Pollution of wetland ecosystems by heavy metals is one of the most important issues that has received special attention in recent years, and several studies have been conducted in this field (Huang et al., 2020). Because these ecosystems are naturally the ultimate recipients of heavy metals (Freedman, 2013). Heavy metals are important pollutants in natural environments, because due to toxicity, stability and biological decomposition, these elements tend to accumulate in aquatic organisms. Among different types of contaminants, heavy metals, even at low concentrations, have increasingly caused health concerns due to their hazardous bioaccumulation ability through the food chains (Li et al., 2014, Qiu, 2014). Various human activities cause these pollutants to enter the ecosystem. These elements enter the wetland ecosystems through direct or indirect discharge by rainwater runoff as well as through the atmosphere. Major sources include the direct entry of heavy metals into aquatic ecosystems, industrial and municipal wastewater and sewage, agricultural runoff, sailing and mining activities (Rai, 2008, Alloway, 2013).
Due to limited water resources and uncontrolled population growth and the expansion of industry and agriculture, the use of recycled water is essential and inevitable. Wastewater is one of the polluting factors in the environment, which needs to be collected, treated and returned to the natural flow of water (Feigin et al., 2012). Therefore, in order to implement measures to develop and exploit new water resources, especially in the agricultural sector, reuse of industrial, urban and rural effluents can be considered as reliable water resources to compensate for the shortage of agricultural water shortages. Rather, the adverse effects of wastewater waste disposal and its environmental damage should also be avoided. One of the dimensions of wastewater treatment, which is considered today, is biological treatment (Lepp, 2012). The use of plants in wastewater treatment, especially municipal and industrial effluents containing heavy metals, has received much attention. Because plants can grow extensively and absorb toxic metals at a lower cost than other biological treatment methods and are not as harmful to the environment as artificial systems, they are very cost-effective. In this regard, the limitations and standards of using this method should be considered, including care and care of plants and disposal of plant residues containing toxic substances after use in the treatment system (Chibuike and Obiora, 2014).
With the growth of industry and the unprincipled focus of industry, natural resources are at risk of extinction, and the level of biosphere pollution has increased dramatically. Heavy metals cause many problems for human health due to their inseparability in the environment and entering the food chain. Common methods of reducing and removing pollutants from the environment, in addition to being costly, are not able to completely remove pollutants from the environment; While the use of plants to clean the environment, in addition to helping to improve environmental conditions, is able to remove a significant portion of pollutants, especially heavy metals from the environment (Asad et al., 2019).
Over the past few decades, environmental pollutants from mining and industrial activities have increased. Soil contamination with heavy elements is one of the most important environmental problems in many parts of the world. Human activities, especially industrial activities and mineral processes, are the cause of the wider dissemination of these elements. The most important elements in terms of food chain contamination are As, Cd, Hg and Pb (Oves et al., 2012). At the same time, some nutrients, such as Cr, Cu, Ni, and Zn, can cause poisoning at high concentrations in plants and animals. Plants are important components of the ecosystem and are responsible for transporting elements from the environment to living organisms. The main sources of elements entering the plants from the environment are air, water and soil (Glick, 2003).
Phytoremediation plant is one of the methods of soil bioremediation that has received a lot of attention in recent decades (Sharma and Pandey, 2014). Compared to other refining methods, this method is a stable, inexpensive, simple and eco-friendly method. In this method, storage plants are used to purify contaminated soils without destroying the soil structure. Plant accumulators are plants with high growth rate, high biomass and high tolerance of metals (more than 1000 ppm) in harvestable parts of the plant that is able to transfer and accumulate in storage tissues (Tüze, 2003).
Various studies have been conducted on the sequestration of heavy metals in different ecosystems. Sasmmas et al. (2008) examined the role of Typha latifolia in the accumulation of heavy metals in the Kehli River. The results showed that the amount of heavy metals in the roots was higher than the leaves. Also, the amount of cadmium in the roots was higher than sediments and in the leaves less than sediments. This result showed that Louis root can be used as an indicator of cadmium contamination in the soil. Singh et al. (2010) states that plants that are able to absorb heavy metals abnormally have the genetic potential to clean up contaminated soils, and in fact the main advantage of these plants is that they can be absorbed and accumulated despite cultivation in contaminated metal or irrigated water. They have metal. Chaoua et al. (2019) investigated the accumulation of heavy metals cadmium, lead (Pb), nickel (Ni) and chromium (Cr) in mangrove swamps on the plant species S. apetala and K. obovata in China. S. apetala significantly altered the biochemical cycle of cadmium, Pb, Ni and chromium (Cr). In S. apetala deposition, TOC plays an important role in the sequence of heavy metals because its positive correlations with zinc and lead are reflected. This study showed the importance of plant species in changing soil quality and accumulation of heavy metals, and S. apetala works more efficiently as an inhibitor of contamination than K. obovata.
Meyghan desert Wetland and its 5459.9 Km2 of land, despite its diversity of soil and vegetation, beautiful lakes in the heart of the desert and the presence of migratory birds and other ecotourism attractions due to human intervention, its nature has undergone drastic changes. This wetland is considered as a sensitive wetland ecosystem due to its size, ecological and hydrological characteristics and the extent of its impact on the region's climate, especially the city of Arak. The entry of wastewater from the Arak wastewater treatment plant, which is a mixture of municipal and industrial wastewater, is a serious threat to the wetland ecosystem in terms of environmental pollution, especially the presence of heavy metals. Therefore,
the aim of the current study is, investigating the effect of 8 wetlandplant species on the phytoremediation of three heavy metals Al, Pb and Zn in the area around Meyghan Wetland.