TÓPICOS ESPECIAIS EM GEOQUÍMICA AMBIENTAL I: BIOMARKERS AS PROXIES OF PAST ENVIRONMENTS AND CLIMATE

Nome da Disciplina: TÓPICOS ESPECIAIS EM GEOQUÍMICA AMBIENTAL I: BIOMARKERS AS PROXIES OF PAST ENVIRONMENTS AND CLIMATE

Carga Horária: 30

Créditos: 2

Obrigatória: Não

The aim of this course is to provide a solid foundation into the principles and the applications of molecular biomarkers as proxies for reconstructing past environments and climatic conditions. After a brief history of the organic geochemistry as a « young » discipline, from its development in the mid-2Oth century into the role it plays today in geosciences, we will review fundamental concepts with emphasis on organic matter production, cycling, and preservation in sedimentary archives (and links to the Carbon cycle). We will examine the composition of organic matter with a focus on the lipid molecular components, their biological sources, biochemistry and role, the major chemical structures and functional groups, and their environmental fate. We will introduce the concept of lipid biomarkers as « fossil chemicals » that encode information about past biodiversity, environmental conditions/climate, biogeochemical processes. We will examine the relationships between the occurrence, distribution, and/or isotopic composition of lipid biomarkers and environmental parameters in modern systems. Such relationships set the basis for using biomarkers as molecular proxies to reconstruct past environments and climates. We will then present and discuss principles, developments and applications of molecular proxies as proxies for past : a) sea surface temperatures (paleothermometry) ; continental temperatures ; b) continental vegetation, marine productivity c) land-ocean interactions Apart from the structural aspects we will also deal with the carbon and deuterium isotopic composition (δ13C, δD) of biomarkers and show how compound-specific isotopic records are increasingly used to reconstruct past hydrological changes, vegetation shifts, pCO2 levels, food web structure, methane cycling... Finally, we will demonstrate the profound importance of analytical chemistry as a probe into fundamental geological and/or environmental research questions on the co-evolution of life and the environment of our planet. We will review methodological steps for biomarker analysis, from a raw natural sample to instrumental analysis at the molecular level. Principal analytical techniques will be presented (GC, GC-MS, GC-ir-MS, HPLC-MS).

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