#
New Screening tool for Obtaining Concentration Statistics of Pollution Generated by Rivers in Estuaries^{ †}

^{1}

^{2}

^{*}

^{†}

## Abstract

**:**

## 1. Introduction and Problem Formulation

## 2. Three-Step Strategy

#### 2.1. Theoretical Background

^{−1}is an attenuation coefficient representing all existing mechanisms that, when combined, concur to progressively reduce U in the x direction, including bathymetry, tides, wind, sea currents, and salinity stratification. The proposed exponential form of mean velocity attenuation as a function of the x resulted from measured velocities, and it was also tested and compared to the hydrodynamic model MOHID [23], as well as to the existing theoretical model for jet flow [24] in [13]. It was shown to be a suitable assumption since it delivered a solution similar to MOHID results and measurements while obtaining a simple expression to be easily used within the recursive equation for standard concentration moments. When such a non-uniform mean velocity field is introduced in Equation (3), the general recursive solution of concentration moments is obtained:

#### 2.2. The Model—CPoRT

^{3}, and the source width (m). The source concentration may be calculated in an additional dialog box if the contaminant mass flux is known ($\dot{m}$ kg/day).

^{−9}m${}^{2}$/s by default, which is a regular value for surface waters [30], but it is user-editable. As previously discussed, molecular diffusion does not have a significant impact in the near field zone, and therefore it may be conservatively kept at a default value unless the user has performed some additional measurements to change it accordingly. The turbulent diffusion coefficient ${e}_{t}$ (m${}^{2}$/s) should be measured and assessed for the estuarine system in question. However, if no data is available, different values can be tested to assess its potential effect on the pollution plume spreading, especially for the worst-case scenario. Depending on the case scenario, lower values of ${e}_{t}$ (e.g., less than 10

^{−4}m${}^{2}$/s) may indicate the longer distance from the river mouth where an acceptable level of concentration may be expected since the plume is narrower as opposed to higher values (e.g., more than 10

^{−2}m${}^{2}$/s). A higher turbulent diffusion coefficient implies greater lateral spreading of the plume which may indicate unwanted concentration at bay sides, but shorter downstream impact. Velocity attenuation may be set to a measured value or calculated within a dialog box if downstream centerline velocity data is known.

#### 2.3. Stakeholders’ Involvement

## 3. Results

#### 3.1. Illustrative Example

#### 3.2. User’s Feedback

## 4. Conclusions and Future Work

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

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**Figure 1.**Problem description within a broader framework (adapted from Galešić et al. [13]).

**Figure 2.**Coastal Pollution Risk Tool (CPoRT) application graphical interface in general (

**a**) and an example of the mean surface plot in the CPoRT (

**b**).

**Figure 3.**Illustrative results: the Žrnovnica estuary map with surface plot of mean concentration and the probability of exceeding the limit concentration (${c}^{*}=1$ mg/L) in chosen points.

**Figure 4.**The cross-sectional results for total nitrogen from the CPoRT: (

**a**) mean concentration; (

**b**) concentration variance.

**Figure 5.**Probability of exceeding the limit concentration of 1 mg/L along the centerline of the plume.

**Figure 6.**The participants’ statements regarding the applicability of the CPoRT in the decision-making process for coastal water management from students (

**a**) and local stakeholders (

**b**).

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**MDPI and ACS Style**

Galešić, M.; Andričević, R.; Divić, V.; Šakić Trogrlić, R.
New Screening tool for Obtaining Concentration Statistics of Pollution Generated by Rivers in Estuaries. *Water* **2018**, *10*, 639.
https://doi.org/10.3390/w10050639

**AMA Style**

Galešić M, Andričević R, Divić V, Šakić Trogrlić R.
New Screening tool for Obtaining Concentration Statistics of Pollution Generated by Rivers in Estuaries. *Water*. 2018; 10(5):639.
https://doi.org/10.3390/w10050639

**Chicago/Turabian Style**

Galešić, Morena, Roko Andričević, Vladimir Divić, and Robert Šakić Trogrlić.
2018. "New Screening tool for Obtaining Concentration Statistics of Pollution Generated by Rivers in Estuaries" *Water* 10, no. 5: 639.
https://doi.org/10.3390/w10050639