Types Of Natural Organic Matter Research Articles

Sorption selectivity in natural organic matter probed with fully deuterium-exchanged and carbonyl-13C-labeled benzophenone and 1H-13C NMR spectroscopy.

Specific functional-group or domain interactions of fully deuterium-exchanged, carbonyl-(13)C-labeled benzophenone and different types of natural organic matter (NOM) were investigated through two-dimensional (1)H-(13)C heteronuclear correlation NMR spectroscopy. The sorbents included Beulah-Zap lignite, type II kerogen (IL-6), Pahokee peat, Amherst humic acid, and a polystyrene-poly(vinylmethyl ether) (PS-PVME) blend. PS-PVME consists of PS and PVME chains that are mixed on a scale of <5 nm. The NOM sorbents all consist predominantly of a mixed aromatic-alkyl or aromatic-O-alkyl matrix that is homogeneous on the 3 nm scale, as evidenced by fast equilibration of aromatic and alkyl (1)H magnetization. In addition, Beulah lignite and IL-6 kerogen exhibit small fractions of distinct polymethylene (CH2)n domains, and Pahokee peat contains significant fractions of polar and nonpolar alkyl domains. Benzophenone-((13)C═O)-d10 shows proximity to both aromatic rings and alkyl segments in all samples but preferentially interacts with aromatic rings in PS-PVME and Beulah lignite, possibly due to π-π electron donor-acceptor interactions. The data for IL-6 kerogen are also compatible with preferential location of benzophenone near the alkyl-substituted edges of aromatic rings, while in Pahokee peat, clear signatures of benzophenone affinity to both aromatic-rich and nonpolar alkyl domains have been detected. Amherst humic acid shows evidence of some affinity to polar alkyl segments but which is weaker than that to aromatic rings. Our results indicate that specific interactions of the sorbate and the presence of domains in the sorbent influence the magnitude and selectivity of sorption.

Fact or artifact: the representativeness of ESI-MS for complex natural organic mixtures

Because mass spectrometers provide their own dispersion and resolution of analytes, electrospray ionization mass spectrometry (ESI-MS) has become a workhorse for the characterization of complex mixtures from aerosols to crude oil. Unfortunately, ESI mass spectra commonly contain multimers, adducts and fragments. For the characterization of complex mixtures of unknown initial composition, this presents a significant concern. Mixed-multimer formation could potentially lead to results that bare no resemblance to the original mixture. Conversely, ESI-MS has continually reflected subtle differences between natural organic matter mixtures that are in agreement with prediction or theory. Knowing the real limitations of the technique is therefore critical to avoiding both over-interpretation and unwarranted skepticism. Here, data were collected on four mass spectrometers under a battery of conditions. Results indicate that formation of unrepresentative ions cannot entirely be ruled out, but non-covalent multimers do not appear to make a major contribution to typical natural organic matter spectra based on collision-induced dissociation results. Multimers also appear notably reduced when a cooling gas is present in the accumulation region of the mass spectrometer. For less complex mixtures, the choice of spray solvent can make a difference, but generally spectrum cleanliness (i.e. representativeness) comes at the price of increased selectivity.

Hydrophilic fraction of natural organic matter causing irreversible fouling of microfiltration and ultrafiltration membranes

Although membrane filtration is a promising technology in the field of drinking water treatment, persistent membrane fouling remains a major disadvantage. For more efficient operation, causative agents of membrane fouling need to be identified. Membrane fouling can be classified into physically reversible and irreversible fouling on basis of the removability of the foulants by physical cleaning. Four types of natural organic matter (NOM) in river water used as a source of drinking water were fractionated into hydrophobic and hydrophilic fractions, and their potential to develop irreversible membrane fouling was evaluated by a bench-scale filtration experiment together with spectroscopic and chromatographic analyses. In this study, only dissolved NOM was investigated without consideration of interactions of NOM fractions with particulate matter. Results demonstrated that despite identical total organic carbon (TOC), fouling development trends were significantly different between hydrophilic and hydrophobic fractions. The hydrophobic fractions did not increase membrane resistance, while the hydrophilic fractions caused severe loss of membrane permeability. These results were identical with the case when the calcium was added to hydrophobic and hydrophilic fractions. The largest difference in NOM characteristics between hydrophobic and hydrophilic fractions was the presence or absence of macromolecules; the primary constituent causing irreversible fouling was inferred to be “biopolymers”, including carbohydrates and proteins. In addition, the results demonstrated that the extent of irreversible fouling was considerably different depending on the combination of membrane materials and NOM characteristics. Despite identical nominal pore size (0.1 μm), a polyvinylidene fluoride (PVDF) membrane was found to be more rapidly fouled than a PE membrane. This is probably explained by the generation of strong hydrogen bonding between hydroxyl groups of biopolymers and fluorine of the PVDF membrane. On the basis of these findings, it was suggested that the higher fouling potential of the hydrophilic fraction of the dissolved NOMs from various natural water sources are mainly attributed to macromolecules, or biopolymers.

Characterization of the Natural Organic Matter (NOM) in groundwater contaminated with 60Co and 137Cs using ultrafiltration, Solid Phase Extraction and fluorescence analysis

Spot samples of shallow groundwaters have been taken between the years 2004 and 2010 near a site formerly used for the dispersal of radioactive liquid wastes. Three sampling points, one clean (upstream), and two downstream of the contamination source, were processed by ultrafiltration (5000 Da cut-off) and Solid Phase Extraction (SPE) to determine the association of selected artificial radionuclides (60Co, 137Cs) with Natural Organic Matter (NOM). The last two sampling episodes (2008 and 2010) also benefited from fluorescence analysis to determine the major character of the NOM. The fluorescence signals are reported as humic-like, fulvic-like and protein-like, which are used to characterize the different NOM types. The NOM from the clean site comprised mostly fine material, whereas the colloidal content (retained by ultrafiltration) was higher (e.g., 15–40% of the Total Organic Carbon – TOC). Most of the 137Cs was present in the colloidal fraction, whereas 60Co was found in the filtered fraction. Fluorescence analysis, on the other hand, indicated a contrasting behavior between the clean and contaminated sites, with a dominance of protein-like material, a feature usually associated with human impacts. Finally, SPE removed almost quantitatively the protein-like material (>90%), whereas it removed a much smaller fraction of the 137Cs (<28%). This finding indicates that the 137Cs preferential binding occurs with a fraction other than the protein-like NOM, likely the fulvic-like or humic-like portion.

Influence of different types of natural organic matter on titania nanoparticle stability: effects of counter ion concentration and pH

Effects of pH, three natural macromolecules and three mono- and divalent electrolytes on the stability of titania nanoparticles.

Examining the interrelationship between DOC, bromide and chlorine dose on DBP formation in drinking water — A case study

During drinking water treatment aqueous chlorine and bromine compete to react with natural organic matter (NOM). Among the products of these reactions are potentially harmful halogenated disinfection by-products, notably four trihalomethanes (THM4) and nine haloacetic acids (HAAs). Previous research has concentrated on the role of bromide in chlorination reactions under conditions of a given NOM type and/or concentration. In this study different concentrations of dissolved organic carbon (DOC) from U.K. lowland water were reacted with varying amounts of bromide and chlorine in order to examine the interrelationship between the three reactants in the formation of THM4, dihaloacetic acids (DHAAs) and trihaloacetic acids (THAAs). Results showed that, in general, molar yields of THM4 increased with DOC, bromide and chlorine concentrations, although yields did fluctuate versus chlorine dose. In contrast both DHAA and THAA yields were mainly independent of changes in bromide and chlorine dose at low DOC (1mg·L−1), but increased with chlorine dose at higher DOC concentrations (4mg·L−1). Bromine substitution factors reached maxima of 0.80, 0.67 and 0.65 for the THM4, DHAAs and THAAs, respectively, at the highest bromide/chlorine ratio studied. These results suggest that THM4 formation kinetics depend on both oxidation and halogenation steps, whereas for DHAAs and THAAs oxidation steps are more important. Furthermore, they indicate that high bromide waters may prove more problematic for water utilities with respect to THM4 formation than for THAAs or DHAAs. While mass concentrations of all three groups increased in response to increased bromide incorporation, only the THMs also showed an increase in molar yield. Overall, the formation behaviour of DHAA and THAA was more similar than that of THM4 and THAA.

Influence of two types of organic matter on interaction of CeO2 nanoparticles with plants in hydroponic culture

An important aspect in risk assessment of nanoparticles (NPs) is to understand their environmental interactions. We used hydroponic plant cultures to study nanoparticle–plant-root interaction and translocation and exposed wheat and pumpkin to suspensions of uncoated CeO2–NP for 8d (primary particle size 17–100nm, 100mgL−1) in the absence and presence of fulvic acid (FA) and gum arabic (GA) as representatives of different types of natural organic matter. The behavior of CeO2–NPs in the hydroponic solution was monitored regarding agglomeration, sedimentation, particle size distribution, surface charge, amounts of root association, and translocation into shoots. NP-dispersions were stable over 8d in the presence of FA or GA, but with growing plants, changes in pH, particle agglomeration rate, and hydrodynamic diameter were observed. None of the plants exhibited reduced growth or any toxic response during the experiment. We found that CeO2–NPs translocated into pumpkin shoots, whereas this did not occur in wheat plants. The presence of FA and GA affected the amount of CeO2 associated with roots (pure>FA>GA) but did not affect the translocation factor. Additionally, we could confirm via TEM and SEM that CeO2–NPs adhered strongly to root surfaces of both plant species.

Natural organic matter: effect on contaminant destruction by UV/H2O2

Ultraviolet (UV) light with hydrogen peroxide degrades a wide array of organic micropollutants. However, natural organic matter (NOM) interferes with contaminant destruction. Seven emerging contaminants were evaluated by UV pilot‐scale and collimated beam experiments. UV absorbance scans demonstrated changes in NOM due to radical attack. Waters with different types and amounts of NOM were examined. As NOM increased, electrical energy per order (EE/O) requirements for destruction increased. EE/O increased similarly for the contaminants. Methyl‐tert‐butyl‐ether destruction and EE/O values correlated well with specific UV absorption for all experiments. Both type and amount of NOM should be considered in the design of UV/hydrogen peroxide facilities.

Effect of natural organic matter (NOM) on Cu(II) adsorption by multi-walled carbon nanotubes: Relationship with NOM properties

The effect of natural organic matter (NOM) on Cu(II) adsorption by multi-walled carbon nanotubes (MWCNTs) was investigated. Particular attention was paid to the relationship between NOM properties and NOM adsorption and their effects on the Cu(II) adsorption by MWCNTs. The results showed that the NOM adsorption data were well fit to the Freundlich isotherm model, and the MWCNTs that had higher oxygen content had lower KF (Freundlich constants) values. The KF values for the different types of NOM varied greatly and were proportional to the aromatic carbon content, the specific ultraviolet absorbance at 275nm, and the TOC-normalized fluorescence intensity of the F3 peak at ∼460nm. In contrast, they had negative linear correlations with the absorbance ratios at 250nm and 365nm and the TOC-normalized fluorescence intensity of the F1 peak from 250nm to 300nm. The results indicated that π–π and hydrophobic interactions were the predominant NOM adsorption mechanisms by the MWCNTs. The Cu(II) adsorption by the MWCNTs increased with increasing NOM concentrations due to the complexing of Cu(II) with the adsorbed NOM. This was confirmed by XPS and FTIR spectra. The increased degree of Cu(II) adsorption was positively correlated with the carboxyl carbon content, carboxyl group content, and the polarity index of the NOM. The findings in this study highlight that the NOM characteristics are responsible for controlling the NOM adsorption and its effects on heavy metal sorption by MWCNTs.

Comparing the Influence of Two Different Natural Organic Matter Types on Colloid Deposition in Saturated Porous Medium

Humic acid and protein are two major organic matter types encountered in natural and polluted environment, respectively. This study employed Triple Pulse Experiments (TPEs) to investigate and compare the influence of Suwannee River Humic Acid (SRHA) (model humic acid) and Bovine Serum Albumin (BSA) (model protein) on colloid deposition in a column packed with saturated iron oxide-coated quartz sand. Study results suggest that adsorbed SRHA may inhibit colloid deposition by occupying colloid sites on the porous medium. Conversely, BSA may promote colloid deposition by a ‘filter ripening’ mechanism. This study provides insight to understand the complex behavior of colloids in organic matter-presented aquifers and sand filters.

Comparing the Influence of Two Different Natural Organic Matter Types on Colloid Deposition in Saturated Porous Medium

Humic acid and protein are two major organic matter types encountered in natural and polluted environment, respectively. This study employed Triple Pulse Experiments (TPEs) to investigate and compare the influence of Suwannee River Humic Acid (SRHA) (model humic acid) and Bovine Serum Albumin (BSA) (model protein) on colloid deposition in a column packed with saturated iron oxide-coated quartz sand. Study results suggest that adsorbed SRHA may inhibit colloid deposition by occupying colloid sites on the porous medium. Conversely, BSA may promote colloid deposition by a ‘filter ripening’ mechanism. This study provides insight to understand the complex behavior of colloids in organic matter-presented aquifers and sand filters.

Effects of natural organic matter type and concentration on the aggregation of citrate-stabilized gold nanoparticles

The aggregation of 12 nm citrate-stabilized gold nanoparticles (cit-AuNPs) in the presence of four different natural organic matter (NOM) isolates and a monovalent electrolyte (KCl) was evaluated using time-resolved dynamic light scattering. All four NOM isolates stabilized the cit-AuNPs with respect to aggregation. However, specific effects varied among the different NOM isolates. At pH = 6 in 80 mM KCl, low concentrations (<0.25 mg C per L) of large molecular weight Suwannee River Humic Acid (SRHA) was required to stabilize cit-AuNPs, while larger concentrations (>2 mg C per L) of smaller Suwannee River Fulvic Acid (SRFA) were necessary at the same ionic strength. Suwannee River NOM (SRNOM) which contains both SRHA and SRFA behaved in a manner intermediate between the two. Pony Lake Fulvic Acid (PLFA), an autochthonous NOM isolate, provided substantial stability at low concentrations, yet aggregation was induced at NOM concentrations > 2 mg C per L, a trend that is hypothesized to be the result of favourable hydrophobic interactions between coated particles induced at increased surface coverage. For all NOM isolates, it appears that NOM adsorption or conformational changes at the AuNP surfaces result in significant increases in the hydrodynamic diameter that aren't attributable to NP-NP aggregation.

The effect of nitrate, bicarbonate and natural organic matter on the degradation of sunscreen agent p-aminobenzoic acid by simulated solar irradiation

Our experiments revealed that a model sunscreen agent, p-aminobenzoic acid (PABA), can be effectively transformed through reactions that are mediated by simulated solar irradiation. We systematically explored the effects of nitrate ions, bicarbonate and different types of natural organic matter (NOM) on the degradation of PABA by simulated solar irradiation. Experimental data suggest that these components ubiquitous in nature water have different influence on the rates of the photoinduced removal of PABA. Products were extracted and analyzed using LC/MS and a total of four products probably resulting from OH and NO2 radicals attack were identified and the possible reaction pathways were proposed. The findings in this study provide useful information for understanding the environmental transformation of sunscreen agent in aquatic system.

Effects of three natural organic matter types on cellulose acetate butyrate microfiltration membrane fouling

This study aimed to clarify the effect of interactions between membranes and natural organic matter (NOM), which is considered to be the major membrane foulant in wastewater treatment processes. Sodium alginate (SA), humic acid (HA) and bovine serum albumin (BSA) were used as NOM models. Hollow fiber membranes were prepared using cellulose acetate butyrate polymer (CAB). Filtration experiments were carried out using SA, HA and BSA solutions and the membrane fouling behavior was examined. NOM adsorption on CAB membranes was measured by quartz crystal microbalance with dissipation (QCM-D), where NOM solutions were flowed across CAB spin-coated quartz crystal sensors and adsorbed. SA showed more severe permeate flux decline during the early stage of filtration and lower recovery of permeate flux after backwashing compared with HA. The severe flux decline for SA was due to pore-plugging and cake formation with high molecular weight components. The BSA solution, with no high molecular components, showed a gradual permeate flux decline and resulted in lower permeate flux after 240 min filtration compared with HA. The gradual permeate flux decline with the BSA solution was due to ready adsorption of BSA on the CAB membrane.

Study on phenol adsorption from aqueous solutions on exfoliated graphitic nanoplatelets

Abstract In this study we report first data on exfoliated graphitic nanoplatelets (xGnPs) as a sorbent for phenol removal and preliminary evaluated the ability of different type of natural organic matter (NOM) to effectively disperse exfoliated graphitic nanoplatelets.

Effects of Humic Substances on Precipitation and Aggregation of Zinc Sulfide Nanoparticles

Nanoparticulate metal sulfides such as ZnS can influence the transport and bioavailability of pollutant metals in anaerobic environments. The aim of this work was to investigate how the composition of dissolved natural organic matter (NOM) influences the stability of zinc sulfide nanoparticles as they nucleate and aggregate in water with dissolved NOM. We compared NOM fractions that were isolated from several surface waters and represented a range of characteristics including molecular weight, type of carbon, and ligand density. Dynamic light scattering was employed to monitor the growth and aggregation of Zn-S-NOM nanoparticles in supersaturated solutions containing dissolved aquatic humic substances. The NOM was observed to reduce particle growth rates, depending on solution variables such as type and concentration of NOM, monovalent electrolyte concentration, and pH. The rates of growth increased with increasing ionic strength, indicating that observed growth rates primarily represented aggregation of charged Zn-S-NOM particles. Furthermore, the observed rates decreased with increasing molecular weight and aromatic content of the NOM fractions, while carboxylate and reduced sulfur content had little effect. Differences between NOM were likely due to properties that increased electrosteric hindrances for aggregation. Overall, results of this study suggest that the composition and source of NOM are key factors that contribute to the stabilization and persistence of zinc sulfide nanoparticles in the aquatic environment.

Quantifying ‘humics’ in freshwaters: purpose and methods

Natural organic matter (NOM) plays an important role in many environmentally relevant processes. NOM includes many different types of compounds, not all of which behave similarly. Much effort has gone into characterising some fractions of NOM (e.g. humic substances) in the different environmental compartments, in finding tracers to ascertain their origin, etc. However, few methods exist for quantifying the different types of NOM and, as a result, field studies have limited themselves to measuring only total or dissolved organic carbon. In this article, the few existing methods for humic substance quantification are reviewed, and the implications of the current lack of simple measurement methods are discussed in relation to two fields of high environmental relevance: trace element speciation modelling and natural colloid and engineered nanoparticle fate.

Effect of natural organic matter on cerium dioxide nanoparticles settling in model fresh water

The ecological risk assessment of chemicals including nanoparticles is based on the determination of adverse effects on organisms and on the environmental concentrations to which biota are exposed. The aim of this work was to better understand the behavior of nanoparticles in the environment, with the ultimate goal of predicting future exposure concentrations in water. We measured the concentrations and particle size distributions of CeO 2 nanoparticles in algae growth medium and deionized water in the presence of various concentrations and two types of natural organic matter (NOM). The presence of natural organic matter stabilizes the CeO 2 nanoparticles in suspension. In presence of NOM, up to 88% of the initially added CeO 2 nanoparticles remained suspended in deionized water and 41% in algae growth medium after 12 d of settling. The adsorbed organic matter decreases the zeta potential from about −15 mV to −55 mV. This reduces aggregation by increased electrostatic repulsion. The particle diameter, pH, electric conductivity and NOM content shows significant correlation with the fraction of CeO 2 nanoparticles remaining in suspension.

Influence of natural organic matter (NOM) quality on Cu–gill binding in the rainbow trout ( Oncorhynchus mykiss)

Natural organic matter (NOM) in aquatic environments reduces metal toxicity to fish by forming metal–NOM complexes, which reduce metal bioavailability, metal–gill binding and toxicity. However, differences in the chemical composition of different types of NOM (quality) could also affect metal–NOM binding and toxicity. We predicted that Cu–gill binding would vary in trout exposed to Cu in the presence of NOM of different qualities. NOM was collected from three sources: Luther Marsh (terrigenous ∼ allochthonous), Bannister Lake (nominally autochthonous), and from a local sewage treatment plant (designated Preston effluent). Excitation–emission matrix spectroscopy (EEMS) revealed that terrigenous Luther Marsh NOM was primarily humic acid-like material (74%), whereas Bannister Lake and Preston sewage effluent NOM had lower humic acid-like material but greater fulvic acid-like material (30% and 50%, respectively). The specific absorption coefficient (SAC) of Luther Marsh NOM was also much higher (SAC = 37.8), consistent with its darker color, compared to more autochthonous, lightly coloured Bannister Lake (SAC = 12.4) NOM, and Preston effluent NOM (SAC = 9.2). At low-moderate waterborne Cu (0–2,000 nmol L −1), all NOM isolates reduced Cu–gill accumulation by 70–90%. Surprisingly, there were no measurable differences in Cu–gill binding amongst the three NOM treatments when fish were exposed to Cu in the low-moderate range. Only at higher Cu (>2,000 nmol L −1) were differences observed, where terrigenous Luther Marsh and Preston effluent NOM reduced Cu–gill binding by 40–50% more than the more autochthonous Bannister Lake NOM. Although Cu–gill binding estimates using the HydroQual BLM showed similar trends, the BLM consistently underestimated Cu–gill binding. We conclude that differences in Cu toxicity at lower-moderate Cu concentrations in the presence of different types of NOM are not necessarily related to measurable differences in Cu–gill accumulation. Rather, we suggest that differences in Cu toxicity reported in the presence of different types of NOM might be explained by direct actions of NOM on the gills, which are quality dependent.

Removal of microcystins by PAC/UF

The removal of microcystins (MC) by powdered activated carbon adsorption/ultrafiltration (PAC/UF) was investigated, focusing on PAC dose and addition mode, MC initial concentration (expressed as MC-LR eq) and on the impact of background natural organic matter (NOM), assessed through model compounds (a mixture of tannic and humic acids) and Microcystis aeruginosa culture. Constant flow experiments were performed with a hydrophilic UF hollow-fibre membrane and a mesoporous fine-powdered activated carbon. In the absence of background NOM, PAC/UF with 10 mg/L PAC and up to 20 μg/L MC-LR eq feed concentration achieved 93–98% MC removal and a cycle-averaged permeate concentration below the drinking water guideline-value adopted by the World Health Organisation (WHO) for microcystin-LR variant. Single-pulse PAC dosing in the beginning of the UF-cycle allowed slightly lower MC concentration in the permeate compared to the multi-pulse PAC addition whereas no differences were found in terms of transmembrane pressure. Hydraulic retention time of 34 and 55 min resulted in similar permeate quality. NOM type and concentration and MC initial concentration determined the PAC dose to be used. While 10 mg/L PAC effectively controlled ca. 5 μg/L MC-LR eq in a model water with 2.5 mg/L NOM or with M. aeruginosa culture (cells and algogenic organic matter) 15 mg/L PAC were unable to achieve the WHO quality with a water containing higher concentrations of NOM (5 mg/L) and microcystins ( ca. 20 μg/L MC-LR eq).