Use In Phytoremediation Research Articles

Potential of Solanum viarum Dunal in use for phytoremediation of heavy metals to mining areas, southern Brazil.

Mining tailing areas may contain metal minerals such as Cu, Pb, Zn, Cr, and Cd at high concentrations and low nutrients for the growth of plants. This kind of conditions of the area, as well as lack of tailing structure, may limit the development of plants on these areas. Thus, the present study determined the metal, macronutrient, and micronutrient concentrations in the tissues of the roots and shoots of the Solanum viarum Dunal species as well as it evaluated the potential use of the plant for phytoremediation of mining tailing areas contaminated with heavy metals. The macronutrients, micronutrients, and heavy metals in the roots and shoots were determined by the digestion method with nitric and perchloric acid (HNO3-HClO4) and quantified by the ICP-OES. In S. viarum, the average concentrations of the metals presented in the dry biomass varied between the shoots and roots, being higher in the roots for metals such as Cu (229mgkg-1), Zn (232mgkg-1), Mn (251mgkg-1), Cr (382mgkg-1), Ni (178mgkg-1), Pb (33mgkg-1), and Ba (1123mgkg-1). S. viarum indicates the possibility of a potential application in phytoremediation and treatment of areas contaminated with heavy metals.

Effects and Removal of the Antibiotic Sulfadiazine by Eichhornia crassipes: Potential Use for Phytoremediation.

The antibiotic sulfadiazine (SDZ) is a challenging threat to the health of aquatic organisms, as it frequently occurs in aquatic ecosystems. Tolerance mechanisms and accumulation of SDZ in a floating macrophyte (Eichhornia crassipes) under hydroponic conditions were investigated in this study to provide more insight into the SDZ removal process. Results show that the presence of 1mg L-1 SDZ decreased the quickest and ranged from 669.45 to 165.34μg L-1 from days 5 to 25. Exposing E. crassipes to SDZ ( < 1mg L-1) maintained stable leaf photosynthetic efficiency. The overall increase in superoxide dismutase and peroxidase activities with SDZ treatments indicated that leaves were resistant. SDZ was absorbed by E. crassipes, following the sequence of root > aerial parts under all treatments. These findings suggest that E. crassipes has the ability to phytoremediation SDZ contaminated water.

Environmental and genetic effects on cadmium accumulation capacity and yield of maize

Maize (Zea mays) is an economic crop suitable for use in phytoremediation in low to moderately cadmium (Cd)-contaminated soils due to its ability to accumulate high concentration of Cd in parts of maize that are not used in human diet. The aim of this study was to test Cd content in nine female parents of the commercial maize hybrids (C1 = ♀2-48; C2 = ♀1767/99; C3 = ♀87-24; C4 = ♀135-88, C5 = ♀84-28; C6 = ♀84-44; C7 = ♀438-95; C8 = ♀30-8; C9 = ♀B-73) grown under field conditions in two soils (B1: eutric cambisol, B2: stagnosol) during three growing seasons (A1: 2006, A2: 2007, A3: 2008). The stationary trial was conducted in four replicates. The ear-leaves at flowering and grain at maturity were taken for chemical analysis. The average quantities of leaf-Cd were 0.081, 0.088 and 0.143 mg per kg of dry matter for A1, A2 and A3, 0.089 and 0.118, for B1 and B2, respectively. Grain-Cd was below the threshold (&amp;lt; 0.02 mg/kg). Five Cd-inefficient genotypes (C3, C5, C6, C7 and C9) had low leaf-Cd (average 0.049 mg/kg), while this content was about 6-times higher (average 0.299 mg/kg) in Cd-efficient genotype C4. The yield among the years ranged from 2.36 to 4.31 t/ha. Maize grown on B2 had about 26% lower yield than on B1. Five genotypes (C1, C2, C8 and C9) achieved yields less than 3.50 t/ha (mean 3.15 t/ha), while in two genotypes (C3 and C5) yields were above 4.00 t/ha (mean 4.14 t/ha). Very strong correlations (r) of leaf-Cd status among years (ranged from 0.52 to 0.77) confirmed high genetic effect on the capability of Cd accumulation in maize. However, correlations between Cd content and yield were low (ranged from –0.17 to 0.06). Cd-efficient C4 female parent could be used for development of maize hybrids suitable for phytoremediation, while Cd-inefficient female parents for hybrids could be suitable as forage maize crop contributing to the lower Cd input into food chain.

Accumulation of radioactive cesium in sorghum (Sorghum bicolor (L.) Moench) accessions cultivated in Fukushima in 2011 and 2012

ABSTRACT The accident at Fukushima 1 Nuclear Power Plant in 2011 caused contamination by radioactive cesium (134Cs and 137Cs) in surrounding areas. After this accident, concerns about Cs contamination, including food safety, have limited industrial activities and reconstruction in Fukushima. Sorghum (Sorghum bicolor (L.) Moench) is an annual C4 crop that can be used as biofuel feedstock due to its high biomass. Use of Cs-contaminated fields to produce biofuel feedstock would be more acceptable than use for food or feed crops due to the lower risk of human internal exposure to radioactive Cs. In addition, high-biomass sorghum might be suitable for removal of Cs from fields (phytoremediation). For both applications, it is important to use accessions showing the appropriate level of accumulation of radioactive Cs (low for biofuel feedstock, high for phytoremediation). Here, we examined the accumulation of radioactive Cs in the aerial parts of 56 sorghum accessions grown in Fukushima. Accessions were cultivated in a low-level-contaminated field in 2011 and in a highly contaminated field in a planned evacuation zone in 2012. After cultivation, activity concentrations from 134Cs and 137Cs were measured in the aerial plant parts. In 2011, the activity concentrations of 134Cs and 137Cs were 58.2–350 and 58.6–450 Bq kg−1 dry weight, respectively. In 2012, the concentrations of 134Cs and 137Cs were 54.2–1320 and 57.1–1960 Bq kg−1 dry weight, respectively. Relative to the median values of the accessions grown each year, 3 showed lower activity concentrations and 2 showed higher activity concentrations of radioactive Cs under both cultivation conditions. In contrast to a previous report, there was no significant correlation between biomass and Cs activity concentration. Because both biomass and Cs concentration are important in classifying accessions for use in phytoremediation, we also calculated the Cs accumulation index (single-plant biomass × Cs activity concentration) for each accession. The accession AKLMOI WHITE showed the highest values in both years, suggesting that this accession has the high per-plant accumulation capacity for radioactive Cs. Our data collected from actual contaminated fields is irreplaceable for choosing sorghum accessions for cultivation in Cs-polluted sites such as Fukushima.

Phytoremediation performance of Lemna communities in a constructed wetland system for wastewater treatment

Duckweeds are considered suitable plants for bioremediation of wastewaters because they can tolerate and take up diverse pollutants and large quantities of nutrients. They have year-round vegetative growth that can reach very high rates using wastewater nutrients that can accumulate intracellularly or be utilized to produce new biomass. The constructed wetland that services the town of Forano (Central Italy) is composed of three interconnected, but distinct, treatment pools (P1, P2, P3). In this study the phytoremediation performance of the whole treatment system was assessed taking into consideration pH, temperature, oxygen, nitrates, phosphates, sulphates, and pathogenic bacteria (Escherichia coli) at the inlet and outlet of each pool once per season over a year. The remediation efficiency of P2 was lower than in P1 and P3, and this was shown to be due to an extended, dense free-floating Lemna mat. The mat was thick enough (18–30 mm) to block light penetration, and heat and gas exchange to the underlying water resulting in dark, cool and near-anaerobic conditions. These conditions limited aerobic biodecomposition processes and natural control of the E. coli population. The underlying fronds of the Lemna mat in P2 were highly necrotic and became a source of nutrients, shown by an increase in nitrates and phosphates from the inlet to the outlet. Lemna use in phytoremediation is often considered highly important, but it is shown here that active management interventions are required and should involve periodic harvesting of Lemna fronds to avoid mat over-development and formation of necromass.

Effects of plant density on the bioremediation of soils contaminated with polyaromatic hydrocarbons

This study aims to evaluate the effects of plant density on the degradation of polyaromatic hydrocarbon (PAH) compounds in soils contaminated with crude oil. In this work, Axonopus compressus was applied as a bioremediator given its extensive and successful use in phytoremediation. A. compressus was planted at the density of three (pot-3), five (pot-5) or seven (pot-7) plants in pots containing soil contaminated with crude oil at the concentration of 20 g kg−1. Two pots were designated as controls: one containing unplanted soil contaminated with crude oil (pot-C) and one containing uncontaminated soil as control (pot-0). All planted and unplanted pots were irrigated with nutrient solution as needed. This study was performed for 2 months. The degradation of PAH compounds in soil was evaluated through ultraviolet fluorescence technique. Results showed that PAH degradation was enhanced as plant density increased. Specifically, after 2 months, PAH contents decreased by 69%, 75.8% and 82.3% in pot-3, pot-5 and pot-7, respectively, relative to those in pot-C. High plant densities mitigated the adverse effects of crude oil contamination on plant growth. Thus, this study demonstrated that high plant densities promote the phytoremediation of soil contaminated with hydrocarbon compounds.

Potential of Alfalfa for Use in Phytoremediation of Soil Polluted with Total Petroleum Hydrocarbons

Remediation technology is a promising technique decrease pollutant like hydrocarbons from the environment. An experimental work was made at green house of University of Technology in order to study the effect of crude oil on the vegetate growth and to measure the decrement which happened on shoot height, germination rate and the reduction of total petroleum hydrocarbon (TPH), which result, by this phytoremediation technique. The samples of soil were measured for TPH reduction and removal by Horiba model (oil content analyzer) OCMA–350. Five doses were used in this experiment (0 control, 10x103, 30 x103, 50 x103, 75 x103) (mg crude oil / kg soil). The polluted soil used in this study appeared to be a harmful environment for alfalfa plants, leading to serious adverse effects on alfalfa germination and growth. Seed germination is known to be a sensitive process affected by environmental factors like the presence of soil pollutants.

Overview of integrated phytoremediation for heavy metals contaminated soil

Heavy metal contaminated soil due to industrial, agricultural and municipal activities is becoming a global concern. Heavy metals severely affect plants, animals and human health. A suitable technology is necessary for heavy metals removal because it cannot self-decomposition as organic compounds. Among the various technologies surveyed, phytoremediation is one of the safest, most innovative, environmental friendly and cost-effective approach for heavy metals removal. Nevertheless, traditional phytoremediation practices pose some limitations such as long processing time, unstable treatment efficiency and limited application at large scale. In many methods proposed to improve phytoremediation, integrated phytoremediation has been studied in the recent years. Integrated phytoremediation use chelating agents and phytohormones to enhance phytoremediation. This is an environmentally safe, saving time and relative high effective method. Results showed that the association of a metal ion and a chelating agent to form chelates helps to maintain the availability of metals in the soil for the uptake of plants. Phytohormones supply nutrients for the soil to support vegetable growth. Therefore, integrated phytoremediation is a promising solution to overcome the disadvantages of conventional phytoremediation. It should be taken commercialization and need more applied projects in this field to demonstrate and clarify the real potential of this technology. In view of above, this manuscript reviews the mechanism and the efficiency of integrated phytoremediation for heavy metals in contaminated soil to give an overview of this technology.

Coping With Metal Toxicity - Cues From Halophytes.

Being the native flora of saline soil, halophytes are well studied for their salt tolerance and adaptation mechanism at the physiological, biochemical, molecular and metabolomic levels. However, these saline habitats are getting contaminated due to various anthropogenic activities like urban waste, agricultural runoff, mining, industrial waste that are rich in toxic metals and metalloids. These toxic metals impose detrimental effects on growth and development of most plant species. Halophytes by virtue of their tolerance to salinity also show high tolerance to heavy metals which is attributed to the enhanced root to shoot metal translocation and bioavailability. Halophytes rapidly uptake toxic ions from the root and transport them toward aerial parts by using different transporters which are involved in metal tolerance and homeostasis. A number of defense related physiological and biochemical strategies are known to be crucial for metal detoxification in halophytes however; there is paucity of information on the molecular regulators. Understanding of the phenomenon of cross-tolerance of salinity with other abiotic stresses in halophytes could very well boost their potential use in phytoremediation. In this article, we present an overview of heavy metal tolerance in case of halophytes, associated mechanisms and cross-tolerance of salinity with other abiotic stresses.

Impact of pollution on weeds phytosociology

THE ASSOCIATED vegetation to some Assiut province farmlands was investigated between two years (2015 and 2016). The recorded flora (82 species belonging to 25 families) revealed general dominance of the annuals (65% of the total flora). Cluster analysis as a classification method yielded two distinct groups (A and B). Stands of group “A” were restricted to the polluted areas and those of group “B” were confined to the non-polluted areas. Fifteen species were confined to the polluted areas (group A), 31 species were in the non-polluted areas (group B) and 36 species were represented in both. Presence (P %) of species within the different groups was used as monitor of ecological success and habitat performance. Those species represented in both areas but with high presence percentages in polluted area (eurytopic species), in addition to species confined to this area can be checked for their potential use in phytoremediation. Urtica urens was the most abundant invasive species tolerating serious pollution level. Therefore, it can be considered as an indicator species for polluted areas. The application of DCA and CCA as ordination techniques on the collected data revealed the dependence of group “A” vegetation on heavy metals and group “B” on major nutrients. Preliminary phytosociological studies, however, can provide useful information on the species of potential use in phytoremediation. Keywords: CCA, DCA, Heavy metals, Phytosociology

Adsorption of Cd(II) by rhizosphere and non-rhizosphere soil originating from mulberry field under laboratory condition

ABSTRACTIn this study, the adsorption behavior of Cd ions by rhizosphere soil (RS) and non-rhizosphere soil (NS) originated from mulberry field was investigated. The Langmuir, Freundlich and the Dubinin–Radushkevich (D-R) equations were used to evaluate the type and efficiency of Cd adsorption. The RS was characterized by lower pH but the higher content of soil organic matter and cation exchange capacity (CEC) as compared to NS. Also, the maximum adsorption of Cd2+ for RS (5.87 mg/g) was slightly bigger than that for NS (5.36 mg/g). In Freundlich isotherm, the Kf of the adsorption of Cd2+ to surface of the RS components was higher than that of the NS, indicating stronger attraction between Cd2+ and components of the RS. According to the D-R model, the adsorption of Cd2+ by both soils was dominated by ion exchange phenomena. These results indicated that mulberry roots modified physical and chemical properties of the RS under field conditions, which also affected the Cd sorption efficiency by soil components during laboratory experiments. Current knowledge of the Cd2+ sorption processes in the rhizosphere of mulberry may be important if these trees are planted for use in phytoremediation of Cd contaminated soils.

Contribution of NtZIP1-Like to the Regulation of Zn Homeostasis.

Tobacco has frequently been suggested as a candidate plant species for use in phytoremediation of metal contaminated soil but knowledge on the regulation of its metal-homeostasis is still in the infancy. To identify new tobacco metal transport genes that are involved in Zn homeostasis a bioinformatics study using the tobacco genome information together with expression analysis was performed. Ten new tobacco metal transport genes from the ZIP, NRAMP, MTP, and MRP/ABCC families were identified with expression levels in leaves that were modified by exposure to Zn excess. Following exposure to high Zn there was upregulation of NtZIP11-like, NtNRAMP3, three isoforms of NtMTP2, three MRP/ABCC genes (NtMRP5-like, NtMRP10-like, and NtMRP14 like) and downregulation of NtZIP1-like and NtZIP4. This suggests their involvement in several processes governing the response to Zn-related stress and in the efficiency of Zn accumulation (uptake, sequestration, and redistribution). Further detailed analysis of NtZIP1-like provided evidence that it is localized at the plasma membrane and is involved in Zn but not Fe and Cd transport. NtZIP1-like is expressed in the roots and shoots, and is regulated developmentally and in a tissue-specific manner. It is highly upregulated by Zn deficiency in the leaves and the root basal region but not in the root apical zone (region of maturation and absorption containing root hairs). Thus NtZIP1-like is unlikely to be responsible for Zn uptake by the root apical region but rather in the uptake by root cells within the already mature basal zone. It is downregulated by Zn excess suggesting it is involved in a mechanism to protect the root and leaf cells from accumulating excess Zn.

Improvement of degraded physical attributes of a saline-sodic soil as influenced by phytoremediation and soil conditioners

ABSTRACTThis study aimed to evaluate the use of phytoremediation and soil conditioners in the recovery of physical attributes of a saline-sodic Fluvic Neossol in Brazil Northeast. The applied treatments were: Atriplex nummularia L., as phytoremediation plant, due to its ability to extract salts from the soil; organic conditioners, such as bovine and sheep manure; gypsum and polymer, as chemical conditioners. Samples with preserved structure were collected at the time of the experiment installation and 18 months after in the layers 0–10 cm and 10–30 cm. The analyzed attributes were: water dispersed clay, dispersion index, bulk density, penetration resistance, soil porosity, and saturated hydraulic conductivity. The use of sheep manure, gypsum and polymer promoted an increase in saturated hydraulic conductivity in the 0–10 cm layer from 4.51 to 16.37 cm day−1, 11.26 to 23.95 cm day−1 and 7.24 to 22.77 cm day−1, respectively. Gypsum increased the macroporosity in the superficial layer by 42.6%. Atriplex and polymer were more efficient at reducing soil penetration resistance. The polymer was more efficient at improving the physical properties. However, it is necessary to consider phytoremediation with Atriplex as a more sustainable alternative that can still be used as complementary fodder in animal feed.

Cadmium tolerance of Typha domingensis Pers. (Typhaceae) as related to growth and leaf morphophysiology.

Typha domingensis (cattail) is a native macrophyte known by its capacity to tolerate several heavy metals effects and the potential use for phytoremediation. However, in despite that cadmium (Cd) is one of the most toxic pollutants; its effects in T. domingensis biology remain uninvestigated. Thus, the objective of this study was to study the tolerance of T. domingensis to cadmium contamination by evaluating its growth, Cd uptake, leaf anatomy and gas exchange. The experiment was designed using three cadmium concentrations (0, 10 and 50 µM) and ten replicates for 90 days. The cadmium uptake, growth, gas exchange, chlorophyll content and leaf anatomy were evaluated. Data was submitted to ANOVA and Scott-Knott test for P<0.05. Typha domingensis accumulates Cd proportionally to its concentration on the solution and the content of this metal was higher in roots as compared to shoots. Plants showed no significant modifications on growth parameters such as the biomass production, number of leaves, number of clones and the biomass allocation to organs. The photosynthesis, transpiration and chlorophyll content were not modified by Cd. Most anatomical traits evaluated were not modified by the metal but the stomatal density and the proportion of vascular tissues were reduced under 50 µM of Cd. In despite, the leaf anatomy showed no toxicity evidences for any Cd level. The absence of growth reduction and the stability of anatomical and physiological traits give insight about the Cd tolerance of this species. Therefore, T. domingensis is able to overcome Cd toxicity and shows potential for phytoremediation.

Brassica napus has a key role in the recovery of the health of soils contaminated with metals and diesel by rhizoremediation

Contaminated soils are frequently characterized by the simultaneous presence of organic and inorganic contaminants, as well as a poor biological and nutritional status. Rhizoremediation, the combined use of phytoremediation and bioremediation, has been proposed as a Gentle Remediation Option to rehabilitate multi-contaminated soils. Recently, newer techniques, such as the application of metallic nanoparticles, are being deployed in an attempt to improve traditional remediation options. In order to implement a phytomanagement strategy on calcareous alkaline peri-urban soils simultaneously contaminated with several metals and diesel, we evaluated the effectiveness of Brassica napus L., a profitable crop species, assisted with organic amendment and zero-valent iron nanoparticles (nZVI). A two-month phytotron experiment was carried out using two soils, i.e. amended and unamended with organic matter. Soils were artificially contaminated with Zn, Cu and Cd (1500, 500 and 50mgkg−1, respectively) and diesel (6000mgkg−1). After one month of stabilization, soils were treated with nZVI and/or planted with B. napus. The experiment was conducted with 16 treatments resulting from the combination of the following factors: amended/unamended, contaminated/non-contaminated, planted/unplanted and nZVI/no-nZVI. Soil physicochemical characteristics and biological indicators (plant performance and soil microbial properties) were determined at several time points along the experiment. Carbonate content of soils was the crucial factor for metal immobilization and, concomitantly, reduction of metal toxicity. Organic amendment was essential to promote diesel degradation and to improve the health and biomass of B. napus. Soil microorganisms degraded preferably diesel hydrocarbons of biological origin (biodiesel). Plants had a remarkable positive impact on the activity and functional diversity of soil microbial communities. The nZVI were ineffective as soil remediation tools, but did not cause any toxicity. We concluded that rhizoremediation with B. napus combined with an organic amendment is promising for the phytomanagement of calcareous soils with mixed (metals and diesel) contamination.

Microcosm investigation of growth and phytoremediation potential of Azolla japonica along nitrogen gradients

ABSTRACTAlthough Azolla species are among the most promising plants for use in phytoremediation, more studies on their growth and nitrogen (N) uptake along the N gradients of growing media are required. In this study, N concentration-dependent growth in growing media and phosphorus (P) and N accumulation by Azolla japonica were studied by estimating direct N uptake from media by molybdenum-iron proteins. The doubling time of A. japonica was less than a week, regardless of the N concentration (0, 5, and 25 mg N/L) present in the growth media, indicating that this plant is suitable for remediation. Plants showed a high uptake of P, probably via plant-bacteria symbiosis, indicating their potential for effective P remediation. A. japonica also showed more than 4% N content regardless of the treatment and accumulated more than 40 mg of N per microcosm in 3 weeks. iron and molybdenum levels in plants were strongly associated with N fixation, and N uptake from media was estimated to be more than 25 mg per microcosm in 3 weeks, indicating that A. japonica has N remediation potential. As A. japonica is a rapidly growing plant, capable of efficient P and N remediation, it has great potential for use in phytoremediation of nutrient-enriched waters such as agricultural or urban wastewater and eutrophicated aquatic ecosystems.

FITORREMEDIACIÓN DE UN SUELO CONTAMINADO CON PETRÓLEO EXTRA PESADO CON Megathyrsus maximus

Soil contamination by petroleum is an environmental problem and phytoremediation has proved to be a promising method for treating such soils. However, selection of species for use in phytoremediation is a key factor for its successful application. The aim of this study was to investigate the phytoremediation potential of the grass Megathyrsus maximus in heavy crude-oil contaminated soils. Temporal changes on total hydrocarbons and soil microbiological activity (enzyme activity of dehydrogenase, microbial biomass carbon and basal respiration) were evaluated in two treatments of oil contaminated soil, planted and unplanted with M maximus , over a 120-day period. Differences between both treatments were small but significant. Hydrocarbon concentration was reduced 17.1 % in planted soils and 9.8 % in unplanted treatments. Both saturated and aromatic hydrocarbon fractions were reduced in planted treatments but aromatics was the only fraction reduced in unplanted treatment. Biochemical and microbiological indicators varied temporally in the planted treatment but the unplanted treatment only showed differences for dehydrogenase enzyme activity and the metabolic coefficient. Microbial activity was always higher or similar in the planted treatment compared to the unplanted one, probably as a result of the rhizosphere favoring this activity.

Isolation of vanadium-resistance endophytic bacterium PRE01 from Pteris vittata in stone coal smelting district and characterization for potential use in phytoremediation

This study investigates the V-resistant endophytic bacteria isolated from V-accumulator Pteris vittata grown on stone coal smelting district. Among all the ten isolates, the strain PRE01 identified as Serratia marcescens ss marcescens by Biolog GEN III MicroPlate™ was screened out by ranking first in terms of heavy metal resistance and plant growth promoting traits. The S. marcescens PRE01 had strong V, Cr and Cd resistance especially for V up to 1500mg/L. In addition, it exhibited ACC deaminase activity, siderophore production and high indoleacetic acid production (60.14mg/L) and solubilizing P potential (336.41mg/L). For heavy metal detoxification tests, PRE01 could specifically assimilate 97.6%, 21.7% and 6.6% of Cd(II), Cr(VI) and V(V) within 72h incubation. Despite the poor absorption of the two anions, most V(V) and Cr(VI) were detoxified and reduced to lower valence states by the strain. Furthermore, the isolate had the potential to facilitate the metals uptake of their hosts by changing heavy metal speciation. Our research may open up further scope of utilizing the endophyte for enhancing phytoextraction of vanadium industry contaminated soils.

Анализ методов очистки нефтезагрязненных почв при авариях на объектах нефтегазовой отрасли и транспорте

Objective: Environment contamination with oil and concomitant contaminants is a burning environmental issue in many parts of Russia. Oil contamination has an effect on the overall set of soil morphological, physical, physicochemical and biological characteristics that govern its fertile and ecological functions. To reach a higher environmental safety level in the Russian oil and gas industry and transport, a multiple factor assessment of the existing oil-contaminated soil cleaning methods has been performed. Methods: Comparison of the existing oil-contaminated soil cleaning methods: mechanical, physicochemical and biological ones. Based on the systems analysis methods, phytoremediation is found to have a high potential for cleaning soils and groundwater contaminated with hydrocarbons as the above method is as a rule cheaper than any alternative soil cleaning methods. Plants do not deteriorate soil or add any secondary pollution as compared with conventional methods. In addition, the public has a positive attitude towards phytoremediation regarding it as an eco-friendly approach to cleaning contaminated soils. Results: Basic physiological and biochemical processes in plants causing a lower hydrocarbon concentration in soil are discussed. Criteria for selection of plants for phytoremediation are identified. The primary limitations on use of phytoremediation include a long soil remediation period, a significant impact of local climatic and hydrological conditions on plant growth, a plant exposure area is limited to less than 0.9 m from the soil surface (root layer), by an impossibility of growing plants in heavily contaminated soils, and also probable ingress of contaminants into food chains. It is shown that large-scale implementation of the method is held back as the method mechanisms are not sufficiently investigated. Practical importance: Phytoremediation is found to have a high potential for cleaning oil-contaminated soils and groundwater.

Phytoaccumulation of heavy metals (Pb, Zn, and Cd) by 10 wetland plant species under different hydrological regimes

Wetland plants have been widely used in constructed wetlands to remove metal contaminants from water and soil. This study aimed to investigate radial oxygen loss (ROL) rate, metal (Pb, Zn, and Cd) uptake, Fe plaque formation, and their relationships in a pot trial with 10 emergent wetland plant species grown in metal-contaminated soil under flooded and non-flooded conditions. The results showed that biomass, ROL rates, metal (Pb, Zn, and Cd) uptake, and Fe plaque formation on root surfaces and in the rhizospheres of the wetland plant species were remarkably higher under flooded conditions than under non-flooded conditions. Generally, flooding mainly increased metal accumulation in the roots and Fe plaque on the root surface of wetland plant species. The wetland plant species with higher ROL rates had higher biomass, Fe plaque formation and metal adsorption on the roots and in the rhizospheres under flooded conditions. These results suggest the wetland plant species with higher ROL rates, biomass and metal accumulation ability, e.g. C. alternifolius, has the potential for use in phytoremediation of metal-contaminated wetlands.