Hydrological catchment analysis from characterisation of organic matter in stream water

University essay from Göteborgs universitet/Institutionen för geovetenskaper

Abstract: Organic matter (OM) in aquatic systems is a complex field which have rapidly developed duringthe last decade due to the introduction of high resolution mass spectrometers. The compositionof OM in the aquatic environment is directly dependent on factors such as oxygen supply, pHand the flow rate in the local system. Furthermore, the OM is closely linked to negative effectson these systems such as eutrophication and brownification, which in many cases are causedby human activity through climate change, water management and changes in land use patterns.This thesis focuses on the composition of organic matter in the aquatic environment in relationto land use and water management. The aim of this work is characterising of OM from waterdraining distinctly different sub-catchments and using the internal OM composition as a tracerfor different catchment characteristics. Stream water was sampled and analysed for OM usingdirect-sample-analysis Time-of-flight mass spectrometry (DSA-TOF-MS) and Total-organiccarbon(TOC) analysis from streams draining the different sub-catchments. The results werethen linked to the different sampling locations through comparisons of mass spectra, Principlecomponentstatistics and molecular formula correlations. The result show that three differentsub-catchments could be distinguished by OM quantification and characterisation. However, itwas not possible use characterised mass peaks as a downstream tracer, which can probably beexplained by the complex degradation, transformation and sedimentation processes interactingwith the OM in the catchment. Improved methodology and further studies to map the processesaffecting the OM in the aquatic system is necessary to be able to use the internal organicchemistry as a marker for the status of the system.

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