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+1.96 has experienced an upward turn and can confirm the existence of time series in Hamedan-Airport station. Figure 2. GraphicalKendalltest, Hamadan-airportweather station The results of Mann-Kandall model in weather station of Malayer in the period 1994 to 2013, due to inclusion of Line u for two indicators of temperature and precipitation in the range and failure to observe the trend due to placement of random series in data of this station does not show a significant trend for these indicators. Figure 3. GraphicalKendalltest, Malayer weather station Investigation of drought indices according to Figure 5 represents that based on RAI index in the years 1985, 1990, 1995, 2001, 2008, Hamedan- Airport Station has experienced very dry years and in the rest of the study period, the region has experienced moderate or mild drought. Figure 4.Trends of changes of Drought Indices in Hamadan- Airport weather station Investigating the drought index in Hamedan- Nozheh station showed that for the years 2013, 2012 and 1999, the region has experienced severe dry years according to RAI index. In other years, the region has not been in satisfactory condition, and has experienced years with relative drought. Figure 5. Trends of changes of Drought Indices in Hamadan- Nozheh weather station Evaluating trend of changes of drought in Malayer Station in terms of RAI index showed that in the years 1995, 1997, 1998, 1999 and 2008, the drought index has been in cute conditions. And the rest years of the study period in this station are associated with normal or mildly drought. Figure 6. Trends of changes of Drought Indices in Malayer weather station Discussion: The study area around the wetland, over a 30-year study period (1984-2013), according to climatic conditions in meteorological stations did not have stable conditions. Thus, analysis of the climatic results emphasizes that in the years 1999, 2001, 2005, 2008 and recent years (2010- 2013) a significant trend of drought has been experienced in terms of all analyses. The use of drought indices in this study suggests the tensions that region has endured over a period of 30 years. Comparing these results with evaluating the trend of changes and time course of changes and modifications indicated that the greatest changes occurred in the temperature indicator and precipitation variations usually appear with a delay of up to several years after the temperature mutations in the region. Therefore, by a careful planning and consideration of the interests of all concerned and influential parties we can present a comprehensive plan for the sustainable management, and controlling and mitigating the effects of drought and climate change, in Agh Gol wetland, , to be witness of dewatering of wetlands in the coming years. Also presenting a sustainable agriculture program in accordance with the climatic conditions of the region may contribute to regional stability a lot.]]>
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Cu > Mn > Zn > Fe > Ni > Cr. Metal extractability of methods was in the order of SBET > TCLP > EDTA > SPLP > CaCl2 for Pb, Ni, Cd and SBET > EDTA > TCLP > SPLP > CaCl2 for the rest. The potential bioavailability of metals was higher than their actual bioavailability while the bioaccessibility of them was the highest. The concentrations of metals extracted by SBET were higher than those of TCLP, which was due to acidic pH and higher temperature in SBET. Although TCLP and SPLP methods are very similar, metal concentrations in TCLP were higher than SPLP. TCLP represents metal leaching under landfill conditions while SPLP simulates their release owing to precipitation which is an easier condition.
Conclusion
In this study, bioavailability, mobility and speciation of heavy metals in dredged sediments of Anzali wetland are assessed. The metal speciation and the mRAC index showed high potential adverse impacts. BRAI index using bioavailability and bioaccessibility test results represented medium and very high risks. Metal concentrations in TCLP test were lower than USEPA limits and in SPLP test were occasionally higher than standards. Results showed that metals in sediments of Anzali wetland can be up-taken by plants. Moreover, metals can leach to the underlying soil and contaminate ground water. They can also be washed due to the precipitation and re-enter to the wetland. On the other hand, sediments are not toxic and can be used for beneficial purposes. It can be concluded that unless properly managed, to deposit sediments can cause adverse effects on the environment and terrestrial organisms of Anzali wetland.]]>
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