title: Effect of preservation on the δ¹³C value of dissolved inorganic carbon in different types of water samples.
abstract: Recent studies have shown that the stable carbon isotope compositions of dissolved inorganic carbon (δ(13)C(DIC)) of water samples preserved with HgCl(2) and CuSO(4) vary. Furthermore, mercury and cuprum compounds are toxic to the human or biological system and require proper waste disposal. To test the effect of preservation on the δ(13)C value of DIC in different types of water samples, a set of water samples with different DIC concentrations was preserved using different methods, including preserving with inhibitors (CuSO(4) or HgCl(2)), preserving under frozen conditions, filtering through a 0.4 μ m paper filter, and the DIC species precipitated in the form of solid BaCO(3). Our results show that δ(13)C(DIC) values of the samples preserved with CuSO(4) and HgCl(2) become more positive with increased storage time. The δ(13)C(DIC) of the water samples preserved under frozen conditions and the precipitated DIC as BaCO(3) are also more positive than original water samples. However, the δ(13)C values were relatively stable for up to 90 days in all water samples filtered through the 0.4 μ m paper filter and stored under cool conditions (0-4 °C). Therefore, we suggest that the better method for the storage of water samples is to filter the samples through a 0.4 μ m paper filter while out in the field and preserve them under cool conditions, thereby avoiding the use of preservatives.
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, IEE, CAS, Xi'an, People's Republic of China. lixiangzhong@ieecas.cn
authors.forename: Xiangzhong
authors.initials: X
authors.lastname: Li
authors.forename: Weiguo
authors.initials: W
authors.lastname: Liu
mesh_terms: D001464:Barium / Q000737:chemistry; D002244:Carbon / Q000032:analysis* / Q000737:chemistry; D002247:Carbon Isotopes / Q000032:analysis / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry; D019327:Copper Sulfate / Q000737:chemistry; D005374:Filtration / Q000295:instrumentation / Q000379:methods; D005615:Freezing; D006801:Humans; D008627:Mercuric Chloride / Q000737:chemistry; D011309:Preservation, Biological / Q000145:classification / Q000379:methods*; D013048:Specimen Handling / Q000145:classification / Q000379:methods*; D013997:Time Factors; D014867:Water / Q000032:analysis* / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D002254:Carbonates; D014867:Water; D001464:Barium; D008627:Mercuric Chloride; C006685:barium carbonate; D002244:Carbon; D019327:Copper Sulfate