metals in the liverwort Conocephalum conicum L. Dum

Tissue accumulation, ultrastructural alterations, oxidative stress, and effects on photosynthesis were assessed in the liverwort Conocephalum conicom exposed in vitro to heavy metals (HM) concentrations in three sites of the Savone River, representative of different anthropic impacts. The uptake and accumulation of HM in the thallus of the liverwort was first studied, and the biological effects in relation to the different accumulation sites of HM along thallus, ribs and wings, were then investigated, considering: bioaccumulation (by atomic absorption spectrometry), localization (by X-ray scanning electron microscopy microanalysis), ultrastructural damage of photosynthetic parenchyma (by transmission electron microscopy), oxidative stress (by ROS contents and antioxidant enzymes activities determination), photosynthesis (by chlorophyll fluorescence). The results showed the HM bioaccumulation in C. conicom was dependent by their concentrations in the contaminated water. As for spatial localization, HM preferentially accumulated in the nerve of gametophytes respect to the wings. With respect to tissue localization, HM were mainly found in the hyaline and in the photosynthetic parenchyma. Essential metals (Cu and Zn) were accumulated at higher concentrations with respect to non-essential metals (Pb and Cd). At the ultrastructural level, HM caused alterations of the fine structure of the cells, most evident along the nerve, inducing marked alterations of the chloroplast structure and therefore of the photosynthetic capacity. Based on the results of the presented study, C.conicum can be used as a marker to indicate heavy metal pollution in water natural resources.

Genetic adaptations in the population history of Arabidopsis thaliana.

A population encounters a variety of environmental stresses, so the full source of its resilience can only be captured by collecting all the signatures of adaptation to the selection of the local environment in its population history. Based on the multiomic data of Arabidopsis thaliana, we constructed a database of phenotypic adaptations (p-adaptations) and gene expression (e-adaptations) adaptations in the population. Through the enrichment analysis of the identified adaptations, we inferred a likely scenario of adaptation that is consistent with the biological evidence from experimental work. We analyzed the dynamics of the allele frequencies at the 23,880 QTLs of 174 traits and 8,618 eQTLs of 1,829 genes with respect to the total SNPs in the genomes and identified 650 p-adaptations and 3,925 e-adaptations [false discovery rate (FDR) = 0.05]. The population underwent large-scale p-adaptations and e-adaptations along 4 lineages. Extremely cold winters and short summers prolonged seed dormancy and expanded the root system architecture. Low temperatures prolonged the growing season, and low light intensity required the increased chloroplast activity. The subtropical and humid environment enhanced phytohormone signaling pathways in response to the biotic and abiotic stresses. Exposure to heavy metals selected alleles for lower heavy metal uptake from soil, lower growth rate, lower resistance to bacteria, and higher expression of photosynthetic genes were selected. The p-adaptations are directly interpretable, while the coadapted gene expressions reflect the physiological requirements for the adaptation. The integration of this information characterizes when and where the population has experienced environmental stress and how the population responded at the molecular level.

Towards a clean environment: To what extent can trees serve as phytoremediators for chemically polluted soils?

The study investigated the potential of five common tree species in West Africa to bioaccumulate heavy metals in their various plant components over the course of different growth phases and at varying contamination levels (control, double the permissible level and triple the permissible limit). Heavy metals in plant tissues were extracted and analyzed using standard wet chemistry procedures. The results showed metal concentrations in tree tissues to positively and significantly correlate with contamination level, growth stage, and plant component. Metal mobility and availability in the tree tissues were in descending order of Mn >Zn>Cu=Pb>Cd. We found heavy metals to be principally accumulated in the stem tissues following a metal exclusion theory, independent of tree species. Tree roots demonstrated a significant accumulation of heavy metals second only to the stem. The results revealed that heavy metal mobility and bioavailability in plant tissue was tree-specific, growth stage-dependent, and metal-specific; showing that trees have a preferential affinity to accumulate a specific metal or pollutant. The study established Shorea roxborghi to be a mono-accumulator of manganese while Tectona grandis and Terminalia ivorensis were multi-accumulators of metals such as Mn, Cu, Zn and Pb. The interactive effects of contamination levels and tree species showed Tectona grandis and Terminalia ivorensis grown in chemically polluted soils at triple the permissible level to have the highest heavy metal uptake with the highest phytoextraction potential. We conclude that all the tree species considered in this study could potentially be effective phytoremediators of chemically polluted soils through their ability in phytoextraction of metals such as lead, zinc, copper, and manganese as well as through phytostabilization of cadmium in contaminated soils.

Concentration and Distribution of Toxic and Essential Elements in Traditional Rice Varieties of Sri Lanka Grown on an Anuradhapura District Farm.

Toxic heavy metals have been the focus of many investigations into chronic kidney disease of unknown aetiology (CKDu) within Sri Lanka. It has been hypothesised that exposure to nephrotoxic arsenic, cadmium and lead could play a role in the development of CKDu, and these metals have previously been found in unsafe concentrations in Sri Lankan rice. Traditional varieties of Sri Lankan rice remain popular due to their perceived health benefits, but their uptake of trace and toxic heavy metals remained unexplored. Here, we report a one-time, cross-sectional dataset on the concentrations of essential and toxic elements present in eleven samples of polished and unpolished traditional rice varieties, all regularly grown and sold in the Anuradhapura district, a CKDu hotspot. All rice was sourced from the same farm, with the exception of one store bought sample grown on another, unidentified farm. Cadmium concentrations varied significantly between varieties, and potentially unsafe concentrations of cadmium were detected in the store-bought sample (Suwadel, 113±13 μg kg-1). Elemental imaging of the grains revealed lead to be stored mainly in the rice bran, which is removed during polishing, while cadmium was distributed in the edible portion of the grain. Essential elements were generally higher in the traditional rice varieties than those reported for non-traditional varieties and are a potential source of trace elements for nutrient-deficient communities. The concentration of selenium, an element that plays a protective role in the kidneys, was too low to provide the minimum recommended intake. The methods developed in this study could be applied to a more comprehensive study of elemental uptake of rice under controlled growing conditions.

Air nanobubble water improves plant uptake and tolerance toward cadmium in phytoremediation

Heavy metal contamination continues to be a persistent environmental problem. To address this issue, this study evaluated the impact of air nanobubbles (NBs) in water on the uptake of heavy metals by Alternanthera philoxeroides (A. philoxeroides), a common aquatic plant in China known for its rapid growth, strong vitality, and high capacity for heavy metal remediation. This study found that diluted air NBs (25% concentration) boosted cadmium uptake of A. philoxeroides by 17.39%. They also enhanced plant growth (25–50%) and photosynthetic pigments (10–20%) even at low cadmium levels (0.1 mM). Furthermore, the incorporation of 25% air NBs has been demonstrated to significantly amplify the performance of key antioxidant enzymes, such as superoxide dismutase and catalase, alongside heightened levels of crucial antioxidants such as malondialdehyde. This heightened activity of antioxidant defenses offers a compelling explanation for the potential amelioration of cadmium toxicity and concurrent enhancements in overall plant growth rates. Notably, a comprehensive analysis utilizing the excitation emission matrix–parallel factor analysis (EEM-PARAFAC) technique has revealed alterations in the composition of rhizosphere dissolved organic matter due to the presence of NBs. This ncomposition change of the rhizosphere dissolved organic mattermposition has subsequently exerted an influence on plant complexation processes and the subsequent uptake of cadmium. This study demonstrates that the strategic implementation of air NBs in water systems holds the potential to significantly enhance the plant's ability to detoxify cadmium and improve the uptake of heavy metals during phytoremediation processes.

Effect of Humic Acid Functionalized Bentonite on Heavy Metal Uptake by Spinach (Spinacia oleracea cv. All Green) Grown on Metal Contaminated Soil

A pot culture study was conducted to investigate the impact of applying humic acid functionalized bentonite (HA-B) on the uptake of heavy metals by spinach. When the soil was amended with 7.5 g kg-1 of humic acid intercalated bentonite, there was a significant improvement in plant growth. Specifically, plant growth increased by 180.7%, 212%, and 231% during the first, second, and third cuttings, respectively. Additionally, the concentration of metals in the spinach decreased substantially, with reductions of 62.8, 69.7, and 77.7% for Cd and 34.7%, 45.2%, and 64.7% for Ni during the first, second, and third cuttings, respectively, when 7.5 g kg-1 of humic acid functionalized bentonite was applied. Furthermore, the addition of humic acid intercalated bentonite at a rate of 7.5 g kg-1 to the soil significantly lowered the bioconcentration factor (BCF) of metals. The BCF decreased by 36.3%, 40%, and 55.2% for Cd and 15.2%, 13%, and 34.7% for Ni during the first, second, and third cuttings, respectively, indicating a reduced uptake of these metals by the plants. Moreover, the non-cancer health risk through hazard quotient (HQ) computation showed that the risk was significantly reduced due to consumption of spinach by the application of 7.5 g kg-1 of humic acid intercalated bentonite.

Biochar supported metallo-inorganic nanocomposite: A green approach for decontamination of heavy metals from water.

Heavy metal contamination of water has become a global environmental burden, which has stirred up agitation worldwide. Fabrication of adsorbents utilizing either low cost, environment friendly materials or waste products can be helpful in remediating environmental pollution. The current study evolved around the synthesis of nanocomposites derived from such raw precursors like spent tea waste biochar, hydroxyapatite, and clays. In this context, two nanocomposites, namely manganese ferrite doped hydroxyapatite/kaolinite/biochar (TK-NC) and manganese ferrite doped hydroxyapatite/vermiculite/biochar (TV-NC), were synthesized followed by their employment for decontamination of heavy metals from aqueous media. TK-NC and TV-NC exhibited the crystallite sizes in the range of 2.55-5.94 nm as obtained by Debye Scherrer Equation and Williamsons-Hall equation The fabricated nanocomposites were characterized using FT-IR, SEM-EDX, and powder XRD. Batch adsorption studies were performed, and influence of different adsorption parameters (contact time, reaction temperature, solution pH, adsorbent dose, and initial adsorbate concentration) on metal adsorption was examined. Thermodynamic studies revealed that the adsorption of Cr(VI), Ni(II) and Cu(II) on TK-NC and TV-NC was endothermic (+ΔH°) and indicates disorderness (+ΔS°) at the solid-liquid interface owing to the strong affinity of metal ions with adsorbent. The heavy metal uptake selectivity followed the following decreasing order; Cr(VI) > Cu(II) > Ni(II) by both nanocomposites, with adsorption capacities falling in the range of 204.68-343.05 mg g-1. Several adsorption kinetic and isotherm models were applied to experimentally calculated data, which suggest favorable adsorption of Cr(VI), Ni(II) and Cu(II) by TK-NC and TV-NC from the system while obeying general-order kinetics and R-P adsorption model, conferring the transition in adsorption kinetics order and involvement of multiple adsorption process.

Biosolids application enhances the growth of Aloe vera plants and provides a sustainable practice for nutrient recirculation in agricultural soils.

In the present study, the fertilization potential of biosolids (sewage sludge; SS) for the cultivation of Aloe vera plants was investigated using block design. Pot experiments were conducted in this study using 50, 100, 150, and 200g/kg of SS. Results showed that SS-fertilized soils significantly (p < 0.05) affected the proximate, biochemical, and heavy metal parameters of A. vera plants. In particular, the T4 treatment gave the best results with maximum plant height 62.21 ± 0.10cm, number of leaves per plant 18.00 ± 4.00, shoot-to-root ratio 6:1, fresh weight 1972.10 ± 0.07g per plant, dry weight 175.49 ± 0.15g per plant, total chlorophyll content (TCC) 0.41 ± 0.02mg/g fwt., carotenoids 0.25 ± 0.04mg/g, total flavonoids 7.55 ± 0.05mg/g, total tannins 3.87 ± 0.06µg/g, ascorbic acid 532.14 ± 0.10µg/g, superoxide dismutase (SOD) 46.28 ± 0.19µg/g, catalase (CAT) 119.23 ± 0.17µg/g, salicylic acid 3.05 ± 0.12mg/ml and anthraquinones 0.45 ± 0.04mg/ml, respectively. The proximate plant characteristics were 96.25 ± 2.71% moisture content, crude protein 0.93 ± 0.05%, crude fiber 5.78 ± 0.44%, crude lipid 3.25 ± 0.02%, lignin 10.74 ± 0.30%, cellulose 13.56 ± 1.06%, hemicellulose 7.24 ± 0.14%, ash 8.75 ± 0.03%, and carbohydrate contents 52.18 ± 1.10% in comparison with control treatment. The bioaccumulation factor showed that heavy metal accumulation was in the order of Cd < Ni < Cu < Pb < Cr < Zn < Fe. The prediction models developed on the basis of soil properties showed good fitness results for the prediction of heavy metal uptake by A. vera plants. The study presented a sustainable approach for managing SS in an eco-friendly way while producing good-quality A. vera plants.

Phytoremediation Effect and Soil Microbial Community Characteristics of Jiulong Iron Tailings Area, Jiangxi

The aim of this paper was to explore the remediation effect and mechanism of Wetland pine (Pinus elliottii), Chinese fir (Cunninghamia lanceolata (Lamb.) Hook), and Alder (Alnus cremastogyne Burkill) on heavy metal contaminated soil in the iron tailings of Jiulong Iron Tailings Area. At the same time, the specificity of plant rhizosphere and non-rhizosphere soil microbial community structure and ecological function were analyzed based on macrogenomic sequencing. The results showed that the dominant microbial genera in J1 (control) was Acidobacteria, followed by Proteobacteria and Actinobacteria. The microbial genera with the highest percentage of relative abundance in J2, J3, J4, J5, and J6 (J2, Wetland Pine rhizosphere; J3, Wetland Pine non-rhizosphere; J4, Chinese fir rhizosphere; J5, Alder rhizosphere; J6, Alder non-rhizosphere) were Proteobacteria, followed by Acidobacteria, and Actinobacteria. It was found that Proteobacteria promoted heavy metal solubilization, activated heavy metals, and converted their forms to improve plant uptake of heavy metals. This proves that the microorganisms of Proteobacteria are the key microbial genera in the study of regional heavy metal remediation. The antibiotic resistance genes (ARGs) in microorganisms can respond to the inducement of heavy metals. Here, we investigated the relationship between the abundance of soil microorganisms ARGs and heavy metal pollution in Jiulong Iron Tailings Area. There are significant differences in the quantity and category of ARGs in the rhizosphere and non-rhizosphere soil samples of the three tree species. The results of this study provide the foundation for the theory and practice of remediation of heavy metal contamination in soils of iron tailing areas in Jiulong Iron Tailings Area in similar stand conditions.

Bamboo Plantations for Phytoremediation of Cadmium in Tannery Effluent: Plant Response and Nutrient Uptake

The rapid development of the industrial sector led to a greater level of heavy metal Cadmium in recent years. Food and breathing are the primary waysthat Cadmium enters the body. Humans are exposed to long-term health hazards from Cadmium. Cadmium accumulates in immune cells, triggers inflammatoryresponses, and leads to a number of health problems. Compared to conventional physical and chemical techniques, phytoremediation is a useful, environmentallyadvantageous method of remediating contaminated soil. Among the different approaches available for phytoremediation, Phytoextraction is the most effective andsuccessful method since it gets rid of heavy metals. Some bamboo species have been recognized as the most promising species for sequestering carbon andpotentially impacting the phytoremediation of soils contaminated with heavy metals. This study aims to assess the growth patterns of the native Indian bamboospecies (Bambusa bambos, Bambusa vulgaris, and Bambusa balcooa) when exposed to metal-contaminated water, such as tannery effluent, in the Tiruchirappalli area.The ability of bamboo sp. to phytoextract Cadmium from contaminated soil has been demonstrated through experimentation, and its antimicrobial and anti-cancerpotency is tested after being subjected to phytoextraction since the heavy metals in the tannery effluent are predominantly carcinogenic. The laboratory conducteda preliminary study on bamboo plant growth to gauge its growth. To measure the tolerance of bamboo when being rinsed with a solution containing 100 mg Cd/l,the morphological characteristics, heavy metal uptake, and translocation potential of the three bamboo species were assessed. The distribution of Cadmium indifferent fragments of the bamboo plant has also been studied, along with the factors that affect the uptake mechanism. Among the native species, Bambusa bambosis found to have a greater phytoextraction capacity of heavy metals, especially Cadmium. The plant is also evaluated for its anticancer and antimicrobial activitiesfollowing phytoextraction so that the stem and other parts of Bambusa bambos have been used as indigenous medicine by the tribal people, and this could be due tothe presence of flavonoids and other associated compounds present in it.

Mercapto-based palygorskite modified soil micro-biology and reduced the uptake of heavy metals by Salvia miltiorrhiza in cadmium and lead co-contaminated soil

Salvia miltiorrhiza is an important traditional Chinese medicinal and edible plant that can easily accumulate excessive cadmium (Cd) and lead (Pb) from contaminated soils. The soil contaminated with heavy metals severely threatened the quality of S. miltiorrhiza products. In this study, we investigated the effects of mercapto-based palygorskite (MPAL), a new passivation amendment, on restraining the uptake of Cd and Pb by S. miltiorrhiza, and the impact on soil micro-ecology. Results showed that the application of MPAL prominently enhanced the biomass and antioxidant enzyme activities of S. miltiorrhiza. With the treatment of 4% MPAL, the Cd and Pb contents in the roots were significantly decreased by 81.42% and 69.09%, respectively. The active ingredients of S. miltiorrhiza, including Danshensu, Cryptotanshinone, Tanshinone I and Tanshinone II were remarkedly increased by 1899.46%, 5838.64%, 54.23% and 200.78%, respectively. In addition, MPAL decreased the bio-availability of Cd and Pb by speciation transformation, which simultaneously boosted the activities of cellulase and sucrase. The application of MPAL also improved the bacterial community composition. These findings revealed that the application of MPAL regulated the soil micro-ecology, positively modified the growth and obstructed the Cd and Pb accumulation in S. miltiorrhiza.

Effect of Manure and Glomus hoi on Heavy Metals and Soil Properties of Spent Engine Oil Contaminated Soil

This study aimed to assesses the impact of spent engine oil on selected soil properties including the heavy metal uptake before and after application of manure. The field experiments were carried in the early cropping season (April – July) and in the late cropping season (September – December) of year 2020 at the Obafemi Awolowo University Teaching and Research Farm, Ile-Ife. Spent-engine oil (SEO) was sourced from a mechanic workshop in Osogbo, Osun State. Amendments (poultry droppings, cow dung and leaves of Gliricidia sepium) were collected from OAU Teaching and Research Farm, Ile-Ife. Glomus hoi was also collected from around the region, and the spores were isolated through wet sieving methods. The test crop used was maize (variety is AWR- SYN- Y. A land area of 69 m x 17 m was ploughed and harrowed and arranged in an 8 X 6 alpha lattice design, containing sixteen (16) treatments with three concentrations which resulted in a total of forty-eight (48) plots in each replicate, each plot measured 2 m X 2 m with a spacing of 1 m in between the plots. The plots were impacted with Spent-engine oil (SEO) sourced from petrol engines. The oil was applied in concentration of 0 ml (0 L/ha), 400 ml (1000 L/ha) and 800 ml (2000 L/ha) to the plots. The treatments were applied to plots 7 days after Spent-engine oil (SEO) application. The layout of the experiment is as follows: Treatment 1 (T1) - Spent-engine oil only; Treatment 2 (T2) - Spent-engine oil + Cow dung; Treatment 3 (T3) - Spent-engine oil + Poultry Manure; Treatment 4 (T4) - Spent-engine oil + Glomus hoi; Treatment 5 (T5) - Spent-engine oil + Gliricidia Sepium leaves; Treatment 6 (T6) - Spent-engine oil + Cow dung + Poultry Manure; Treatment 7 (T7) - Spent-engine oil + Glomus hoi + Gliricidia sepium leaves; Treatment 8 (T8) - Spent-engine oil + Cow dung + Poultry Manure + Glomus hoi + Gliricidia sepium leaves. After treatments application, the plots were left for two weeks before planting to allow for incubation. Data collected were analyzed using appropriate statistical techniques. At the end of the experiment, all soils were impacted with the presence of increased Spent-engine oil with an increase in heavy metals in the soil. The findings suggest that a combination of different organic amendments can significantly reduce the heavy metal uptake of soils contaminated with spent-engine oil. However, further studies are needed to investigate the long-term effects of these treatments on soil quality and plant growth.

Effect of citric acid on phytoextraction potential of Cucurbita pepo, Lagenaria siceraria, and Raphanus sativus plants exposed to multi-metal stress

Phytoextraction is a novel technique that involves using plants to remove heavy metals from contaminated soils. An outdoor pot experiment was designed to evaluate the phytoextraction potential of three plant species Cucurbita pepo, Lagenaria siceraria, and Raphanus sativus in soil contaminated with multiple metals (Cd, Co, Cr, Cu, Ni, Pb, and Zn) under the application of citric acid. The results showed that Raphanus sativus, out of all the studied plants, had the highest root and shoot dry weight and the capacity to accumulate all heavy metals at higher concentrations except for Cu. The application of citric acid into the polluted soil significantly increased plant growth, biomass, and heavy metal uptake. High bioconcentration values indicate that Raphanus sativus is a promising plant for absorbing and accumulating Cd and Ni from the soil. The maximum values of bioconcentration were also observed by the application of citric acid. The values of metal translocation from the root to the shoot were varied by plant species and the citric acid application. Regarding the biomass, metal content, as well as removal metal percentage values, it became apparent that the Raphanus sativus plant was the most effective crop in removing heavy metals from multi-metal contaminated Soil. Generally, these findings emphasize that the application of citric acid could be a useful approach to assist Cd and Ni phytoextraction by Raphanus sativus plants. When these plants are growing as vegetable crops, more attention should be given to evaluating the heavy metal content in them, especially when adding citric acid to their soil through fertigation systems to avoid food chain contamination.

Effect of different levels of EDTA on phytoextraction of heavy metal and growth of Brassica juncea L.

Heavy metal pollution of soil is a major concern due to its non-biodegradable nature, bioaccumulation, and persistence in the environment. To explore the probable function of EDTA in ameliorating heavy metal toxicity and achieve the sustainable development goal (SDG), Brassica juncea L. seedlings were treated with different concentrations of EDTA (0, 1.0, 2.0, 3.0, and 4.0 mM Kg-1) in heavy metal-polluted soil. Plant samples were collected 60 days after sowing; photosynthetic pigments, H2O2, monoaldehyde (MDA), antioxidant enzymes, and ascorbic acid content, as well as plant biomass, were estimated in plants. Soil and plant samples were also examined for the concentrations of Cd, Cr, Pb, and Hg. Moreover, values of the phytoremediation factor were utilized to assess the accumulation capacity of heavy metals by B. juncea under EDTA treatments. In the absence of EDTA, B. juncea seedlings accrued heavy metals in their roots and shoots in a concentration-dependent manner. However, the highest biomass of plants (roots and shoots) was recorded with the application of 2 mM kg-1 EDTA. Moreover, high levels (above 3 mM kg-1) of EDTA concentration have reduced the biomass of plants (roots and shoots), photosynthetic area, and chlorophyll content. The effect of EDTA levels on photosynthetic pigments (chlorophyll a and b) revealed that with an increment in EDTA concentration, accumulation of heavy metals was also increased in the plant, subsequently decreasing the chlorophyll a and b concentration in the plant. TLF was found to be in the order Pb> Hg> Zn> and >Ni, while TF was found to be in the order Hg>Zn>Ni>Pb, and the best dose was 3 mM kg-1 EDTA for Hg and 4 mM kg-1 for Pb, Ni, and Zn. Furthermore, hyperaccumulation of heavy metals enhanced the generation of hydrogen peroxide (H2O2), superoxide anions (O2•-), and lipid peroxidation. It also interrupts mechanisms of the antioxidant defense system. Furthermore, heavy metal stress reduced plant growth, biomass, and chlorophyll (chl) content. These findings suggest that the exogenous addition of EDTA to the heavy metal-treated seedlings increases the bioavailability of heavy metals for phytoextraction and decreases heavy metal-induced oxidative injuries by restricting heavy metal uptake and components of their antioxidant defense systems.