改进沉淀法在溶解性无机碳稳定同位素测定中的应用研究  

Application of the Improved Precipitation Method in the Detection of Stable Isotope of Dissolved Inorganic Carbon

作　　者：赵志超 吴宇波 廖振良[1] 冯公垚 ZHAO Zhichao;WU Yubo;LIAO Zhenliang;FENG Gongyao(Key Laboratory of Yangtze River Water Environment(Ministry of Education),UNEP-Tongji Institute of Environment for Sustainable Development,Shanghai 200092,China;School of Life Sciences,Jinggangshan University,Jiangxi Ji'an 343009,China;Institute of Architecture and Engineering,Xinjiang University,Urumqi 830047,China)

机构地区：[1]同济大学长江水环境教育部重点实验室,联合国环境署-同济大学环境与可持续发展学院,上海200092 [2]井冈山大学生命科学学院,江西吉安343009 [3]新疆大学建筑工程学院,乌鲁木齐830047

出　　处：《地球与环境》2022年第5期623-629,共7页Earth and Environment

基　　金：国家自然科学基金项目(51778451);国家水体污染控制与治理科技重大专项课题(2018ZX07208006)。

摘　　要：水体中溶解性无机碳(Dissolved inorganic carbon,DIC)的稳定碳同位素比值(δ^(13)C_(DIC))是揭示碳循环过程的重要技术指标。DIC的分离和富集是测定δ^(13)C_(DIC)的基础,也是影响δ^(13)C_(DIC)测定准确度的主要过程之一。沉淀法和气体法均为常用的DIC分离和富集方法。相比于气体法,沉淀法操作流程简单,适用性较强,在δ^(13)C_(DIC)测定过程中具有广阔的应用前景。然而,基于沉淀法的DIC分离和富集过程中常存在碳稳定同位素分馏问题。为此,本研究在综合气体法和沉淀法优缺点的基础上,以超声时间,水浴温度和氮气吹扫速率为自变量,以δ^(13)C_(DIC)的理论值与实测值之间绝对误差的最小化为目标,采用响应面法对传统NaOH-BaCl_(2)沉淀法进行了改进。基于改进沉淀法测定的δ^(13)C_(DIC)理论值与实测值之间的绝对误差,以及两处城市河流水体平行样品δ^(13)C_(DIC)的标准偏差分别为0.052‰、0.061‰和0.037‰。上述结果表明了该方法在δ^(13)C_(DIC)测定中的有效性和实用性。Stable carbon isotope ratio(δ^(13)C_(DIC))of dissolved inorganic carbon(DIC)in water is an important indicator for revealing the carbon cycle process.The separation-enrichment of DIC is the basis for the determination ofδ^(13)C_(DIC),and it is also one of the main processes that affect the measuring accuracy ofδ^(13)C_(DIC).Precipitation method and gas method are the commonly-used DIC separation-enrichment methods.Compared with gas method,precipitation method has the characteristics of simple operation and better applicability.Therefore,it has a wide application prospect in the determination ofδ^(13)C_(DIC).However,the problem of isotope fractionation often exists in the precipitation-based separation-enrichment process of DIC.In this paper,a response surface method,that considers the comprehensive advantages and disadvantages of the gas and precipitation methods and aims at minimizing the absolute error between the theoretical and measured values ofδ^(13)C_(DIC),was applied to improve the traditional NaOH-BaCl_(2) precipitation method.Based on the improved method,the absolute error between the theoretical and the measured values ofδ^(13)C_(DIC),and theδ^(13)C_(DIC) standard deviations of the parallel water samples of two urban rivers were 0.052‰,0.061‰and 0.037‰,respectively.These results showed the high accuracy and stability of the method in the determination ofδ^(13)C_(DIC).

关 键 词：溶解性无机碳 稳定碳同位素 改进沉淀法 响应面分析 

分 类 号：O658.9[理学—分析化学]