侵蚀黄土不同粒级抑制CO_(2)排放的有效沉积厚度  

Experimental Study on the Effective Depth for Different Erodible Loess Particles to Inhibit CO_(2) Emissions

作　　者：王文倩 宋媛 张辉 郭胜利[1,2,3,4] 栗现文 胡亚鲜 Wang Wenqian;Song Yuan;Zhang Hui;Guo Shengli;Li XianWen;Hu Yaxian(Research Center of Soil and Water Conservation and Ecological Environment,Chinese Academy of Sciences and Ministry of Education,Yangling,Shaanxi 712100,China;Institute of Soil and Water Conservation,Chinese Academy of Sciences and Ministry of Water Resources,Yangling,Shaanxi 712100,China;University of Chinese Academy of Sciences,Beijing,Shaanxi 100049,China;Institute of Soil and Water Conservation,Northwest A&F University,Yangling,Shaanxi 712100,China;College of Water Resources and Architectural Engineering,Northwest A&F University,Yangling,Shaanxi 712100,China)

机构地区：[1]中国科学院教育部水土保持与生态环境研究中心,陕西杨凌712100 [2]中国科学院水利部水土保持研究所,陕西杨凌712100 [3]中国科学院大学,北京100049 [4]西北农林科技大学水土保持研究所,陕西杨凌712100 [5]西北农林科技大学水利与建筑工程学院,陕西杨凌712100

出　　处：《水土保持研究》2024年第6期119-129,共11页Research of Soil and Water Conservation

基　　金：中国科学院“西部之光”人才培养计划“西部青年学者”项目(XAB2020YN03);陕西省引进高层次人才专(F2020221001)。

摘　　要：[目的]探讨沉积泥沙粒级及厚度对剖面CO_(2)传输过程的影响,明确不同含水率条件下侵蚀黄土不同粒级抑制CO_(2)排放的有效沉积厚度,为完善沉积区有机碳矿化和排放过程提供理论依据。[方法]通过沉降速度分选为4个粒级(≥250μm,250~125μm,125~63μm,≤63μm),各粒级分别在静态水体中沉积形成0.4 cm,0.7 cm,1.4 cm和2 cm共4个薄层沉积厚度。各沉积土柱保持田间持水量,先进行恒湿自矿化(7 d),后将^(13)C葡萄糖标记黄土置于土柱底部作为独立CO_(2)释放源,进行^(13)C标记CO_(2)示踪(7 d),最后将各土柱自然干裂(7 d),对比这3个阶段的CO_(2)释放效率和^(13)C相对丰度变化特征。[结果](1)各土柱的平均CO_(2)通量在恒湿自矿化阶段(无^(13)C标记CO_(2)释放源)为0.21μg/(cm^(2)·h),略低于^(13)C标记CO_(2)示踪阶段的0.35μg/(cm^(2)·h),且两者均显著低于自然干裂阶段0.9μg/(cm^(2)·h),说明湿润状态下黄土沉积层均对CO_(2)释放有不同程度的抑制作用,但随着土壤干裂,封存于土层中CO_(2)便会集中释放,削弱沉积碳汇效应。(2)粗颗粒(D≥250μm)在3个培养阶段的平均CO_(2)通量较细颗粒(D<63μm)分别高出77.9%,39.6%和30.8%,且粗颗粒在3个培养阶段的CO_(2)通量和^(13)C相对丰度差异比细颗粒更显著,且峰值提前1 d。(3)各沉降粒级在湿润状态时,粒径≥125μm的黄土容重较小而充气孔隙度和气体扩散系数相对较大,需至少2 cm沉积厚度才可有效抑制CO_(2)传输,而粒径为63≤D<125μm和D<63μm时,充气孔隙度和气体扩散系数极小,仅1.4 cm甚至更薄的沉积厚度,便可有效抑制CO_(2)向表土扩散。[结论]黄土沉积区须有细密颗粒覆盖且保持较高的含水率才可有效抑制CO_(2)向地表传输,从而保证沉积掩埋碳汇效应,且不同黄土颗粒抑制CO_(2)排放的有效沉积厚度存在差异。[Objective]The aims of this study are to examine the effects of sediment grain size and thickness on the CO_(2) transport process in the profile,to clarify the effective deposition thickness of different grain sizes of eroded loess to inhibit CO_(2) emission under different water content conditions,and to provide a theoretical basis for improving the process of organic carbon mineralization and emission in the sedimentary area.[Methods]By settling fractionation,the loess particles of four different size classes(≥250μm,250~125μm,125~63μm,and≤63μm)were settled freely through a static water column to form thin soil columns with different thicknesses(0.4 cm,0.7 cm,1.4 cm,and 2 cm).Each sediment column was maintained at field water holding capacity,subjected to constant moisture mineralization,and subsequently amended with ^(13)C-labeled glucose to serve as an independent CO_(2) source.The released ^(13)C-labeled CO_(2) was traced,and the relative abundance of ^(13)C was analyzed during three stages:constant moisture mineralization,^(13)C-labeled CO_(2) tracing,and natural desiccation.[Results](1)The average CO_(2) emission rate during constant moisture mineralization(without ^(13)C-labeled CO_(2))was 0.21μg/(cm^(2)·h),slightly lower than the 0.35μg/(cm^(2)·h)during ^(13)C-labeled CO_(2) tracing,both significantly lower than the 0.9μg/(cm^(2)·h)during natural desiccation.This indicated that loess sediment layers exhibited varying degrees of inhibitory effects on CO_(2) emissions under moist conditions.However,upon soil desiccation,CO_(2) previously sequestered within the soil layer was concentrated and released,weakening the sediment carbon sink effect.(2)The average CO_(2) emission rates for coarse particles(D≥250μm)were 77.9%,39.6%,and 30.8% higher than for fine particles(D<63μm)in the three cultivation stages,respectively.Coarse particles exhibited more pronounced differences in CO_(2) emission rates and ^(13)C relative abundance compared to fine particles,and this effect was observed one day earl

关 键 词：黄土 沉积 碳汇 粒径 CO_(2) 气体传输 ^(13)C示踪 

分 类 号：S157.1[农业科学—土壤学]