جستجوی مقالات مرتبط با کلیدواژه « تالاب شادگان » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

Shadgan wetland is the largest international wetland in Iran and the livelihood needs of local communities depend on it. Therefore, the health of wetland fish is of great importance as the main source of food for marginal residents. Mercury as an accumulating pollutant was studied in aquatic food chains. Based on this, 3 fish species were sampled including binni, carp, and tilapia in the fishing season and the water of wetland was sampled in spring and summer from three selected stations. Mercury concentration in fish tissue was measured using direct mercury analyzer (DMA 80) device and in water samples with atomic absorption device. To determine the permissible limit of mercury in wetland water, based on USEPA guidelines, the mercury bioaccumulation factor (BAF) in the food chain in wetland water and mercury concentration criterion in fish tissue (TRC) were calculated based on the consumption pattern of wetland residents. The average mercury concentration of water samples was 0.11 µg/l in the summer season. The mean concentration of mercury in Shadegan wetland fish was 22.18 µg/kg wet weight. The average BAF of mercury was 41.69 l/kg. The mean of TRC of the wetland was 22 µg/kg, and the permissible limit of mercury in the wetland water was 0.53 µg/l. Although the amount of mercury in the water and fish of the wetland was lower than the USEPA standard limits; but the high consumption of fish by local people and the higher average amount of mercury in wetland fish compared to the calculated TRC indicate the possibility of mercury risk to the health of local consumers. It is also necessary to monitor mercury pollution in this wetland.

Evaluating the metals concentration and their environmental risk for pollution monitoring is necessary to maintain the quality and the health of the ecosystem. In this study, the distribution and ecological risk assessment of heavy metals in the sediments of the estuaries around the petrochemical units were investigated. The purpose of this research is the pollution value and ecological risk assessment of heavy metals in the sediments in Shadgan wetland. A systematic method of random classification was used to determine the sampling points and 36 sediment samples were collected and transferred to the laboratory for analysis. Preparation and complete digestion of sediments were performed according to standard Mopam instructions. For analyze to of samples, was used ICP-OES model 730-ES device. Important environmental indicators such as the geochemical index (Igeo) and ecological risk index (ERi) were calculated. Based on the results obtained, mean concentrations of Ni, Pb, Hg, and V were 55.8, 8.5, 6.9 and 88.7µg/g, respectively. The research results showed that distribution pattern of heavy metals in the sediments was V>Ni>Pb>Hg. Based on Muller's geochemical index, pollution degree was severe contamination for nickel and lead, severe to very severe contamination for mercury, and moderate contamination for vanadium. The ecological risk index (ERi) analysis showed that the risk situation is considerable for Ni, Pb, and Hg and moderate for V. It can be concluded that the Shadgan wetland is contaminated with heavy metals due to the inflow of effluents from petrochemical industries. The use of modern treatment plants, decomposition of pollutants and the use of raw materials with a lower percentage of pollutants in wastewater management are necessary to reduce pollutants.

Soil moisture is one of the key parameters in watershed and water resources studies. Field measurement of this parameter is extremely difficult, time-consuming and costly. Hence, in recent years, numerous satellite-based methods for estimating and modeling soil moisture have been developed and presented. Among proposed methods, surface energy models performed better and have a higher degree of accuracy because of their physical nature. But, due to their particular complexity, they have been used rarely. Therefore, this research was carried out to estimate soil moisture using Landsat 8 Satellite imagery and Surface Energy Balance System (SEBS) near the Shadegan Wetland, located in the south-west of Iran. For this purpose, volumetric soil moisture content was measured at 39 points on 27 June 2016, simultaneous with the overpass of Landsat 8 Satellite over the study area. After necessary image processing, the was calculated using the applying the SEBS on satellite image. Then, the evaporation fraction was used as the main input in an experimental model (saturation ratio model) for estimating the soil moisture. Results showed the good ability of the model for estimating soil moisture with the coefficient of determination of 0.69 and the RMSE error value of 0.03 . It can be concluded that combination of remote sensing data, surface energy balance system and the experimental model of soil moisture can be used for modeling soil moisture in a large scale.

Study of surface sediments of southern Khuzestan plain in Shadegan marshes surroundings was made to understand the nature of the sediments, their classification and determining the most effective physical and chemical characteristics of sediments change. Samples were taken from 27 points inside the work units. The chemical characteristics of sediment samples containing calcium carbonate, calcium sulfate, sodium chloride, sodium, magnesium, calcium, electrical conductivity, pH and sodium absorption ratio, was measured. After removal all carbonates and evaporates materials, the portion of carbonates-evaporates and terrigenous parts, was specified. Granulometry for terrigenous part was done for terrigenous materials. The new method of classification was performed for these fine sediments containing solutes, which considers the portion of the chemical and terrigenous parts, was performed.
In order to specify the most effective factors and variables in the sediment variability, factor analysis and cluster analysis were used consequently. Classification results showed that the sediments are marl, with similar components with Iran tertiary marls. Two main factors, the components of the new classification and the chemical characteristics were controlled sediments variability, while the chemical characteristics had more effective roles. According to the results of cluster analysis, Sodium was the most effective variable which its value varies up to more than 20 in different work units. The results of this study show that the use of the new method of classification together with statistical analysis led to extract more details from flat and broad playa and sabkha environments.

One of the important aspects of the management of wetlands in possession of various aspects of their economic value, which indicates the importance of natural resources for the residents of a region or country. In general, wetlands benefits are divided into two categories of use and non-use. This study sought nonuse value of the wetland through modeling preferences and willingness to pay is calculated and put at the disposal of policy makers and society. In this regard, using the choice experiment, the nonuse value of Shadegan wetlands was estimated. Therefore, the design and implementation of the choice experiment and completing 120 questionnaires in Ahvaz and Abadan, combined with a random coefficient logit model estimate values for wetland features include biodiversity, ecological function, educational services and natural scenary were estimated. The values obtained were extended to the whole society the enjoyment of these blessings. The results showed that all variables of the model (including wetland features and price) statistically significant at 95 percent and have expected signs. The estimated marginal willingness to pay for nonuse benefits suggest that the value of the improve the quality of each wetland features for people who wish to visit wetlands in the future is not significant. Calculations showed that the value of wetland benefits is equal to 4,303,395,852,380,952 Rials. So, by adding this value to the province's gross domestic product, the share of the wetland benefits is more than 2 percent. The numbers showed the importance of wetlands for society as well as the susceptibility of the conditions to comply with its conservation policies.

As a cansequence of Marun dam construction on the Jarrahi River, qualitative and quantitative changes of inflow is an ecological threat on wetland ecosystem. In order to prevent the long- term negative impact of the projects on the ecosystem, it is necessary to assess the environmental flow and optimum water allocation for different uses. In this research, environmental flow indices were investigated using hydrological analysis of wetland inflow at Jarrahi River. Environmental flow estimated in Shadegan wetland are 6.83, 1.54 and 3.18 m on Montana method, environmental flow is estimated 1.54 and 3.6 m respectively. The results have shown that environmental flow indices were decreased after dam construction in all hydrometric stations. 3/s based on duration curve, Aqua France law and Smakhtin methods, respectively. Base 3/s in first and second part of year.