Changes In Composition Of Organic Matter Research Articles

Peatland carbon chemistry, amino acids and protein preservation in biogeochemically distinct ecohydrologic layers

AbstractPeatlands play a significant role in global carbon and nitrogen cycles due to their carbon storage capabilities. However, there are key knowledge gaps in our understanding of how peatland hydrology influences the biogeochemical properties that drive peatland functioning and health. This study examines peatland hydrology and biogeochemical dynamics by exploring the variations in carbon chemistry, total amino acid (‘protein’) content and amino acid composition in the ecohydrologic layers: acrotelm, mesotelm and catotelm. The dynamic movement of the water table recorded half‐hourly over 4 years was used to assist in identifying the boundaries between these layers. Peat amino acids were measured using liquid chromatography‐tandem mass spectrometry (LC‐MS/MS). Carbon chemistry was analysed by solid state Cross Polarization Magic Angle Spinning (CPMAS) 13C Nuclear Magnetic Resonance (NMR) spectroscopy, with the alkyl:O‐alkyl ratio used to quantify the extent of decomposition. Our result revealed a strong positive correlation between the extent of decomposition and total protein content, indicating selective preservation of proteinaceous materials during peat decomposition. Each ecohydrologic layer displayed a distinct amino acid composition and carbon functional group composition. The acrotelm was relatively enriched in seven amino acids and two carbon functional groups. The mesotelm was relatively enriched in four amino acids, while the catotelm was relatively enriched in three amino acids and four carbon functional groups. The variations in amino acid composition reflect differences in microbial function and efficiency, while variations in carbon functional groups provide insights into long‐term carbon sequestration in peatland. Collectively, these results provide more insights into nutrient cycling and changes in organic matter composition during peat decomposition. These findings demonstrate that peatland biogeochemistry is closely linked to ecohydrology and suggest that changes to water table dynamics could affect the ability of peatlands to sequester and store carbon in the future.

Enhancing hydrogen-rich fuel gas production from dewatered sludge pyrolysis: The effect of hybrid conditioning with peroxyacetic acid, polyaluminium chloride, and KOH-modified activated carbon

Pyrolysis is a promising technology for the disposal of sewage sludge, because it not only greatly reduces the volume of sludge but also converts it into high calorific and pollution-free clean energy, H2. Direct pyrolysis of raw sludge (with moisture content of about 98%) consumes a lot of energy, thus it is necessary to dewater the raw sludge before pyrolysis. However, sludge is a heterogeneous colloidal system, making it difficult to reduce water content with traditional pressurization. Conditioning agents often are needed to improve the dewatering efficiency. In this work, we applied peroxyacetic acid (PA) and polyaluminium chloride (PAC) combined with KOH-modified activated carbon (KAC) to condition the raw sludge (denoted as PA/PAC/KAC) before conducting dewatering and pyrolysis. We found that changes of organic matter composition of the dewatered sludge exerted by the conditioning significantly influenced pyrolysis gas production. The pyrolysis H2 yield from the conditioned sludge can be 4–5-fold higher than the unconditioned. The PA oxidation mediated by KAC led to more olefin substances appearing in the dewatered sludge, which further promoted the production of low aromatic hydrocarbons through the Diels-Alder reaction in pyrolysis and enhanced tar cracking rate. Potassium loaded on KAC catalyzed tar cracking. KAC remained in the dewatered sludge promoted water–gas-shift (WGS) and steam reforming reactions to produce more H2. This study provides a new path to enhance the resource utilization of dewatered sludge and facilitate the resource utilization of the dewatered sludge in potential applications.

Infrared-based analysis of organic matter composition in liquid and solid runoff fractions collected during a single erosion event

Heavy rain events can cause soil material to be widely transported by surface runoff in arable soil landscapes. While soils of the eroded hilltop and backslope areas are affected by a loss of material, soil properties in deposition areas are affected by sedimentation of particulate and dissolved mineral and organic substances. During the event, the composition of mineral and organic matter (OM) fractions changes dynamically with runoff velocity. However, changes in OM composition during runoff have mostly been neglected. The objective was to identify changes of OM composition of runoff fractions with time and flow velocity during a single rainfall-runoff event. By the comparison of runoff from a conventionally-tilled (CT) plot and a no-till (NT) plot, we aimed at discussing process-based explanations for dynamic OM composition in runoff. Surface runoff was collected from CT and NT plots at the toe-slope of an experimental hillslope. Time-dependent runoff samples were compared with cumulative bulk samples obtained by Coshocton wheels and separated in a coarser sediment (sed>63 µm) and a finer fraction of < 63 µm-sized particles plus dissolved OM (<63 µm&diss). The OM composition was determined with Fourier transform infrared (FTIR) spectroscopy. It was found to change with runoff volume due to contact with litter (NT) or soil minerals (CT) mainly for finer fractions from both CT and NT plots. Even during a single runoff event, the OM mass and composition in runoff changes characteristically. The OM composition dynamics was dominated by OMcat/C-O-C ratios in runoff from CT and by C-H/CO ratios in runoff from NT due to contact with soil minerals (CT) and litter (NT). The time-dependent collection schemes suggested that OM composition in runoff reflected the surface properties and could help to further improve explanations for spatial distribution of OM-related soil properties such as the potential wettability in arable soil landscapes.

Physical and biogeochemical drivers of solute mobilization and flux through the critical zone after wildfire

A nine-year time series of nutrient cation and anion concentration and efflux from three forested catchments in the Jemez River Basin Critical Zone Observatory (JRB-CZO) in northern New Mexico was used to quantify the pulse of chemical denudation resulting from varying levels stand-replacing wildfire intensity in May-June of 2013. The 3 years of pre-fire and 6 years of postfire data were also probed to shed light on the mechanisms underlying the pulsed release and the subsequent recovery. The initial large solute pulse released to the streams—K+, Ca2+, Mg2+, SO42-, Cl−, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and total dissolved nitrogen (TDN)—was caused by leaching of hillslope ash deposits during the first monsoon storms post-fire. Debris flow following the wildfire likely redistributed much of the ash-containing sediments along streams and valley bottoms. Sustained elevated solute concentrations observed in the surface waters throughout the post-fire period relative to pre-fire baselines is consistent with these soluble materials being periodically flushed from the soils during wet seasons, i.e., snowmelt and summer monsoons. As microbial mediated reactions and biotic uptake—due to plant regrowth—recover after fire, nutrient ion export (e.g., NO3-, Cl− and SO42-) steadily decreased toward the end of the post fire period, but remained above pre-fire levels, particularly for NO3- and SO42-. Surface water concentrations of polyvalent cations (e.g., Al and Fe) decreased significantly after the fire. Our observations suggest that changes in organic matter composition after fire (e.g., increased humification index—HIX) and the presence of pyrogenic carbon may not favor organo-metal complexation and transport. Finally, differences in burn severity among the three watersheds presented in this study, provide insights of the relative impact of solute exports and resilience. The catchments that experienced high burn severity exhibited greater solute fluxes than the less severely burn. Moreover, despite these differences, toward the end of the post-fire period these surface waters presented low and similar solute effluxes, indicating system recovery. Nonetheless, magnitudes and rebounds were solute and process specific. The results of this study highlight the importance of surface and near surface physical and biogeochemical processes on the long-lasting geochemical denudation of forested catchments following wildfires of varying intensities.

Linking Seasonal Changes in Organic Matter Composition and Nutrients to Shifting Hydraulic Gradients in Coastal Urban Canals

AbstractThe capacity for coastal river networks to transport and transform dissolved organic matter (DOM) is widely accepted. However, climate‐induced shifts in stormwater runoff and tidal extension alter fresh and marine water source contributions, associated DOM, and processing rates of nutrients entering coastal canals. We investigate how time‐variable interactions among coastal water source contributions influence the concentrations of dissolved organic carbon (DOC), nutrients, and DOM composition in urban canals. We quantified the spatiotemporal variability of DOM quality and nutrient concentrations to determine contributions of tidal marine water, rainwater, stormwater runoff, and groundwater to three coastal urban canals of Miami, Florida (USA). We created a Bayesian Monte Carlo mixing model using measurements of fluorescent DOM (fDOM), DOC concentrations, δ18O and δ2H isotopic signatures, and chloride (Cl−). Fractional contributions of groundwater averaged 17% in the dry season and 26% at peak high tide during the subtropical wet season (September–November). The canal‐to‐marine head difference (CMHD) was a primary driver of groundwater contributions to coastal urban canals and monthly patterns of fDOM/DOC. High tide (&gt;1 m) and discharge events were found to connect canals to upstream sources of terrestrial DOM. Loading of terrestrially sourced DOC and DOM is pulsed to urban canals, shunted downstream and supplemented by microbially sourced DOM during the wet season at high tide. Overall, we demonstrate that a combined tracer approach with isotopes and fDOM can help identify groundwater contributions to coastal waterways and that autochthonous fDOM may prime the degradation of carbon or nutrients as the CMHD pushes inland.

Changes of organic matter composition in surface sediments from the Pearl River estuary to the coastal South China Sea revealed by rapid molecular screening using FTICR-MS

The Pearl River drains the second largest watershed in China, funnelling large amounts of freshwater and organic matter into the northern part of the South China Sea through an estuary characterized by pronounced biogeochemical gradients. In this study we used a newly developed single injection Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) method to analyze organic extracts of surface sediments transitioning from freshwater to marine settings in the Pearl River estuary and coastal South China Sea. Results show a complex mixture of molecular markers, with distinct fingerprints characterizing the freshwater and saline sites. Notable examples include steroidal and thiophenic species at the freshwater site, indicative of possible anthropogenic organic matter inputs from the continent; on the other hand, samples from the coastal site are uniquely characterized by putative tetrapyrrole species, indicative of phaeopigments sourced from marine phytoplankton. This study demonstrates the potential application of single injection FTICR-MS in rapidly probing the dynamic changes of organic matter sources and fates occurring in estuaries influenced by anthropogenic activities.

Changes in shale gas produced water DOM during its early storage period: Molecular composition correlated with microbial functions

The environmental problem posed by shale gas wastewater has received considerable research attention. Researchers mostly focus on the technical aspect of terminal centralized treatment with little concern on the topic of early collection and on-site pretreatment of PW near gas gathering stations. In this study, the short-term fluctuations of the DOM molecular composition and the concurrent transformation of the microbial community and functions were carefully examined when the PW was temporarily stored in a simulated reservoir near gas wells. Ultra-high resolution mass spectrometry was used to determine the molecular structure of the DOM samples. The data showed that during the short-term storage of PW, strongly polarized and nonvolatile organic compounds developed a complex molecular structure, resulting in molecules that were more unsaturated and lower bioavailability. Microbial activity was responsible for the changes in organic matter composition that occurred in the later stages of the storage process, during which the amount of nitrogenous organic molecules increased. Network analysis offered vital information on microbial functions related to organic matter composition and the patterns of interaction between them. Organic molecule consumption and accumulation were intimately connected to the interactions between various bacteria the same as the consumption and accumulation of DOM molecules.

Enhanced biological S0 accumulation by using signal molecules during simultaneous desulfurization and denitrification

ABSTRACT A high rate of elemental sulfur (S0) accumulation from sulfide-containing wastewater has great significance in terms of resource recovery and pollution control. This experimental study used Thiobacillus denitrificans and denitrifying bacteria incorporated with signal molecules (C6 and OHHL) for simultaneous sulfide (S2–) and nitrate (NO3 –) removal in synthetic wastewater. Also, the effects on S0 accumulation due to changes in organic matter composition and bacteria proportion through signal molecules were analyzed. The 99.0% of S2– removal and 99.3% of NO3 – was achieved with 66% of S0 accumulation under the active S2– removal group. The S0 accumulation, S2– and NO3 – removal mainly occurred in 0–48 h. The S0 accumulation in the active S2– removal group was 2.0-6.3 times higher than the inactive S2– removal groups. In addition, S0/SO4 2- ratio exhibited that S0 conversion almost linearly increased with reaction time under the active S2– removal group. The proportion of Thiobacillus denitrificans and H+ consumption showed a positive correlation with S0 accumulation. However, a very high or low ratio of H+/S0 is not suitable for S0 accumulation. The signal molecules greatly increased the concentration of protein-I and protein-II, which resulted in the high proportion of Thiobacillus denitrificans. Therefore, high S0 accumulation was achieved as Thiobacillus denitrificans regulated the H+ consumption and electron transfer rate and provided suppressed oxygen environment. This technology is cost-effective and commercially applicable for recovering S0 from wastewater.

Changes in organic matter composition caused by EDTA washing of two soils contaminated with toxic metals

Two soils contaminated with potentially toxic metals (PTMs) contrasting in pH and mineralogy were remediated with CaEDTA, and changes in soil organic matter (SOM) composition were investigated. Previous studies showed no significant loss of SOM from CaEDTA-treated soils, but the results of our study reflected significant decreases (from 46 to 49%) in the free fraction of humic acids (HAs). Remediation affected the composition of the free HA fraction via disturbance of intermolecular bonds — an increase in phenolic and aromatic groups with a simultaneous decrease in carbohydrates — which was confirmed by FTIR spectroscopy in both soils. Because non-radical molecules such as carbohydrates were selectively removed, the concentration of free radicals in the free HA fraction increased in acidic soil. The bound fraction of HAs and fulvic acids (FAs) in SOM, which are important due to their stability and the permanent effects they have on the soil’s physical properties, remained unchanged in both remediated soils. The effect of soil recultivation was observed only in the excitation emission matrix (EEM) fluorescence spectra of HAs. In terms of SOM, CaEDTA soil washing can be considered moderately conservative; however, the restoration of free humic fractions is likely to be a long-term process.

Changes in organic matter composition during the Toarcian Oceanic Anoxic Event (T-OAE) in the Posidonia Shale Formation from Dormettingen (SW-Germany)

During the Early Toarcian, deposition of organic carbon-rich-shales occurred throughout the epicontinental sea across Europe. Climate instability and high extinction rates in the marine realm were associated with profound environmental changes. The Toarcian Oceanic Anoxic Event (T-OAE) has been linked to the injection of greenhouse gases (e.g. oceanic methane) into the atmosphere triggered by the emplacement of the Karoo-Ferrar large igneous province (LIP) volcanism. The data presented are obtained from the Posidonia Shale Formation in Dormettingen (southwestern Germany), ~2 km from the well-known Dotternhausen section. Despite the intense palaeontological and geochemical research, studies on the particulate organic matter (POM) across the T-OAE are scarce. Here, we provide a detailed study of POM of the Dormettingen section as a tool to evaluate changes in the depositional environment. Integrated POM (i.e. amorphous organic matter, marine and terrestrial palynomorphs) and geochemical (i.e. carbon isotope δ13C) analyses reveal different episodes of palaeoecological upheavals during the studied time interval. In this study, we will integrate new palynofacies data and combine it with the existing sedimentological and palaeoecological data of Dotternhausen in order to interpret relative sea-level fluctuations and climatic changes at the local palaeogeographic setting.

Age matters: Fate of soil organic matter during ageing of earthworm casts produced by the anecic earthworm Amynthas khami

The transformation of organic matter (OM) occluded in earthworm casts during the casts' lifetime may affect its composition and accumulation in stabilised OM pools. We collected casts produced by the anecic earthworm Amynthas khami in a tropical woodland of Northern Vietnam presenting different degradation stages. The aim of this study was to assess (1) the biogeochemical properties of OM in earthworm casts compared to control aggregates from the surrounding soil, and (2) the fate of occluded OM during cast ageing. We analysed intact casts and their density fractions at five ageing stages for organic carbon (OC) and nitrogen (N) content, OM chemical composition by analytical pyrolysis, and OM stability by Rock-Eval thermal analysis. Compared to control aggregates, fresh casts had higher OC values (5.3 vs. 2.6%) and increased OC in all density fractions. Cast OM had more lignin (1.1 vs.<0.1%), similar polysaccharide and N-compound contribution and was more thermally labile than those of control aggregates. Changes in OM composition and content during cast ageing appeared at the end of the casts’ lifetime, when they were broken into smaller aggregates (10–13 mm). At these latest stages, OC content decreased (1.5-fold); along with OM in macro-aggregates (2.2-fold) and microaggregates (6.8-fold). Reduced mineral-associated OC was also recorded (1.3-fold). During ageing, the percentage of lignin decreased (5.5-fold) while the thermal stability of OM increased. The distinct OM properties of casts were maintained throughout the cast ageing process, and most properties of the oldest casts were significantly different from the control aggregates. Since OM is retained in cast fragments after they disintegrate, the earthworm influence on soil organic matter stabilisation processes appears to persist beyond the lifespan of casts.

Integrated farming systems influence soil organic matter dynamics in southeastern Brazil

Integrated farming systems are sustainable strategies to intensify land productivity by combining annual crop, livestock and/or forestry activities in different spatio-temporal arrangements. Therefore, they may help tackle global food and energy insecurity and climate change in the coming decades. We investigated the effects of integrated crop-livestock (ICL) and integrated crop-livestock-forestry (ICLF) systems on quantity, quality, and origin of soil organic matter (SOM) in southeastern Brazil. A native forest and an extensive low-grazing intensity pasture system were used as references. In integrated systems, corn (Zea mays) was alternated with two consecutive years of piatã grass (Urochloa bryzantha) for cattle grazing. In ICLF, eucalyptus trees (Eucalyptus urograndis) were planted in simple rows of 15 × 2 m. Soil sampling was performed three times; in 2014, after two years of grazing; in 2015, after crop cultivation; and in 2016, after a successive grazing year, to evaluate chemical and physical composition changes of organic matter (C, N, δ13C, δ15N, and organic matter fractions) with time. Our findings showed that from 2010 to 2016, all systems (extensive grazing, ICL and ICLF) promoted increments on soil C and N stocks. However, land intensification converting extensive low-grazing intensity pasture to ICL was the most promising strategy, increasing soil C stocks at the rate of 0.28 Mg C ha−1 yr−1 from 2010 to 2016. Annual crop cultivation (corn intercropped with piatã grass) promoted high organic matter inputs on the soil, increasing the amount of soil labile organic matter fractions, which presented higher δ13C and lower δ15N values over time. SOM in the integrated farming systems was originated mainly from C4 plants. Therefore, optimizing development of piatã grass and corn increases organic residue inputs and then, soil C and N stocks. In addition, the crop period increased soil fertility parameters, which favors plant growth, thus providing high labile C inputs to the soil. In contrast, land intensification by adding the forestry component into the system (i.e., conversion from ICL to ICLF) reduced soil C (-0.22 Mg C ha−1 yr−1) and N (-0.03 Mg N ha−1 yr−1) stocks from 2010 to 2016, likely due to the reduction of C and N inputs to the soil caused by limited growth of annual crop and grass species under tree shades. In conclusion, land use intensification through ICL system contributes towards a more efficient and low-C agriculture, whereas the studied ICLF system did not bring further benefits to increase the quantity and/or quality of SOM.

Molecular changes of soil organic matter induced by root exudates in a rice paddy under CO2 enrichment and warming of canopy air

While crop productivity and carbon flux/partitioning in agroecosystem have been widely addressed, potential changes in organic matter composition through root deposition are still unknown under climate change. In this study, root exudates of rice and rhizospheric topsoil were collected in a paddy field under 6 years of simulated climate changes respective of CO2 enrichment, canopy air warming, and their combination as compared to the control. The molecular composition of root exudates was analyzed with liquid chromatography/mass spectrometry (LC/MS) while soil organic matter (SOM) was analyzed with pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), along with a phospholipid fatty acid analysis (PLFA) for characterizing soil microbial community. Compared to control, root exudation under elevated CO2 was enhanced but the exudate composition remained unchanged. On the other hand, root exudation rate under warming was unaffected, but the exudate composition was changed. Relative abundance of phenolic compounds in root exudates under warming, was decreased by 26% but that of amino acids was increased by 53%. However, neither root exudation nor the exudate composition was altered under combined CO2 and temperature elevation. Furthermore, increases in abundance of heterocyclic nitrogen compounds, phenolic acids and phenols (by 37%, 65%, and 26%, respectively) in SOM were relevant to the increase in bacterial/fungal (B/F) ratio under elevated CO2. This accumulation was possibly attributed to preferential utilization of the increased root exudates by bacteria. However, the overall reduction of some highly hydrophobic SOM compounds (fatty acids, phenols, and phenolic acids) by 14%, could be induced by accelerated decomposition in line with significant decrease in B/F ratio under warming. Indeed, the decreased relative abundance of phenolic compounds such as p-coumaric acid (by 49%) in root exudates lead to fungal increase, which accelerated SOM decomposition. Yet, the molecular composition of SOM was hardly changed under the combination of elevated CO2 and temperature. Overall, our findings suggested that in a rice paddy CO2 enrichment increased root exudation and B/F ratio, while air warming altered the root exudate composition and decreased B/F ratio, resulting in changes of SOM composition. These results indicate that root exudates are a key component for the regulation of SOM dynamics under climate change scenarios.

Resource heterogeneity structures aquatic bacterial communities

Microorganisms are strongly influenced by the bottom-up effects of resource supply. While many species respond to fluctuations in the concentration of resources, microbial diversity may also be affected by the heterogeneity of the resource pool, which often reflects a mixture of distinct molecules. To test this hypothesis, we examined resource-diversity relationships for bacterioplankton in a set of north temperate lakes that varied in their concentration and composition of dissolved organic matter (DOM), which is an important resource for heterotrophic bacteria. Using 16S rRNA transcript sequencing and ecosystem metabolomics, we documented strong relationships between bacterial alpha-diversity (richness and evenness) and the bulk concentration and the number of molecules in the DOM pool. Similarly, bacterial community beta-diversity was related to both DOM concentration and composition. However, in some lakes the relative abundance of resource generalists, which was inversely related to the DOM concentration, may have reduced the effect of DOM heterogeneity on community composition. Together, our results demonstrate the potential metabolic interactions between bacteria and organic matter and suggest that changes in organic matter composition may alter the structure and function of bacterial communities.

On the changing petroleum generation properties of Alum Shale over geological time caused by uranium irradiation

An interdisciplinary study was carried out to unravel organic–inorganic interactions caused by the radiogenic decay of uranium in the immature organic-rich Alum Shale (Middle Cambrian-Lower Ordovician).Based on pyrolysis experiments, uranium content is positively correlated with the gas-oil ratios and the aromaticities of both the free hydrocarbons residing in the rock and the pyrolysis products from its kerogen, indicating that irradiation has had a strong influence on organic matter composition overall and hence on petroleum potential. The Fourier Transform Ion Cyclotron Resonance mass spectrometry data reveal that macro-molecules in the uranium-rich Alum Shale samples are less alkylated than less irradiated counterparts, providing further evidence for structural alteration by α-particle bombardment. In addition, oxygen containing-compounds are enriched in the uranium-rich samples but are not easily degradable into low-molecular-weight products due to irradiation-induced crosslinking.Irradiation has induced changes in organic matter composition throughout the shale’s entire ca. 500 Ma history, irrespective of thermal history. This factor has to be taken into account when reconstructing petroleum generation history. The Alum Shale’s kerogen underwent catagenesis in the main petroleum kitchen area 420–340 Ma bp. Our calculations suggest the kerogen was much more aliphatic and oil-prone after deposition than that after extensive exposure to radiation. In addition, the gas sorption capacity of the organic matter in the Alum Shale can be assumed to have been less developed during Palaeozoic times, in contrast to results gained by sorption experiments performed at the present day, for the same reason. The kerogen reconstruction method developed here precludes overestimations of gas generation and gas retention in the Alum Shale by taking irradiation exposure into account and can thus significantly mitigate charge risk when applied in the explorations for both conventional and unconventional hydrocarbons.

Multi-century record of anthropogenic impacts on an urbanized mesotidal estuary: Salem Sound, MA.

Salem, MA, located north of Boston, has a rich, well-documented history dating back to settlement in 1626 CE, but the associated anthropogenic impacts on Salem Sound are poorly constrained. This project utilized dated sediment cores from the sound to assess the proxy record of anthropogenic alterations to the system and compared the proxy records to the known history. Proxies included bulk stable isotopes of organic matter, magnetic susceptibility, and trace metal concentrations. Our data reveal clear changes in organic matter composition and concentration associated with land use changes and twentieth century sewage disposal practices. Further, metals data correspond with local industrial activity, particularly the historic tanning industry in Peabody, MA. Although conservation practices of past decades have improved the state of Salem Sound, the stratigraphic record demonstrates that the environment is still affected by anthropogenic influences, and has not attained conditions consistent with pre-anthropogenic baseline. The approach and results of this study are applicable to coastal embayments that are being assessed for remediation, especially those with scant historic or monitoring data.

Investigating molecular changes in organic matter composition in two Holocene lake‐sediment records from central Sweden using pyrolysis‐GC/MS

AbstractOrganic matter (OM) is a key component of lake sediments, affecting carbon, nutrient, and trace metal cycling at local and global scales. Yet little is known about long‐term (millennial) changes in OM composition due to the inherent chemical complexity arising from multiple OM sources and from secondary transformations. In this study we explore how the molecular composition of OM changes throughout the Holocene in two adjacent boreal lakes in central Sweden and compare molecular‐level information with conventional OM variables, including total carbon, total nitrogen, C:N ratios, δ13C, and δ15N. To characterize the molecular OM composition, we employed a new method based on pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), which yields semiquantitative data on &gt;100 organic compounds of different origin and degradation status. We identify large changes in OM composition after deglaciation (circa 8500 ± 500 B.C.), associated with early landscape development, and during the most recent 40–50 years, driven by degradation processes. With molecular‐level information we can also distinguish between natural landscape development and human catchment disturbance during the last 1700 years. Our study demonstrates that characterization of the molecular OM composition by the high‐throughput Py‐GC/MS method is an efficient complement to conventional OM variables for identification and understanding of past OM dynamics in lake‐sediment records. Holocene changes observed for pyrolytic compounds and compound classes known for having different reactivity indicate the need for further paleo‐reconstruction of the molecular OM composition to better understand both past and future OM dynamics and associated environmental changes.

Improved fermentation performance in an expanded ectopic fermentation system inoculated with thermophilic bacteria

Previous research showed that ectopic fermentation system (EFS) inoculated with thermophilic bacteria is an excellent alternative for cow wastewater treatment. In this study, the effects of thermophilic bacterial consortium on the efficiency and quality of the fermentation process in EFS were evaluated by measuring physicochemical and environmental factors and the changes in organic matter composition. In parallel, the microbial communities correlated with fermentation performance were identified. Inoculation of EFS with thermophilic bacterial consortium led to higher temperatures, increased wastewater requirements for continuous fermentation, and improved quality of the litters in terms of physicochemical factors, security test, functional group analysis, and bacterial community composition. The relationship between the transformation of organic component and the dominant bacteria species indicated that environmental factors contributed to strain growth, which subsequently promoted the fermentation process. The results highlight the great potential of EFS model for wide application in cow wastewater treatment and re-utilization as bio-fertilizer.

Detection of residual oil-sand-derived organic material in developing soils of reclamation sites by ultra-high-resolution mass spectrometry.

The reconstruction of disturbed landscapes back to working ecosystems is an issue of increasing importance for the oil sand areas in Alberta, Canada. In this context, the fate of oil-sand-derived organic material in the tailings sands used for reclamation is of utmost environmental importance. Here we use electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry of maltene fractions to identify compositional variations over a complete oil sand mining and recultivation process chain. On the basis of bulk compound class distributions and percentages of unique elemental compositions, we identify specific compositional features that are related to the different steps of the process chain. The double bond equivalent and carbon number distributions of the N1 and S1O2 classes are almost invariant along the process chain, despite a significant decrease in overall abundance. We thus suggest that these oil-sand-derived components can be used as sensitive tracers of residual bitumen, even in soils from relatively old reclamation sites. The patterns of the O2, O3, and O4 classes may be applied to assess process-chain-related changes in organic matter composition, including the formation of plant-derived soil organic matter on the reclamation sites. The N1O2 species appear to be related to unidentified processes in the tailings ponds but do not represent products of aerobic biodegradation of pyrrolic nitrogen compounds.

Geochemical study of maltenes from coal biodesulphurisation

The aim of the study is to examine by geochemical proxies the effect of biodesulphurisation on coal organic matter composition. Two Bulgarian and one Turkish low rank coals (Rr=0.20–0.46%) were analysed. Prior to biotreatments, the coals were demineralised and depyritised. The white rot fungi Phanerochaete chrysosporium – ME446 and the thermophilic and acidophilic archae Sulfolobus solfataricus – ATCC 35091 were used.After desulphurisations the samples were extracted with chloroform to recover bitumens. Maltenes (portion soluble in n-hexane) were prepared after asphaltenes precipitation. They were fractionated into aliphatic, aromatic and polar fractions and the first two were GC/MS studied. The following homologous series were registered: (i) n-alkanes, nC12–nC32, mainly long-chain homologues with “odd” members prevalence; (ii) n-alkan-2-ones; (iii) esters of n-fatty acids, nC12–nC32, with bimodal distributions; (iv) diterpenoids; (v) products of triterpenoids destruction and aromatisation; (vi) hopanoids. Results were quantitatively interpreted.All studied fractions of initial and biotreated samples were strongly dominated by n-alkanes, 60–90%, but patterns of distributions after desulphurisations were somewhat changed as shorter homologues had partly disappeared. Relative distribution of geochemically considered series depicted some peculiarities: (i) organic matter of higher mature coal was less attained by desulphurisation; (ii) lignite organic matter seemed to be more susceptible to biotreatment especially with P. chrysosporium culture. During S. solfataricus biodesulphrisation different series preserved their pattern of distribution while P. chrysosporium treatment strongly perturbed it.There were indications for coal organic matter oxidation assigned by polar biomarkers appearance. Tercyclohexanes were detected only in products of coals biotreated with S. solfataricus. The gradual changes in organic matter composition depicted by a scale adopted from petroleum exploration attested “light” biodegradation during coal biodesulphurisation.