Study On The Effect Of Biochar On Urease Activity

Biochar is a kind of thermal decomposition product of biomass and it is a very effective way for carbon locking.This way can make the carbon lock up for several thousands of years and benefit for mitigating global climate change.Variety kinds of biomass can be used as raw materials to produce biochar;this is the basic condition to widely application biochar.Biochar has excellent physical and chemical properties and mainly is used in soil improvement,environmental restoration,animal husbandry and aquaculture.Some living organisms,such as plants,bacteria,algae,protozoa and crustaceans were used to evaluate the toxicity of biochar in existing reports.Although these organisms could reflect the toxicity of biochar at a certain extent,some of these living organisms were not the originally species in arable land,so it didn’t has a universal representation;Secondly living organism has metabolism,when they contact contaminated substances may trigger some response mechanism,it will strengthen or weaken the effect of pollutants on organisms,so it requires more auxiliary experiments to truly reflect the toxic effects of biochar.This research chooses urease as study object to evaluate biochar environmental risk.Urease also is known as urea amide hydrolase,it is the first crystalline enzymes in the world and is also the first metal enzymes contained nickel ions;it’s a milestone in the history of biochemistry.This paper chooses urease to evaluate the toxicity of biochar,except for the characteristic of urease itself,there are also as the following reasons:Urease is a kind of protein that has catalytically active,it’s sensitive to harmful substances in the environment and make the slight harmful factors apparent;Urease is the originally substance in arable land,it will foresee biochar as a soil addition may exist environmental risk;Urease has specific substrate,generally catalyzes urea hydrolysis,although some researchers found that urease can catalyzed a small number of urea derivatives hydrolysis,it’s catalytic activity will greatly reduce,so it can effectively eliminate interference in the reaction system.In the study of the activity of urease affected by biochar,we change the composition of the reaction system,compare the difference between the different reaction system to study the effects of sterilized soil and biochar on the activity of urease.The results showed that both biochar and sterilized soil can adsorbed NH4+,the mechanism is not due to surface area and electrostatic interactions,but because of oxygen-containing functional groups contained in biochar provide negative potential point for adsorption of NH4+.Since the biochar and sterilized soil can adsorb NH4+,when study biochar affects the activity of urease,related correction experiments need to be done.In the experiments of biochar affect the activity of urease,researchers find that oxygen-containing functional groups in biochar may oxidize sulfhydryl groups in urease and lead the activity of urease changing;Researchers detect heavy metals and polycyclic aromatic hydrocarbons in biochar,both of these two hazardous substances are at the level of μg/L,the content of hazardous substances are at the same level to the measured values of other researchers.The higher levels of these harmful substances contained,the activity of urease is lower,but in the certain range and time,urease has a certain tolerance for these hazardous substances.The mechanism of heavy metal to decrease the activity of urease is that heavy metal combine with sulfhydryl located in the activity of urease sites,it’s equal to form metal-sulfide equivalent;the mechanism of polycyclic aromatic hydrocarbons doesn’t have exact conclusion,its need for more in-depth study.Environmental persistence radical also is detected in biochar.The content of environmental persistence radical increase with the rise of the thermal decomposition temperature,although the content of environmental persistence radical seems have not relationship with the phenomenon has been found in impact of biochar on the activity of urease,it shouldn’t be ignored in the application of biochar,it’s a potential environmental risk.Biochar almost shows excellent characters and results in all aspects,making people give more and more hope for biochar application,at the same time,it’s very easy to overlook biochar may cause potential environmental risks.it’s necessary to make a comprehensive and objective evaluation to the environmental risks of biochar,which can avoid a lot of unpredictable consequences.When people have a comprehensive and objective understanding of biochar,it will make people take appropriate measures to deal with harmful substances contained in biochar in the future application of biochar,so that it can make the advantages of biochar get maximum play.This study hopes to study the impact of biochar on the activity of urease to accumulated valuable reference for making a comprehensive and objective evaluation to the environmental risks of biochar.