2004 Fiscal Year Final Research Report Summary
Nitrate Infiltration Processes in Non-homogeneous Porous Media
| Project/Area Number |
13680610
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Environmental dynamic analysis
|
|---|
| Research Institution | Chiba University of Commerce |
|---|
Principal Investigator |
SUGITA Fumi Chiba University of Commerce, Faculty of Commerce and Economics, Associate Professor, 商経学部, 助教授 (40275962)
|
|---|
| Project Period (FY) |
2001 – 2004
|
| Keywords | nonhomogeneous porous medium / laboratory infiltration experiment / nitrate / macropores / evaporation from heterogeneous surfaces / vadoze zone |
|---|
| Research Abstract |
Groundwater contamination by nitrate in agricultural area is a serious problem in many countries including Japan. Nitrogen enters underground system from the ground surface and infiltrates through vadoze zone to groundwater table. The infiltration processes are complicated due to heterogeneity of the porous medium as well as that of rainfall distribution with respect to time and space. The effects of macropore and rainfall pattern were investigated by means of field observations, laboratory experiments and numerical simulation.
The maximum concentration is always found near the ground surface and the concentration decreases with depth in the field covered with various crops. These results coincide with profiles obtained in macroporous media with repeating rainfalls less than 13mm/event in the laboratory. The macropores serve as the fast conduits for water and solute under relatively large rainfalls whereas they cause large solute dispersion under all rainfalls. The rainfall intensity controls onset of the macropore flow. The effects of macropores are most apparent in intermediate strength rainfalls in which piston flow did not occur. The numerical model that accounts for macropore flow was able to reproduce the profiles observed in the laboratory.
|
