Different Fractions Of Organic Matter Research Articles

Evaluation of the Different Fractions of Organic Matter in an Electrochemical Treatment System Applied to Stabilized Leachates from the Bordo Poniente Landfill in Mexico City

The presence of refractory compounds in stabilized leachates makes treatment complex. In leachate treatment systems, the lack of data on the characterization of leachates and effluents makes it difficult to track and explain the evolution of organic matter. In this study, the fractionation of chemical oxygen demand (COD) and humic substances, including humic acids (HA) and fulvic acids (FA), in addition to the application of spectroscopic techniques (Fourier transform infrared and ultraviolet–visible spectroscopy), were used to solve this data gap. A treatment system was proposed: electro-coagulation (EC) and electro-oxidation (EO). Optimal conditions (maximum COD removal) were EC, I: 4.3 A, stirring: 120 revolutions per minute, and pH: 7; EO, added NaCl: 1.0 g L−1, distance between electrodes: 0.75 cm, I: 2 A, and pH: 7. Under optimal conditions COD, HA, and FA % removals were achieved: EC: 64, 69, and 63; EO: 83, 40, and 55; respectively. In EC, the % of biodegradable COD increased from 26 to 39 and in EO it increased from 39 to 58. The biodegradability index increased from 0.094 to 0.26 with EC and reached 0.46 with EO. The generated data allowed us to establish the transformations of organic matter in the process, which was useful for understanding the processes and functioning as a tool for improving treatment systems.

Variability of biochemical compounds in surface sediments along the eastern margin of the Arabian Sea

Different fractions of organic matter in surface sediments from three transects along the eastern margin of the Arabian Sea (AS) were quantified to determine the sources of organic matter, and also to study its impact on microbial community structure. From the extensive analyses of different biochemical parameters, it was evident that the distribution of total carbohydrate (TCHO), total neutral carbohydrate (TNCHO), proteins, lipids, and uronic acids (URA) concentrations and yield (% TCHO-C/TOC) are affected by organic matter (OM) sources and microbial degradation of sedimentary OM. Monosaccharide compositions from surface sediment was quantified to assess the sources and diagenetic fate of carbohydrates, suggesting that the deoxysugars (rhamnose plus fucose) had significant inverse relationship (r = 0.928, n = 13, p < 0.001) with hexoses (mannose plus galactose plus glucose) and positive relationship (r = 0.828, n = 13, p < 0.001) with pentoses (ribose plus arabinose plus xylose). This shows that marine microorganisms are the source of carbohydrates and there is no influence of terrestrial OM along the eastern margin of AS. During the degradation of algal material, the hexoses seem to be preferentially used by heterotrophic organisms in this region. Arabinose plus galactose (glucose free wt %) values between 28 and 64wt% indicate that OM was derived from phytoplankton, zooplankton, and non-woody tissues. In the principal component analysis, rhamnose, fucose, and ribose form one cluster of positive loadings while glucose, galactose, and mannose form another cluster of negative loadings which suggest that during OM sinking process, hexoses were removed resulting in increase in bacterial biomass and microbial sugars. Results indicate sediment OM to be derived from marine microbial source along the eastern margin of AS.

Soil Organic Matter of Tidal Marsh Permafrost-Affected Soils of Kolyma Lowland

Soils of the Arctic sea coasts are one of the least studied due to the complex logistical accessibility of the region, as well as the severe climatic conditions. The genesis of these soils is determined by several factors of soil formation simultaneously—cryogenesis, the influence of river alluvial processes, as well as the tidal influence of the sea. The paper presents data on the morphological structure of soils formed on the seacoast of the East-Siberian Sea (Kolyma Lowland, North Yakutia). Under the influence of cryogenesis and sea water tidal input, marsh soils are formed, with a relatively high level of salinity and the development of gleyization. Autochthonous and allochthonous soil organic matter play a leading role in marsh soil formation here, including the possible accumulation and biochemical transformation of incoming pollutants (e.g., hydrocarbons). The main objective of the study was to evaluate the soil organic matter genesis and alteration under the influence of tidal processes in coastal permafrost-affected soils as well as to obtain the previously unknown characteristics of the structural and elemental composition of different fractions of organic matter. The elemental composition and 13C NMR spectroscopy of humic acids were analyzed. It was revealed that humic acids extracted from the studied marsh soils accumulate up to 50% C and 4% N. Active processes of dehydrogenation are noted in HAs molecules, which indicates a relatively low degree of aliphatic structure development. According to 13C NMR spectroscopy, it was revealed that up to 45% of aromatic structural fragments accumulate in marsh soils, indicating a relatively high degree of organic matter stabilization and resistance to biodegradation.

Use smaller size of straw to alleviate mercury methylation and accumulation induced by straw incorporation in paddy field

Straw sizes were found to affect the methylmercury (MeHg) accumulation in rice grains induced by straw incorporation. The mechanism behind, however, still remains unclear. Here, we incorporated rice straw in different sizes (powder, 2 cm and 5 cm) into a Hg-contaminated paddy soil. Our results showed that straw sizes regulated the release of different fractions of organic matter (OM) in straw residues and further Hg methylation in paddy soil. The easily degradable OM (EDOM) was a key driving factor that facilitated net Hg methylation, though it only occupied a small fraction (1.12–3.12%) of the soil OM. Powdered straw reduced the duration of net Hg methylation by 74.39% compared to 5 cm straw, resulting in a strong and rapid net Hg methylation in paddy soil before the rice flowering. After the release of EDOM, the humified OM dominated in paddy soil and bound to MeHg, leading to less MeHg being transported to rice grains during the grain filling. Powdered straw decreased MeHg accumulation by 25.32% in the mature rice grains compared with 5 cm straw. Our study suggests that straw powdering before incorporation provides a feasible pathway for reducing MeHg accumulation in rice grains induced by straw incorporation.

Trophic niches and diet shifts of juvenile mullet species coexisting in marine and estuarine habitats

AbstractFood partitioning among coexisting species is often considered advantageous to minimize niche overlap and avoid inter-specific competition. Congeneric fish species such as the mullets Mugil curema and Mugil liza, which co-occur across marine and estuarine habitats, are good models to evaluate resource use and niche overlap or partitioning. We used stomach contents (SCA) and stable isotope analysis (SIA) to assess potential trophic shifts and changes in niche overlap associated with the mullets transitioning from marine to estuarine habitats. SIA included different fractions of organic matter in suspension and in the sediment to estimate the contribution of micro, nano and pico-organisms to the mullets’ diets. We hypothesized higher resource partitioning in the less resource-diverse system (marine surf-zone) than in the more diverse one (estuary). SCA showed diet differences between M. curema and M. liza according to the habitat. They showed distinct diets in the marine area (P &lt; 0.001), but similar diets in the estuary (P = 0.226). A lower niche breadth was observed for both species in the marine area (M. curema = 0.03, M. liza = 0.06) compared with the estuary (M. curema = 0.14, M. liza = 0.16). Isotopic niches of both species were higher in the estuary (64.7%) compared with the marine area (0.7%). These findings corroborated our hypothesis of higher food partitioning in the marine surf-zone. We also demonstrated using SIA the shift from planktonic to benthic feeding following the recruitment of the mullets from the surf-zone into the estuary.

Microscopic and Fractal Characterization of Organic Matter within Lacustrine Shale Reservoirs in the First Member of Cretaceous Qingshankou Formation, Songliao Basin, Northeast China

Understanding the occurrences of different fractions of organic matter in shale reservoirs is very important for the evaluation of shale oil. Lacustrine organic-rich shale samples from the first member of the Cretaceous Qingshankou Formation in the Songliao Basin were analyzed with confocal laser scanning microscopy (CLSM) and fluorescence spectral analysis. The results show that the occurrences of different organic components are related to the fabric of samples and vary with depth. The bulk content of light components is significantly higher than heavy components and exhibits a positive relationship with quartz and feldspar contents. Both light and heavy components are distributed parallel with the lamination in microscopic view in laminated samples, and randomly in massive samples. The maximum radius of light components in most of the samples is larger than 20 µm, while it is smaller for heavy components, indicating the micro fractionation from clay/organic lamina to quartz/feldspar lamina. The depth of enrichment of light components corresponds to the oil maturity of organic matter. Both the distribution of light and heavy components fits the same fractal model, with fractal dimensions ranging between 2.2 and 2.5. The CLSM results confirm that it can be a reliable tool for the “sweet spot” exploration.

Effective biological nitrogen process and nitrous oxide emission characteristics for the treatment of landfill leachate with low carbon-to-nitrogen ratio

Biological nitrogen removal via nitrite has been applied extensively to treat low chemical oxygen demand to nitrogen (COD/N) ratio wastewater, e.g. landfill leachate. It is known that landfill leachate has a very complex organic and nutrients profile. During the treatment, the transformation behavior of organic pollutants and nitrogen, as well as the side-product of nitrous oxide (N2O) emission in this process has not been fully explored. In this study, a typical integrated anoxic-aerobic (low dissolved oxygen (0.1–1.0 mg O2 L−1)) process with sludge recirculation was employed for landfill leachate treatment. Results show that most of low molecular weight acids, building blocks and low molecular weight neutrals can be removed in the anoxic unit due to denitrification. A total nitrogen removal efficiency up to 84% was achieved with influent COD/N ratio of about 4.5, while the overall N2O emission was 2.8 ± 0.5% of the incoming nitrogen load. It was found that N2O emission was negligible from anoxic unit under COD/(NO2−-N + NO3−-N) ratio of 5.51 ± 0.83. However, reduced COD/(NO2−-N + NO3−-N) ratio in the anoxic unit caused enhanced N2O emission where nitrite accumulation was also observed. When COD/(NO2−-N + NO3−-N) ratio in the anoxic unit was decreased to 2.66 ± 0.76 and 1.39 ± 0.19, N2O emission in the process increased to 5.6 ± 1.8% and 9.5 ± 1.6% of incoming nitrogen load, respectively. Quantification of functional genes suggests that N2O emission was negatively correlated to the abundance of nirS, nosZ genes and nosZ/narG ratio, highlighting the role of effective denitrification potential and more N2O-consuming bacteria in lowering N2O emissions. This study shed light on conversion of different fractions of organic matter in the landfill leachate treatment, and provided strategies to minimize N2O emission.

Adsorption characteristics of oxytetracycline by different fractions of organic matter in sedimentary soil.

Sedimentary soil was selected as the original sample (SOS). The adsorption fractions were obtained by the removal of dissolved organic matter (SRDOM), removal of minerals (SRM), removal of free fat (SRLF), and removal of nonhydrolyzable organic carbon (SNHC) respectively to investigate the adsorption characteristic of oxytetracycline (OTC) by different fractions of organic matter in sedimentary soil. The adsorption mechanism was investigated by elemental analysis, infrared spectra, and UV-visible spectroscopy. The results showed that the DOM in the sedimentary soil inhibited the adsorption of OTC, but the adsorption of different fractions of organic matter was quite different. The sorption kinetics of OTC were fitted to the pseudo-second-order model and the adsorption capacity of each fraction was: SNHC≈SRDOM > SOS > SRLF> SRM. The adsorption processes of OTC by different fractions were spontaneous. Alkaline pH condition had an effect on the adsorption of four fractions except for SNHC, while neutral and acidic pH affects SOS and SRDOM more obviously, the SNHC fraction was almost free from pH varies. Mechanism analysis showed that the main factors determining the adsorption capacity were the aromaticity and polarity of organic matter fractions. For the organic matter-based fractions (SRM, SRLF, and SNHC), the adsorption coefficient was positively correlated with the aromaticity. Furthermore, for SOS and SRDOM based on inorganic minerals, it was not only related to aromaticity, but also the content and composition of inorganic minerals.

Molecular and isotopic evaluation of the maturation history of the organic matter in an Ordovician aquiclude (Michigan Basin): Evidence for late diagenetic biodegradation

Previous characterization of a low permeability (10−16 ≤ Kh ≤ 10−12 m s−1) and high salinity (> 5 M of Cl−, > 10× seawater salinity) aquiclude, in Upper Ordovician-aged sediments situated on the eastern flank of the Michigan Basin, where a deep geological repository for low and intermediate level nuclear waste is proposed, suggested a microbial origin for CH4 and CO2 based on their stable isotope values. CH4 is believed to have been produced and trapped during the Paleozoic in a relatively discrete and high organic matter (OM) horizon at the shale/carbonate transition. To further investigate the efficiency of confinement of this aquiclude, here we present detailed isotopic and geochemical stratigraphic profiles of OM and biomarkers, with the objective of understanding the origin of CH4 and its relative timing of confinement. Classical diagnostic ratios of polycyclic aromatic hydrocarbons, relative abundances of hopanes and degraded hopanes coupled to dual compound-specific isotopic analysis of n-alkanes, as well as δ13C analysis on different fractions of OM were measured. A partitioning of the Ordovician sedimentary succession into two systems is observed with an upper system that is self-sourced and confined, hosting the microbially derived CH4 with evidence of late diagenetic OM biodegradation and a lower system that reveals later secondary oil migration which has overprinted the organic geochemical record. We propose a conceptual model that would explain the generation and preservation of this paleo-bioreactor over time using the maturation history reconstruction derived from this dataset. This work not only provides essential field empirical evidence of a relationship between methanogenesis and late diagenetic biodegradation, but also shows the power of dual-compound-specific isotope analyses in deciphering between different maturation processes affecting OM in natural subsurface settings.

Do all fractions of organic matter contribute equally in shale porosity? A case study from Upper Ordovician Utica Shale, southern Quebec, Canada

In many unconventional hydrocarbon systems, organic matter (OM) substantially contributes to total porosity of the rock that led to a positive correlation between total organic carbon (TOC) and porosity. While organic porosity is an important reservoir property of unconventional hydrocarbon systems, TOC of these rocks consists of different macerals or petrographic fractions. These TOC fractions can be geochemically divided and quantified by the revised, extended slow heating (ESH) Rock-Eval analysis. This study discusses the contribution of different fractions of OM on porosity variation in the mature to overmature Utica Shale in southern Quebec, using ESH Rock-Eval analysis, helium pycnometery, scanning electron microscopy (SEM), and X-ray diffraction (XRD) mineralogy. Selected samples from three wells at depths of ∼400, 700, and 2000 m, covering a range of thermal maturity from late peak oil window (VRoeqv. ∼1%) to dry gas zone (VRoeqv. ∼2.1%) were analyzed in this study. The predominant OM constituents are solid bitumen, chitinozoans, and minor graptolites with mean TOC of 1.1 ± 0.4 wt. %. The mean porosity for oil and gas window samples decreases with depth from 3.9 ± 0.9 to 2.6 ± 0.5%, respectively. The SEM images reveal that organic porosity is limited to pores developed in solid bitumen, while regardless of thermal maturity, chitinozoans have a non-porous structure throughout the oil to dry gas window. This observation suggests that the impact of thermal maturity on porosity is different for different OM fractions (i.e., macerals), leading to different contribution of OM fractions to total porosity. The latter conclusion is further supported by the improved correlation observed between the solid bitumen fraction and porosity compared to TOC-porosity correlation for oil window samples. Our entire data set suggests that OM (i.e., bitumen fraction), especially in the dry gas window, is not the major controlling factor on the total porosity in the Utica Shale, whereas, intergranular porosity has the dominant control on total porosity. This observation suggests that the hydrocarbon storage potential may largely reside in inorganic pores rather than organic pores in the analyzed intervals of the Utica Shale. The decrease in total porosity observed from shallower samples (i.e., oil window) to deeper samples (i.e., dry gas window) also suggests that intergranular porosity is the dominant porosity component, which decreases with burial.

Long-Term Effect of Fertilizers and Amendments on Different Fractions of Organic Matter in an Acid Alfisol

ABSTRACTThe effect of fertilizers and amendments on organic matter dynamics in an acid Alfisol was studied in a long-term field experiment initiated during 1972 at experimental farm of Department of Soil Science, CSK HPKV, Palampur (India). Continuous application of chemical fertilizers either alone or in combination with farmyard manure (FYM) or lime for 42 years significantly influenced water-soluble organic carbon (WS-OC), water-soluble carbohydrate (WS-CHO), soil microbial biomass carbon, soil microbial biomass nitrogen, soil microbial biomass phosphorus, soil microbial biomass sulfur, humic acid (HA), and fulvic acid (FA). Continuous cropping without fertilization resulted in depletion to the order of 17, 21, 24, 23, 22, 26, 12, and 18% in WS-OC, WS-CHO, microbial biomass carbon, microbial biomass nitrogen, microbial biomass phosphorus, microbial biomass sulfur, HA, and FA, respectively. Different fractions of soil organic matter were found to be positively and significantly correlated with grain and straw/stover yield of wheat and maize crops.

Evaluation of different fractions of the organic matter of peat on tetracycline retention in environmental conditions: in vitro studies

Due to the modernization of the agro-industrial sector, compounds with different toxicity and effects on human health and animal have been used and consequently affecting the environment. Among them, tetracycline (TC) stands out as one of the antibiotics most commonly used worldwide. This study evaluated the TC interaction with different fractions of peat in natura and humic substances, humic acid, fulvic acid, and humin. The different fractions of the organic matter were characterized by organic matter content, elemental analysis, spectroscopic analysis (E4/E6), and nuclear magnetic resonance of carbon 13 (NMR 13C), and the interaction between TC and different fractions of organic matter was made by fluorescence spectrometry. We used the tangential ultra-filtration system for determining the complexation capability of humic substances (HSs), fulvic acids (FA), humic acids (HA), and humin (HUM) from peat with TC. Finally, we evaluated sorption kinetic experiments between TC and peat in natura. The peat samples, humic substances, FAs, HAs, and HUM were characterized by organic matter (OM), atomic ratio (H/C and C/O) calculated from elemental analysis data, functional groups quantified by NMR 13C data, and E4/E6 ratio, and the results show significant differences in the structural characteristics of the fractions of OM influenced by the type of microorganisms and environmental factors associated with this decomposition. Data analysis revealed the strongest interaction between HUM and TC (59.19 mg g−1), followed by interaction between HS and TC (43.36 mg g−1 HS). In the sorption studies, these conditions showed the best model to describe the system under consideration using the Freundlich model. The results showed that the different fractions of the OM extracted from peat show different contributions that affect the bioavailability of contaminants to the environment.

Effects of organic and mineral matter on reservoir quality in a Middle Triassic mudstone in the Canadian Arctic

This study examines the hydrocarbon potential of the Middle Triassic Murray Harbour Formation (Sverdrup Basin, Arctic Canada) as a self-sourced reservoir. The Murray Harbour Formation consists of organic-rich mudstone and siltstone which has contributed oil and gas to the majority of known hydrocarbon fields in the basin. Organic matter (OM) and mineral fractions of the interval are investigated to characterize the effect that each fraction has on reservoir quality. The interval of interest is within the oil generation window, with a Tmax of 443°C and total organic carbon (TOC) value of 3.20wt.% (median, n=51). A modified method of Rock-Eval analysis, referred to as the extended slow heating (ESH) cycle, where heating occurs at a slower rate of 10°C per minute up to 650°C, was utilized to better resolve different fractions of OM. In conjunction with organic petrology, this allowed correct identification of the components of TOC and the effects each has on reservoir quality and hydrocarbon potential for the unit.Three main OM fractions are identified: i) light free hydrocarbons, ii) medium to heavy fluid-like hydrocarbon residue (FHR), and iii) kerogen and solid bitumen. The kerogen (allo- and autochthonous) and solid bitumen fraction, which is dominated by solid bitumen, occurs in two petrographically observable forms: matrix and lump solid bitumen. Matrix bitumen is primarily disseminated within the clay-rich matrix and fills smaller pores, whereas lump solid bitumen fills larger pores. TOC has a negative correlation with porosity indicating that it occupies pore space, with a detrimental effect on hydrocarbon storage and flow at the present level of thermal maturity. However, thermally overmature areas of the Murray Harbour Formation may have increased microporosity within the solid bitumen network which could provide additional adsorption sites for generated gas within the reservoir. Macro- and micro-scopic phosphate nodules (likely high-density apatite mineral) appear throughout the interval, and under fluorescence microscopy, are observed to retain light free hydrocarbons and FHR. A strong positive correlation between porosity and grain density suggests that these nodules contribute to porosity and provide capacity for hydrocarbon storage within the rock. This important observation can be applied to other phosphate-rich mudrock plays, including the coeval Doig Formation Phosphate Zone in the established Alberta Basin, to potentially identify and exploit prolific zones.

Organic matter in a dystroferric Red Latossol under no-tillage

Soils of the Cerrado have chemical, physical, and biological limitations for agriculture, which, associated with climate factors, contribute to their impoverishment. The maintenance and accumulation of soil organic matter are considered the best option of addressing this problem and to ensure a sustainable production. The purpose of this study was to evaluate different fractions of organic matter, and carbon and nitrogen contained in these compartments of a very clayey dystroferric Red Latossol under different crop rotations and at different depths under long-term no-tillage in Dourados, state of Mato Grosso do Sul. The experiment was arranged in a randomized block design with three replications, and the treatments in a 5x4 factorial design, with five crop rotation systems (1 – vetch + oat + oilseed radish/ soybean/ radish/ maize/ vetch + oats + radish/ soybean; 2 – sunflower/ soybean/ vetch + oat + radish/ maize/ sunflower/ soybean; 3 – oat/ soybean/ sunflower/ maize/ oat/ soybean; 4 – vetch + oat/ soybean/ brachiaria/ maize/ brachiaria/ soybean; 5 – vetch/soybean/vetch/maize/vetch/soybean), in four soil layers (0-5, 5-10, 10-15, 15-20 cm). Particle size was analyzed to determine the particulate fraction of organic matter (POM), and carbon (C-POM) and nitrogen (N-POM) in it. It was concluded that the levels and stock of C-POM, and nitrogen contents in the soil are not influenced by the different crop rotation systems. Crop rotation 4 increased the levels and stock of total organic carbon (TOC), carbon associated with soil minerals (C-MOM) and the total C/N ratio and total C/N ratio associated with soil minerals. The highest levels of TOC, C-POM, C-MOM, total nitrogen, N-POM and nitrogen associated with soil minerals (N-MOM) were found in the 0-5cm layer.

Ti-salt flocculation for dissolved organic matter removal in seawater

In this study, the removal of different fractions of organic matter in seawater was investigated using titanium tetrachloride (TiCl4) flocculation and compared with ferric chloride (FeCl3) flocculation. The organic matter fractions were characterised using liquid chromatography–organic carbon detector (LC–OCD). Results showed the hydrophobic compounds removal was dominant by both flocculants. However, the removal of hydrophilic organic compounds, such as humics and low-molecular weight neutral compounds of seawater, was superior by TiCl4 flocculation compared to FeCl3 flocculation and this removal increased considerably with the increase of TiCl4 doses. The flocculated sludge after TiCl4 flocculation was incinerated to produce titanium dioxide (TiO2) nanoparticle. TiO2 from seawater sludge characterised by X-ray diffraction (XRD) and scanning electron microscope/energy-dispersive X-ray spectroscopy (SEM/EDS) showed predominant anatase phase with Si as a main dopant.

Ceramic membrane as a pretreatment for reverse osmosis: interaction between marine organic matter and metal oxides

Scaling and (bio)fouling phenomena can severely alter the performance of the reverse osmosis process during desalination of seawater. Pretreatments must be applied to efficiently remove particles, colloids, and also precursors of the organic fouling and biofouling. Ceramic membranes offer a lot of advantages for micro and ultrafiltration pretreatments because their initial properties can be recovered using more severe cleaning procedure. The study focuses on the interaction between metal oxides and marine organic matter. Experiments were performed at laboratory scale. The first series of experiments focus on the filtration of different fractions of natural organic matter and model compounds solutions on flat disk ceramic membranes (47 mm of diameter) characterized with different pore size and composition. Direct filtration experiments were conducted at 0.7 bar or 2 bars and at room temperature (20 ± 0.5°C). The efficiency of backflush and alkaline cleaning were evaluated. The second series of experiments were carried out with metal oxide particles of the same composition than the disk ceramic membranes. Isotherm adsorption and adsorption kinetics of different fractions of organic matter with different concentration and physico-chemical characteristics were studied (pH, temperature, and ionic strength). Metal oxides studied are aluminum, zirconium, and titanium oxides. Each metal oxide corresponds to a specific pore size for the disk ceramic membranes: 80, 60, and 30 nm. Different sizes of metal oxide particles are used to measure the impact of the surface area on the adsorption of the organic matter. Seawaters from the Arabian Gulf and from the Red Sea were collected during algal blooms. Cultures of algae were also performed in the laboratory and in cooperation with woods hole oceanographic institute. Solutions of algal exudates were obtained after a couple of weeks of cultivation followed by sonication. Solutions were successively filtered through GFF (0.7 μm) and 0.45μm membrane filters before use. The dissolved organic carbon (DOC) concentration of final solution was between 1 and 4 mg/L and showed strong hydrophilic character. These various solutions were prepared with the objective to mimic the dissolved organic matter composition of seawater subjected to algal bloom. Characterization of the solutions of filtration experiments (feed water, permeate water, and backwashes) and batch experiments (raw solution and supernatant solutions) included fluorescence, UV, total organic carbon, total nitrogen, and Liquid Chromatography – Organic Carbon Detection measurements. In comparison to seawater under normal condition, seawaters collected during algal bloom and algal exudates solutions led to very severe fouling of all ceramic membranes (with some DOC removal of 10–20%). It is important to indicate that algal exudate permeates still exert fouling properties when filtered through similar new (virgin) membrane. These results indicate that both size exclusion and adsorption phenomena occur (on surface, inside pores). In all cases, the backflush (performed with MilliQ [MQ]) showed minor or no effect and the cleaning backwash was not able to recover the initial flux (30–60%). Analyses performed on the backflush solution (performed with MQ) and on the alkaline cleaning solution revealed the retention of both high and low molecular organics on the different metal oxides. Unfortunately, analyses of membrane surface using imaging various tools are not providing informative results in term of foulant/adsorbed material composition.

Cellulase and xylanase activity during the decomposition of three aquatic macrophytes in a tropical oxbow lagoon

Due to the connection between enzymatic activity and degradation of different fractions of organic matter, enzyme assays can be used to estimate degradation rates of particulate and dissolved organic carbon in freshwater systems. The aim of this study was to quantify and model the enzymatic degradation involving the decomposition of macrophytes, describing temporal activity of cellulases (EC 3.2.1.4 and EC 3.2.1.91) and xylanase (EC 3.2.1.8) during in situ decomposition of three aquatic macrophytes (Salvinia sp., Eichhornia azurea and Cyperus giganteus) on the surface and water-sediment interface (w-s interface) of an oxbow lagoon (Óleo lagoon) within a natural Brazilian Savanna Reserve. Overall, the enzymatic degradation of aquatic macrophytes in Óleo lagoon occurred during the whole year and was initiated together with leaching. Xylanase production was ca. 5 times higher than cellulase values due to easy access to this compound by cellulolytic microorganisms. Enzymatic production and detritus mass decay were similar on the surface and w-s interface. Salvinia sp. was the most recalcitrant detritus, with low mass decay and enzymatic activity. E. azurea and C. giganteus decomposition rates and enzymatic production were high and similar. Due to the physicochemical homogeneity observed in the Óleo lagoon, the differences between the decay rates of each species are mostly related with detritus chemical quality.

Applications of stable isotope ratio mass spectrometry in cattle dung carbon cycling studies

Understanding the fate of dung carbon (C) in soils is challenging due to the ubiquitous presence of the plant-derived organic matter (OM), the source material from which both dung-derived OM and soil organic matter (SOM) predominantly originate. A better understanding of the fate of specific components of this substantial source of OM, and thereby its contribution to C cycling in terrestrial ecosystems, can only be achieved through the use of labelled dung treatments. In this short review, we consider analytical approaches using bulk and compound-specific stable carbon isotope analysis that have been utilised to explore the fate of dung-derived C in soils. Bulk stable carbon isotope analyses are now used routinely to explore OM matter cycling in soils, and have shown that up to 20% of applied dung C may be incorporated into the surface soil horizons several weeks after application, with up to 8% remaining in the soil profile after one year. However, whole soil delta(13)C values represent the average of a wide range of organic components with varying delta(13)C values and mean residence times in soils. Several stable (13)C isotope ratio mass spectrometric methods have been developed to qualify and quantify different fractions of OM in soils and other complex matrices. In particular, thermogravimetry-differential scanning calorimetry-isotope ratio mass spectrometry (TG-DSC-IRMS) and gas chromatography-combustion-IRMS (GC-C-IRMS) analyses have been applied to determine the incorporation and turnover of polymeric plant cell wall materials from C(4) dung into C(3) grassland soils using natural abundance (13)C isotope labelling. Both approaches showed that fluxes of C derived from polysaccharides, i.e. as cellulose or monosaccharide components, were more similar to the behaviour of bulk dung C in soil than lignin. However, lignin and its 4-hydroxypropanoid monomers were unexpectedly dynamic in soil. These findings provide further evidence for emerging themes in biogeochemical investigations of soil OM dynamics that challenge perceived concepts of recalcitrance of C pools in soils, which may have profound implications for the assessment of the potential of agricultural soils to influence terrestrial C sinks.

Canopy herbivory altering C to N ratios and soil input patterns of different organic matter fractions in a Scots pine forest

Herbivorous insects can affect ecological processes in forested ecosystems such as nutrient and matter cycling especially during outbreak situations. However, the knowledge about their contribution to the quality and flows of energy and matter in forests is still imperfect. In this paper we report on the herbivore-affected C to N ratios in different fractions of organic matter cascading from the canopy to the forest floor during a pine lappet (Dendrolimus pini L.) mass infestation. Throughout a four months period we monitored the C and N fluxes with throughfall, and the C/N ratios of insect excrements (faeces) and pine needles in an 80-year-old Scots pine forest. Compared to the control, herbivore defoliation significantly magnifies C and N input fluxes by two to three times amounting to 95 kg TOC and 5.9 kg TN ha−1 in addition. Concurrently NO3-N fluxes diminished and the C/N ratios in throughfall solutions increased during peaking frass activity. Compared to fresh needle biomass, the C/N ratios in insect faeces triple during peaking frass activity resulting in values between 70 and 100. This study demonstrates the importance of herbivorous insect’s pests on element cycling as they act as a short-time phenomenon altering the nutrient quality and quantity reaching the forest floor and potentially affecting below-ground processes.

Characterization of the Different Organic Matter Fractions of Spent Mushroom Substrate

Spent mushroom substrate (SMS) has been employed in recent years for different applications. However, most of these applications have been unable to solve the problem of its disposal completely, except its agricultural use. Because of this, it is important to identify the variability in the organic composition of SMS to evaluate its capacity as a soil amendment. Therefore, a study was carried out involving the analysis of different organic matter (OM) fractions in the two types of SMS obtained from 19 mushroom industries in Spain. In this experiment, 40 different types of SMS [19 spent substrates of Agaricus bisporus (SMS‐AB) and 21 spent substrates of Pleurotus (SMS‐P)] were evaluated for OM; soluble polyphenols; organic nitrogen (Norg); total organic carbon (Corg); water‐soluble carbon (Cw); cation exchange capacity (CEC); Corg/Nt, Cw/Norg, and CEC/Corg ratios; humic acid‐like carbon (Cha); fulvic acid‐like carbon (Cfa); 0.1 M sodium hydroxide (NaOH)–extractable organic carbon (Cex); humification ratio (HR) (Cex / Corg × 100); humification index (HI) (Cha / Corg × 100), percentage of humic acid–like carbon (Pha) (Cha / Cex × 100) and Cha/Cfa ratio. In comparison with the limits set by the Spanish legislation for organic fertilizers, SMS‐AB and SMS‐P had suitable and high Corg/Nt ratios, respectively, and both of them showed high OM contents. The study of the different fractions of OM showed that SMS‐P had higher contents of Corg, Cw, and soluble polyphenols than SMS‐AB. However, the fraction of organic N was significantly higher in SMS‐AB than in SMS‐P. The study also showed that only SMS‐AB had a percentage of humic acid–like C greater than that of the fulvic acid–like C. Moreover, in most cases, the values of the humification parameters of this waste were higher than those of SMS‐P, indicating a greater OM humification in the SMS‐AB compared to SMS‐P. Regarding the parameters related to the OM stability and its maturity, it has been observed that only SMS‐AB had values of these parameters higher or close to the established limits for mature organic materials. The origin influenced in the parameters related to OM (OM, Corg, Norg, and Cw) in SMS‐AB, whereas SMS‐P only showed significant differences in the humification parameters (Cex, Cha, HR, HI, Pha, CEC, and Cha/Cfa and CEC/Corg ratios) related to the origin. The heterogeneity in OM composition of the studied SMS did not allow the formulation of simple equations for the complete evaluation of the composition of these wastes from easily determined parameters.