Abstract: Solute transport in subsurface systems often causes unexpected groundwater contamination and has received much attention from environmental researchers. There is, thus, interest in observing the pathways that speed up solute transport to subsurface water. In our study, preferential solute transport with the effects of different transport ions, three solute application methods (small pulse; large pulse; duration pulse), and two pore water velocities (slow 1.47 cm/h, fast 3.34 cm/h) were studied in undisturbed, saturated, silt loam soil columns, using miscible experiments. The solute transport process is simulated by the two-flow region model. Results indicated that (i) the breakthrough curves (BTCs) for different input methods varied greatly, but bimodal peaks were present for both small and large pulse inputs; (ii) the peak appeared significantly later for larger pulse input; (iii) when the pore water velocity was higher, asymmetry and tailing of BTCs were significant for the same input method and breakthrough time advanced and was not dependent on the input method; and (iv) shapes of the BTCs for Cl − and NO3 − were similar, showing both asymmetry and bimodal peaks, except for the peak values. With regard to the adsorbed ions, Cu2 + behaved differently from the anions under the same input method conditions, and its relative concentrations were much lower. The two-flow region model is more significant for characterizing solute transport.
1Institute of Water Resources and Hydro-electric Engineering, Xi’an University of Technology, Xi’an, China.
2State Key Laboratory of Soil Erosion and Dry-land Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, China.
Address for correspondence: Dr. Beibei Zhou, PhD, or Dr. Quanjiu Wang, PhD, Institute of Water Resources and Hydro-electric Engineering, Xi’an University of Technology, Xi’an 710048, China. E-mail: email@example.com; firstname.lastname@example.org
Financial Disclosures/Conflicts of Interest: This research was supported by the National Natural Science Foundation of China (51239009), the 973 Program (2011CB411903), and the projects of the Natural Science Fund (41001132).
Received October 10, 2012.
Accepted for publication April 29, 2013.