Black Soil Ecological Effects Of Zero-valent Iron With Different Particle Sizes And Its Effect On Soybean Seedling Growth

In recent years,as a new functional material,nanometer zero-valent iron has been applied in the field of environmental pollution control.In addition,black soil,as an extremely precious natural resource,plays an important role in ensuring China's food security.However,as the ecological effects of nanometer zero ferric iron on black soil are still unknown,it is impossible to determine whether nanometer zero ferric iron can be used in black soil pollution control.Therefore,this research intends to select two different particle size of nanometer zero-valent iron,focuses on the above two kinds of different levels of dosing nanometer zero-valent iron in typical black soil physical and chemical properties,the key enzyme activity,microbial biomass crops as well as the typical black soil(soybean)the influence law of growth and physiological characteristics,so as to nanometer zero-valent iron in the black soil pollution prevention in the field of security used to provide the necessary reference basis.The main research results are summarized as follows:(1)To study the effects of two kinds of nano-sized zero-valent iron(n ZVI-A,250 nm and n ZVI-B,100 nm)at different addition levels on soil p H and nutrient content.The results showed that the content of organic matter,total nitrogen,total phosphorus and available nitrogen in the black soil was not significantly affected by the above two kinds of nano-sized zero-valent iron at the addition level of 100~500 mg/kg in 21 days.With the increase of the application concentration of nanometer zero-valent iron(100 ~ 500 mg/kg)and the increase of culture time,the inhibition effect of n ZVI-B on p H and available phosphorus content of black soil was gradually enhanced,which was stronger than that of n ZVI-A treatment group.On the 21 st day of culture,soil p H and available phosphorus in the n ZVI-B treatment group with the dosage of 500 mg/kg were respectively(5.44 mg/kg and 13.61 mg/kg),4.4% and 45.85% lower than those in the blank treatment group(0 mg/kg),reaching a significant difference.n ZVI-A at the same addition level has no significant effect on the p H value of black soil,while n ZVI-A has A certain promoting effect on the content of available phosphorus in black soil.At 21 days,the available phosphorus content of black soil in the treatment group with n ZVI-A dosage of 300 mg/kg and 500 mg/kg increased by5.95% and 11.71%,respectively,compared with the corresponding control treatment.(2)The effects of two kinds of nano-sized zero-valent iron at different addition levels on biomass carbon,nitrogen and phosphorus content of black soil microorganisms were investigated.The effects of two kinds of nanometer zero-valent iron on the contents of carbon,nitrogen andphosphorus in black soil showed obvious "time-effect" and "dose-effect" relations.At the end of the experiment(21 days),n ZVI-A dosing quantity is 500 mg/kg treatment group of soil microbial biomass carbon,nitrogen,phosphorus and controlled processing phase was reduced by 32.08%,20.19% and 11.67%,respectively,and adding the same level of n ZVI-B treatment group after 21 days of training,the soil microbial biomass carbon,nitrogen,phosphorus content than control treatment phase was reduced by 66.81%,21.30% and 32.07% respectively.The above results indicate that the influence of n ZVI-B on the content of carbon,nitrogen and phosphorus in black soil microbial biomass is more obvious than that of n ZVI-A.(3)Two kinds of different levels of dosing of nanometer zero-valent iron adding black soil under the condition of typical soil enzyme activity,urease,sucrase and dehydrogenase response regularity results show that the n ZVI-B on black soil sucrase and dehydrogenase all have inhibition,dosing quantity n ZVI-B in 300 mg/kg and 500mg/kg processing soil to cultivate 21 d of invertase activity inhibition rate was 13.69%,10.89%,respectively.Compared with the blank treatment in the same period,it was significantly reduced(p < 0.05).The activity of dehydrogenase in black soil treated with n ZVI-B(1-21d)was significantly inhibited on the 21 th day after the addition of 300 mg/kg of black soil,and the enzyme activity inhibition rate was 20.83%.When the addition increased to 500 mg/kg on the 14 th day,the enzyme activity inhibition rate was 9.86%and 30.66%,and the inhibition increased with the extension of culture time.However,n ZVI-A only had A strong inhibitory effect on dehydrogenase activity.The inhibition effect appeared on day 21,and the inhibition rate of enzyme activity was 2.39%,which was significantly lower than the blank group(p < 0.05).NZVI-A and n ZVI-B had no significant effect on 1-21 d black soil urease activity.(4)It was found that the addition of nanometer zero-valent iron into the soil could also exert some stress on the growth and physiological indexes of soybean.After 21 d culture,the inhibition The inhibition rate of 500mg/kg n ZVI-B on root weight of soybean seedlings reached 37.25%,which was significantly different from the blank group(p < 0.05).while the above addition level of n ZVI-B had no significant effect on soybean plant height,plant weight and root length.The addition of n ZVI-A in the range of 100-500 mg/kg promoted the growth of soybean plants,which were 0.22 cm,1.90 cm and 1.20 cm higher than the blank.In addition,500 mg/kg of n ZVI-B reduced the content of chlorophyll b in soybean leaves by 26.86% compared with the control treatment,while the same level of n ZVI-A had no significant effect on the content of chlorophyll a,chlorophyll b and carotenoids in soybean leaves.The increase of SOD and proline content means that the concentration of reactive oxygen species is increased,indicating that high concentration(300-500 mg/kg)of n ZVI induces oxidative stress reaction in soybean.