For many years, first as a students and later as a teachers, we have observed graduate students in ecology and other environmental sciences who had been required as undergraduates to take calculus courses. Those courses have often emphasized how to prove theorems about the beautiful, logical structure of calculus, but have neglected applications. Most of the time, the students have come out of such courses with little or no appreciation of how to apply calculus in their own work. Based on these observations, a new approach to numerical method based on "interpolation theory for functions of two variables is proposed. We develop a multivariate divided difference method. In addition, the explicit formulae that connect the classical finite difference interpolation coefficients for one variable curve with multivariate interpolation coefficients are established"[34] To illustrate the accuracy and efficiency of suggested method we used it to estimate the rate of contaminated soils by heavy metals that is evaluate the concentration of heavy metals in soil of some city.