TY - JOUR
T1 - Can functional group composition of alkaline isolates from black carbon-rich soils be identified on a sub-100nm scale?
AU - Heymann, Karen
AU - Lehmann, Johannes
AU - Solomon, Dawit
AU - Liang, Biqing
AU - Neves, Eduardo
AU - Wirick, Sue
N1 - Funding Information:
This study was financially supported by grants from the NSF IGERT program ( BCS-0215890 ), the NSF-Geobiology ( EAR-0819689 ), USDA-AFRI ( 2008-35107-04511 ) and the Department of Crop and Soil Sciences at Cornell University . Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of USDA or the National Science Foundation.
PY - 2014/12
Y1 - 2014/12
N2 - Objectives: Alkaline extracts from soils generate operationally-defined isolates that are referred to as "humic substances" but may not relate to a distinct molecular structure within the soil organic matter (SOM) matrix. This study examines whether alkaline extracts from black carbon (BC) rich soils can be identified on a fine spatial scale. Methods: We related the functional group composition of alkaline extracts derived from BC-rich soils using Scanning Transmission X-ray Microscopy (STXM) coupled with near-edge X-ray absorption fine- structure (NEXAFS) spectroscopy to the spatial composition of a BC-rich soil microaggregate at a scale of <. 50. μm. Soils were analyzed from 3 depths (0-0.16. m, 0.16-0.43. m, 0.43-0.67. m) along with their respective extracts. Results: Using principal component analysis, we were unable to obtain a good fit (RMS. <. 0.01) for the spectral properties of the alkaline extracts within the spatial map of the microaggregates. The presence of a distinct chemical structure resembling the alkaline extracts could not be verified within the soil organic matter matrix on a fine spatial scale. Conclusions: Our results suggest that a distinct component class similar to alkaline extracted materials, often referred to as "black humic substances", is not present in SOM on a fine spatial scale. Rather, alkaline extracts of BC-rich soils reflect the mixture of various materials at different stages of decomposition.
AB - Objectives: Alkaline extracts from soils generate operationally-defined isolates that are referred to as "humic substances" but may not relate to a distinct molecular structure within the soil organic matter (SOM) matrix. This study examines whether alkaline extracts from black carbon (BC) rich soils can be identified on a fine spatial scale. Methods: We related the functional group composition of alkaline extracts derived from BC-rich soils using Scanning Transmission X-ray Microscopy (STXM) coupled with near-edge X-ray absorption fine- structure (NEXAFS) spectroscopy to the spatial composition of a BC-rich soil microaggregate at a scale of <. 50. μm. Soils were analyzed from 3 depths (0-0.16. m, 0.16-0.43. m, 0.43-0.67. m) along with their respective extracts. Results: Using principal component analysis, we were unable to obtain a good fit (RMS. <. 0.01) for the spectral properties of the alkaline extracts within the spatial map of the microaggregates. The presence of a distinct chemical structure resembling the alkaline extracts could not be verified within the soil organic matter matrix on a fine spatial scale. Conclusions: Our results suggest that a distinct component class similar to alkaline extracted materials, often referred to as "black humic substances", is not present in SOM on a fine spatial scale. Rather, alkaline extracts of BC-rich soils reflect the mixture of various materials at different stages of decomposition.
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U2 - 10.1016/j.geoderma.2014.07.011
DO - 10.1016/j.geoderma.2014.07.011
M3 - Article
AN - SCOPUS:84904509381
SN - 0016-7061
VL - 235-236
SP - 163
EP - 169
JO - Geoderma
JF - Geoderma
ER -