Effects of Reclaimed Water and C and N on Breakthrough Curves in Sandy Soil and Loam

Abstract

Long-term irrigation with reclaimed water may change soil physical properties and solute transport rate due to C and N in reclaimed water and the particularity of reclaimed water. Ordinary water, reclaimed water and mixed water which added C and N into reclaimed water were used as background water, then potassium bromide was added to background water and mixed them into three kinds of solutions whose bromide concentrations were all 0.5 mol/L, then soil column breakthrough experiments were conducted. The results showed that bacteria quantity increased both in sandy soil and loam after soil column experiments, and bacteria quantity in sandy soil and loam were all in the following descending order: breakthrough solution using mixed water as background water, breakthrough solution using reclaimed water as background water, and breakthrough solution using ordinary water as background water. However, fungi quantity had no significant difference. Cumulative infiltration in sandy soil and loam can be properly described by power function and logarithm function, respectively. The amount of cumulative infiltration in sandy soil and loam in the same infiltration time were all showed a descending order as: breakthrough solution using ordinary water as background water, breakthrough solution using reclaimed water as background water, and breakthrough solution using mixed water as background water. Breakthrough curves can be well described by CXTFIT 2.1 code, it can be seen from the values of V and D that reclaimed water and the addition of C and N made solute transport more difficult in soils and increased diffusion coefficient, and these impacts were greater on loam than sandy soil. Reclaimed water and the added C and N increased soil bacteria, complicated soil pore system, and decreased soil hydraulic conductivity.