British Journal of Environment and Climate Change, ISSN: 2231-4784,Vol.: 3, Issue.: 1 (January-March)-Special Issue
Original Research Article Special Issue
Oxidation is Key for Black Carbon Surface Functionality and Nutrient Retention in Amazon Anthrosols
Biqing Liang1,2*, Chung-Ho Wang1, Dawit Solomon2, James Kinyangi2,3, Flavio J. LuizÄƒo4, Sue Wirick5, Jan O. Skjemstad6 and Johannes Lehmann2*
1Institute of Earth Sciences, Academia Sinica, Nangang, Taipei 11129, Taiwan ROC.
2Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853, USA.
3International Livestock Research Institute (ILRI), P.O. Box 30709, 00100, Nairobi, Kenya.
4Instituto Nacional de Pesquisa da Amazônia (INPA), 69011-970 Manaus, Brazil.
5Department of Physics and Astronomy, State University of New York at Stony Brook, NY, USA.
6CSIRO Land and Water, PMB No. 2, Glen Osmond SA 5064, Australia.
Aims: Soil black carbon (BC) has been shown to possess large amounts of cation exchange sites and surface charge, and is viewed as a potential soil amendment to improve nutrient retention and for pollutant remediation. This study investigated the nano-scale distribution of reactive functional groups and the binding of cations on the surface of micron-size BC particles, identified the key processes, and explored the sources of surface functionality and their relative contribution to cation exchange capacity (CEC).
Materials and Methods: Elemental microprobe and synchrotron-based Scanning Transmission X-ray Spectromicroscopy (STXM) coupled with Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy were used for nano-scale mapping of cations and reactive functional groups, and further distinction of the sources of reactive functional groups generated either by oxidation of BC surfaces or by adsorption of non-BC organic matter onto the BC surfaces. Their respective contribution to cation adsorption was obtained using a depth profile of a BC-rich Anthrosol from the central Amazon, Brazil.
Results and Discussion: Adsorption of Non-BC organic matter is more dominant on the surface of BC particle in topsoil as evidenced by a stronger signal of microbial biomass and humic substances extracts. In comparison, a greater level of oxidation was found on the outerlayer of BC particles in subsoil horizons. Organic C in subsoils was found to generate 23-42% more CEC per unit C than topsoil. Based on CEC per unit C, the capacity of BC in creating CEC was 6-7 times higher than Non-BC, and the BC in deeper horizons had up to 20% higher CEC than the topsoil horizon. Near BC surfaces, higher ratios of Ca/C and K/C in subsoil than topsoil horizons reinforce the observation that BC in subsoil horizons had a higher capacity in binding cations and creating CEC than in the topsoil horizon.
Conclusions: Oxidation of BC is suggested to be more efficient and important for creating CEC than the adsorption of non-BC onto BC surfaces, thus identified as being key for BC surface functionality and nutrient retention in Amazon Anthrosols.
Adsorption; black carbon; nutrient retention; oxidation; surface functionality; synchrotron-based scanning transmission X-ray spectromicroscopy (STXM); near edge X-ray absorption fine structure (NEXAFS) spectroscopy.
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DOI : 10.9734/BJECC/2013/2267