Investigation of Ecosystem Health of International Meighan Wetland


 Background: The aim of this study was to evaluate the ecosystem health of Meighan Wetland of Arak. Methods: To evaluate the Meighan Wetland of Arak, the status of benthic organisms and other parameters, sampling of sediments of the wetland floor was performed at 10 points of the wetland and at 5 replications at each point. Heavy metal pollution, biological, and water quality indices were also evaluated. Then, the map of ecosystem health was prepared. Results: The results showed that except for the nickel, zinc and lead, for other elements and compounds (EC, Na, Cl, Mg, Ca, HCO3, SO4 and TDS), the minimum and maximum values ​​belonged to stations 3 and 6, respectively. In the case of copper, zinc and lead, the lowest concentration was seen in the northwestern part of the wetland and the highest in the western and southeastern parts of the wetland. Conclusion: The high amount of the mentioned elements and compounds in station 6 may be due to the activity of a factory that produces sodium sulfate in the northern part of the wetland, which causes changes in the wetland ecosystem by removing sediments from the wetland floor. The high level of the copper, zinc and lead in the southern part of the wetland can be due to urban and domestic wastewaters that enter the wetland from the southwest of the wetland through the outlet channel of Arak refinery.


Introduction
Wetlands are valuable ecosystems that have a wide variety of functions to protect biodiversity, multiple natural, economic and social values (Fallah, 2017 & Fakhran). The Ramsar Convention de nes wetlands as swamps, sludges, lakes and rivers, natural or arti cial water, whether permanent or temporary, in which fresh, bitter and salty water are found stagnant or owing. The survival of many plant and animal species depends on the existence of wetlands, which are dynamic and complex aquatic ecosystems. Among the 84 wetlands of international importance in Iran, 24  Meighan Wetland of Iran is located 15 km northeast of Arak and is one of the important habitats of 140 species of birds. In addition to the main role in biodiversity, its seasonal lake has direct effects on controlling sand, salt and air pollution sources in Arak. It is like a bowl of water that stretches over an area of 5,000 square feet (Figure 1).
It is also an important winter habitat that attracts countless migratory birds especially, at least 5,000 Common Cranes per year from October to December (Behrouzi-Rad et al. 1997).
This area is also the habitat of unique plant species that has a very beautiful landscape. Since Meighan wetland of Arak has been affected by various stresses and environmental pollutants such as the entry of agricultural and urban industrial e uents. The e uent entering the wetland has reduced soil salinity in the southwestern part of the wetland and has helped to create a dense cover of Cyperus Cyperus eremicus (Ansari, 2008).
Pourimani et al. (2020) show that the presence of radium and thorium in sediments and water samples from the Arak wastewater treatment plant is less than the global average and its amount in the soil of the region is moderate. The speci c activity of 40 K is equal to the global average and the soil sediments around the areas are polluted with 137 Cs synthetic radionuclide, similarly. Radiological maps show that 226 Ra is mostly deposited in the vicinity of the inlet (S1) and 137 Cs is deposited in remote locations.
Fortunately, radiological parameters of water quality are within acceptable limits and is not considered a risk factor for the local population.
the presence of non-native species, land use change, the study of spatial and temporal changes of pollutants is one of the objectives of this study.

Materials And Methods
In order to evaluate the health of aquatic ecosystems and also to investigate the status of benthic organisms and other parameters, sampling of wetland sediments was performed in 5 repetitions from 10 points of the Meighan wetland ( Figure 2).
The following various indicators were used to assess the ecosystem health of the wetland: -The AZTI Marine Biotic Index (AMBI), which is obtained from the ratio between species resistant to stress gradients and increased pollution. This index is based on the distribution and frequency of soft bed communities in 5 ecological groups based on sensitivity and resistance, organisms against stress gradient and increased pollution. Due to the impact of humans on the environment, this index is used to measure the evolution of the environmental situation in certain areas. One form of AMBI is the classi cation of species into different groups according to the species' response to infection.
-The Hilsenhof Biotic Index (HBI) estimates the overall tolerance of a community in a sample area, which is weighed against the relative abundance of each classi cation group (family, genus, etc.). In this method, water is classi ed in terms of pollution with organic matter and the amount of index is calculated using the following equation. Accordingly, the higher index is a marker of the higher presence of animals with resistance, and this means high pollution of the study source.
-The business con dence index (BCI) provides information on future developments, based upon opinion surveys on developments in production, orders and stocks of nished goods in the industry sector.This index is designed to assess the environment and destructive or non-destructive systems in relation to the reference conditions and based on the response of benthic organisms to environmental stressors. This index includes: 1) Shannon-Wiener diversity index 2): Frequency for Tubi cida 3) Percentage abundance of bivalves 4) Percent abundance of capitelicidae family 5) Percentage abundance of two species.

Results
The AZTI Marine Biotic Index (AMBI), shows a good ecological status. The relationship between different indicators related to the health of Meighan wetland ecosystem and the concentration of different compounds in each station shows that there is no signi cant correlation between them (except in terms of acidity and nickel concentration). The value of regression coe cient in the mentioned parameters according to the graphs is higher than 0.5 and this shows a signi cant relationship between BC indices, nickel concentration and acidity (Diagrams 1-13).
The results show that the highest and lowest concentrations were obtained for copper, nickel, lead and zinc in mg/kg of sediments of the wetland oor dry weight. Based on sampling station, except for nickel, zinc and lead, for other elements, the lowest and highest values in mg/kg are for stations 3 and 6, respectively. In 3 and 6 stations, the lowest and highest values were as follows: 4.88 Mg/kg and 6.9 mg/kg for calcium 3.98 and 4.96 Mg/kg for magnesium 62.5 and 7.01 Mg/kg for sodium 6.18 and 7.71 Mg/kg for sodium sulfate. EC is equal to 85/1458 and 34/1821 ppm, while 3.69 and 4.60 are for HCO3, 67/4 and 83/5 are for chlorine (Table 2).
For pH scale values, the lowest (7.35 mg/kg) and highest (7.94 mg/kg) are for stations 3 and 7, respectively. In the case of nickel, the lowest (0.47 mg/kg) and highest (1.28 mg/kg) belong to stations 7 and 2, respectively. In the case of zinc, the lowest (0.47 mg/kg) and highest (1.28 mg/kg) are related to stations 3 and 10, respectively. In the case of lead, the lowest (0.25 mg/kg) and highest (0.64 mg/kg) are related to stations 2 and 3, respectively. The range of concentration changes of four heavy metals obtained in the sediments of the bottom of Meighan wetland in Arak coastal region in terms of mg / kg were for copper, nickel, lead and zinc, respectively.
The results of pollution factor analysis showed that most of the samples are in the category of unpolluted to low polluted coe cient. So that for lead metal, all stations and nickel, except for the rst 3 stations, the rest of the stations are in the lower pollution class (Table 5).
Also, in order to determine the situation of the region in terms of concentration of different elements, relevant maps were prepared. It was found that the levels of Ca, EC, HCO3, Mg, Na, PH, Cl and TDS in the southwest of the wetland are minimal and reach their peak in the northern part of the wetland. In the case of copper, zinc and lead, the lowest concentration is seen in the northwestern part of the wetland and the highest concentration is seen in the western and southeastern parts of the wetland (Table 5). According to BC and BI maps, the lowest concentration of pollution is concentrated in the southwest of the wetland and the lowest in the northwest of the wetland.

Discussion And Conclusion
In the present study, the concentrations of heavy metals (nickel, copper, zinc and lead) in the sediments of the bottom of Meighan wetland in Markazi (central) province were investigated. In the end, the results showed that the highest and lowest concentrations were obtained for heavy metals of copper, nickel, lead and zinc in mg/kg dry weight, respectively.
Examination of physicochemical characteristics of sampling stations showed that except for heavy metals nickel, zinc and lead and pH, for other elements and compounds (EC, Na, Cl, Mg, Ca, HCO3, SO4 and TDS), the lowest and highest values It corresponds to stations 3 and 6, respectively. The high amounts of elements and compounds in station 6 can be due to the activity of sodium sulfate factory in the northern part of the wetland, which changes the ecosystem of the wetland by removing sediments.
To determine the amount of sediment pollution to heavy metals, the concentration of compounds in the area should be compared with a known standard. In the meantime, comparison with the existing standards for the same region is one of these methods. In this study, due to the lack of speci c standards for pollution in the study area, global and existing standards in other countries were used. However, comparisons should be made with caution because there are different differences in properties or physicochemical parameters between their concentrations at different locations and times (38).
In fact, their average concentration was more or less depending on the type of metal and the place of measurement. But in general, the concentration of metals in the sediments of the study area was the same as the values determined for other studies conducted in Meighan wetland. In the case of heavy metals, minor pollution was observed in some parts of the region, so that in the case of nickel, the lowest (0.47) and highest (1.28) values were related to stations 7 and 2, respectively. In the case of zinc, the lowest (0.47) and highest (1.28) values were related to stations 3 and 10, respectively. In the case of lead, Most of the nickel is colloidal and is heavily deposited in estuaries and beaches. High nickel in some areas may be due to point sources or possibly the entry of municipal sewage sludge. Because municipal wastewater also has a signi cant amount of nickel with it (Darvishnia et al., 2015). and compounds Zinc is the twenty-fth most abundant element in the earth's crust, making up between 0.0005 and 0.02% of the earth's crust. Some heavy metals, such as copper and zinc, are essential micronutrients that in toxic concentrations have toxic and adverse effects on growth, while another element, such as lead, plays no major role in plant metabolism, although naturally It exists in soil (Pendias and Pendias, 1992).
A possible source of increasing concentrations of zinc and copper is the discharge of construction waste and household wastewater into the Meighan wetland. In the case of copper, in a study conducted in Italy, the amount of copper was 5.1 mg / kg, which is consistent with our ndings in this study (Tavassoli et al. Regarding BC and BI maps, studies indicate that the lowest concentration of pollution is concentrated in the southwest of the wetland (entry of treated wastewater from Arak into the wetland) and the highest concentration of pollution is concentrated in the northwest of the wetland (sodium sulfate Company). Therefore, the southern and southwestern areas of the wetland have relatively better conditions than its northern and northwestern areas.
The results of pollution factor analysis showed that most of the samples are in the category of unpolluted to low pollution coe cient. So that for lead metal, all stations and nickel, except for the rst 3 stations, the rest of the stations are in the lower pollution class in terms of the pollution factor of the zoning map of different elements and compounds.
The correlation between the physicochemical properties of the measuring stations along with their biological coe cient shows that there is a positive correlation between the biological coe cient (BC) and PH scale and HCO3 concentrations and a negative correlation between BC and Ni. There is also a correlation between copper and elements such as lead, potassium and nickel. This issue can be a sign of the common origin of their production from the rocks of the region and on the other hand shows the human contribution of the production of these metals due to urban development around the Meighan Wetland (Khodabakhshi et al., 2017).
Today, heavy metals pollution in aquatic ecosystems due to properties such as toxicity, carcinogenic potential and high mutagenicity, very long stability, high accumulation at different levels of the food chain are one of the biggest problems and concerns worldwide. Therefore, in order to determine the health of the wetland, the pollution conditions of this ecosystem were evaluated. This evaluation was done by examining the samples taken from the sediments of the wetland oor and also examining the water quality of the wetland based on the indicators used and the biological index of wetland health.
According to studies, it was found that the health of the wetland is in two oors, non-polluted and low pollution. In general, the situation in the wetland area indicates a situation with relatively low pollution in the area. The results of pollution factor analysis showed that most of the samples are in the category of unpolluted to low pollution coe cient. So that for lead metal, all stations and nickel, except for the rst 3 stations, the rest of the stations are in the lower pollution class. In areas that are not polluted, it indicates that in those areas either the required data may be not available enough or they are well protected. In the northern parts of the wetland, due to the presence of sodium sulfate plant, the concentration of salinity elements increases as a constant trend.
Examination of data related to heavy metals shows that the wetland area is in a non-polluted to low pollution state from the point of view of heavy metals. Therefore, it can be concluded that heavy sediments on the bottom of the wetland are not a good indicator of ecosystem health and cannot re ect the reality of the wetland well. In general, the effect of mineralization in the region on the concentration of elements and compounds in the sediments of the wetland oor of the deposit area as a natural and terrestrial factor and the effect of Arak wastewater treatment plant e uent as an anthropogenic factor in increasing the concentration of elements and compounds is obvious.
In this regard, it is suggested that periodic monitoring of pollutants and conducting appropriate scienti c research in the region be strengthened. Also, new warning systems and appropriate protective measures should be taken by executive organizations in this regard. Also, evaluations of the wetland area should be done periodically to effectively contribute to the sustainable development of the wetland. Tables   Table1-relatioship between biologic factors and