Inputs estuary

Table 2. Known inputs and outputs of U to the oceans. Units are 10 g yr or thousand tons per year. References are the most recent primary studies of that flux. Some other fluxes (e.g., groundwater input and input or removal at estuaries) are so poorly known that they cannot be realistically included. Significant uncertainty remains in most of the fluxes listed above so that, within these uncertainties, the U budget can be considered to be in balance.

River inputs. The riverine endmember is most often highly variable. Fluctuations of the chemical signature of river water discharging into an estuary are clearly critical to determine the effects of estuarine mixing. The characteristics of U- and Th-series nuclides in rivers are reviewed most recently by Chabaux et al. (2003). Important factors include the major element composition, the characteristics and concentrations of particular constituents that can complex or adsorb U- and Th-series nuclides, such as organic ligands, particles or colloids. River flow rates clearly will also have an effect on the rates and patterns of mixing in the estuary (Ponter et al. 1990 Shiller and Boyle 1991). 

Several studies have examined the partitioning of U on particles and colloids. Results from detailed sampling and particle separation in the Amazon estuary shows that most of the uranium at the Amazon River mouth is associated with particles (>0.4 im) and that >90% of the uranium in filtered water (<0.4 im) is transported in a colloidal phases (from a nominal molecular weight of 10 000 MW up to 0.4 im) (Swarzenski et al. 1995 Moore et al. 1996). Mixing diagrams for uranium in different size fractions in the Amazon estuary reveal that uranium in all size fractions clearly display both removal and substantial input during mixing. 

Harder, H.W., E.C. Christensen, J.R. Matthews, and T.F. Bidleman. 1980. Rainfall input of toxaphene to a South Carolina estuary. Estuaries 3 142-147. 

Alkylphenol derivatives in the North Sea and UK coastal waters Blackburn and Waldock [11] undertook a survey of water concentrations of alkylphenols (APs) in rivers and estuaries in England and Wales. Locations were selected to represent a wide range of possible AP inputs, from both agricultural and industrial sources. For all samples, both filtered and unfiltered water were treated, to determine both the dissolved and the total extractable APs by GC-MS. 

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]. 

Charette, M.A., K.O. Buesseler, and J.E. Andrews. 2001. Utility of radium isotopes for evaluating the input and transport of groundwater-derived nitrogen to a Cape Cod estuary. Limnology and Oceanography 46 465-470. 

Colloids are present in natural waters (i.e., surface and groundwaters). Surface systems receive terrestrial input as runoff, which carries solid-derived materials into streams, rivers, lakes, or estuaries. Groundwater receives leachates from land fills and percolation water and is frequently well connected with surface water bodies. Colloids may also be formed in situ by native processes of precipitation and dissolution, suspension, or biological activity [103,104]. 

The ion proportions in most river water is significantly different from that in seawater. As a result, river runoff can have a local impact on the ion ratios of coastal waters. This effect is most pronounced in marginal seas and estuaries where mixing with the open ocean is restricted and river input is relatively large. The variable composition of river water and its impact on the chemical composition of seawater are discussed further in Chapter 21. 

The input of terrestrial DOM via rivers and aeolian transport was discussed in Chapter 23.3. Riverine concentrations of DOC range from 2 to 20mgC/L. In contrast, little or no terrestrial DOM is detectable in seawater, leading to the cmrent consensus that most is removed close to its point of input. In some estuaries, removal is associated with flocculation reactions promoted by the large increase in ionic strength that occms when river water mixes with seawater. In other estuaries, DOC exhibits conservative behavior, leaving marine chemists with a mystery as to how and where DOC is removed. 

In Figure 1, a map is presented of the estuary of the river Rhine near (west of) Rotterdam. The industrialized region is situated around the harbors located south of the river near Hoogvliet. Refineries and fertilizer plants are found there. In Table 1, various stages in pattern recognition are listed. The subroutine CHANGE, in combination with the INPUT-format is used in stages one and two. 

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