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The pollution pressures on coastal waters predominantly come from the river freshwater transport and loadings of contaminants into the estuary. This study presents the probabilistic model of the near field solute transport in an estuary based on the spatially integrated concentration statistics. A methodology is presented for quantifying the degree of dilution within the surface layer in terms of expected mass and volume fraction functions as a simple alternative to the point concentration probability density function. The theoretical prediction is experimentally validated using the salinity dilution as an inverse process in the field case of river Žrnovnica near the city of Split. A novel dilution measure is presented as combination of expected mass and volume fraction indicating the area of an estuary where dilution process will attenuate the concentration of a passive contaminant below any selected environmental limits. Introduced dilution measure directly corresponds to different catchment loadings through the river as a hydrological pathway of mass transport and can be used for assessing water quality status for transitional water bodies and to guide future efforts for monitoring potential eutrophication hot-spots in the coastal area. [ABSTRACT FROM AUTHOR]

There are multiple factors affecting the behavior of water properties in an estuary, including the hydraulic properties of rivers and corresponding receiving water bodies, along with the potential solutes brought by rivers. Although there are various numerical models and analytical approaches to solving particular or holistic problems in estuaries, measurements are inevitably required. In this study, we developed an innovative low-cost probe based on the Arduino platform as an alternative to more expensive measuring systems. Our device is designed to measure position, temperature, and electrical conductivity in multiple realizations, and it consists of a floating container equipped with the following components: an Arduino Mega development board, a power management module, an SD card logging module, a Bluetooth module, a temperature measuring module, a global positioning satellite (GPS) position module, and a newly developed module for measuring electrical conductivity (EC). We emphasize that all used tools are open-source and greatly supported by the worldwide community. We tested our probe during a field campaign conducted at the estuary of River Jadro near Split (Croatia). Nine probes were released at the river mouth and their position, temperature, and EC were monitored and recorded during the experiment, which ended when the probes stopped, due to the river plume attenuation. The same experiment was repeated three times. All of the probes recorded consistent temperature data, while the EC data show more variable behavior, due to the higher sensitivity of the corresponding sensor. This was expected as a part of the natural process in the estuary. The measured data were additionally used to parameterize an analytical model for mean flow velocity and salinity as a proxy concentration. This showed a good match between the experimental results and the theoretical framework. This work, although focused on water surface applications in the near field zone of an estuary, should be considered as a promising step toward the development of innovative and affordable measurement devices. [ABSTRACT FROM AUTHOR]

A correction to the article "New Screening Tool for Obtaining Concentration Statistics of Pollution Generated by Rivers in Estuaries" that was published in a previous issue is presented.

Rivers represent an essential pathway for waterborne transport, and therefore estuaries are critical coastal areas for a pollution hazard that might lead to eutrophication and general water quality deterioration. When addressing these problems, the decision makers and coastal managers often need additional skills and specialists, so they engage consultants in developing models and providing potential solutions. Different stakeholders’ interests present a challenge in the implementation process of proposed solutions. Nevertheless, if the relevant institutions were presented with a screening tool, enabling them with a certain level of solution ownership, potentially more involvement would occur. There are numerous intertwined physical processes present in the estuary ecosystem, including river discharge, tidal forces, wind-induced stress and water density variations. This research utilizes an analytical model based on ensemble averaging and near-field approximation of the advective-diffusion equation for the case of continuous, steady, conservative solute transport in a stratified, river-dominated estuary. Such an approach significantly reduces the costs and time needed to obtain enough measured data required for common statistical analysis or the need for a more complex numerical model. The developed methodology is implemented into a simple software named CPoRT (Coastal Pollution Risk Tool) within a recently conducted research project funded by European Social Fund. [ABSTRACT FROM AUTHOR]