Potentiometric Titrations of Humic Substances: Do Ionic Strength Effects Depend on the Molecular Weight?

Ephraim, James H.; Pettersson, Catharina; Nordén, Maria; Allard, Bert

doi:10.1021/es00003a009

“…These are primarily treated as impermeable spheres and the electrostatic interactions on the surfaces are modeled using BSM (18,19). However, depending on their configuration and size, some humic molecules may have certain groups outside the gel that behave like normal monomeric molecules (1,20). Electrostatic interactions within this part of the HS are considered to be negligible.…”

Section: Electrostatic Effectsmentioning

confidence: 99%

Modeling the Acid–Base Properties and Metal Complexation of Humic Substances with the Stockholm Humic Model

Gustafsson¹

2001

Journal of Colloid and Interface Science

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“…In boreal regions, DOM consists mainly of humic substances, which are a complex and heterogeneous mixture of high molecular weight organic acids. Several studies have shown that the macromolecular structure of dissolved humic substances is affected by environmental factors like pH, ionic concentrations, and DOM concentration [1–5]. Several studies have also shown that the binding of metals [6,7] as well as the binding of organic compounds [8–11] to DOM is affected by these structural changes.…”

Section: Introductionmentioning

confidence: 99%

Effects of water hardness and dissolved organic material on bioavailability of selected organic chemicals

Akkanen

¹

,

Kukkonen

²

2001

Enviro Toxic and Chemistry

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The influence of water hardness and dissolved organic matter (DOM) on bioavailability of organic chemicals to Daphnia magna was studied by using benzo[a]pyrene (BaP), pyrene, atrazine, and 3,3',4,4'-tetrachlorobiphenyl (TCB) as model compounds. Two types of DOM were used, namely Lake Kontiolampi, Joensuu, Finland water (KL) and Nordic reference fulvic acid (NoFA) dissolved in artificial freshwater. Binding of the four contaminants by KL DOM decreased with increasing water hardness. Furthermore, increasing hardness reduced the binding of BaP and pyrene to NoFA. The binding of atrazine and TCB by NoFA was low and was not significantly affected by water hardness. In the DOM-free samples, the bioconcentration of the four contaminants in D. magna usually was not affected by water hardness. In the presence of DOM, the bioconcentration factors (BCFs) were lower (except for atrazine) than in the DOM-free controls. In the presence of both types of DOM, increasing water hardness resulted in higher BCFs for BaP. The bioconcentration of pyrene and TCB increased with increasing water hardness in the presence of KL DOM. In conclusion, the effects of DOM and water hardness on bioavailability of hydrophobic chemicals depend on the type of chemical and on the properties of DOM.

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“…In boreal regions, DOM consists mainly of humic substances, which are a complex and heterogeneous mixture of high molecular weight organic acids. Several studies have shown that the macromolecular structure of dissolved humic substances is affected by environmental factors like pH, ionic concentrations, and DOM concentration [1][2][3][4][5]. Several studies have also shown that the binding of metals [6,7] as well as the binding of organic compounds [8][9][10][11] to DOM is affected by these structural changes.…”

Section: Introductionmentioning

confidence: 99%

Effects of Water Hardness and Dissolved Organic Material on Bioavailability of Selected Organic Chemicals

Akkanen¹,

Kukkonen²

2001

Environ Toxicol Chem

4

2

0

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The influence of water hardness and dissolved organic matter (DOM) on bioavailability of organic chemicals to Daphnia magna was studied by using benzo[a]pyrene (BaP), pyrene, atrazine, and 3,3',4,4'-tetrachlorobiphenyl (TCB) as model compounds. Two types of DOM were used, namely Lake Kontiolampi, Joensuu, Finland water (KL) and Nordic reference fulvic acid (NoFA) dissolved in artificial freshwater. Binding of the four contaminants by KL DOM decreased with increasing water hardness. Furthermore, increasing hardness reduced the binding of BaP and pyrene to NoFA. The binding of atrazine and TCB by NoFA was low and was not significantly affected by water hardness. In the DOM-free samples, the bioconcentration of the four contaminants in D. magna usually was not affected by water hardness. In the presence of DOM, the bioconcentration factors (BCFs) were lower (except for atrazine) than in the DOM-free controls. In the presence of both types of DOM, increasing water hardness resulted in higher BCFs for BaP. The bioconcentration of pyrene and TCB increased with increasing water hardness in the presence of KL DOM. In conclusion, the effects of DOM and water hardness on bioavailability of hydrophobic chemicals depend on the type of chemical and on the properties of DOM.

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Potentiometric Titrations of Humic Substances: Do Ionic Strength Effects Depend on the Molecular Weight?

Cited by 36 publications

References 20 publications

Modeling the Acid–Base Properties and Metal Complexation of Humic Substances with the Stockholm Humic Model

Modeling the Acid–Base Properties and Metal Complexation of Humic Substances with the Stockholm Humic Model

Effects of water hardness and dissolved organic material on bioavailability of selected organic chemicals

Effects of Water Hardness and Dissolved Organic Material on Bioavailability of Selected Organic Chemicals

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