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- Fleur de sel composition and production: analysis and numerical simulation in an artisanal salternPublication . Sainz, Noa; Boski, T.; DMR, SampathThis study is a first approach to modelling of fleur de sel production, aimed at increasing its efficiency and contributing to the scarce literature on the topic. Quantitative forecasting of daily production of fleur de sel was applied to an artisanal solar pond unit in the environmentally protected area of Castro Marim, SE Portugal. The numerical model was based on simulations of the evaporation process, taking into account the effect of reduced vapour pressure of the brine solution. The controlling variables chosen as input parameters to the forecast model were brine temperature, brine concentration, harvesting efficiency, albedo, incoming solar radiation, precipitation, air relative humidity, air temperature, atmospheric pressure, day of the year, wind direction, and wind speed. Production predicted by the model was tested against actual production in two crystallisers in the years 2015 and 2017. The statistically evaluated match between the estimated and actual production was highly significant with a mean R-2 of 0.8 and overall error of estimation was 14.5%. The chemical composition of nine samples of fleur de sel was analysed, showing the temporal evolution of several components during the harvesting period. A decrease of NaCl content from 96% to 87% and an increase by one order of magnitude of Mg, S, K, Br, and As were observed. The range of Ca, Si, Al, and Sr contents was 0.12-0.65%, 0.1-0.85%, 0.08- 0.3%, and 0.009-0.013%, respectively. Ba, Fe, Mn, Mo, Pb, and Sn contents had the following ranges: 0.051-0.145, 1.2-5.5, 0.44-1.66, 0.03-0.05, <0.05-0.55, and <0.05-0.1 mg/kg, respectively. The following elements were below the detection limit and below the limits of the Codex Alimentarius: Cd, Th, U, Cu, Cr, Co, Ni, V, Bi, Zn, Rb, and Hg.
- Morphological response of the saltmarsh habitats of the Guadiana estuary due to flow regulation and sea-level risePublication . Sampath, DMR; Boski, T.In the context of rapid sea-level rise in the 21st century, the reduction of fluvial sediment supply due to the regulation of river discharge represents a major challenge for the management of estuarine ecosystems. Therefore, the present study aims to assess the cumulative impacts of the reduction of river discharge and projected sea-level rise on the morphological evolution of the Guadiana estuary during the 21st century. The assessment was based on a set of analytical solutions to simplified equations of tidal wave propagation in shallow waters and empirical knowledge of the system. As methods applied to estimate environmental flows do not take into consideration the fluvial discharge required to maintain saltmarsh habitats and the impact of sea-level rise, simulations were carried out for ten cases in terms of base river flow and sea-level rise so as to understand their sensitivity on the deepening of saltmarsh platforms.Results suggest saltmarsh habitats may not be affected severely in response to lower limit scenarios of sea-level rise and sedimentation. A similar behaviour can be expected even due to the upper limit scenarios until 2050, but with a significant submergence afterwards. In the case of the upper limit scenarios under scrutiny, there was a net erosion of sediment from the estuary. Multiplications of amplitudes of the base flow function by factors 1.5, 2, and 5 result in reduction of the estimated net eroded sediment volume by 25, 40, and 80%, respectively, with respect to the net eroded volume for observed river discharge. The results also indicate that defining the minimum environmental flow as a percentage of dry season flow (as done presently) should be updated to include the full spectrum of natural flows, incorporating temporal variability to better anticipate scenarios of sea-level rise during this century. As permanent submergence of intertidal habitats can be significant after 2050, due to the projected 79 cm rise of sea-level by the year 2100, a multi-dimensional approach should be adopted to mitigate the consequences of sea-level rise and strong flow regulations on the ecosystem of the Guadiana Estuary. (C) 2016 Elsevier Ltd. All rights reserved.
- Modelling of estuarine response to sea-level rise during the Holocene: Application to the Guadiana Estuary-SW IberiaPublication . Sampath, DMR; Boski, T.; Loureiro, Carlos; Sousa, Carlos A. Mendes da Silva deThis paper focuses on simulations of the morphological evolution of an estuary during sedimentary infilling that accompanied Holocene sea-level rise. The simulations were conducted using the Estuarine Sedimentation Model, which uses a behaviour-oriented approach, supported by the chronostratigraphy of the estuary's sedimentary sequence. Behaviour curves were computed to represent the relationship between the estuarine channel depth below maximum high tide and the net accretion at a given location relative to the average sedimentation rate of the estuary during the Holocene. The model was validated by comparing the observed present-day bathymetry of the Guadiana River Estuary, southeastern Portugal, with the corresponding simulated bathymetries for nine control sections across the estuary. The best fit between simulated and actual sediment surface elevations was obtained along the cross-sections in the sheltered, low-energy environments of the estuary. The accuracy of the sedimentary stratigraphy of the best-fit model was further established using 16 radiocarbon ages obtained from five boreholes in the estuary. The present approach is particularly suitable for simulating long-term morphological evolution in sheltered estuarine environments where tidally driven vertical aggradation dominates at centennial to millennium timescales. However, the accuracy of simulated sediment surface elevations and consequently the robustness of behaviour-type models based on Geographical Information System platforms can be enhanced by incorporating (i) the impacts of nearshore hydrodynamic processes and episodic flood events in highly energetic channels, and (ii) the impacts of cross-currents in meandering channel sections. (C) 2015 Elsevier B.V. All rights reserved.
- Coastal responses to sea-level rise on centennial to millennial time scales: development of hybrid model-based forecasting for the Guadiana EstuaryPublication . Sampath, DMR; Boski, T.In the context of hybrid approach, this study was focused on formalizing and application of a simple and idealized model using a set of theoretical framework based on rule-based morphological expressions. Main objectives were: (1) to simulate the sedimentary infilling of the Guadiana Estuary palaeovalley due to eustatic sea-level rise during the Holocene, against previous geomorphological and post-glacial palaeoenvironmental reconstructions based on facies interpretation and 14C dating; (2) to assess potential morphological impacts and risk of habitat shift by simulating the morphological evolution of the Guadiana estuary and its intertidal zone for the worst case of sea level rise and sedimentation scenarios predicted for the 21st century; (3) to assess the sensitivity of bed friction coefficient, power index of the current velocity in the erosion rate function, river discharge, and sea-level rise rate in determining the decadal scale morphological evolution in the Guadiana estuary; and (4) To understand the effect of dam construction along the Guadiana river on the estuarine morphology. According to the results, the long-term modelling of the morphological evolution in the estuary due to sea-level rise during the Holocene complemented previous reconstructions, based on interpretations of the experimental data. The intermediate hybrid approach that was followed in this study appears to be a useful tool for simulating the morphological evolution of an estuarine system during the period of postglacial sea-level rise. It seems particularly suited to the more sheltered environments of an estuarine system where vertical aggradation dominates the sedimentary infilling of the palaeovalley. However, the direct application of Estuarine Sedimentation Model and the intermediate hybrid model, are very much applicable to a system where there is net accretion throughout the estuarine system. These constraints were compensated to a certain extent using the fully developed hybrid model as it was able to produce elevation change distribution from 2000 to 2014 in the Guadiana estuary, approximately similar to the observed normal probability distribution for the same period. This improved model was able to produce spatial variability of eroding and accreting regions, enabling the coupling of decadal scale model to centennial scale model. Furthermore, results indicate the deficiencies of defining the environmental flow as a percentage of dry season flow and the risk of habitat loss from the intertidal zone. Thus, a multi-dimensional approach has to be adopted to mitigate their consequences of sea-level rise and drastic flow regulations on the ecosystem of the Guadiana estuary.
- Impact of shoreline retreat and inundation due to sea level rise along the coastline adjacent to the Guadiana estuary, Portugal/Spain borderPublication . Sampath, DMR; Boski, T.The integrated impact assessment of shoreline retreat and inundation due to sea level rise over the coastal zone of the Guadiana estuary, Portugal/Spain border was carried out to identify and map hazard zones. Geographical Information System tools were used to visualize and analyse impacts on built-up area, transportation network and habitats. The shoreline retreat with the present shoreline evolution rate and the accelerated sea level rise given by three SRES scenarios, namely, B1, A1B and A1FI (upper-bound values: 38, 48 and 59 cm rise in sea level, respectively) exhibit high spatial variability. The adjacent coastline of Monte Gordo tourist beach (Portugal) and the entire shoreline of Ayamonte municipality (Spain) are susceptible to severe erosion. The erosion extent increases gradually with the sea level rise. However, the main forcing of the shoreline retreat is not the climatic change but anthropogenic interventions including construction of coastal defense structures. The first order assessment of shoreline retreat for a hypothetical storm surge with elevated flood contours due to sea level rise shows that the damage to the built-up area and urban habitat can be long lasting while the sandy dune and salt marsh habitats may have resilience depending on sediment supply. The vulnerability of Portuguese side of the Guadiana estuary coastal zone for inundation due to storm surges of 3.0 and 4.9 m from mean sea level (1 and 2 m from the maximum spring high tide level, respectively) shows approximately two-fold and four-fold increase, respectively, relative to the hazard zone marked by the maximum spring high tide (1.9 m from MSL). Two- and three-fold respective increase can be seen in Spain side of the estuary. However, in terms of total area of inundation, Spanish side would severely affect. The main response should be focused on Integrated Coastal Zone Management programme with strategically planned soft engineering interventions to mitigate the negative impacts of shoreline retreat due to sea level rise hazards.