مطالعه ریزساختاری و تغییرات نفوذپذیری خاک‌های رسی در حضور کودهای فسفاته

ﻧﻴﺎز ﺑﻪ ﺗﻮﻟﻴﺪ ﺑﻴﺸﺘﺮ ﻣﺤﺼﻮﻻت ﻛﺸﺎورزی در واﺣﺪ ﺳﻄﺢ ﻣﻮﺟﺐ اﻓﺰاﻳﺶ اﺳﺘﻔﺎده از ﻛﻮدﻫﺎی شیمیایی و ﺳﺎﻳﺮ ﻋﻮاﻣﻞ ﺧﻄﺮزا ﺑﺮای ﻣﺤﻴﻂ زﻳﺴﺖ ﺷﺪه اﺳﺖ. از ﺳﻮی دﻳﮕﺮ اﺳﺘﻔﺎده از ﻛﻮدﻫﺎی شیمیایی ﻣﻮﺟﺐ ﺗﻐﻴﻴﺮ ﺳﺎﺧﺘﺎر و وﻳﮋﮔﻲﻫﺎی ژﺋﻮﺗﻜﻨﻴﻜﻲ ﺧﺎک ﻣﻲﺷﻮد و اﻳﻦ اﻣﺮ ﻣﻲﺗﻮاﻧﺪ در اﻓﺰاﻳﺶ آﻟﻮدﮔﻲﻫﺎی ﺳﻄﺤﻲ و زﻳﺮزﻣﻴﻨﻲ ﻣﻮﺛﺮ ﺑﺎﺷﺪ. ﺑﺮ اﻳﻦ اﺳﺎس ﻫﺪف اﻳﻦ ﭘﮋوﻫﺶ ﻣﻄﺎﻟﻌﻪ ﺗﻐﻴﻴﺮات ﻧﻔﻮذﭘﺬﻳﺮی و ﺗﻐﻴﻴﺮات ﺳﺎﺧﺘﺎر و رﻳﺨﺖﺷﻨﺎﺳﻲ ﺧﺎکﻫﺎی رﺳﻲ در اﻧﺪرﻛﻨﺶ ﺑﺎ ﻛﻮدﻫﺎی شیمیایی ﻓﺴﻔﺎﺗﻪ اﺳﺖ. در اﻳﻦ راﺳﺘﺎ ﺑﺎ اﻧﺠﺎم ﻳﻜﺴﺮی آزﻣﺎﻳﺶﻫﺎی ژﺋﻮﺗﻜﻨﻴﻜﻲ و ژﺋﻮﺗﻜﻨﻴﻚ زﻳﺴﺖﻣﺤﻴﻄﻲ، ﻓﺮاﻳﻨﺪ اﻧﺪرﻛﻨﺶ ﻧﻤﻮﻧﻪ رﺳﻲ ﺑﻨﺘﻮﻧﻴﺖ ﺑﺎ ﻛﻮدﻫﺎی شیمیایی ﻓﺴﻔﺎﺗﻪ ﻣﻮرد ﻣﻄﺎﻟﻌﻪ ﻗﺮار ﮔﺮﻓﺘﻪ اﺳﺖ. ﺑﺮرﺳﻲ ﺗﻐﻴﻴﺮات ﺿﺮﻳﺐ ﻧﻔﻮذﭘﺬﻳﺮی، رﺳﻮب، وﻳﮋﮔﻲﻫﺎی ﺧﻤﻴﺮی ﺧﺎک، ﺗﻐﻴﻴﺮات ph ﻣﺤﻴﻂ، ﻧﺘﺎﻳﺞ رﻳﺰﺳﺎﺧﺘﺎری ﭘﺮاش اﺷﻌﻪ اﻳﻜﺲ xrd و ﺗﺼﺎوﻳﺮ ﻣﻴﻜﺮوﺳﻜﻮپ اﻟﻜﺘﺮوﻧﻲ ﭘﻮﻳﺸﻲ sem ﻧﺸﺎن ﻣﻲدﻫﺪ ﻛﻪ ﺣﻀﻮر ﻛﻮدﻫﺎی ﻓﺴﻔﺎﺗﻪ ﻣﻮﺟﺐ ﺗﻐﻴﻴﺮ ﺳﺎﺧﺘﺎر ﺧﺎک رﺳﻲ ﺷﺪه اﺳﺖ. ﺑﺮ اﺳﺎس ﻧﺘﺎﻳﺞ اﻳﻦ ﭘﮋوﻫﺶ ﭼﮕﻮﻧﮕﻲ ﻗﺮارﮔﻴﺮی ﺳﺎﺧﺘﺎر و اﺑﻌﺎد ﺻﻔﺤﺎت رﺳﻲ ﺑﻪ ﺷﺪت ﺗﺤﺖ ﺗﺄﺛﻴﺮ ﻣﻴﺰان ﻛﻮدﻫﺎی ﻓﺴﻔﺎﺗﻪ اﺳﺖ. ﻫﻤﭽﻨﻴﻦ ﺣﻀﻮر ﻛﻮدﻫﺎی ﻓﺴﻔﺎﺗﻪ ﻣﻮﺟﺐ ﻛﺎﻫﺶ ﺷﺪت ﻗﻠﻪ اﺻﻠﻲ ﻛﺎﻧﻲ رﺳﻲ ﻣﻮﻧﺖﻣﻮرﻳﻠﻮﻧﻴﺖ و اﻓﺰاﻳﺶ ﺿﺮﻳﺐ ﻧﻔﻮذﭘﺬﻳﺮی ﺧﺎک ﻣﻲﺷﻮد ﺑﻪ ﻧﺤﻮی ﻛﻪ اﻓﺰاﻳﺶ ﺣﺪود 0/5 ﺳﻮﭘﺮﻓﺴﻔﺎت ﺗﺮﻳﭙﻞ ﺣﺪ رواﻧﻲ ﻧﻤﻮﻧﻪ ﺑﻨﺘﻮﻧﻴﺖ را 27 ﻛﺎﻫﺶ داده و ﺳﺒﺐ اﻓﺰاﻳﺶ ﺿﺮﻳﺐ ﻧﻔﻮذﭘﺬﻳﺮی ﺧﺎک ﺑﻪ ﻣﻴﺰان ﺣﺪود 100 ﺑﺮاﺑﺮ ﺷﺪه اﺳﺖ.

microstructural study and permeability variations of clayey soils at the presence of phosphate fertilizers

in the recent years the use of phosphate fertilizer has been increased. on the other hand, the use of phosphate fertilizer causes change in micro-structure and geotechnical properties of clayey soils. this may raise the risk for groundwater contamination. the main objective of this paper is to study the permeability and microstructural change of clayey soils after interaction with phosphate fertilizer. to achieve the above mentioned objective, series of geo-environmental engineering experiments was performed and the process of interaction of bentonite with phosphate fertilizer is studied. the evaluation of permeability variations, sedimentation tests, plasticity properties, soil ph variations and results of xrd and sem experiments show that the presence of phosphate fertilizer changes the clay soil microstructure. based on the results of this study phosphate fertilizer causes a reduction on the quantity of intensity of basal spacing of montmorillonite. consequently the permeability might increases around1000 times at the presence of 10 percent phosphate fertilizer.