A Simplified Model to Estimate the Concentration of Inorganic Ions and Heavy Metals in Rivers

Clemêncio Nhantumbo,Rolf Larsson,Magnus Larson,Kenneth Persson,Dinis Juízo

doi:10.3390/w8100453

Abstract

This paper presents a model that uses only pH, alkalinity, and temperature to estimate the concentrations of major ions in rivers (Na+, K+, Mg2+, Ca2+, HCO3−, SO42−, Cl−, and NO3−) together with the equilibrium concentrations of minor ions and heavy metals (Fe3+, Mn2+, Cd2+, Cu2+, Al3+, Pb2+, and Zn2+). Mining operations have been increasing, which has led to changes in the pollution loads to receiving water systems, meanwhile most developing countries cannot afford water quality monitoring. A possible solution is to implement less resource-demanding monitoring programs, supported by mathematical models that minimize the required sampling and analysis, while still being able to detect water quality changes, thereby allowing implementation of measures to protect the water resources. The present model was developed using existing theories for: (i) carbonate equilibrium; (ii) total alkalinity; (iii) statistics of major ions; (iv) solubility of minerals; and (v) conductivity of salts in water. The model includes two options to estimate the concentrations of major ions: (1) a generalized method, which employs standard values from a world-wide data base; and (2) a customized method, which requires specific baseline data for the river of interest. The model was tested using data from four monitoring stations in Swedish rivers with satisfactory results.

Highlights

Mining is common in many African countries and it brings substantial revenues to the governments
There are a number of existing mathematical models that may be useful in connection with water quality monitoring programs, the most common being the Streeter–Phelps model, the QUAL Model, WASP Models, QUASAR Model, MIKE Models, BASIN Model, EFDC Model, and PHREEQ C [9]
Both model options were used, i.e., the generalized method, which uses the continental averages of relative concentrations, denoted by (G); and the customized method, which uses the river specific relative concentrations, denoted by (C) and (Cav)

Summary

Introduction

Mining is common in many African countries and it brings substantial revenues to the governments. The impacts are imminent, and the water quality monitoring programs in developing countries are not well established to assess the water quality changes [8]. A lack of resources is one of the main constraints in implementing sustainable water quality monitoring programs in developing countries [8]. This makes it important to develop less resource-demanding monitoring programs supported by mathematical models that minimize the required sampling and analysis, while retaining the capability to detect and quantify water quality changes, thereby allowing for the rapid implementation of measures to protect water resources.

Methods

Results

Conclusion