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Inter-comparison of data products from simultaneous measurements performed with independent systems and methods is a viable approach to assess the consistency of data and additionally to investigate uncertainties. Within such a context the inter-comparison called Assessment of In Situ Radiometric Capabilities for Coastal Water Remote Sensing Applications (ARC) was carried out at the Acqua Alta Oceanographic Tower in the northern Adriatic Sea to explore the accuracy of in situ data products from various in- and above-water optical systems and methods. Measurements were performed under almost ideal conditions, including a stable deployment platform, clear sky, relatively low sun zenith angles and moderately low sea state. Additionally, all optical sensors involved in the experiment were inter-calibrated through absolute radiometric calibration performed with the same standards and methods. Inter-compared data products include spectral waterleaving radiance L-w(lambda), above-water downward irradiance E-d(0(+),lambda) and remote sensing reflectance R-rs(lambda). Data products from the various measurement systems/methods were directly compared to those from a single reference system/method. Results for R-rs(lambda) indicate spectrally averaged values of relative differences comprised between - 1 and +6 \%, while spectrally averaged values of absolute differences vary from approximately 6\% for the above-water systems/methods to 9 \% for buoy-based systems/methods. The agreement between R-rs(lambda) spectral relative differences and estimates of combined uncertainties of the inter-compared systems/methods is noteworthy.

In situ incubations of sediment with overlying water provide valuable and consistent information about benthic fluxes and processes at the sediment-water interface. In this paper, we describe our experiences and a variety of applications from the last 14 years and 308 deployments with the Gothenburg benthic chamber lander systems. We give examples of how we use sensor measurements for chamber leakage control, in situ chamber volume determination, control of syringe sampling times, sediment resuspension and stirring quality. We present examples of incubation data for in situ measurements of benthic fluxes of oxygen, dissolved inorganic carbon, nutrients, metals and gases made with our chamber landers, as well as manipulative injection experiments to study nitrogen cycling (injections of 15N nitrate), phosphate retention (injections of marl suspension) and targeted sediment resuspension. Our main goal is to demonstrate the possibilities that benthic chamber lander systems offer to measure solute fluxes and study processes at the sediment-water interface. Based on our experience, we recommend procedures to be used in order to obtain high quality data with benthic chamber landers.

At the end of 2014, a Major Baltic Inflow (MBI) brought oxygenated, salty water into the Baltic proper and reached the long-term anoxic Eastern Gotland Basin (EGB) by March 2015. In July 2015, we measured benthic fluxes of phosphorus (P), nitrogen (N) and silicon (Si) nutrients and dissolved inorganic carbon (DIC) in situ using an autonomous benthic lander at deep sites (170–210 m) in the EGB, where the bottom water oxygen concentration was 30–45 μM. The same in situ methodology was used to measure benthic fluxes at the same sites in 2008–2010, but then under anoxic conditions. The high efflux of phosphate under anoxic conditions became lower upon oxygenation, and turned into an influx in about 50% of the flux measurements. The C:P and N:P ratios of the benthic solute flux changed from clearly below the Redfield ratio (on average about 70 and 3–4, respectively) under anoxia to approaching or being well above the Redfield ratio upon oxygenation. These observations demonstrate retention of P in newly oxygenated sediments. We found no significant effect of oxygenation on the benthic ammonium, silicate and DIC flux. We also measured benthic denitrification, anammox, and dissimilatory nitrate reduction to ammonium (DNRA) rates at the same sites using isotope-pairing techniques. The bottom water of the long-term anoxic EGB contained less than 0.5 μM nitrate in 2008–2010, but the oxygenation event created bottom water nitrate concentrations of about 10 μM in July 2015 and the benthic flux of nitrate was consistently directed into the sediment. Nitrate reduction to both dinitrogen gas (denitrification) and ammonium (DNRA) was initiated in the newly oxygenated sediments, while anammox activity was negligible. We estimated the influence of this oxygenation event on the magnitudes of the integrated benthic P flux (the internal P load) and the fixed N removal through benthic and pelagic denitrification by comparing with a hypothetical scenario without the MBI. Our calculations suggest that the oxygenation triggered by the MBI in July 2015, extrapolated to the basin-wide scale of the Baltic proper, decreased the internal P load by 23% and increased the total (benthic plus pelagic) denitrification by 18%.

The KB186 well (GSB 047W0264, Lommel-Kerkhoven) is situated in the northern part of the Campine Basin (NE Belgium) to the west of the Donderslag fault and has been studied and sampled in detail from a depth of 1182.72 meters to 1197.75 metres. The objective is to examine the sedimentological, petrographical, mineralogical and petrophysical characteristics and their variations within and between two cyclothems. 17 shale samples were taken throughout the entire section, varying from roof shales, over dark organic-rich shales with siderite enrichments, to bluish-grey shales without no visible organic content. Two sedimentary cycles have been recognised. Macroscopically, they show some similarities and differences in facies and sedimentological trends. Both are approximately 6.5 metres thick and contain sections of mainly shale deposits (with or without siderite enrichments). Fining-upwards sequences of fine sand and clayey silt and larger sandstone bodies occur between these shale-rich sections. A petrographical assessment by means of optical light and electron microscopy is conducted for a qualitative analysis of the mineralogical composition and diagenetic history, while a quantitative determination is made by means of x-ray diffractometry. Important mineralogical reservoir parameters are the relative amounts of silica and quartz, and the clay mineralogy with special attention to smectite and illite.

Acoustic interaction theory and observation highlight the strong relation between the acoustic signal responses and the physical and biological processes acting on the seafloor and in the water column. Several descriptors such as sediment texture, porosity and surface roughness are identified as the main factors affecting the acoustic reverberation and backscatter signals. Shells can influence if not dominate the scattering on the seafloor(Jackson et al., 1986; Stanic et al., 1989 and Zhang, 1996). Scattering from both inclusions and partially buried shells on the sea-floor is described by Stanton (2000), and scattering from shells as a potential mechanism explaining the scattering above 200 kHz is highlighted by Ivakin (2009). In order to improve the knowledge on this matter, several institutions with different expertise are cooperating to integrate mathematical modeling and experimental results to better quantify the influence of shells and shell debris on the acoustic signal and scattering of sonar images. Mathematical 3D models of shell objects in a sediment matrix will be used to simulate the influence of the shells on acoustic signal and scattering. The physical arrangements of shells and their spatio-temporal population trends are also considered in the modeling. The models will be supported by direct sonar measurements of seafloor areas on the Belgian Continental Shelf, combined with sampling, visual observations, classification and shape analysis of the shells and shell debris.

The development of geothermal energy is below the European National Renewable Energy Action Plans' anticipated trajectory. For deep geothermal energy projects in particular, multiple sources of uncertainty in combination with high upfront investment costs result in a major investment risk, hampering the mobilization of required capital (Compernolle et al., 2019). The uncertainty sources include market uncertainty, uncertainty regarding new technologies and uncertainty inherent to working with subsurface data. The objectives of the DESIGNATE project for deep geothermal systems in Belgium, including applications in abandoned mines are two folds. First, to create tools for integrated forecasts under uncertainty and second to set-up a methodological framework for territorial Life Cycle Analysis (LCA) considering surface and subsurface impacts. To do so, analytical reservoir models will be developed to assess the effect of uncertainties about geological data and concepts on the performance and impact of the geothermal applications. These will be coupled with a techno-economic analysis in combination with a territorial, environmental life cycle analysis. To evaluate the impact of different policy measures, the techno-economic analysis consists of a Monte Carlo simulation model that integrates both market and geological uncertainties and a project developers' option to wait or abandon the geothermal project development at different steps in the development of the project (Welkenhuysen et al., this conference). As a preliminary step, the influence of the rollout time of a heat network on the risk and on the profitability is investigated. At the start often only a part of the district heating network is in place at the time of commissioning and the geothermal plant operates at much lower capacity. Part of the capacity is foreseen for district heating networks linked to residential districts expected to be built or renovated in the near future. In this research, the change in income of a project considering a stepwise rollout of a district heating network compared to a full load from the start, in combination with a reduced maximum capacity of the geothermal plant compared to the expected output is calculated. This is done with a simplified spreadsheet techno-economic model, limiting variability to the rollout scenarios. For the calculation, data provided by the project developer HITA of the Turnhout NW geothermal project is used. In the next section the four cases used to evaluate the risk and profitability linked to the changes in the rollout time of a heat network are described. In the first case, the base case, the production plant is assumed to work at full capacity once the construction of the geothermal plant is achieved. Full capacity means that the production plant will be working at 100% during the heating season. Additional production for cooling or for heat storage in summertime are not taken into account. The second case considers that the maximum production capacity is 20% lower than in the first case due to lower-than-expected reservoir temperature or flow rate. In the third case, the full capacity is equal to the one of the base case but will be reached in three steps, simulating a growing demand by adding new district heating networks. The demand is expressed as a percentage of the expected maximum production capacity of the geothermal plant. At the start of production, the geothermal plant runs at 50%. After 5 years this is increased to 75% and after 10 years full capacity is reached. The fourth and last case is similar to the third case, with a stepwise increase of the demand, but the maximum production capacity is, as in second case, 20% lower. Because the demand is lower than the total capacity in the first 10 years, the production plant will however be able to supply the required energy. Only after 10 years when the demand rises to the expected maximum production capacity, only 80% of the required energy can be delivered without additional investments. As such, the income of the project will be the same the first 10 years compared to the third case. In a best-case scenario, demand and rollout of a district heating network will be fast and the production plant will run at full capacity during the heating season from the start (case 1). This is however unlikely and assuming this to be the base case will result in many projects not reaching predetermined targets, as the income of the project will be lower during the first years of production. In this respect, the third case or a similar scenario is a better option to use as a base case. This will put more stringent conditions on the expected output parameters of the production well to ensure an economic viable project, and hence provide a more realistic outlook. When using case 3 as the base case this also has the complementary benefit of reducing the risk related to the maximum production capacity. If the real maximum production capacity is lower than expected, the reduction of income will be lower than the decrease in the maximum production capacity. In other words, a reduction of 20% of the maximum production capacity will not lead to a reduction of 20% of the income, but will be between 0 and 20%, depending on the interest rate and on the time frame to reach full capacity. Acknowledgments This research is carried out under the DESIGNATE project, which receives funding from the BELSPO BRAIN-be 2.0 research programme under contract nr B2/191/P1/DESIGNATE. HITA kindly provided input for the development for this case study. References Compernolle, T., Welkenhuysen, K., Petitclerc, E., Maes, D. & Piessens, K., 2019. The impact of policy measures on geothermal energy investments. Energy Economics, 84, 104524. https://doi.org/10.1016/j.eneco.2019.104524 Welkenhuysen, K., Compernolle, T., Kaufmann, O., Laenen, B., Meyvis, B., Piessens, K., Gousis, S., Dupont, N., Harcouet-Menou, V. & Pogacnik, J., this conference. Decision support under uncertainty for geothermal applications: case selection and concept development.