The adsorption behavior of black carbon in urban forest and traffic district soils toward heavy metal ions (Cu, Zn)
In China, many pollutants due to urbanization, traffic, and mining activities contaminate soil in urban areas. These pollutants include black carbon and persistent organic pollutants (POPs). They can remain in urban soils for a long time, which may play an important role in further pollution in urban environments, and pose a potential threat to human health and ecological systems. Adsorption of Cu and Zn in single metal solutions by traffic district and urban forest soils was investigated in batch sorption experiments. The black carbon (BC) of soils was also investigated. The soil samples were taken over 0-10 cm depths from traffic district and urban forest in Nanjing, China main urban areas (118°22′–119°14′E, 31°14′–32°37′N).
The results showed complete differences in adsorption capacities of the studied soils. Traffic district soil had higher adsorption capacities than urban forest soil. The adsorption sequence Cu > Zn was established for the traffic district and urban forest soil. The Freundlich and Langmuir models described the experimental isotherms for the metal sorption. Traffic district soil containing a high amount of BC is characterized by the higher adsorption capacity towards the metals, compared to urban forest soil with a lower BC content. Properties of the soils, such as pH and the content of clay and organic matter, showed a significant influence on adsorption capacities of the studied soils.