Humic Acid-like Compounds Research Articles

Redistribution of Cs 137 introduced into montmorillonite in association with organic matter coming from biomass composting

The adsorption and later bioavailability of 137Cs from the system humic acid (HA)/humic acid like compounds (HALC) and montmorillonite was investigated. The setup of the experiments should approach as much as possible natural conditions when 137Cs is introduced into soil with HALC from decomposed biomass. The significant differences were found in the trials containing various HA/HALC and also pure montmorillonite. The 137Cs was more available when it reached soil in association with HALC originated from compost than when it was adsorbed on stable humic acids. Moreover, the long term interaction of 137Cs with HALC led to decrease of 137Cs adsorbed on montmorillonite and increase of its bioavailable fraction. UV–Vis spectrometry and infrared spectroscopy showed the clear difference between HA, fresh HALC and old HALC which could partially explain the different results.

Structure and biodegradability of dissolved organic matter from Ultisol treated with long-term fertilizations

Dissolved organic matter (DOM) is a labile and reactive fraction of soil organic matter. Ultisol usually has low content of organic matter. Fertilization is a normal way in regulating the state of soil organic matter. This study aimed to investigate the effects of different fertilizations on the content, distribution, structure, and biodegradability of DOM from Ultisol. Ultisol treated by no fertilizer (Ck), chemical fertilizer (NPK), the mixture of chemical fertilizer and straw (NPKS), and animal manure (AM) were collected from a long-term fertilization experimental site. Soil DOM was extracted by deionized water with solid to water ratio of 1:5. The concentration of dissolved organic carbon and total soluble nitrogen in DOM was determined by TOC analyzer. The structure of DOM was investigated by fluorescence spectroscopy through the emission spectra, excitation spectra, synchronous-scan spectra, and excitation-emission matrix. Soil DOM was incubated for 21 days after the addition of soil microbial inoculum and nutrient solution, the biodegradability of DOM was estimated by calculating the percentage of dissolved organic carbon lost after 21 days of incubation. The content of dissolved organic carbon in the soil of Ck, NPK, NPKS, and AM was 22.14, 27.05, 36.08, and 56.04 mg/kg, respectively. The distribution of dissolved organic carbon on large macroaggregate increased from 47.0% in Ck to 65.0–71.5% in fertilized treatments but that on small macroaggregate decreased from 35.5% in Ck to 18.3–19.9% in fertilized treatments. Similar peak wavelength and a fluorophore at wavelength pair of 330–340ex/406–422em were found in all examined DOM. However, a sequence of AM > NPKS > NPK > Ck was found in the fluorescence intensity of examined DOM, indicating the simplification of DOM structure induced by fertilization. The biodegradability of DOM from the Ck, NPK, NPKS, and AM treatment after 21 days of incubation was 23.9, 28.7, 34.2, and 42.7%, respectively. Organic and inorganic fertilization increased the content of DOM from Ultisol. Compared to the Ck treatment, the fertilization treatments increased the distribution of dissolved organic carbon on large macroaggregate but reduced its distribution on small macroaggregate. Humic acid-like compounds were the dominant fractions in DOM from all treatments. DOM from Ck and NPK treatments had more complex molecular structure and lower biodegradability than that from NPKS and AM treatments.

Release of 137Cs from plant mass in course of biodegradation

This investigation was focused on the role of humic acid-like compounds during the biodegradation of plant mass contaminated with 137Cs. The experiments were set up to distinguish cases of external and internal contamination. The results showed that 137Cs was associated with humic acid-like compounds in eluates from biomass and especially with their lighter fraction. The 137Cs in detritus was markedly mobile and only minor amounts were retained in biomass. These two variants differed in the rate of 137Cs release: while in the internally contaminated biomass the rate decreased during composting, in the externally contaminated biomass the rate increased.

Effects of NOM on the degradation of chloramphenicol by UV/H2O2 and the characteristics of degradation products

Abstract Effects of natural organic matter (NOM) on the degradation of chloramphenicol (CAP) by UV/H 2 O 2 and the characteristics of degradation products were investigated. With initial concentration of 5 mg L −1 CAP, UV and 0.5 mM H 2 O 2 process induced the degradation rate constant increased to 3.75 × 10 −3 s −1 , which was about 1.6 times of that treated with UV alone. The excitation-emission matrix (EEM) fluorescence spectra showed that the degradation products included many humic acid-like compounds (HA). Therefore, addition of 5 mg/L HA to the solution decreased the degradation rate constant to 1.78 × 10 −3 s −1 , because they would compete for the oxidizing reaction of CAP with OH. However, the degradation rate constant and removal efficiency of CAP were influenced not only by the initial concentration of HA but also by the ratio of [HA] 0 /[CAP] 0 . When the initial concentration of CAP decreased to 0.1 mg/L, the ratio of [HA] 0 /[CAP] 0 increased to 50. The degradation rate constant increased to 2.32 × 10 −3 s −1 . Moreover, the results of ultra high-performance liquid chromatography & quadrupole time-of-flight mass spectrometer (UPLC-Q-TOF-MS) suggested that the main degradation products were dichloroacetic acid ( m / z 129) and aromatics 4-nitro-benzoic acid ( m / z 167). These products were induced by the radical reaction during the UV/H 2 O 2 treatment process. Meanwhile, Fourier transform infrared spectroscopy (FTIR) indicated that UV/H 2 O 2 could destroy the aromatic ring of CAP and initiating the mineralization of CAP. TEQ 4-NQO decreased to 0.20 μg L −1 after the treatment with UV dose 2000 mJ cm −2 and 0.5 mM H 2 O 2 . Therefore, the radical reaction and mineralization of CAP also decreased the genotoxicity obviously.

Calcium and organic matter removal by carbonation process with waste incineration flue gas towards improvement of leachate biotreatment performance

Municipal solid wastes incineration (MSWI) flue gas was employed as the carbon source for in-situ calcium removal from MSWI leachate. Calcium removal efficiency was 95–97% with pH of 10.0–11.0 over 100min of flue gas aeration, with both bound Ca and free Ca being removed effectively. The fluorescence intensity of tryptophan, protein-like and humic acid-like compounds increased after carbonation process. The decrease of bound Ca with the increase of precipitate indicated that calcium was mainly converted to calcium carbonate precipitate. It suggested that the interaction between dissolved organic matter and Ca2+ was weakened. Moreover, 10–16% of chemical oxygen demand removal and the decrease of ultraviolet absorption at 254nm indicated that some organics, especially aromatic compound decreased via adsorption onto the surface of calcium carbonate. The results indicate that introduce of waste incineration flue gas could be a feasible way for calcium removal from leachate.

Peroxidation of High Algae-laden Water by Ozone: Algae Organic Matter Transformation and Disinfection By-products Formation

Formation characteristics and transferring feature of nitrogenous/carbonaceous disinfection by-products have been observed under different ozone dosages and pH conditions, and essential nature conversion of Algae organic matters has been also studied concurrently, based on high algae-laden water. The results showed as follows:reduction of Microcystis aeruginosa could reach 36% at the ozonation concentration of 28.92 mg·L-1. Humic acid-like compounds first increased and then decreased with continuing addition of ozone dosage, whereas soluble microbial products, fulvic acids and aromatic protein substance all diminished. Low dosage of ozone had certain effect on control of dichloroacetonitrile(DCAN) and trichloroacetonitrile (TCAN) formation potential, yet augmented the yield of trichloronitromethane (TCNM) and 1,1,1-trichloroacetone(1,1,1-TCP) precursors, and N-DBPs formation potential was promoted with the increase of ozone dosage. Algae removal efficiency was relatively the best under the acidic condition, meanwhile, UV254 and DOC increased with the rise of pH, though the change was not outstanding. Humic acid-like compounds decreased with the rise of pH; ozonation could degrade the soluble microbial products and the consequence was affected little by the change of pH. DCAN and TCAN formation potential decreased with the rise of pH; TCNM formation potential appeared to be the highest when the pH was 10, whereas the highest 1,1,1-TCP formation potential was found at pH 7.

Effects of ZnO nanoparticle exposure on wastewater treatment and soluble microbial products (SMPs) in an anoxic-aerobic membrane bioreactor

The effect of zinc oxide nanoparticles (ZnO NPs) on the performance of an anoxic-aerobic submerged membrane bioreactor (MBR), and the characterization of the soluble microbial products (SMPs) produced in the presence of ZnO NPs was evaluated. Continuous operation over 144 days showed that ZnO NPs at concentrations of 10 and 50 mg/L exerted a negative impact on chemical oxygen demand (COD) and nitrogen removal, although ZnO NPs were efficiently removed in the MBR (>92%). 10 and 50 mg/L ZnO NPs decreased COD removal substantially from 93.1± 0.6% to 90.1± 0.8% (<0.05) and 86.3± 2.3% (<0.05), respectively. Similarly, with 10 and 50 mg L ZnO NPs, the decreased in NH4N removal was 8.1% and 21.1%, respectively. Exposure to 1, 10 and 50 mg/L ZnO NPs increased SMP concentrations by 12.8%, 42.4% and 51.5%, respecti. High performance size exclusion chromatograph (HP-SEC) analysis revealed that the presence of ZnO NPs caused a significant increase in high-molecular weight (MW) (583 kDa) SMPs at 1 and 10 mg/L ZnO NP concentration. A substantial decrease in the concentration of high-MW compounds in the MBR effluent was observed at the end of the experiment. Excitation emission matrix (EEM) fluorescence contours revealed that SMPs were dominated by amino acid-, tryptophan protein-, polyaromatic-, and polycarboxylate-type substances. The presence of ZnO NPs enhanced the production of amino acid-like (7.5–25.1%) and tryptophan protein-like compounds (31.7–38.1%), compared to the control (6.0–20.2% for amino acid-like compounds; and 28.5–36.7% for tryptophan protein-like compounds). In contrast, the fulvic and humic acid-like compounds decreased with exposure to ZnO NPs. This work may help better understanding the effect of nanoparticle exposure on wastewater treatment performance and SMP characteristics.

Effects of returning NF concentrate on the MBR-NF process treating antibiotic production wastewater.

The optimization of the nanofiltration (NF) concentrate backflow ratio (R cb) and the influence of the NF concentrate on the performance of membrane bioreactor-nanofiltration (MBR-NF) process treating antibiotic production wastewater were investigated on a laboratory scale. The R cb was optimized at 60% based on the removal rates of chemical oxygen demand (COD) and NH4 (+)-N by MBR. Data analyses indicated that salinity brought by NF concentrate is the major driver leading to the decrease of sludge activity, especially at a high R cb. EPS analysis showed that electric conductivity (EC), proteins in soluble microbial products (SMP), and SMP brought by NF concentrate are the dominant factors causing the severe membrane fouling in MBR. Furthermore, undegradable substances including fulvic acid-like and humic acid-like compounds accumulated in NF concentrate showed significant influence on fouling of NF. MBR could well degrade small MW compounds in NF concentrate, which confirmed the enhancement of organic removal efficiency by recycling the NF concentrate to MBR. The MBR-NF process showed a relatively stable performance at the R cb of 60% (volume reduction factor (VRF) = 5), and the NF permeate could satisfy the water quality standard for fermentation process with a water recovery rate of 90.9%.

Advanced treatment of stabilized landfill leachate after biochemical process with hydrocalumite chloride (Ca/Al–Cl LDH)

This study investigated the effectiveness of Ca/Al–Cl LDH for the treatment of stabilized landfill leachate. Experiments were performed including different dosage of Ca/Al–Cl LDH and comparison with different reagents, such as CaCl2 and AlCl3. As a result, Ca/Al–Cl LDH efficiently removed organic matters in stabilized landfill leachate with the maximum removal (59.41% COD, 62.06% DOC and 70.56% UV254) at the dose of 30g/L. According to UV254 and EEM, it is remarkable that the formation of Ca/Al–LDH has a greater beneficial to organic removal than other reagents, especially for fulvic acid-like and humic acid-like compounds. Moreover, the removal of fulvic acid-like compounds was much better than humic acid-like compounds. The previous compounds had more carboxylic groups, thus had a better removal selectivity.

Effect of long-term application of corn stalks and inorganic fertilizers on fluorescence characteristics of water extractable organic matter in a meadow black soil of northeast China

ABSTRACTReturning crop residues into fields, either alone or in combination with inorganic fertilizer, is considered as a practical way to enhance soil fertility. However, information concerning the effects of crop residues and inorganic fertilizer application on water extractable organic matter (WEOM) in soil is scarce. The aim of this study was to examine the 10-year effect of corn residue (CR) return with or without the application of nitrogen, phosphorus, and potassium (NPK) fertilizer on the quantity and quality of WEOM in a black soil of northeast China by means of ultraviolet absorbance, fluorescence excitation--emission matrix, and derived spectroscopic indices. The application of NPK fertilizers and CR, alone or together, increased the content of total soil organic carbon (SOC), water extractable organic carbon (WEOC), and ratio of WEOC/SOC, with the sequence being NPK + CR > CR > NPK > CK. Compared with control treatment, the individual application of NPK fertilizer decreased the aromaticity of WEOM. In contrast, elevated proportion of tryptophan-like fluorophore and microbially derived fulvic acid-like components with low molecular weight was detected in the WEOM. The amendment with CR alone resulted in increase in aromaticity of WEOM and proportion of plant-derived humic acid-like component with large molecular weight, accompanied by reduced proportion of tyrosine-like compounds. For the soil with CR restoration, the application of NPK fertilizer increased aromaticity of WEOM, and large molecular weight fulvic acid-like and humic acid-like compounds were found. However, the proportions of tyrosine-like and tryptophan-like compounds were diminished. The quantitative and qualitative analysis of WEOM using fluorescence spectroscopy describes responses to be observed in long-term different fertilization strategies.

Towards understanding the stabilization process in vermicomposting using PARAFAC analysis of fluorescence spectra

In this study, fluorescence excitation–emission matrix (EEM) combined with parallel factor analysis (PARAFAC) was employed to trace the behavior of water extractable organic matter and assess the stabilization process during vermicomposting of sewage sludge and cattle dung. Experiments using different mixing ratios of sewage sludge and cattle dung were conducted using Eisenia fetida. The results showed that vermicomposting reduced the DOC, DOC/DON ratio and ammonia, while increased the nitrate content. A three-component model containing two humic-like materials (components 1 and 2) and a protein-like material (component 3) was successfully developed using PARAFAC analysis. Moreover, the initial waste composition had a significant effect on the distribution of each component and the addition of cattle dung improved the stability of sewage sludge in vermicomposting. The PARAFAC results also indicated that protein-like materials were degraded and humic acid-like compounds were evolved during vermicomposting. Pearson correlation analysis showed that components 2 and 3 are more suitable to assess vermicompost maturity than component 1. In all, EEM–PARAFAC can be used to track organic transformation and assess biological stability during the vermicomposting process.

Simultaneous removal of dissolved organic matter and bromide from drinking water source by anion exchange resins for controlling disinfection by-products

Anion exchange resins (AERs) with different properties were evaluated for their ability to remove dissolved organic matter (DOM) and bromide, and to reduce disinfection by-product (DBP) formation potentials of water collected from a eutrophic surface water source in Japan. DOM and bromide were simultaneously removed by all selected AERs in batch adsorption experiments. A polyacrylic magnetic ion exchange resin (MIEX®) showed faster dissolved organic carbon (DOC) removal than other AERs because it had the smallest resin bead size. Aromatic DOM fractions with molecular weight larger than 1600 Da and fluorescent organic fractions of fulvic acid- and humic acid-like compounds were efficiently removed by all AERs. Polystyrene AERs were more effective in bromide removal than polyacrylic AERs. This result implied that the properties of AERs, i.e. material and resin size, influenced not only DOM removal but also bromide removal efficiency. MIEX® showed significant chlorinated DBP removal because it had the highest DOC removal within 30 min, whereas polystyrene AERs efficiently removed brominated DBPs, especially brominated trihalomethane species. The results suggested that, depending on source water DOM and bromide concentration, selecting a suitable AER is a key factor in effective control of chlorinated and brominated DBPs in drinking water.

Diuron herbicide degradation catalyzed by low molecular weight humic acid-like compounds

Phenylureas such as diuron are major herbicides used worldwide to control undesirable weeds. The environmental fate of phenylureas is of great interest because massive amounts of those herbicides are used. It is known that abiotic degradation of phenylureas in soil–water systems is catalyzed by humic acids. However, due to the chemical heterogeneity and large molecular sizes of humic acids, the specific effects of functional groups during catalysis have not been elucidated. Therefore, we studied here for the first time the kinetics of diuron degradation in the presence of low molecular weight humic acid-like compounds such as benzoic acid derivatives. Experiments were carried out at various pH and temperature, and monitored by high-performance liquid chromatography. Results show that all benzoic acid derivatives efficiently catalyzed diuron hydrolysis. The catalytic efficiency decreased in the following order: 0.88 M−1 day−1 for 3,4-dihydroxybenzoic acid, 0.72 M−1 day−1 for 4-hydroxybenzoic acid, 0.23 M−1 day−1 for phthalic acid, 0.11 M−1 day−1 for 2-hydroxybenzoic acid, and 0.09 M−1 day−1 for 2,4-dihydroxybenzoic acid. These differences in the catalytic efficiency are explained by steric hindrance affecting the accessibility of reactive sites and hence influencing the rate of the overall process. Steric factors are therefore expected to control the catalytic activity of humic acids because of the chemical similarities between humic acids and low molecular weight humic acid-like compound. Our results should help predict more accurately the fate and abiotic degradation mechanism of phenylureas in the environment.

Chemical and spectroscopic characterization of water extractable organic matter during vermicomposting of cattle dung

This work illustrated the characteristics and transformation of water extractable organic matter (WEOM) during vermistabilization (Eisenia fetida) of cattle dung by means of chemical and spectroscopic methods. The independent experiment conducted in triplicate was sampled at the 0, 7, 14, 21, 35, 60 and 90days. Results showed that the DOC kept steady around 2.7gkg−1 after day 60 and the DOC/DON ratio decreased from 19.77 to 5.26 till the end of vermicomposting. On the other hand, vermicomposting decreased the aliphatic, proteinaceous, carbohydrates components and increased the aromaticity and oxygen-containing functional groups in the WEOM. Moreover, fluorescence spectra and fluorescence regional integration (FRI) results indicated that protein-like groups were degraded and fulvic and humic acid-like compounds were evolved during the vermicomposting process. In all, this study suggested the suitability of WEOM for monitoring the organics transformation and assessing the maturity in the vermicomposting.

Changes in the chemical characteristics of water-extracted organic matter from vermicomposting of sewage sludge and cow dung

The chemical changes of water-extractable organic matter (WEOM) from five different substrates of sewage sludge enriched with different proportions of cow dung after vermicomposting with Eisenia fetida were investigated using various analytical approaches. Results showed that dissolved organic carbon, chemical oxygen demand, and C/N ratio of the substrates decreased significantly after vermicomposting process. The aromaticity of WEOM from the substrates enhanced considerably, and the amount of volatile fatty acids declined markedly, especially for the cow dung substrate. Gel filtration chromatography analysis showed that the molecular weight fraction between 103 and 106Da became the main part of WEOM in the final product. 1H nuclear magnetic resonance spectra revealed that the proportion of H moieties in the area of 0.00–3.00ppm decreased, while increasing at 3.00–4.25ppm after vermicomposting. Fluorescence spectra indicated that vermicomposting caused the degradation of protein-like groups, and the formation of fulvic and humic acid-like compounds in the WEOM of the substrates. Overall results indicate clearly that vermicomposting promoted the degradation and transformation of liable WEOM into biological stable substances in sewage sludge and cow dung alone, as well as in mixtures of both materials, and testing the WEOM might be an effective way to evaluate the biological maturity and chemical stability of vermicompost.

Availability of microbial and soil organic nitrogen to a Pseudomonas strain and the effect of soil organic matter on the availability of casein nitrogen

A microbiological method has been devised to determine the availability of microbial and soil organic N to a proteolytic Pseudomonas strain. The growth of the Pseudomonas sp. on soil fractions or on microbial material as the sole N source was compared with the growth on casein-N. The nitrogenous constituents of 3-day-old Arthrobacter cells were found to be more resistent to degradation than those of 6-day-old cells during an incubation period of 4 days. The percentage of available soil organic N and available humic acid N increased with the pH of the medium in which the availability was determined. The percentage of available organic N in grassland soil was twice that in arable soil. The proportion of N utilized by the proteolytic Pseudomonas sp. from humic acids extracted from the soil with sodium pyrophosphate (pH 7) was four times higher than that utilized from the total soil organic matter. When NaOH had been the extractant of the humic acid fraction, the relative availability of the N of the humic acid fraction was twice as high as that of the entire soil organic matter. The availability of N of humic acid-like compounds, synthesized by a Streptomyces strain, to the Pseudomonas sp. was similar to that of humic acids extracted from grassland soil by NaOH, viz. 11–25 per cent (depending upon the pH of the culture solution) of the total N contained in the humic acid fraction. The availability of casein-N decreased in the presence of soil or soil humic acids. This reduction of casein assimilation was partly offset by the addition of CaCO 3 to the test medium; it appeared to be a pH effect. The results obtained suggest that more protein-like compounds are incorporated in the soil organic matter of grassland than in that of arable land.