A new mercury (Hg) evasion model for the Adriatic Sea was developed accounting for the ocean mixed layer depth in order to decrease Hg depletion at the surface. Previously modelled airborne Hg species and measured Hg in the ocean were used. Simulations were run using one- and two-way coupled atmosphere-ocean models. Discrepancies in evasion between the applied coupling schemes were shown to be insignificant. The model was evaluated by applying various wind parameterisations and diffusive coefficient formulae. Relatively high discrepancies among the applied methods were observed. The results of a shorter simulation were extrapolated over a one-year period by applying a measurement-based adaptation. We obtained good agreement with previously published data on Hg evasion in the entire Mediterranean area, thus confirming the suitability of the new model for Hg evasion simulations. Model computations performed for the Adriatic Sea resulted in levels of evasion approximately two times lower than previously estimated.

This paper presents a new semi-empirical model for oil droplet size distributions generated by single breaking wave events. Empirical data was obtained from laboratory experiments with different crude oils at different stages of weathering. The paper starts with a review of the most commonly used model for natural dispersion, which is followed by a presentation of the laboratory study on oil droplet size distributions formed by breaking waves conducted by SINTEF on behalf of the NOAA/UNH Coastal Response Research Center. The next section presents the theoretical and empirical foundation for the new model. The model is based on dimensional analysis and contains two non-dimensional groups; the Weber and Reynolds number. The model was validated with data from a full scale experimental oil spill conducted in the Haltenbanken area offshore Norway in July 1982, as described in the last section of the paper.

A two-fluid, small scale numerical ocean model was developed to simulate plume dynamics and increases in water acidity due to leakages of CO2 from potential sub-seabed reservoirs erupting, or pipeline breaching into the North Sea. The location of a leak of such magnitude is unpredictable; therefore, multiple scenarios are modelled with the physiochemical impact measured in terms of the movement and dissolution of the leaked CO2. A correlation for the drag coefficient of bubbles/droplets free rising in seawater is presented and a sub-model to predict the initial bubble/droplet size forming on the seafloor is proposed. With the case studies investigated, the leaked bubbles/droplets fully dissolve before reaching the water surface, where the solution will be dispersed into the larger scale ocean waters. The tools developed can be extended to various locations to model the sudden eruption, which is vital in determining the fate of the CO2 within the local waters.

A coupled 3D hydrodynamic-ecological model was applied to the Santa Marta Coastal Area (SMCA, Colombian Caribbean) to provide insights into the role of external stressors (e.g. wastewater outfall and upwelling) on the water quality and benthic – pelagic coupling. The model was calibrated and validated based on benthic metabolic measurements, satellite–derived chlorophyll-a (Chl-a) and sea surface temperature (SST) maps, field and literature water quality data. The model was able to reproduce the complex dynamics and fast transitions of temperature, nutrients, and phytoplankton, including the stratification and mixing periods during the non-upwelling (NUPW) and upwelling (UPW) seasons. Wide and fast changes in the temperatures and the highly flushed environment prevented excess phytoplankton growth and nutrient accumulation in the benthic and pelagic compartments. The model proved to be a reliable research tool to analyze the interactive effects of upwelling and untreated wastewater on the functioning of a tropical bay.

Air pollution is a major global concern in urban areas and it is considered the greatest environmental risk to health. Nature-based solutions (NBS) can help improve air quality and reduce the urban heat island effect. The impacts of urban vegetation on air quality and ambient temperature depend on many factors, such as vegetation type, location, pollutants, climate conditions and topography. Therefore, the implementation of NBS needs to be tailored for each city. Within the context of the H2020 UNaLab project, the main objective of this work is to assess the potential of NBS to improve air quality across three European cities with different climates: (i) Eindhoven, The Netherlands; (ii) Tampere, Finland; and (iii) Genova, Italy. The WRF-CHEM model was applied for the hottest week in a present climate reference year. The baseline case (without NBS) and two NBS scenarios were simulated for each city. These scenarios (green roofs and green parks) were implemented in the model by modifying the land-use type and the emissions of the model grid cells. According to the model results, the city that least benefited from NBS was Tampere with an average reduction of 5% in surface temperature, and 1% in nitrogen dioxide (NO2) and ozone (O3) concentrations. Temperature-wise Genova and Eindhoven had similar results, approximately 6% reduction, while Genova showed the largest improvement in NO2 (12%). These results indicate that NBS are more effective in high temperature and high air pollution cities, such as Genova. Moreover, this study reinforces the importance of studying case-specific solutions, considering environmental characteristics and challenges.

A simplified particle-tracking model with an idealised coastline was used to investigate how the interaction between variable winds and water level (VaWWL) operates spatially along a coast. The model included a constant along-coast current, horizontal diffusion, onshore/offshore wind drift, beach/cliff combinations and point/distributed litter sources. The default model reproduced basic properties of observed beach litter loadings (zero net accumulation, negatively skewed loading distributions) and the observed spatial pattern along the Scottish east coast, with average loadings increasing in the coastal current direction. The VaWWL effect moved the along-coast flux of floating litter offshore as debeaching events occur during offshore winds. Varying diffusion, coastal current speed, windage, beach/cliff combinations and different foreshore boundary conditions were investigated. Reconciling model predictions with previous estimates of plastic inflow suggested sinking rates of up to 90% soon after first entry into the sea. The VaWWL effect offers a realistic boundary condition for particle-tracking models.

Great Barrier Reef (GBR) catchment management has been constrained by knowledge gaps regarding streambank erosion processes in grazing lands. To help reduce these uncertainties a remote sensing study using high-resolution imagery estimated sediment contributions from cattle traffic on streambanks of a GBR river basin. Results suggest cattle ramps and ramp trails may contribute up to 50% of the modelled streambank sediment supply. Once a suitable delivery ratio is applied, this estimated supply may contribute up to 30% of the modelled fine sediment exported from the Fitzroy River Basin. These findings may also offer a plausible explanation for the first-flush of high sediment concentration observed early in flood hydrographs. Overall, the results could help identify what proportion of currently modelled subsoil erosion is generated by riparian cattle traffic. Future studies applying similar methods could provide useful initial estimates of streambank ramp erosion from grazing land use in other GBR river basins.

Marine debris' transboundary nature and new strategies to identify sources and sinks in coastal areas were investigated along the Paranaguá estuarine gradient (southern Brazil), through integration of hydrodynamic modelling, ground truthing estimates and regressive vector analysis. The simulated release of virtual particles in different parts of the inner estuary suggests a residence time shorter than 5days before being exported through the estuary mouth (intermediate compartment) to the open ocean. Stranded litter supported this pathway, with beaches in the internal compartment presenting proportionally more items from domestic sources, while fragmented items with unknown sources were proportionally more abundant in the oceanic beaches. Regressive vector analysis reinforced the inner estuarine origin of the stranded litter in both estuarine and oceanic beaches. These results support the applicability of simple hydrodynamic models to address marine debris' transboundary issues in the land-sea transition zone, thus supporting an ecosystem transboundary (and not territorial) management approach.

Seagrasses are among the planet’s most effective natural ecosystems for sequestering (capturing and storing) carbon (C); but if degraded, they could leak stored C into the atmosphere and accelerate global warming. Quantifying and modelling the C sequestration capacity is therefore critical for successfully managing seagrass ecosystems to maintain their substantial abatement potential. At present, there is no mechanism to support carbon financing linked to seagrass. For seagrasses to be recognised by the IPCC and the voluntary C market, standard stock assessment methodologies and inventories of seagrass C stocks are required. Developing accurate C budgets for seagrass meadows is indeed complex; we discuss these complexities, and, in addition, we review techniques and methodologies that will aid development of C budgets. We also consider a simple process-based data assimilation model for predicting how seagrasses will respond to future change, accompanied by a practical list of research priorities.