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化学蚀变指数(CIA)反映湿润亚热带风化壳型土壤风化强度的适用性探讨

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风化壳型土壤剖面是记录"地球关键带"长期信息的重要载体.然而,目前对大范围的风化壳-土壤原位风化过程研究较少,化学风化指标能否指示其风化强度存在争议.本研究以广东省湿润亚热带气候主导区的6个花岗岩风化壳型土壤剖面为研究对象,结合土壤的常量元素地球化学和粒度数据来描述剖面的化学风化和物理变化,探讨CIA反映湿润亚热带风化壳型土壤风化强度的适用性.结果显示:在温带地区迁移作用微弱的惰性元素Fe、Al、Ti在亚热带风化剖面上层含量相对中下层较低;随着地区降水量的增加,CIA从剖面顶部到底部数值呈增加趋势,这与风化壳剖面自上而下风化强度减弱的理想风化趋势相悖;并且发现CIA指标与气候参数,尤其是降水之间存在良好的反相关关系(R2=0.77,P<0.01,y=-0.0065x+104.01).通过对该异常现象的探讨,得到以下认识:在湿润亚热带地区,风化壳表层土壤具有复杂的物理、化学变化,尤其是高降水量引起的物理侵蚀使得化学活动性弱的Fe、Al、Ti氧化物、以及粘粒被地表径流带走或者下渗到更深层土壤中,使得表层土壤的CIA值偏低,不能真实反映其化学风化强度.因此,在应用CIA指标反映湿润亚热带高降水地区风化壳土壤剖面的风化强度时应当谨慎.
THE APPLICABILITY OF CHEMICAL INDEX OF ALTERATION(CIA)TO REFLECT WEATHERING INTENSITY OF HUMID SUBTROPICAL WEATHERING CRUST SOIL
Weathering crust-soil profile is an important carrier to record the long-term information of the"Earth Critical Zone".However,there are limited studies on the in-situ weathering of a wide variety of weathering crust,and it is debatable whether chemical weathering indexes can accurately reflect weathering intensity.In this paper,six granite weathering crust soil profiles in Guangdong Province's humid subtropical climate area(22.152°~23.579° N,111.787°~115.853° E)were used as the research object,which are Conghua section(CH:23.579°N,113.538°E),Xinxing section(XX:22.647° N,112.206°E),Huidong section(HD:23.020°N,114.679°E),Jiexi section(JX:23.413°N,115.853°E),Boluo section(BL:23.517° N,114.474°E),and Yangchun section(YC:22.152°N,111.787°E).A total of 265 samples were collected with 10cm as the sampling interval,and individual soil layers with larger thickness were separated by 20 cm.The thickness of the collected profiles is between 3.5 m and 5.5 m.Meteorological data for each profile are from the nearest weather station and are averaged over a 30-year period(1981~2010).The major geochemical element and grain size were measured and analyzed to describe the chemical weathering and physical changes of the profiles,and discuss the applicability of CIA values in reflect weathering intensity.The results demonstrated that the contents of Fe,Al,and Ti,which had a negligible effect on migration in the temperate zone,decreased in the upper layer of the subtropical weathering profile.With the increase of regional precipitation,the value of CIA increased from the top to the bottom of the weathering profile,which was contrary to the ideal weathering trend that the top-down weathering intensity of the weathering crust profile decreased.Additionally,there was a good negative relationship between the CIA and climate variables,particularly precipitation(R2=0.77,P<0.01,y=-0.0065x+104.01).Through the discussion of this abnormal phenomenon,the following understandings were obtained:in humid subtropical areas,the surface soil of weathering crust had complex physical and chemical changes,especially the physical erosion caused by high precipitation makes the chemically inactive Fe,Al,Ti oxides and clay particles carried away by surface runoff or infiltrated into deeper soil,resulting in low CIA value of the surface soil,which cannot truly reflect its chemical weathering intensity.Therefore,The CIA index should be utilized carefully to reflect the weathering intensity of humid subtropical region with high precipitation.

major geochemical elementChemical Index of Alterationchemical weathering intensityweathering crust soilhumid subtropical zone

陈田圆、吕镔、李嘉伟、唐金梦、刘鑫

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福建师范大学湿润亚热带生态-地理过程教育部重点实验室,福建福州 350117

福建师范大学地理科学学院、碳中和未来技术学院,福建福州 350117

兰州大学资源环境学院,西部环境教育部重点实验室,甘肃兰州 730000

常量地化元素 化学蚀变指数 化学风化强度 风化壳型土壤 湿润亚热带

国家自然科学基金项目国家自然科学基金项目国家自然科学基金项目

418774354227744242130507

2024

第四纪研究
中国科学院地质与地球物理研究所 中国第四纪研究委员会

第四纪研究

CSTPCD北大核心
影响因子:2.939
ISSN:1001-7410
年,卷(期):2024.44(2)
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