بررسي فلزات سنگين چسبيده به رسوبات معلق رواناب در حوزه آبخيز شهري بجنورد

Assessment of heavy metals absorbed to suspended solids in runoff of Bojnourd urban watershed

ارزﯾﺎﺑﯽ ﻓﻠﺰات ﭼﺴﺒﯿﺪه ﺑﻪ ﻣﻮاد ﻣﻌﻠﻖ ﺳﯿﻼب ﻫﺎي ﺷﻬﺮي، ﺑﻪ ﻣﺪﯾﺮان اﺟﺎزه ﻣﯽ دﻫﺪ ﺗﺎ اﻗﺪاﻣﺎﺗﯽ در راﺳﺘﺎي ﺑﻬﺒﻮد ﮐﯿﻔﯿﺖ ﻣﺤﯿﻂ ﺷﻬﺮي اﻧﺠﺎم دﻫﻨﺪ. در اﯾﻦ ﭘﮋوﻫﺶ، ﺑﻪ ﺑﺮرﺳﯽ ﺗﻐﯿﯿﺮات ﻣﻘﺪار ﻏﻠﻈﺖ ﻓﻠﺰات ﺳﻨﮕﯿﻦ ﺳﺮب، روي و ﻣﺲ ﻣﻮﺟﻮد در ﻣﻮاد ﻣﻌﻠﻖ رواﻧﺎب ﻫﺎ در ﺣﻮزه آﺑﺨﯿﺰ ﺷﻬﺮي ﺑﺠﻨﻮرد در دو ﻓﺼﻞ ﭘﺎﯾﯿﺰ و ﺑﻬﺎر ﭘﺮداﺧﺘﻪ ﺷﺪه اﺳﺖ. ﺑﻪ اﯾﻦ ﻣﻨﻈﻮر، ﺗﻌﺪاد 52 ﻧﻤﻮﻧﻪ رواﻧﺎب ﺗﻬﯿﻪ ﺷﺪ. ﭘﺲ از آﻣﺎده ﺳﺎزي ﻧﻤﻮﻧﻪ ﻫﺎ، ﺗﻔﮑﯿﮏ رﺳﻮﺑﺎت ﻣﻌﻠﻖ ﺑﺎ اﺳﺘﻔﺎده از ﮐﺎﻏﺬ ﺻﺎﻓﯽ واﺗﻤﻦ و ﭘﺲ از ﺗﻮزﯾﻦ ﻣﻘﺪار رﺳﻮﺑﺎت ﻣﻮﺟﻮد در رواﻧﺎب، ﺑﺎ اﺳﺘﻔﺎده از دﺳﺘﮕﺎه ﺟﺬب اﺗﻤﯽ، ﻣﻘﺪار ﻓﻠﺰات ﺳﻨﮕﯿﻦ ﻣﺤﻠﻮل در رواﻧﺎب و ﻓﻠﺰات ﺳﻨﮕﯿﻦ ﭼﺴﺒﯿﺪه ﺑﻪ رﺳﻮﺑﺎت ﻣﻌﻠﻖ ﺑﺮ ﺣﺴﺐ ppb اﻧﺪازه ﮔﯿﺮي ﺷﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﻣﻘﺪار وزﻧﯽ رﺳﻮﺑﺎت ﻣﻌﻠﻖ در ﻓﺼﻞ ﺑﻬﺎر ﺑﯿﺸﺘﺮ از ﭘﺎﯾﯿﺰ اﺳﺖ. ﻫﻤﭽﻨﯿﻦ، ﻧﺘﺎﯾﺞ ﺣﺎﮐﯽ از آن اﺳﺖ ﮐﻪ ﺑﯿﺸﯿﻨﻪ ﻏﻠﻈﺖ ﻓﻠﺰات ﺳﻨﮕﯿﻦ ﻏﯿﺮﻣﺤﻠﻮل و ﭼﺴﺒﯿﺪه ﺑﻪ رﺳﻮﺑﺎت ﺑﯿﺸﺘﺮ از ﻓﻠﺰات ﺳﻨﮕﯿﻦ ﻣﺤﻠﻮل در رواﻧﺎب اﺳﺖ. از ﺳﻮﯾﯽ دﯾﮕﺮ، ﻧﺘﺎﯾﺞ ﺑﯿﺎﻧﮕﺮ آن اﺳﺖ ﮐﻪ ﺑﯿﺸﯿﻨﻪ ﻣﯿﺎﻧﮕﯿﻦ ﻏﻠﻈﺖ ﻓﻠﺰات روي و ﻣﺲ ﺑﻪ ﺟﺰ ﺳﺮب ﭼﺴﺒﯿﺪه ﺑﻪ رﺳﻮﺑﺎت در ﻓﺼﻞ ﺑﻬﺎر ﺑﯿﺸﺘﺮ از ﭘﺎﯾﯿﺰ اﺳﺖ و از ﻧﻈﺮ ﻣﮑﺎﻧﯽ ﻏﻠﻈﺖ ﻓﻠﺰات روي و ﻣﺲ در ﻧﻤﻮﻧﻪ ﻫﺎي رﺳﻮﺑﺎت ﻣﻌﻠﻖ رواﻧﺎب ﻣﺴﯿﻞ ﺻﻨﺪل آﺑﺎد )FC3S( ﺑﯿﺸﺘﺮ ﺑﻮده اﺳﺖ، اﯾﻦ در ﺣﺎﻟﯽ اﺳﺖ ﮐﻪ در ﺧﺼﻮص ﻓﻠﺰ ﺳﺮب در ﻧﻤﻮﻧﻪ ﻫﺎي ﻣﻌﺎﺑﺮ و ﺷﺒﮑﻪ اﻧﻬﺎر )FB2S( ﻣﻘﺪار ﻏﻠﻈﺖ ﺑﯿﺸﺘﺮ ﺑﻮده اﺳﺖ. ﻟﮑﻦ ﺗﻔﺎوت ﻣﮑﺎﻧﯽ داده ﻫﺎ ﺑﺮاي ﻓﻠﺰات ﺳﻨﮕﯿﻦ ﭼﺴﺒﯿﺪه ﺑﻪ رﺳﻮﺑﺎت ﻣﻌﻠﻖ از ﻧﻈﺮ آﻣﺎري ﻣﻌﻨﯽ دار ﻧﯿﺴﺖ. ﻫﻤﭽﻨﯿﻦ، ﻧﺘﺎﯾﺞ آزﻣﻮن ﻫﻤﺒﺴﺘﮕﯽ ﭘﯿﺮﺳﻮن ﺣﺎﮐﯽ از آن اﺳﺖ ﮐﻪ ﻫﻤﺒﺴﺘﮕﯽ ﻣﺜﺒﺖ اﻣﺎ ﭘﺎﯾﯿﻨﯽ ﺑﯿﻦ ﺳﺮب و روي )0/166=r( در ﻓﺼﻞ ﭘﺎﯾﯿﺰ و ﺑﯿﻦ ﺳﺮب و ﻣﺲ )0/271=r( در ﻓﺼﻞ ﺑﻬﺎر ﺑﺮﻗﺮار اﺳﺖ. ﻣﻌﻨﯽ داري اﯾﻦ ﻫﻤﺒﺴﺘﮕﯽ ﺑﺎ اﺳﺘﻔﺎده از ﺗﺤﻠﯿﻞ ﺧﻮﺷﻪ اي ﺑﻪ روش ﺳﻠﺴﻠﻪ ﻣﺮاﺗﺒﯽ ﻣﻮرد ﺗﺎﯾﯿﺪ ﻗﺮار ﮔﺮﻓﺖ.

Assessment of metals absorbed to suspended solids in urban floods, allows managers to take measures to improve the quality of the urban environment. This article examines the changes in the concentration of heavy metals such as lead, zinc and copper in suspended load of runoff from the Bojnourd urban watershed in autumn and spring seasons. For this reason, 52 samples were collected. After preparing the samples, separation of suspended sediment using the Whatman filter paper and then weighing the amount of sediment in runoff, using atomic absorption, the amount of heavy metals dissolved in runoff and heavy metals absorbed to suspended solids in runoff were measured in terms of ppb. The results showed that the amount of suspended sediment weight is higher in spring than autumn. Results indicated that the maximum concentration of insoluble heavy metals and attached to sediments is more than soluble heavy metals in runoff. On the other hand, the results revealed that the mean maximum concentration of zinc and copper, except lead attached to sediments, is higher in the spring than autumn and the spatial concentration of zinc and copper in samples of runoff suspended sediments from Sandalabad Stream (FC3S) is higher. While on the lead, concentration for the samples taken from the runoff pathways and drainage network (FB2S) was higher. However, the difference in location of data for heavy metals absorbed to suspended sediments is not statistically significant. The Pearson correlation test results showed that there is a positive but low correlation between lead and zinc (r =0.166) in the autumn and the lead and copper (r=0.271) in the spring. Significance of this correlation is certified using hierarchical cluster analysis method.