Phosphate surface water

The destiny of most biological material produced in lakes is the permanent sediment. The question is how often its components can be re-used in new biomass formation before it becomes eventually buried in the deep sediments. Interestingly, much of the flux of phosphorus is held in iron(lll) hydroxide matrices and its re-use depends upon reduction of the metal to the iron(ll) form. The released phosphate is indeed biologically available to the organisms which make contact with it, so the significance attributed to solution events is understandable. It is not clear, however, just how well this phosphorus is used, for it generally remains isolated from the production sites in surface waters. Moreover, subsequent oxidation of the iron causes re-precipitation of the iron(lll) hydroxide floes, simultaneously scavenging much of the free phosphate. Curiously, deep lakes show almost no tendency to recycle phosphorus, whereas shallow... 

In addition to its presence as the free element in the atmosphere and dissolved in surface waters, oxygen occurs in combined form both as water, and a constituent of most rocks, minerals, and soils. The estimated abundance of oxygen in the crustal rocks of the earth is 455 000 ppm (i.e. 45.5% by weight) see silicates, p. 347 aluminosilicates, p. 347 carbonates, p. 109 phosphates, p. 475, etc. 

Over 20% of the world s open ocean surface waters are replete in light and major nutrients (nitrate, phosphate, and silicate), yet chlorophyll and productivity values remain low. These so-called "high-nitrate low-chlorophyll" or HNLC regimes (Chisholm and Morel, 1991) include the sub-arctic North Pacific (Martin and Fitzwater, 1988 Martin et al, 1989 Miller et al, 1991), the equatorial Pacific (Murray et al, 1994 Fitzwater et al, 1996) and the southern Ocean (Martin et al.,... 

Figure 6.3. 5 "0 in surface water (data from Gat 1980) compared with that in biogenic phosphates of various mammals from many world regions (data shown in squares are from conventional phosphate analyses Longinelli 1984 Luz et al. 1984 Ayliffe and Chivas 1990 D Angela and Longinelli 1990 Yoshida and Miyazaki 1991 Huertas et al. 1995). For comparison, plotted as filled circles, are 8 0 values for tooth enamel analyzed by laser fluorination (six humans, one shark, and one wolf Kohn et al. 1996). 

Organophosphate ester hydraulic fluid components have also been detected in groundwater near a hazardous waste site (1.7 pg/L tributyl phosphate) (Sawhney 1989) and in surface water from a radioactive waste disposal site (triphenyl phosphate and tributyl phosphate) (Francis et al. 1980). Organophosphate... 

The iron cycle shown in Fig. 10.14 illustrates some redox processes typically observed in soils, sediments and waters, especially at oxic-anoxic boundaries. The cycle includes the reductive dissolution of iron(lll) hydr)oxides by organic ligands, which may also be photocatalyzed in surface waters, and the oxidation of Fe(II) by oxygen, which is catalyzed by surfaces. The oxidation of Fe(II) to Fe(III)(hydr)-oxides is accompanied by the binding of reactive compounds (heavy metals, phosphate, or organic compounds) to the surface, and the reduction of the ferric (hydr) oxides is accompanied by the release of these substances into the water column. 

The O2 content of the surface waters is lower at mid-latitudes because of higher temperatures, which lead to lower gas solubility. As shown in Figure 10.1a, the ther-mocline is characterized by a concentration minimum that increases in intensity from the Atlantic to the North Pacific. Note that the O2 minimum is less pronounced in the vertical profile from 45°S as compared to 9°N in the Atlantic Ocean because of close proximity to the site of AABW formation. Mid-water phosphate and nitrate maxima... 

As illustrated in Figure 10.8, surfece-water phosphate and nitrate concentrations are uniformly low at aU latitudes below 45°. In contrast, high-latitude surface waters are characterized by much higher concentrations. This causes the phosphate concentration in new NADW to range from 0.7 to 0.9 pM and 1.8 to 2.0 pM in AABW. As the water masses sink and travel through the ocean basins, their phosphate concentrations increase as sinking POM is remineralized. Thus, the phosphate concentration at any... 

Annuai mean surface water nutrient concentrations (ixM) of (a) phosphate, (b) nitrate, and (o) siiicate. Source-. After Conkright, M. E., et al. (2002). World Ocean Atlas 2001, Volume 4 Nutrients, NOAA Atias NESDiS 52, U.S. Government Printing Office (See companion website for coior version.)... 

Phosphorite A hydrogenous mineral that forms in surficial sediments underlying surface waters of high biological productivity. It is composed primarily of calcium phosphate that is biogenic in origin. 

Wet adhesion phenomena represent a potentially fruitful area of research since so little is known. Some of the important questions are (1) How does one measure quantitatively the magnitude of the adhesion when the coating is wet (2) What is the governing principle that determines whether or not water collects at an organic coating/metal interface (3) What is the thickness of the water layer at the interface and what determines the thickness A recent paper (1.) correlates the wet adhesion properties of a phosphated surface with the crystalline nature of the zinc phosphate at the metal surface. 

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