Carbonic acid produced by the dissolution of atmospheric and soil CO_(2)in water is usually the most dominant catalyst for chemical weathering,but a sulfuric aciddriven phenomenon,different from usual,was found in the...Carbonic acid produced by the dissolution of atmospheric and soil CO_(2)in water is usually the most dominant catalyst for chemical weathering,but a sulfuric aciddriven phenomenon,different from usual,was found in the orogenic belt watersheds dominated by silicate bedrock.This study,rooted in comprehensive field investigations in the Manas River Basin(MRB)north of the Tianshan Mountains,delves into the mechanisms and impacts of sulfuric and carbonic acid as catalysts driving diff erent types of chemical weathering in the Central Asian Orogenic Belt.Quantitative analyses elucidate that carbonate weathering constitutes 52.4%of the total chemical weathering,while silicate and evaporite account for 18.6%and 25.3%,respectively,with anthropogenic activities and atmospheric precipitation having little eff ect.The estimated total chemical weathering rate in MRB is approximately 0.075×10^(6)mol/km^(2)/year.Quantitative findings further suggest that,preceding carbonate precipitation(<10^(4)year),chemical weathering can absorb CO_(2).Subsequently,and following carbonate precipitation(10^(4)-10^(7)year),it will release CO_(2).The release significantly surpasses the global average CO_(2)consumption,contributing to a noteworthy climate impact.This study underscores the distinctive weathering mechanisms,wherein sulfuric acid emerges as the predominant catalyst.The quantity of sulfuric acid as a catalyst is approximately three times that of carbonic acid.Sulfuric acid-driven carbonate rock weathering(SCW)is identified as the sole chemical weathering type with a net CO_(2)release eff ect.SCW CO_(2)release flux(5176 mol/km^(2)/year)is roughly 2.5 times the CO_(2)absorption by Ca-Mg silicate weathering,highlighting the pivotal role of chemical weathering in sourcing atmospheric CO_(2)over the timescales of carbonate precipitation and sulfate reduction.Lastly,this study posits that catalyst and transport limitations are the most plausible critical factors in MRB.The interplay between sulfuric acid and dissolved CO_(2)competitively shapes the types and rates of chemical weathering reactions.展开更多
在地质历史时期,大陆化学风化作为一种调节气候的负反馈机制,是维持“宜居地球”的关键。然而,地质记录中的证据显示,新生代以来气温逐渐下降,而大陆化学风化却逐渐增加,对这一机制提出了挑战。深入研究化学风化和温度的关系成为解答这...在地质历史时期,大陆化学风化作为一种调节气候的负反馈机制,是维持“宜居地球”的关键。然而,地质记录中的证据显示,新生代以来气温逐渐下降,而大陆化学风化却逐渐增加,对这一机制提出了挑战。深入研究化学风化和温度的关系成为解答这一矛盾的关键,也是当前地球系统科学研究的热点。近期有研究显示,高纬极地地区虽然温度低,但其河流沉积物的化学蚀变指数(chemical index of alteration,CIA)却达到中等风化水平。因此,深入研究极地化学风化,可能是打开风化与温度之谜的关键钥匙。本文回顾了南北两极地区化学风化研究的主要进展和成果,并尝试总结极地地区化学风化的主要特征。南北两极不同的地理格局和地质背景决定了两极化学风化的差异。南极大陆由于冰盖覆盖缺乏河流,沉积物多为就近搬运和沉积;而北极地区周边大陆有众多大型河流,源-汇体系发育,水文条件和母岩属性决定了北极地区具有更强的沉积风化记录。相比低纬热带典型风化区域,目前对极地地区尤其是南极地区化学风化的研究仍十分欠缺,新兴地球化学分析开展的较少。在未来大陆风化研究中,重视和加强两极地区的化学风化研究有利于完善低温条件下的化学风化机理的探索;同时,在当今全球变暖和极地放大效应的影响下,研究极地的化学风化如何加速全球碳汇效应可以加深对全球气候变化理论的认识。展开更多
若尔盖盆地黄土—古土壤序列较好地记录了古湖泊消失后的地表过程及演变。本文选取玛曲段黄河二级阶地欧强村剖面为研究对象,对其粒度、磁化率、总有机碳(TOC)、色度、元素等进行分析,利用光释光(OSL)方法测年断代。结果表明:(1)黄河二...若尔盖盆地黄土—古土壤序列较好地记录了古湖泊消失后的地表过程及演变。本文选取玛曲段黄河二级阶地欧强村剖面为研究对象,对其粒度、磁化率、总有机碳(TOC)、色度、元素等进行分析,利用光释光(OSL)方法测年断代。结果表明:(1)黄河二级阶地在10 ka BP前后开始接受连续的风尘堆积,发育的黄土—古土壤序列年代由下至上依次为河流相沉积物(T_(2-al),>10.0 ka)→黄土(L1,10.0—8.5 ka)→古土壤(S_(0),8.5—3.0 ka)→现代表土(L_(0)+MS,3.0—0 ka)。(2)欧强村剖面整体上处于以斜长石风化分解为主、钾长石尚未分解的初等化学风化阶段(CIA值在48.20~63.08之间),与黄土层相比,古土壤S0风化程度有所增强(CIA值60.83),但增强程度有限。(3)10 ka BP前后,若尔盖盆地气候干冷,风沙活动盛行,平缓的阶地面上开始接受持续的风尘堆积(形成黄土L1);8.5 ka BP前后,气候温湿,风沙活动明显减弱和风化成壤作用占主导,区域上形成了以黑灰色为特征的古土壤S_(0);3.0 ka BP前后,气候转为较冷干,风沙活动强烈,古土壤S0发育中断和被黄土L0所覆盖,形成了现代土壤MS。(4)若尔盖盆地黄土—古土壤序列在宏观形态、地层年代和物性参数方面与黄土高原可进行良好对比,但这些参数的绝对值和变化幅度差异显著,暗示高寒区(若尔盖盆地)这些参数的环境意义可能与季风湿润区(黄土高原)有所不同。本文可为若尔盖盆地风积物的年代学研究和环境信息的提取提供基础数据支撑。展开更多
基金support from the Third Xinjiang Scientific Expedition Program(2021XJKK0803)the National Natural Science Foundation of China(No.41930640)the Project of the Second Comprehensive Scientific Investigation on the Qinghai-Tibetan Plateau(2019QZKK1003)。
文摘Carbonic acid produced by the dissolution of atmospheric and soil CO_(2)in water is usually the most dominant catalyst for chemical weathering,but a sulfuric aciddriven phenomenon,different from usual,was found in the orogenic belt watersheds dominated by silicate bedrock.This study,rooted in comprehensive field investigations in the Manas River Basin(MRB)north of the Tianshan Mountains,delves into the mechanisms and impacts of sulfuric and carbonic acid as catalysts driving diff erent types of chemical weathering in the Central Asian Orogenic Belt.Quantitative analyses elucidate that carbonate weathering constitutes 52.4%of the total chemical weathering,while silicate and evaporite account for 18.6%and 25.3%,respectively,with anthropogenic activities and atmospheric precipitation having little eff ect.The estimated total chemical weathering rate in MRB is approximately 0.075×10^(6)mol/km^(2)/year.Quantitative findings further suggest that,preceding carbonate precipitation(<10^(4)year),chemical weathering can absorb CO_(2).Subsequently,and following carbonate precipitation(10^(4)-10^(7)year),it will release CO_(2).The release significantly surpasses the global average CO_(2)consumption,contributing to a noteworthy climate impact.This study underscores the distinctive weathering mechanisms,wherein sulfuric acid emerges as the predominant catalyst.The quantity of sulfuric acid as a catalyst is approximately three times that of carbonic acid.Sulfuric acid-driven carbonate rock weathering(SCW)is identified as the sole chemical weathering type with a net CO_(2)release eff ect.SCW CO_(2)release flux(5176 mol/km^(2)/year)is roughly 2.5 times the CO_(2)absorption by Ca-Mg silicate weathering,highlighting the pivotal role of chemical weathering in sourcing atmospheric CO_(2)over the timescales of carbonate precipitation and sulfate reduction.Lastly,this study posits that catalyst and transport limitations are the most plausible critical factors in MRB.The interplay between sulfuric acid and dissolved CO_(2)competitively shapes the types and rates of chemical weathering reactions.
文摘在地质历史时期,大陆化学风化作为一种调节气候的负反馈机制,是维持“宜居地球”的关键。然而,地质记录中的证据显示,新生代以来气温逐渐下降,而大陆化学风化却逐渐增加,对这一机制提出了挑战。深入研究化学风化和温度的关系成为解答这一矛盾的关键,也是当前地球系统科学研究的热点。近期有研究显示,高纬极地地区虽然温度低,但其河流沉积物的化学蚀变指数(chemical index of alteration,CIA)却达到中等风化水平。因此,深入研究极地化学风化,可能是打开风化与温度之谜的关键钥匙。本文回顾了南北两极地区化学风化研究的主要进展和成果,并尝试总结极地地区化学风化的主要特征。南北两极不同的地理格局和地质背景决定了两极化学风化的差异。南极大陆由于冰盖覆盖缺乏河流,沉积物多为就近搬运和沉积;而北极地区周边大陆有众多大型河流,源-汇体系发育,水文条件和母岩属性决定了北极地区具有更强的沉积风化记录。相比低纬热带典型风化区域,目前对极地地区尤其是南极地区化学风化的研究仍十分欠缺,新兴地球化学分析开展的较少。在未来大陆风化研究中,重视和加强两极地区的化学风化研究有利于完善低温条件下的化学风化机理的探索;同时,在当今全球变暖和极地放大效应的影响下,研究极地的化学风化如何加速全球碳汇效应可以加深对全球气候变化理论的认识。
文摘若尔盖盆地黄土—古土壤序列较好地记录了古湖泊消失后的地表过程及演变。本文选取玛曲段黄河二级阶地欧强村剖面为研究对象,对其粒度、磁化率、总有机碳(TOC)、色度、元素等进行分析,利用光释光(OSL)方法测年断代。结果表明:(1)黄河二级阶地在10 ka BP前后开始接受连续的风尘堆积,发育的黄土—古土壤序列年代由下至上依次为河流相沉积物(T_(2-al),>10.0 ka)→黄土(L1,10.0—8.5 ka)→古土壤(S_(0),8.5—3.0 ka)→现代表土(L_(0)+MS,3.0—0 ka)。(2)欧强村剖面整体上处于以斜长石风化分解为主、钾长石尚未分解的初等化学风化阶段(CIA值在48.20~63.08之间),与黄土层相比,古土壤S0风化程度有所增强(CIA值60.83),但增强程度有限。(3)10 ka BP前后,若尔盖盆地气候干冷,风沙活动盛行,平缓的阶地面上开始接受持续的风尘堆积(形成黄土L1);8.5 ka BP前后,气候温湿,风沙活动明显减弱和风化成壤作用占主导,区域上形成了以黑灰色为特征的古土壤S_(0);3.0 ka BP前后,气候转为较冷干,风沙活动强烈,古土壤S0发育中断和被黄土L0所覆盖,形成了现代土壤MS。(4)若尔盖盆地黄土—古土壤序列在宏观形态、地层年代和物性参数方面与黄土高原可进行良好对比,但这些参数的绝对值和变化幅度差异显著,暗示高寒区(若尔盖盆地)这些参数的环境意义可能与季风湿润区(黄土高原)有所不同。本文可为若尔盖盆地风积物的年代学研究和环境信息的提取提供基础数据支撑。
