Soil Organic Matter (SOM) characterisation and biogeochemistry of variable-charge soils

  1. Manuel Suárez Abelenda
Dirixida por:
  1. Marta Camps Arbestain Director
  2. Felipe Macías Vázquez Director

Universidade de defensa: Universidade de Santiago de Compostela

Ano de defensa: 2013

  1. Carmen Monterroso Martínez Secretaria
  2. Manuel Madeira Vogal
  3. Francisco Javier González Vila Vogal
  4. Roque Ortiz Silla Vogal
  5. Florencio Arce Vázquez Vogal
  1. Departamento de Edafoloxía e Química Agrícola

Tipo: Tese


In chapter 2, we investigated soils that differed in the abundance of organo-Al complexes to determine the effect of such binding on SOM chemistry. For this, the surface horizons of three types of acid soils in the Basque Country (northern Spain) under forest stands were studied: (i) Alu-andic Andosols (AND soils) on basalts and trachytes, (ii) Umbrisols or so-called `aluminic¿(ALU) soils also on basalts and trachytes and (iii) soils with a podzolizing trend (POD), on quartzites. NaOH- extractable SOM was studied by Py-GC/MS. Soils derived from quartz-rich parent material had the largest loads of plant-derived markers. SOM of the Alu-andic Andosols had the smallest amounts of plant-derived SOM and the largest amounts of microbial products. ALU soils had an intermediate pattern. In chapter 3, samples from a black C- rich colluvial soil in NW Spain were subjected to K2Cr2O7 and KMnO4 oxidation and the residual SOM was NaOH-extracted and analyzed using Py-GC/MS and 13C CP/MAS NMR in order to study the susceptibility of different SOM fractions towards these oxidation agents. KMnO4 promotes the oxidation of carbohydrate products, mostly from (i) microbial SOM and (ii) a resistant lignocellulose fraction, causing a relative enrichment of aliphatic moieties and aromatic black C structures. K2Cr2O7 oxidation left black C, N-containing black C markers and aliphatic structures. In chapter 4, a semi-arid mangrove-dominated estuary system in the Northeast Brazilian coast was selected for this study. The main objective of the study was to determine the impact of shrimp farm wastewater effluents on the geochemistry and the organic carbon (OC) storage of this soils and estimate the total amount of OC stored. We hypothesized that the decrease in OC storage in wastewater-affected soils is due to (i) an increase in microbial activity caused by the loading of rich-nutrient effluents, and (ii) a decrease in pyrite - and thus in that of soil OC burial - triggered by oxidation in presence of NO3-.