Nitrate concentration profile

Two plots are shown in Figure 1, the upper one indicates the concentration of S(V1) (the S(IV) autoxidation product) growing with the time of reaction performed under quasisteady state conditions and the lower one which gives the rate - scavenger (nitrate) concentration profile. 

Figure 1. Effect of nitrates (low concentration region) on the rate of S(IV) autoxidation accumulation of the reaction product, S(VI), in time (upper plots) rate -scavenger (nitrate) concentration profile.

Fig. 6.17 Typical nitrate concentration profiles of surface sediments from different productivity regions in the South Atlantic Ocean. The profiles from the continental slope of the Argentine and the Cape Basin indicate denitrification at about 3 cm. The profile from an oligo-trophic equatorial site shows no denitrification.

Fig. 2 Di ssolved oxygen, BOD and nitrate concentration-time profiles (25 °C wastewater).

Depth profiles from the eastern tropical North Pacific (Figure 24.8) show the effects of nitrogen metabolism under 02-deficient conditions. The thermocline is characterized by a sharp decline in O2 concentrations that coincides with increasing nitrate and phosphate concentrations. The oxycline is produced by the respiration of sinking POM under vertically stagnant conditions. Below the oxycline, in depths where O2 concentrations are suboxic, phosphate concentrations continue to increase, but at a slower rate. In contrast, nitrate concentrations decline and reach a mid-water minimum that coincides with a nitrite maximum. The latter is referred to as the secondary nitrite maximum. (At this site the primary nitrite maximum is located at 50 m.)... 

Vertical concentration profiles of (a) nitrate, (b) nitrite and phosphate, and (c) O2 and temperature in the eastern tropical North Pacific in August 1962 (15°N 100°W). The calculated nitrate concentrations were estimated by multiplying the observed phosphate concentrations by the average nitrate to phosphate ratio in the three deepest samples (11.9 1.6 xmolN/L). Source From Thomas, W. H. (1966). Deep-Sea Research 13, 1109-1114. 

Fig. 11.18 Concentration profiles for mixer-settler bank under total reflux system TBP (50%) from nitrate medium. (From Ref. 42.)... 

The breakthrough time observed in the NO, concentration profile indicates that during the initial part of the pulse the N O fed to the reactor is completely stored on the catalyst surface. As shown by FT-IR spectroscopy [inset (d) in Figure 13.12], the initial NO uptake occurs primarily in the form of nitrites, which are readily transformed into nitrates so that at the end of the NO pulse, at catalyst saturation, nitrates were the prevalent species. Notably, the rate of both nitrite formation and their oxidation to nitrates was higher on Pt-Ba/y-AbOj than on Ba/y-AbO, thus indicating a catalytic role of Pt. 

Figure 11, Concentration profiles of ammonium, nitrite, and nitrate in a plug...

Example 7.7 Absorption of ammonia vapor by lithium nitrate-ammonia solution The following modeling is from Venegas et al. (2004). For simultaneous heat and mass transfer during the absorption of ammonia vapor by lithium nitrate-ammonia (A) solution droplets, the ammonia concentration profile in the liquid phase can be estimated from the continuity equation without a source term... 

The various influences on the efficacy of UV disinfection are compiled in Fig. 9-1 (cf Malley Jr, 2000). Primarily, the efficacy of UV disinfection depends on the germicidal fluence Ho=EoXt which is the product of fluence rate Eq and the duration time t of the irradiation (often called UV dose , Chapter 2.1) (see Sommer et al., 1998). Other key factors include the hydraulics and hydrodynamics of the UV reactor (Kreft et al., 1986), its geometry (FIGAWA, 1998, Hoyer, 1996), the number and type of UV lamps required (Loge et al., 1996), their temperature profiles with respect to a maximum fluence rate Eq (in the case of LP Hg lamps, cf Fig. 4-8), the water quality and its variability such as UV absorbance/transmittance (Bolton et al., 2001, Sommer et al., 1997), the water matrix, e.g. nitrate concentration, its potential for quartz fouling by inorganic constituents particularly iron ions and hardness (cf Chapter 8-2), the turbidity, the particle content (total sus-... 

FIGURE 28 Metal concentration profiles along the length of a monolith for deposition precipitation by use of urea decomposition with nickel nitrate on a cordierite monolith. Metal deposited on a 25-cm-long, 1-cm-diameter, 400 cpsi monolith. Profiles were determined by X-ray fluorescence spectroscopy of finely ground 2.5-cm long sections of the monolith. 

Pore-water nitrate profiles in marine sediments typically show one of three profile shapes. In sediment with rapid rates of organic matter oxidation relative to rates of solute supply from the overlying water, both oxygen and nitrate concentrations decrease more or less exponentially from overlying water concentrations at the sediment—water interface to zero, with oxygen depletion preceding or simultaneous with nitrate depletion at shallow sediment depth (see 105 m and 440 m profiles in Fig. 6.12). These types of profiles are common in continental shelf and upper slope sediments, and are due to relatively large carbon rain to the sediments (relatively... 

Figure 34-4 Water column profiles of nitrate concentration (open symbols) and c5 N itrate (filled symbols) in the Eastern Tropical North Pacific (ETNP, coastal Baja California), Southern Ocean and North Atlantic (Sargasso Sea). The ETNP shows a large increase in c5 N i ate in the thermocline owing to local water column denitrification. The Southern Ocean shows little deviation from the global deep mean c5 N it te except at the surface, where partial NO3 assimilation leaves residual nitrate enriched in N. The North Atlantic profile shows low c5 N itrate in the thermocline owing to the nitrification of locally fixed N. Note that the ETNP profile also includes deep measurements from near Hawaii (diamonds) the smooth transition between samples at distant locations emphasizes the homogeneity of the deep Pacific.

We denote by Vr the volume of regenerant effluent recycled from one cation exchange cycle, and by Vea the volume of acid necessary for regeneration if it were used at the same concentration as in the production of ammonium nitrate or ammonium sulfate (55% for nitric acid and 98% for sulfuric acid). The acid is actually diluted twice, firstly when the regenerant solution is prepared and secondly in the resin bed by longitudinal diffusion wbich broadens the concentration profile at the front and tail. 

The presence of other materials in the impregnating solution can have a marked effect on the location of the metal within the support particle. These additives have been conveniently divided into three classes. Class 1 additives consist of simple inorganic electrolytes which influence the electrostatic interactions at the solution-support interface. Simple salts such as sodium nitrate, sodium chloride, or calcium chloride do not adsorb strongly enough on alumina to compete with platinum salts for adsorption. Fig. 13.9a 0 shows the concentration profile of platinum on an alumina particle when the impregnation of chloroplatinic acid was done in the absence of any additives. This a somewhat diffused egg shell profile. Fig. 13.9b shows the adsorption profile for the catalyst prepared by impregnation in the presence of an amount of sodium nitrate equimolar to the chloroplatinic acid. Here the amount of platinum adsorbed decreases while the adsorption profile approaches a uniform distribution. It is... 

Fignre 6.5 shows typical pore water profiles of oxygen and nitrate measured in organic rich sediments off Namibia summing up the net reactions described above. Due to nitrification, the highest nitrate concentrations are reached approximately at the oxygen penetration depth. At abont 3 cm depth, nitrate is consumed in the process of denitrification. The nitrate profile indicates an npward flnx into the bottom water and a downward flnx to the zone of denitrification. Both profiles are verified by the application of Equations 6.1 and 6.2 within the computer model CoTAM/CoTReM (cf. Chapter 15) as indicated by the solid and dashed lines. 

The rate-increasing portion of the nitration rate profile can readily be explained by the increasing concentration of nitronium ion up to about 90% sulfuric acid, at which point the nitric acid is essentially completely converted to nitronium ion. It is not clear exactly why the nitration rate declines thereafter however, it has been suggested that the effects of the medium on the aromatic activity coefficients are responsible. (13)... 

Nitronium ion can be ruled out as the oxidizing species in step (8) since its concentration, paralleled by the nitration rate profile, steeply climbs with increasing medium acidity. 

Pore-water concentration profiles of redox-sensitive ions (nitrate, Mn, Fe, sulphate and sulphide) and nutrients (ammonium and phosphate) demonstrate the effects of degradation of OM. In freshwater sediments, the redox zones generally occur on a millimetre to centimetre scale due to the high input of reactive OM and the relatively low availability of external oxidators, especially nitrate and sulphate, compared to marine systems. A typical feature for organic-rich freshwater sediments deposited in aerobic surface waters, is the presence of anaerobic conditions close to the sediment-water interface (SWI). This is indicated by the absence of dissolved oxygen and the presence of reduced solutes (e.g. Mn, Fe and sulphides) in the pore water. Secondary redox reactions, like oxidation of reduced pore-water and solid-phase constituents, and other postdepositional processes, like precipitation-dissolution... 

Silicate concentrations also can be used to distinguish different water masses. The most obvious example is at the Southern Ocean Polar Front (see Figure 2), which separates Antarctic Surface Water from the Subantarctic system. The silicate and nitrate concentration gradients across these Southern Ocean waters occur in different locations (in a manner similar to the distinct maxima in their vertical profiles). The high concentrations of silicate (50-100 pmol N ) south of the Polar Front result from wind-induced upwelling bringing silicate to the surface faster than the local biota can turn it into particulate silica. Turnover times between surface waters and... 

The nutrient uptake by vegetation contributes to nutrient reduction in the soil profile with time. In low-nutrient systems, plants can sequester nutrients from the subsurface soil layers and deposit them on soil surfaces through detrital accumulation and increasing the connectivity of nutrients with water. Vegetative water uptake and transpiration can increase the solute flux from water column into the soil (Figure 14.30). For example, Martin et al. (2003) showed a greater reduction of surface water nitrate concentration in experimental Typha mesocosms with greater rates of evapotranspiration. 

Here, BDC is 1,4-benzene-dicarboxylate (terephthalic acid) and Zn40(BDC)3 represents the MOF-5 imit composition. The reaction equilibrium can be shifted toward formation of the MOF product by tuning the concentration profiles of the solvent, the water released, or the nitrate ions produced. Since esterification reactions can be driven in both directions without difficulty, it appears evident that the stability of MOF materials in applications could depend on polar protic environments and pH values (128). 

Figure S.8 Typical concentration profiles for nitrate, nitrite, and ammonia (Q and during hydrogenation of a model drinking water at two different hydrogen pressures over a bimetallic Pdf 1 %)-Cu(0.3 %)/Al2 O3 catalyst...

Fig. 12.17 Chloride concentration profiles in concrete under severe corrosion environment in the presence of 9.9 17m nitrate inhibitor.

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