溶解有机碳同位素测定方法研究及其在九龙江的应用

发布时间：2018-07-11 13:10

  本文选题：DOC + δ13CDOC　； 参考：《国家海洋局第三海洋研究所》2015年硕士论文

【摘要】：碳循环是研究全球生物地球化学循环中最核心的一个环节,涉及到大气圈、陆地生物圈、水圈和岩石圈。河流作为连接地球上海洋和陆地这两个碳库最重要的纽带,是将陆地含碳物质输送到海洋的主要通道。因此,研究河流中碳循环过程对了解碳的生物地球化学循环过程具有重要意义,而稳定同位素技术则对研究碳的来源提供了技术手段。本文研究了一种能同时测定溶解有机碳(DOC)含量及其同位素(δ13CDOC)的方法——湿氧化-质谱法。该方法利用常规水化学的方法(湿氧化法),配合实验室现有在线制样装置(Gas Bench II)和稳定同位素质谱仪(IRMS),用于测定水体中DOC含量和δ13CDOC值。经过多次实验,在不同条件下对该方法进行分析测试其稳定性后,将其用于九龙江西溪和北溪与河口区表层水体中DOC含量及δ13CDOC值测定,并对其变化规律及来源进行了探讨,获得了以下几点认识:1.实验结果表明,湿氧化-质谱法对空白和DOC标准物质的同位素测试结果稳定,可以应用于DOC碳同位素的测定。该方法在1.0 ml氧化剂量、100℃氧化温度的条件下,DOC标准物质的碳回收率及δ13CDOC值稳定性较好,但δ13CDOC值受空白的影响都出现明显分馏。当DOC标准物质的浓度逐渐升高时,δ13CDOC值逐渐接近其真实值,但碳的回收率表现为降低的趋势。2.西溪表层水体DOC含量季节变化为春季(5.56 mg/L)高于夏季(3.38mg/L),δ13CDOC值表现为春季(-13.11‰)高于夏季(-15.38‰);空间变化为春季DOC含量和δ13CDOC值均沿河道逐渐递增,下游高于上游,夏季DOC含量和δ13CDOC值无明显变化趋势。北溪表层水体中DOC含量季节变化为春季(2.18mg/L)低于夏季(4.85 mg/L),δ13CDOC值为春季(-12.91‰)低于夏季(-12.37‰);空间变化为春夏季DOC含量沿河道从上游逐渐降低,在临近河口区时,含量有回升趋势;δ13CDOC值春季无明显变化趋势,夏季沿河道逐渐降低。3.河口区表层水体DOC含量季节变化为春季(5.13 mg/L)低于夏季(6.68mg/L);表层水体中δ13CDOC值为春季(-12.38‰)低于夏季(-8.74‰)。春夏季DOC含量和δ13CDOC值空间变化表现为随河道从上游地区到下游地区均呈升高趋势,在近海端均有高DOC含量和高δ13CDOC值。
[Abstract]:The carbon cycle is the core of the global biogeochemical cycle, involving the atmosphere, terrestrial biosphere, hydrosphere and lithosphere. As the most important link between the two carbon pools on the earth, rivers are the main way to transport carbon-containing matter from land to ocean. Therefore, the study of carbon cycling in rivers is of great significance in understanding the biogeochemical cycling process of carbon, while stable isotope technology provides a technical means for studying the source of carbon. A method for simultaneous determination of dissolved organic carbon (DOC) and its isotopes (未 13 CDOC) by wet oxidation-mass spectrometry has been studied. This method is used to determine DOC content and 未 13 CDOC value in water by conventional hydrochemical method (wet oxidation method), gas Bench II and stable isotope mass spectrometer (IRMS). After many experiments, the stability of the method was analyzed and tested under different conditions. The method was applied to the determination of DOC content and 未 13 CDOC value in the surface water of Xixi, Beixi and estuary areas of Jiulong River, and its variation law and source were discussed. The following points of understanding have been gained: 1. The experimental results show that the isotopic measurements of blank and DOC reference materials by wet oxidation-mass spectrometry are stable and can be applied to the determination of DOC carbon isotopes. The method has good stability of carbon recovery and 未 13 CDOC values of DOC standard materials at oxidation temperature of 100 鈩，

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