ZHU Mengbo1,2, SONG Jianzhong1, PENG Pingan1
(1. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;
2. Graduation School of the Chinese Academy of Sciences, Beijing 100039, China)
Abstract：As important properties of soils, sediments and atmospheric dust, it is very important to accurately quantify the total organic carbon (TOC) contents and stable carbon stable carbon isotope (δ13C) in these samples. In fact, the pretreatment procedures may have certain impacts on the measured results of TOC and δ13C. In this study, the influences of pretreatment procedures on the determination of TOC and δ13C in different samples were investigated by two ways: acid treatments and dry methods. The tested acid treatment procedure includes hydrochloric acidification/separation, infrared carbon and sulfur crucible, and in-situ Ag cup acidification. The tested drying method include heat drying and vacuum freeze drying. Results show that the acid treatment has important effects on the determination of TOC in different samples. The TOC values determined using methods of hydrochloric acidification/separation method but reserving residual acid and in-situ Ag cup acidification are significantly higher than those of other groups, especially for the atmospheric dust sample which increased 20% of TOC. These differences can be explained by the fact that dissolved organic carbons (DOC) are removed during the acid treatment process. The δ13C values determined with these two methods are slightly positive than those of other groups, especially for surface soil samples those increase around 0.8‰-2‰. However the drying method of heat drying and vacuum freeze drying does not have observable effects on the determination of TOC and δ13C in different samples, which may indicate that the influences of volatile organic carbon (VOC) on the determination of TOC and δ13C in these tested samples are ignorable. In summary, the in-situ Ag cup acidification method has many advantages such as time saving, operation easy, and more accurate, thus it may be a good method to measure the TOC contents and δ13C in different samples, especially for the samples with high levels of DOC.
Key word: total organic carbon content, δ13C value, Ag cup acidification, dissolved organic carbons
EARTH AND ENVIRONMENT Vol. 43, No.4, Tot No.306, 2015, Page 476
