HA Fractions Research Articles

Reduction of hexavalent chromium by compost-derived dissolved organic matter.

Compost-derived dissolved organic matter (DOMC) is a heterogeneous assemblage of different redox-active organic molecules. We hypothesize that DOMC can interact with Cr(VI) and reduce it to Cr(III), thereby influencing the dynamics of Cr(VI) in soil and aquatic environments. Here, DOMC, along with soil humic substances isolated from red soil and black soil, were fractionated into humic acid fractions (i.e., HAC, HAB, and HAR) and fulvic acid fractions (i.e., FAC, FAB, and FAR), respectively. The reduction and interaction between Cr(VI) and the six organic matter fractions were investigated. The results showed that the total Cr(VI) reduction capacity (TRC) of the six organic matter fractions was 26.77-49.34 μM Cr(VI) per mg OM. The TRC of HA fractions was 35.54-49.34 μM Cr(VI) per mg OM, which exceeded that of FA fractions (26.77-31.29 μM Cr(VI) per mg OM). DOMC had a HA/FA ratio of 0.64, which was higher than that of black soil humic substance (0.59) and red soil humic substance (0.20). The sum of the TRC of DOMC was 35.57 μM Cr(VI) per mg OM, which was larger than that of black soil humic substance (32.87 μM Cr(VI) per mg OM) and red soil humic substance (33.01 μM Cr(VI) per mg OM). The TRC was positively correlated with TOC, TN, phenol C, alkyl C, and aromatic C contents and negatively correlated with E2/E3, O-alkyl C, and carboxyl C contents. The reduction of Cr(VI) at pH 6 was negligible, whereas 32-67% Cr(VI) was reduced at pH 2. The Cr(VI) reduction capacities (RC2, RC2, and RC6) at pH 2-6 were positively correlated (R2 > 0.71) with phenol C. Spectral analysis showed that there was no obvious complexation between Cr(VI) and the six organic matter fractions at pH 6, and thus the reduction of Cr(VI) was negligible, but solution pH could affect the accessibility of organic molecules to Cr(VI) and thus influence Cr(VI) reduction.

Isolation of Phenolic Acids from Land Kale (Ipomoea reptans Poir) and Antioxidant Activity

Land kale or Ipomoea reptans Poir is widely consumed by Indonesian people. Land kale plants can be used as natural antioxidants because they contain polyphenolic compounds, one of which is phenolic acid. This research was carried out to determine the antioxidant activity and isolate phenolic acid compounds contained in land kale plants (Ipomoea reptans Poir). The sample used was an ethanol extract of land kale. The total phenolics were determined using the Folin-Ciocalteu method. Phenolic acids were isolated using alkaline hydrolysis and acid hydrolysis and without hydrolysis methods. Separation of isolates was carried out using the TLC method. The structure was identified using UV-Vis spectrophotometry and LC-MS/MS. Antioxidant activity was measured using the DPPH method. The total phenolics of land kale ethanol extract were 71.2420 ± 0.0791 mg/g GAE. TLC showed that the HB, HA, and TH fractions contained caffeic acid and ferulic acid compounds. Separation of the (HB) fraction produced three isolates: B2 with a yellow color, B3 with a slightly yellowish color, and B4 which is colorless. Isolate B2 was identified as potentially containing caffeic acid, while isolate B3 was indicated to potentially contain ferulic acid through analysis using a UV-Vis spectrophotometer. Isolate B4 was thought to have a hydroxybenzoic acid framework after being determined using LC-MS/MS. The ethanol extract of land kale has strong antioxidant activity because it produces an IC50 value of 94.83 mg/L.

Effect of particles size on adsorption isotherm of chlorantraniliprole, dinotefuran, bispyribac-sodium, and metribuzin into sandy loam soil

The efficiency of different sorbents (bulk soil, sand, silt, clay and humic acid-HA) for chlorantraniliprole (CAP), dinotefuran (DNF), bispyribac-sodium (BPS), and metribuzin (MBZ) adsorption was described and compared. The adsorption of CAP, DNF, BPS and MBZ were significantly greater on clay and HA fractions than the bulk soils. Also, the tested pesticides sorption was greater on HA fraction compared to clay fraction except in the case of BPS. The mass unit of bulk soil adsorbed of CAP, DNF, BPS and MBZ approximately 15, 20, 10 and 5 % of the same of HA and 40, 60, 95 and 35 % of that of clay fraction, respectively. The actual amounts adsorbed on bulk soil ranged from (88.63 to 93.93 %) of the calculated amounts adsorbed on all soil components indicating high efficiency of the tested soils to adsorb tested pesticides. All adsorption data fitted well to the linear Freundlich equation. The adsorption of tested pesticides in soil and their different constituents is S-type according to 1/n (except some cases).

Antioxidant potential of humic substances measured by Folin-Ciocalteu, CUPRAC, QUENCHER-CUPRAC and ESR methods

An increasing proportion of the population in the Western world suffers from one of the oxidative stress related diseases. Although the radical-scavenging and therapeutic potential of humic substances (HSs) are known, little is known about their antioxidant properties and structure-property relationships. The aim of the research is to reveal the antioxidant potential of different HS samples and to compare them with already well-known antioxidants like gallic acid and Trolox. We determined the total phenolic content (TPC) of the samples using Folin-Ciocalteu (FC) method because it is generally associated with the antioxidant effect. We also applied the CUPRAC (CUPric Reducing Antioxidant Capacity) and QUENCHER-CUPRAC methods to achieve a comprehensive picture about the antioxidant potential of HSs. Furthermore, we tested the HS samples using electron spin resonance (ESR) method as a new tool to characterize the antioxidant properties. According to the results of FC method given in gallic acid equivalent antioxidant capacity (GAEAC) the HA fractions contain the most phenolic moieties (300–470 mg GAE/g) which is followed by the HY (150–175 mg GAE/g) and then FA (80–155 mg GAE/g). The antioxidant capacities of HS samples were related to Trolox (Trolox equivalent antioxidant capacity (TEAC)) in addition to gallic acid (GAEAC), namely 5–35 µmol GAE/g, 50–310 µmol TE/g and 12–42 µmol GAE, 175–530 µmol TE /g obtained by CUPRAC and QUENCHER-CUPRAC methods, respectively. The ESR results supported that the tested HS samples have antioxidant properties. Moreover, we compared the results of our fractions with the standard samples of the IHSS, in terms of origin and extraction methods. We could conclude that, in addition to the source of raw materials for the fractions, the method of their extraction also greatly influences their antioxidant effect.

Differences in structure and composition of soil humic substances and their binding for polycyclic aromatic hydrocarbons in different climatic zones

Humic substances (HSs) play important roles in the transport and bioavailability of hydrophobic organic compounds (HOCs) in soils. The sorption of HOCs depends on the compositions and structures of HSs which may differ in different climatic zones, however, the sorption behavior of HOCs by HSs in soils from different climatic zones is poorly understood. In this study, different HS fractions (humic acids-HAs, fulvic acids-FAs and humin-HM) in soils from different climatic zones were extracted and used as sorbents for polycyclic aromatic hydrocarbons (PAHs). The results indicated that HSs (including HA, FA and HM fractions) from colder climatic zones contained more oxygen-containing functional groups and exhibited smaller molecular weight as well as higher aliphaticity and polarity than those from warmer climatic zones. The sorption affinity of HAs at the low given concentration (0.05 Sw) of naphthalene (Nap), phenanthrene (Phe), pyrene (Pyr) and benz(α)anthracene (BaA) from warmer climatic zones to colder ones increased from 26.3 to 43.9, from 36.7 to 114.0, from 125.8 to 388.8, and from 322.5 to 876.1, respectively, and the same trends were obtained for FAs and HM at the same PAH concentration. The results indicated that HSs from colder climatic zones showed higher sorption affinity than those from warmer climatic zones. Moreover, the weighted contributions of FAs, HAs and HM to the overall sorption from different climatic zones were 9.1–28.4%, 13.5–59.2% and 23.4–76.9%, respectively. This indicates FA fraction, a previously neglected component, is also an important contributor to binding PAHs in soils. This study suggests that the difference in sorption behaviors of HOCs to HSs among different climatic zones should be considered when predicting HOC fates and bioavailability in soils.

Ratio of elements in humic acids extracted from restored mine soil as a measure of quality of carbon sequestered

Mining land loses large amounts of C (carbon) due to loss of topsoil and mechanical mixing of soil horizons. Biological reclamation of this soil stimulates SOC sequestration. A chronosequence study consisting of 8, 14 and 25years old reclaimed mine soils under Azadirachta indica,Gmelina arborea, Dalbergia sissoo at Gevra, Chhattisgarh, India was initiated to quantify the composition and ratios of humic acid. Carbon content of humic acid was highest in the case of Azadirachta indica followed by Gmelina arborea and Dalbergia sissoo. It had increased from 34.95% to 41.94%, 16.31% to 28.65% and 18.50% to 21.16% for Azadirachta indica, Dalbergia sissoo and Gmelina arborea with increase in year of reclamation for surface soil. Humic acid nitrogen content was found highest in the case of Azadirachta indica followed by Dalbergia sissoo and Gmelina arborea. N (%) in humic acid ranged from 1.29 for Gmelina arborea and 2.65 for Azadirachta indica. Highest C/N ratio was observed in case of Gmelina arborea. The C/N ratios of HA fractions ranged from 30.91 in Gmelina arborea to 15.27 in Azadirachta indica plantations. In case of C/H ratio, it ranged from 6.26 to 15.01 in restored mine soils. Thus, C/H ratio was significantly differing with slightly wider ratios in increasing depths. From elemental composition, it is evident that HAs contained more C than N and H. From the results of experiment we can say that humic acid C and N content improved with increase in year of reclamation due to enrichment in TOC and process of humification.

Organo-metallic complex and its implications

Complex formation is the reaction of a metal ion and ligands through electron pair sharing and the resulting product is called the metal coordination compound. The metal ion is the electron-pair acceptor, and the ligand is the electron-pair donor. The metal ion serves as the central ion, and the organic ions are coordinated around it in a first coordination sphere.Covelo et al., 2008 studied the heavy metal sorption and desorption behavior of a Fibric Histosol with that of its organo mineral fraction (OMF) and reported that greatest sorption capacity was for lead and copper. Urrutia et al., 2013 studied the physico-chemical characteristics of diverse types of humic-metal-phosphate acid complexes and reported that molecular size distribution of humic-metal-phosphate as a function of pH is similar to that of potassium or sodium humates and metal-humate complexes. Eshwar et al., 2017 studied the stability constant of Fe(II), Cu(II), Mn(II) and Zn(II) metal ion complexes with HA/FA at pH 7 and at 30 ⁰C and reported that for humic acid the log k values was highest for Cu (II) and in case of fulvic acid the log k values was highest for Mn (II). Mukhopadhyay and Sanyal, 2004 studied the release potential of arsenic (As) from arsenic-humic/fulvic complexes by soluble phosphate nitrate salt and examined it in terms of the appropriate exchange isotherms and reported that phosphate had a greater degree of exchangeability with arsenic than did nitrate, at both the lower and higher concentrations and also reported that stability constant of synthetic HA/FA were greater than that of natural HA/FA.Sinha and Bhattacharyya, 2011 studied the release isotherm of As from the HA/FA complexes extracted from vermicompost and FYM in presence of molybdate, nitrate, phosphate, sulfate and borate and reported that the greatest tendency to displace As from the complexes was shown by sulphate, molybdate, and nitrate. Datta et al., 2001 studied the stability constant of complexes formed by the humic acid with Cd2+ ions in aqueous phase and reported that humic phenolic-OH group was involved in the formation of Cd2+ -humic complexShahid et al., 2012 studied the effects of different organic ligands like ethylene diamine tetra-acetic acid (EDTA), low molecular weight organic acids, humic substances on lead speciation and reported that EDTA forms soluble, stable, and phytoavailable Pb-chelates due to high binding lead affinity. He et al., 2016 studied the binding behavior of Cu+2 to all ten HA fraction and reported that the FTIR and SEM-EDX image of HA fraction revealed that carboxyl and phenolic groups were responsible for the Cu2+ sorption on the ten sequentially extracted HA fractions process. Higher molecular weight humic acids bind heavy metals more strongly than low molecular weight acids, and the study of soil organic fractions that can sorb heavy metals moderating its toxicity in the soil/crop system and preventing its entry in the food chain should be explored in future.

Selective adsorption of soil humic acid on binary systems containing kaolinite and goethite: Assessment of sorbent interactions

Inorganic colloids are ubiquitous in soils and coexist as simple mixtures or as strong associations of particles. The coexisting inorganic colloids with a variety of active sites can selectively adsorb humic substances and thus affect the availability and mobility of organic matter. To investigate the selective adsorption of organic matter by coexisting inorganic colloids, humic acid (JGHA) extracted from soil, a kaolinite and goethite synthetic association (KGA) and a kaolinite and goethite mixture (KGM) were prepared and studied. With the adsorption expressed in μmol m−2, the adsorption affinity of JGHA on KGA (initial slope of isotherms) was slightly higher than that on KGM, although KGM could adsorb more JGHA molecules at larger JGHA concentrations. At pH 4, JGHA was adsorbed on the kaolinite edges and goethite through electrostatic attraction and ligand exchange, and on the kaolinite siloxane plates through hydrophobic interaction. At pH 6 and 8, the adsorption occurred only on the kaolinite siloxane plates and goethite. The overall average adsorption Gibbs energies were moderately negative, and comprised a strongly negative average overall molar entropy and a negative average overall molar entropy contribution. Thus, overall JGHA adsorption on KGA and KGM was enthalpy controlled. The large exothermic enthalpy gains and entropy losses were a result of electrostatic attraction and ligand exchange. The entropy gains because of hydrophobic attraction between JGHA and the kaolinite siloxane plates are masked by the larger entropy loss of adsorption on the hydrophilic surfaces. The fractions of JGHA with molar mass >~12.9 kDa (1 Da = 1 g mol−1) were adsorbed selectively by KGM, whereas the fractions <~12.9 kDa were selectively adsorbed by KGA. High molar mass and hydrophobic fractions adsorb selectively on the kaolinite siloxane plates, whereas low molar mass fractions with hydrophilic groups adsorb selectively on goethite and the kaolinite edges.Highlights Selective adsorption behaviour of HA on binary systems containing kaolinite and goethite. High molar mass and hydrophobic HA fractions selectively adsorb on kaolinite siloxane plates. Low molar mass and hydrophilic HA fractions selectively adsorb on kaolinite edges and goethite. Binding affinity of HA to KGA is stronger than to KGM; mineral associations are more beneficial for fixing OM in soil.

Isolation of phenolic acid in Acalypha indica l plants and test total phenol also antioxidant test using DPPH method

Acalypha indica L (Anting-anting plant) is a traditional medicinal plant that can be used as a medicine for asthma, wounds, scabies, bronchitis, diuretics, and expectorants. Acalypha indica L contains secondary metabolites including alkaloid, tannin, saponin, glycoside, steroid, phenolic, terpenoid and flavonoid. The aim of this study was to isolate of phenolic acid and test total phenol also antioxidant test with the DPPH method. The sample used was ethanol crude extract from Acalypha indica obtained by maceration method with 96% ethanol. Isolation of phenolic acid from ethanol extract was carried out by the method of acid hydrolysis (HA), alkaline hydrolysis (HB) and without hydrolysis (TH) and the separation of phenolic acid isolate was undertaken using chromatography. The total phenolic yield in Acalypha indica plants was 203,065 GAE/g. The isolation results obtained in the fractions of HA, HB and TH were 0.72 g (0.036%), 1.45 g (0,073%), 0.41 g (0.020%), respectively. The results of the TLC scanner analysis on the HA, HB and TH fractions with Rf 0.63 were thought to contain caffeic acid with 21.69%, 7.14% and 2.67% respectively. The yields of the caffeic acid content using TLC Scanner on the HA, HB and TH fractions with Rf of 0.63 were 21.69%, 7.14%, 2.67%, respectively. Antioxidant activity test on the HA, HB and TH fractions showed that IC50 values were of 127.87 ppm, 132.97 ppm, 133.68 ppm respectively.

Implication of different humic acid fractions in soils under karst rocky desertification

Karst rocky desertification, a kind of intense soil degradation, has become an urgent environmental issue in the karst region of southwest China. It was found that limestone soil, a typical soil of the karst region, is more vulnerable to karst rocky desertification than adjacent other soils although limestone soil has relatively high TOC (total organic carbon) content, but underlying mechanisms remain unclear. To investigate roles of soil properties in karst rocky desertification, three major soils, limestone soil, yellow soil and yellow brown soil, of the karst region of southwest China were sampled and their total extractable humic acid (THA) were fractionated into three sub-fractions, namely, free HA (HAf), encapsulated HA (HAe) and interacted HA (HAi), with a sequential extraction method. These soils and fractionated HA samples were systematically characterized with various analysis methods and discussed. The results showed that limestone soil had higher contents of total organic content (TOC) and THA content, but its THAC/TOC (carbon in THA to TOC) ratio (23.39%) was lower than those of yellow soil (31.44%) and yellow-brown soil (30.74%); C/N ratios and total acid contents of HAe and HAi fractions, which were physically protected by soil minerals/aggregates, were much higher than those of HAf fractions, indicating that HAe and HAi could be more active and degraded easier than HAf once exposed to microbes or/and runoff erosions. Therefore, lower HAf content and significantly lower HAfC/TOC (carbon in HAf to TOC) ratio of limestone soil may underlie the observation that limestone soil showed weak resistance to karst rocky desertification compared to other adjacent soils when the site had been artificial disturbed. We believe that roles of different HA fractions to overall quality and stability of soil deserve more attention.

Isolation of Phenolic Acid Compounds and Antioxidant Tests from Mindi Leaves (Melia azedarach L.)

Melia azedarach L plant categorized as traditional medicinal plant is normally used as a medicine for cough, skin diseases, drug for malaria, diabetes, colon cancer, jaundice, vaginal discharge, fever and scabies. Melia azedarach leaves contain steroid, terpenoid, alkaloid, tannin, saponin, phenolic and flavonoid compounds. The purpose of this study was isolation of phenolic acid compounds and antioxidant activity test from Melia azedarach L. Leaves. The method used to isolate phenolic acid using 3 ways that were alkaline hydrolysis (HB), acid hydrolysis (HA), and without hydrolysis (TH). The separation of phenolic acid which has Rf not the same as standard phenolic acid was undertaken by preparative TLC and characterized using UV-Vis spectrophotometer, FT-IR, and LC-MS. Moreover, antioxidant test of phenolic acid using DPPH method was also conducted. The results showed that isolation of Melia azedarach L. Leaves resulted in HB, HA and TH fractions with the weight of 1.05 grams, 1.26 grams and 1.38 grams, respectively. The identification of phenolic acid which has Rf the same as standard phenolic acids was ferulic acid. While result of phenolic acid (FA) isolates which has Rf not the same as phenolic acids standard was caffeic acid after the identifying using UV-Vis spectrophotometer, FTIR and LC-MS. Qualitative antioxidant activity test showed that FA isolate had IC50 of 168,650 ppm. This result indicated that FA isolate is potential as antioxidant compound.

Association between cationic liposomes and low molecular weight hyaluronic acid.

This work presents a study of the association between low molecular weight hyaluronic acid (16 kDa HA) and cationic liposomes composed of egg phosphatidylcholine (EPC), 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). The cationic liposome/HA complexes were evaluated to determine their mesoscopic structure, average size, zeta potential, and morphology as a function of the amount of HA in the system. Small angle X-ray scattering results revealed that neighboring cationic liposomes either stick together after a partial coating of low concentration HA or disperse completely in excess of HA, but they never assemble as multilamellar vesicles. Cryo-transmission electron microscopy images confirm the existence of unilamellar vesicles and large aggregates of unilamellar vesicles for HA fractions up to 80% (w/w). High concentrations of HA (> 20% w/w) proved to be efficient for coating extruded liposomes, leading to particle complexes with sizes in the nanoscale range and a negative zeta potential.

H-binding of size- and polarity-fractionated soil and lignite humic acids after removal of metal and ash components

A fractionation technique, combining dialysis removal of metal and ash components with hydrofluoric acid and pH 10 citrate buffer followed by chromatography of dialysis permeate on XAD-8 resin at decreasing pH values, has been applied to lignite humic acid (lignite-HA) and soil humic acid (soil-HA). H-binding data and non ideal competitive adsorption-Donnan model parameters were obtained for the HA fractions by theoretical analysis of H-binding data which reveal a significant increase of the carboxyl and the phenolic charge for the lignite-HA fractions vs. the parental lignite humic acid (LParentalHA). The fractionated lignite-HA material consisted mainly of permeate fractions, some of which were fulvic acid-like. The fractionated soil-HA material consisted mainly of large macromolecular structures that did not permeate the dialysis membrane during deashing. Chargeable groups had comparable concentrations in soil-HA fractions and parental soil humic acid (SParentalHA), indicating minimal interference of ash components with carboxyl and phenolic (and/or enolic) groups. Fractionation of HA, combined with theoretical analysis of H-binding, can distinguish the supramolecular vs. macromolecular nature of fractions within the same parental HA.

Changes in the content and composition of humus in the sandy loamy soddy-podzolic soil in a long-term liming experiment

The effect of liming on organic matter in sandy loamy soddy-podzolic soil was studied. The study was performed on samples taken from the 50-year-long experiment established by Prof. Kornilov in 1957. It was shown that liming had almost no effect on the total humus content in the soil. The humus composition was studied using two fractionation methods of the humus substances by the Ponomareva-Plotnikova procedure. The regrouping of the humus fractions occurred due to the changes in the mobility of soil mineral components, which involved a regular increase in the content of the Ca-bound fraction of humic acids (HA-2) at the expense of the HA-1 fraction bound to the mobile forms of R2O3 reliable at the lime rates equivalent to the total acidity and higher. The levels of the stabilization of the different HA fractions were considered, as well as the stability of the changes in the humus composition during 50 years.

Identification of Pt and Pd bound to humic acid species in spiked soils and street dusts by size exclusion chromatography and ICP-MS

The formation of PGE-humic acid (HA) complexes in soil and street dust samples was investigated. In order to assess the distribution of Pt and Pd among molecular weight fractions of humic substances, the HA extracts (extracted by 0.1 mol L−1 sodium pyrophosphate) were analysed by size exclusion chromato-graphy coupled on-line with UV-Vis detection. Similar chromatograms were obtained for soils and street dust samples (254 nm, 280 nm) and two size fractions were operationally defined as high (1600–5000 Da) and low molecular (< 1600 Da) HA fractions. The concentration of Pt and Pd in the separated extracts was determined by ICP-MS. The results indicate that up to 43% of Pt is in the high molecular and up to 52% in the low molecular HA fraction. In both type of soil samples, Pd is preferentially bound to the low molecular HA fraction. Dependence of Pd–HA and Pt–HA formation on the sample type both in the soils and in the street dust sample as well as on Pt oxidation state was established. Metallic Pt shows a tendency for complexation with the fractions of HA higher than 5000 Da. In the street dust samples, the distribution of Pt and Pd is similar and is strongly dependent on the sample type, being bound mainly to the fractions: higher than 5000 Da, 1600–5000 Da and the fraction lower than 1600 Da.

Crystal Structure of Bacteriophage T4 5′ Nuclease in Complex with a Branched DNA Reveals How Flap Endonuclease-1 Family Nucleases Bind Their Substrates

Bacteriophage T4 RNase H, a flap endonuclease-1 family nuclease, removes RNA primers from lagging strand fragments. It has both 5' nuclease and flap endonuclease activities. Our previous structure of native T4 RNase H (PDB code 1TFR) revealed an active site composed of highly conserved Asp residues and two bound hydrated magnesium ions. Here, we report the crystal structure of T4 RNase H in complex with a fork DNA substrate bound in its active site. This is the first structure of a flap endonuclease-1 family protein with its complete branched substrate. The fork duplex interacts with an extended loop of the helix-hairpin-helix motif class 2. The 5' arm crosses over the active site, extending below the bridge (helical arch) region. Cleavage assays of this DNA substrate identify a primary cut site 7-bases in from the 5' arm. The scissile phosphate, the first bond in the duplex DNA adjacent to the 5' arm, lies above a magnesium binding site. The less ordered 3' arm reaches toward the C and N termini of the enzyme, which are binding sites for T4 32 protein and T4 45 clamp, respectively. In the crystal structure, the scissile bond is located within the double-stranded DNA, between the first two duplex nucleotides next to the 5' arm, and lies above a magnesium binding site. This complex provides important insight into substrate recognition and specificity of the flap endonuclease-1 enzymes.

Application of microwave energy to speed up the alkaline extraction of humic and fulvic acids from marine sediments

The feasibility of microwave energy to speed up the alkaline extraction of humic substances (humic acid, HA, and fulvic acid, FA) from marine sediments has been checked. Extractions were performed by using 20 mL of sodium hydroxide at 0.1 M (two repeated extractions) after an ultrasound-assisted acid pre-treatment of samples to remove the carbonate fraction (ultrasound power at 17 kHz, 10 mL of 6.0 M hydrochloric acid for 15 min). After separation of HA and FA fractions by acidifying with 6 M HCl, the FA fraction (supernatant) was purified by passing the solution through a column of Amberlite XAD-8. Both HA and FA extracts were measured by UV–visible spectrophotometry. All variables affecting the extraction process (sodium hydroxide concentration and volume, ramp and hold times, temperature and number of repeated extractions) have been screened by using a Plackett–Burman design (PBD) as multivariate approach. The variables temperature and number of repeated extractions were the most significant factors ( P = 95%) affecting the extraction of both FA and HA from marine sediments. These two variables have led optimum values of 150 °C and two repeated extractions. The developed method has been found precise (R.S.D.s of 9% for HA and 12% for FA, for 11 determinations) and its results were comparable in terms of elemental (C, H and N) composition to those obtained after applying methods based on mechanical stirring and ultrasounds assisting. However, higher HA and FA concentrations than those obtained after conventional stirring and ultrasound irradiation were obtained when applying microwave energy. This means a higher efficiency of microwave energy than ultrasounds or mechanical stirring to extract HA and FA fractions from marine sediments. The method was finally applied to different surface marine sediments from the Ría de Arousa estuary.

Cocomposting of Sludge from Olive Oil Mill Wastewater Mixed with Tree Cuttings

The sludge residue from olive oil mill wastewater (OMW) evaporated in natural conditions in an open-air lagoon was cocomposted with tree cuttings (TC) in two mixtures, 48% of OMW sludge + 52% of TC (M1, C/N ratio, 30), and 58% of OMW sludge + 42% of TC (M2, C/N ratio, 26). The evolution and modification of properties occurring in the OMW sludge-TC mixtures at different stages of the composting process were evaluated by chemical analyses, including pH, electrical conductivity and contents of total organic C, total N, total extractable C and humified C fractions. Further, HAs were isolated from the mixtures by a conventional procedure based on alkaline extraction, acidic precipitation to pH 1, purification by repeated alkaline dissolutions and acidic precipitations, water washing, dialysis, and final freeze-drying. The HAs obtained were analyzed for elemental (C, H, N, S, O) and acidic functional group (carboxylic and phenolic) composition, and by ultraviolet/visible, Fourier transform infrared, fluorescence and electron spin resonance spectroscopies. Composting of the OMW sludge-TC mixtures resulted in an increase of pH and total N, ash and humified C contents, whereas electrical conductivity and total organic C, total extractable C and NH4 +−N contents and C/N ratio tended to diminish. At the initial stage of composting, HAs from the OMW sludge-TC mixtures were characterized by a marked aliphatic character, small O and acidic functional group contents, marked presence of proteinaceous materials and partially modified lignin moieties and polysaccharides-like structures, extended molecular heterogeneity, low organic free radical contents and small degrees of aromatic ring polycondensation, polymerization and humification. With increasing the composting time, a loss of aliphatic materials and carbohydrates, and an increase of oxygenation, acidic functional groups, S- and N-containing groups and aromaticity occurred in HA fractions. Chemical and physicochemical analyses of the two OMW sludge-TC mixtures and their HA components at the end of composting indicated that an adequate degree of maturity and stability was achieved by both end products, and especially for the one obtained from mixture M2.

Interactions of Cu (II) and Fe (III) with mangal humic substances studied by synchronous fluorescence spectroscopy and potentiometric titration

Humic (HA) and fulvic (FA) acids isolated from mangrove sediments of Sundarban, the largest delta on earth in the estuarine phase of the river Ganges, were studied and attempts were made to characterize their binding sites by quenching of Synchronous fluorescence (SyF) bands with Fe (III) and Cu (II). A modified Stern-Volmer relationship applicable for static quenching was applied for the determination of conditional stability constants and the data were compared with those determined by potentiometric titration. In the excited state HA and FA showed different acidity constant compared to the ground state. Values of the conditional stability constant (log Kc) for Fe (III) and Cu (II) indicated that binding sites were bidentate in nature. FA were better chelators than the HA fractions. High energy binding sites of both FA & HA were occupied by Fe(III) and the low energy binding sites, mainly responsible for mobilization and immobilization of metal, were occupied by Cu(II).

Labile soil organic matter as a potential nitrogen source in golf greens

The loss of fertilizer N from golf greens can be high depending upon management (irrigation schedule, N source, rate and timing of fertilizer application) as well as soil conditions. Although soil organic matter (SOM) is acknowledged as a major source of N and other nutrients, its potential as an N source seems to be neglected in the management of golf greens. The susceptibility of SOM to degradation is one indication of how active a role SOM plays as a nutrient source. An extraction method developed by Olk et al. [Geoderma 65 (1995) 195] distinguishes humic acid fractions by their binding to dominant stabilizing soil cations and separates them into calcium-bound (CaHA) and non calcium-bound or mobile (MHA) fractions. Mobile humic acid is a relatively young, N-rich HA fraction that does not appear to form stable complexes with Ca. The MHA could therefore play a greater role in nutrient availability than CaHA. We determined C and N distributions within SOM extracted from these two HA fractions in 11 golf greens ranging in age from 4 to 28 yr. Because SOM in golf greens is recently formed, and MHA is an N-rich fraction representing an early stage of SOM evolution, we hypothesized that the MHA fraction would account for a larger proportion of soil organic N than CaHA. The amounts of both HA-C and HA-N increased significantly with green age. MHA accounted for a larger proportion (20–27%) of total soil C than CaHA-C (8–14%). MHA was also enriched in N compared to CaHA with consistently smaller C-to-N ratios. Thus, the greater abundance of MHA and its higher N concentration accounted for a larger proportion of soil organic N (24–45%). The equivalence of MHA-N ranged between 250 kg N ha −1 for a 4 yr-old green and 775 kg N ha −1 for a 21 yr-old green. Thus, soils of established greens contain significant quantities of labile SOM rich in N that could through mineralization supply part of the fertilizer N requirement of turf grass. A greater understanding of the dynamics of this resource is needed if we are to manage golf greens for optimal use without negative consequences to the environment.