Fulvic Compounds Research Articles

Monitoring of water quality with HPLSEC and fluorescence method in the ozonated recirculating aquaculture system

In recirculating aquaculture systems (RAS), it is important to monitor the water quality to keep the fish healthy. Especially in water treatment with oxidizing agents, for example, ozone (O3) or hydrogen peroxide (H2O2), the monitoring of the quality of dissolved organic matter (DOM) in water is advisable to keep track of the treatment’s effect. Previously in wastewater treatment plant (WWTP) studied, HPLSEC and fluorescence method for monitoring and characterization of organic matter was used here to track the effect of oxidative treatments; 5 duplicated treatments (2 × O3, 1 × O3 + H2O2, 1 × H2O2, 1 × control) were performed for four months with weekly samplings. Systems that contained O3 injection reduced fluorescence on average over 90%, except tyrosine-like fluorescence with removal of 80%. Combined O3 + H2O2 treatment did not bring any advantages over pure O3 treatment, and H2O2 had no significant effect on fluorescence. Humic and fulvic compounds were detected to largely be derived from inlet lake water, while large protein-like structures were mostly created in RAS. A peak of benzoic acid-like molecules was also detected in all RAS waters. Treatments did not change the molecular weight profile of DOM systems and inlet water, having most of their fluorescence coming from medium-sized (108–1322 Da) molecules. DOC was lower in O3 treatments, but the linear connection between DOC and fluorescence was not observed, although this was proposed in earlier studies. Most likely, the oxidizing treatments induce change to DOM in a way that such comparison becomes inaccurate, although this must be studied further in the future.

Spectroscopy Techniques for Monitoring the Composting Process: A Review

Composting is described as a sustainable alternative to organic waste reuse from the agricultural and household sectors. The organic matter degradation and stabilization product presents great variability due to the waste composition used. Thus, the use of techniques that allow the monitoring of the decomposition process is necessary to determine the quality of the final product. Therefore, this review critically analyzes and updates the chemical spectroscopy methods described for the evaluation of the organic matter transformation in the composting process to optimize and generate amendments for agricultural use. This review examines spectroscopic techniques such as ultraviolet-visible (UV-Vis), infrared (IR), fluorescence, and 13C NMR reported for the evolution and maturation of carbonate structures in composting. In addition, they are used in the study of indicators for monitoring the degradation of complex structures, such as sugars and proteins, for the formation of precursors that are responsible for the formation of highly stabilized substances such as humic and fulvic compounds. Finally, these parameters may be used to elucidate organic matter degradation and its stabilization process, establish patterns that characterize each stage of composting along with its physicochemical characteristics, and monitor potential phytotoxicity levels.

Relevant issues of determining total organic carbon in water

Introduction. Total organic carbon (TOC) is a generalized indicator characterizing the pollution of water bodies with organic substances. In accordance with SanPiN 2.1.3864-21 for drinking water, the standard value of TOC content is set equal to 5 mg/dm3. Currently, total carbon analyzers are widely used to determine TOC. Despite its undoubted advantages, the determination of TOC on analyzers has many bottlenecks. Purpose of the study. Analysis of the TOC values of water samples of various origins, obtained using different methods and measurement conditions. Materials and methods. Determination of TOC was carried out with a total carbon analyzer TOC-VCHP (Shimadzu) in accordance with the operation manual of the difference measurement method (TOC) and non-blown organic carbon (NPOC). The objects of study were the water of natural sources, the centralized water supply system of various districts of Moscow, standard solutions of organic compounds. Results. It has been established that during the operation of the analyzer in the analysis of natural and drinking water, incomplete disclosure of humic and fulvic compounds is observed, which cannot be established by standard tests provided for carbon analyzers. The lack of standardized procedures for degassing sparkling water can lead to TOC errors of thousands of percent. Limitation. The limit of determined TOC values was 0.5 mg/dm3. Conclusion. To control the correctness of the determination of TOC in drinking, natural and waste waters, standard samples of humic compounds are required that are characteristic of a particular area with a certified TOC value. It is required to develop and implement a standard procedure for degassing gaseous samples when determining TOC, since the lack of control of this stage of analysis can lead to unacceptable errors in the determination.

Metal–organic complexes as a major sink for rare earth elements in soils

Environmental contextThe role of rare earth elements in soil–plant systems remains unclear. We use continuous-flow extraction, designed to mimic natural conditions while minimising artefacts, to study in vitro chemical fractionation of rare earth elements in soil. The study reveals a predominant association of rare earth elements and metal-organic complexes independent of soil type and contamination, and thereby provides valuable insights into the behaviour of these elements in soil–plant systems. AbstractThe role of rare earth elements (REEs) in soil–plant systems has attracted increasing attention but still remains somewhat unclear. Along invivo studies on the uptake of REEs by plants, invitro chemical fractionation of REEs in soil according to their physicochemical mobility can offer additional insights into the behaviour of REEs. In the present work, the fractionation of REEs was studied with the example of background, aerially and hydrogenically contaminated soil samples using dynamic (continuous flow) extraction, which allows natural conditions to be mimicked and artefacts to be minimised. The eluents applied addressed exchangeable, specifically sorbed, bound to Mn oxides, bound to metal–organic complexes, and bound to amorphous and poorly ordered Fe/Al oxides fractions extractable by 0.05M Ca(NO3)2, 0.43M CH3COOH, 0.1M NH2OH·HCl, 0.1M K4P2O7 at pH 11, and 0.1M (NH4)2C2O4 at pH 3.2 respectively. The distribution of trace metals (such as Pb, Cu, Zn, Ni) between separated fractions varies with sample and is dependent on the type of contamination. However, for all samples, the recoveries of REEs by pyrophosphate are surprisingly high, up to 40–45% of their total concentrations in background and anthropogenically transformed floodplain soils. As compared to metal–organic complexes, the contents of REEs bound to Fe/Al oxides are fairly low, no more than 12%. REEs in other fractions may be taken into consideration only for aerially contaminated soil. Such a predominant association of REEs and metal–organic complexes (i.e. humic and fulvic compounds) independent of the type of soil has not been reported before.

Applicability of Fluorescence and Absorbance Spectroscopy to Estimate Organic Pollution in Rivers.

This article explores the applicability of fluorescence and absorbance spectroscopy for estimating organic pollution in polluted rivers. The relationship between absorbance, fluorescence intensity, dissolved organic carbon, biochemical oxygen demand (BOD), chemical oxygen demand (COD), and other water quality parameters were used to characterize and identify the origin and the spatial variability of the organic pollution in a highly polluted watershed. Analyses were performed for the Iguassu River, located in southern Brazil, with area about 2,700 km2 and ∼3 million inhabitants. Samples were collect at six monitoring sites covering 107 km of the main river. BOD, COD, nitrogen, and phosphorus concentration indicates a high input of sewage to the river. Specific absorbance at 254 and 285 nm (SUVA254 and A285/COD) did not show significant variation between sites monitored, indicating the presence of both dissolved compounds found in domestic effluents and humic and fulvic compounds derived from allochthonous organic matter. Correlations between BOD and tryptophan-like fluorescence peak (peak T2, r=0.7560, and peak T1, r=0.6949) and tyrosine-like fluorescence peak (peak B, r=0.7321) indicated the presence of labile organic matter and thus confirmed the presence of sewage in the river. Results showed that fluorescence and absorbance spectroscopy provide useful information on pollution in rivers from critical watersheds and together are a robust method that is simpler and more rapid than traditional methods employed by regulatory agencies.

Transmission electron microscopy investigation of colloids and particles from landfill leachates

Leachates collected at two (active and closed) municipal solid waste (MSW) landfills were examined for colloids and particles by transmission electron microscopy, energy dispersive spectrometry, selected area electron diffraction and for the chemical compositions of the filtrates after the filtration to 0.1 µm and ultrafiltration to 1 kDa (~ 1 nm). Six groups of colloids/particles in the range 5 nm to 5 µm were determined (in decreasing order of abundance): carbonates, phyllosilicates (clay minerals and micas), quartz, Fe-oxides, organics and others (salts, phosphates). Inorganic colloids/particles in leachates from the active landfill predominantly consist of calcite (CaCO(3)) and minor clay minerals and quartz (SiO(2)). The colloids/particles in the leachates from the closed landfill consist of all the observed groups with dominant phyllosilicates. Whereas calcite, Fe-oxides and phosphates can precipitate directly from the leachates, phyllosilicates and quartz are more probably either derived from the waste or formed by erosion of the geological environment of the landfill. Low amounts of organic colloids/particles were observed, indicating the predominance of organic molecules in the 'truly dissolved' fraction (fulvic compounds). Especially newly formed calcite colloids forming particles of 500 nm and stacking in larger aggregates can bind trace inorganic contaminants (metals/metalloids) and immobilize them in landfill environments.

FLUXY: a simple code for computing steady-state metal fluxes at consuming (bio)interfaces, in natural waters

Environmental context. Until now there was no user-friendly code for metal flux computations in natural mixtures of aquatic complexants, which are however essential for prediction of metal bioavailability. The present paper describes the capabilities and limitations of one of the only two such codes presently available, called FLUXY. The results of FLUXY are compared with those of another code, and it is shown that it enables quick computation and is applicable to natural ligands under many environmental conditions. Abstract. The computation of metal fluxes at consuming interfaces like microorganisms or bioanalogical sensors is of great importance in ecotoxicology. The present paper describes the application of a simple code, FLUXY, for the computation of steady-state metal fluxes in the presence of a very large number of complexes, with broadly varying values of equilibrium constants, rate constants and diffusion coefficients. This code includes two major limiting assumptions, namely, (i) the existence of excess of ligand (L) compared with metal (M), and (ii) the fact that in a series of successive MLn complexes, the reaction is the rate-limiting step in flux computation. The domains of rate constants for which these assumptions are valid are tested systematically, and the corresponding errors are evaluated by comparison with the exact results given by another code: MHEDYN. FLUXY is then applied and compared with MHEDYN for case studies typical of aquatic systems, namely (i) a culture medium containing simple ligands; (ii) solutions of fulvic compounds including a broad distribution of complex stability and rate constants; and (iii) suspensions of aggregates with a broad size distribution. It is shown that FLUXY gives good results for cases (i) and (iii). Application to case (ii) (fulvic compounds) is also feasible under conditions that are clearly described. Altogether, FLUXY and MHEDYN are complementary. In particular, FLUXY only computes steady-state fluxes and requires the fulfilment of a few conditions, but when these are met, computations require much less computer time than MHEDYN.

Encyclopedia of analytical science

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Size distribution of copper complexing ligands in tropical freshwaters

The size distribution of soluble copper complexing ligands (<0.45 μm) present in water samples collected from a tropical river system was characterised using a combination of equilibrium dialysis and differential pulse anodic stripping voltammetry. The proportion of copper complexing capacity associated with small molecular weight (<1,000 Dalton) ligands increased progressively from 40% in the upper catchment to 79% at a lowland floodplain/wetland location. This increase indicated the dominant role of the floodplain as a source of low molecular weight ligands to the river system. Asignificant proportion of copper complexation was also associated with the >14,000 Dalton fraction. As the majority of soluble iron was also associated with this fraction, it is likely that this complexing pool contains organic ligands adsorbed to the surface of inorganic colloids as well as large molecular weight ligands. Destruction of dissolved organic matter by sample pre-treatment with UV light resulted in a complete loss in copper complexation capacity detectable by anodic stripping voltammetry. This confirmed that the observed complexation of copper was associated with organic ligands and not inorganic components of the sample. A statistically significant linear correlation was observed between copper complexation capacity and fluorescence (340 nm excitation/440 nm emission). This indicated that the ligands were most likely to be associated with humic and fulvic compounds having conjugated molecular structures. Overall, the study emphasises the role of low molecular weight organic ligands in controlling copper speciation in tropical freshwater systems.

Human exposure to trihalomethanes in drinking water

Halogenated hydrocarbon compounds, some of them recognized as carcinogenic to different animal species can be found in drinking water. Chloroform, bromodichloromethane, dibromochloromethane and bromoform are the most important trihalomethanes found in potable water. They are produced in natural waters during chlorinated desinfection by the halogenation of precursors, specially humic and fulvic compounds. The review, in the MEDLINE covers the period from 1974 to 1998, presents the general aspects of the formation of trihalomethanes, sources of human exposure and their toxicological meaning for exposed organisms: toxicokinetic disposition and spectrum of toxic effects (carcinogenic, mutagenic and teratogenic).

A Generalized Description of Aquatic Colloidal Interactions: The Three-colloidal Component Approach

This paper describes several possible interactions among the different types of organic and inorganic aquatic colloids, based on our present knowledge of their size, electric charge, and conformation. The physicochemical properties of the different groups of colloids are described. Emphasis is placed on the various types of organic components, including fulvic compounds. Subsequently, the role of each colloid class is discussed with respect to homoaggregation (aggregation within a given colloid class) and heteroaggregation (aggregation among different colloid types). On the basis of a synthesis of literature reports, microscopic observations of natural colloids, experimental results obtained with model systems, and numerical simulations, it is concluded that the formation of aggregates in aquatic systems can be understood by mainly considering the roles of three types of colloids: (i) compact inorganic colloids; (ii) large, rigid biopolymers; and (iii) either the soil-derived fulvic compounds or their eq...

Palaeohydrological variation in a tropical river catchment: a reconstruction using fluorescent bands in corals of the Great Barrier Reef, Australia

Massive, long-lived corals in inshore waters of the Great Barrier Reef contain yellow-green fluorescent bands. These bands are due to terrestrial humic and fulvic compounds incorporated into the coral skeleton during high river flow events. Fluorescence measurements are presented for two colonies of Porites spp. from locations in the path of the Burdekin River floodwaters the major river in north Queensland draining into the Coral Sea. The records extend from AD 1737 to 1980 and 1644 to 1986, respectively. The two independent coral records show a high degree of similarity. The two series are combined and used to reconstruct Burdekin River runoff for the period AD 1644 to 1980. The regression model accounts for 83% of the annual (water year) variability of Burdekin River flow and is verified over independent data. The 337-year reconstruction thus increases by threefold the length of record for considering interannual to decadal climate variations in northeast Australia. Instrumental and reconstructed Burdekin River runoff are closely related to an index of summer monsoon rainfall in Queensland. Thus, the reconstruction provides insights into the behaviour over the past three centuries of both a major tropical river system and the highly variable summer monsoon rainfall in northeast Australia. The reconstructed series shows wetter conditions (higher runoff) in the late-seventeenth to mid-eighteenth centuries and in the late-nineteenth century. Drier conditions (lower runoff) are reconstructed in the late-eighteenth to mid-nineteenth centuries and in the mid-twentieth century.

Investigation of fulvic acids from peat using capillary electrophoresis (CE)

AbstractThe aim of this work was to characterize the fulvic acids (FA) extracted from peat by use of capillary electrophoresis (CE). Two FA extracts have been obtained using two different extractants (0.1 M NaOH and 0.1 M NaOH plus 0.1 M Na4P2O7, Na+PP). The CE runs wre performed using a coated silica capillary, and several buffer solutions at different PH values. The results obtained show that the Fa extracts may be well characterized by CE even if the isolelectric point of the fulvic compounds is very low. The best fractionation has been obtained using a buffer borate at PH 8.9 as funning buffer. The charcterization of the two extracts also showed some important differences between the NaOH extract and the Na+PP extract.

Adsorption of poly(ethylene glycol)s on mercury/aqueous solution interface 1. Kinetics of PEG 8000 adsorption

In order to study the influence of the adsorption of fulvic compounds on voltammetric signals and to understand better the adsorption of these compounds on hydrophobic natural water interfaces, adsorption studies of macromolecules such as poly(ethylene glycol) (HO(CH 2CH 2O) n ) with molecular weight of 8000 were done on the mercury/water interface by a.c. voltammetry at the potential of zero charge. The maximum surface concentration, adsorption equilibrium constant and adsorption rate constant have been determined from the global adsorption mechanism, controlled by two determining steps: diffusion and kinetics of adsorption at the interface.

High-performance liquid chromatographic study of nickel complexation with humic and fulvic acids in an environmental water

A high-performance liquid chromatographic method was developed to determine cation-exchange capacities and conditional association constants for metal interactions with humic and fulvic materials present in environmental waters. The method does not require prior extraction of the humic and/or fulvic compounds. A salt-gradient is used, which exploits the size-exclusion and adsorption properties of a coated porous silica stationary phase, in order to separate and permit the measurement of the free and complexed metal concentrations. The results are subjected to a weak and strong binding site interpretation.

Lead-210 chronology of the Scandinavian SWAP sites

In the Surface Water Acidification Project (SWAP) sediment profiles from five Scandinavian sites were analysed for 210 Pb by using refined isotope dilution alpha spectrometry. The 210 Pb parameters of these lakes were very similar to those obtained for protected forest lakes with no land-use activities. These data demonstrated almost exclusive atmospheric inputs and an internal deposition regulated by the organic fractionation and the grain-size distribution in the sediments. Preliminary speciation experiments showed minor losses of 210 (≤ 5%) through enhanced dissolution of fulvic compounds at acid conditions (pH ≥ 4). The sediment accumulation rates (constant rate of unsupported 210 Pb supply (CRS) model) of the lakes gradually increased, by at least a factor of three, over the past century although 210 Pb parameters did not show any strong signs of enhanced land-use activities. This is perhaps caused by more efficient preservation of the sediments through humic precipitation under more acid conditions.

Special issue on humic and fulvic compounds: Buffle, J. (guest editor) et al., 1990. Analytica chim. Acta, 232(1):237pp; 18 papers

Special issue on humic and fulvic compounds: Buffle, J. (guest editor) et al., 1990. Analytica chim. Acta, 232(1):237pp; 18 papers

Effect of physico-chemical heterogeneity of natural complexants : Part I. Voltammetry of labile metal—fulvic complexes

A theoretical study of the effect of the physico-chemical heterogeneity of complexants such as fulvic compounds on d.c. polarographic curves is described. These compounds have been strongly implicated in playing a decisive role in trace cation complexation in natural systems. Their main feature is their wide range of complexation energy, which stems from their intrinsic properties: polyfunctionality, polyelectrolytic character and conformational properties. The whole of these complexing properties may be represented by complexation distribution functions. It is shown that, in the formation of labile metal—fulvic complexes and in the absence of adsorption and kinetic effects, it is possible to obtain from a single voltammetric curve important parameters related to metal speciation, namely the average diffusion coefficient of the complexes and the parameters describing the equilibrium complexation distribution functions.

Speciation of Pb-210/Po-210 in aquatic systems and their deposits

Lead-210 speciation was carried out on previously examined aquatic deposits of known ages and geochemical histories. The main separated fractions were fulvic, humic, humin and mineral-bonded humics. these organic components were wet-oxidized and their 210Po was extracted by coprecipitation with Fe 3+, distillation at 450°C and self-deposition on silver-discs. The 210Po activities were determined by isotope dilution and alpha spectrometry techniques. Nineteen samples from three lakes and one ombrotrophic peat-hummock in southern Sweden; and three fjords of Skagerrak, North Sea, were investigated. Humic materials proved to trap and preserve aquatic unsupported 210Pb, especially in lakes and peats. Fulvic compounds, on the other hand, seem to enhance the mobility of unsupported 210Pb particularly under acidic conditions. However, the fulvic fraction of marine sediments showed higher amounts of unsupported 210Pb. Our results show that the supported 210Pb is incorporated with the organo-mineral complexes, the NaOH-insoluble fraction. The 210Pb activity of this fraction was found to converge to the expected supported 210Pb of sediment samples older than 100 years or so. Some younger sediments may also show the last mentioned observation. This might serve as an alternative for evaluating the supported 210Pb in 210Pb dating.

Adsorption of fulvic-like organic ligands and their Cd and Pb complexes at a mercury electrode

Benzyliminodiacetic acid, pyridine-2-carboxylic acid and pyridine 2,6-dicarboxylic acid were used as model compounds of the components of natural pedogenic fulvic acids to study the most important factors related to their adsorbing and complexing properties which may affect the behaviour of their complexes at a mercury electrode. In the absence of metal ions, their adsorption properties were studied by alternating current polarography, at different pHs and ligand concentrations. The adsorption of their Pb and Cd complexes was studied by normal pulse polarography, in a low concentration range. Comparison of all the experimental data shows that adsorption of the free ligand and the complexes is always primarily due to the hydrophobic part of the ligand which tends to accumulate on the Hg surface. Any electrically charged group of the molecule (either positive or negative) increases its hydrophilicity and decreases its adsorbability. However, this effect plays a significant role only when the distance between the charged and hydrophobic groups is small. For instance, it was found to be much less important with the benzyliminodiacetic ligand than with the other two ligands. For all the ligands and complexes, 10 −6 M is the approximate limit below which the adsorption is small in the normal time-scale of a dropping mercury electrode, due to the small adsorption equilibrium constants of free or protonated ligands and to the slowness of the overall adsorption rate of the complexes. These results are compared to those obtained with pedogenic fulvic compounds.