Hydrophobicity and reactivity of trace metals in the low‐salinity zone of a turbid estuary

Turner, Andrew; Mawji, Edward

doi:10.4319/lo.2005.50.3.1011

Cited by 13 publications

(4 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, while the consequences of aqueous phase disequilibria on the adsorption of metals to natural solids have been observed, they do not appear to have been quantitatively or systematically addressed. For example, in several field studies it has been noted that adsorption of many complexing metals is not accompanied by reestablishment of the original aqueous speciation ( , ), at least within the time scale of experiments or measurements (on the order of a few hours to several days). Moreover, in controlled laboratory experiments, the extent of removal of strongly complexing metals by natural sorbents is dramatically reduced following a period of preequilibration of metal in the aqueous phase ( , ); thus, different apparent solid−aqueous phase equilibria arise that depend on the sequence of reactant introduction.…”

Section: Introductionmentioning

confidence: 99%

A Binary Aqueous Component Model for the Sediment−Water Partitioning of Trace Metals in Natural Waters

Turner

2007

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

A model defining the overall sediment-water partitioning of a chemical, K(D), and the partitioning of its conservative components, (K(D))i, is presented. With respect to many trace metals in natural waters it is proposed that, through strong and perhaps specific complexation, two independent aqueous components coexist and a binary form of the model is appropriate. For two components of a metal that exhibit unequal partitioning, an inverse relationship between K(D) and particle concentration is predicted. Published experimental measurements of K(D) for metals in river waters, derived under conditions which exclude variable concentrations of preexistent colloidal particles, displayed either an inverse dependence (Cu, Ni, and Pd) or little dependence (Cs) on particle concentration. Regarding the former, iterative fits with the binary model were better than empirical fits based on a third (colloidal) phase model, and suggested the presence of between about 10 and 75% of a particle-reactive component ((K(D))1 approximately 5 x 10(4) to 10(10) mL g(-1)) and 25 and 90% of a less reactive (e.g., strongly complexed) component ((K(D))2 < or = 2.5 x 10(3) mL g(-1)). Regarding Cs, data indicated the presence of a single component whose K(D) was on the order of 10(3) mL g(-1). These observations challenge the conventional means by which sediment-water partitioning is considered and modeled, and imply that a third phase is not always a prerequisite for the particle concentration effect frequently observed in laboratory and field studies.

show abstract

Section: Introductionmentioning

confidence: 99%

A Binary Aqueous Component Model for the Sediment−Water Partitioning of Trace Metals in Natural Waters

Turner

2007

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…One exception is the work of Turner and Mawji who used C-18 and liquid-liquid extractions to quantify and characterise the hydrophobic fraction of dissolved metals in natural waters. [23] Their octanol-water partition coefficients indicated that the hydrophobicity of metal complexes was both pH-and metal-dependent, [24,25] reaching a maximum in the range of pH 7-8, where the overall charge of the metal complexes was thought to be very low. Some of the metal complexes with dissolved organic matter (DOM) were also shown to be hydrophobic, and their prevalence was related to the nature, origin and concentration of the DOM [26] (Box 1).…”

Section: Introductionmentioning

confidence: 99%

When are metal complexes bioavailable?

Zhao¹,

Campbell²,

Wilkinson³

2016

Environ. Chem.

View full text Add to dashboard Cite

Environmental context. The concentration of a free metal cation has proved to be a useful predictor of metal bioaccumulation and toxicity, as represented by the free ion activity and biotic ligand models. However, under certain circumstances, metal complexes have been shown to contribute to metal bioavailability. In the current mini-review, we summarise the studies where the classic models fail and organise them into categories based on the different uptake pathways and kinetic processes. Our goal is to define the limits within which currently used models such as the biotic ligand model (BLM) can be applied with confidence, and to identify how these models might be expanded.Abstract. Numerous data from studies over the past 30 years have shown that metal uptake and toxicity are often best predicted by the concentrations of free metal cations, which has led to the development of the largely successful free-ion activity model (FIAM) and biotic ligand model (BLM). Nonetheless, some exceptions to these classical models, showing enhanced metal bioavailability in the presence of metal complexes, have also been documented, although it is not yet fully understood to what extent these exceptions can or should be generalised. Only a few studies have specifically measured the bioaccumulation or toxicity of metal complexes while carefully measuring or controlling metal speciation. Fewer still have verified the fundamental assumptions of the classical models, especially when dealing with metal complexes. In the current paper, we have summarised the exceptions to classical models and categorised them into five groups based on the fundamental uptake pathways and kinetic processes. Our aim is to summarise the mechanisms involved in the interaction of metal complexes with organisms and to improve the predictive capability of the classic models when dealing with complexes.

show abstract

“…The assertion that, in natural waters, hydrophobic species are conserved during the partition process is supported by independent measurements of the hydrophobic fraction of various trace metals in river and estuarine waters using solid-phase C18 extraction ( , ). Here, the hydrophobic fraction of dissolved metal has been observed to decrease following the addition of suspended particles, implying that hydrophobic species preferentially (ad)sorb to suspended particles.…”

Section: Resultsmentioning

confidence: 98%

On the Relationship between D_o_w and K_ow in Natural Waters

Turner

Williamson

2005

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

The relationship between the overall octanol-water partition coefficient of a mixture of related chemical species, D(ow), and the octanol-water partition coefficients of its components, (K(ow))i, is explored. One form of the relationship (model 1) is generally applicable but relies on definition of aqueous phase speciation at equilibrium with octanol. An alternative form of the relationship (model 2) circumvents this requirement but assumes that related species are conserved during the partitioning process and is explicitly dependent on the water to octanol volume ratio, Vw/Vo. The potential applications and limitations of each model for defining the hydrophobic characteristics of chemical species in natural waters are examined in the light of experimental partition results for dissolved Cu and Pb in river waters. Given the general difficulties in accurate speciation modeling of trace metals in natural samples, model 1 was only able to estimate a K(ow) (typically in the range 0.03-0.3) for a computed organically complexed fraction of metal (generally > 90%). However, by conducting partition "isotherms" as a function of Vw/Vo and, because of the buffering capacity of natural waters, by treating a sample as two distinct hydrophilic and hydrophobic "pools", model 2 was able to estimate both the abundance and K(ow) of a more specific group of species. Parameter values derived from the latter approach indicated that river waters comprise a relatively small pool (about 4-20%) of metal whose octanol-water partitioning is in the region of 15-150. Given that the free ion activity of strongly binding metals in natural waters is extremely small, the hydrophobic fraction may, in many cases, representthe most biologically and environmentally significant component of metal. Accordingly, the experimental and modeling approaches described herein could be of great significance to an improved understanding of the fate and impacts of trace metals in the aquatic environment.

show abstract

Hydrophobicity and reactivity of trace metals in the low‐salinity zone of a turbid estuary

Cited by 13 publications

References 35 publications

A Binary Aqueous Component Model for the Sediment−Water Partitioning of Trace Metals in Natural Waters

A Binary Aqueous Component Model for the Sediment−Water Partitioning of Trace Metals in Natural Waters

When are metal complexes bioavailable?

On the Relationship between D_o_w and K_ow in Natural Waters

Contact Info

Product

Resources

About

Hydrophobicity and reactivity of trace metals in the low‐salinity zone of a turbid estuary

Cited by 13 publications

References 35 publications

A Binary Aqueous Component Model for the Sediment−Water Partitioning of Trace Metals in Natural Waters

A Binary Aqueous Component Model for the Sediment−Water Partitioning of Trace Metals in Natural Waters

When are metal complexes bioavailable?

On the Relationship between Dow and Kow in Natural Waters

Contact Info

Product

Resources

About

On the Relationship between D_o_w and K_ow in Natural Waters