Phytoremediation Of Soils Research Articles

Remote Sensing and Mycorrhizal-Assisted Phytoremediation for the Management of Mining Waste: Opportunities and Challenges to Raw Materials Supply

In recent times, the development of innovative processes permits the application of a circular economy approach to the management and exploitation of mining waste with respect to human health and environment, such that society is changing its fundamentally negative perception of the mining sector. This study presents the opportunities and challenges of supplying raw materials from waste using a remote sensing technique, mycorrhizal-assisted phytoremediation, and hydrometallurgical techniques to transform mining waste from a problem to a resource. Soil/mine wastes from the Sierra Pintada mine (Mendoza, Argentina) were mineralogically and chemically analyzed, and then, a mapping of the mining waste was carried out by Sentinel-2A images to identify areas with similar characteristics. The bioaccumulation of HMs by autochthonous shrubs was also determined to select accumulator plant species, and to evaluate their potential for phytoremediation of mine soils at different technological scales, when they were inoculated with arbuscular mycorrhizal fungi originated from a mining-impacted area. RMs were recovered from plant biomass by scaling in bioreactors, the depuration module, and hydrometallurgical techniques. The encouraging results highlight that this multidisciplinary approach can be applied to meet the increasing demand for RMs supply and, at the same time, to protect the environment and public health.

Enhancing phytoremediation of arsenic-contaminated soil by agronomic practices (drip irrigation and intercropping): Influence of soil organic matter

It is essential to improve the efficiency and economic benefits of phytoremediation. In this study, drip irrigation and intercropping were used to enhance the phytoremediation of arsenic-contaminated soil. Meanwhile, the influence of soil organic matter (SOM) on phytoremediation was investigated by comparing the difference in arsenic migration in soils with or without peat addition as well as the arsenic accumulation of plants. The results showed that hemispherical wetted bodies with a radius of approximately 6.5 cm were formed in the soil after drip irrigation. Arsenic in the center of the wetted bodies migrated to the edge of the wetted bodies. Peat inhibited the upward migration of arsenic from the deep subsoil and increased the phytoavailability of arsenic under drip irrigation conditions. To soils without peat added, drip irrigation decreased the arsenic accumulation in crops (planted at the center of the wetted body) while increased the arsenic accumulation in remediation plants (planted at the edge of the wetted body) compared with the flood irrigation treatment. An increase in soil organic matter of about 36 % was found after mixing 2 % peat in the soil, and correspondingly, arsenic concentrations in remediation plants increased by >28 % in both intercropping treatments with a drip or flood irrigation. Drip irrigation coupled with intercropping enhanced the effect of phytoremediation, and the addition of soil organic matter further improved phytoremediation efficiency.

Overexpression of LSU1 and LSU2 confers cadmium tolerance by manipulating sulfur metabolism in Arabidopsis

Phytoremediation using plants is an environmentally friendly and cost-effective strategy for removing cadmium (Cd) from soil. Plants used for phytoremediation must have a high Cd accumulation capacity and strong Cd tolerance. Therefore, understanding the molecular mechanism of Cd tolerance and accumulation in plants is of great interest. In response to Cd exposure, plants produce various thio-rich compounds, such as glutathione, phytochelatins, and metallothioneins, which play important roles in Cd immobilization, sequestration, and detoxification. Therefore, sulfur (S) metabolism is crucial for Cd tolerance and accumulation. In this study, we report that the overexpression of low-S responsive genes, LSU1 and LSU2, confers Cd tolerance in Arabidopsis. First, LSU1 and LSU2 promoted S assimilation under Cd stress. Second, LSU1 and LSU2 inhibited the biosynthesis and promoted the degradation of aliphatic glucosinolates, which could limit the consumption and enhance the release of S, thus, facilitating the production of the S-rich metabolites, glutathione, phytochelatins, and metallothioneins. We further demonstrated that the Cd tolerance mediated by LSU1 and LSU2 was dependent on the myrosinases BGLU28 and BGLU30, which catalyze the degradation of aliphatic glucosinolates. In addition, the overexpression of LSU1 and LSU2 improved Cd accumulation, which has great potential for the phytoremediation of Cd-contaminated soil.

Isolation and characterization of plant growth promoting bacteria (PGPB) from Larrea divaricata Cav., with potential use in phytoremediation of mining soils

Isolation and characterization of plant growth promoting bacteria (PGPB) from Larrea divaricata Cav., with potential use in phytoremediation of mining soils

Electrokinetic-Assisted Phytoremediation of Pb-Contaminated Soil: Influences of Periodic Polarity Reversal Direct Current Field

The effect of electric stimulation on the phytoremediation of Pb-contaminated soil by tall fescue and wheat seedlings was investigated by monitoring the time-dependent changes in soil properties and Pb accumulation in plants with or without a direct current (DC) exchange field. The results showed that plants could strengthen electrical conductivity (EC) and current in the soil environment. The periodic exchange electrode helped maintain a stable soil pH. Electric stimulation enhanced phytoremediation efficiency, and the enhancement effect increased with plant growth. Compared with the treatments without a DC exchange electric field, the Pb content in plots with tall fescue and wheat seedlings under DC exchange electric field increased 107–250.6% and 32.7–84.4%, respectively, after 30 d of planting. DC exchange electric field significantly increased the Pb enrichment coefficient of tall fescue and wheat seedlings. The upward transport of Pb from wheat seedling roots to shoots was greatly promoted by electric stimulation for 18 d. However, Pb transport in both plants was restrained after 18 d of electric stimulation. Additionally, DC exchange electric stimulation can improve the phytoremediation of heavy-metal-contaminated soil. More attention should be paid to the selection and testing of promising hyperaccumulators for electrokinetic-assisted phytoremediation of Pb-contaminated soil.

Transcriptomic analysis reveals the molecular mechanisms of Boehmeria nivea L. in response to antimonite and antimonate stresses

Soil antimony (Sb) pollution is a global concern that threatens food security and human health. Boehmeria nivea L. (ramie) is a promising phytoremediation plant exhibiting high tolerance and enrichment capacity for Sb. To reveal the molecular mechanisms and thus enhance the ramie uptake, transport, and detoxification of Sb with practical strategies, a hydroponic experiment was conducted to compare the physiological and transcriptomic responses of ramie towards antimonite (Sb(Ⅲ)) and antimonate (Sb(Ⅴ)). Phenotypic results showed that Sb(Ⅲ) had a stronger inhibitory effect on the growth of ramie. Root Sb content under Sb(Ⅲ) was 2.43 times higher than that in Sb(Ⅴ) treatment. Based on the ribonucleic acid sequencing (RNA-Seq) technique, 3915 and 999 significant differentially expressed genes (DEGs) were identified under Sb(Ⅲ) and Sb(Ⅴ), respectively. Transcriptomic analysis revealed that ramie showed different adaptation strategies to Sb(Ⅲ) and Sb(V). Key DEGs and their involved pathways such as catalytic activity, carbohydrate metabolisms, phenylpropanoid biosynthesis, and cell wall modification were identified to perform crucial roles in Sb tolerance and detoxification. Two heavy metal-associated domain-type genes, six heavy metal-associated isoprenylated plant proteins, and nine ABC transporters showed possible roles in the transport and detoxification of Sb. The significant upregulation of NRAMP5 and three NIPs suggested their roles in the transport of Sb(V). This study is the basis for future research to identify the exact genes and biological processes that can effectively enhance Sb accumulation or improve plant tolerance to Sb, thereby promoting the phytoremediation of Sb-polluted soils.

USING OF THE MATHEMATICAL PLANNING OF THE EXPERIMENT FOR THE QUANTITATIVE ASSESSMENT OF THE METHOD OF PHYTOREMEDIATION RESTORATION OF SOILS CONTAMINATED WITH PETROCHEMICALS

Nowadays, the problem of soil contamination with oil products has global character. The issue of soil quality is particularly acute in technogenically loaded territories, which, in particular, include the territories of airports. To reduce the negative impact of petrochemicals on the condition of the soils and to restore their quality characteristics, various methods of destruction of petroleum hydrocarbons in contaminated soils are used. In recent years, biological methods of cleaning soils from oil products are gaining more and more popularity. These methods have a number of advantages over physic-chemical and mechanical methods of restoring the quality of the soils contaminated with petrochemicals. However, the most popular is the phytoremediation method. In our research, we have chosen this method of cleaning soils contaminated with aviation fuel, as it is one of the most ecologically safe, cost-effective, accessible and promising of the existing methods of restoring the quality of soils contaminated with petroleum products. The purpose of the work was to evaluate the use of phytoremediation to restore the quality characteristics of soil contaminated with aviation fuel, using the method of mathematical planning of the experiment, namely the method of full factorial experiment, which allows obtaining a statistical model of the influence of the factors involved, namely the presence of plants and petroleum products. To achieve the goal, the phytoremediation technology of soil samples artificially contaminated with TS-1 aviation kerosene was applied. The plants chosen for the study were oats (Avena Sativa L.) and timothy (Phleum L.). The change in the level of phytotoxicity of the soil samples after the application of phytoremediation technology was determined using a growth test with watercress (Lepidium sativum).
 The obtained data showed that on the 10th day of observation, the negative impact of aviation fuel (X2) and the positive impact of plants (X1) is observed. At the same time, strengthening the positive impact of plant action and reducing the negative impact of aviation fuel in the interaction of these two factors X1 and X2. Analyzing the obtained results, we can draw a conclusion about the possibility of using the technology of phytoremediation of oil-contaminated soils, which is quantitatively evaluated using the method of a full factorial experiment.

Does micro/nano biochar always good to phytoremediation? A case study from multiple metals contaminated acidic soil using Salix jiangsuensis '172'

Biochar amendments have shown great superiority in reduction of heavy metals (HM) toxicity and soil amelioration in severely contaminated mining areas, which suggested to facilitate vegetation rehabilitation using fast-growing trees. Bone biochar (BC) and ball-milled bone biochar (MBC) were fabricated by pyrolyzing bone meal at 600°C followed by eco-friendly wet-milling techniques. The effect of BC and MBC application (0, 0.5, 1.0, 2.0 and 4.0 wt%) on soil properties, plant growth and metal accumulation of Salix jiangsuensis '172' (SJ-172) in multi-metal (Cu, Pb, Cd and Mn)-contaminated acid clay soil was investigated in a 150-day pot experiment. The results showed that BC and MBC considerably improved the survival rate of SJ-172 when the application rate was larger than 1.0%. MBC displayed outstanding performance in reducing HMs bioavailability and improving N and P soil fertility, while BC enhanced the reduction in acidity and increase in K supply. Interestingly, BC enhanced HMs accumulation (Cd 115.23%, Pb 161.82%, Mn 285.23% and 219.29% Cu at 4% application rate) by SJ-172 compared with MBC. Taken together, the good performance of BC in enhancing HMs accumulation in SJ-172 indicated that it is a promising amendment for phytoremediation of clay soils, while MBC can be utilized as an excellent amendment for HMs stabilization.Graphical

Co-planting alters plant iron deficiency in heavy metals contaminated soil amended with sludge

Heavy metals (HMs)-induced iron (Fe) deficiency severely inhibits plant growth and thus hampers phytoremediation and revegetation in HMs-contaminated soil. We conducted a 12-month pot experiment to investigate the effects and mechanisms of co-planting on altering plant HM-induced Fe deficiency. The landscape tree Ilex rotunda was co-planted with Ficus microcarpa and Talipariti tiliaceum in sludge-amended soil. The responses of I. rotunda growth, elements uptake, and rhizosphere microbial community and metabolites were analyzed. The addition of sludge increased cadmium (Cd), zinc (Zn), and nickel (Ni) uptake and induced Fe deficiency-induced chlorosis in I. rotunda. This chlorosis was exacerbated when I. rotunda was co-planted with F. macrocarpa due to the increase in the abundance of sulfate reduction or Fe immobilization-associated bacteria and the relative level of isoprenyl alcohol and atropine in I. rotunda rhizosphere but the decrease in the contents of soil diethylenetriaminepentaacetic acid Fe (DTPA-Fe) (−16.19 %). Co-planting with T. tiliaceum or F. macrocarpa and T. tiliaceum decreased the contents of total or DTPA Zn/Cd/Ni in the soil while increased the contents of soil DTPA-Fe by 13.24 % or 11.34 % and the abundance of microbes which contributed to immobilizing HMs or activating Fe reduction, and then alleviated the chlorosis and the growth inhibition of I. rotunda. These results provide a new perspective on the phytoremediation and revegetation of HMs-contaminated soil.

Ectomycorrhizal fungi, two species of Laccaria, differentially block the migration and accumulation of cadmium and copper in Pinus densiflora

The root tips of host plant species can establish ectomycorrhizae with their fungal partners, thereby altering the responses of the host plants to heavy metal (HM) toxicity. Here, two species of Laccaria, L. bicolor and L. japonica, were investigated in symbiosis with Pinus densiflora to study their potential for promotion of phytoremediation of HM-contaminated soils in pot experiments. The results showed that L. japonica had significantly higher dry biomass than L. bicolor in mycelia grown on modified Melin-Norkrans medium containing elevated levels of cadmium (Cd) or copper (Cu). Meanwhile, the accumulations of Cd or Cu in L. bicolor mycelia were much higher than that in L. japonica at the same level of Cd or Cu. Therefore, L. japonica displayed a stronger tolerance to HM toxicity than L. bicolor in situ. Compared with non-mycorrhizal P. densiflora seedlings, inoculation with two Laccaria species significantly increased the growth of P. densiflora seedlings in absence or presence of HM. The mantle of host roots blocked the uptake and migration of HM, which led to the decrease of Cd and Cu accumulation in the P. densiflora shoots and roots, except for the root Cd accumulation of L. bicolor-mycorrhizal plants when 25 mg kg−1 Cd exposure. Furthermore, HM distribution in mycelia showed Cd and Cu are mainly retained in the cell walls of mycelia. These results provide strong evidence that the two species of Laccaria in this system may have different strategies to assist host tree against HM toxicity.

Effects of Different Trace Elements on Ecophysiological Characteristics of Ligustrum obtusifolium Saplings

Phytoremediation is becoming more prevalent globally. Literature on phytoremediation strategies in western China is relatively scarce. The present research sought to fill this gap by examining the effects of trace elements such as Cd, Cr, Pb, and Zn on growth, physiological traits, tolerances, and accumulation characteristics in 2-year-old saplings of Ligustrum obtusifolium. The gradient of trace element concentration was determined by adding exogenous trace elements to the soil in a pot experiment: CK (no exogenous trace element), T1, T2, and T3 (Cd 0, 2, 5, and 10 mg/kg; Cr 0, 300, 500, and 700 mg/kg; Pb 0, 400, 800, and 1200 mg/kg; and Zn 0, 300, 500, and 1000 mg/kg, respectively). The results indicated that Chla, Chlb, and total Chls significantly decreased (p < 0.05) in the leaves of L. obtusifolium, with the lowest value obtained during soil treatment with T3. Along with the increase in trace element concentration, the net increase in height, root biomass, aerial biomass, and total biomass was reduced significantly. The net growth of L. obtusifolium under Cr stress did not differ significantly from that of CK at T1; however, the net growth of L. obtusifolium under Cr stress was considerably reduced at T2 and T3. The antioxidant enzyme activity of L. obtusifolium increased under different trace element stresses and first increased and then decreased as trace element levels increased. It was found that the SOD, POD, CAT, and APX activity of L. obtusifolium peaks at T2 under Cd and Zn stress in contrast to a peak at T1 under Cr and Pb stress. The contents of trace elements in L. obtusifolium roots, stems, and leaves increased along with the increase in soil trace element levels. Cr, Pb, and Zn threshold values can be set at 300 mg/kg, 400 mg/kg, and 300 mg/kg, respectively. This is carried out by using a reference index of the biomass of L. obtusifolium decreased by 10%, while the Cd threshold value needs to be further studied. L. obtusifolium would be an appropriate plant for phytoremediation of Cr-polluted soil, compared to Cd, Pb, and Zn absorption and accumulation. It showed optimal antioxidant enzyme activity and transfer ability under soil Cr contents of 300 mg/kg, and the growth of L. obtusifolium was not restricted. Therefore, L. obtusifolium was particularly suitable for phytoremediation of Cr pollution in areas in western China.

Investigating an electro-bio-chemical phytoremediation of multi-metal polluted soil by maize and sunflower using RSM-based optimization methodology

Accumulation of heavy metals (HMs) in soil has become a serious environmental problem due to various anthropogenic activities. Phytoremediation is one of the most cost-effective and environmentally friendly techniques for removing HMs from contaminated soil. However, it is remarked as a slow way of remediation, and it may need some amendments. Thus, in this study, a phytoremediation-based method of zinc (Zn) cadmium (Cd) lead (Pb) and nickel (Ni), comprised of sunflower and maize, was amended by the electro-bio-chemical treatments, comprised of ethylene glycol tetraacetic acid (EGTA), Bacillus subtilis and electrical current. Moreover, the performance of the system was optimized by the response surface methodology (RSM), to optimize the performance of both reactors. A high R2 value of non-linear second-order model showed satisfactory function of RSM in optimizing the performance of the remediation system. The electrical current and EGTA were the main significant factors in increasing growth parameters and translocation factor (TF) of some HMs, respectively. The highest values of shoot dry weight and TF were 15.62 g pot−1 (run 2) and 2.11 (run 4) which belonged to maize and Zn in sunflower, respectively. To achieve the highest possible response, the following optimal values were predicted: electrical current of 2 V cm−1, EGTA concentration of 0.04 mmol kg−1, and Bacillus subtilis level of 1.4 × 109 CFU pot−1 for maximized shoot dry weight efficiencies of 16.14 g pot−1. Also electrical current of 1.97 V cm−1, EGTA concentration of 1.68 mmol kg−1, and Bacillus subtilis level of 0.21 × 109 CFU pot−1 for maximized TF of Zn efficiencies of 1.6. The use of a combination of treatments was more successful than each treatment alone in the removal of HMs by maize and sunflower.

Organic fertilization and mycorrhization increase copper phytoremediation by Canavalia ensiformis in a sandy soil

Organic fertilization and mycorrhization can increase the phytoremediation of copper-contaminated soils. The time of vermicomposting alters the properties of vermicompost, which can affect copper's availability and uptake. Therefore, this study sought to evaluate the effect of different organic fertilizers and mycorrhization on copper-contaminated soil phytoremediation. The soil was contaminated with 100 mg Cu kg-1 dry soil and received mineral fertilizer (MIN), bovine manure (CM), and vermicompost produced in 45 days (V45) or 120 days (V120), all in doses equivalent to 40 mg kg-1 dry soil of phosphorus. Half of the jack bean (Canavalia ensiformis) plants were inoculated with the arbuscular mycorrhizal fungus Rhizophagus clarus. At plant flowering, the dry mass and concentrations of Cu, Zn, Mn, Ca, Mg, P, and K in the soil, solution, and plant tissue were determined, in addition to mycorrhizal colonization, nodulation, photosynthetic pigments, and oxidative stress enzyme activity. Organic fertilization increased plant growth and copper accumulation in aerial tissues. These effects were more evident with the V120, making it suitable for use in copper phytoextraction. Mycorrhization increased root and nodule dry mass, making it recommended for phytostabilization. C. ensiformis nodulation in Cu-contaminated soils depends on vermicompost fertilization and mycorrhization. Hence, the copper phytoremediation by C. ensiformis is increased by using organic fertilization and mycorrhization.

Comparative genome and metabolome analyses uncover the evolution and flavonoid biosynthesis between Apocynum venetum and Apocynum hendersonii

Apocynum species have great application prospects in textile and phytoremediation of saline soil, are rich in flavonoids, and possess medicinal significance. Here, we report the draft genomes of Apocynum venetum and Apocynum hendersonii, and elucidate their evolutionary relationship. The high synteny and collinearity between the two suggested that they have experienced the same WGD event. Comparative analysis revealed that flavone 3-hydroxylase (ApF3H) and differentially evolved flavonoid 3-O-glucosyl transferase (ApUFGT) genes are critical for determining natural variation in flavonoid biosynthesis between the species. Overexpression of ApF3H-1 enhanced the total flavonoid content and promoted the antioxidant capacity of transformed plants compared to the wild-type. ApUFGT5 and 6 explained the diversification of flavonoids or their derivatives. These data provide biochemical insight and knowledge on the genetic regulation of flavonoid biosynthesis, supporting the adoption of these genes in breeding programs aimed at the multipurpose utilization of the plants.

Cd uptake and translocation by camelthorn (Alhagi maurorum Medik): a promising approach for phytoremediation of Cd-contaminated soils.

Camelthorn (Alhagi maurorum Medik) is a desert plant that can withstand a variety of abiotic challenges, including water stress and harsh weather, making it potentially useful for cleaning cadmium (Cd) from contaminated soils. The current study aims to determine the degree of plant tolerance to Cd toxicity and the possibility of using it in the phytoremediation of Cd-contaminated soils. Camelthorn plants were cultivated in soil polluted with Cd at doses of 0, 25, 50, 100, and 200 mg kg-1. The growth, nutrient uptake, Cd concentrations, and some biochemical compounds were determined to study the response of camelthorn plants to Cd stress. Exposure of camelthorn plants to 200 mg kg-1 of Cd inhabited the synthesis of leaf-chlorophyll by 49% compared to the control and reduced the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), iron (Fe), and zinc (Zn) by 43, 36, 43, 50, 67, and 36%, respectively. Camelthorn plants can tolerate up to 11 mg kg-1 of available soil Cd, 65 mg kg-1 in the root, and 22 mg kg-1 in the shoot before experiencing Cd toxicity. Camelthorn plants increased the levels of carbohydrates, total phenols, and proline compounds that were used in the scavenging of reactive oxygen species (ROS). Moreover, the plants increased the activity of antioxidant enzymes, i.e., superoxide dismutase (SOD) and peroxidase (POD), to mitigate the oxidative stress caused by Cd toxicity. The root-shoot transfer (TF) of Cd varied between 0.27 to 0.48, while the bioaccumulation factor (BAF) varied between 1.2 and 2.32. Camelthorn plants have a BAF value higher than 1 and a TF value lower than 1. Camelthorn plants accumulate Cd in the roots with low root-shoot transfer and are suitable for phytostabilization technology. Camelthorn plants have a potent antioxidant defense against the toxicity of Cd, and this finding is a good tool in the remediation of Cd-contaminated soil.

Advancing environmental design with phytoremediation of brownfield soils using spontaneous invasive plants

Compared to traditional mechanical brownfield remediation strategies, phytoremediation as a sustainable and low-impact solution, yielding long-term soil chemical improvement. As a common part of many local plant communities, spontaneous invasive plants have advantages over native species in growth speed and resource-use efficiency and are many are effective on degrading or removing chemical soil pollutants. This research presents a methodology for using spontaneous invasive plants as the agent of phytoremediation for brownfield remediation is an innovative component of ecological restoration and design. This research explores s conceptual and applicable model of using spontaneous invasive plants in the phytoremediation of brownfield soil for environmental design practice. This research summarizes five parameters (Soil Drought Level, Soil Salinity, Soil Nutrients, Soil Metal Pollution, and Soil pH) and their classification standards. Based on the five parameters, a series of experiments were designed to examine 5 spontaneous invasive species' tolerance and performance to different soil conditions. Taking the research results as a data base, this research developed a conceptual model of selecting suitable spontaneous invasive plants for brownfield phytoremediation by overlaying the soil condition data and plants' tolerance data. Using a brownfield site in Boston metropolitan region as a case study, the research tested the feasibility and rationality of this model. The results propose a novel approach and materials for general environmental remediation of contaminated soil by involving spontaneous invasive plants. It also transforms the abstract phytoremediation knowledge and data to an applicable model which integrates and visualizes the requirements of scientific plant selection, design aesthetic, and ecosystem factors to help the environmental design process in brownfield remediation.

Arsenic (As) oxidation by core endosphere microbiome mediates As speciation in Pteris vittata roots

Pteris vittata is an arsenic(As)-hyperaccumulator that may be employed in phytoremediation of As-contaminated soils. P. vittata-associated microbiome are adapted to elevated As and may be important for host survival under stresses. Although P. vittata root endophytes could be critical for As biotransformation in planta, their compositions and metabolisms remain elusive. The current study aims to characterize the root endophytic community composition and As-metabolizing potentials in P. vittata. High As(III) oxidase gene abundances and rapid As(III) oxidation activity indicated that As(III) oxidation was the dominant microbial As-biotransformation processes compared to As reduction and methylization in P. vittata roots. Members of Rhizobiales were the core microbiome and the dominant As(III) oxidizers in P. vittata roots. Acquasition of As-metabolising genes, including both As(III) oxidase and As(V) detoxification reductase genes, through horizontal gene transfer was identified in a Saccharimonadaceae genomic assembly, which was another abundant population residing in P. vittata roots. Acquisition of these genes might improve the fitness of Saccharimonadaceae population to elevated As concentrations in P. vittata. Diverse plant growth promoting traits were encoded by the core root microbiome populations Rhizobiales. We propose that microbial As(III) oxidation and plant growth promotion are critical traits for P. vittata survival in hostile As-contaiminated sites.

Evaluation of the Bioaccumulation Capacity of Buddleja Species in Soils Contaminated with Total Chromium in Tannery Effluents in Arequipa (Peru)

The main purpose of this study is to evaluate the Buddleja species bioaccumulation capacity for the phytoremediation of soils contaminated with chromium produced by tannery effluents. The soils evaluated were collected from the Añashuayco stream, located in Arequipa region. The soil samples were collected from four different locations, in order to determine the presence of total chromium through the Environmental Protection Agency analytical technique, method 3050B acid digestion of sediment, sludge and soil. Three soil samples were analyzed for each collected location. Additionally, two non-contaminated soil samples (control group) were also analyzed. A Buddleja species seedling was placed in each sample to be monitored monthly for up to 90 days. Then, the plant tissue analysis was carried out by the analytical method of atomic absorption spectrophotometry in order to determine the amount of bioaccumulated total chromium. As a result, the Buddleja species bioaccumulated 30.45%, 24.19%, 34.55% and 40.72% of total chromium per each soil sample location in a period of 90 days. Therefore, the Buddleja species can be considered as an alternative to remediate soils contaminated with total chromium that comes from tannery effluents.

Enhanced phytoremediation of petroleum-contaminated soil by biochar and urea

Application of bioremediation in petroleum-contaminated soils is limited by its low efficiency. Although biochar and urea are commonly used soil additives, their potential beneficial effect on the bioremediation of petroleum contamination have rarely been discussed. In this study, biochar and urea were combined to test their effects on the phytoremediation of petroleum-contaminated soil in pot experiments. Our results showed that the degradation rate of total petroleum hydrocarbons reached 49.6%, 38.3%, 42.5%, and 77.9% when the soil was treated with biochar, urea, ryegrass, and their integrated application treatment (PBCN), respectively. A number of soil physicochemical properties (e.g., pH, elements, aggregate distribution, and organic matter composition) altered by the treatments were found to be linked to the accelerated degradation of petroleum hydrocarbons. The activities of soil dehydrogenase, lipase, and urease, and the abundances of 16 s rRNA gene and alkane degradation-related genes could be increased simultaneously when biochar, urea, and ryegrass were co-applied. Furthermore, urea significantly reduced soil bacterial α-diversity, while soil bacterial community dissimilation was mainly driven by urea and ryegrass. Lysobacter, xanthomonadaceae, and longimicrobia could be biomarker species in the PBCN group. Soil bacterial network analysis showed that biochar and urea application decreased the network complexity and robustness, while ryegrass behaved inversely. Lastly, soil metabolomic analysis revealed that root soil metabolites were greatly affected by urea-addition during phytoremediation, and co-application of biochar and urea could activate the putative metabolism pathway of petroleum hydrocarbons in root soil (e.g., naphthalene and anthracene degradation, and pyruvate metabolism). In summary, this study confirmed the enhancement of biochar and urea application in the phytoremediation of petroleum-contaminated soil and explored the internal mechanism of the interactive effect, which can potentially improve the development of eco-friendly and cost-effective in-situ bioremediation technology for petroleum-contaminated soils.

5-Aminolevulinic acid mitigates the chromium-induced changes in Helianthus annuus L. as revealed by plant defense system enhancement

Chromium (Cr) in the soil is one of the major pollutants for agricultural production. This study examined the efficiency of sunflower plants to remediate Cr-contaminated soils using a plant growth regulator, 5-aminolevolinic acid (ALA). At six leaf stage, sunflower plants were exposed to soil-applied Cr (0.15 g kg−1), manganese (Mn, 0.3 g kg−1) and trisodium (S,S)-ethylenediamine-N,N′-disuccinic acid (EDDS, 2.5 mmol kg−1), ALA (10 mg L−1) was sprayed. After ALA treatment, the plants were harvested for further biochemical analyses. Results showed that EDDS and Mn improved the Cr accumulation but restrained plant growth. Conversely, ALA improved the growth of Cr-stressed plants by promoting chlorophyll concentration in the top fully expanded leaves. The bioaccumulation quantity and removal efficiency of sunflowers treated by Cr + EDDS + ALA was improved by 47.92% and 47.94%, respectively, as compared to the Cr treatment. This was further supported by qRT-PCR analysis, where the expression of heavy metal transport genes such as ZIP6 and NRAMP6 and subsequently Cr accumulation in sunflower tissues increased by EDDS, Mn, and ALA application. However, compared with other treatments, ALA ameliorated cellular injury from Cr-stress by uptake or movement of Cr prevention, modulation of antioxidant enzymes, and elimination of reactive oxygen species. Our study suggested that ALA as an ideal option for the phytoremediation of Cr-contaminated soils.