Showing papers on "Humic acid published in 2014"
TL;DR: Results suggest that environmental aquatic concentration ranges of humic acids largely modify the stability of aggregated or dispersed ZnO nanoparticles.
245 citations
TL;DR: The HPO and TPI fractions were the major sources of superoxide, H2O2 and •OH under simulated solar irradiation and Autochthonous NOM showed a higher •OH productivity than terrestrial NOM.
Abstract: The formation of reactive oxygen species (ROS) from effluent organic matter (EfOM) was investigated under simulated solar irradiation. In this study, EfOM was isolated into three different fractions based on hydrophobicity. The productivity of ROS in EfOM was measured and compared with that of natural organic matter (NOM) isolates, including Suwannee River humic acid/fulvic acid (SRHA/FA) and Pony Lake fulvic acid (PLFA). The hydrophilic (HPI) component had a greater quantum yield of 1O2 than those of the hydrophobic (HPO) and transphilic (TPI) fractions because the HPI contained peptides and proteins. Regarding O2•-, the phenolic moieties acted as electron donating species after photochemical excitation and therefore electron transfer to oxygen. A positive correlation was found between the phenolic concentrations and the steady state O2•-concentrations. H2O2 accumulated during the irradiation process from superoxide as precursor. Potentially, due to the presence of proteins or other organic species in the HPI fraction, the decay rates of H2O2 in the dark for both the effluent wastewater and the HPI fraction were significantly faster than the rates observed in the standard NOM isolates, the HPO and TPI fractions. Autochthonous NOM showed a higher •OH productivity than terrestrial NOM. The [•OH]ss was lowest in the HPI fraction due to the lack of humic fraction and existence of soluble microbial products (SMPs), which easily reacted with •OH. Overall, the HPO and TPI fractions were the major sources of superoxide, H2O2 and •OH under simulated solar irradiation. The HPI fraction dominated the production of 1O2 and acted as a sink for H2O2 and •OH.
242 citations
TL;DR: Michael T. Rose, Antonio F. Patti, Karen R. Little, Alicia L. Brown, W. Roy Jackson, Timothy R. Cavagnaro, and W.Roy Jackson as discussed by the authors
Abstract: Michael T. Rose, Antonio F. Patti, Karen R. Little, Alicia L. Brown, W. Roy Jackson, Timothy R. Cavagnaro
236 citations
TL;DR: The decrease in aliphatic organics in HA demonstrated the degradation of the readily available organics, while an increase in aromatic functional groups indicated the maturity of compost.
229 citations
TL;DR: The coupled changes in optical and redox properties for the different HS suggest that phenols are an important determinant of aquatic HS optical properties and that quinones may play a more important role in soil HS.
Abstract: Two aquatic fulvic acids and one soil humic acid were irradiated to examine the resulting changes in the redox and photochemical properties of the humic substances (HS), the relationship between these changes, and their relationship to changes in the optical properties. For all HS, irradiation caused photooxidation, as shown by decreasing electron donating capacities. Photooxidation was accompanied by decreases in specific UV absorbance and increases in the E2/E3 ratio (254 nm absorbance divided by that at 365 nm). In contrast, photooxidation had little effect on the samples’ electron accepting capacities. The coupled changes in optical and redox properties for the different HS suggest that phenols are an important determinant of aquatic HS optical properties and that quinones may play a more important role in soil HS. Apparent quantum yields of H2O2, ·OH, and triplet HS decreased with photooxidation, thus demonstrating selective destruction of HS photosensitizing chromophores. In contrast, singlet oxygen...
187 citations
TL;DR: The three fractions of NOOM, humic and fulvic acids and natural organic matter and their concentrations were found to affect nano-TiO2 stability to different degrees although pH dependent trends in cation and anion effects had similar patterns.
149 citations
TL;DR: In this article, natural zeolite coated with titanium dioxide (TiO 2 ) was used as an adsorbent to rapidly remove humic acid (HA) from an aqueous solution.
140 citations
TL;DR: Analytical results for two in-vessel composting piles amended with biochar suggest that biochar amendment might be a potential method to enhance humification during pig manure composting.
135 citations
TL;DR: It was concluded that Al-HA complexation strongly affects the reaction pathways for Al hydrolysis and the final nature of the precipitates during PACl coagulation of HA and that the Hydrolysis products are also strongly affected by the characteristics of the PACl Coagulant.
130 citations
TL;DR: The present work investigates the potential of five extraction methods to estimate changes in soil-EPS content and concludes that using microbial ATP as an indicator of cell-lysis could only be ascribed to EPS extraction with cation exchange resin, and the expected increases in EPS-polysaccharide were clearly apparent.
Abstract: Many soil microbes exist in biofilms. These biofilms are typified by variable quantities of extracellular polymeric substances (EPS: predominantly polysaccharides, glycoconjugates, and proteins) and the embedded microbial cells. A method to measure soil-EPS (the biofilm exclusive of microbial cells) has not yet been described. The present work investigates the potential of five extraction methods to estimate changes in soil-EPS content. A rationale for selection of appropriate EPS extraction and methodology is discussed, including the crucial consideration of both intracellular and extracellular contamination.
EPS was developed in situ by provision of labile C (glycerol) to the microbial biomass of a moist soil and then applying desiccation stress. Only two out of the five extraction methods showed statistically significant increases in polysaccharide production responding to substrate addition. Humified organic matter, estimated by its humic acid equivalent (HAE) was used to indicate the degree of extracellular contamination, and/or creation of humic artefacts – both of which affect detection of changes in EPS. The HAE concentration was very high when applying original and modified methods designed to extract glomalin related soil protein (GRSP). Extraction methods involving heating with dilute sulphuric acid appeared to overestimate EPS-polysaccharide. Using microbial ATP as an indicator of cell-lysis, confidence could only be ascribed to EPS extraction with cation exchange resin. Using this method, the expected increases in EPS-polysaccharide were clearly apparent. The HAE/protein ratios of EPS extracts were also lowest with cation exchange – indicating this method did not cause excessive contamination from humified soil organic matter or create related artefacts.
126 citations
TL;DR: In this article, the adsorption of phosphate onto calcite-M was studied in a series of batch experiments and in a wide range of phosphate concentration (5 −160μm).
TL;DR: In this article, polysulfone membranes were prepared via phase inversion technique by using polyethylene glycol with molecular weights of 400, 1500 and 6000 Da as pore forming agent in dope formulation.
TL;DR: In this paper, the role of GRSP in sequestering Pb and Cd was investigated in an in situ field experiment and the effect of metal sequestration on GRSP was also investigated.
Abstract: Glomalin is a metal-sorbing glycoprotein excreted by arbuscular mycorrhizal fungi (AMF). One method of estimating glomalin in soils is as glomalin-related soil protein (GRSP). In this study the role of GRSP in sequestering Pb and Cd was investigated in an in situ field experiment. The effect of metal sequestration on the subsequent decomposition of GRSP was also investigated. GRSP was determined using the Bradford method as total glomalin-related soil protein (T-GRSP) and as easily extractable glomalin-related soil protein (EE-GRSP). After 140 days, GRSP bound Pb accounted for 0.21–1.78% of the total Pb, and GRSP bound Cd accounted for 0.38–0.98% of the total Cd content in the soil. However when compared on a soil organic matter (SOM) basis, only 4% of the Pb or Cd was bound to the GRSP fraction of the SOM compared with 40–54% of the Pb or Cd bound to the humin and fulvic acids in the SOM fraction. In soils contaminated with the highest levels of Pb and Cd, the T-GRSP (EE-GRSP) decomposition after 140 days was reduced by 8.0 (6.6)% and 7.0 (7.5)%, respectively, when compared with the controls. In the high Pb or Cd treatment groups we found that the fraction of metal bound to GRSP increased even though the total GRSP content declined over time. The mass ratio between Pb and GRSP-carbon changed from 2.3 to 271.4 mg (100 g) −1 in all Pb levels soil, while with the high-Cd treatment group the mass ratio between Cd and GRSP-carbon (0.36 mg (100 g) −1 ) was higher than the mass ratio seen with Cd-bound humic acid fractions. Our in situ field study shows that while GRSP does bind Pb and Cd, in the soils we investigated, the levels are insignificant compared to soil organic matter such as humic and fulvic acids.
TL;DR: Experimental results indicate that arsenic may form complexes with HA and FA with a higher affinity for arsenate than for arsenite, which may give insights on the complexation of arsenic in HA/FA laden groundwater and on the selection of more effective adsorption-based treatment methods for natural waters.
TL;DR: The different spectra presented by ALHA compared to those shown by the natural aquatic humic substances for all the fluorescence techniques studied suggest an important structural difference between them, which cast doubt on the use of commercial humic acids as surrogates for natural humic substance.
TL;DR: Electrostatic, hydrophobic and hydrogen bonding were the dominant types of interactions predicted, whilst divalent ion-mediated bonding was not identified in the simulations, which supported the LC-results.
TL;DR: In this article, the role of H 2 as reducing agent and CO 2 as buffer is discussed for the photocatalytic nitrate reduction in water by a 1%Pd-1%Cu (%wt) catalyst supported on TiO 2 under different reaction conditions.
TL;DR: In this article, a magnetic chitosan nanoparticle (MCNP) was first prepared by one-step in situ co-precipitation at low temperature and normal atmosphere to remove humic acid (HA) from aqueous solution.
TL;DR: In this article, the potential of catalytic ozonation of common water pollutants (volatile organic chemicals, pharmaceuticals and carboxylic acids, by-products) on ZSM-5 zeolites and investigate the effect of the nature of pollutants on the efficiency of the catalytic process.
Abstract: The results presented in this study aim to show the potential of ozonation of common water pollutants (volatile organic chemicals, pharmaceuticals and carboxylic acids, ozonation by-products) on ZSM-5 zeolites and to investigate the effect of the nature of pollutants on the efficiency of catalytic ozonation. Both the H-ZSM-5 and Na-ZSM-5 forms with different SiO2/Al2O3 ratios and counter ions (Z1000H:SiO2/Al2O3 = 1000, Z900Na:SiO2/Al2O3 = 900, Z25H:SiO2/Al2O3 = 25 and Z25Na:SiO2/Al2O3 = 25) have been used. The effects of pH, adsorption, presence of hydroxyl radical scavengers, phosphates and humic acids on the efficiency of catalytic ozonation have been investigated. The results revealed that catalytic ozonation on zeolites could substantially enhance the removal of VOCs and ibuprofen when compared with ozonation alone and that adsorption plays a key role in the effectiveness of this process. Zeolites with high SiO2/Al2O3 ratios were found to have a high adsorption capacity towards VOCs and as a result high catalytic activity. On the other hand zeolites with low SiO2/Al2O3 ratios had a high adsorption capacity towards ibuprofen in its ionised form. Catalytic processes have been found to be pH dependent with the highest activity at acidic pH. The presence of hydroxyl radical scavengers (phosphates and humic acid) did not have a significant effect on the removal of contaminants on ZSM-5 zeolites. Despite high activity towards VOCs and ibuprofen, zeolites did not catalyse the removal of acetic acid in water at studied pH values. It is therefore suggested that catalytic ozonation of organic pollutants on ZSM-5 zeolites proceeds via direct reactions of molecular ozone with pollutants adsorbed on the surface of zeolites.
TL;DR: In this article, cyclodextrin-modified graphene oxide nanosheets (denoted as CD/GO) were synthesized by an in- situ polymerization method and characterized by as well as Fourier transform-infrared spectroscopy, X-ray photoelectron spectrogram, Raman spectroscopic and potentiometric acid-base titration.
Abstract: Cyclodextrin-modified graphene oxide nanosheets (denoted as CD/GO) were synthesized by an in - situ polymerization method and characterized by as well as Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and potentiometric acid-base titration. The characterization results indicated that CD was successfully grafted onto GO surfaces by forming a chemical bond. Mutual effects on the simultaneous removal of hexavalent uranium and humic acid by CD/GO from aqueous solution were investigated. The results indicated that U(VI) and humic acid (HA) sorption on CD/GO were greatly affected by pH and ionic strength. The presence of HA enhanced U(VI) sorption at low pH and reduced U(VI) sorption at high pH, whereas the presence of U(VI) enhanced HA sorption. The surface adsorbed HA acted as a “bridge” between U(VI) and CD/GO, and formed strong inner-sphere surface complexes with U(VI). Sorption isotherms of U(VI) or HA on CD/GO could be well fitted by the Langmuir model. This work highlights that CD/GO can be used as a promising material in the enrichment of U(VI) and HA from wastewater in U(VI) and humic substances obtained by environmental pollution cleanup.
TL;DR: In this paper, ZnO-NPs with two different particle sizes, particle shapes, specific surface areas, and functional groups (OH group and carboxylic acid) were prepared through two different synthesis methods.
TL;DR: The results suggest that the primary substrate characterized by a more refractory character could increase the relative abundances of Firmicutes, Planctomycetes, and Actinobacteria, as well as associated cytochrome P450 genes, all of which should play important roles in the biotransformation of TOrCs in this natural treatment system.
Abstract: This study was performed to reveal the microbial community characteristics in simulated managed aquifer recharge (MAR), a natural water treatment system, under different concentrations and compositions of biodegradable dissolved organic carbon (BDOC) and further link these to the biotransformation of emerging trace organic chemicals (TOrCs). Two pairs of soil-column setups were established in the laboratory receiving synthetic feed solutions composed of different peptone/humic acid ratios and concentrations. Higher BDOC concentration resulted in lower microbial community diversity and higher relative abundance of Betaproteobacteria. Decreasing the peptone/humic acid ratio resulted in higher diversity of the community and higher relative abundances of Firmicutes, Planctomycetes, and Actinobacteria. The metabolic capabilities of microbiome involved in xenobiotics biodegradation were significantly promoted under lower BDOC concentration and higher humic acid content. Cytochrome P450 genes were also more abundant under these primary substrate conditions. Lower peptone/humic acid ratios also promoted the attenuation of most TOrCs. These results suggest that the primary substrate characterized by a more refractory character could increase the relative abundances of Firmicutes, Planctomycetes, and Actinobacteria, as well as associated cytochrome P450 genes, all of which should play important roles in the biotransformation of TOrCs in this natural treatment system.
TL;DR: The results indicated that the adsorption of Cu(2+) onto hematite and kaolinite in the absence and presence of humic acid is more conforming to pseudo second order kinetics.
TL;DR: It is clearly demonstrated that the role of structure and microporosity in Phen sorption is dependent on the sources of sorbents.
Abstract: Natural sorbents including one humic acid (HA), humins (HMs), nonhydrolyzable carbons (NHCs), and engineered sorbents (biochars) were subject to bleaching to selectively remove a fraction of aromatic C. The structural properties and sorption isotherm data of phenanthrene (Phen) by original and bleached sorbents were obtained. Significant correlations between Phen Koc values by all sorbents and their organic carbon (OC)-normalized CO2 cumulative surface area (CO2–SA/OC) suggested that nanopore-filling mechanism could dominate Phen sorption. After bleaching, natural sorbents still contained large amounts of aromatic C, which are resistant to bleaching, suggesting that they are derived from condensed or nonbiodegradable organic matter (OM). After eliminating the effect of aromatic C remaining in the bleached samples, a general trend of increasing CO2–SA/OC of natural sorbents with increasing aliphaticity was observed, suggesting that nanopores of natural sorbents are partially derived from their aliphatic mo...
TL;DR: This work presents a thoroughly validated method, the new standardized method for determination of HA and FA contents in raw humate ores and in solid and liquid products produced from them, which differs from previous methods in that it determinesHA and FA concentrations gravimetrically on an ash-free basis.
Abstract: Increased use of humic substances in agriculture has generated intense interest among producers, consumers, and regulators for an accurate and reliable method to quantify humic acid (HA) and fulvic acid (FA) in raw ores and products. Here we present a thoroughly validated method, the new standardized method for determination of HA and FA contents in raw humate ores and in solid and liquid products produced from them. The methods used for preparation of HA and FA were adapted according to the guidelines of the International Humic Substances Society involving alkaline extraction followed by acidification to separate HA from the fulvic fraction. This is followed by separation of FA from the fulvic fraction by adsorption on a nonionic macroporous acrylic ester resin at acid pH. It differs from previous methods in that it determines HA and FA concentrations gravimetrically on an ash-free basis. Critical steps in the method, e.g., initial test portion mass, test portion to extract volume ratio, extraction time, and acidification of alkaline extract, were optimized for maximum and consistent recovery of HA and FA. The method detection limits for HA and FA were 4.62 and 4.8 mg/L, respectively. The method quantitation limits for HA and FA were 14.7 and 15.3 mg/L, respectively.
TL;DR: In this paper, the role of humic acid and fulvic acid (FA) extracted from the natural soil, in the interaction mechanism and microstructure of Eu(III) with pyrolusite (beta-MnO2) by using batch experiments and extended X-ray absorption fine structure (EXAFS) techniques.
TL;DR: In this paper, a magnetically chitosan nanoparticle (MCNP) was used to adsorb humic acid from aqueous solution in a wide range of initial HA concentration.
TL;DR: Results from correlation analysis indicated that the responses of the foliar humic acid fertilizer on growth and development of chrysanthemum could be related with a constitutive increased net photosynthetic rate due to the high content of chlorophyll and the improved chloroplast ultrastructure.
TL;DR: Flocculation is positively influenced by the presence of biopolymers that are produced as the result of marine primary production and humic acid, which is abundant in the rivers that drain the agricultural soils of Southeastern United States, has little influence on flocculation.
Abstract: Riverine particles undergo a rapid transformation when they reach estuaries. The rapid succession of hydrodynamic and biogeochemical regimes forces the particles to flocculate, settle and enter the sediment pool. The rates and magnitudes of flocculation depend on the nature of the particles which are primarily affected by the types and quantities of organic matter (OM). Meanwhile, the OM characteristics vary widely between environments, as well as within a single environment due to seasonal climate and land use variability. We investigated the effect of the OM types and quantities through laboratory experiments using natural estuarine particles from the Mississippi Sound and Atchafalaya Bay as well as model mixtures of montmorillonite and organic molecules (i.e., biopolymers (guar/xanthan gums) and humic acid). Biopolymers promote flocculation but the magnitude depends on the types and quantities. Nonionic guar gum yields much larger flocs than anionic xanthan gum, while both of them exhibit a nonlinear behavior in which the flocculation is the most pronounced at the intermediate OM loading. Moreover, the effect of guar gum is independent of salinity whereas the effect of xanthan gum is pronounced at higher salinity. Meanwhile, humic acid does not affect flocculation at all salinity values tested in this study. These results are echoed in the laboratory manipulation of the natural estuarine particles. Flocculation of the humic acid-rich Mississippi Sound particles is unaffected by the OM, whereas that of biopolymer-rich Atchafalaya Bay particles is enhanced by the OM. Flocculation is positively influenced by the presence of biopolymers that are produced as the result of marine primary production. Meanwhile, humic acid, which is abundant in the rivers that drain the agricultural soils of Southeastern United States, has little influence on flocculation. Thus, it is expected that humic acid-poor riverine particles (e.g., Mississippi River, and Atchafalaya River, to a lesser degree) may be prone to rapid flocculation and settling in the immediate vicinity of the river mouths when mixed with biopolymer-rich coastal waters. It is also expected that humic acid-rich riverine particles (e.g., Pearl River) may resist immediate flocculation and be transported further away from the river mouth.
TL;DR: This work presents the innovative concept that Humic acid acts as a natural antidote of graphene by regulating its translocation and metabolic fluxes in vivo and can be used to control nanomaterial contamination.
Abstract: Graphene-related research has intensified rapidly in a wide range of disciplines, but few studies have examined ecosystem risks, particularly phytotoxicity. This study revealed that graphene significantly inhibits the number of wheat roots and the biosynthesis of chlorophyll, and altered the morphology of shoots. Humic acid (HA), a ubiquitous form of natural organic matter, significantly (P < 0.05) relieved this phytotoxicity and recovered the sharp morphology of shoot tips. Both graphene and graphene–HA were transferred from wheat roots to shoots and were found in the cytoplasms and chloroplasts. HA increased the disordered structure and surface negative charges, and reduced the aggregation of graphene. HA enhanced the storage of graphene in vacuoles, potentially indicating an effective detoxification path. The content of cadaverine, alkane, glyconic acid, and aconitic acid was up-regulated by graphene, greatly contributing to the observed phytotoxicity. Conversely, inositol, phenylalanine, phthalic acid...