Effects Of Biomass Carbon On Soil Contaminated By Heavy Metals Under Simulated Acid Rain Conditions

Acid rain is one of the most serious environmental pollution problems in the world.All countries suffer from acid rain,especially In China.The development of heavy industry and the emission of chemical and automobile exhaust aggravate the serious problem.With the development of metallurgy and electroplating industries,heavy metal pollution is becoming more and more serious,crop loss,harm to human health and social environment.The synergistic effect of acid rain and heavy metals reduces soil pH and soil fertility,so it is of great practical significance to find a safe,environmentally friendly and convenient way to improve soil.Biomass charcoal has a large surface area,strong adsorption capacity,abundant surface functional groups and other factors,and has been widely used as soil improver in recent years.This study based on the national bureau of forestry and grassland of the Yangtze river delta,forest ecosystems positioning research station(zhenjiang jurong shu forest farm),with German oak forest as the research object,take forests,soil column leaching of soil,according to the natural properties of the soil configuration add heavy metal copper,zinc,indoor simulated acid rain leaching experiment,the simulation in different acidity(pH3.5 pH4.5 pH5.6,pH7.0)acid rain and different biomass charcoal to add(add(CK),2% 0% biomass charcoal(BC-2),5% biomass charcoal(BC-5),10% more biomass charcoal(BC-10))processing,Analysis of simulated acid rain on leaching liquid pH,conductivity,the content of copper and zinc,soil pH,soil nutrient elements(n,p,k),soil enzymes(urease,acid phosphatase)and the content of soil heavy metals(copper and zinc effectively)effectively,the influence of reveal that under simulated acid rain stress biomass charcoal to add copper and zinc contaminated soil leaching liquid,the effect of soil physical and chemical properties and soil enzyme activity,the main results were as follows:(1)The addition of biomass charcoal can effectively improve the pH of leaching solution and soil under simulated acid rain leaching.The pH of the leacheate increased by 0.13～1.05,and the pH of the soil increased by-8.83% ～ 21.84%(pH3.5),10.71% ～ 35.94%(pH45),26.44% ～ 42.71%(pH5.6),36.67% ～ 62.13%(pH7.0).In the early leaching,the pH of the leacheate and the soil increased rapidly,and the pH of the later period remained basically stable.The addition of biomass carbon brings a large number of alkaline ions and compounds to neutralize and other reactions with H+ in acid rain,which has an obvious effect on the buffer capacity of acid rain,reducing the acidity of leachate and soil,increasing pH,and effectively preventing soil acidification.(2)The addition of biomass charcoal increases the conductivity of leachate at the beginning,then the conductivity of leachate decreases rapidly until it tends to 0.Biomass carbon addition,brought a lot of potassium,calcium,sodium,and other alkaline salt ions,under simulated acid rain eluviation,for alkaline ion free and colloid ionization provides a good environment,the electrical conductivity of lixiviant peak after the first leaching time,as the reaction progresses,biomass charcoal alkaline weakening,weakening and acid,base ions to form complex or colloid,cause the ions in the solution,after 4 ～ 5 times leaching,leaching liquid conductivity to converge to zero.(3)With the increase of biomass charcoal,the leaching loss of Cu and Zn in contaminated soil was increased to different degrees.Increased 26.35% ～ 105.32%,the leaching amount of how many relationships with various treatments for: pH3.5 > pH4.5 > pH5.6 > pH7.0,biomass carbon addition,under the condition of simulated acid rain eluviation,played a large role,especially biomass charcoal(BC-5)added 5%,10%,biomass carbon add(BC-10),can greatly increase the leaching amount of Cu and zinc,effectively alleviate the pressure of the soil heavy metal pollution.(4)Simulated acid rain,especially when the acidity is high,has a negative impact on the content of copper and zinc in soil,soil enzyme activity,soil fertility and bioavailability,but the addition of biomass charcoal,especially the addition of 10% biochar,significantly increases the physical and chemical properties and biological activity of soil.Soil fertility,available potassium,available phosphorus and alkali-hydrolyzed nitrogen were increased by 9.60%～72.90%,72.49%～323.72% and 0.60%～34.78%,respectively,and bioavailability of copper and zinc were also decreased.(5)Under the treatment of high acidity simulation acid rain,10% biomass charcoal addition effect is obviously better than other biomass charcoal addition,whether from the degree of acid resistance,or the richness of available elements;Under middle and low acidity of simulated acid rain treatment,2% or 5% of the more significant effect of biochar,compared to 10% of the biomass carbon addition,improved 2% and 5% are relatively high,so in the middle and low acidity of acid and region,2% or 5% of the biomass charcoal can add more environmental protection,safety,economy to improve the soil heavy metal pollution.(6)in the Yangtze river delta region,biomass carbon added,can effectively mitigate soil acidic pH,improve soil fertility and enzyme activity,improve leach liquor acidity and metal ion freeness,greatly improved the ecological environment,soil biomass carbon can be used as acid rain stress,a safe,environmental protection and efficient soil conditioner.