As an important part of the global carbon cycle, dissolved inorganic carbon (DIC) concentration and its stable carbon isotopic composition (δsup.13Csub.DIC) have been used to constrain the sources of ...DIC in rivers. In this study, we systematically investigated the water chemistry, DIC contents, and δsup.13Csub.DIC values in a tropical agricultural river in northeast Thailand. The water temperature ranged from 20.3 to 31.3 °C, and water pH values ranged from 6.4 to 8.4, with seasonal variations. Based on the major ion compositions, the hydro-chemical type of the Mun River water was a unique Na–Ca–Cl–HCOsub.3 type, controlled by evaporite and silicate weathering. Seasonal variation of DIC concentrations and its carbon isotopic composition was obvious; DIC and δsup.13Csub.DIC were significantly lower in the wet season (135 to 3146 μmol/L and −31.0‰ to −7.0‰) compared to the dry season (185 to 5897 μmol/L and −19.6‰ to −2.7‰). A high level of sup.12C-enriched DIC/COsub.2 from soil respiration and organic matter oxidation may cause the low pH values, δsup.13Csub.DIC values, and high partial pressure of COsub.2 (pCOsub.2) in the middle and lower reaches during the wet/rainy season compared to the dry season. This may be responsible for the seasonal and spatial variations of DIC concentrations and δsup.13Csub.DIC values in the Mun River. According to the relationship between pCOsub.2 and δsup.13Csub.DIC values, COsub.2 outgassing may be more significant in the dry season, due to the greater influx of groundwater with higher pCOsub.2 levels; and the rapid COsub.2 diffusion into the atmosphere will continuously increase the δsup.13Csub.DIC values and decrease pCOsub.2 levels. These results show that riverine biologic effects and COsub.2 outgassing play important roles in the DIC and δsup.13Csub.DIC evolution of this typical agriculturally-dominated watershed.
This thesis develops analytical frameworks for evaluating the validity of MBES data with comparable ground truthing and hydrodynamic data with respect to geomorphology and marine biodiversity in two ...Special Areas of Conservation (SAC) in the Malin-Hebrides Sea off the north-Irish coast. First, a modelling framework based on Generalised Linear Modelling (GLM) is developed to test the validity of multi-frequency MBES backscatter data (30, 95, 300 kHz) to characterise sediment grain size in the Hempton's Turbot Bank (HTB) SAC. The results demonstrate that the single-frequency sources have a marginal gain on the multi-frequency model, with the 30 kHz model driving the significance of the multi-frequency model, and the inclusion of the higher frequencies diminishes the level of agreement. Secondly, a combination of K-Means unsupervised classification and GLM based on MBES backscatter (95, 300 kHz) and bathymetry analysis are successfully used to predict different levels of sandeel Hyperoplus lanceolatus densities with respect to geomorphology in the HTB SAC. The study demonstrates that the lower frequency source is more adept at capturing the variety inherent in shallow sub-surface sedimentary environments, which this species prefers. Finally, multidisciplinary modelling and analysis approaches using MBES data, hydrodynamic data and theodolite tracking observations are used to assess the spatial dynamics of harbour porpoise Phocoena phocoena in the Skerries and Causeway SAC. Generalised Additive Modelling (GAM) identifies that slope, aspect and backscatter intensity are the most statistically significant variables accounting for the highest deviance in porpoise sighting density. Models predict a high probability (> 0.6) of porpoise encounters in nearshore areas, particularly concentrated around headlands where local flow acceleration results in coarser beds. The robust workflows developed in this thesis, provides a proof of concept for developing robust monitoring strategies for Marine Protected Areas and associated species. Respective recommendations will inform marine policy, marine spatial planning and management.
This textbook describes some of the most effective and straightforward quantitative techniques for modeling Earth surface processes. By emphasizing a core set of equations and solution techniques, ...the book presents state-of-the-art models currently employed in Earth surface process research, as well as a set of simple but practical research tools. Detailed case studies demonstrate application of the methods to a wide variety of processes including hillslope, fluvial, aeolian, glacial, tectonic, and climatic systems. Exercises at the end of each chapter begin with simple calculations and then progress to more sophisticated problems that require computer programming. All the necessary computer codes are available online at www.cambridge.org/9780521855976. Assuming some knowledge of calculus and basic programming experience, this quantitative textbook is designed for advanced geomorphology courses and as a reference book for professional researchers in Earth and planetary science looking for a quantitative approach to Earth surface processes.
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