ISSN:
1745-6584
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Energy, Environment Protection, Nuclear Power Engineering
,
Geosciences
Notes:
The in situ measurement of water flow and chemical transport through clay pan soils is crucial to understanding potential water contamination from agricultural sources. It is important due to the large areal extent of these soils in agricultural regions of the midwestern United States and because of preferential flow paths caused by desiccation cracks, worms burrowing, and root development. A study plot at the Missouri Management Systems Evaluation Area near Centralia, Missouri, was instrumented to determine the rate of preferential flow of water and transport of NO3−1 fertilizer in the unsaturated zone through a claypan soil using 15N-NO3−1 and Br-1 tracers. The areal distribution of preferential flow paths was between 2 and 20% in the topsoil. Gravity lysimeter flow caused by preferential flow through the claypan was as much as 150 times greater than the estimated average rate of vertical recharge. As much as 2.4% of the volume of the soil below the clay pan may be occupied by preferential flow paths.The 15N-NO3−1 concentrations in ground water indicate that substantial quantities of fertilizer-derived NO3−1 were transported to ground water through the claypan during the first recharge event following fertilizer application even though that event occurred six months after application. Hydraulic conductivity, measured at three scales, ranged from 6.2 × 10−8 to 7.5 × 10−3 cm/s. The observed increase of calculated hydraulic conductivity with each increase in scale was attributed to the inclusion of more and larger preferential flow paths within the volume over which the measurement was made, indicating hydraulic conductivity measured at one scale may not describe flow and transport at another scale.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1745-6584.1998.tb02820.x
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