A comparison of residence time calculations using simple compartment models of the Altamaha River estuary, Georgia

Estuaries ◽  
2002 ◽  
Vol 25 (6) ◽  
pp. 1304-1317 ◽  
Author(s):  
Joan E. Sheldon ◽  
Merryl Alber
Keyword(s):  
Residence Time ◽  
River Estuary ◽  
Compartment Models

scholarly journals Compartment models for estimating attributes of digesta flow in cattle

1988 ◽  
Vol 60 (3) ◽  
pp. 571-595 ◽  
Author(s):  
K. R. Pond ◽  
W. C. Ellis ◽  
J. H. Matis ◽  
H. M. Ferreiro ◽  
J. D. Sutton
Keyword(s):  
Residence Time ◽  
Mean Residence Time ◽  
Residence Times ◽  
Age Dependency ◽  
Faecal Excretion ◽  
Compartment Models ◽  
Equal Rate ◽  
Age Dependent ◽  
The Mean ◽  
Age Independent

1. The basic assumptions involved in one- and two-compartment models with age-independent distributed residence times (exponential, G1) for describing digesta flow are reviewed as the bases for describing families of one- and two-compartment models which assume age-dependent distributions (Gn) of residence times.2. The two-compartment, age-independent model with exponentially distributed residence times (GIGI) yielded estimates of essentially equal rate parameters when fitted to faecal values for all four cows receiving a diet of 500 g coarsely chopped, sodium hydroxide-treated straw /kg and one of four cows receiving the same diet but with ground and pelleted straw. The incorporation of progressively higher orders of age dependency (G2-G6, Gn) into the faster turnover compartment of two-compartment models (GnG1) resulted in a resolution of equal rate parameters estimated by the G1G1 model and a reduction in standard errors for the rate and the initial concentration parameters.3. The occurrence of equal rate parameters in two-compartment models indicated an age-dependent process; a process which could equally well be described by a one-compartment, age-dependent compartment having an order of age dependency equal to the sum of these orders in the two-compartment model with equal rate parameters.4. The age-independent models overestimated time of first appearance in the faeces of a meal's particles. The association of age dependency with the faster turnover compartment resulted in earlier estimates for first appearance of the marked particles; estimates which were more consistent with observed first appearance.5. The faecal excretion pattern from cows fed on the ground and pelleted straw diet exhibited an age-independent distribution of longer residence times which dominated approximately 80% of the later residence times. Age-dependent, one-compartment models gave a poor fit to such data from these cows fed on ground and pelleted straw. In contrast, age-dependent, one-compartment models provided an excellent fit to data from cows fed on chopped straw; data which indicated that age-independent distributions of residence times were much delayed in appearing or were totally absent.6. The mean residence time for the slower turnover, age-independent compartment estimated from faecal excretional of stained particles from either diet was similar to that estimated from duodenal concentrations of the stained particles. This suggests that the slower turnover model compartment was confined to preduodenal sites.7. The mean residence time for the faster turnover, age-dependent compartment estimated from duodenal data was 58–62 % that estimated from faecal data and suggests that the site of this model compartment was both pre- and post-duodenal.8. It is emphasized that the slow and imperfect mixing of particulate matter that occurs in reticulo-rumen digesta is inconsistent with the assumptions of instantaneous and homogeneous mixing made by models having age-independent distributions of residence times. The use of age-dependent distributed residence times can accommodate such imperfect mixing and is consistent with the existence of age-discriminating processes involved in particle flow from the reticulo-rumen. Age dependency also offers improved precision in estimating parameters of digesta flow via processes having inherent uncertainty in their mixing and age-discriminating mechanisms.

scholarly journals Microbial Biogeography along an Estuarine Salinity Gradient: Combined Influences of Bacterial Growth and Residence Time

2004 ◽  
Vol 70 (3) ◽  
pp. 1494-1505 ◽  
Author(s):  
Byron C. Crump ◽  
Charles S. Hopkinson ◽  
Mitchell L. Sogin ◽  
John E. Hobbie
Keyword(s):  
Bacterial Community ◽  
Community Composition ◽  
Residence Time ◽  
Doubling Time ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Salinity Gradient ◽  
Bacterial Community Composition ◽  
River Estuary ◽  
Leucine Incorporation ◽  
Bacterioplankton Community

ABSTRACT Shifts in bacterioplankton community composition along the salinity gradient of the Parker River estuary and Plum Island Sound, in northeastern Massachusetts, were related to residence time and bacterial community doubling time in spring, summer, and fall seasons. Bacterial community composition was characterized with denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA. Average community doubling time was calculated from bacterial production ([14C]leucine incorporation) and bacterial abundance (direct counts). Freshwater and marine populations advected into the estuary represented a large fraction of the bacterioplankton community in all seasons. However, a unique estuarine community formed at intermediate salinities in summer and fall, when average doubling time was much shorter than water residence time, but not in spring, when doubling time was similar to residence time. Sequencing of DNA in DGGE bands demonstrated that most bands represented single phylotypes and that matching bands from different samples represented identical phylotypes. Most river and coastal ocean bacterioplankton were members of common freshwater and marine phylogenetic clusters within the phyla Proteobacteria, Bacteroidetes, and Actinobacteria. Estuarine bacterioplankton also belonged to these phyla but were related to clones and isolates from several different environments, including marine water columns, freshwater sediments, and soil.

scholarly journals Calculating Estuarine Exchange Flow Using Isohaline Coordinates*

2011 ◽  
Vol 41 (6) ◽  
pp. 1116-1124 ◽  
Author(s):  
Parker MacCready
Keyword(s):  
Residence Time ◽  
River Estuary ◽  
Columbia River ◽  
Time Dependent ◽  
Salt Flux ◽  
Exchange Flow ◽  
Exact Formulation ◽  
Volume Flux ◽  
Columbia River Estuary ◽  
Estuarine Exchange

Abstract A method for calculating subtidal estuarine exchange flow using an isohaline framework is described, and the results are compared with those of the more commonly used Eulerian method of salt flux decomposition. Concepts are explored using a realistic numerical simulation of the Columbia River estuary. The isohaline method is found to be advantageous because it intrinsically highlights the salinity classes in which subtidal volume flux occurs. The resulting expressions give rise to an exact formulation of the time-dependent Knudsen relation and may be used in calculation of the saltwater residence time. The volume flux of the landward transport, which can be calculated precisely using the isohaline framework, is of particular importance for problems in which the saltwater residence time is critical.

scholarly journals Residence time of the Danshuei River estuary, Taiwan

2004 ◽  
Vol 60 (3) ◽  
pp. 381-393 ◽  
Author(s):  
Chi-Fang Wang ◽  
Ming-Hsi Hsu ◽  
Albert Y. Kuo
Keyword(s):  
Residence Time ◽  
River Estuary
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