摘要
In order to understand the transport and humification processes of dissolved organic matter（DOM） within sediments of a semi-arid floodplain at Rifle,Colorado,fluorescence excitation–emission matrix（EEM） spectroscopy,humification index（HIX） and specific UV absorbance（SUVA） at 254 nm were applied for characterizing depth and seasonal variations of DOM composition.Results revealed that late spring snowmelt leached relatively fresh DOM from plant residue and soil organic matter down into the deeper vadose zone（VZ）.More humified DOM is preferentially adsorbed by upper VZ sediments,while non-or lesshumified DOM was transported into the deeper VZ.Interestingly,DOM at all depths undergoes rapid biological humification process evidenced by the products of microbial by-product-like（i.e.,tyrosine-like and tryptophan-like） matter in late spring and early summer,particularly in the deeper VZ,resulting in more humified DOM（e.g.,fulvic-acid-like and humic-acid-like substances） at the end of year.This indicates that DOM transport is dominated by spring snowmelt,and DOM humification is controlled by microbial degradation,with seasonal variations.It is expected that these relatively simple spectroscopic measurements（e.g.,EEM spectroscopy,HIX and SUVA） applied to depth-and temporally-distributed pore-water samples can provide useful insights into transport and humification of DOM in other subsurface environments as well.
In order to understand the transport and humification processes of dissolved organic matter（DOM） within sediments of a semi-arid floodplain at Rifle,Colorado,fluorescence excitation–emission matrix（EEM） spectroscopy,humification index（HIX） and specific UV absorbance（SUVA） at 254 nm were applied for characterizing depth and seasonal variations of DOM composition.Results revealed that late spring snowmelt leached relatively fresh DOM from plant residue and soil organic matter down into the deeper vadose zone（VZ）.More humified DOM is preferentially adsorbed by upper VZ sediments,while non-or lesshumified DOM was transported into the deeper VZ.Interestingly,DOM at all depths undergoes rapid biological humification process evidenced by the products of microbial by-product-like（i.e.,tyrosine-like and tryptophan-like） matter in late spring and early summer,particularly in the deeper VZ,resulting in more humified DOM（e.g.,fulvic-acid-like and humic-acid-like substances） at the end of year.This indicates that DOM transport is dominated by spring snowmelt,and DOM humification is controlled by microbial degradation,with seasonal variations.It is expected that these relatively simple spectroscopic measurements（e.g.,EEM spectroscopy,HIX and SUVA） applied to depth-and temporally-distributed pore-water samples can provide useful insights into transport and humification of DOM in other subsurface environments as well.
基金
partially performed at the Molecular Foundry,Lawrence Berkeley National Laboratory
supported as part of the Sustainable Systems Scientific Focus Area program at Lawrence Berkeley National Laboratory
supported by the U.S.Department of Energy,Office of Science,Office of Biological and Environmental Research,Subsurface Biogeochemical Research Program,through Contract No.DE-AC02-05CH11231 between Lawrence Berkeley National Laboratory and the U.S.Department of Energy
