As a result of human activities, Metal pollution has become one of the most serious environmental problems today. Phytoremediation utilizes plants to uptake contaminants and can potentially be used to remediate metal-contaminated sites. A pot experiment was conducted to compare the phytoextraction and PHYTOSTABILIZATION potential of two plant species (Populus alba and Morus alba) for some elements. Thus, Cd (40, 80, and 160 mg/kg), Cr (60, 120, and 240 mg/kg) and Ni (120, 240, and 480 mg/kg) were added to the soil, shoots and roots of studied species. Associated soil samples were collected and analyzed by measurement of total concentration of Cd, Cr and Ni and then bioconcentration factor (BCF) and translocation factor (TF) calculated for each element. Our results show that none of the plants were suitable for PHYTOSTABILIZATION of studied elements with root BCF<1 and TF> 1. In addition, Populus alba with the shoot BCF> 1 for Cd in all studied treatments and Ni in 240 and 480 mg/kg treatments were suitable for phytoextraction while Morus alba was suitable for phytoextraction of Ni with the shoot BCF> 1 in all studied treatments.

The technology of phytoremediation is cost effective and ecologically friendly in which plant utilizes its natural abilities to restore environment. In nature there are a number of plants existing with innate mechanisms for removing heavy metals from soil, air and water as a survival strategy. Among several subsets of phytoremediation, the widely studied strategies are (a) phytoextraction (b) phytofiltration (c) phytovolatilization and (d) PHYTOSTABILIZATION. Application of organic / inorganic chelants in soil directly affects the solubility of heavy metals and consequently increases their accumulation in plants that enhances phytoextraction. In the present review current knowledge about the phytoremediation and its techniques are discussed.

Background and Objectives: Today, it is necessary to develop biological soil remediation methods that are cost-effective and eliminate pollution without degrading soil fertility. So, studies have been done to reduce the mobility and bioavailability of heavy metals. Recently, biochar is widely used to reduce the toxicity of heavy metals. Biochar is a carbon-rich organic matter, which is produced from pyrolysis of residues under limited oxygen conditions. It is made up of polycyclic aromatic hydrocarbons in which carbon atoms are annularly bounded. Aromatic structure makes it resistant to biological and chemical changes. This carbon-rich material has many functional groups such as, hydroxyl, ketone, ester, aldehyde, amine and carboxyl and significant amounts of humic and fulvic organic acids, which their composition and heterogeneous surface can exhibit different hydrophilic or hydrophobic properties and acidic and basic features. Therefore, biochar has the capacity to stabilize organic and inorganic materials. Furthermore, this material can reduce the risk of entering heavy metals contamination into food chain due to its surface area, porous structure, high pH and CEC. The aim of this study was to investigate the application of Walnut leaves and biochars produced from which at three temperatures of 200, 400 and 600 ° C on the availability and uptake of lead by maize (Zea mays L. Cv. Single cross 704). Materials and Methods: In this study, a pot experiment was conducted, consisting of soils treated with 0, 0. 5, 1 and 2 percent (w/w) of Walnut leaves and its derived biochars produced at 200, 400 and 600 ° C. Walnut leaves and biochars were mixed with 3 kg of soil in 3 replicates and were incubated for 45 days in greenhouse conditions. After incubation, 3 seeds of maize were planted in each pot while adding fertilizers needed. Shoots and roots were harvested after 8 weeks of planting. The maize indices (shoot and root dry weights, Pb and Zn concentration in shoots and roots, bioaccumulation factor and translocation factor) and DTPA-extractable of pb in soils were determined. Results: The results showed that DTPA-extractable of pb and its bioaccumulation reduced by increasing the producing temperature and the application rate of biochars in calcareous soils. Treating soil with 0. 5, 1 and 2% of biochar produced at 600 ° C, significantly reduced pb concentration in shoots by 31. 3%, 33. 5%, 36. 1%, respectively and pb concentration in roots by 32. 0%, 35. 6% and 36. 2%, respectively (P<0. 05). Physiological responses showed that modifiers were effective for increasing the ratio of shoot to root of maize throughout its growth. Treating soil with 2% of biochar produced at 600 ° C, increased significantly the dry weight of shoot and root by 131. 4% and 116. 7%, respectively compared to the control. Also, results showed that the DTPA-extractable of pb decreased by increasing the producing temperature and the application rate of amendments in soils. Treating soil with 0. 5, 1 and 2% biochar produced at 600 ° C, reduced the Bioavailable soil Pb concentrations (DTPA extraction) by 35. 3, 40. 1 and 49. 1%, respectively (P<0. 05). Therefore, biochars were able to reduce the contamination of Pb in treatments and increase maize dry weight. Conclusion: Biochar decreased the concentration of Pb in plant tissues and increased maize growth by reducing the bioavailable soil Pb concentrations (DTPA extraction). Therefore, biochar can be assisted to maize for phytostabilizing Pb in soil and improving phytoremediation.

In desert reclamation strainer plants can be used for improvement and decrease pollution of soil and water. This technology can be used to remove both inorganic and organic contaminants in soil. In this study, one year old Acacia victoriae seedlings were exposed to Pb (NO3) 2 in 5 different concentrations; 0, 50, 250, 500 and 1000 mg Pb L-1 for 45 days in two growing seasons. Subsequently, the heavy metal concentrations were measured in different plant tissues by Atomic Absorption Spectroscopy (AAS) for two growing periods. In addition, some physiological and morphological parameters (root and plant length, root diameter, leave area, dry weight, chlorophyll a, b and total) were measured. Based on the results, the visible toxicity symptoms (chlorosis and necrosis) appeared only to the highest concentration (1000 mg Pb L-1) in both growing seasons. The results also showed that application highest concentration of Pb reduced the physiological and morphological parameters as compared to the control seedlings. The accumulation of Pb was influenced by the Pb concentration in the growth medium and the growing seasons as well. With respect to the more accumulation of Pb in the roots tissues than aboveground tissues, indicating A.victoriae as a good option for PHYTOSTABILIZATION of Pb contaminated soils. Furthermore if A.victoriae is planted for Pb phytoextraction, therefore the harvest of aboveground should be done at the fall season. Meanwhile concentrations of Pb in the aboveground parts were more than roots at the fall season. In conclusion A.victoriae a native to the arid zone appeared to be hyper tolerate, accumulate high concentrations of Pb and it could be regarded as a potential accumulator. In addition A.victoriae have high application value in repairing Pb contaminated soils and is suitable and effective choice to be used as a tool of phytoremediation in industrial sites of the arid zones. Our findings suggest that A.victoriae has the advantages of high capacity for adaptation to poor, easy cultivation, deep root system, high tolerance to the drought, saline soils and Pb and could use as candidate plant for environmetals monitoring.

Athyrium wardii (Hook.) is a promising herbaceous plant species for PHYTOSTABILIZATION of cadmium (Cd) contaminated sites with large biomass and fast growth rate. However, little information is available on its tolerance mechanisms towards Cd. To further understand the mechanisms involved in Cd migration, accumulation and detoxification, the present study investigated subcellular distribution and chemical forms of Cd in the mining ecotypes and corresponding non-mining ecotypes of A. wardii via greenhouse pot experiment. Subcellular fractionation of Cd-containing tissues demonstrated that the majority of the element was mainly located in soluble fraction in cell walls. This indicated that both the vacuoles and cell walls might be evolved the Cd tolerance mechanisms to protect metabolically active cellular compartments from toxic Cd concentrations. Meanwhile, Cd taken up by the plant existed in different chemical forms. Results showed that the majority of Cd in plant was in undissolved Cd-phosphate complexes (extracted by 2% CH3COOH), followed by water soluble Cd-organic acid complexes, Cd (H2PO4) 2, pectates and protein form (extracted by deionized water and 1 M NaCl), whereas only small of Cd in roots was in inorganic form (extracted by 80% ethanol) which suggests low capacity to be transported to aboveground tissues. It could be suggested that Cd integrated with undissolved Cd-phosphate complexes in cell wall or compartmentalization in vacuole might be responsible for the adaptation of the mining ecotypes of A. wardii to Cd stress.

The objective of the present study was to compare the potential accumulation capacity of Cr, Cu and Zn in Zea mays and Populus deltoides Marsh. The study was conducted in an area in a wastewater treatment plant in Birjand for a period of 120 days. The soil sample and selected parts of Z. mays and P. deltoides Marsh were collected monthly and treated with hydrochloric acid and nitric acid. The results showed that the highest mean concentrations of Cu (1.78 ± 0.93 mg kg-1) and Zn (2.65 ± 1.37 mg kg-1) were observed at Z. mays in September. The results indicated that the concentrations of Cu and Zn in Z. mays and P. deltoides Marsh shoots irrigated with wastewater were higher than tap water. In addition, both the plants comparatively showed a significant increase in total metal amount when treated with wastewater (p < 0.001). The study of BCF and TF demonstrated that Z. mays was suitable for phytoextraction of Cu, but unsuitable for both phytoextraction and PHYTOSTABILIZATION of Zn and Cr, whereas P. deltoides Marsh was unsuitable for both phytoextraction and PHYTOSTABILIZATION of Zn, Cu and Cr.

As a result of human activities, metal pollution has become one of the most important challenges in soil and water conservation area today. Phytoremediation utilizes plants to uptake contaminants and can potentially be used to remediate metal contaminated soils and waters. This study was carried out with the aim of assessing the ability of Acacia victoriae three months old seedlings in the accumulation of cadmium in their parts (stem and root), transfer it from the roots to the stems and to understand the effect of Cd accumulation on some morphology attributes of the plant. For this purpose, 12 seedlings of A.victoriae three months old seedlings were exposed to Cd in 4 different concentrations: 0, 10, 50 and 100 (mg/l) for period 45 days in completely randomized design with 3 replicates per treatment were considered. The results showed significantly reduction of height, biomass and resistance were observed, compared to the control plants and also symptoms of toxicity in the leafs which become thin, yellow and with brwon spots in high concentrations of Cd were notably. Also Cd accumulation in roots and aerial parts increasing trend with increasing Cd supply up to 100 (mg/l) and root tissue concentration regards to Cd concentration was higher than stem tissues concentration at all treatments. Cd were accumulated in the roots, stems and leafs of seedlings, more than 72% (19433.33 mg/kg), under 17% (4630 mg/kg) and under 11% (2853.33 mg/kg) exposed to 100 (mg/l), respectively. Bioconcentration Coefficient root and stem, Translocation Factors, Enrich Coefficient and Uptake Index were determined 184.9, 71.20, 0.39, 0.014, 7697.73 mg/kg in high concentrations of Cd, respectively. Indeed, the results confirmed that A.victoriae had the ability to accumulate Cd in the roots so that prevented Cd toxicity symptom. Generally, this desert plant can be used in the process of remediation of Cd soil polluted by way of PHYTOSTABILIZATION.

Using the synergistic relations between plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) is a sustainable and economically significant management method for growing plants in soils with heavy metal contamination. A greenhouse experiment was carried out using corn plant in a factorial design with four Cd levels of zero, 10, 20, and 30 mg kg-1 and four microbial inoculation including control (C), PGPR inoculation (B), AMF inoculation (F) and PGPR+AMF (BF). PGPRs inoculant was a mixture of fluorescent Pseudomonads and the AMF isolate belonging to Glomus versiforme. After 98 days, plants were harvested and shoots and roots were separately weighed and dried. Growth parameters and Cd concentration and content (accumulation) were determined in different parts of the plants. Analysis of variances showed that different Cd levels and microbial inoculations significantly affected the measured indices. High concentration of Cd decreased shoot dry weight, and increased Cd concentration as well as Cd content compared to non-contaminated treatments by 1.8 and 1.4 fold, respectively. Accumulated Cd in plants of Cd0 treatment was 250 mg/pot and significantly increased in Cd30 treatment (966 mg/pot). Microbial inoculation of corn led to an increase in plant biomass compared to the control plants in the contaminated condition. The highest plant biomass (27.5 g/pot) was achieved in PGPR inoculation which 3.4 times higher than that of the control plants (8.1 g/pot). Microbial inoculation increased significantly (2.57 fold) Cd uptake in comparison with control condition. Among microbial treatments, PGPR inoculation showed the highest effect on shoot dry weight and Cd accumulation. Microbial inoculation reduced the concentration of shoot Cd, however, due to higher plant biomass, Cd accumulation increased in the whole plant. It is concluded that PGPR and AMF inoculations resulted in increasing phytoextraction and PHYTOSTABILIZATION of Cd, respectively.