The chemical control of soluble phosphorus in the Amazon estuary

Fox, Lewis E.; Sager, Shawn L.; Wofsy, Steven C.

doi:10.1016/0016-7037(86)90354-6

Cited by 133 publications

(58 citation statements)

References 31 publications

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“…Uptake of SRP is observed in spring while relatively small mid-salinity SRP sources are commonly found during the remainder of the year. These trends have been observed both near (Sharp et al, 1982) and away from (Edmond et aL, 1981;Kaul & Froelich, 1984;Fox et aL, 1986) industrial and agricultural sources. Two types of mid-salinity sources have been postulated: seasonal regeneration of organic material (Edmond et al, 1981;Kaul & Froelich, 1984) and desorption from suspended material (Sharp et al, 1982;Fox et al, 1986;Froelich, 1988).…”

Section: Introductionmentioning

confidence: 73%

Geochemistry and loading history of phosphate and silicate in the Hudson estuary

Clark

Simpson

Bopp

et al. 1992

Estuarine, Coastal and Shelf Science

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The loading history and geochemistry of soluble reactive phosphorus (SRP) and dissolved silica (D S i) are evaluated in the Hudson estuary using 16 years of axial transect data. SRP behaves atypically in the estuary. Profiles show conservative mixing between a large mid-salinity source and the freshwater and seaward end members. Order of magnitude calculations indicate that waste water treatment facilities (WWTFs) are the dominant mid-salinity SRP source. DSi profiles display behaviour more typical of other estuaries in the northeastern United States, showing conservative mixing during periods of high flow and a midsalinity source during periods of low flow. A single layered multi-box model is used to evaluate the loading history of SRP and DSi. Shortly after the New York State phosphate detergent ban of 1972, the SRP load dropped to two-thirds of that typical of the early 1970s. Loading of SRP remained at this level until the mid-1980s when construction began at the largest point source. During the construction phase (1984)(1985)(1986), SRP loading returned to the early 1970s level. Upon completion, the total load declined once again and by the end of the 1980s it reached a level approximately one-third of that existing prior to the detergent ban. Model calculations of observed DSi profiles do not show a similar timetrend. They suggest that during summer months dissolution of diatom tests is a major source of DSi; however, WWTF DSi loads also appear to be a significant source to the Hudson estuary.

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Section: Introductionmentioning

confidence: 73%

Geochemistry and loading history of phosphate and silicate in the Hudson estuary

Clark

Simpson

Bopp

et al. 1992

Estuarine, Coastal and Shelf Science

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“…Similarly, the increase of phosphate in the Tana oligohaline region of about 1 mmol L 21 is more consistent with the degradation of terrestrial plant organic matter rather than freshwater phytoplankton. This increase of phosphate could also be due to desorption from suspended particles, although this process occurs in the mesohaline region (e.g., Froelich 1988), and on the contrary abiotic removal can occur in the oligohaline region (e.g., Fox et al 1986). The decrease of POC would correspond to an increase of phosphate of about 1.3 mmol L 21 assuming a P : C molar ratio of 1 : 852 for terrestrial plant organic matter (Cross et al 2003).…”

Section: Discussionmentioning

confidence: 99%

Biogeochemistry of the Tana estuary and delta (northern Kenya)

Bouillon

Dehairs

Schiettecatte

et al. 2007

Limnology & Oceanography

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The estuarine mixing zone of the Tana River (northern Kenya) and an extensive deltaic area just south of the estuary were sampled in April 2004 with the aim of identifying the distribution, sources, and processing of particulate and dissolved organic carbon (POC, DOC) and inorganic carbon (DIC). C4 inputs from the catchment contributed ,50% to the POC pool in the Tana River and estuary, and in the mangrove creek water column and intertidal sediments. The d 13 C values of DOC, however, were typically much more negative than that of POC, indicating a substantially higher contribution by C3 and/or mangrove-derived carbon in the DOC pool. The undersaturation of O 2 , high pCO 2 , and the nonconservative nature of DIC and d 13 C DIC suggest a strongly heterotrophic water column, particularly in the freshwater part of the Tana and in the tidal creeks in the delta, where high additional inputs of organic matter were observed. However, some of these sites showed d 18 O DO signatures lower than the atmospheric equilibrium (i.e., +24.2%) indicative of significant O 2 production by photosynthesis. Therefore, the heterotrophic signature in the water column is likely the result of a strong interaction with the large intertidal areas, whereby respiratory activity in sediments and in the overlying water column during tidal inundation leave a marked signature on the water column. This is confirmed by the covariation between salinity-normalized total alkalinity and DIC, whose slope indicates an important role for anaerobic diagenetic processes. If our data are representative for other large river systems in the region, current estimates are likely to underestimate suspended matter and both inorganic and organic C fluxes to the Indian Ocean from tropical east Africa.

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“…For instance, suspended particles and organic aggregates, which can account for a significant fraction of riverborne P, desorb a fraction of their bound phosphorus as electrolyte concentrations increase toward the mouth of the estuary (Fox et al 1986;Froelich 1988). Furthermore, metal oxides carry a net positive charge at typical freshwater pH and a net negative charge at sea water pH (Barrow et al 1980).…”

Section: Acknowledgmentsmentioning

confidence: 99%

Phosphorus sorption characteristics of intertidal marsh sediments along an estuarine salinity gradient

Sundareshwar

Morris

1999

Limnology & Oceanography

130

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The phosphate sorption capacity of intertidal vegetated marsh sediments was measured along a salinity gradient in the Cooper River estuary, South Carolina. The phosphate sorption capacity of the surface sediments (0-10 cm) of a freshwater marsh was higher than the sorption capacity of sediments from brackish and saline marshes, and surface sediments had greater sorption capacity than subsurface (10-20 cm) sediments. These trends were opposite that of available phosphorus, which increased downstream and with depth. Freshwater marsh sediments trap phosphorus in a less-bioavailable form as evidenced by the low zero equilibrium phosphorus concentration (ZEPC) of the ambient sediment and low exchangeable phosphorus found there. Soil ZEPC values were similar to the in situ mean pore-water phosphate concentrations, which shows that sorption has a major effect on the spatial distribution of pore-water phosphorus along the estuarine salinity gradient. The magnitude of phosphorus sorption by the freshwater marsh sediments greatly reduced the pore-water phosphate concentration, while the phosphorus sorption properties of brackish and salt marsh sediments maintained in situ equilibrium pore-water phosphorus concentrations at surplus levels (with respect to its availability to plants). These differences in P sorption properties of the sediments can be explained on the basis of their physical and chemical characteristics. For instance, approaching the sea, the surface area of sediments declined, with freshwater marsh sediments (0-10 cm) supporting 8.5ϫ higher surface area than the salt marsh sediments. However, the sorption capacity of freshwater sediments was 33ϫ greater than that of salt marsh sediments, which indicates that other properties such as sediment mineral composition are important. The concentrations of important elements such as Al and Fe in sediments also declined downstream. The results suggest that the differences in phosphorus exchange properties among these marshes are a function of sediment type and sedimentary concentrations of Fe and Al. These in turn are related to the changes in ionic strength and associated parameters (e.g., pH) and physical sorting mechanisms.Phosphorus bioavailability (operationally defined here as the molybdate-reactive phosphorus) in wetlands is controlled by complex in situ biotic and abiotic processes. The latter include removal of dissolved phosphate from pore-water through sorption onto sediment particles and organic aggregates. Sorption-desorption processes within a sediment chemical environment are influenced by the mineral composition of the sediment. For example, P sorption is positively correlated with the amount of free iron oxide in acid sulfate soils (Jugsujinda et al. 1995). Furthermore, organic molecules can form complexes with metal ions such as iron (Fe) and aluminum (Al), which in turn can sorb phosphorus and reduce its bioavailability (Jones et al. 1993). This is consistent with the high phosphorus sorption capacity of mineral-rich, freshwater wetland sed...

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The chemical control of soluble phosphorus in the Amazon estuary

Cited by 133 publications

References 31 publications

Geochemistry and loading history of phosphate and silicate in the Hudson estuary

Geochemistry and loading history of phosphate and silicate in the Hudson estuary

Biogeochemistry of the Tana estuary and delta (northern Kenya)

Phosphorus sorption characteristics of intertidal marsh sediments along an estuarine salinity gradient

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