Water pollution is the most important reason to monitor and assess water quality. The chemical, physical, and biological quality of natural waters may be affected by anthropogenic activities such as industrial, urban, and agricultural activities. In the present study, the water quality of the Zarrineh River, one of the main rivers supplying water in the northwest of Iran, was investigated. A total of 21 sites were selected for surface water sampling during spring and winter (dry and wet) seasons. The concentrations of the metals aluminum, iron, barium, chromium, arsenic, copper, manganese, nickel, selenium, lead, and zinc were determined for source partition and heavy metal pollution index (HMPI) assessment during both the spring and winter seasons. Four important dominant factors in the principal component analysis depicted, in toto, 76.22 percent of the variance, with an initial eigenvalue greater than 1. The calculated HMPI for all the seasons and sampling stations was 66, fluctuating between 30 and 170 in single water sampling sites. The results showed that almost all locations fall into the high classes of the HMPI, but below the critical pollution index limit of 100. Apart from the gold mining establishments and industrial factories, the reasons for the increased concentrations of metals in the Zarrineh River may be attributed in particular to anthropogenic and mining activities.
A one-dimensional qualitative model was created for this study’s modelling and phase transfer of the heavy metal dissolved in the river. The advection–diffusion equation considers the environmental variables temperature, dissolved oxygen, pH, and electrical conductivity as influencing parameters on the change in the concentration of the dissolved phase of heavy metals lead, cadmium, and zinc in springtime and winter. Hec-Ras hydrodynamic model and Qual2kw qualitative model have been used to determine the hydrodynamic and environmental parameters in the created model. The approach of minimizing simulation errors and Vba coding was employed to identify the constant coefficients for these relations, and the linear relation incorporating all of the parameters is thought to be the final connection. In order to simulate and calculate the concentration of the heavy metals in the dissolved phase at each site, the kinetic coefficient of the reaction corresponding to that point should be employed because the kinetic coefficient of the reaction varies in different portions of the river. Additionally, if the above mentioned environmental parameters are used in the spring and winter term of advection–diffusion equations, the accuracy of the developed model significantly improves, and the effect of other qualitative parameters is negligible, indicating that the model is effective at simulating the dissolved phase of heavy metals in the river.
<p><strong>Abstract: </strong>Based on the deep studies of existing mathematical models, a mathematical model that expresses the dynamic of transport and transformation of heavy metals in the rivers has been presented. In this model, the basic principles of chemistry in the environment, hydraulic and fluid transfer dynamics have been used as well as recent studies of researchers. The effects of sediment on the transfer and evolution of heavy metals pollution can be investigated by the proposed models. For example, the evolution and transport of heavy metal pollutants in a steady state flow containing sediment are studied using the present model. The results of theoretical analysis and calculations show that transport and transformation of heavy metal pollution in sediment laden flows, not only have common characteristics of general pollutant but also have features of transport and transformation induced by the movement of sediments.</p><p><strong>Keywords:</strong> Numerical Simulation; Heavy Metal; Pollution; Sediment; Finite Difference Method.</p>
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