土壤中总有机碳环境标准样品研制

土壤环境标准样品是土壤生态环境监测质量控制的重要技术工具。目前,土壤中总有机碳环境标准样品仍为中国环境标准样品体系的空缺,特别是配套燃烧氧化-非分散红外法的土壤标准样品一直未曾问世。本文以有机碳含量较高的农用地土壤为原材料,经干燥、研磨、混匀、装瓶、灭菌等加工步骤,制备获得土壤中总有机碳环境标准样品。分层随机抽取10瓶样品进行均匀性检验,经评价统计量F小于临界值F_(0.05)(9,10),瓶间均匀性相对不确定度(u_(bb))为1.5%,样品均匀性良好。在室温避光保存条件下,对样品进行了18个月的稳定性检验,稳定性相对不确定度(u_(lts))为1.2%,样品具有良好稳定性。由中国11家实验室采用燃烧氧化-非分散红外法和重铬酸钾容量法进行协作定值,通过对检测结果的数理统计分析,样品量值评定结果为(25.2±1.4)mg/g。该标准样品为采用燃烧氧化-非分散红外法参与定值的土壤中总有机碳环境标准样品,可作为土壤中总有机碳测定标准方法配套的实物标准,满足土壤生态环境监测及相关研究需求,且与国外同类样品具有可比性。

Preparation and Certification of a Soil Total Organic Carbon Reference Material

BACKGROUND: Soil environmental reference materials are important technical tools for the quality control of soil environmental monitoring. However, there is no self-developed environmental matrix reference material with total organic carbon (TOC). In particular, a soil standard sample supporting the combustion oxidation-non-dispersive infrared method has not been developed yet.OBJECTIVES: To develop a soil TOC reference material that can support standard methods for the determination of TOC in soil.METHODS: Agricultural land soil with a high organic carbon content was selected as the raw material. The soil TOC reference materials were prepared after drying, grinding, mixing, bottling, and sterilization. Ten bottles of the reference materials were randomly sampled in layers, and their homogeneities were determined using combustion oxidation-non-dispersive infrared (NDIR) absorption method. The data were assessed using a single element analysis of variance. The reference material was stored at room temperature, and its stability was determined for 18 months. The test results were assessed using a linear fitting model. Eleven laboratories were organized as the cooperation to determine the TOC content of the prepared reference material using combustion oxidation-NDIR absorption method and potassium dichromate volumetric method. All measurement data were statistically analyzed to obtain the certified value and uncertainty of the reference material.RESULTS: The soil TOC reference material exhibited good homogeneity and stability. After evaluation, the F value was determined to be less than the critical value of F_0.05 (9, 10). Additionally, the relative uncertainty (u_bb) of the uniformity between bottles was 1.5%, and the sample exhibited good uniformity. The stability uncertainty was 1.2%, which indicated good stability. The certified value of the soil TOC reference material was determined to be (25.2±1.4)mg/g, using the grand mean of the collaborative determination results from multiple laboratories.CONCLUSIONS: A soil TOC reference material was developed using combustion oxidation-NDIR absorption method. This reference material can be used to support the standard determination methods of TOC in soil and meets the requirements of the studies on TOC content in soil. Moreover, it is comparable with similar foreign samples.