Black Carbon Content Of Urban Forest Soil And Its Impact On Distribution Of Polycyclic Aromatic Hydrocarbons (PAHs)

Black carbon was biomass or fossil fuel incomplete combustion of the formation of a classof carbon compounds, widely presented in the atmosphere, soil and water. Black carbon was therecord of human activity, and also could keeping organic carbon, stabled soil carbon pool,adsorbing pollutants, and reduced the function of the toxicity of pollutants. With the analysis ofblack carbon in Nanjing urban forestry soil, the distribution characteristics and ecological effectsof black carbon in urban forestry soil were studied. The results as follows:(1) The contents in different functional zones of black carbon in the soil had large range.And their range was0.77to21.27g/kg. The level of black carbon content as followed: at thesurface, road green belts> urban natural forest> suburban natural forest> school>city greensquare> parks> residential; in the subsurface, roads green belts> schools> urban natural forest>city green square> suburban natural forest> parks> residential. The content of black carbon insurface soil was more than that in sub-surface. The difference between urban forest soil layers gota significant level. Soil organic carbon and black carbon content was significantly positivelycorrelated. The Pearson correlation coefficient was0.876. This showed that the increase in blackcarbon can significantly enhance the level of accumulation of organic carbon in the soil.(2) The value of black carbon/organic carbon in road green belts was between0.46and0.57.And δ13CPDBof black carbon was-27.04‰. So the main source of black carbon in road greenbelts was incomplete combustion of fossil fuels. The value of black carbon/organic carbon inurban forest was about0.2. And δ13CPDBof black carbon was-23‰. The main source wasincomplete combustion of biomass. The other zones were influenced by both fossil fuelcombustion and biomass burning.(3) The main source of polycyclic aromatic hydrocarbons was incomplete combustion offossil fuels. The content in road green belts was highest in all zones. And the contents in urbanforest and residential had low level. The relationship between black carbon and polycyclicaromatic hydrocarbons was significant positive correlation. The Pearson correlation coefficientswere0.567(total polycyclic aromatic hydrocarbons),0.687(2-3ring),0.540(4-6ring). Theseparameters were bigger than the parameters of the organic carbon. So the impact to black carbonfor the distribution of polycyclic aromatic hydrocarbons was much stronger than the influence oforganic carbon.