Phosphorus sediments

Phosphorus Distribution. The major sediment phosphorus fraction is that extracted by hydrochloric acid (Table III). Ammonium oxalate-oxalic acid solution extracts somewhat less phosphorus than hydrochloric acid, while sodium hydroxide as well as hydroxylamine extract much less. 

Phosphorus extracted from sediment by NaOH has been related to non-occluded, surface-exchangeable, bioavailable forms (22). Hydrochloric acid extraction yields occluded phosphorus incorporated in hydrous metal oxides, carbonate and phosphate minerals of sediment. Hydroxylamine reagent specifically removes hydrous manganese oxides, while amorphous hydrous oxides of iron and aluminijm are removed by the oxalate reagent. Total available sediment phosphorus analyses includes sediment organic phosphorus components in addition to the inorganic portion determined by the selective extraction procedures. 

The variation in total available sediment phosphorus concentration among the three sediment types shown in Table II is clear. A statistical analysis of this data shows that both the suspended sediment and particulate total phosphorus concentrations are greater than the bottom sediment value at the 99% confidence level. Phosphorus content increases in the sequence bottom sediment, suspended sediment, and particulate material in accordance with the increase in surface area (M. M. Reddy, New York State Dept, of Health, unpublished data, 1977). High surface area sediment components may adsorb phosphorus-containing substances,from the water column, increasing their phosphorus concentration. Another possible explanation includes dilution of bottom sediment by relatively inert primary minerals in the sand and silt size fractions. 

In the lower reaches of the Genesee River, the results of the extractions suggest that substances other than hydrous oxides are phosphorus sinks. This is evident where the amount of sediment phosphorus extracted by hydrochloric acid steadily increases down river, while the oxalate extractable phosphorus remains relatively constant. Schwertmann (2 ) emphasized that the results of such procedures are best considered as a measure of the relative amount of a phase or, more generally, a measure of an element s reactivity in a sediment under carefully controlled conditions. Laboratory experiments (Figure 8) show that phosphorus uptake by calcium carbonate, under simulated natural conditions, proceeds slowly. The large hydrochloric acid extractable component observed at Rochester may arise from slow uptake and subsequent mineralization of dissolved inorganic phosphorus by carbonate minerals. 

Several chemical reactions, including calcium carbonate and hydroxyapatite precipitation, have been studied to determine their relationship to observed water column and sediment phosphorus contents in hard water regions of New York State. Three separate techniques have been used to Identify reactions important in the distribution of phosphorus between the water column and sediments 1) sediment sample analysis employing a variety of selective extraction procedures 2) chemical equilibrium calculations to determine ion activity products for mineral phases involved in phosphorus transport and 3) seeded calcium carbonate crystallization measurements in the presence and absence of phosphate ion. 

Typical results for Genesee River watershed bottom sediment phosphorus contents are (phosphorus analysis, x (ug/g), (ug/g), h) total phosphorus, 560, 140, 99 NaOH extractable phosphorus, 58, 62, 98 HCl extractable phosphorus, 398, 99, 98 NH20H extractable phosphorus, 74, 63, 98 (NH )2C204 extractable phosphorus 184, 93, 83. Bottom sediment, suspended sediment, and particulate total phosphorus (560 ug/g, 770 ug/g, and 910 ug/g respectively) Increase as does specific surface area, across these fractions indicating that adsorption processes may be important in increasing sediment phosphorus concentrations. 

Sediment phosphorus extraction analyses show that hydrous iron oxides (extracted by (NH4)2C204) play a major role in the transport of sediment phosphorus. In northern areas of the Genesee River watershed calcium carbonate formation also appears to be Involved in phosphorus fixation. Ion activity product calculations for water column samples from the Genesee River consistently exhibit subsaturation with respect to the stable calcium phosphate phase, hydroxyapatite. Calcium carbonate, which can serve as a substrate for phosphate mineralization, shows an ion activity product below the solubility product in the Genesee River except during the summer low-rainfall season. 

Jensen, H. S., McGlathery, K. J., Marino, R., and Howarth, R. W. (1998). Forms and availability of sediment phosphorus in carbonate sand of Bermuda seagrass beds. Limnol. Oceanogr. 43, 799—810. 

Forms and availability of sediment phosphorus in carbonate sand of Bermuda seagrass beds. Limnol. Oceanogr. 43, 799-810. 

The range of riverine suspended particulate matter that may be solubilized once it enters the marine realm (e.g., the so-called reactive-F ) is derived from three sources. Colman and Holland (2000) estimate that 45% may be reactive, based on RSPM-P compositional data from a number of rivers and estimated burial efficiency of this material in marine sediments. Bemer and Rao (1994) and Ruttenberg and Canfield (1994) estimate that 35% and 31% of RSPM-P is released upon entering the ocean, based on comparison of RSPM-P and adjacent deltaic surface sediment phosphorus in the Amazon and Mississippi systems, respectively. Lower estimates have been published (8% Ramirez and Rose (1992) 18% Froelich (1988) 18% Compton et al. (2000). Higher estimates have also been published (69% Howarth et al. (1995). 

Gachter R. and Meyers J. S. (1993) The role of microorganisms in sediment phosphorus dynamics in relation to mobilization and fixation of phosphorus. Hydrobiologia 253, 103-121. 

Sediments generally represent both the largest sink and the largest source of phosphorus in aquatic systems (Baldwin et al., 2002). Therefore, information on sediment phosphorus speciation is important in understanding the aquatic biogeochemistry of phosphorus. However, like soils, sediments typically consist of a complex mixture of clay, silt, sand, organic matter, various minerals, micro- and macro-organ-isms and water and therefore represent a potentially difficult medium in which to study phosphorus speciation. 

Twinch, A. J. 1987. Phosphate exchange characteristics of wet and dried sediment samples from a hypertrophic reservoir implications for the measurement of sediment phosphorus status. Water Res. 21 1225-1230. 

In addition, the research on sediment phosphorus can supply information about the paleoenvironment. The information about the environment and biogeochemistry of phosphorus extracted from the South Sea shelf slope sediments showed that the supply of terrigenous phosphorus for the sea was steady overall. The change in phosphorus contents in different depths was the result of climate and environmental changes. The vertical distribution of phosphorus had an opposite trend to calcium carbonate and Cd in sediment. The ebb and flow between CO2 and in seawater calculated by chemical balance in-... 

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