Humic Substances as an Important Factor of Metal Migration in Surface Waters of Ukraine

The results of studies of humic substances and metals in rivers of the Pripyat’ river basin are discussed. It is shown that concentration of these natural organic compounds is within a wide range of values — from 8.9 to 167.7 mg/L (0.4–7.0 mmol C L−1). In river waters of the North Polessye it is above due to the predominance of peat and bog feeding in a forming of their runoff. In river waters of the Western Polesye the concentration of humic substances is in general much lower, but in some rivers it reaches approximately the same quantities as in the Northern Polesye. Humic substances are the predominant group of dissolved organic matter in studied river waters (73.3–88.3% C org). In the humic substance composition the high molecular compounds are dominated. The relative content of fractions with a molecular weight of 5.0–20.0 and > 20.0 kDa is 59.0–82.3% of the total concentration of humic substances. Prevalence of high molecular fraction of humic substances is reflected on their weight average molecular weight (M w), which is within 7.7–10.9 kDa. Humic substances in the high concentration have a significant influence on the behavior, migration and distribution of metals among their coexisting forms. In particular, the proportion of dissolved forms for such metals as iron and aluminum substantial increases because of complexation with humic substances which stabilize them in solution. Copper is found mainly as dissolved form due to complexation with humic substances. The close correlation between the content of titanium dissolved form and concentration of humic substances has not been established. The data on the distribution of metals among the complexes with dissolved organic substances of different chemical nature and also of anionic complexes with humic substances are given.

Dependence of microbial magnetite formation on humic substance and ferrihydrite concentrations

Peat is a natural substrate for growth of microorganisms because it is rich in compounds that microorganisms can use as sources of carbon, nitrogen and growth factors. Peat originating from Vlasina lake in Eastern Serbia is especially rich in organic matter. The content of humic substances (humic acid, fulvic acid and humine) is almost twice that found in other peat-rich regions of similar origin and geochemical age. Humic and fluvic acids are known to promote microbial growth. In this work, humic and fulvic acids were first extracted from Vlasina lake peat and then added to minimal medium (synthetic, low ionic strength medium). The humic substances were added separately and combined in a 1:1 ratio by mass to study their individual and combined effect on microbial growth of Escherichia coli ATCC 25922 (Gr–), Staphyloccocus aureus (Gr+) i Aureobasidium pullulans, strain CH-1. The microbial growth was measured microspectrophotometrically over a 24-hour period and growth curves were obtained for a range of acid concentrations between 25 µg cm-3 and 100 µg cm-3. It was found that both humic and fulvic acids promote the growth of all three microorganisms by up to a maximum of 40%-80% the extent of which varied with the concentration of the acid and the identity of the microorganism. In general, humic acid was found to result in higher microbial growth (at highest concentrations, up to ~80% for all three microbial species).

Realistic soil C sink estimate in dry forests of western Argentina based on humic substance content

Chemical and physical fractionation techniques were used to study the effects of organic and conventional management practices on soil organic matter (SOM) characteristics. We isolated SOM from: (i) organic animal‐based, manure‐amended (ORG‐AN), (ii) organic cash‐grain‐based, cover cropped (ORG‐CC), and (iii) conventional, cash‐grain‐based (CONV) rotations. We quantified the total C and N contents of humin (HN) and humic substances (HS), and light (LF), heavy (HF), fine organo‐clay, and organo‐sand fractions. Management changed the quantity and distribution of C and N in physically and chemically isolated fractions. The ORG‐CC soil had significantly greater quantities of C in its HN, HS, LF, and HF fractions than the CONV soil. Management impacted the distribution of C and N only in the LF fraction. The ORG‐CC had a larger percentage and proportion of C and N in its LF than the other soils. The percentage of soil N in HS was higher in the ORG‐AN and ORG‐CC than in the CONV soil. Even though the quantity of N in the CONV's HN equaled the other soils, it had the highest percentage and proportion of N allocated to this fraction. Farming systems did not significantly alter the C and N contents of HS or the quantity of C associated with selected particle‐size fractions; however, the C content of fine clay isolated from aggregated soil was significantly greater than the C content of clay isolated from loose soil. By isolating macroorganic matter (LF) in concert with HS and HN fractions, we were able to assess management practice impacts on SOM characteristics.

Results of long-term investigations of the content of iron in surface water bodies of various types, including the reservoirs of the Dnieper cascade, the Danube River (the Kiliya delta), the Desna River, rivers of the Pripyat, Southern Bug, Ros, Gorny Tikich, and Seret basins, the reservoirs formed on these rivers, some Shatsk lakes, and water bodies located within the territory of Kiev, are given in the paper. The occurrence of this metal mainly in the composition of suspended matter (61.4-97.3% Fetotal) is typical to river waters. In the branches of the Kiliya delta of the Danube River, iron migrates mainly in suspended form, which is conditioned by a high content of mineral suspended matter. A predominance of iron suspended form is observed in some small water bodies of Kiev, which is conditioned by intensive development of phytoplankton. In the reservoirs of the Dnieper cascade, iron occurs mainly in the dissolved form, which is conditioned by its binding into the complexes with organic matter. The degree of iron complexation in the studied water bodies accounts for 89-97% Fedis. In surface waters with high coloration (rivers of the Pripyat basin and the upper reservoirs of the Dnieper cascade), humic substances are of crucial importance in binding iron. In small water bodies, a significant portion of Fedis was found in the composition of neutral complexes with carbohydrates. Results of the study of molecular-mass distribution of anionic and neutral complex compounds of iron are discussed in the paper.

Soil organic matter (SOM) plays an important role in terrestrial ecosystems and agroecosystems. Changes in the agricultural sector in the Czech Republic within the past 25 years have had a negative impact on SOM content and contribute to gradual soil degradation. The aim of this study is to estimate the effect of long-term application of different mineral fertilizers (NPK) and organic manures (manure, cattle slurry) on soil chemical properties (quality of humus, available nutrients, and soil reaction). Soil samples were collected from Luvisol during two selected periods 1994–2003 and 2014–2016 from long-term field experiment carried out in Prague-Ruzyně (Czech Republic). Average annual temperature is 8.5 °C, and annual precipitations are 485 mm. Different fertilization regimes have been applied for 62 years. The crop rotation was as follows: cereals (45%), root crops (33%) and legumes (22%). Soil analysis—soil organic carbon (SOC) was determined by oxidimetric titration method. Short fractionation method for evaluation of humic substance (HS), humic acid (HA) and fulvic acid (FA) content was used. Absorbance of HS in UV-VIS spectral range was measured by Varian Carry 50 Probe UV-VIS spectrometer. Degree of humification (DH) and color index (Q4/6) were calculated from fractional composition data. Soil reaction was measured by potentiometric method. Available nutrients (phosphorus, potassium, magnesium, calcium) were determined by Mehlich II and Mehlich I methods and by ICP-OES. For data analysis, the following are used: exploratory data analysis, ANOVA, and principal component analysis (PCA). PCA analysis differentiated fertilizers into two categories: (1) variant NPK (lower quality of humus)—higher acidity, lower SOC and HS content, predomination of FA, higher DH and lower content of available nutrients; (2) variants with organic manures (higher quality of humus)—lower acidity, higher SOC and HS content, predomination of HA, middle DH, and high content of available nutrients. The main result of presented study is to give a synthesis of effect of different type of fertilizers on a sustainable organic matter management in arable soils, with respect to yields, food security and adaptation to predict climate changes. Long-term application of mineral fertilizers (NPK) without organic matter input can accelerate humus mineralization and soil quality degradation with all negative consequences such as (nitrogen leaching, higher availability of toxic element for plants, slow energy for soil microorganisms etc.). Application of organic fertilizers (manure and cattle slurry) helps to achieve the long-term stable yields while maintaining soil at optimum quality (long-term sustainable management with SOM). Principal component analysis is a useful tool for evaluation of soil quality changes.

Study of the organic matter evolution during municipal solid waste composting aimed at identifying suitable parameters for the evaluation of compost maturity

Humic and fulvic acids in environmental water were determined by UV spectrophotometry after concentration with diethylaminoethyl(DEAE)-cellulose and separation at pH 1 by centrifugation. The ranges of fulvic and humic acids in Katsura, Uji, Kidzu and Yodo Rivers were from about 0.50 to 3.2 mg/l and 0.025 to 0.2 mg/l, except for the sampling points, which were located downstream of a sewage-disposal plant. Fulvic acid was predominant in these rivers. The concentrations of humic substances were high in the summer and low in the winter. The concentrations of humic substances in these rivers decreased fairly much from December of 1992 to August of 1993. The annual changes in the values of humic substances during 1993 to 1996 were smaller than the change from 1992 to 1993. The trends for the seasonal and annual changes in the concentration of the trihalomethane formation potential in Yodo rivers were almost consistent with those of humic substances.

1. Although the mass of dissolved organic matter (DOM) often exceeds that of living organisms in freshwaters, little is known about the roles of its constituent molecules as sources of energy and information for aquatic organisms. In the present review attention is focused on free amino acids (FAA) and humic substances (HS) as examples of labile and refractory components within DOM.2. The following questions are addressed. (i) What are spatiotemporal patterns in the distribution of DOM, HS and FAA? (ii) What are the origins of the components of DOM and how are their concentrations regulated? (iii) What is the significance of the spatial and temporal distributional patterns of DOM, HS and FAA to detritivorous invertebrates and other organisms associated with them? (iv) What is the relevance of DOM to the food web concept and to the biochemical ecology of freshwater ecosystems?3. Concentrations of DOM, FAA and HS within lentic ecosystems are ranked as follows: Sediment pore water > Air–water interface > Midwater column. Comparisons between water bodies show that the concentrations of labile constituents of DOM, such as FAA, are usually positively correlated with base cations, nutrients and biological activity. In contrast, HS concentrations are negatively correlated with base cations or nutrients but positively correlated with the rate of biological degradation (the maximum values occurring in the autumn). The FAA : HS ratios might serve therefore as an indicator of the potential productivity of a water body.4. External sources of DOM in general, and FAA and HS in particular, include rainwater, windborne material, surface flow and groundwater. The relative importance of these allochthonous sources of DOM decreases along the length of lotic ecosystems and also with increase in size of lentic ecosystems. Internal sources of FAA and HS include synthesis or polymerization from existing organic matter, degradation of organic matter and release from both living and dead organisms. The net accumulation of DOM released by living bacteria, phytoplankton, epilithon, macrophytes and invertebrates is much reduced due to heterotrophic uptake. Hence, most of the allochthonous DOM in freshwater originates from dead organic matter deposited on the sediment. Phytoplankton‐dominated ecosystems may, however, differ, as most of their DOM may be recycled within the water column.5. The factors that determine the external concentrations of DOM, FAA and HS are discussed. Evidence is cited in support of the following testable hypotheses. (i) The rates of production of DOM components will be favoured by increasing base cation and nutrient concentrations. (ii) Colloidal clay, base cations, biopolymers and living organisms, particularly bacteria, facilitate the removal of HS. Consequently, base‐rich eutrophic waters tend to have lower HS concentrations than oligotrophic, base‐deficient waters. (iii) As a result of higher productivity and selective removal of FAA, eutrophic waters tend to have higher FAA concentrations than those that are oligotrophic.6. Labile DOM components, such as FAA, act as sources of information for aquatic organisms. More research is needed in this field. There is a consensus that DOM acts as an important source of energy for aquatic bacteria, thus forming the microbial loop. However, higher eukaryotic organisms also utilize DOM, including components released by bacteria and plants as metabolic end‐products and photoassimilates, respectively. As a result, these DOM components may be more important as food for macrodecomposers than the microdecomposers themselves. HS may also benefit aquatic organisms by promoting their growth and protecting them from inimical forces. Conversely, the removal of photons and the release of toxins by HS may be detrimental to aquatic organisms.7. It is concluded that the central dogma of the foodweb, and its implicit assumption that the energy flow in aquatic ecosystems can be quantified solely by measuring rates of photosynthesis, ingestion of solid food and its digestion by higher organisms, is invalid. To extend our understanding of the role of DOM as a source of nutrition and information to aquatic organisms it is suggested that the subject should be studied within the context of ‘modules’ which have the following properties: (i) the components have co‐evolved; (ii) the more vulnerable components will have protective mechanisms; (iii) the components will derive mutual benefits from co‐existence; (iv) sedentary components will release kairomonal attractants or developmental primers; (v) living components will exchange energy and information; (vi) the module will collapse following the removal of strongly interactive keystone species. An example of a three‐component, three‐subset module, is provided by tubificid worms, epilithic bacteria and algae. A more complex module consisting of pulmonate snails, associated macrophytes, their epiphytic bacteria and algae has four components and six subsets. The elucidation of the interactive mechanisms within such modules demands an interdisciplinary approach, involving microbiology, biochemistry and behavioural biology.

Chlorination is the most widely used technique for disinfection of drinking water. A consequence of chlorination is the formation of Disinfection By-Products (DBPs). The formation of DBPs in drinking water results from the reaction of chlorine with naturally occurring organic materials, principally humic and fulvic acids. This paper focuses on the effect of humic substances on the formation of twenty-four compounds belonging to different categories of DBPs. This investigation was conducted in two water treatment plants in Greece, Menidi and Galatsi, from July 1999 to April 2000. Humic substances were determined by the diethylaminoethyl (DEAE) method with subsequent UV measurement. The techniques used for the determination of DBPs were liquid-liquid extraction, gas chromatography and mass spectrometry. The concentrations of DBPs were generally low. Total trihalomethanes (TTHMs) ranged from 5.1 to 24.6 microg L(-1), and total haloacetic acids (HAAs) concentration ranged from 8.6 to 28.4 microg L(-1), while haloaketones (HKs) and chloral hydrate (CH) occurred below 1 microg L(-1). The content of humic substances was found to influence the formation of DBPs and especially TTHMs, trichloroacetic acid (TCA), dibromoacetic acid (DBA), CH, 1,1-dichloropropanone (1.1-DCP) and 1,1,1-trichloropropanone (1,1,1-TCP). Seasonal variation of TTHMs and HAAs generally followed that of humic substances content with peaks occurring in autumn and spring. The trends of 1,1-DCP, 1,1,1-TCP and CH formation seemed to be in contrast to TTHMs and HAAs. Trends of formation of individual compounds varied in some cases, probably due to influence of parameters other than humic substances content. Statistical analysis of the results showed that the concentrations of TTHMs, CH, 1,1-DCP, 1,1,1-TCP, TCA and DBA are strongly affected from humic substances content (at 0.01 confidence level). The opposite is true for dichloroacetic acid (DCA) concentration. Humic substances also vary to a statistically significant degree during different months, as well as the concentrations of TTHMs, CH, 1,1-DCP, 1,1,1-TCP, TCA and DCA. The variance of DBA was not statistically significant. Regarding the effect of sampling station, humic substances content showed no statistically significant difference between the two raw water sources studied.

The reaction of aquatic humic substances with copper(II) ions: an ESR study of complexation

The concentrations of total and individual free amino-acids (TFAA, FAA) and humic substances (HS) were measured by HPLC in the midwater column (MWC), air-water interface (AWI) and sediment pore water (SPW) in the oligotrophic, dystrophic Isle of Thorns lake and the eutrophic Lewes Brooks drainage channel in East Sussex, UK, during each of the four seasons. Pesticide levels were low, usually below detection levels in both water bodies. At the temporal level there were tendencies for the concentration of both FAA and HS to be lowest in the winter months and for the HS concentrations to be higher in the autumn in both water bodies. At the spatial level the eutrophic Lewes Brooks was characterized by having much higher FAA/HS ratios than the oligotrophic Isle of Thorns lake and it is suggested that further comparative studies be undertaken to verify whether the FAA/HS ratios may have general application in the classification of water bodies on a trophic basis. The concentrations of TFAA are higher in the SPW and AWI than in the MWC in both water bodies and the HS concentrations are much higher in the SPW than in the MCW Statistical analyses support the view that the FAA in the MWC are mainly derived from the SPW whereas the FAA in the AWI have a different origin. The data obtained is used to address the following questions: (a) How do the spatio-temporal patterns of FAA and HS in the present study areas compare with those of other water bodies? (b) What are the origins of the FAA and HS and how are their concentrations regulated? (c) Are the distributional patterns of FAA and HS of special significance to invertebrate detritivores? (d) How can the differences in the FAA and HS patterns in oligotrophic and eutrophic waters be explained? What are the conclusions and testable hypotheses arising from the present study?

ABSTRACTConcentrations of humic substance (HS) in deep groundwater from sedimentary formations were determined by the carbon concentration-based DAX-8 resin isolation technique. The groundwater samples were collected from test galleries at depths of 140, 250 and 350 m at the Horonobe Underground Research Laboratory (URL) in Hokkaido, and two observation wells with different depths of 560 and 1050 m in Niigata, Japan. The analytical condition was optimized for the groundwater samples with a high salinity and a high concentration of dissolved organic matters (DOMs). The analytical results showed that the HS concentrations varied from 7.8 to 23.5 mg-C dm−3, depending on the depth and the area. The HS proportions to DOM (%HS) were evaluated to be 58 – 67% and slightly decreased in the deeper groundwater. The regression analysis showed that the HS concentrations are positively correlated with the DOM concentrations. In addition, the low deviation of the %HS values from the slope in the regression equation indicated that the slight variation of %HS can be trivial in the prediction of the concentration of HS. In previous studies, HS concentrations in the groundwater had been determined with a large uncertainty and potential usage of the regression equation for the prediction had not been elucidated. Therefore, the results in this study can provide useful information on the HS concentration and its prediction from the DOM concentration in deep groundwater from sedimentary formations.

The paper presents data on organic carbon concentrations in riverine suspended matter and surficial bottom sediments measured in the estuary of the Razdol’naya River during the period of ice cover (February 2010). In the suspended matter, humic substances and phytoplankton accounted for 30% and 14% of total organic carbon, respectively. The concentration of humic substances in riverine suspended matter was determined for the first time by spectrophotometry. The concentration of phytoplankton carbon was calculated from the chlorophyll-a content. Concentrations of organic carbon, humic substances, and chlorophyll-a were measured in the surface sediment layer. The proportions of these three components show no marked variability with an increase in salinity to 23‰. The degree of humification in bottom sediments was about 52%. Organic carbon concentrations were almost an order of magnitude lower and the proportion of bioavailable (nonhumified) carbon was two times lower in the bottom sediments than in the riverine suspended matter.