【摘 要】
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Understanding the fate of terrestrial organic carbon (OC) in a cascade impoundment system is critical for recognizing the role of carbon sink for reservoirs.Surface sediments collected from eight cascade reservoirs across the Wujiang River,southwestern Ch
【机 构】
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School of Environmental and Chemical Engineering,Shanghai University,Shanghai 200444,China
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Understanding the fate of terrestrial organic carbon (OC) in a cascade impoundment system is critical for recognizing the role of carbon sink for reservoirs.Surface sediments collected from eight cascade reservoirs across the Wujiang River,southwestern China,were ana-lyzed for elemental and stable carbon isotopic (δ13C)composition,and lignin phenols (Σ8 and Λ8) to investigate the spatial distribution,contribution,origin and degrada-tion of sedimentary terrestrial OC.The values of total organic carbon (TOC) and Σ8 exhibited a remarkable reduction along the upstream-downstream transect sug-gesting the trapping effect of cascade-damming.A rela-tively broad range of δ13C (-26.61 to-25.54‰,95％ CI)and C/N (6.80-18.20) indicated mixed allochthonous/au-tochthonous OC sources in surface sediments.The uan-titative simulation indicates that the OC of the sediments mainly was derived from terrestrial organic matter.Soil-derived OC rather than C3 vascular plant-derived OC makes a major contribution to sedimentary terrestrial OC in reservoirs on karst terrain.As evidenced by lignin com-positions and δ13C,the predominant vascular plant origins of terrestrial OC along the Wujiang River are non-woody angiosperm C3 plants.The aged reservoirs showed a trend of increasing contribution of autochthonous OC,which potentially weaken the role of carbon sink for reservoirs.The relationship between runoff inputs,watershed area/water surface area ratios,and water residence time and A8 were explored,indicating the natural and anthropogenic influences on terrestrial OC remains very complex in a cascade-damming river.
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