Analytical pyrolysis (Py-GC/MS) discriminates main organic matter inputs to intertidal sediments of Ria Formosa salt marshes lagoon (South, Portugal)
The provenance and molecular composition of organic matter (OM) are key to understand biogeochemical cycling of carbon in coastal wetlands. Here we provide a detailed fingerprinting of OM from Ria Formosa intertidal sediments covering salt marshes vegetation and mudflats (Fig. 1.). We analysed three transects (5T, 15T, and 25T) core sediments from different locations using analytical pyrolysis techniques (Py-GC/MS) to improve our understanding of intertidal sedimentary organic matter molecular properties and their preservation. Major biomarker classes detected by direct analytical pyrolysis of the core sediment samples encompassed homologous aliphatic (n-alkanes, n-alkanoic acids and n-alkan-2-ones) series, polycyclic aromatic hydrocarbons (PAHs), hopanes, steranes and linear alkylbenzenes (LABs). Unimodal, bimodal and trimodal n-alkane distributions were observed in chain length ranging from C10 - C34 and predominance of C13, C23, C25, and C29 chain length homologues with only one sample (T1 0-10 cm) having an even carbon number (C22, C24, C26 and C28) predominance for n-alkanes. Long-chain n-alkanes (C27-C31) were found in relatively lower abundance compared to mid (C21-C25) and short chain n-alkanes (C10-C20). Retene biomarker was found with high abundance, this is a natural PAH and a diagenetic products of resinous pine. The study of calculated geochemical indexes such as carbon preference index (CPI), odd/even predominance (OEP), the proportion of aquatic ratio (Paq) to terrigenous (TAR), indicate that, although major OM sources are of terrigenous origin, in some areas of the marsh lagoon of Ria Formosa, algal and aquatic macrophyte OM inputs are also relevant. Analytical pyrolysis was also able to identify anthropogenic sources of contamination i.e. petroleum/oil spills OM sources characterized by CPI values close to unity and signals of highly unresolved mixture of products (HUMP). The occurrence of methylated polycyclic aromatic hydrocarbons (PAHs) together with hopanes (C29 - C36) and steranes (C27- C29) biomarkers also supported the oil spills/petroleum contamination. OM. Another pollution source, probably urban sewages, is also detected and reflected in well resolved series of linear alkylbenzenes (LABs) (Fig. 2) and FAs (Palmitic C16:0 and oleic C18:1 acids) present in the core sediments. Our findings highlight the utility of the Py-GC/MS technique for OM fingerprinting of and the detection of biomarkers surrogated to the sedimentary OM origin. This is a unique tool for discerning between natural and anthropogenic sources and for assessing and monitoring the health status of areas with high environmental value, mainly those close to highly populated areas and prone to degradation.
| Main Authors: | , , , , |
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| Format: | comunicación de congreso biblioteca |
| Published: |
Nagoya Institute of Technology (Japan)
2018-06-03
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| Online Access: | http://hdl.handle.net/10261/180461 |
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