Phytoremediation Of Contaminated Soil And Water Pdf
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Phytoremediation technologies use living plants to clean up soil, air, and water contaminated with hazardous contaminants. Although attractive for its cost, phytoremediation has not been demonstrated to redress any significant environmental challenge to the extent that contaminated space has been reclaimed. Phytoremediation is proposed as a cost-effective plant-based approach of environmental remediation that takes advantage of the ability of plants to concentrate elements and compounds from the environment and to detoxify various compounds.
- Phytoremediation of contaminated soils using ornamental plants
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Heavy metal—contaminated agricultural soil is a complex and serious phenomenon that has hazardous effects on the environment and, consequently, on humans, animals, plants, and beneficial microorganisms by influencing and tainting food chains, soil, irrigation or potable water, aquifers, and the surrounding atmosphere Wuana and Okieimen, Cadmium Cd is an important poisonous element that is not known for any essential biological function.
Furthermore, Cd may cause malfunctioning of metabolic processes Campbell, In plants, Cd causes various types of damage, such as the disturbance of metal homeostasis resulting in iron deficiency in the shoot Fodor et al.
As a result, the biosynthesis of chlorophylls, the formation of Chl—protein complexes, and the development of thylakoid membranes are highly disturbed Basa et al.
Copper Cu is an important essential micronutrient that participates in many vital physiological functions of plants, including acting as a catalyzer of redox reactions in mitochondria, chloroplasts, and the cytoplasm of cells Fargasova, or as an electron carrier during plant respiration Yruela, Increased Cu can damage membranes and produce free radicals in different plant parts Chen et al.
Lead Pb accumulation in plant tissue impairs different morphological, physiological, and biochemical functions in plants, either directly or indirectly, and induces a range of deleterious effects. Pb causes phytotoxicity by changing cell membrane permeability and reacting with active groups of various enzymes involved in plant metabolism Pourrut et al. Phytoremediation has become an effective and affordable technological solution used to extract or remove metal pollutants from contaminated soil using plants.
Plants possess a sophisticated and interrelated network of defense strategies to avoid or tolerate heavy metals or facilitate their de-toxification Harada et al. To reduce the harmful impact of free radicals resulting from heavy metal stress, plant cells have developed an antioxidant defense mechanism Sharma et al. Tree species have been suggested as appropriate plants for phytoremediation of heavy metal—contaminated soil because they provide several beneficial attributes such as large biomass, genetic variability, established management practices, economic value, public acceptability, and site stability Pulford and Waston, To achieve good phytoremediation efficiency, plants should accumulate a significant amount of heavy metals, tolerate soil pollution, and produce a great quantity of biomass under contaminating conditions McGrath et al.
The advantages of phytoremediation are mainly due to its effectiveness in reducing contaminant ions to very low levels. Moreover, it involves the use of an inexpensive bio-sorbent material Rakhshaee et al. Salix spp. Additionally, there has been a growing interest in their use for different environmental purposes and land reclamation, including phytoremediation and phytoextraction of contaminated soils Dimitriou et al.
Willows are recognized for their phytoremediation potential and phytoextraction of soils contaminated by heavy metals Vervaeke et al. Safsaf willow Salix mucronata , a member of the Salicaceae family, is a popular commercial tree in Egypt that is used for many industrial purposes Fahmy, It is indigenous to northern and tropical Africa and widely distributed throughout Egypt and Sudan. It is used for wind screening, planting in damp woodlands, waterside planting, coppicing, and remediation of contaminated sites.
However, there are accepted species names under the Salix genus, with intraspecific ranks for the genus worldwide, including 3 species in Egypt Fahmy, A previous study indicated that 34 species of Salix were used for phytoremediation Kersten, Of these, phytoremediation of heavy metal—contaminated soil involves S.
In general, these studies concluded that although growth and chemical parameters were negatively affected in the presence of heavy metals, these species could be used as phytoremediators to clean contaminated soil. However, there is no report of using S. Additionally, most previous studies involved acidic soil. Therefore, this study used alkaline soil to study the effects of Cd, Cu, and Pb on the growth and chemical and biochemical compositions of S. The relationships between the concentrations of these metals in plant organs and their concentrations in the soil were determined to facilitate the use of S.
Mature shoot cuttings 1-year-old wood 15 cm in length and 0. The cuttings were cultured in plastic bags 10 cm in diameter one cutting per bag filled with clay soil Table 1. The cuttings were watered manually every 10 d using L watering cans; the same water volume was applied to each bag.
After 3 months, homogeneous transplants with an average height of 35 cm and stem diameter of 0. Chemical analysis of the soil used for growth of Salix mucronata before plantation and 27 months after plantation. The clay soil used in this study was placed in plastic pots 40 cm in diameter with 9 kg of air-dried soil per pot, sprinkled with solutions of the aforementioned concentrations of metals and incubated for 60 d before being planted outdoors under a waterproof tarpaulin.
Soil without heavy metal contamination served as a negative control. Homogeneous 3-month-old plants were transplanted to previously prepared plastic pots one transplant per pot on 1 May The plants were placed in an open field after planting and were irrigated with tap water using L watering cans to reach field capacity when required. The experiment continued for 27 months. Soil analysis was performed before and after completion of the experiment Table 1.
Both physical and chemical analyses were performed; the particle size distribution was analyzed using a hydrometer method Gee and Balder, before planting only. The soil had a clay-like texture consisting of Soil pH was measured in a ratio soil: deionized water suspension using a calibrated pH meter Jenway, Staffordshire, UK. Soluble ions in saturated extracts were measured according to the methods of Jackson Total carbonate was determined using a volumetric calcimeter Nelson and Sommers, Organic matter content was determined using the dichromate oxidation method Nelson and Sommers, At the end of the experiment on 1 Aug.
The degree of greenness was measured on the fifth leaf from the apical meristem using a portable leaf chlorophyll meter SPAD; Minolta Corp. To determine antioxidant enzyme activities, 0. The reaction was initiated by adding the protein extract. For each measurement, the blank corresponded to the absorbance of the mixture at time zero, and the actual reading corresponded to the absorbance after 1 min.
One unit of CAT activity was defined as a 0. The reaction mixture contained 3. Changes in the absorbance at nm were recorded at 30 s for 3 min. The reaction mixture consisted of 2. Changes in absorbance at nm were recorded at s intervals for 3 min. Measurements were performed as described by Szalai et al. Flasks were shaken for 20 h at an ambient temperature to facilitate electrolyte leakage from injured tissues. Final conductivity was measured for each flask. Then, 0. The solution was left to cool before it was filtered and diluted to 50 mL with distilled water Evenhuis and de Waard, The total carbohydrate percentage in leaves was determined according to the methods described by Herbert et al.
The biomass tolerance index TI b was calculated to estimate the resistance of S. The experiment used a completely randomized design. Data were subjected to an analysis of variance using the SAS program version 6. A physiochemical analysis of the soil used for the growth of S. In addition, changes in organic matter and CaCO 3 content before and after planting were limited.
Conversely, cation and anion concentrations increased after planting using the Cd, Cu, and Pb treatments, except for control treatments, which were decreased. Regardless of the treatments, the changes in pH values were slight, but we noted a slight decrease in EC values after control planting.
The available concentrations of N, P, and K decreased in the control soil after planting compared with the soil before planting. In contrast, the available concentrations of N, P, and K were only slightly decreased in soil contaminated with high heavy metal concentrations. Furthermore, Cd, Cu, and Pb concentrations were deceased after planting relative to their concentrations before planting. There were negligible changes in pH values with the treatments used in this study.
Soil characteristics such as pH, organic matter O. The increased EC values may be due to the addition of metals, resulting in increased cations and anions. However, larger quantities of ions and soluble salts have resulted in increased EC values in industrial effluent-treated soil samples Sharma and Raju, Additionally, the reduction in available N, P, K, soluble cations, and Cd, Cu, and Pb concentrations after planting may refer to the uptake by plant roots or the loss to irrigation water.
It is known that plants were growing in soil with a pH of 7. These nutrients are extremely important for many components such as carbohydrates, proteins, amino acids, phospholipids, and energy components. In addition, Cd and Pb negatively impact the permeability of the plasma membrane Pourrut et al. Using different concentrations of Cd, Cu, and Pb significantly reduced most vegetative traits compared with control plants Tables 2.
The highest values for plant height, stem diameter, and the number of branches were reported for the negative control treatment group as Leaf area and vegetative fresh and dry weight exhibited the same trend for all treatments, showing a decrease with increasing heavy metal concentrations. Therefore, the reduction in root parameters was parallel to increasing heavy metal levels in the soil. The results showed that low heavy metal concentrations had the same significant effect as the controls on most traits.
Effects of different levels of cadmium Cd , copper Cu , and lead Pb pollutants on vegetative growth traits of Salix mucronata 27 months after plantation. Conversely, high concentrations of heavy metals had negative effects on all studied traits. Our findings indicated that vegetative growth and root traits were drastically inhibited, especially with medium and high heavy metal concentrations.
Tauqeer et al. These two toxic effects reduce the production of chlorophyll and, consequently, photosynthesis, which can lead to senescence and cell death Santos et al. Vegetative trait values gradually decreased with the increasing concentrations of each element in the soil. However, there was no plant lethality at any of the tested concentrations of the elements. Some toxic effects appeared on the adult leaves, such as yellow coloration and drying of the leaf edges after treatments with high heavy metal concentrations.
The reduction in growth and abscission of leaves were observed in Willow Tangio S. Additionally, the total leaf area of Willow clones was affected by In the present study, high concentrations of heavy metals suppressed root development of S.
Moreover, Yuan et al. In addition, Pb toxicity leads to the inhibition of photosynthesis, oxidative stress, DNA damage, and defects in mitosis Kupper,
Phytoremediation of contaminated soils using ornamental plants
The potential of Arundo donax L. The growth and physiology of plants were evaluated at the end of the experiment. Relatively low Cd uptake occurred during soil experiment with low translocation factor TF values. Consequent to global industrialization, heavy metal pollution is a widespread problem which has become a major environmental concern due to hazardous effects on human and environmental health. In industrialized societies, heavy metals are the world over environmental contaminants.
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Heavy metal—contaminated agricultural soil is a complex and serious phenomenon that has hazardous effects on the environment and, consequently, on humans, animals, plants, and beneficial microorganisms by influencing and tainting food chains, soil, irrigation or potable water, aquifers, and the surrounding atmosphere Wuana and Okieimen, Cadmium Cd is an important poisonous element that is not known for any essential biological function. Furthermore, Cd may cause malfunctioning of metabolic processes Campbell, In plants, Cd causes various types of damage, such as the disturbance of metal homeostasis resulting in iron deficiency in the shoot Fodor et al.
Heavy metal accumulation in soil has been rapidly increased due to various natural processes and anthropogenic industrial activities. As heavy metals are non-biodegradable, they persist in the environment, have potential to enter the food chain through crop plants, and eventually may accumulate in the human body through biomagnification. Owing to their toxic nature, heavy metal contamination has posed a serious threat to human health and the ecosystem. Therefore, remediation of land contamination is of paramount importance. Phytoremediation is an eco-friendly approach that could be a successful mitigation measure to revegetate heavy metal-polluted soil in a cost-effective way.
There are several different types of phytoremediation mechanisms. These are:. Rhizosphere biodegradation. In this process, the plant releases natural substances through its roots, supplying nutrients to microorganisms in the soil. The microorganisms enhance biological degradation.