Mineralogy and Geochemistry of urban soils of different age and land use in Qingdao, China.
Stefan Norra1, Nabil Fjer1, Thomas Neumann1, Doris Stüben1, Fanwei Lee2, and Xianfeng Shu2. (1) Institute of Mineralogy and Geochemistry, Universitaet Karlsruhe, Kaiserstr. 12, Karslruhe, Germany, (2) Qingdao Environmental Protection Bureau, 39 Yanan Yi Road, Qingdao, China
Qingdao is an intensive industrialized coastal town comprising more than 2 million inhabitants in the inner city. Present economic growth and migration led to a strong urban growth accompanied by the endangerment of the environment. Soil is one environmental compartment affected by urban growth. However, in comparison to water and air, soils are less investigated with respect of the consequences of urban growth, especially in developing countries such as China. We undertook an exemplarily investigation of five urban soils of different age and land use to assess the impact of urban development. Two of these soils were located in the inner city area. One soil profile was dig out in the garden of an old colonial style tenement representing a history of use of about 100 years. The other soil profile represents a time span of around 40 years of urban land use and was excavated between abandoned blocks of flats. We investigated a third soil profile located in the northern industrial area of Qingdao. This profile was on the area of a soda plant. The fourth profile was situated at the margin of an abandoned construction site in the modern inner city near to the coast. Furthermore, we surveyed a soil profile that represents as far as possible a natural soil. This soil is a Cambisol formed on granitic parent rock under forest in the north. We took samples from each soil horizon as well as of 10 cm layers. Qingdao urban soils are intensively disturbed. They are composed of up to more than 10 different horizons within 1 m depth. These horizons contain artificial and anthropogenic materials such as lime, domestic waste, construction waste, coal, and ashes. The pH-values of the urban soils vary between 6 and 8, whereas the natural soil shows pH-values between 4 and 5. Granitic minerals (quartz, feldspars, mica) dominate all soils but the urban soils show much higher shares of clay minerals and carbonates as the natural soil. The inner urban and oldest soil profile was most polluted by heavy metals, such as Zn, Cu and Pb, whereas the soil from the industrial site was astonishingly low polluted with respect to heavy metals. According to a cluster analysis, anthropogenic, geogenic and organic sources of analyzed parameters could be distinguished. The anthropogenic cluster comprises sub-clusters representing coal and its ashes, diffuse pollution sources and construction waste. It is obvious that the development of Qingdao urban soils is mainly determined by the input of construction waste. This input is subsequently increasing the thickness of the soils. The implementation of a construction waste management preventing the unregulated spreading of building rubble over the whole town would be useful to protect the soils against uncontrolled soil pollution, and would be a contribution to a sustainable urban development and for the preservation of soils for future generations.