Numerical simulations for reactive nitrogen compounds pollution measurements in a stream using Saulyev method

Abstract

Nutrient pollution is one of most harmful environmental problems, and is caused by surplus nitrogen in water.  This nitrogen concentration occurring in water can take several forms, such as organic nitrogen, ammonia, nitrite, nitrate, and dissolved nitrogen gas.  Pollution levels can be measured via data collection; however, this is a rather difficult and complex process, and the results obtained widely deviate in term of measurement.  A mathematical model can be used in complicated water-quality measurement.  The advection-dispersion-reaction model provides a pollutant concentration field.  In this research, there are five numerical models for nitrogen pollutant concentration measurement in a stream proposed: a total nitrogen dispersion model, an organic nitrogen dispersion model, an ammonia dispersion model, a nitrite dispersion model, and a nitrate dispersion model.  The traditional Forward Time Central Space finite difference technique and the unconditionally explicit Saulyev technique are employed to obtain five approximated types of organic and inorganic nitrogen pollutant concentrations in each time and place.  This paper proposes five forms of nitrogen pollutant measurement model for the unconditionally stable Saulyev method, so as to make it more accurate without incurring any significant loss of computational efficiency.  The five approximated forms of pollutant concentrations obtained indicate that all models improve the nutrient pollution measurement process.