Comparison of the quantitative determination of soil organic carbon in coastal wetlands containing reduced forms of Fe and S

Autor(es)

Passos, Tassia R. G. ^[1] ; Artur, Adriana G. ^[1] ; Nobrega, Gabriel N. ^[2] ; Otero, Xose L. ^[3] ; Ferreira, Tiago O. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Fed Ceara, Dept Soil Sci, A Mister Hull 2977, BR-60440554 Fortaleza, Ceara - Brazil

^[2] Univ Sao Paulo, Luiz de Queiroz Coll Agr, Dept Soil Sci, Ave Padua Dias 11, BR-13418260 Piracicaba, SP - Brazil

^[3] Univ Santiago de Compostela, Fac Biol, Dept Edaphol & Agr Chem, Santiago De Compostela 15782 - Spain

• Tipo de documento: Artigo Científico
• Fonte: GEO-MARINE LETTERS; v. 36, n. 3, p. 223-233, JUN 2016.
• Citações Web of Science: 4

Resumo

The performance of the Walkley-Black wet oxidation chemical method for soil organic carbon (SOC) determination in coastal wetland soils (mangroves, coastal lagoons, and hypersaline tidal flats) was evaluated in the state of Ceara along the semiarid coast of Brazil, assessing pyrite oxidation and its effects on soil C stock (SCS) quantification. SOC determined by the chemical oxidation method (C-WB) was compared to that assessed by means of a standard elemental analyzer (C-EA) for surficial samples (< 30 cm depth) from the three wetland settings. The pyrite fraction was quantified in various steps of the chemical oxidation method, evaluating the effects of pyrite oxidation. Regardless of the method used, and consistent with site-specific physicochemical conditions, higher pyrite and SOC contents were recorded in the mangroves, whereas lower values were found in the other settings. C-WB values were higher than C-EA values. Significant differences in SCS calculations based on C-WB and C-EA were recorded for the coastal lagoons and hypersaline tidal flats. Nevertheless, the C-WB and C-EA values were strongly correlated, indicating that the wet oxidation chemical method can be used in such settings. In contrast, the absence of correlation for the mangroves provides evidence of the inadequacy of this method for these soils. Air drying and oxidation decrease the pyrite content, with larger effects rooted in oxidation. Thus, the wet oxidation chemical method is not recommended for mangrove soils, but seems appropriate for SOC/SCS quantification in hypersaline tidal flat and coastal lagoon soils characterized by lower pyrite contents. (AU)

• Processo FAPESP: 14/11778-5 - Solos subaquáticos de pradarias marinhas (seagrass bed) do Brasil: biogeoquímica, gênese e classificação
• Beneficiário: Gabriel Nuto Nóbrega
• Modalidade de apoio: Bolsas no Brasil - Doutorado