title: Selenium fractions in organic matter from Se-rich soils and weathered stone coal in selenosis areas of China.
abstract: A high degree of association between Selenium (Se) and organic matter has been demonstrated in natural environments, but Se fractions and speciation in organic matter is unclear. In this study, a method for quantifying organic matter associated with Se (OM-Se) was developed to investigate Se fractions in organic matter in Se-rich soils and weathered stone coal from Enshi, China, where Se poisoning of humans and livestock has been documented. Initially, Se was extracted using water and a phosphate buffer. Subsequently, OM-Se was extracted using NaOH, and then speciated into Se associated with fulvic acids (FA-Se) and humic acids (HA-Se). Both FA-Se and HA-Se were further speciated into the weakly bound and strongly bound fractions using a customized hydride generation reactor. The results show that FA-Se (1.91-479 mg kg(-1)) is the predominant form of Se in all Se-rich soils and the weathered stone coal samples, accounting for more than 62% of OM-Se (3.07-484 mg kg(-1)). Weakly bound FA-Se (1.33-450 mg kg(-1)) was prevalent in the total FA-Se, while weakly bound HA-Se (0.62-26.2 mg kg(-1)) was variable in the total HA-Se (1.15-32.5 mg kg(-1)). These data indicate that OM-Se could play a significant source and sink role in the biogeochemical cycling of Se in the supergene environment. Weakly bound FA-Se seems to act as a potential source for bioavailable Se, whereas strongly bound HA-Se is a possible OM-Se sink which is not readily transformed into bioavailable Se.
authors: State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China.
authors: Hai-bo
authors: HB
authors: Qin
authors: Jian-ming
authors: JM
authors: Zhu
authors: Hui
authors: H
authors: Su
mesh_terms: D001578:Benzopyrans / Q000737:chemistry; D002681:China; D003031:Coal / Q000032:analysis*; D018556:Crops, Agricultural; D004785:Environmental Pollutants / Q000032:analysis* / Q000506:poisoning*; D005308:Fertilizers / Q000032:analysis; D006812:Humic Substances / Q000032:analysis; D009930:Organic Chemicals / Q000737:chemistry*; D012643:Selenium / Q000032:analysis* / Q000506:poisoning*; D012987:Soil / Q000737:chemistry*
chemical_list: D001578:Benzopyrans; D003031:Coal; D004785:Environmental Pollutants; D005308:Fertilizers; D006812:Humic Substances; D009930:Organic Chemicals; D012987:Soil; D012643:Selenium; C005023:fulvic acid