A Comparative Study Of Kinetic And Thermodynamic Characteristics Of Soil Enzymes In Songnen Petroleum Pollution And Servely Saline-Alkalized Grassland

The ecological environment of Songnen grassland is deteriorating day by day,it is of great significance to improve the degraded grassland with petroleum pollution and salt-alkali stress to maintain and promote the regional development.Soil enzymes are biocatalysts that produce a specific biochemical reaction in soil,and can indicate the biological reaction process of petroleum pollution and severe saline-alkalized grassland.Soil enzyme kinetics and thermodynamic parameters can indicate the compactness between petroleum pollution and saline-alkalized soil enzyme substrate complexes,the reaction process and energy state of the action process.The changes of soil enzymes in petroleum pollution and severe saline-alkalized grassland were explained from the mechanism of enzyme-induced reaction.Therefore,study the changes of soil catalase,polyphenol oxidase,alkaline phosphatase,invertase and urease activity,kinetics and thermodynamics in different temperature of Songnen petroleum pollution and severe saline-alkalized grassland,and compared that of the two habitats.To explore the characteristics of soil enzyme reaction after phytoremediation and heating up of petroleum pollution and severe saline-alkalized grassland,and to reveal the mechanism of soil enzyme activity change,in order to provide theoretical basis for restoring the degradation of Songnen petroleum pollution and severe saline-alkalized grassland.The following results are obtained from the study:1.The activities of five kinds of soil enzymes varied with the change of temperature and substrate concentration in petroleum pollution?1 km,5 km,15 km bare land and the restoration land of Leymus chinensis from petroleum working area?and different plant growth?natural grassland,the restoration land of Leymus chinensis,Avena sativa,and Medicago sativa?of severe saline-alkalized grassland.With the increase of temperature,the activities of five kinds of soil enzymes increased gradually.In petroleum pollution grassland,The activities of soil catalase,polyphenol oxidase,alkaline phosphatase and urease increased gradually with the increase of substrate concentration,soil invertase activity increased gradually at 35?and 45?,but decreased gradually at 15?and 25?.In severe saline-alkalized grassland,the activities of soil catalase,polyphenol oxidase and alkaline phosphatase increased gradually with the increase of substrate concentration,while the soil invertase activity and urease increased or decreased with the increase of substrate concentration.2.Soil enzyme activities are different in two habitats with petroleum pollution and severe saline-alkalized grassland.The activity of soil catalase showed that 1 km bare land and 1 km Leymus chinensis repaired land from the petroleum working area was significantly higher than that in other petroleum pollution grasslands and severe saline-alkalized grasslands.The activity of soil polyphenol oxidase showed that 5 km bare land from the petroleum working area was significantly higher than that in other petroleum pollution grasslands and severe saline-alkalized grasslands.The activities of soil alkaline phosphatase,invertase and urease showed that saline-alkalized grassland of different plants and petroleum pollution Leymus chinensis repaired lands were significantly higher than petroleum pollution bare land.3.The changes of five kinds of soil enzyme kinetic parameters of K_m?Michaelis constant?,V_max?maximum rate of enzymatic reaction?and V_max/K_m?catalytic efficiency?with the change of temperature in petroleum pollution and severe saline-alkalized grassland.In the petroleum pollution grasslands,with the increase of temperature,the K_m valuesof five kinds of soil enzymes changed irregularly.The V_max values of the five soil kinds of enzymes increased gradually.The Vmax/Km value of soil catalase decreased or decreased at first and then increased,and the Vmax/Km values of soil polyphenol oxidase,alkaline phosphatase,invertase and urease all increased gradually.In severe saline-alkalized grasslands,with the increase of temperature,the K_m value of soil catalase increased gradually,while the K_m value of soil polyphenol oxidase,alkaline phosphatase,invertase and urease decreased gradually,and the Vmax value of five kinds of soil enzymes increased gradually.The V_max/K_m value of soil catalase decreased at first and then increased,while the V_max/K_m value of soil polyphenol oxidase,alkaline phosphatase,invertase and urease all increased gradually.4.The soil enzyme kinetic parameters of K_m,V_max and V_max/K_m in petroleum pollution and severe saline-alkalized grassland are different.The K_m value of soil catalase showed that the natural grassland,the restoration land of Leymus chinensis,Avena sativa and Medicago sativa were higher than petroleum polluted grassland.The Vmax value showed that in 1 km Leymus chinensis repaired land from the petroleum working area was significantly higher than that in other petroleum pollution grasslands and severe saline-alkalized grasslands.The V_max/K_m value showed that 1 km bare land and 1 km Leymus chinensis repaired land from the petroleum working area was significantly higher than that in other petroleum pollution grasslands and severe saline-alkalized grasslands.The K_m value of soil polyphenol oxidase changed irregularly.The Vmax value showed that 5 km bare land from the petroleum working area?1 km and 15 km bare land and Leymus chinensis repaired land from the petroleum working area?saline-alkalized natural bare land?5 km Leymus chinensis repaired land from the petroleum working area?natural grassland and the restoration land of Leymus chinensis,Avena sativa and Medicago sativa.The K_m value of soil polyphenol oxidase,alkaline phosphatase,invertase changed irregularly,the Vmax and Vmax/Km value showed that saline-alkalized grassland of different plants higher than petroleum pollution glasslang,and petroleum pollution Leymus chinensis repaired lands were higher than bare land.5.The changes of five kinds of soil enzyme thermodynamic parameters of?G?activation free energy?,?H?activation enthalpy?and?S?activation entropy?,Q₁₀?temperature coefficie?,E_a?activation energy?with the change of temperature in petroleum pollution and severe saline-alkalized grassland.With the increase of temperature,the five kinds of soil enzymes Q₁₀,?H,?S decreased gradually,and?G increased gradually.6.The soil enzyme thermodynamic parameters of Q₁₀,?H,?S,E_a in petroleum pollution and severe saline-alkalized grassland are different,?G had no significant difference.Soil catalase?H,?S,Ea changed irregularly;Soil polyphenol oxidase?H,?S,Ea showed that in petroleum pollution grassland was lower than that in severe saline-alkalized grassland?except the restoration land of Leymus chinensis?;Soil alkaline phosphatase,invertase,urease?H,?S,Ea showed that saline-alkalized grassland of different plants smaller than petroleum pollution glasslang,and petroleum pollution Leymus chinensis repaired lands were smaller than bare land.