The Study Of Black Carbon Spatial Varition And Correlations With Polycyclic Aromatic Hydrocarbons In Urban Forest Soil Of Nanjing

Black carbon has an great impact on global warming, regional climate, environmant and health. It is a kind of carbonaceous material, resulting from burning coal and fossil, and widely distributed in the atmosphere, soil, snow and water and sediments. In this experiment, we collect 162 soil samples,using grid sampling(10km*10km) at the main city of Nanjing, then choose 8 typical functional areas, each area collcets 3 sample points using grid sampling(2km*2km),and every sample point collcet three levels of samples, the size is 0 to 20 cm, 20 to 40 cm and 40 to 60 cm. We uesthermochemical reaction method measuring how many black carbon in the soil. We use ArcGIS Geostatistical analysis and SPSS correlation analysis to study overall spatial distribution of black carbon, black carbon content in different functional areas as well as the correlation between the carbon content of black urban forestry and total organic carbon content in soil, PAHs content, thereby affecting factors and the impact of black carbon sources of black carbon distribution. The following content is our main resulting:1.The contents of black carbon in the Nanjing city forestry soil have large range.And their rang is 0.7245 g/kg ~ 13.9340 g/kg, with a mean of 4.429 g/kg, presents obvious space difference. Black carbon concentration distribution in Nanjing city forestry soil has certain continuity, high concentration values appeared, from the middle to the north and south on both sides of the present decreasing trend, namely from the downtown to suburbs on both sides showed a trend of decline. Seen from space, the black carbon content has a high value in the heart of the city traffic hub such as the east bus station, Xinzhuang transport hub and GuLou Xinjiekou traffic areas. That black carbon content affected by incomplete combustion of motor vehicle fuel. Spatial interpolation figure reflects the urban forest of black carbon content in the soil in addition to the affected by automobile exhaust is affected by the disturbance of human activities2.From the interpolation prediction map,the contents of black carbon and total organic carbon in the Nanjing city forestry soil have overlap on the graph of high value parts, the graphic patch distribution also have similarities. Black carbon content and total organic carbon content has significant correlation(p<0.01).The Pearson correlation coefficient was 0.876.This showed that black carbon has an important role in fixing the organic carbon in the Nanjing city forestry soil.It can help stabilize the soil structure,maintain soil fertility,preventing soil degradation.3.In main of Nanjing city forestry soil the value of black carbon/organic carbon is about o.5~0.7,this showed that the major source of black carbon in the soil for the burning of fossil fuels. The value of black carbon/organic carbon in urban forest is about 0.13,the major source of black carbon for the burning of biomass.The contents in different functional zones of black carbon have the difference, transport hub area and road green belts with high content of stems mainly from automobile fuel oil incomplete combustion. And with the development of the city constantly, the boundaries of each functional areas also increasingly blurred, environment mutual penetration, mixed with each other, black carbon content in various functional areas of difference also gradually narrowed.4.In Nanjing city forestry soil the main soure of PAHs was incomplete combustion of fossil fuels.In almost functional zones the relationship between black carbon organic carbon and polycyclic aromatic hydrocarbons was significant positive correlation.The Pearson correlation coefficients are about 0.8~0.9.In urban forest soil, the distribution of PAHs and significantly affected by the organic carbon and black carbon, and the influence of black carbon is more significant. And compared to the low number of ring PAHs, the number of epipodium PAHs could be more influenced by organic carbon, carbon black, this is because the number of epipodium molecular weight PAHs is higher, its chemical properties more stable and less volatile.