Granulometry, mineralogy and organic matter content of permafrost core 5011-3

The combination of permafrost history and dynamics, lake level changes and the tectonical framework is considered to play a crucial role for sediment delivery to El'gygytgyn Crater Lake, NE Russian Arctic. The purpose of this study is to propose a depositional framework based on analyses of the core strata from the lake margin and historical reconstructions from various studies at the site. A sedimentological program has been conducted using frozen core samples from the 141.5 m long El'gygytgyn 5011-3 permafrost well. The drill site is located in sedimentary permafrost west of the lake that partly fills the El'gygytgyn Crater. The total core sequence is interpreted as strata building up a progradational alluvial fan delta. Four macroscopically distinct sedimentary units are identified. Unit 1 (141.5-117.0 m) is comprised of ice-cemented, matrix-supported sandy gravel and intercalated sandy layers. Sandy layers represent sediments which rained out as particles in the deeper part of the water column under highly energetic conditions. Unit 2 (117.0-24.25 m) is dominated by ice-cemented, matrix-supported sandy gravel with individual gravel layers. Most of the Unit 2 diamicton is understood to result from alluvial wash and subsequent gravitational sliding of coarse-grained (sandy gravel) material on the basin slope. Unit 3 (24.25-8.5 m) has ice-cemented, matrix-supported sandy gravel that is interrupted by sand beds. These sandy beds are associated with flooding events and represent near-shore sandy shoals. Unit 4 (8.5-0.0 m) is ice-cemented, matrix-supported sandy gravel with varying ice content, mostly higher than below. It consists of slope material and creek fill deposits. The uppermost metre is the active layer (i.e. the top layer of soil with seasonal freeze and thaw) into which modern soil organic matter has been incorporated. The nature of the progradational sediment transport taking place from the western and northern crater margins may be related to the complementary occurrence of frequent turbiditic layers in the central lake basin, as is known from the lake sediment record. Slope processes such as gravitational sliding and sheet flooding occur especially during spring melt and promote mass wasting into the basin. Tectonics are inferred to have initiated the fan accumulation in the first place and possibly the off-centre displacement of the crater lake.

Redistribution of Soil Organic Matter by Permafrost Disturbance in the Canadian High Arctic

With increased warming in the Arctic, permafrost thaw may induce localized physical disturbance of slopes. These disturbances, referred to as active layer detachments (ALDs), redistribute soil across the landscape, potentially releasing previously unavailable carbon (C). In 2007–2008, widespread ALD activity was reported at the Cape Bounty Arctic Watershed Observatory in Nunavut, Canada. Our study investigated organic matter (OM) composition in soil profiles from ALD-impacted and undisturbed areas. Solid-state 13C nuclear magnetic resonance (NMR) and solvent-extractable biomarkers were used to characterize soil OM. Throughout the disturbed upslope profile, where surface soils and vegetation had been removed, NMR revealed low O-alkyl C content and biomarker analysis revealed low concentrations of solvent-extractable compounds suggesting enhanced erosion of labile-rich OM by the ALD. In the disturbed downslope region, vegetation remained intact but displaced material from upslope produced lateral compression ridges at the surface. High O-alkyl content in the surface horizon was consistent with enrichment of carbohydrates and peptides, but low concentrations of labile biomarkers (i.e., sugars) suggested the presence of relatively unaltered labile-rich OM. Decreased O-alkyl content and biomarker concentrations below the surface contrasted with the undisturbed profile and may indicate the loss of well-established pre-ALD surface drainage with compression ridge formation. However, pre-ALD profile composition remains unknown and the observed decreases may result from nominal pre-ALD OM inputs. These results are the first to establish OM composition in ALD-impacted soil profiles, suggesting reallocation of permafrost-derived soil C to areas where degradation or erosion may contribute to increased C losses from disturbed Arctic soils.

Potential Shifts in Canadian High Arctic Sedimentary Organic Matter Composition With Permafrost Active Layer Detachments

Increased temperature and precipitation in Arctic regions have led to deeper thawing and structural instability in permafrost soil. The resulting localized disturbances, referred to as active layer detachments (ALDs), may transport organic matter (OM) to more biogeochemically active zones. To examine this further, solid state cross polarization magic angle spinning 13C nuclear magnetic resonance (CPMAS NMR) and biomarker analysis were used to evaluate potential shifts in riverine sediment OM composition due to nearby ALDs within the Cape Bounty Arctic Watershed Observatory, Nunavut, Canada. In sedimentary OM near ALDs, NMR analysis revealed signals indicative of unaltered plant-derived material, likely derived from permafrost. Long chain acyclic aliphatic lipids, steroids, cutin, suberin and lignin occurred in the sediments, consistent with a dominance of plant-derived compounds, some of which may have originated from permafrost-derived OM released by ALDs. OM degradation proxies for sediments near ALDs revealed less alteration in acyclic aliphatic lipids, while constituents such as steroids, cutin, suberin and lignin were found at a relatively advanced stage of degradation. Phospholipid fatty acid analysis indicated that microbial activity was higher near ALDs than downstream but microbial substrate limitation was prevalent within disturbed regions. Our study suggests that, as these systems recover from disturbance, ALDs likely provide permafrost-derived OM to sedimentary environments. This source of OM, which is enriched in labile OM, may alter biogeochemical patterns and enhance microbial respiration within these ecosystems.

Loadings of dissolved organic matter and nutrients from the Neva River into the Gulf of Finland – Biogeochemical composition and spatial distribution within the salinity gradient

We studied the loadings of dissolved organic matter (DOM) and nutrients from the Neva River into the Eastern Gulf of Finland, as well as their distribution within the salinity gradient. Concentrations of dissolved organic carbon (DOC) ranged from 390 to 840 μM, and were related to absorption of colored DOM (CDOM) at 350 nm, aCDOM(350), ranging from 2.70 to 17.8 m-1. With increasing salinity both DOC and aCDOM decreased, whereas the slope of aCDOM spectra, SCDOM(300-700), ranging from 14.3 to 21.2 μm-1, increased with salinity.

Loadings of dissolved organic matter and nutrients from the Neva River into the Gulf of Finland – Biogeochemical composition and spatial distribution within the salinity gradient

We studied the loadings of dissolved organic matter (DOM) and nutrients from the Neva River into the Eastern Gulf of Finland, as well as their distribution within the salinity gradient. Concentrations of dissolved organic carbon (DOC) ranged from 390 to 840 μM, and were related to absorption of colored DOM (CDOM) at 350 nm, aCDOM(350), ranging from 2.70 to 17.8 m-1. With increasing salinity both DOC and aCDOM decreased, whereas the slope of aCDOM spectra, SCDOM(300-700), ranging from 14.3 to 21.2 μm-1, increased with salinity.

Microbial metabolism mediates interactions between dissolved organic matter and clay minerals in streamwater

Sorption of organic molecules to mineral surfaces is an important control upon the aquatic carbon (C) cycle. Organo-mineral interactions are known to regulate the transport and burial of C within inland waters, yet the mechanisms that underlie these processes are poorly constrained. Streamwater contains a complex and dynamic mix of dissolved organic compounds that coexists with a range of organic and inorganic particles and microorganisms. To test how microbial metabolism and organo-mineral complexation alter amino acid and organic carbon fluxes we experimented with 13C-labelled amino acids and two common clay minerals (kaolinite and montmorillonite). The addition of 13C-labelled amino acids stimulated increased microbial activity. Amino acids were preferentially mineralized by the microbial community, concomitant with the leaching of other (non-labelled) dissolved organic molecules that were removed from solution by clay-mediated processes. We propose that microbial processes mediate the formation of organo-mineral particles in streamwater, with potential implications for the biochemical composition of organic matter transported through and buried within fluvial environments.

Effects of Soil Organic Matter Properties and Microbial Community Composition on Enzyme Activities in Cryoturbated Arctic Soils

Enzyme-mediated decomposition of soil organic matter (SOM) is controlled, amongst other factors, by organic matter properties and by the microbial decomposer community present. Since microbial community composition and SOM properties are often interrelated and both change with soil depth, the drivers of enzymatic decomposition are hard to dissect. We investigated soils from three regions in the Siberian Arctic, where carbon rich topsoil material has been incorporated into the subsoil (cryoturbation). We took advantage of this subduction to test if SOM properties shape microbial community composition, and to identify controls of both on enzyme activities. We found that microbial community composition (estimated by phospholipid fatty acid analysis), was similar in cryoturbated material and in surrounding subsoil, although carbon and nitrogen contents were similar in cryoturbated material and topsoils. This suggests that the microbial community in cryoturbated material was not well adapted to SOM properties. We also measured three potential enzyme activities (cellobiohydrolase, leucine-amino-peptidase and phenoloxidase) and used structural equation models (SEMs) to identify direct and indirect drivers of the three enzyme activities. The models included microbial community composition, carbon and nitrogen contents, clay content, water content, and pH. Models for regular horizons, excluding cryoturbated material, showed that all enzyme activities were mainly controlled by carbon or nitrogen. Microbial community composition had no effect. In contrast, models for cryoturbated material showed that enzyme activities were also related to microbial community composition. The additional control of microbial community composition could have restrained enzyme activities and furthermore decomposition in general. The functional decoupling of SOM properties and microbial community composition might thus be one of the reasons for low decomposition rates and the persistence of 400 Gt carbon stored in cryoturbated material.

Ecological stoichiometry controls the transformation and retention of plant-derived organic matter to humus in response to nitrogen fertilisation

Carbon (C) sequestration in soils is a means for increasing soil organic carbon (SOC) stocks and is a potential tool for climate change mitigation. One recommended management practice to increase SOC stocks is nitrogen (N) fertilisation, however examples of positive, negative or null SOC effects in response to N addition exist. We evaluated the relative importance of plant molecular structure, soil physical properties and soil ecological stoichiometry in explaining the retention of SOC with and without N addition. We tracked the transformation of 13C pulse-labelled buffel grass (Cenchrus ciliaris L.), wheat (Triticum aestivum L.) and lucerne (Medicago sativa L.) material to the <53 μm silt + clay soil organic C fraction, hereafter named “humus”, over 365-days of incubation in four contrasting agricultural soils, with and without urea-N addition. We hypothesised that: a) humus retention would be soil and litter dependent; b) humus retention would be litter independent once litter C:N ratios were standardised with urea-N addition; and c) humus retention would be improved by urea-N addition. Two and three-way factorial analysis of variance indicated that 13C humus was consistently soil and litter dependent, even when litter C:N ratios were standardised, and that the effect of urea-N addition on 13C humus was also soil and litter dependent. A boosted regression analysis of the effect of 44 plant and soil explanatory variables demonstrated that soil biological and chemical properties had the greatest relative influence on 13C humus. Regression tree analyses demonstrated that the greatest gains in 13C humus occurred in soils of relatively low total organic C, dissolved organic C and microbial biomass C (MBC), or with a combination of relatively high MBC and low C:N ratio. The greatest losses in 13C humus occurred in soils with a combination of relatively high MBC and low total N or increasing C:N ratio. We conclude that soil variables involved in soil ecological stoichiometry exert a greater relative influence on incorporating organic matter as humus compared to plant molecular structure and soil physical properties. Furthermore, we conclude that the effect of N fertilisation on humus retention is dependent upon soil ecological stoichiometry.

Plant-derived compounds stimulate the decomposition of organic matter in arctic permafrost soils

Arctic ecosystems are warming rapidly, which is expected to promote soil organic matter (SOM) decomposition. In addition to the direct warming effect, decomposition can also be indirectly stimulated via increased plant productivity and plant-soil C allocation, and this so called "priming effect" might significantly alter the ecosystem C balance. In this study, we provide first mechanistic insights into the susceptibility of SOM decomposition in arctic permafrost soils to priming. By comparing 119 soils from four locations across the Siberian Arctic that cover all horizons of active layer and upper permafrost, we found that an increased availability of plant-derived organic C particularly stimulated decomposition in subsoil horizons where most of the arctic soil carbon is located. Considering the 1,035 Pg of arctic soil carbon, such an additional stimulation of decomposition beyond the direct temperature effect can accelerate net ecosystem C losses, and amplify the positive feedback to global warming.

Temporal variation of delta C-13 in particulate organic matter and oyster Crassostrea gigas in Marennes-Oleron Bay (France): Effect of freshwater inflow

The temporal variability of delta(13)C in suspended particulate organic matter (POM) and oyster Crassostrea gigas along a salinity gradient was investigated from May 1992 to September 1993 within the estuarine bay of Marennes-Oleron (France). During this period the mean daily discharge of the Charente River exhibited large seasonal variation, with a high discharge from November 1992 to January 1993. Contrary to that at the river mouth and the marine littoral, delta(13)C in POM and in oysters at mid-estuary was affected by the high flood period. The delta(13)C values of POM decreased in mid-estuary and remained at low levels during the high discharge period, indicating an increasing contribution of terrestrial inputs to the estuarine POM pool. At the same site, a remarkable decrease of delta(13)C in oysters occurred between December 1992 and March 1993 (after a time lag compared to the ambient POM), indicating incorporation of terrestrial organic matter in oyster tissues during the high flood discharge. The lag between the delta(13)C decrease in POM and oysters is attributed to the time needed for oyster tissues to incorporate enough newly terrestrial light carbon to be recognized by the delta(13)C measure (about 1 to 2 mo). This time interval depends on tissue turnover time. The delta(13)C POM decrease (i.e. 1.3 parts per thousand) cannot explain entirely the decrease observed in oysters (i.e. 2.3 parts per thousand). In fact, the pattern exhibited by mid-estuarine oysters can be explained by the increasing contribution of terrestrial organic matter to their feeding, and the inability to preferentially utilize specific components of the estuarine POM that are C-13-enriched.

Organic Matter Removal from Piggery Wastewater in Waste Stabilisation Pond in Nigeria

Four (4) wastewater quality variables: chemical oxygen demand (COD), total solid (TS), total dissolved solid (TDS), and total suspended solid (TSS) were determined. Analysed samples comprises of raw influent and effluents entering and leaving the stabilisation ponds. Significant reduction in variables were obtained, maximum and minimum values obtained for COD were 917mg/l (anaerobic pond), and 13mg/l (maturation pond). For TS, TDS and TSS, maximum and minimum values obtained were 14,420mg/l, 9,180mg/l, 5,240mg/l and 3,398mg/l, 3,120mg/l, 278mg/l respectively. Removal efficiencies recorded for parameters in final effluent (maturation pond) were 98.55% (COD), 76.44% (TS), 66.01% (TDS), and 94.69% (TSS) respectively.

Release of available nitrogen from river-discharged dissolved organic matter by heterotrophic bacteria associated with the cyanobacterium Microcystis aeruginosa

The use of riverine dissolved organic matter by the heterotrophic bacteria associated with a culture of the cyanobacterium Microcystis aeruginosa and release of simple nitrogen compounds were studied in an experimental series. Bacteria reduced the bulk of dissolved organic nitrogen (DON) by half, but when associated with M. aeruginosa, DON was excreted and its concentration rose by 13%. During the stationary growth phase bacteria released ammonium, doubling the concentration of ammonia as well as of nitrates. Bacteria associated with M. aeruginosa consumed riverine DON and joined the ammonification and nitrification process, supplying cyanobacteria with simple nitrogen compounds.

Non chemical natural organic matter removal with a contact TiO2 process

Dissertação de Mestrado, Tecnologia dos Alimentos, Instituto Superior de Engenharia, Universidade do Algarve, 2014

Carbon in humic fractions of organic matter in soil treated with organic composts under mango cultivation.

Soil organic matter (SOM) plays a key role in maintaining the productivity of tropical soils, providing energy and substrate for the biological activity and modifying the physical and chemical characteristics that ensure the maintenance of soil quality and the sustainability of ecosystems. This study assessed the medium-term effect (six years) of the application of five organic composts, produced by combining different agro-industrial residues, on accumulation and chemical characteristics of soil organic matter. Treatments were applied in a long-term experiment of organic management of mango (OMM) initiated in 2005 with a randomized block design with four replications. Two external areas, one with conventional mango cultivation (CMM) and the other a fragment of regenerating Caatinga vegetation (RCF), were used as reference areas. Soil samples were collected in the three management systems from the 0.00-0.05, 0.05-0.10, and 0.10-0.20 m layers, and the total organic carbon content and chemical fractions of organic matter were evaluated by determining the C contents of humin and humic and fulvic acids. Organic compost application significantly increased the contents of total C and C in humic substances in the experimental plots, mainly in the surface layer. However, compost 3 (50 % coconut bagasse, 40 % goat manure, 10 % castor bean residues) significantly increased the level of the non-humic fraction, probably due to the higher contents of recalcitrant material in the initial composition. The highest increases from application of the composts were in the humin, followed by the fulvic fraction. Compost application increased the proportion of higher molecular weight components, indicating higher stability of the organic matter.