Dissolved organic carbon changes

Research into the aquatic chemistry of plutonium has produced information showing how this radioelement is mobilized and transported in the environment. Field studies revealed that the sorption of plutonium onto sediments is an equilibrium process which influences the concentration in natural waters. This equilibrium process is modified by the oxidation state of the soluble plutonium and by the presence of dissolved organic carbon (DOC). Higher concentrations of fallout plutonium in natural waters are associated with higher DOC. Laboratory experiments confirm the correlation. In waters low in DOC oxidized plutonium, Pu(V), is the dominant oxidation state while reduced plutonium, Pu(III+IV), is more prevalent where high concentrations of DOC exist. Laboratory and field experiments have provided some information on the possible chemical processes which lead to changes in the oxidation state of plutonium and to its complexation by natural ligands. 

Fig. 2 Longitudinal changes in nutrient concentrations below the effluent input of a WWTP without tertiary treatment in La Tordera Stream. Values are the average ( SEM) of monthly measurements done over a year (see more details in [47]). In the left panel, note the net decline of ammonium concentration with concomitant net increases in nitrate concentration, suggesting a potential hot spot for nitriflcation. However, in the latest meters downstream, dissolved inorganic nitrogen (DIN) tends to decrease, which indicates net lost of DIN possibly due to denitrification. The right panel shows net changes in phosphate and dissolved organic carbon (DOC) concentrations. While phosphate does not exhibit any clear trend on an annual basis, DOC seems to decline similarly to DIN, which supports the relative dominance of denitrification...

Volk et al. (1997) assessed the effects of ozone, ozone/hydrogen peroxide, and catalytic ozone by changes in the organic constituents of a synthetic solution of fulvic acids. Initial dissolved organic carbon (DOC) and... 

Chittleborough, D. J. K., R. J. Smettem, E. Cotaris, and F. W. Leaney. 1992. Seasonal changes in pathways of dissolved organic carbon through a hillslope soil (Xeralf) with contrasting texture. Australian Journal of Soil Research 30 465-476. 

Grieve, I. C. 1991b. Dissolved organic carbon trends in small streams, land use effects and models of temporal variation. In Sediment and Stream Water Quality in a Changing Environment Trends and Explanation. Proceedings of the Vienna Symposium, August, 1991. IAHS Publication, No. 203, pp. 201-208. 

Schindler, D. W., P. J. Curtis, S. E. Bayley, B. R. Parker, K. G. Beaty, and M. P. Stainton. 1997. Climate induced changes in the dissolved organic carbon budgets of boreal lakes. Biogeochemistry 36 9-28. 

Schiff, S., R. Aravena, E. Mewhinney, R. Elgood, B. Warner, P. Dillon, and S. Trumbore. 1998. Precambrian Shield wetlands Hydrologic control of the sources and export of dissolved organic carbon. Climatic Change 40 167—188. 

Prahl, F.G., and Coble, P.G (1994) Input and behavior of dissolved organic carbon in the Columbia River estuary. In Changes in Fluxes in Estuaries Implications from Science and Management (ECSA22/ERF Symp., Plymouth, England) (Dyer, K.R., and Orth, R.J., eds.), pp. 451 157, Olsen and Olsen, Copenhagen. 

Figure 4 Correlations of with (a) surfactant concentration, (b) in situ chlorophyll fluorescence, (c) dissolved organic carbon (DOC), and (d) colored dissolved organic matter (CDOM) for seawater samples collected from Monterey Bay, USA ( ) and on a transect from Narragansett USA to Bermuda ( ) (Frew, 1997) (reproduced by permission of Cambridge University Press from The Sea Surface and Global Change, 1997, pp. 121-172).

Clair T. A. and Ehrman J. M. (1996) Variations in discharge and dissolved organic carbon and nitrogen export from terrestrial basins with changes in climate a neural network approach. Limnol. Oceanogr. 41, 921-927. 

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