3889

3672

كارشناسي ارشد

خاك شناسي

اصفهان :دانشگاه صنعتي اصفهان ،دانشكده كشاورزي

1386

سيزده، 106،[II]ص: مصور، جدول، نمودار

ص، ع به: فارسي و انگليسي

فرشيد نوربخش

امير حسين خوشگفتارمنش

8/2/87

نفيسه نيلي، مهران شيرواني

مهندسي كشاورزي

ID3672

به فارسي و انگليسي: قابل روئيت در نسخه ديجيتال

Abstract Protection of soils against contamination is a major principle of long runproductivity and sustainable agriculture Heavy metals including Cd negativelyinfluence the soil community structure and microbial activities and hence affect soilhealth Soil enzyme activities have been frequently used as soil bio indicators of soilquality Phosphatases play a vital role in P mineralization and consequently in plantnutrition The enzymes are also adversely affected by salinity Ecological Dose 50 ED50 the concentration that results in a 50 reduction in a biological function hasbeen used as a quantitative index of toxicity The objective of this study was to studythe additive effects of salinity on Cd toxicity on soil alkaline phosphatase In order tostudy the effects of salinity on ED50 and Inhibition percent of Cd on soil alkalinephosphatase two contrasting soils were sampled Soil samples include a calcareous Shervedan and an acidic Langroud soil Soils were air dried passed through a 2 mmsieve and were artificially salinized by NaCl to achieve electrical conductivities 13 18and 28 dS m 1 The soils then were contaminated with varying concentrations of Cd 0 3 10 50 100 300 700 1000 and 5000 mg Cd kg Soils were incubated at 25 C and50 water holding capacity for 3 and 60 days and at the end of the incubation period soil alkaline phosphatase was determined by determining p nitrophenol released Furthermore NH4NO3 extractable Cd was also measured by atomic adsorptionspectroscopy Two kinetic models models 1 and 2 and a sigmoid dose response curve model 3 were fitted to the data Results indicated that Langroud soil had significantlygreater Cd concentrations Salinity enhanced the extractable Cd concentration Longerincubation period increased the extractable Cd concentration and resulted in loweralkaline phosphatase activity The enzyme activity significantly decreased as the appliedCd concentration increased A more pronounced reduction in the enzyme activity wasobserved as salinity increased In Shervedan soil kinetic based models 1 and 2 weresatisfactory for 60 and 3 days of incubation respectively The ED50 values calculated bymodels 2 and 3 were decreased as the salinity increased In lordegan soils neither of themodels could calculate ED50 values The inhibition percent was consistently greater inLangroud soil and enhanced in the both soils as soils were salinized Overall we foundout that Cd ia a limiting factor for P mineralization in soils and salinity can enhance thetoxicity of Cd on alkaline phosphatase This finding supports the hypothesis suggestingthat salinity additively increase the Cd toxicity on soil alkaline phosphatase

فرشيد نوربخش

امير حسين خوشگفتارمنش

نفيسه نيلي، مهران شيرواني