عنوان مقاله [English]
Desertification is currently a problem in many countries of the world, including developing countries. The result of this phenomenon is the loss of renewable resources in each of these countries. One of the most important renewable sources is water, which is polluted in various ways today. Nitrate and phosphate are two important pollutants that are created by chemical fertilizers and pollute the environment, including water sources, and have harmful effects on human health. Sulfates are also another major ion found in natural waters and wastewater. There are common physical, chemical and biological methods in removing these pollutants from water sources. Due to the high cost and limited efficiency of physical and chemical methods, in recent years, suitable and inexpensive natural treatment methods such as Phytoremediation has been studied. The phytoremediation process is a natural way to purify contaminants that is very effective and inexpensive and can be performed for a long time. Due to the limited quantity and quality of water and soil resources and the need to provide food for the growing population of the country, today special attention has been paid to the production of agricultural products in soilless cultivation systems. Therefore, due to the fact that plants have different abilities in monitoring pollution, suitable plants should be used to clean polluted environments. Eucalyptus camaldulensis Dehnh. and Elaeagnus angustifolia L. plants are among the common and well-known species in Iran for planting along waterways with the aim of purifying crop water to prevent them from entering surface flows.However, as far as the comprehensive studies of the researcher in internal and international sources show, no study has been done on the removal of nitrate, phosphate and sulfate by Elm and Eucalyptus., this research can be the first research in this field to purify polluted resources in Iran.
The present study was conducted in the greenhouse of Isfahan University of Technology at a temperature of 40 degrees. In First, to study and compare phytoremediation of nitrate, phosphate and water sulfate using Eucalyptus camaldulensis Dehnh. and Elaeagnus angustifolia L. tree species. seedlings of these trees were planted in plastic pots with a cover of washed pebbles. Overall, The pots were 54 and had a volume of about 10 liters and a diameter of 12 cm. Thus, in 27 pots of Eucalyptus and 27 other species of Elaeagnus were planted. At the beginning of planting, the seedlings were impregnated with hydroponic solution (with a volume of 2 liters) and about 2 times a week, hydroponic solution was added to each pot. after establishment of plants, solutions containing nitrate, phosphate and sulfate prepared in the laboratory was added to the culture in three replications with concentrations (0,30,60 mg /l) for phosphate and sulfate and concentrations (0,50, 100 mg /l) for nitrate. Three chemicals, potassium nitrate KNO3, monosodium phosphate NaH2PO and sodium sulfate Na2SO4 , were used to prepare nitrate, phosphate and sulfate contaminants, respectively. This experiment was performed for four months in the natural resources greenhouse of Isfahan University of Technology in March 2017. The experiment was performed factorially and in the form of a completely randomized design. In order to measure the nitrate, phosphate and sulfate of the samples and evaluate the effect of phytoremediation on the uptake of these contaminants, samples of the culture medium were transferred to the laboratory every month with contaminated water. Data were collected and recorded for at least 3 months and the uptake of nitrate and phosphate in the leaves of the plant was examined by sampling and analysis in the laboratory during each month. Plant parameters were harvested every week. In this regard, the effect of different concentrations of nitrate and phosphate contaminants on some physiological factors of the plant (stem diameter, plant height, stomatal exchange and chlorophyll content) were measured. also all data were measured by statistical analysis using SAS statistical software with version 25. Finally, analysis of variance was performed by ANOVA test and mean data were compared by LSD test.
The results of the analysis of variance, for nitrate, phosphate and sulfate removal showed a significant difference at 99% level. The results of analysis of variance showed the highest percentage of removal was to Eucalyptus species with 86.26% nitrate, 95.34% phosphate and 86.8% sulfate and to Elaeagnus species with 83.72% nitrate, 88.55% phosphate and 90.73% sulfate. As a result, Eucalyptus specimens showed a higher ability to remove nitrate and phosphate pollutants and Elaeagnus species a higher ability to remove sulfate. The results also showed that the correlation and interaction of species on physiological traits (stem diameter, plant height, Chlorophyll content and stomatal exchange) was very significant due to differences in species and different concentrations of pollutants. Also, the results of mean comparison showed that no significant differences were observed between the traits of Eucalyptus and Elaeagnus species.