scholarly journals Humic Acid Extracts Leading to the Photochemical Bromination of Phenol in Aqueous Bromide Solutions: Influences of Aromatic Components, Polarity and Photochemical Activity

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 608
Author(s):  
Hui Liu ◽  
Yingying Pu ◽  
Xiaojun Qiu ◽  
Zhi Li ◽  
Bing Sun ◽  
...  
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Dissolved Organic Matter ◽  
Chemical Properties ◽  
Photochemical Activity ◽  
Simulated Solar Light ◽  
Geochemical Cycle ◽  
Reactive Halogen Species ◽  
Aromatic Components ◽  
Bromide Solutions

Dissolved organic matter (DOM) is considered to play an important role in the abiotic transformation of organobromine compounds in marine environment, for it produces reactive intermediates photochemically and is recognized as a significant source of reactive halogen species in seawater. However, due to the complex composition of DOM, the relationship between the natural properties of DOM and its ability to produce organobromine compounds is less understood. Here, humic acid (HA) was extracted and fractionated based on the polarity and hydrophobicity using silica gel, and the influences of different fractions (FA, FB and FC) on the photochemical bromination of phenol was investigated. The structural properties of HA fractions were characterized by UV-vis absorption, Fourier transform infrared spectroscopy and fluorescence spectroscopy, and the photochemical reactivity of HA fractions was assessed by probing triplet dissolved organic matter (3DOM*), singlet oxygen (1O2) and hydroxyl radical (•OH). The influences of HA fractions on the photo-bromination of phenol were investigated in aqueous bromide solutions under simulated solar light irradiation. FA and FB with more aromatic and polar contents enhanced the photo-bromination of phenol more than the weaker polar and aromatic FC. This could be attributed to the different composition and chemical properties of the three HAs’ fractions and their production ability of •OH and 3DOM*. Separating and investigating the components with different chemical properties in DOM is of great significance for the assessment of their environmental impacts on the geochemical cycle of organic halogen.

scholarly journals Uranyl binding to humic acid under conditions relevant to cementitious geological disposal of radioactive wastes

2012 ◽  
Vol 76 (8) ◽  
pp. 3391-3399 ◽  
Author(s):  
A. Stockdale ◽  
N. D. Bryan
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Dissolved Organic Matter ◽  
Equilibrium Dialysis ◽  
Radioactive Wastes ◽  
Experimental Results ◽  
Uranyl Ions ◽  
Geological Disposal ◽  
Ph Range ◽  
Competing Ions

AbstractFew studies have sought to investigate the potential for dissolved organic matter (DOM) to bind (and thus potentially transport) radionuclides under the high pH regimes that are expected in cementitious disposal. We have used equilibrium dialysis to investigate uranyl binding to humic acid over a pH range of ∼10 to 13. The experimental results provide evidence that DOM can bind uranyl ions over this pH range, including in the presence of competing ions. There is a general decrease in binding with increasing pH, from ∼80% of total uranyl bound at pH 9.8 to ∼10% at pH 12.9. Modelling of the system with WHAM/Model VII can yield representative results up to pH ∼10.5.

Genesis of podzols on coastal dunes in southern Queensland .III. The role of aluminum organic complexes in profile development

Soil Research ◽  
1992 ◽  
Vol 30 (5) ◽  
pp. 645 ◽  
Author(s):  
JO Skjemstad
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Organic Acids ◽  
Fulvic Acid ◽  
Matrix Material ◽  
Chemical Properties ◽  
Coastal Dunes ◽  
Total Carbon ◽  
Aluminium Content ◽  
Carboxyl Content

Organic matter was extracted sequentially with 0.1 M HC1, 0.5 M HCl and 0.5 M NaOH from three soil samples consisting of the dark brown organic nodules and matrix material from the Bhs2 horizon and the untreated Bhs3 horizon material of a freely drained podzol from Cooloola. The NaOH extract was further divided into fulvic and humic acid. After extracts were separated on G-50 Sephadex gel, titration data demonstrated that carboxyl groups in the collected fractions ranged from 8.8% to 61.3% of the total carbon although some overestimate of the carboxyl content may result from the chromic acid method used. Fractions excluded by the gel made up >95% of each extract and the first fraction collected in each case was the lowest in carboxyl content. These fractions from the 0-1 M HC1 extracts were generally low in carboxyl content (8.8%-24.9%) as were those from the humic acids (10.7-11.2%) although the major remaining humic acid fractions were extremely high (58.6-61.3510). The 0.5 M HCl and fulvic acid extracts appeared similar in chemical properties with carboxyl content of the separated fractions ranging from 16.4 to 44.0%. Molar absorptivities were in the order 0.1 M HCl < 0.5 M HC1< fulvic acid < humic acid. The pKa values of the acids were found to increase in the order humic acid < fulvic acid = 0.5 M HCl < 0.1 M HCl as well as in the order Bhs2 (dark brown nodules) < Bhs2 (yellow brown bulk) < Bhs3 for each fraction. Ease of flocculation of the extracts by aluminium counter ions decreased in the order humic acid > fulvic acid > 0.5 M HCl > 0.1 M HCl. It was demonstrated that other organic extracts low in aluminium content could be used to remobilize flocculated humic acid through redistribution of the aluminium bound to the precipitated phase into the solution phase. From these and other data, a hypothesis explaining the specific manner in which organic matter is arrested during podzolization is proposed. Some major factors appear to be (a) the pH of the horizon, (6) pKa and aromaticity of the organic acids and (c) availability of aluminium to the organic fractions. Remobilization of precipitated organic matter requires the presence of organic acids of low aluminium content in the percolating soil solution. This hypothesis adequately describes the process by which distinct Bh, Bhs and Bs horizons are formed and evolve during profile genesis.

Photochemical activity of mirex associated with dissolved organic matter

Chemosphere ◽  
1988 ◽  
Vol 17 (6) ◽  
pp. 1133-1146 ◽  
Author(s):  
Anand R. Mudambi ◽  
John P. Hassett
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Photochemical Activity

scholarly journals Combined organic amendment effects on eggplant yield, soil fertility characteristics and humic acid quality

1969 ◽  
Vol 100 (2) ◽  
pp. 101-122
Author(s):  
Ian C. Pagán-Roig ◽  
Joaquín A. Chong ◽  
José A. Dumas ◽  
Consuelo Estévez de Jensen
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Soil Fertility ◽  
Humic Acids ◽  
Organic Amendments ◽  
Chemical Properties ◽  
Soil Chemical Properties ◽  
Agricultural System ◽  
Vegetable Production ◽  
Amended Soils

Soil fertility and organic matter have been hindered due to unsustainable agricultural practices. There is a need to develop and better understand the effect of combined organic amendments that have the potential to increase soil fertility and agricultural system sustainability. Compost incorporations, the use of coordinated fallows and other biological amendments are alternatives to better the soil and increase crop yield. Information is scarce about the effect of combined organic amendments over soil chemical properties and their impact on vegetable production. The objective of the present study was to assess the effect of a combination of organic amendments we termed soil treatment management cycles (STMC) on soil chemical properties and eggplant yield in a San Antón soil. The STMC amendments consisted of incorporating organic matter from coffee pulp compost, planting and incorporation of a mixture of four green manure species, adding a mycorrhizae culture to the soil as well as compost tea. The different STMC were: control, no STMC (CL0); one STMC (CL1); two consecutive STMC (CL2); and three consecutive STMC (CL3). Results showed that CL1 was enough to significantly increase organic matter, P, K and S content in the soil compared with the non-amended soil. The concentration of Ca was significantly increased by three (CL3), and that of Mg by three (CL3) and two (CL2) STMC, compared to the other treatments. All treatments significantly changed soil pH, buffering it toward neutrality with increasing cycles when compared with pH 7.9 of no STMC control soils. Treatments CL1, CL2 and CL3 increased humic acid content 2.8, 3.8 and 5.9 times, respectively, when compared with CL0. Humic acids, extracted from unamended soils exhibited more condensation and more aromaticity when compared with those of amended soils. Nevertheless, the humic acids of amended soils showed high levels of polymerization. The enhancement in soil properties promoted by STMC resulted in an increase in eggplant fruit yield and biomass production.

Interaction of Hg(II) with kaolin-humic acid complexes

Clay Minerals ◽  
2004 ◽  
Vol 39 (1) ◽  
pp. 35-45 ◽  
Author(s):  
M. Arias ◽  
M.T. Barral ◽  
J . Da Silva–Carvalhal ◽  
J .C. Mejuto ◽  
D. Rubinos
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Dissolved Organic Matter ◽  
Equilibrium Concentration ◽  
Soluble Complex ◽  
Ph Values ◽  
Subsurface Waters ◽  
Ph Range ◽  
Surface And Subsurface Waters ◽  
Reduced Risk

AbstractThe adsorption and desorption of Hg(II) by humic acid (HA) previously adsorbed on kaolin was studied. In the range of HA concentration investigated (0.0 –26.9 mg g–1), the Hg(II) adsorption capacity of kaolin at pH 4 is enhanced by the presence of HA. For the complexes with the highest HA concentration and for low Hg(II) initial concentrations, adsorption was lower, i.e. as HA concentration on the complexes increases, Hg(II) equilibrium concentration also increases. This behaviour is due to the increasing presence of dissolved organic matter as the HA concentration on the complexes increases. The dissolved organic matter is able to form a soluble complex with Hg, thus decreasing adsorption. Hg(II) adsorption from a 2.5×10–5 MHg(II) solution was influenced by pH. For kaolin, a pHmax (pH where maximum adsorption occurs) of 4.5 was observed. At pH values >pHmax retention decreased with increasing pH. This same behaviour was observed for the kaolin- HA complex containing the lowest HA concentration (6.6 mg g –1). For the other kaolin-HA complexes there was little effect of pH on Hg(II) adsorption between pH 2.5 and pH 6.5. The presence of HA increased the adsorption of Hg(II) on kaolin all along the pH range studied. Desorption experiments showed that the amount of Hg(II) desorbed was quite low (<1%) for all the HA and Hg(II) concentration range studied, except for the kaolin at acid pH (pH 2.5) where the Hg(II) released was >50% of Hg(II) previously adsorbed. The presence of HA dramatically reduced this percentage of desorption to values of <3%, indicating reduced risk of toxicity problems in surface and subsurface waters. The addition of Cu(II) did not favour any Hg(II) desorption, even though Cu exhibits a strong affinity for organic matter.

LINKING OPTICAL AND CHEMICAL PROPERTIES OF DISSOLVED ORGANIC MATTER IN NATURAL WATERS

2013 ◽  
Vol 22 (3) ◽  
pp. 78-82 ◽  
Author(s):  
Christopher L. Osburn ◽  
Colin A. Stedmon ◽  
Robert G. M. Spencer ◽  
Aron Stubbins
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Natural Waters ◽  
Chemical Properties ◽  
And Chemical Properties

scholarly journals How humans alter dissolved organic matter composition in freshwater: relevance for the Earth’s biogeochemistry

2021 ◽  
Author(s):  
Marguerite A. Xenopoulos ◽  
Rebecca T. Barnes ◽  
Kyle S. Boodoo ◽  
David Butman ◽  
Núria Catalán ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Drinking Water ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Global Climate ◽  
Chemical Properties ◽  
Freshwater Ecosystems ◽  
Biogeochemical Processes ◽  
Dom Composition

AbstractDissolved organic matter (DOM) is recognized for its importance in freshwater ecosystems, but historical reliance on DOM quantity rather than indicators of DOM composition has led to an incomplete understanding of DOM and an underestimation of its role and importance in biogeochemical processes. A single sample of DOM can be composed of tens of thousands of distinct molecules. Each of these unique DOM molecules has their own chemical properties and reactivity or role in the environment. Human activities can modify DOM composition and recent research has uncovered distinct DOM pools laced with human markers and footprints. Here we review how land use change, climate change, nutrient pollution, browning, wildfires, and dams can change DOM composition which in turn will affect internal processing of freshwater DOM. We then describe how human-modified DOM can affect biogeochemical processes. Drought, wildfires, cultivated land use, eutrophication, climate change driven permafrost thaw, and other human stressors can shift the composition of DOM in freshwater ecosystems increasing the relative contribution of microbial-like and aliphatic components. In contrast, increases in precipitation may shift DOM towards more relatively humic-rich, allochthonous forms of DOM. These shifts in DOM pools will likely have highly contrasting effects on carbon outgassing and burial, nutrient cycles, ecosystem metabolism, metal toxicity, and the treatments needed to produce clean drinking water. A deeper understanding of the links between the chemical properties of DOM and biogeochemical dynamics can help to address important future environmental issues, such as the transfer of organic contaminants through food webs, alterations to nitrogen cycling, impacts on drinking water quality, and biogeochemical effects of global climate change.

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