A comparison of water solubility enhancements of organic solutes by aquatic humic materials and commercial humic acids

Chiou, Cary T.; Kile, Daniel E.; Brinton, Terry I.; Malcolm, Ronald L.; Leenheer, Jerry A.; MacCarthy, Patrick

doi:10.1021/es00165a012

Cited by 367 publications

(262 citation statements)

References 12 publications

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“…Hydrophobic organic contami- nants, such as naphthalene etc., have strong affinity toward the hydrophobic groups of the humic substances, and their adsorption onto the natural particles acts mainly on the organic layers of the natural particles. Therefore, earlier investigations [10,11,[42][43][44][45] showed that sorption of hydrophobic organic contaminants (HOCs) by soils and sediments is dominated by partitioning into relatively homogeneous, lipophilic, gel-like humic matrices, which can be recognized as a partition or dissolution process and has the linear adsorption features. A number of more recent studies [12][13][14][15][46][47][48][49][50][51][52][53][54][55] , however, have indicated that such sorption often manifests substantial deviations from a linear partition model, provided that very low concentrations of HOCs are studied.…”

Section: Resultsmentioning

confidence: 99%

“…They can form molecular aggregates, dispersed in different colloidal states in solution or deposited on mineral surfaces [4,5] , and therefore, strongly influence a wide range of environmentally important processes. For example, they may modify the chemical speciation of trace metals, stabilize inorganic colloids via adsorption [6,7] , and significantly impact the fate and transport of hydrophobic organic pollutants in subsurface systems [8][9][10][11][12][13][14][15][16] . A better understanding of their morphology and the underlying adsorption and aggregation processes is therefore of fundamental importance.…”

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confidence: 99%

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AFM study on the adsorption and aggregation behavior of dissolved humic substances on mica

Zhou

Lü

et al. 2006

SCI CHINA SER B

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Humic substances constitute the major organic fractions of soils, sediments and natural waters, and play a dominant role in the binding, mobilization, transport and ultimate fate of organic contaminants in subsurface systems. In this paper, two humic acid samples, Guanting and Tianjin, with different origin and chemical compositions have been investigated with AFM imaging for their adsorption and aggregation behaviors on mica. While the Tianjin humic sample is found to form small spheres with 250 to 330 nm in diameter at lower concentrations, irregular loop-chain assemblies of hundreds of nanometer in diameter with the chain width of about 40 nm are dominant for the Guanting humic sample, which may attribute to the more polar aliphatic fractions in the chemical composition in the latter. The heterogeneous and polydisperse nature of humic substances with multiple structural features, such as sponge-like structures, perforated sheets, aggregate of spheres, branches and chain-like assemblies etc., is apparent at higher concentrations for both humic samples, showing morphologically new evidence for the dominant view of the humic dual-mode sorption model. With naphthalene introduced, the assemblies of Guanting humic substances clearly become more compact with significantly narrowed branches and less porous the perforated sheet-like structures. It is indicative of that smaller nanometer scale rings present along the perforated assemblies could potentially represent hydrophobic domains, which may facilitate the adsorption and aggregation of naphthalene onto the natural particle surfaces and therefore lead to an important role of dissolved humic substances in the sorption of environmental pollutants.Keywords: atomic force microscopy (AFM), dissolved humic substances, morphology, aggregation, adsorption.Humic substances (HS) are a category of naturally occurring, biogenic, heterogeneous organic materials found in or extracted from soils, sediments, and natural waters that can generally be characterized as being yellow-to-black in color, of highly variable relative molecular masses, and refractory [1,2] . Derived from a variety of organic precursors (plant biopolymers such as lignin etc.), plant residues and animal debris via both transformation and synthesis processes [3] under the profound geochemical alteration, including the microbiological and chemical degradation, sedimentation and diagenesis as well, humic substances com-AFM study on the adsorption and aggregation behavior of dissolved HS on mica 257 prise highly complex composites of partially or completely degraded biomolecules, carbohydrates, lipids, and proteins etc. However, they cannot be classified into any of the normal, easily defined categories of discrete materials such as proteins, polysaccharides, and polynucleotides. As the major organic constituents of soils, sediments and waters, humic substances are ubiquitous in all terrestrial and aquatic environments. They can form molecular aggregates, dispersed in different colloidal states in solutio...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

AFM study on the adsorption and aggregation behavior of dissolved humic substances on mica

Zhou

Lü

et al. 2006

SCI CHINA SER B

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“…On the other hand, it is widely recognized that sorption process of hydrophobic organic compounds onto dissolved natural organic matter (DOM) may significantly increase their aqueous solubility (Chiou et al, 1987;Yamamoto et al, 2003). This solubility enhancement affects the fate of these chemical species in an aquatic environment and water treatment processes (Yamamoto et al, 2003) but the increases in dissolved organic matter concentration result in decreases in bioavailability and the bioaccumulation of these chemicals while attenuating their toxicity.…”

Section: Article In Pressmentioning

confidence: 99%

Acute and chronic effects of testosterone and 4-hydroxyandrostenedione to the crustacean Daphnia magna

Barbosa

Nogueira

Soares

2008

Ecotoxicology and Environmental Safety

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a b s t r a c tSteroid compounds have been globally detected in surface waters. The ecological impacts of these biologically active chemicals are largely unknown. Toxicity of testosterone and 4-hydroxyandrostenedione was assessed for the freshwater cladoceran Daphnia magna. Acute toxicity tests showed that 6.20 mg L À1 of testosterone, the highest concentration tested, did not have effect on the daphnids, whereas 4-hydroxyandrostenedione had an EC 50 of 4.26 mg L À1 . Chronic toxicity tests were carried out using survival, body length, fecundity, and fertility as endpoints. Long-term testosterone exposure reduced D. magna fecundity and fertility at concentrations ranging from 0.31 to 2.48 mg L À1 . The significant decrease in fecundity was associated with an increase in aborted eggs. Long-term 4-hydroxyandrostenedione exposure at 0.84 mg L À1 increased the mortality of the neonates. The chronic toxicity effects were observed at concentrations higher than the measured environmental concentrations of these compounds. Nevertheless, the reproductive impairment of the daphnids is likely to occur at environmental levels as an ultimate response to long-term exposure.

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“…In addition, calculations of [HA] by using Eq. (2) showed that, in the case of A0C12, the available binding sites of 83% or above were occupied by the dye molecules under the conditions in Fig. 3; even in the case of AO having the smallest KDOC (Fig.…”

Section: Determination Of Binding Constantsmentioning

confidence: 87%

Determination of Equilibrium Constants for Binding of Acridine Orange and Its 10-Alkyl Derivatives to Dissolved Humic Substances by a Fluorescence Quenching Method

et al. 1990

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University,Fluorescence intensities of Acridine Orange and its 10-alkyl derivatives were reduced by the presence of commercial humic acid or dissolved humic substances obtained from river water, seawater and pond water samples. Synchronous changes in the absorption spectra and the virtually unchanged fluorescence lifetime of the 10-dodecyl derivative suggested that the fluorescence quenching could be explained on the basis of a static quenching mechanism, in which the fluorescence dyes were bound to humic substances to form non-fluorescent dye aggregates. Curve fitting procedures for the upwardly-curved Stern-Volmer plots yielded the equilibrium binding constants normalized to organic carbon content. The binding constants at pH 7.0 for fractions eluting at pH 2.4 -7.5 in a pH-gradient chromatographic separation of the aquatic humic substances were larger than those for fractions eluting at pH 8.2-11.4. Some chemical properties of the binding have also been discussed in terms of the electrostatic interaction and/or the hydrophobic interaction.

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A comparison of water solubility enhancements of organic solutes by aquatic humic materials and commercial humic acids

Cited by 367 publications

References 12 publications

AFM study on the adsorption and aggregation behavior of dissolved humic substances on mica

AFM study on the adsorption and aggregation behavior of dissolved humic substances on mica

Acute and chronic effects of testosterone and 4-hydroxyandrostenedione to the crustacean Daphnia magna

Determination of Equilibrium Constants for Binding of Acridine Orange and Its 10-Alkyl Derivatives to Dissolved Humic Substances by a Fluorescence Quenching Method

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