Organic Matter Fractions Research Articles

Превращения урацила , глицина и глюкозы, поступающих в составе опада в лесную подстилку дерново-подзолистой почвы

In model experiments under forest ecosystem conditions, samples of partially decomposed forest litter and soil from a 0–10 cm layer containing 14C-labeled organic matter were selected. The label was introduced in the form of low molecular weight water-soluble organic substances of individual nature – glycine, uracil and glucose together with unlabelled plant litter in nylon bags. The experiment was carried out in the late autumn period on the territory of the Malinsky forestry, 20 km south-west of Moscow, on a medium loamy sod-podzolic soil. For the study, samples were taken from two selection periods – 40 days after labelling and after two years. The selected samples were extracted and separated into soil organic matter fractions containing 14C in their composition, followed by radiometry. The results showed differences in the transformation and incorporation of radiocarbon of the studied products – glycine, uracil, and glucose into different fractions of soil organic matter of low molecular weight water-soluble substances, depending on their nature.

Pores distribution influences the soil microorganism's response to changes in temperature and moisture

Microorganisms are an essential fraction of soil organic matter, which presence and activity depend directly on soil physical conditions. This study aimed to address the effect of soil temperature and moisture under contrasting macroporosity conditions on soil biological properties. Soil physical-chemical characterization implicated the collection of composite samples and undisturbed surface soil samples (0 to 10 cm). Also, samples of undisturbed surface soil were extracted in 40 polyvinyl chloride cylinders of 18 cm diameter and 20 cm height for the arrangement of soil mesocosm as the experimental units of a completely randomized experiment with a 2x2x3 factorial arrangement. The experiment duration was 21 days, and the soil biological properties measured were microbial biomass (MB) and soil respiration (SR). Macroporosity showed a significant effect on MB, which indicates that aeration pore influences the number of microorganisms in the soil; for the SR, the macroporosity had a not significant effect. The temperature at the ranges established in the experiment did not significantly affect MB, whereas a highly significant effect of temperature over SR was observed. A highly significant effect of soil moisture was observed on MB and SR. Macroporosity, moisture, and temperature are determining factors in the presence of soil microorganisms, both directly and through the interaction between them. Herein the microorganisms have a wide range of thermal adaptation, and the effect of soil temperature can boost soil microorganisms. In turn, it was observed that the microorganisms present are significantly sensitive to the moisture deficit in soil.

Impact of deforestation on the soil physical and chemical attributes, and humic fraction of organic matter in dry environments in Brazil

Deforestation of Caatinga and inadequate land use of these dry environments have impacted soil quality in Northeastern Brazil. The objectives of this study were: (a) to evaluate the effect of deforestation and different agricultural uses on the physical and chemical properties of soil, and humic fractions of soil organic matter in dry environments; and (b) to detect the soil properties that were most affected by anthropic actions. We evaluated four dry areas in Chapada do Araripe, NE Brazil: preserved native vegetation; degraded native vegetation; cassava conventional cultivation; and eucalyptus agro-energy cultivation. Soil fertility, total organic carbon and humic fractions of soil organic matter were lower in the degraded native vegetation area. The best indicators for soil quality evaluation were: macroporosity; bulk density; soil resistance penetration; sum of bases (mainly Ca2+); available P; and saturation by Al3+. Total organic carbon and humic acid fractions of soil organic matter were important in improving soil quality. These properties were influenced by deforestation and agricultural uses, suggesting that the deforestation of native vegetation in dry environments has high capacity to degrade the soil, preventing its regeneration.

Explore variations of DOM components in different landcover areas of riparian zone by EEM-PARAFAC and partial least squares structural equation model

Dissolved organic matter (DOM) plays key roles in species-distribution of contaminants and the biogeochemical cycle of carbon in ecosystems. Riparian zone is the representative of water-land ecotone and controls the DOM exchange between water and land. However, the variance of DOM in different landcover areas of an urban river riparian zone is unknown. In this study, fluorescence excitation-emission matrix (EEM) spectroscopy coupled with parallel factor analysis (PARAFAC) and partial least squares structural equation model (PLS-SEM) was applied to character dissolved organic matter (DOM) fractions in four types of landcover riparian areas (natural forest, artificial forest, semi-natural grassland, and cropland) of Puhe River and trace latent factors. Soil samples were collected at 0–20 cm, 20–40 cm, 40–60 cm, and 60–80 cm. The results showed that soil DOM components and humification varied between forests with grassland and cropland samples, and soil humification was obviously higher in the forest samples than that in the grassland and cropland samples. In the natural and artificial forest soils, the humic/fulvic-like were the dominant fractions of DOM, whose variations were smaller than the protein-like with soil depths. However, the tyrosine-like was the representative component in the grassland and cropland soils, whose variation was smaller than the humus substances. According to the PLS-SEM, the DOM components and humification were affected by soil physiochemical properties and DOM sources. The humification in the forest soils had a positive correlation with tryptophan-like, which derived from blended source of the autochthonous and terrigenous. Nevertheless, a positive correlation was observed between humification and humus substances, which could derive from microbial degradation of tyrosine-like, in the grassland and cropland soils. Moreover, the soil physiochemical properties were negatively related to DOM components in all soil samples, which could affect indirectly soil humification. Therefore, EEM combined with PARAFAC and PLS-SEM might be an effective method to investigate DOM fractions and trace the latent factors in different landcover areas of the riparian zone.

Soil aggregation and associated organic matter under management systems in sandy-textured soils, subtropical region of Brazil.

Increasing the diversity of plant species in agricultural production areas favors the maintenance or improvement of soil quality, particularly for soils with a sandy texture. This beneficial effect is related to the formation of aggregates of different origins. This study aimed to (i) verify whether soil use and management affect the proportion of biogenic (Bio) and physicogenic (Phy) aggregates and (ii) verify whether biogenic aggregation is more likely to lead to soil improvement than physicogenic aggregation. Three management systems were evaluated (permanent pasture, PP; no-tillage system, NT; and no-tillage + Brachiaria system, NT + B) as well as a reference area (Atlantic Forest biome vegetation, NF). According to their origin or formation pathway, the aggregates were separated, identified, and classified as Bio (formed by biological processes) and Phy (resulting from chemical and physical actions). The differentiation between Bio and Phy aggregates was performed based on the visualization of morphological features, such as shape, size, presence of roots, porosity, and subunit arrangements, and junctions. Only the PP area was able to promote greater aggregate formation of biological origin, with greater amounts of Bio aggregates. The highest total organic carbon (TOC) contents and the least negative δ13C values were also quantified in the aggregates of the PP area. The NT + B system provided an increase in the TOC content of its aggregates in comparison with aggregates in the NT and NF areas. Among the formation pathways, the Bio aggregates had the highest TOC and soil organic matter fractions contents and the most negative δ13C values. Perennial forage grasses vegetation was more important than the plant species diversity in favoring Bio aggregate formation. The beneficial effect of Brachiaria can be observed when incorporated as part of intercropping with corn in grain production systems. The biogenic aggregates favored the concentration of more labile soil organic matter fractions. The results of this study can provide important theoretical information for future studies focused on the combination of different plant species in agricultural food production areas on sandy-textured soils.

Enrichment of Organic Acids in Fine Particles Over a Megacity in South China

AbstractOrganic acids are abundant aerosol components that impact the hygroscopicity and multiphase processes of particulate matter, yet their changing compositions and sources are poorly understood. In this study, filter‐based PM2.5 samples were collected concurrently at three sites (urban, rural, and coastal) during the summer and winter of 2018 in the megacity Guangzhou, south China, to determine organic acids including C9–C32 fatty acids, C4–C10 dicarboxylic acids, and aromatic acids. On average, the total concentrations of the speciated organic acids were higher in winter than in summer, and were the highest at the urban site. Compared to observations at the same sites in winter 2009, average concentrations of organic acids in winter 2018 increased by 35.0%, 66.0%, and −3.2% at the urban, rural and coastal sites, while their fractions in organic matter (OM) increased by approximately 261.5%, 266.7%, and 61.1%, and their fractions in PM2.5 increased by approximately 318.2%, 308.7%, and 221.1%, respectively. Source apportionment of organic acids revealed that cooking emission and vehicle exhaust were the major sources at the urban site, plant wax and vehicle exhaust were the two largest sources at the rural site with substantial contributions from biomass burning in winter, while vehicle exhaust and ship emission were the two major sources at the coastal site. Less contributions from secondary production were retrieved in winter 2018 than in winter 2009, and the enrichment of organic acids in PM2.5 or OM was attributed to their elevated primary emissions from vehicles and ships, cooking, and plant wax.

The effect of organic matter fraction extracted on micropores development degree and CH4 adsorption capacity of coal

The percentage of micropores in the pore structure of coal plays a significant role in methane (CH4) adsorption, whereas the fraction of organic matter in coal has a positive effect on CH4 adsorption. Ultrasonic waves were used to excite mixtures of organic solvents and coals with different degrees of deterioration. This process facilitates the induction of surface organic matter in coal and the shedding of non-closed-ring side chains in the main structure of coal and the opening of closed rings. The samples extracted by organic solvents were subjected to electron microscopy detection, elemental analysis, and functional group analysis. The porosity of the samples showed distinct changes, and the sample with the best organic solvent extraction effect showed a sharp decrease in organic main carbon and a change in the distribution of partial functional group peaks. Through the experimental results of CH4, N2, and CO2 adsorption, the physical adsorption theory and density flooding theory with micropore filling theory were combined. It was found that the CH4 adsorption decreased, macro-and mesopore channels developed, and the percentage of micropores decreased. Overall, the filling effect caused by microchemistry had a significant influence on the macroscopic physical adsorption. Our research results provide theoretical guidance and a reference for the efficient exploitation of coalbed methane and mine gas control.

Kinetics and mineralization fraction of organic matter from sewage sludge mixed with soil under controlled laboratory conditions

The objective of this work was to evaluate the kinetics and mineralization fraction of organic matter from sewage sludge mixed with the soil under controlled laboratory conditions. For this, organic material samples accumulated in layers 0–5 cm, 5–10 cm and 10–15 cm in relation to the surface of a vertical flow constructed wetland system (VF-CW) used for treatment of septic tank sludge, in addition to samples of dewatered sludge from a septic tank and a UASB reactor and non-dewatered sludge from an anaerobic digester were mixed with material collected from the surface layer of a Red Yellow Argisol at rates equivalent to the applications, via organic residues, of 300 and 600 kg ha−1 year−1 of total nitrogen. It was found that the two-phase kinetic equation fit better to the mineralization data of labile and recalcitrant organic carbon. For the lowest nitrogen application rate in the mixtures, the mineralization fractions of the total organic carbon were higher than 73%, while at the highest dose there was a reduction in the mineralization of organic matter by 17% and 63%, respectively in samples collected in layer 10–15 cm from the VF-CW and in the septic tank sludge dewatered in the drying bed.

Soil Strength and Structural Stability Are Mediated by Soil Organic Matter Composition in Agricultural Expansion Areas of the Brazilian Cerrado Biome

A growing demand for resources has led to the expansion of agricultural areas worldwide. However, land conversion associated with poor soil management might lead to soil physical degradation. We investigated the effects of land conversion on soil physical properties in the Brazilian Cerrado region, under native Cerrado vegetation (NV)—pasture (PA) and NV—cropland (CL) conversion scenarios. Soil physical properties related to compaction, pore size distribution, and structure stability were assessed up to a 30 cm depth. Additionally, carbon levels of soil organic matter fractions (particulate and mineral-associated organic matter) were determined. Our results indicate that the compaction process equivalently reduced the soil porosity in PA and CL. However, soil penetration resistance was higher in PA (~2.5 MPa) than in CL (~1.5 MPa), as well as the stable mean weight diameter of soil aggregates. The highest total and labile organic carbon levels were observed in CL, while the lowest levels of total and labile organic carbon occurred in PA (smaller than in CL). These results suggest that the higher structural stability found in PA was mediated by the predominance of stabilized carbon (a decrease in the proportion of soil labile carbon), causing the gaining of soil strength under negligible soil volume variation (in comparison with CL). Our results suggest that the reduction in the soil porosity by compaction due to PA and CL uses can equivalently reduce macropore space and soil hydraulic functioning, and that soil carbon quality alterations (i.e., labile vs. stabilized fractions) are responsible for the gain in soil strength in long-term degraded PA areas. Future research should focus on understanding the magnitude in which soil organic matter controls soil physical attributes, such as soil strength in these expansion areas, and whether this gain in soil strength limits plant development and compromises productivity in the long term.

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.

Variations in the concentration, composition, and sources of WEOM in erosion and deposition landscapes over an erosion intensity gradient on the Loess Plateau of China

Water-extractable organic matter (WEOM) is the most active and mobile fraction of soil organic matter and responds sensitively to soil erosion. However, previous studies on the chemical nature of WEOM in the erosion and deposition landscapes were controversial at site-level studies and mainly focused on surface soils, limiting our assessment of WEOM’s environmental fate at larger and deeper scales. Here, we collected eroded soils and deposited sediments from a depth of 0–200 cm in five eroding catchments with an erosion intensity gradient across the Loess Plateau. We examined the concentration, composition, and potential sources of WEOM using UV–visible absorption and fluorescence excitation-emission matrix-parallel factor analysis. Soil WEOM quantity and quality varied significantly in the erosion and deposition landscapes, with greater variations in soils below 20 cm, where WEOM in the deposition zone was characterized by higher concentration, aromaticity, hydrophobicity, and UVA and UVC humic-like components derived from terrestrial and soil organic matter. WEOM variations in deep soils increased with increasing erosion modulus among sites, and were mainly driven by changes in soil organic carbon concentration, aggregate stability, and carbon to nitrogen ratio. However, the pattern of WEOM parameters between erosion and deposition zones at 0–20 cm was opposite to that in soils below 20 cm. Vegetation inputs compensated the loss of organic matter in sites with suitable climatic status and weak erosion, and led to higher concentrations and exogenous features of WEOM in the surface erosion area. Concludingly, the WEOM concentration, components, and sources differed significantly between erosion and deposition zones, and these differences, as well as their response to erosion intensity, revealed an opposing pattern in surface and deep soils.

A rapid and sensitive assay to quantify amino sugars, neutral sugars and uronic acid necromass biomarkers using pre-column derivatization, ultra-high-performance liquid chromatography and high-resolution mass spectrometry

Microbial necromass comprises a large fraction of soil organic matter (SOM) due to the accumulation and stabilization of microbial residues from dead archaea, bacteria and fungi. Amino sugars, neutral sugars and uronic acids have been used as microbial necromass biomarkers to trace the origin and composition of microbial residues in the SOM pool. Due to the structural complexity of sugars, derivatization reactions and high-throughput analytical methods are required to separate and quantify these sugar-related compounds. Our aim was to develop a rapid and sensitive assay to measure amino sugar, neutral sugar and uronic acid compounds using pre-column 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatization. PMP-derivatives were separated and quantified via reversed phase (RP) ultra-high-performance liquid chromatography (UPLC) coupled to high-resolution Orbitrap mass spectrometry (MS). The method was validated and applied on hydrolyzed peptidoglycans and the biomass of archaeal, bacterial, fungal and plant species, as well as with soils. This developed PMP method allowed the separation and quantification of 18 sugar-related compounds, including four amino sugars, three N-acetyl amino sugars, eight neutral sugars, and three uronic acids within 20 min. This PMP method showed a precision for isotope enrichment detection of 0.03–0.05 atom % 13C for D-glucose and D-glucosamine. This is the first time talosaminuronic acid (deriving from archaeal pseudopeptidoglycan) was identified and quantified using PMP derivatization. The application of this novel PMP method on pure hydrolyzed biomass and soils, showed the successful chromatographic and mass spectrometric separation and quantification of amino sugar, neutral sugar and uronic acid compounds. A multivariate analysis using these sugar-related PMP derivatives showed a clustering of the species according to their respective taxonomic group (archaea, gram-positive bacteria, gram-negative bacteria, fungi and plants). The modified PMP method can be applied to identify and quantify soil microbial necromass biomarkers, as well as their contribution to SOM. The sensitive isotope tracer detection allows tracing isotopically labeled materials into necromass biomarkers in SOM pools.

Agricultural practices influence biological soil quality indicators in an irrigated semiarid agro-ecosystem

A study was conducted to investigate how soil biological measurements can be used to indicate differences in soil quality in arid and semiarid agroecosystems. The objectives were to assess soil biological quality indicators under different land management practices and at different depths and to explore the relationships between soil microbial community and organic matter fractions. Soil samples were collected from three replicates of six land management systems at 0–5 cm and 5–15 cm soil depths. Four management systems had medium to fine soil texture including a permanent grass field with tall fescue (Lolium arundinaceum [Schreb]; TFC), peach orchard with clover understory (Prunus persica with Trifolium repens L.; PCC), alfalfa field (Medicago sativa; ALF) and conventionally tilled soil with an annual crop rotation (CTC). Two management systems, including a young cottonwood tree orchard (Populus fremontii and Populus deltoides; CWS) and conventionally tilled soil in annual crop rotation (CTS), had coarse soil texture. Management systems had significant impacts on most of the soil biological indicators assessed at the two depths with both depths responding similarly to management practices. For the soil biological indicators that showed differences, the TFC generally had the most favorable indicator measurements compared to other management systems. The principal component analysis showed a clear separation between the management systems and microbial communities at both soil depths. The ordination pattern was structured by soil textural differences between medium to fine-textured soils from TFC, PCC, ALF, and CTC fields and coarse-textured soils (CWS, CTS). Spearman’s correlation coefficients (rs) showed that the soil organic matter (rs = 0.85, P = 0.001) and the permanganate oxidizable carbon (rs = 0.93, P = 0.001) were significantly correlated with the total microbial biomass at 0–5 cm soil depth. Also, the soil organic matter (rs = 0.84, P = 0.001) was significantly correlated with the total microbial biomass at 5–15 cm soil depth. This study suggests that in semiarid agroecosystems, management practices with permanent covers have the potential to improve soil quality, and soil texture may also influence the directional changes in soil quality within this region.

Moisture, organic matter, and large particle correction for accurate Pb portable X‐ray fluorescence assessment in urban soils

AbstractThe need for accurate quantification of lead concentrations in urban centers around the world is turning attention towards rapid methods for contamination assessment. Portable X‐ray Fluorescence (pXRF) has been recognized as a more accessible alternative to traditional digestion methods. This study was conducted to produce measurement corrections for in‐situ pXRF measurements conducted on field soils under varying conditions of moisture, organic matter (OM) content, and particle size heterogeneity. Urban forest soils were analyzed for Pb under increasing soil moisture, OM, and coarse fraction contents with two different pXRF and the results were compared to reverse aqua regia digestions. While both instruments showed a strong correlation despite using different calibration methods, correction of pXRF data to digestion values improved accuracy but potentially underestimated Pb concentrations. We propose an empirical correction equation derived from the regression of variance between theoretical and observed concentrations to correct for moisture effects. OM and particle size heterogeneity did not produce a significant effect on Pb measurement and did not warrant correction. Our study confirms other work showing that pXRF provides an accurate and precise alternative to traditional digestion methods for Pb screening, provided that moisture is corrected.

Biological quality and organic matter dynamics in minesoil at 18 years reclamation with perennial grasses

Mining is one of the most destructive economic activities on natural ecosystems. There are around 750 ha impacted by open-pit coal mining in Candiota Mine, the largest in Brazil, with 1.2 billion tons subject to mining. In soils impacted by mining, litter decomposition, always linked to a more extended period of restoration and maintenance of the vegetation, presents positive correlations with the diversity of the edaphic fauna and the enzymatic activity of these areas, promoting improvements in the ecological functions of the new ecosystem. The objective of the present study was to analyze the impact of revegetation with different summer perennial grasses subjected to different mowing managements on the biological and chemical quality of soils after coal mining in an experimental area at the Candiota Mine. Analyzes were performed to identify edaphic organisms using modified Berlese-Tüllgren funnels and microbiological analyzes to quantify Microbial Biomass Carbon (MBC), Microbial Respiration (MR), and urease enzymatic activity. The different fractions of Soil Organic Matter (fulvic, humic acids, and humin) were also quantified to understand the degree of humification in the area. All results were compared in mean tests by Tuckey's test (p < 0.05) and by Principal Component Analysis. After 18 years of revegetation and 11.6 years of mowing management in the area, there was an improvement in MBC and MR compared to the Control, evidencing the positive effect of the perennial grasses used in the experimental area. However, mowing management cannot yet be considered the most promising management for improving edaphic conditions.

Soil organic matter fractions and carbon distribution under different management in Lesotho, southern Africa

AbstractSoil organic matter (SOM) is a complex mixture of multiple fractions of soil organic C (SOC) that can be influenced by management decisions. This study evaluate the effects of tillage (moldboard plow [MP] and no‐tillage [NT]) and commercial fertilizer as limestone ammonium nitrate (28–0–0) at three rates (0 [0‐N], 100 [100‐N], and 200 [200‐N] kg N ha–1) on SOC, soil total N (STN), and SOM fractions (total particulate organic matter‐C [POM‐C] and mineral‐associated organic matter‐C [MAOM‐C]). The study was established in 2008 on the National University of Lesotho Campus Farm, Roma Valley of the Maseru District in Lesotho, southern Africa. The soil classified as Berea series. Soil samples were collected from 0‐to‐5‐, 5‐to‐10‐, 10‐to‐15‐, and 15‐to‐30‐cm depths. Under NT, the SOC, STN, and POM at 0‐to‐15‐cm were 54, 47, and 40% higher than 15‐to‐30‐cm depth, respectively. Differently, 0‐to‐15‐cm the MP had 17, 17, 35% higher SOC, STN, and POM than 15‐to‐30‐cm depth. The SOC in the 0‐to‐15‐cm increased by 27% with MP and by 36% with NT at the 200‐N compared with the 100‐N rate. The highest N‐rate (200‐N) increased total POM by 28.8% for MP and 22.6% for NT than the100‐N rate. The greater increase in POM under MP with high N rate was probably related to the low initial total POM, where small changes in POM will be pronounced, whereas the high total POM in NT could mask the effect the high N rate addition. The coarse and fine POM accounted for 39 and 61%, respectively, of the changes in total POM at both NT and MP. The high percentage of SOC was observed within fine POM fraction (48.4%) in MP, which makes it susceptible to wind erosion, and within MAOM fraction (48.9%) in NT practice. The C/N ratio was highest with coarse POM (C/N ≈ 25) and lowest with MAOM (C/N ≈ 7.2) at both tillage practices. The low C/N ratio made MAOMC vulnerable to microbial decomposition. These findings suggest the need for conservation efforts where conservation tillage and N rates could be used to reduce SOC and POM losses and contribute to improve land sustainability and SOM conservation.

Investigation of electrochemical properties, leachate purification, organic matter characteristics, and microbial diversity in a sludge treatment wetland- microbial fuel cell

Sludge treatment wetland-microbial fuel cell (STW-MFC) is a unique sludge treatment process that produces bioelectricity, but its technology is still in its infancy. This study investigated the electrochemical properties, organic matter characteristics, leachate purification, and microbial community structure of STW-MFCs as affected by electrode location. When electrodes were placed in the filler layer, the STW-MFC system presented a higher power generation capacity (maximum output power density: 0.498 W/m3; peak cell voltage: 0.879 V) and organic matter degradation efficiency. The hydrophilic fraction was the main dissolved organic carbon fraction in sludge extracellular biological organic matter (EBOM) and leachate dissolved organic matter (DOM). Aromatics were mainly concentrated in the hydrophobic acid fraction. The UV-254 content of sludge EBOM decreased mainly in the hydrophilic and transphilic acid fractions. The excitation-emission matrix analysis showed that tryptophan-like protein was more easily eliminated than tyrosine-like protein. In addition, there was a strong correlation between voltage and NH4+ removal efficiency; a negative correlation between total chemical oxygen demand (TCOD), total nitrogen (TN), and total phosphorus (TP) removal efficiency, and a negative correlation between pH and TN, TP, and NH4+ removal efficiencies. High-throughput sequencing showed that the system was most abundant in Thermomonas, Geothrix and Geobacter when the electrodes were placed in the filled layer, while the levels of genes for membrane transport, carbohydrate metabolism and energy metabolism functions were higher than in other systems. This work will support STW- MFC widespread implementation by illuminating the underlying mechanics of different anode positions.

Seeing the forest for the fractions – Comparing soil organic matter fractionation methods using molecular features after forest stand conversion

The molecular composition of soil organic matter (SOM) contains key information on the persistence of soil carbon (C) in relation to changes in vegetation and environmental factors. Depending on the ecosystem, analytical method and specific objectives, many SOM fractions and numerous fractionation schemes have been proposed to study soil C. However, the molecular composition and environmental significance of those different SOM fractions have not yet been compared systematically. We use a reverse fit approach to fill this knowledge gap: i.e. we chose a study area with a well-known land history to assess which information is stored in the most frequently analysed SOM fractions. The Gaume forest (Belgium) is an ancient deciduous forest (>200 years) in which small stands were converted to Norway spruce (Picea abies) 40–50 years ago. Those stands are located along a lithological gradient in soil buffering capacity. We investigated the molecular composition of bulk mineral soil samples and five organic SOM fractions by pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The SOM fractions included particulate OM (POM), water extractable OM (WEOM), and fractions obtained by alkaline extraction, including the traditionally used humic acid (HA) and fulvic acid (FA) and the total base extract from which they are obtained (BE). Our results indicate that pyrolysates of bulk mineral soil did not prove useful to reflect environmental changes after forest stand conversion. Principal Component Analysis indicated that within each organic fraction similar changes occurred when comparing soil depths, degree of SOM decomposition, litter inputs, and soil buffering capacity. However, only the HA and BE appeared successful in capturing all these processes: the degree of SOM decomposition was not expressed in pyrolysates from the POM, differences in litter input between forest stand types were not evidenced in the WEOM, and effects of buffering capacity were not demonstrated in the WEOM and FA fractions. Thus, the molecular composition of different SOM fractions can be used complementary to each other to study environmental and ecological effects of forest stand conversion on soil C dynamics.

Removal of natural organic matter fractions by adsorptive asymmetric ceramic membrane functionalized with in situ phytogenic nanoscale zero valent iron: Performance and Fenton cleaning strategy

AbstractExtant literature has demonstrated that conventional water treatment processes especially in developing countries struggle in completely removing detrimental organic loads. Emerging research delineates nanomaterials such as nanoscale zero valent iron (nZVI) to have excellent performance in organic matter removal from aqueous media. In this work, nZVI particles were prepared from the liquor of commercially available green tea and supported on kaolin (K‐nZVI) and investigated as an adsorbent for natural organic matter (NOM) sequestration from aquatic media. Further, the asymmetric ceramic membrane was prepared by incorporating the developed adsorbent on a concrete support for the removal of NOM. A Fenton cleaning strategy was developed to mitigate fouling. The Brunauer–Emmett–Teller (BET) results revealed the developed adsorbent surface area was greater compared to raw kaolin (27.07 and 11.64 m3 g−1, respectively). The scanning electron microscopy (SEM) imagery of the developed adsorbent showed the particle staking was presented as paper slices of varying sizes, an indication of dispersed particles with characteristic plate‐like fragments. The synthesized membrane exhibited a pHZPC value of 4.79 ± 0.03. This meant at pH above 4.79 ± 0.03, the membrane would be negatively charged, and conversely at pH below the pHZPC value. Membrane fouling due to bovine serum albumin (BSA) deposition showed a 50% flux decline in the first 60 min, coinciding with the rapid adsorption capacity within the same time frame. The optimal cleaning parameters of pH (4.5) and H2O2 (5 mM) gave the best flux recovery rates. This work demonstrated an efficient Fenton cleaning strategy to regenerate the developed membrane.

Quantitative Carbon Changes of Selected Organic Fractions during the Aerobic Biological Recycling of Biodegradable Municipal Solid Waste (MSW) as a Potential Soil Environment Improving Amendment—A Case Study

The aim of the investigation was to determine the quantitative changes of selected organic compounds during composting of municipal solid wastes (MSWs). The object of the study was a differently matured compost produced according the to open pile/windrow semi-dynamic technology from selectively collected biodegradable municipal solid waste. During the experiment, the temperature and moisture of the composted wastes were monitored. In the collected samples—taken from differently matured compost—the total organic carbon (TOC) and total nitrogen (TN) were determined. The organic matter fractionation method described by Stevenson and Adani et al. was adopted, which allows to determine the carbon content of the following groups of organic compounds: hydrophobic (HSC), hydrophilic (WEOC), acidophilic (CAC), cellulose (CCEL), core-HA (ligno-humic, CALK) and residual carbon (non-hydrolysing, CR). The TOC and TN content, as well as the origin and quality of the starting materials, allow the product tested to be classified for fertiliser purposes. The most intense changes were observed during the thermophilic composting phase. In spite of the optimal technological conditions of the process, the predominance of the CR and CCEL fraction was observed, and the share of humic compounds did not exceed 30% TOC. The investigated compost met legal, ecological and economic criteria for products of biological recycling, thus can be used as a good organic amendment to improve the soil organic matter balance, stimulate the soil biodiversity and carbon sequestration.