Estuaries, models

The compound formaldehyde is biodegrading in several systems simultaneously (1) a lake, modeled as a complete mix reactor (2) an estuary, modeled as three complete mixed reactors in series (3) a large river, modeled as 10 complete mixed reactors in series, and a small stream, modeled as a plug flow reactor. What is the nondimensional reaction/residence time, k p, that is required for each of these systems to reach a degradation of 50%, 90%, 99%, and 99.9% ... 

Reckhow, K.H., and Gray, J. (2000) Neuse River Estuary modeling and monitoring project stage 1 stage 1 executive summary and long-term modeling recommendations. Report no. 325-A of the Water Resources Research Institute, University of North Carolina, Chapel Hill, N.C. 

Gunnerson, C.G. 1966. Optimizing the sampling interval in tidal estuaries. J. Sanit. Eng. 92 103-125. Harleman, D.R.F., E.R. Holley, and W,C. Huber. 1966. Interpretation of water pollution data from tidal estuary models, p. 1-11. In Paper no. 3, Sect. III. Proc. 3rd Int. Conf. Water Pollut. Res., Munich. September. Pergamon Press. 

Dynamic estuary model (DEM) Tidal temperature model (TTM) RECEIV SRMSCI... 

Figure 10.11. Regression coefficients for PLS prediction of DOC from fluorescence in the Horsens catchment. (A) River and WTP model with two latent variables. (B) Estuary model with three latent variables.

For the river and WTP sites, a five-component model has the lowest RMSECV however, the two-component model appears to be a better choice, given that relatively small gains in RMSECV (and the correlation coefficient, are obtained by including the last three latent variables. For the estuary sites, a three- component model appears to be sufficient. Again, a seven-component model has lower RMSECV, yet only very small improvements in RMSECV are attained with the addition of many latent variables. A conservative approach is thus to select two latent variables for the river and WTP model, and three for the estuary model. 

Similarly, contaminant concentrations in rivers or streams can be roughly assessed based on rate of contaminant introduction and dilution volumes. Estuary or impoundment concentration regimes are highly dependent on the transport mechanisms enumerated. Contaminants may be localized and remain concentrated or may disperse rapidly and become diluted to insignificant levels. The conservative approach is to conduct a more in-depth assessment and use model results or survey data as a basis for determining contaminant concentration levels. 

MODELED PROCESS Air Runoff Streams Lakes Estuaries Unsat. Zone Sat. Zone... 

Future needs in support of model validation and performance testing must continue to be in the area of coordinated, well-designed field data collection programs supplemented with directed research on specific topics. The FAT workshop produced a listing of the field data collection and research needs for the air, streams/lakes/estuaries, and runoff/unsaturated/saturated soil media categories, as follows ... 

The reaction manifold describing the automated determination of ammonia is shown in Fig. 6.1. Two alternative modes of sampling are shown discrete and continuous. Discrete 5 ml samples contained in ashed (450 °C) glass vials are sampled from an autosampler (Hook and Tucker model A40-11 1.5 min sam-ple/wash). For high-resolution work in the estuary, the continuous sampling mode is preferred. The indophenol blue complex was measured at 630 nm with a colorimeter and the absorbance recorded on a chart recorder. 

Ibanez C, Saldana J, Prat N (1999) A model to determine the advective circulation in a three layer, salt wedge estuary Application to the Ebre River estuary. Estuar Coast Shelf Sci 48 271-279... 

Thomann, R.V., J.A. Mueller, R.P. Winfield, and C.-R. Huang. 1991. Model of fate and accumulation of PCB homologues in Hudson estuary. Jour. Environ. Engin. 117 161-178. 

Katsev, S., etal. 2007. Effect of progressive oxygen depletion on sediment diagenesis and fluxes A model for the Lower St. Lawrence Estuary. Limnology and Oceanography, 52, 2555-2568. 

To assess the relative importance of the volatilisation removal process of APs from estuarine water, Van Ry et al. constructed a box model to estimate the input and removal fluxes for the Hudson estuary. Inputs of NPs to the bay are advection by the Hudson river and air-water exchange (atmospheric deposition, absorption). Removal processes are advection out, volatilisation, sedimentation and biodegradation. Most of these processes could be estimated only the biodegradation rate was obtained indirectly by closing the mass balance. The calculations reveal that volatilisation is the most important removal process from the estuary, accounting for 37% of the removal. Degradation and advection out of the estuary account for 24 and 29% of the total removal. However, the actual importance of degradation is quite uncertain, as no real environmental data were used to quantify this process. The residence time of NP in the Hudson estuary, as calculated from the box model, is 9 days, while the residence time of the water in the estuary is 35 days [16]. 

In particular, for the relatively volatile APs, volatilisation can be a significant process of removal from the water column [16,32]. A model study showed that volatilisation of NP was in fact a more important removal process than degradation and advection out of the estuary [16]. The estuarine fate of short-chain APEO metabolites in estuaries is determined mainly by sorption processes, degradation in the water, and advective transport out of the estuary [15]. 

Influence of other ions. Two examples are considered to illustrate the importance of other ions in natural waters on Mn(II) oxidation kinetics. In the first example the ionic composition of the solution is typical of that found in freshwaters and in the second example the composition of the solution is typical of that found in the low salinity region of an estuary (I -0.1M). The composition of these solutions is given in Davies (26). The calculated oxidation half-lives based on the model given above for these systems are shown in Table VI. 

Turner A (2003) Salting out of chemicals in estuaries Imphcation for contaminant partitioning and modeling. Sci Total Environ 315 599-612... 

Rivers are close to the perfect environmental flow for describing the flow as plug flow with dispersion. The flow is confined in the transverse and vertical directions, such that a cross-sectional mean velocity and concentration can be easily defined. In addition, there is less variation in rivers than there is, for example, in estuaries or reactors - both of which are also described by the plug flow with dispersion model. For that reason, the numerous tracer tests that have been made in rivers are useful to characterize longitudinal dispersion coefficient for use in untested river reaches. A sampling of the dispersion coefficients at various river reaches that were... 

Thorrold et al. [81] used EDA and ANN models to classify fish as a function of their natal estuary. They investigated the ability of trace element and isotopic signatures measured in otoliths to record the nursery areas of juvenile (young-of-the-year) weakfish Cynoscion regalis from the east coast of the USA. 

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