Study On The Effect Of Biochar-nps On Wheat Growth

Biochar,which is a new energy material and carbon-rich solid waste material derived from the pyrolysis of agricultural and forest residual biomass has become a hot cause for concern throughout the world.It has been wildly applied in maintaining soil ecosystem balance and adsorption of water contaminants such as heavy metals and consequently reducing their bioavailability due to its greater pore structure and the larger surface area.However,smaller particles of carbon in the nano or micro range are formed during biochar synthesis and at present,the researches on the growth of crop by biochar are largly focused on the conventional size effect,while a few are on the nanoscale of biochar behavior,and their effects combined with common soil pollutants such as heavy metals.Thus,in the present study,we prepared manure biochars.Hydroponic experiment and the plant experiment were conducted to study the effects and mechanisms of biochar-NPs and their combination with Pb and Cr?shortened as Pb+Cr?on wheat seedlings germination,growth and antioxidase activities?SOD,POD,CAT?.Physical and chemical properties were examined as well.Main research results are as follows:?1?As seen from the condition of hydroponic culture,it was observed that both root and shoot length were not obviously affected by biochar-NPs at the lower concentration range of 10 to 100 mg L^-11 when comparing to the control?P>0.05?.In contrast,high concentration of biochar-NPs(150-300mg L^-1)significantly inhibited the growth of plant by causing plant oxidative damage and defensive reactions,as a result,the dry weight of wheat was reduced.?2?Under the soil culture conditions,the application of 1%and 2%biochar-NPs increased the dry weight of wheat and promoted the growth of wheat while significantly reducing the superoxide dismutase and peroxidase activity,soluble protein content and malondialdehyde content,at the same time catalase activity was increased.5%biochar-NPs on wheat seedlings obtained the opposite results,the main reason for this may be that high concentration of biochar-NPs easily conglutinate on plant roots,affecting root uptake of moisture and nutrients,and it may also be that active sites on the surface of high concentrations of BC-NPs cause oxidative damage to plants.?3?Under the contaminated soil culture conditions,the biodegradability of lead and chromium in the soils was significantly reduced by 1%-2%biochar-NPs.Results showed that SOD,POD which existed in wheat leaf was significantly decreased,while CAT showed the adversary tendency.The corresponding dry weight of plant,chlorophyll and soluble protein content was relatively high.In addition the effect of 5%biochar-NPs may be weaker than that of 1%.It was speculated that high-dose BC-NPs may promote the mineralization of soil organic matter,reducing the adsorption of heavy metals,and may release their inherent heavy metals,eventually inhibiting the growth of the plant.