Interference of Soluble Silica in the Determination of Orthophosphate‐Phosphorus

Ciavatta, Claudio; Antisari, Livia Vittori; Sequi, P.

doi:10.2134/jeq1990.00472425001900040021x

Cited by 25 publications

(9 citation statements)

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“…It is possible that Si interference may have influenced MRP determination in this study, but we consider this unlikely. In particular, interference is negligible in solutions with relatively low Si to P ratios similar to those analyzed here, and is also minimized when a short reaction time and a relatively strong H 2 SO 4 concentration are used (as here) in the colorimetric procedure (Ciavatta et al, 1990).…”

Section: Methodsmentioning

confidence: 81%

Colloidal Phosphorus in Surface Runoff and Water Extracts from Semiarid Soils of the Western United States

2004

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Colloidal particles in runoff may have an important role in P transfer from soils to waterbodies, but remain poorly understood. We investigated colloidal molybdate-reactive phosphorus (MRP) in surface runoff and water extracts of calcareous arable soils from the semiarid western United States. Colloidal MRP was determined by ultrafiltration and operationally defined as MRP associated with particles between 1µm and 1 nm diameter, although a smaller pore-size filter (0.3 nm) was used to define the lower size limit of colloids in water extracts. In surface runoff from three calcareous soils generated by simulated sprinkler irrigation, colloidal MRP concentrations ranged between 0.16 and 3.07 1LM, constituting between 11 and 56% of the MRP in the <1-gm fraction. Concentrations were strongly correlated with agronomic and environmental soil-test P concentrations for individual soils. Water extracts of a range of similar soils contained two size fractions of colloidal MRP: a larger fraction (L0-0.21Lm) probably associated with fine clays, and a smaller fraction (3-0.3 nm) probably associated with Ca-phosphate minerals. Colloidal MRP was solubilized in the acidic medium of the colorimetric detection procedure, suggesting that a fraction of the filterable MRP in runoff from calcareous soils may not be as readily bioavailable as free phosphate in waterbodies. Our results suggest that colloidal MRP is an important but poorly understood component of P transfer in runoff from calcareous western U.S. soils and should be given greater consideration in mechanistic studies of the P transfer process. P HOSPHORUS TRANSFER in runoff from agricultural soils to watercourses can contribute to blooms of toxin producing cyanobacteria (blue-green algae) and other water quality problems associated with eutrophication (Foy and Withers, 1995;Leinweber et al., 2002). As a result, a considerable research effort has aimed to quantify P transfer from agricultural land, and data now exist for a range of soils and agronomic management practices (for a recent review see Haygarth and Jarvis [1999]). Meaningful interpretation of such data requires a thorough understanding of P speciation and the analytical procedures involved in its determination.Conventionally, it is considered desirable to know the concentration of free phosphate in runoff, because this is the form most readily available to algae in waterbodies (Reynolds, 1984). This is estimated by crude fractionation based on membrane filtration (typically 0.45-or 0.2-1.Lm pore size) and reaction with molybdate (Murphy and Riley, 1962), but rarely provides an accurate value of the true dissolved phosphate concentration in envi-

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Section: Methodsmentioning

confidence: 81%

Colloidal Phosphorus in Surface Runoff and Water Extracts from Semiarid Soils of the Western United States

2004

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“…Interferences in the [P] determinations from silicate ions (stemming from the glass dissolution) were minimized by employing the procedure of ref. [ 65 ]. pH, [Ca] and [P] values were measured in triplicate for each of the two independent BG45

–

preparations.…”

Section: Methodsmentioning

confidence: 99%

Contrasting In Vitro Apatite Growth from Bioactive Glass Surfaces with that of Spontaneous Precipitation

2018

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Body-fluid-exposed bioactive glasses (BGs) integrate with living tissues due to the formation of a biomimetic surface layer of calcium hydroxy-carbonate apatite (HCA) with a close composition to bone mineral. Vast efforts have been spent to understand the mechanisms underlying in vitro apatite mineralization, as either formed by direct precipitation from supersaturated solutions, or from BG substrates in a simulated body fluid (SBF). Formally, these two scenarios are distinct and have hitherto been discussed as such. Herein, we contrast them and identify several shared features. We monitored the formation of amorphous calcium phosphate (ACP) and its crystallization into HCA from a Na2O–CaO–SiO2–P2O5 glass exposed to SBF for variable periods out to 28 days. The HCA growth was assessed semi-quantitatively by Fourier transform infrared spectroscopy and powder X-ray diffraction, with the evolution of the relative apatite content for increasing SBF-exposure periods evaluated against trends in Ca and P concentrations in the accompanying solutions. This revealed a sigmoidal apatite growth behavior, well-known to apply to spontaneously precipitated apatite. The results are discussed in relation to the prevailing mechanism proposed for in vitro HCA formation from silicate-based BGs, where we highlight largely simultaneous growth processes of ACP and HCA.

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“…Confusion however often arises when the P measured in unfiltered and undigested samples by the latter method is considered as free "orthophosphate" or "inorganic" P . The Murphy-Riley procedure has been shown to also determine loosely bound inorganic and organic forms of P, as a result of either molybdenum-enhanced hydrolysis or hydrous ferric oxide-orthophosphate reactions, or interference with silica (Tarapchak, 1983;Ciavatta et al, 1990). Hence taking the Murphy-Riley determined (i.e.…”

Section: T Mardamootoo Et Almentioning

confidence: 99%

Agricultural Phosphorus Management for Environmental Protection: A Review

Mardamootoo¹,

Preez²,

Barnard³

2021

GEP

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This review addresses research done over the past 40 years on different aspects of agricultural phosphorus (P) management for environmental protection. Inputs of P are essential for profitable crop production. Long-term application of P to agricultural soils has resulted in elevated levels of soil P. This accumulation may be desirable from an agronomic point of view but it represents a threat to freshwater quality. Indeed, P in runoff from agricultural land is an important component of non-point source pollution and can accelerate eutrophication of lakes and streams. Even very small amounts of P can raise the concentration above the critical value for eutrophication. Excessive eutrophication restricts water use for recreation, industry, and drinking due to the increased growth of undesirable algae and aquatic weeds. Current concerns facing the environmentally sound management of P in agriculture are similar worldwide and revolve around agricultural, economic, and environmental compromises associated with balancing productivity with environmental values. Agricultural P management strategies should be geared towards ensuring that P, a finite earth resource, is not wasted and those soils do not become so enriched with P that there is an unnecessary risk of too much P being mobilized to water from agricultural fields. Approaches, such as soil P testing and either P models or indices have been studied and implemented to mitigate agricultural P losses. Apparently, P indices are preferred instead of P models for this purpose because they are more flexible. A holistic management strategy is therefore suggested by using soil P testing in conjunction with either a P index or a P model.

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Interference of Soluble Silica in the Determination of Orthophosphate‐Phosphorus

Cited by 25 publications

References 0 publications

Colloidal Phosphorus in Surface Runoff and Water Extracts from Semiarid Soils of the Western United States

Colloidal Phosphorus in Surface Runoff and Water Extracts from Semiarid Soils of the Western United States

Contrasting In Vitro Apatite Growth from Bioactive Glass Surfaces with that of Spontaneous Precipitation

Agricultural Phosphorus Management for Environmental Protection: A Review

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