Speciation in Freshwaters

Filella, Montserrat; Town, Raewyn M.; Buffle, Jacques

doi:10.1002/9780470988312.ch8

Cited by 13 publications

(9 citation statements)

References 319 publications

(274 reference statements)

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“…The pH of water can have a marked effect on the species (chemical form) of metal ions and nutrients, and hence on bioavailability (Filella et al, 1995). Decreasing pH frequently also leads to increased levels of metal cations in the water column as a result of desorption from the surfaces of suspended particles.…”

Section: General Commentsmentioning

confidence: 99%

Review: Water quality in non-perennial rivers (with erratum)

Day

Malan

Abegunde

2019

WSA

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More than half the river-lengths of rivers in southern Africa dry up occasionally or – more commonly – seasonally. Here we review the literature on water quality (WQ) in non-perennial rivers (N-PRs), with emphasis on river management and southern African systems. Hydrological regimes cover a spectrum from relatively predictable and unvarying in perennial rivers, to unpredictable and highly variable in non-perennial rivers, which are complex, continually shifting mosaics of flowing water, standing-water pools and terrestrial habitats. N-PRs are uncommonly difficult to manage because they represent a limited source of water that is renewed unpredictably and is competed for by local people as well as being required by wildlife. Groundwater, and therefore its chemical and physical features, contributes significantly to base flow and to the maintenance of pools remaining in the bed when the river is not flowing. Water chemistry reflects catchment geology except in polluted systems. Salinity varies temporally, and spatially over three dimensions, and is the variable controlling the composition of the biotas of many N-PRs. Hydrological regimes are seldom predictable with any certainty; WQ varies naturally over time and space; groundwater often determines the WQ of surface water, especially in pools; and WQ in non-perennial rivers and pools may be affected by activities far upstream in the catchment. As yet we have no more than a sketchy understanding of the extent to which data on any one system can be applied to any other. Until we have a better understanding of these systems, the following basic principles should guide the management of WQ in N-PRs: (i) Rivers need to be assessed on a case-by-case basis. (ii) Understanding of the groundwater regime, including its chemistry, is crucial. (iii) Effluents need to be controlled by conservative effluent standards set for both ground and surface waters. (iv) Flows may need to be augmented at certain times of the year.

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Section: General Commentsmentioning

confidence: 99%

Review: Water quality in non-perennial rivers (with erratum)

Day

Malan

Abegunde

2019

WSA

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“…Potentiometry using ion selective electrodes (ISE) is an adequate technique for metal speciation because it responds to the activity of an individual ion, and the natural distribution of species in the sample is not disturbed during the measurement [16]. However, with these inherent advantages, the use of potentiometry at ISEs for trace element determination in unpolluted waters is limited due to the lack of sensitivity required for direct measurements (lower limits of linear response usually ranging from 10 À6 to 10 À7 M) [8], and to the interfering effects caused by other ions present in the analytical matrix.…”

Section: Introductionmentioning

confidence: 99%

Speciation of Inorganic Arsenic in Waters by Potentiometric Flow Analysis with On‐Line Preconcentration

Rodríguez¹,

Barrado²,

Vega³

et al. 2005

Electroanalysis

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A potentiometric flow system has been developed for the direct determination of arsenic(V) in water samples after on-line preconcentration in a minicolumn packed with a new adsorbent material selective to As(V). Iron oxyhydroxide embedded in silica gel was synthesized and used simultaneously as adsorbent material in the minicolumn and as selective component in a tubular potentiometric electrode. In the first step, the sample solution is mixed on-line with phosphate buffer of pH 7 and pumped through the minicolumn to adsorb As(V). The insertion of the minicolumn in the mobile section of a homemade injector-commutator allows to relocate the minicolumn to desorb the retained As(V) in the second step. The desorption is maximum in the presence of 0.1 M phosphate of pH 12. Maximum response of the tubular selective membrane is achieved in phosphate buffer of pH 7. On-line oxidation of As(III) to As(V) by iodine (I 3 À ) in the presence of phosphate buffer of pH 7 allows the determination of total As as As(V) and then the speciation of inorganic arsenic, since As(III) can be estimated as the difference between total As and As(V). In the optimized experimental conditions, a linear range of 40 -500 mg L À1 for As(V), and detection limits of 30.6 and 38.6 mg L À1 for As(V) and total As, respectively, were obtained.The flow system has been successfully applied to the determination of inorganic arsenic species in groundwater samples collected in areas affected by arsenic contamination. Relative standard deviation of replicated determinations of As in groundwater samples was always below 5%.

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“…Les techniques de spéciation peuvent être regroupées en deux catégories : (i) celles où des fractions opérationnellement définies du métal total sont détectées, et (ii) celles mesurant les concentrations métalliques totales (Filella et al, 1995 (Farrah et Pickering, 1993). Ces problèmes sont : (i) possibles changements de la spéciation d'un élément au cours des étapes successives d'extraction et de rinçage de l'échantillon après chaque étape (Rosenberg et Ariese, 2001) ; (ii) risques multiples de contamination de l'échantillon par l'utilisation successives de réactifs (Quevauviller, 1998).…”

Section: Choix De La Procédure D'extractionunclassified

“…Tous ces métaux sont différemment réactifs, toxiques ou biodisponibles pour le biota (Gómez-Ariza et al, 2001). De ce fait, la mesure de la concentration totale des ions métalliques en solution n'apporte que peu d'informations pour la prédiction du comportement métallique (Filella et al, 1995). C'est alors qu'une analyse de spéciation, selon l'IUPAC (International Union for Pure and Applied Chemistry), correspondant à l'activité analytique d'identification et de mesure de la quantité d'une ou plusieurs espèces chimiques individuelles dans un échantillon (Templeton et al, 2000), s'impose.…”

Section: Introductionunclassified