scholarly journals On the propagation of reaction fronts in a sandy aquifer over 20+ years: lessons from a test site in northwestern Germany

2021 ◽  
Author(s):  
Georg J. Houben ◽  
Vincent E.A. Post ◽  
Jens Gröger‐Trampe ◽  
María H. Pesci ◽  
Jürgen Sültenfuß
Keyword(s):  
Test Site ◽  
Reaction Fronts ◽  
Sandy Aquifer

Field Observations of Tracer Dispersion Under Natural Flow Conditions in an Unconfined Sandy Aquifer

1979 ◽  
Vol 14 (1) ◽  
pp. 1-18 ◽  
Author(s):  
E.A. Sudicky ◽  
J.A. Cherry
Keyword(s):  
Analytical Solution ◽  
Groundwater Flow ◽  
Solute Transport ◽  
Deterministic Model ◽  
Test Site ◽  
Chloride Salt ◽  
Transport Parameters ◽  
Deterministic Models ◽  
Wide Range ◽  
Sandy Aquifer

Abstract ABSTRACT An exceptionally detailed field determination of the solute transport parameters was performed in an unconfined sandy aquifer near an abandoned landfill at the Canadian Forces Base at Borden, Ontario. The test site is located above the contaminant plume originating from the landfill. The aquifer consists of slightly stratified sands with minor laminations. A chloride salt solution was injected into a two m3 volume of aquifer about one meter below the water-table and then migration of the tracer occurred under the natural hydraulic gradient. The migration of the chloride pulse was monitored in detail using a three-dimensional array of bundle-type multilevel samplers. Hydraulic head measurements in the zone of transport were obtained from a network of miniature piezometers. The test results demonstrated the influence of zones of local aquifer heterogeneity on solute migration rates and the ability of a porous medium to disperse solutes in these zones. Different rates of groundwater flow between a fast and slow transport zone caused the pulse to split into two halves. Each half was found to be Gaussian in shape in accord with the classical theory of solute transport. The measured chloride distributions closely fit an analytical solution of the advection-dispersion equation. Dispersivity values for chloride obtained from the analytical solution increased with mean travel distance in the groundwater flow domain, which suggests that calibration of a deterministic model at one spatial scale may lead to erroneous predictions when applied to a different scale. From this it is concluded that, if deterministic models are to yield useful predictions of contaminant migration, it will be necessary to establish scaling functions from studies of the variability of transport parameters in a wide range of hydrogeological settings.

Magnitude Estimation and Cross-Modal Matching of Lingual Vibrotactile and Auditory Sensation

1989 ◽  
Vol 32 (3) ◽  
pp. 698-702 ◽  
Author(s):  
Daniel Harris ◽  
Donald Fucci ◽  
Linda Petrosino
Keyword(s):  
Auditory Stimulus ◽  
Magnitude Estimation ◽  
Sensory Processing ◽  
Test Site ◽  
Systematic Investigation ◽  
Thenar Eminence ◽  
Stimulus Range ◽  
Psychophysical Scaling ◽  
Scaling Methods ◽  
Response Biases

The present experiment was a preliminary attempt to use the psychophysical scaling methods of magnitude estimation and cross-modal matching to investigate suprathreshold judgments of lingual vibrotactile and auditory sensation magnitudes for 20 normal young adult subjects. A 250-Hz lingual vibrotactile stimulus and a 1000-Hz binaural auditory stimulus were employed. To obtain judgments for nonoral vibrotactile sensory magnitudes, the thenar eminence of the hand was also employed as a test site for 5 additional subjects. Eight stimulus intensities were presented during all experimental tasks. The results showed that the slopes of the log-log vibrotactile magnitude estimation functions decreased at higher stimulus intensity levels for both test sites. Auditory magnitude estimation functions were relatively constant throughout the stimulus range. Cross-modal matching functions for the two stimuli generally agreed with functions predicted from the magnitude estimation data, except when subjects adjusted vibration on the tongue to match auditory stimulus intensities. The results suggested that the methods of magnitude estimation and cross-modal matching may be useful for studying sensory processing in the speech production system. However, systematic investigation of response biases associated with vibrotactile-auditory psychophysical scaling tasks appears to be a prerequisite.

Sign in / Sign up

Export Citation Format

Share Document