The physiology of fish in acidic waters rich in dissolved organic carbon, with specific reference to the Amazon basin: Ionoregulation, acid–base regulation, ammonia excretion, and metal toxicity

2021 ◽  
Author(s):  
Carolyn Morris ◽  
Adalberto L. Val ◽  
Colin J. Brauner ◽  
Chris M. Wood
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Metal Toxicity ◽  
Amazon Basin ◽  
Ammonia Excretion ◽  
Specific Reference ◽  
Acid Base ◽  
Acidic Waters

scholarly journals New possibility for characterization of dissociation behaviour of supramolecular electrolytes: results obtained for the International Humic Substances Society standard and reference samples by coulometry

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Martina Klučáková
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Humic Substances ◽  
Functional Groups ◽  
Dissociation Constants ◽  
Fulvic Acids ◽  
Molecular Organization ◽  
Humic And Fulvic Acids ◽  
Acid Base ◽  
Reference Samples

Abstract Background Humic substances can be considered as polyelectrolytes with supramolecular character and complicated behaviour in water environment. The fractions of humic substances dissolved in water are the most active ones and determinative for their functioning in nature, where the proton-binding and dissociation ability play a crucial role. The dissociation behaviour of humic and fulvic acids can be affected by different circumstances including their concentration which is directly connected with the molecular organization of humic particles in solution and the accessibility of their ionizable functional groups. This study is focused just on these active fractions and their dissociation behaviour in the dependence on their content in studied system. Results Standards and reference samples of International Humic Substances Society were used. Flow-through coulometry was used to determine the total content of acidic functional groups in fulvic solutions and humic leachates. The amount of dissociated acidic groups was determined on the basis of potentiometry. Several differences between the behaviour of humic and fulvic acids were found. While whole samples of fulvic acids including the weakest functional groups were analysed, only the active dissolved humic fractions containing stronger acidic functional groups were characterized. The fractions containing higher amounts of the weakest functional groups remained insoluble. The dissociation degree of fulvic acids decreased with their increasing content, but a maximum on its concentration dependence obtained for humic acids was observed. Conclusions Two different values of dissociation constants were determined for each sample. The first was determined on the basis of the extrapolation of infinite dilution, second was determined as their average value in the region of high concentrations in which it was constant. Obtained values characterize the functioning of dissolved humic substances from point of view of their dissociation ability. The results obtained by this approach can help to predict the acid–base behaviour of dissolved organic carbon in soil and generally in nature. The acid–base behaviour of dissolved organic carbon depends on its ratio to water. It behaves differently in soil which is dry and in soil which is wet or saturated by water.

THE ROLE OF SORPTION IN CONTROL OF RIVERINE DISSOLVED ORGANIC CARBON CONCENTRATIONS BY RIPARIAN ZONE SOILS IN THE AMAZON BASIN

Soil Science ◽  
2007 ◽  
Vol 172 (4) ◽  
pp. 279-291 ◽  
Author(s):  
Sonya M. Remington ◽  
Brian D. Strahm ◽  
Vania Neu ◽  
Jeffrey E. Richey ◽  
Hil??ndia Brand??o da Cunha
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Amazon Basin ◽  
Riparian Zone ◽  
Carbon Concentrations
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