坡面片蚀泥沙有机碳组分及^(13)C同位素不均匀富集对水动力学参数的响应  

Hydrodynamics and^(13)C Isotopic Characteristics of Non-uniform Enrichment of Light and Heavy Fractions of Organic Carbon in Eroded Sediments on Sloping Land Subjected to Sheet Erosion

作　　者：屈久祁 刘琳 王善琦 Qu Jiuqi;Liu Lin;Wang Shanqi(College of Geography and Environment,Shandong Normal University,Jinan,Shandong 250000,China)

机构地区：[1]山东师范大学地理与环境学院,山东济南250000

出　　处：《水土保持通报》2024年第1期399-409,431,共12页Bulletin of Soil and Water Conservation

基　　金：国家自然科学基金项目“棕壤坡面颗粒有机碳流失对团聚体破碎的响应”(41907055);中国博士后科学基金资助项目“棕壤坡面团聚体颗粒有机碳流失机制”(2019M652456)。

摘　　要：[目的]探究片蚀泥沙轻组有机碳(LF_(OC))和重组有机碳(HF_(OC))不均匀富集的水动力学和碳同位素特征,为正确理解水蚀作用下土壤有机碳库变化提供理论与技术支撑。[方法]以陕西省咸阳市杨凌区土为研究对象,采用改进“三区”移动式变坡钢制土槽,结合人工模拟降雨技术,测定径流水动力学参数和泥沙各粒径团聚体有机碳组成及其δ^(13)C值,并辅以棕壤侵蚀泥沙有机碳δ^(13)C值和水力参数,验证土试验结果的准确性。[结果]①雨强和坡度较小时,侵蚀泥沙LF_(OC)和HF_(OC)易发生富集,且相较黏粉粒和微团聚体,大团聚体LF_(OC)与HF_(OC)含量受雨强和坡度的影响更大;②侵蚀泥沙黏粉粒中有机碳δ^(13)C值与其有机碳活跃分数(λ)呈负相关,而其他粒径团聚体有机碳δ^(13)C值与其λ呈显著正相关(p<0.05);③流速与黏粉粒λ显著正相关(p<0.05),雷诺数与各粒径团聚体有机碳δ^(13)C值均呈显著负相关(p<0.01),片蚀过程中流速越大,黏粉粒中LF_(OC)越易于优先输移,而紊流加剧则促进低δ^(13)C值团聚体有机碳的优先输移;④对于侵蚀泥沙黏粉粒,流速和雷诺数越大,其有机碳δ^(13)C值越小,λ越大;对于微团聚体和大团聚体,雷诺数越小,其有机碳δ^(13)C值与λ越大。[结论]片蚀过程中轻重组有机碳流失与流速和雷诺数密切相关。并进一步验证了^(13)C同位素对侵蚀泥沙有机碳示踪的有效性。[Objective]The hydraulic characteristics and^(13)C isotopic characteristics of the non-uniform enrichment of light(LF_(OC))and heavy(HF_(OC))fractions of soil organic carbon in sediments during the sheet erosion process were determined in order to provide theoretical and technical support for a better understanding of the dynamic changes in soil organic carbon stocks under water erosion.[Methods]This study was conducted on Lou soil from Yangling District of Xianyang City,Shannxi Province.An improved"three-zone"mobile steel soil pan was used together with an artificial rainfall simulator to measure runoff hydraulic parameters,organic carbon compositions of each aggregate size in sediments,and their relatedδ^(13)C values.Additionally,these results for Lou soil were verified based on theδ^(13)C values of organic carbon in eroded sediments and runoff hydraulic parameters for brown soil.[Results]①When rainfall intensity and slope were low,both LF_(OC)and HF_(OC)were enriched in eroded sediments,and the organic carbon composition of macroaggregates were observed to be more susceptible to the influence of rainfall intensity and slope than observed for clay and silt particles and microaggregates.②Theδ^(13)C values of organic carbon in clay and silt particles were negatively correlated with the percentage of LF_(OC)in SOC(λ),while theδ^(13)C values of organic carbon in other size aggregates showed a significant positive correlation withλvalues(p<0.05).③Flow velocity was positively correlated withλvalues of clay and silt particles(p<0.05),while Reynolds number was negatively correlated withδ^(13)C values of clay and silt particles,microaggregates,and macroaggregates(p<0.01).Increasing flow velocity during sheet erosion promoted the preferential transport of clay and silt size organic carbon,while turbulence promoted the transport of organic carbon with lowδ^(13)C values in aggregates;④For clay and silt particles,the larger the flow velocity and Reynolds number,the smaller theδ^(13)C value of organic carbo

关 键 词：片蚀 轻组有机碳 重组有机碳 水动力学特征 δ^(13)C 分馏效应 

分 类 号：S153.6[农业科学—土壤学]