Dissolved reactive

The solid-water interface, mostly established by the particles in natural waters and soils, plays a commanding role in regulating the concentrations of most dissolved reactive trace elements in soil and natural water systems and in the coupling of various hydrogeochemical cycles (Fig. 1.1). Usually the concentrations of most trace elements (M or mol kg-1) are much larger in solid or surface phases than in the water phase. Thus, the capacity of particles to bind trace elements (ion exchange, adsorption) must be considered in addition to the effect of solute complex formers in influencing the speciation of the trace metals. 

Concentrations of dissolved reactive phosphorous (DRP) (Fig. 4) in glacier streams, and the two small streams Calancasca and Versegeres, fell in the range of a few... 

Deposition during the mixed period (up to day 165) was calculated from a mass balance on water-column Si and the Si P ratio in sediment trap material, because sediment traps overestimate the net particle deposition flux in a mixing water column (19). Our calculations assumed that losses of dissolved reactive Si resulting from diatom uptake that are not accounted for by increases in particulate biogenic Si are caused by Si deposition. The estimate of mixed-period P deposition was conservative because we assumed that nondiatom particulate P was removed at a rate similar to diatom P. We also assumed that loss of P in traps resulting from diagenesis-dissolution was negligible. The use of short collection periods (2-3 weeks) and a poison should minimize loss. 

Uptake and Release by Diatoms. Diatoms represent a major sink and transport vector for P in Lake Michigan. The importance of diatom production is shown by the changes in dissolved reactive Si levels that resulted from incorporation into diatoms. During the mixed period (late March to mid-June) dissolved reactive Si decreased by 30.7 g/m2, representing 36% of the spring concentration. An additional 11.4 g/m2 was re-... 

As contaminant transport occurs over times much greater than the times over which groundwater flow fluctuates, steady flow is frequently assumed. For steady groundwater flow in three dimensions, the following vector equation, developed based on mass conservation principles, is typically used to model advective/ dispersive transport of a dissolved reactive contaminant (after [53]) ... 

Location Dissolved total Hg Particulate total Hg Dissolved reactive Hg Dissolved MMHg Particulate MMHg Dissolved DMHg Dissolved Hg° Reference(s)... 

Many important chemical reactions take place in the aqueous component of the atmospheric aerosol or in fog droplets. An example is the solution-phase oxidation of SO2 to SO. Such reactions may drive the dilTusioiial transport of reactants from the gas to the particles followed by absorption and chemical reaction. If the chemical reactions are slow compared with the gas- and aero.sol-phase transport rates, the dissolved reactive species will be nearly in equilibrium between the gas and particles. 

Downes, M.T. and Paerl, H.W. (1978) Separation of two dissolved reactive phosphorus fractions in lake water. Journal of the Fisheries Research Board of Canada 35, 1636-1 539. 

FIGURE 9.8 Schematic showing separation of dissolved reactive phosphorus and particulate phosphorus in water samples. 

FIGURE 17.34 Vertical distribution of dissolved reactive phosphorus in soil pore water and water column at impacted and unimpacted sites in the WCA-2A of the Everglades. (Reddy, K. R., Unpublished Results, University of Florida.)... 

These three phase reactions may be classified into two distinct categories,one in which the solids are sparingly soluble in the medium and the reaction occurs between the dissolved gas and dissolved reactive species obtained from dissolution of solid particles,the other in which the particles are insoluble in medium.In each case, the product of the reaction may be soluble or insoluble in medium.Table 1 and 2 show some typical examples of these two cases. 

Particles smaller than the liquid film thickness.The liquid film thickness in gas-liquid reactors may vary between 5-100 microns. Thus for a gently stirred system,the average diameter of the particles may considerably be less than the thickness of the liquid film( d < 0.1 6) and we can conceivably have the step of dissolution of solid particles in parallel to that of diffusion of dissolved gas from the gas-liquid interface to the bulk liquid-phase.Depending on the relative rates of diffusion and chemical reaction,the entire amount of dissolved gas may react in the film leading to considerable enhancement of gas absorption rate.Further,the concentration of dissolved reactive species in the liquid film may be uniform(in which case the simultaneous dissolution of solid particles in the film will not affect the specific rate of mass transfer),or may be zero at a location close to the gas-liquid interface. 

L.A. Zimmer, G.A. Cutter, High resolution determination of nanomolar concentrations of dissolved reactive phosphate in ocean surface waters using long path liquid waveguide capillary cells (LWCC) and spectro-metric detection, Liiimol. Oceanogr. Methods 10 (2012) 568-580. 

R.L. Benson, Y.B. Truong, I.D. McKelvie, B.T. Hart, G.W. Bryant, W.P. Hilkmann, Monitoring of dissolved reactive phosphorus in wastewaters by flow injection analysis. Part 2. One-line monitoring system. Water Res. 30 (1996) 1965-1971. 

O. Tue-Ngeun, P. Ellis, I.D. McKelvie, P. Worsfold, J. Jakmunee, K. Grudpan, Determination of dissolved reactive phosphorus (DRP) and dissolved organic phosphorus (DOP) in natural waters by the use of rapid sequenced reagent injection flow analysis, Talanta 66 (2005) 453-460. 

S. Auflitsch, D-M.W. Peat, P.J. Worsfold, I.D. McKelvie, Determination of dissolved reactive phosphorus in estuarine waters using a reversed flow injection manifold. Analyst 122 (1997) 1477-1480. 

However, the nature of the filtrate is ultimately dependent on the nature of the membrane used, the conditions under which the filtration is performed, and the nature of the sample itself, and for these reasons, the use of the terms soluble and dissolved reactive phosphorus is misleading. A less ambiguous nomenclature would be the use of the term filterable reactive phosphorus membrane pore size ( xm)), e.g., FRF (0.2) where a 0.2 xm filter was used. 

Stripping or elution methods, also widely used, are based on the saturation of the melt with the gas. The melt is stripped by an inert gas carrier and the evolved gas mixture is measured and analyzed.In this method it is assumed that the inert gas removes completely the dissolved reactive gas by displacing the equilibrium representing the solubility reaction. However, this method, although applicable to nonreactive systems, does not appear to be reliable with reactive systems. 

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