Phytoextraction Of Heavy Metals Research Articles

Effects of nitrogen regulation on heavy metal phytoextraction efficiency (Leucaena leucocephala): application of a nitrogen fertilizer and a fungal agent

Lead (Pb) and cadmium (Cd) have been identified as the primary contaminants in soil, posing potential health threats. This study aimed to examine the effects of applying a nitrogen fertilizer and a fungal agent Trichoderma harzianum J2 (nitrogen alone, fungi alone, and combined use) on the phytoremediation of soils co-contaminated with Pb and Cd. The growth of Leucaena leucocephala was monitored in the seedling, differentiation, and maturity stages to fully comprehend the remediation mechanisms. In the maturity stage, the biomass of L. leucocephala significantly increased by 18% and 29% under nitrogen-alone (NCK+) and fungal agent-alone treatments (J2), respectively, compared with the control in contaminated soil (CK+). The remediation factors of Pb and Cd with NCK+ treatment significantly increased by 50% and 125%, respectively, while those with J2 treatment increased by 73% and 145%, respectively. The partial least squares path model suggested that the nitrogen-related soil properties were prominent factors affecting phytoextraction compared with biotic factors (microbial diversity and plant growth). This model explained 2.56 of the variation in Cd concentration under J2 treatment, and 2.97 and 2.82 of the variation in Pb concentration under NCK+ and J2 treatments, respectively. The redundancy analysis showed that the samples under NCK+ and J2 treatments were clustered similarly in all growth stages. Also, Chytridiomycota, Mucoromucota, and Ciliophora were the key bioindicators for coping with heavy metals. Overall, a similar remediation mechanism allowed T. harzianum J2 to replace the nitrogen fertilizer to avoid secondary pollution. In addition, their combined use further increased the remediation efficiency.

Phytoremediation Potential of Different Genotypes of Salix alba and S. viminalis.

Elevated concentrations of heavy metals result in soil degradation, a reduction in plant yields, and a lower quality of agricultural products, which directly endangers people, animals, and the ecosystem. The potential of three clones of Salix alba (347, NS 73/6, and B-44) and one genotype of S. viminalis for the phytoextraction of heavy metals was investigated, with the aim of identifying the most physiologically suitable willow genotypes for use in soil phytoremediation. The experiment was placed on the contaminated soil substrate collected in Kolubara Mining Basin (Serbia), enriched by high loads of heavy metal salts, and a control medium. Significant differences in the concentrations of heavy metals were recorded between the contaminated and control plant material, especially when it comes to nickel (Ni), copper (Cu), cadmium (Cd), and lead (Pb), confirming that S. alba and S. viminalis are hyperaccumulator species of heavy metals. Clone 347 shows the greatest uptake of Cd and chromium (Cr), and clone B-44 takes up these metals only to a lesser extent, while clone NS 73/6 shows a less pronounced uptake of Cr. The roots have the greatest ability to accumulate Ni and Pb, Cu is absorbed by all plant organs, while Cd is absorbed by the leaves. The organ that showed the greatest ability to accumulate heavy metals was the root, which means that willows have a limited power to translocate heavy metals to above-ground organs. The studied genotypes of S. alba have a higher potential for the phytostabilization of Cu and Cd, as well as the phytoextraction of Cd, compared with S. viminalis. The results confirm the assumption of differences between different willow genotypes in terms of the ability to phytoextract certain heavy metals from soil, which is important information when selecting genotypes for soil phytoremediation.

Screening of mustard cultivars for phytoremediation of heavy metals contamination in wastewater irrigated soil systems.

The mustard (Brassica juncea L.) plant is a well-known and widely accepted hyper-accumulator of heavy metals. The genetic makeup of mustard's cultivars may significantly impact their phytoremediation capabilities. The present study aimed to investigate the growth performance, yield attributes, and heavy metal accumulation potential of B. juncea cv. Varuna, NRCHB 101, RH 749, Giriraj, and Kranti, cultivated in soil irrigated with wastewater (EPS) and bore-well water (MPS). EPS contributed more Cr, Cd, Cu, Zn, and Ni to tested mustard cultivars than the MPS. EPS reduced morphological, biochemical, physiological, and yield attributes of tested mustard cultivars significantly (p < 0.05) than the MPS. Among the tested cultivars of mustard plants, Varuna had the highest heavy metal load with the lowest harvest index (35.8 and 0.21, respectively). Whereas NRCHB 101 showed the lowest heavy metal load with the highest harvest index (26.9 and 0.43, respectively). The present study suggests that B. juncea cv. Varuna and NRCHB 101 could be used for the phytoextraction of heavy metals and reducing their contamination in food chain, respectively in wastewater irrigated areas of peri-urban India. The outcomes of the present study can also be utilized to develop a management strategy for sustainable agriculture in heavy metal polluted areas resulting from long-term wastewater irrigation.

Evaluating capability of two halophyte plants for phytoextraction of cadmium from contaminated soils

Selecting an appropriate plant is a key factor for the phytoextraction of heavy metals from contaminated soils. The possibility of using two halophytes for the remediation of cadmium (Cd) from contaminated soils was investigated. Consequently, an experiment with Chenopodium album L. and Chenopodium botrys L. including Cd treatments of 0, 5,10, 20, 40, 60, 80 and 100 ppm was conducted. Designated analyses including fresh weight, dry weight, and Cd concentrations in shoots and roots were performed. Results indicated that for both plants, a logarithmic model performed best to demonstrate the relationship between total soil Cd with shoot Cd and dry matter. Although both halophytes had considerable capability to remediate Cd from soils, C. botrys demonstrated greater potential to accumulate Cd in shoots. The range of bioconcentration factor (BCF) in C. botrys was obtained to be 0.8 to 8.8 and in C. album was 0.4 to 1.73. For C album, BCF in most treatments was lower than 1.0, but for C. botrys, it was mostly larger than 1.0. Although both plants can be used as hyperaccumulators to remediate Cd-polluted soils, the clean-up time of C. album under higher Cd concentrations was shorter than C. botrys L.

Foliar application of plant growth regulators for enhancing heavy metal phytoextraction efficiency by Sedum alfredii Hance in contaminated soils: Lab to field experiments

The phytoremediation efficiency of plants in removing the heavy metals (HMs) might be influenced by their growth status and accumulation capacity of plants. Herein, we conducted a lab-scale experiment and a field try out to assess the optimal plant growth regulators (PGRs) including indole-3-acetic acid (IAA)/brassinolide (BR)/abscisic acid (ABA) in improving the phytoextraction potential of Sedum alfredii Hance (S. alfredii). The results of pot experiment revealed that application of IAA at 0.2 mg/L, BR at 0.4 mg/L, and ABA at 0.2 mg/L demonstrated notable potential as optimal dosage for Cd/Pb/Zn phytoextraction in S. alfredii. The findings of subcellular level of Cd/Pb/Zn in leaves showed that IAA (0.2 mg/L), BR (0.4 mg/L) or ABA (0.2 mg/L) promoted the HMs storage in the soluble and cell wall fraction, therefore contributing HMs subcellular compartmentation. In addition, application of PGRs notably enhanced the antioxidant system (SOD, CAT, POD, APX activities) while reducing lipid peroxidation (MDA content) in S. alfredii, consequently improving HMs tolerance and growth of S. alfredii. Moreover, the results of field trial showed that application of BR, IAA, or ABA+BR substantially improved the growth of S. alfredii by inducing plants biomass and augmenting the levels of photosynthetic pigment contents. Notably, ABA+BR noticed the highest theoretical biomass by 42.9 %, followed by IAA (41.6 %), and BR (36.4 %), as compared with CK. Additionally, ABA+BR treatment showed effectiveness in removing the Cd by 103.4 %, while BR and IAA led to a significant increase of Pb and Zn removal by 239 % and 116 %, respectively, when compared with CK. Overall, the results of this study highlights that the foliar application of IAA, BR, or ABA+BR can serve as viable strategy to boosting phytoremediation efficiency of S. alfredii in contaminated soil by improving the biomass and metal accumulation in harvestable parts.

Chelate facilitated phytoextraction of Pb, Cd, and Zn from a lead–zinc mine contaminated soil by three accumulator plants

This study aims to evaluate the enhancement of phytoextraction of heavy metals (Pb, Cd, and Zn) by species Marrubium cuneatum, Stipa arabica, and Verbascum speciosum, through EDTA amendment. Assisted phytoextraction pot experiments were performed at different EDTA dosages (0, 1, 3, and 5 mmol kg−1 soil). The DTPA-extractable metal content increased in the presence of EDTA, followed by their contents in the tissues of all three studied species. Resulting from oxidative stress, the activity of antioxidant enzymes such as glutathione peroxidase (GPX), superoxide dismutase (SOD), and catalase (CAT) increased when the chelating agent was added. EDTA in higher doses partially decreased chlorophyll concentration, and 5 mmol kg−1 of that reduced the biomass of the studied species. The bioconcentration factor (BCF) for Cd was notably high in all studied plants and considerably elevated for Zn and Pb with the addition of EDTA in M. cuneatum and S. arabica (BCF > 1), whilst an accumulation factor greater than one (AF > 1) was found for Cd in all species and for Pb in the case of S. arabica. In general, the results demonstrated that EDTA can be an effective amendment for phytoextraction of Cd, Zn, and Pb by M. cuneatum, V. speciosum and S. arabica in contaminated soils.

Critical evaluation of the performance of rhamnolipids as surfactants for (phyto)extraction of Cd, Cu, Fe, Pb and Zn from copper smelter-affected soil

Rhamnolipids are biosurfactants produced by bacteria belonging to the Pseudomonas genus. They are discussed to complex heavy metal cations stronger than cations of Fe, Ca, Mg. It is therefore suggested to employ rhamnolipids in phytoextraction where their addition to soil should result in preferential complexation of heavy metals that can be taken up by plants, thus enabling rapid and ecological clean-up of contaminated soil. In order to test this concept, we evaluated the rhamnolipid-mediated phytoextraction of heavy metal from soil collected from the vicinity of a copper smelter. The following aspects were investigated: i) selectivity of rhamnolipids towards Cu, Zn, Pb, Cd and Fe during soil washing; ii) phytoextraction efficiency of each ion with respect to the effective concentration of rhamnolipids; iii) possible phytotoxic effects; iv) effect of micro-sized polystyrene amendment. The experiments evaluated soil washing efficiency, BCR (Community Bureau of Reference) sequential extraction to determine the impact of rhamnolipids on the mobility of metal ions, phytoextraction with maize (Zea mays L.) and phytotoxic effects based on dry matter, chlorophyll fluorescence and content. The obtained results indicated that rhamnolipids lack desired selectivity towards heavy metal ions as Fe was complexed more efficiently by 80 % of the available rhamnolipids compared to priority pollutants like Zn, Cu, Pb, which were complexed by only 20 % of the tested rhamnolipids. With increased concentration of rhamnolipids, the soil washing efficiency increased and shifted in favour of Fe, reaching values of approx. 469 mg for Fe and only 118 mg in total of all tested heavy metals. Phytoextraction also favoured the accumulation of Fe, while Cd was not removed from the soil even at the highest applied rhamnolipid concentrations. Considering the selectivity of rhamnolipids and the costs associated with their production, our results suggest the need to search for other alternative (bio)surfactants with better selectivity and lower price.

Oxalic acid-assisted phytoextraction of heavy metal contaminated wastewater through Lemna minor L.

The present research was carried out to investigate the performance of oxalic acid (OA) through Lemna minor L. (duckweed) in the phytoextraction of lead (Pb) from metal contaminated water. Zero, 100 μM, 250 μM, and 500 μM Pb concentration and combinations with 2.5 ml of OA were provided to the plants in the form of solution after defining intervals. Continuous aeration was provided to the plants and kept a pH level at 6.5. Results from this research depicted that increasing concentration level of Pb inhibited the overall plant growth, biomass, frond area, chlorophyll, and antioxidant enzyme activities like peroxidase (POD), superoxide-dismutase (SOD), catalases (CAT), and ascorbate-peroxidase (APX). Moreover, Pb stress enhances the concentration, hydrogen peroxide, malondialdehyde, and electrolyte leakage substances in plants. Furthermore, the addition of OA alleviated the Pb-induced toxicity in the plants, increasing the Pb accumulation and its endorsement in the L. minor. The OA addition increased the Pb accumulation in plants at 0, 100, 250 and 500 μM. At higher concentration, Pb showed harmful effect as related to the other low doses. Under the application of OA, Pb higher accumulation and concentration in L. minor were measured, which showed that it could be the most suitable plant for the phytoextraction of lead-contaminated soil and wastewater.

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.

Exogenous ATP triggers antioxidant defense system and alleviates Cd toxicity in maize seedlings

The role of exogenous adenosine 5′-triphosphate (ATP) in the regulation of antioxidant response in plants under heavy metal stress is unclear. Here, we investigated the effects of exogenous ATP application on plant growth, antioxidant response, and Cd accumulation in maize seedlings. Treatment with 0.1 mM CdCl2 moderately reduced dry weight, decreased chlorophyll content, impaired photosynthesis, and increased lipid peroxidation in maize seedlings compared with controls. However, toxicity due to Cd was alleviated after 10–200 µM ATP treatment. Subsequently, the activity of Cd-regulated antioxidant enzymes, antioxidant metabolite accumulation, and total antioxidant capacity were drastically enhanced after 50 µM ATP treatment. Similar patterns were observed in the ADP-treated group but not in the AMP-treated group under Cd stress. However, the ATP-induced elevation in antioxidant defense ability was decreased by the inhibition of NADPH oxidase (NOX). ATP-induced elevation in NOX activity and H2O2 production was partly reversed by the inhibition of NOX in maize seedlings under Cd stress. Furthermore, ATP promoted Cd accumulation in the roots and shoots of maize seedlings. However, the ATP-induced increase in Cd accumulation was partly abolished by the inhibition of NOX. To our knowledge, this is the first report on the role and mechanism of exogenous ATP in regulating plant growth, antioxidant response, and heavy metal phytoextraction. The study provides a new method based on exogenous ATP for enhancing heavy metal tolerance in plants.

A Review Article: Pharmacological uses and Phytochemistry Studies on Carica papaya

For a very long time, the papaya has been valued for both its nutritionals, and therapeutic activity. The various traditional medical systems, including Ayurveda, are well aware of the therapeutic benefits of papaya fruit and other parts. Its many portions have been described in numerous traditional literatures for various disease situations, including cold, fever, headache, swellings, gonorrhoea, itches, jaundice, eczema, asthma, chicken pox, bronchitis and whooping cough. Over the past forty years, numerous outstanding studies on biological functions and therapeutic uses have been documented, establishing it as a significant nutraceutical agent. Scientific research has been done on the Carica papaya Linn. leaf for a number of therapeutic purposes, including antibacterial, antioxidant, antipyretic, insecticidal, antimicrobial, and anti-mollusk properties. Given this, Leaves have been investigated using variation of cutting-edge approach, as well as phytoextraction of heavy metals and phytoremediation of particle pollution. The past severals decade, A numbers of read up on phytoconstituents and the chemical make-up of leaves have been published. The presents-day review seeks to allow a overviews of Carica papaya Linn. pharmacognostic phytochemical and pharmacological studies.

PGPR: the treasure of multifarious beneficial microorganisms for nutrient mobilization, pest biocontrol and plant growth promotion in field crops.

Plant growth-promoting rhizobacteria (PGPR) have multifarious beneficial activities for plant growth promotion; act as source of metabolites, enzymes, nutrient mobilization, biological control of pests, induction of disease resistance vis-a-vis bioremediation potentials by phytoextraction and detoxification of heavy metals, pollutants and pesticides. Agrochemicals and synthetic pesticides are currently being utilized widely in all major field crops, thereby adversely affecting human and animal health, and posing serious threats to the environments. Beneficial microorganisms like PGPR could potentially substitute and supplement the toxic chemicals and pesticides with promising application in organic farming leading to sustainable agriculture practices and bioremediation of heavy metal contaminated sites. Among field crops limited bio-formulations have been prepared till now by utilization of PGPR strains having plant growth promotion, metabolites, enzymes, nutrient mobilization and biocontrol activities. The present review contributes comprehensive description of PGPR applications in field crops including commercial, oilseeds, leguminous and cereal crops to further extend the utilization of these potent groups of beneficial microorganisms so that even higher level of crop productivity and quality produce of field crops could be achieved. PGPR and bacteria based commercialized bio-formulations available worldwide for its application in the field crops have been compiled in this review which can be a substitute for the harmful synthetic chemicals. The current knowledge gap and potential target areas for future research have also been projected.

Spring wheat yield under application of growth promoting rhizobacterium in soil contaminated with nickel

Impact of growth promoting rhizobacterium Pseudomonas fluorescens 20 on the yield of spring wheat was studied in pot experiment. Plants were grown up to maturity when agrogray soil was contaminated with Ni as NiCl2·6H2O at a rate of 200 mg Ni/kg of soil against background of applying NPK fertilizers. After harvesting, content of nutrients N, P, K, Ca, Mg, Fe, Mn, Zn and Cu in grain, straw and roots was determined. N was determined by phenol technique. Resistance of plants to Ni toxicity was found under bacterial inoculation. Application of bacterium eliminated phytotoxicity of heavy metal and provided the same biomass production including grain as in control - in non-inoculated plants non-exposed Ni stress. Resistance of plants inoculated with bacterium to Ni toxicity was due to enhanced growth of root system and increase in content and accumulation of Ni in roots and, as a result this was not accompanied by increase in metal incorporation into aboveground organs. Resistance of plants inoculated with bacterium to Ni toxicity was due to enhanced growth of root system and increase in content and accumulation of Ni in roots. Application of bacterium also improved mineral nutrition of plants - increased nutrient uptake from contaminated soil. Increase in nutrient uptake by yield from contaminated soil as influenced by inoculation with bacterium was due to growth promotion and increase of plant weight in general without significant changes in content of most elements in aboveground organs and roots. Bacterium enhanced phytoextraction of heavy metal (soil cleaning) - increased Ni uptake by aboveground organs without significant changes in its content in grain and straw. Increase in Ni uptake by bacterially inoculated plants occurred without changes of soil medium reaction and was probably due to production of bacterial siderophores.

Comparative assessment of the heavy metal phytoextraction potential of vegetables from agricultural soils: A field experiment

A field study was established to determine the phytoextraction potential of six vegetable species, namely Amaranthus viridis L., Basella alba L., Brassica chinensis var. Parachinensis, Brassica rapa L., Capsicum frutescens L., and Ocimum tenuiflorum L.. These edible plants were selected for their short growth cycles and high biomass production, which are some traits for efficient phytoremediation. Following acid digestion of the soil and vegetable samples using the USEPA 3050B acid digestion method, the extracts were analyzed for Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn using ICP-OES. Results in soil samples showed that the concentrations of both beneficial and essential heavy metals, and non-essential heavy metals are below the WHO, USEPA, and CCME soil quality guidelines. Al is one of the highest concentrations found in the soil samples but it tends to accumulate in the root part of all vegetable species compared to the aboveground parts. In general, B. rapa L. accumulated the highest level of Cd (0.4 mg/kg) and Pb (5.71 mg/kg), while B. alba L. accumulated the highest Cr (2.62 mg/kg) in all plant parts. The findings in this study indicated that Co, Cu, Fe, Mn and Zn were mostly accumulated in leaves of A. viridis L. (Co, Cu, Fe, Mn and Zn), B. alba L. (Co, Fe and Mn), B. chinensis (Mn and Zn) and O. tenuiflorum L. (Mn), and roots of C. frutescens L. (Co, Cu, Fe and Mn), B. alba L. (Co, Cu and Zn), A. viridis L. and B. chinensis (Cu and Fe) and B. rapa L. (Fe). Cr, Pb and Ni were significantly greater in B. alba L. (Cr) And B. rapa L. (Ni and Pb) roots. MTF >1 was observed in the roots of all species for Co, Cd, Zn, and Ni. BTC values varied between the different vegetable species with A. viridis L. having the greatest heavy metal mobility between its plant parts and the best heavy metal phytoextraction potential among other species. The PCA biplots showed that heavy metals were partitioned differently between various plant parts of the vegetable species and can be explained by the first two components (PC1 and PC2) which were associated with the root and/or leaf parts for most vegetable species.

Survival and phyto-extraction of heavy metals by Nauclea diderrichii (De Wild. &amp; T. Durand) Merr. plantlets in spent engine oil medium

Investigation was carried out on the phyto-extraction potentials of Nauclea diderrichii grown in tissue culture medium contaminated with spent engine oil with a view to determining the suitability of this tree species to remediate polluted soils for reclamation. This experiment was carried out in the Biotechnology Research Center, Forestry Research Institute of Nigeria, Ibadan, Oyo State. The experimental design used for this study was Completely Randomized Design with 9 treatments replicated 5 times. Concentrations 0 (control), 0.1, 0.2, 0.3 0.4 ml of spent engine oil (SEO) from diesel and petrol engines were applied to the medium of the plantlets. The survival of the plantlets was monitored while amount of heavy metals (Lead and Cadmium) present in the plantlets were assessed after 2 months. Data collected were subjected to descriptive analysis. After 2 months, results showed that 100 % of the plantlets without the application of SEO (control) survived, 60% of the plantlets subjected to 0.1 ml of SEO from diesel engine (D) and 0.1 ml of SEO from petrol engine (P) survived. Forty percent (40 %) of the plantlets subjected to 0.2 ml SEO from D and 0.2 ml SEO from P survived, 20 % of the plantlets subjected to 0.3 ml SEO from D and 0.3 ml SEO from P survived while plantlets subjected to 0.4 ml SEO from D and 0.4 ml SEO from P did not survive. There was difference in the amount of lead and cadmium of N. diderrichii plantlets subjected to different SEO from diesel and petrol engines. The Pb and Cd content in the tissue of plantlets subjected to SEO from petrol engine was higher than that of plantlets subjected to SEO from diesel engine. This might be due to the viscousity of the different SEO. The study revealed that contamination of the culture medium with SEO from both diesel and petrol engines can lead to a gradual accumulation of heavy metals showing the phytoremediation potentials of N. diderrichii. This study has been able to show that tissue cultured plantlets of N. diderrichii have the ability/potential to phyto-extract heavy metals from SEO contaminated medium.

Acidified Cow Dung-Assisted Phytoextraction of Heavy Metals by Ryegrass from Contaminated Soil as an Eco-Efficient Technique

Heavy metal contamination of soil is an alarming environmental dilemma all over the world. With increasing industrialization, timely development of low-cost and eco-friendly remedial techniques for heavy metal-contaminated soil is needed. Phytoremediation is an emerging technique to remove heavy metals from contaminated soil for environmental sustainability. In the present study, ryegrass was used for phytoextraction of lead and cadmium from contaminated soil in a pot experiment. To enhance the bioavailability of heavy metals, cow dung was acidified by amending with elemental sulfur and molasses and also bioaugmented with an SS-16 sulfur-oxidizing strain to boost biological sulfur oxidation and, hence, four chemically different organic products were prepared. The pot experiment was conducted for a period of 60 days under Pb- and Cd-spiked soil for growing ryegrass with the application of a 10% slurry of each acidified organic product. A significant increase in root and shoot fresh mass as well as Pb and Cd accumulation in the root and shoot of the ryegrass was recorded. As compared to the control and the acidified organic product, P4 was the most effective product overall. Bioconcentration and translocation factors of ryegrass for Pb and Cd were also calculated. At the same time, acidified cow dung slurry (10%) also improved the antioxidative defense mechanism of ryegrass. The results suggest that acidified organic products could be effective for phytoextraction of lead and cadmium from contaminated soil, and in the future acidified cow dung slurry can be used to restore heavy metal-polluted soils in an environmentally sustainable way.

Remediation of soils on municipal rendering plant territories using Miscanthus × giganteus

Phytoremediation, as a cost-effective, highly efficient, environmentally friendly, and green approach, gained attention to the removal of metals, including heavy metals, from contaminated soils. The toxic nature of heavy metals can have an adverse effect on human health and the ecosystem, and their removal remains a worldwide problem. Therefore, in this study, a field experiment was carried out to evaluate the potential of Miscanthus × giganteus for the removal of ten microelements and heavy metals (Al, Zn, Fe, Pb, Cd, Co, Cr, Cu, Mn, Ni) from contaminated soil in the territory of a Municipal Waste Rendering Plant. Moreover, the effect of the incorporation of soil improver obtained upon composting biodegradable waste as well as the addition of highly contaminated post-industrial soil on the efficiency of phytoremediation and plant growth was described. The soil improver (SK-8) was applied to the soil at a rate of 200 Mg ha−1 and 400 Mg‧ha−1. Meanwhile, in the last object, 100 Mg‧ha−1 of highly contaminated post-industrial soil was added. Herein, the research was aimed at assessing the possibility of phytoextraction of heavy metals from soils with different physicochemical properties. The results showed that plants cultivated in soil with 400 Mg‧ha−1 of soil improver exhibited the highest yield (approximately 85% mass increase compared to the soil without additives). Furthermore, the application of a single dose of SK-8 (200 Mg ha−1) increased the uptake of Al, Fe, Co, Pb, Mn, Ni, and Cd by Miscanthus × giganteus compared to the soil without additives. Additionally, the performed biotests demonstrated no or low toxicity of the investigated soils affecting the test organisms. However, in all experiments, the phytorecovery of the elements did not exceed 1% of the amount introduced to the soil, which may result from a short cultivation period and large doses of SK-8 or highly contaminated post-industrial soil.

Phytoremediation of contaminated industrial wastewater by duckweed (Lemna minor L.): Growth and physiological response under acetic acid application.

Extensive usage of heavy metals (HMs) in chemical reactions and processes eventually contaminate the environmental segments and is currently a major environmental concern. HMs such as cadmium (Cd), copper (Cu), lead (Pb), chromium (Cr) and nickel (Ni) are considered the most harmful pollutants as they have adequate potential of bioaccumulation. The current research was carried out to assess the HMs toxicity of textile and tannery wastewater and effect of acetic acid (AA) on phytoextraction of HMs by duckweed (Lemna minor L.) in a hydroponic system. Plants were treated with different treatments having different hydroponic concentrations of AA (5 and 10mM) and textile and tannery effluents, where these two effuents were equally mixed and then diluted with good quality water with different ratios (25, 50, 75, and 100%) along with three replications of each treatment. Results were recorded for growth attributes, chlorophylls, antioxidant enzymes, electrolytic leakage, reactive oxygen species and HMs accumulation in plants. HMs accumulation disrupts the growth parameters, chlorophyll contents and carotenoids contents along with increased activities of antioxidant enzyme such as catalases (CAT), superoxide dismutase (SOD), peroxidases (POD) and ascorbate peroxidase (APX). Addition of AA in the hydroponic experimental system significantly improves the antioxidant defense mechanism and alleviated the HM induced toxicity in plants. Cr, Cd, Pb, Cu and Ni concentrations were maximally increased up to 116 & 422%, 106 & 416%, 72 & 351%, 76 & 346%, and 41 & 328% respectively under AA (10mM) application. The results revealed that duckweed can be applied as potential phyto-remedy to treat industrial wastewater.

Application of phytoremediation on soil polluted by heavy metals from sewage sludge

Soil pollution by heavy metals (HM) has become a problem in Algeria, in particular that caused by the discharge of untreated sewage sludge due to the lack of means at the level of sewage treatment plants (WWTP). The objective of our work was to study the possibility of reducing HM pollution of the soil of the WWTP site of Reghaia (Algeria) by phytoremediation. The results obtained showed the decrease in plant growth parameters (maize, rapeseed and alfalfa) grown on the polluted soil. However, on polluted soil amended with fertilizer, improved growth of these plants was noted. It has also been observed that the cultivation of plants in polluted soils (amended and unamended) made it possible to have attenuation rates for HMs (Cd, Zn and Cr) higher than those obtained in the absence of plant cultivation. However, these rates were not very high (less than 40%), and the fertilizer amendment did not increase these rates, despite the improvement in the production of plant biomass. This would be mainly due to the decrease in the bioavailability of HMs for plants. It was concluded that the tested plants do not allow the phytoextraction of HM but their phytostabilization in the polluted soil of the Reghaia WWTP site.

Modeling phytoremediation of heavy metal contaminated soils through machine learning

As an important subtopic within phytoremediation, hyperaccumulators have garnered significant attention due to their ability of super-enriching heavy metals. Identifying the factors that affecting phytoextraction efficiency has important application value in guiding the efficient remediation of heavy metal contaminated soil. However, it is challenging to identify the critical factors that affect the phytoextraction of heavy metals in soil–hyperaccumulator ecosystems because the current projections on phytoremediation extrapolations are rudimentary at best using simple linear models. Here, machine learning (ML) approaches were used to predict the important factors that affecting phytoextraction efficiency of hyperaccumulators. ML analysis was based on 173 data points with consideration of soil properties, experimental conditions, plant families, low-molecular-weight organic acids from plants, plant genes, and heavy metal properties. Heavy metal properties, especially the metal ion radius, were the most important factors that affect heavy metal accumulation in shoots, and the plant family was the most important factor that affect the bioconcentration factor, metal extraction ratio, and remediation time. Furthermore, the Crassulaceae family had the highest potential as hyperaccumulators for phytoremediation, which was related to the expression of genes encoding heavy metal transporting ATPase (HMA), Metallothioneins (MTL), and natural resistance associated macrophage protein (NRAMP), and also the secretion of malate and threonine. New insights into the effects of plant characteristics, experimental conditions, soil characteristics, and heavy metal properties on phytoextraction efficiency from ML model interpretation could guide the efficient phytoremediation by identifying the best hyperaccumulators and resolving its efficient remediation mechanisms.