The wide-ranging impacts of globally increasing carbon dioxide (CO 2) concentration and rising metal-contaminated soils are serious problems in terrestrial ecosystems. In this study, we investigated the effects of elevated CO2 on the lead (Pb) uptake of pine seedlings and the microbial activity in Pb-contaminated soil. Three-year-old pine seedlings were exposed to ambient, as well as elevated levels of CO2 (380 and 760 ppmv, respectively) in 500 mg/kg Pb-contaminated soil. Growth rates, C/N ratios and Pb uptake of the pine seedlings were determined. Dissolved organic carbon (DOC) content and microbial activity were also measured in the rhizosphere soil. Elevated CO2 significantly increased the total biomass and accumulation of Pb in roots and shoots. In addition, the accumulation of Pb in the roots under elevated CO2 concentration was four times higher than those in the roots under ambient CO2 concentration. Elevated CO 2 levels also affected C/N ratios in the pine seedlings and soil enzyme activities. Decline in the overall nitrogen content and increases in the C/N ratios of pine needles were observed. Soil enzyme activity increased in the rhizosphere soils, including those of β-glucosidases, N- acetylglucosaminidases, and phosphatases. Quality of the DOC was affected by elevated CO2, while the quantity of DOC was affected by Pb additions under elevated CO2 conditions. Two major conclusions can be drawn from this study: (1) elevated CO2 significantly increased biomass and metal uptake of pine seedlings and (2) chemical metabolism on pine tissue and processes of organic decomposition were more affected by elevated CO2 levels than by Pb contamination.
All Science Journal Classification (ASJC) codes
- Environmental Engineering
- Environmental Chemistry
- Ecological Modelling
- Water Science and Technology