Organic matter characteristics of a rapidly eroding permafrost cliff in NE Siberia (Lena Delta, Laptev Sea region)

Organic carbon (OC) stored in Arctic permafrost represents one of Earth’s largest and most vulnerable terrestrial carbon pools. Amplified climate warming across the Arctic results in widespread permafrost thaw. Permafrost deposits exposed at river cliffs and coasts are particularly susceptible to thawing processes. Accelerating erosion of terrestrial permafrost along shorelines leads to increased transfer of organic matter (OM) to nearshore waters. However, the amount of terrestrial permafrost carbon and nitrogen as well as the OM quality in these deposits are still poorly quantified. Here, we characterise the sources and the quality of OM supplied to the Lena River at a rapidly eroding permafrost river shoreline cliff in the eastern part of the delta (Sobo-Sise Island). Our multi-proxy approach captures bulk elemental, molecular geochemical and carbon isotopic analyses of late Pleistocene Yedoma permafrost and Holocene cover deposits, discontinuously spanning the last ~52 ka. We show that the ancient permafrost exposed in the Sobo-Sise cliff has a high organic carbon content (mean of about 5 wt%).We found that the OM quality, which we define as the intrinsic potential to further transformation, decomposition, and mineralization, is also high as inferred by the lipid biomarker inventory. The oldest sediments stem from Marine Isotope Stage (MIS) 3 interstadial deposits (dated to 52 to 28 cal kyr BP) and is overlaid by Last Glacial MIS 2 (dated to 28 to 15 cal ka BP) and Holocene MIS 1 (dated to 7–0 cal ka BP) deposits. The relatively high average chain length (ACL) index of n-alkanes along the cliff profile indicates a predominant contribution of vascular plants to the OM composition. The elevated ratio of iso and anteiso-branched FAs relative to long chain (C ≥ 20) n-FAs in the interstadial MIS 3 and the interglacial MIS 1 deposits, suggests stronger microbial activity and consequently higher input of bacterial biomass during these climatically warmer periods. The overall high carbon preference index (CPI) and higher plant fatty acid (HPFA) values as well as high C / N ratios point to a good quality of the preserved OM and thus to a high potential of the OM for decomposition upon thaw. A decrease of HPFA values downwards along the profile probably indicates a relatively stronger OM decomposition in the oldest (MIS 3) deposits of the cliff. The characterisation of OM from eroding permafrost leads to a better assessment of the greenhouse gas potential of the OC released into river and nearshore waters in future, which is important to understand the consequences of a warming climate in Arctic environments on the global carbon cycle.

Combination of Coagulation–Flocculation–Decantation and Ozonation Processes for Winery Wastewater Treatment

This research assessed a novel treatment process of winery wastewater, through the application of a chemical-based process aiming to decrease the high organic carbon content, which represents a difficulty for wastewater treatment plants and a public health problem. Firstly, a coagulation–flocculation–decantation process (CFD process) was optimized by a simplex lattice design. Afterwards, the efficiency of a UV-C/ferrous iron/ozone system was assessed for organic carbon removal in winery wastewater. This system was applied alone and in combination with the CFD process (as a pre- and post-treatment). The coagulation–flocculation–decantation process, with a mixture of 0.48 g/L potassium caseinate and 0.52 g/L bentonite at pH 4.0, achieved 98.3, 97.6, and 87.8% removals of turbidity, total suspended solids, and total polyphenols, respectively. For the ozonation process, the required pH and ferrous iron concentration (Fe2+) were crucial variables in treatment optimization. With the application of the best operational conditions (pH = 4.0, [Fe2+] = 1.0 mM), the UV-C/ferrous iron/ozone system achieved 63.2% total organic carbon (TOC) removal and an energy consumption of 1843 kWh∙m−3∙order−1. The combination of CFD and ozonation processes increased the TOC removal to 66.1 and 65.5%, respectively, for the ozone/ferrous iron/UV-C/CFD and CFD/ozone/ferrous iron/UV-C systems. In addition, the germination index of several seeds was assessed and excellent values (>80%) were observed, which revealed the reduction in phytotoxicity. In conclusion, the combination of CFD and UV-C/ferrous iron/ozone processes is efficient for WW treatment.

Spatial variability of fertility status in soils of Dima Hasao district of Assam

Two hundred fifty geo-referenced surfaces (0-15 cm) soil samples were collected and analysed for macronutrients and micronutrients to study fertility status in soils of Dima Hasao district of Assam and their relationship with some important soil properties. Soils of the district were found to be extremely acidic to slightly acidic in reaction with a low to high organic carbon content and low in cation exchange capacity. The soil of the district indicated that the available nitrogen, phosphorus and potassium status was observed to the tune of 14.0 %,7.2% and 67.2% under low and 86.0 %, 92.8 % and 32.8 %under medium categories, respectively. The overall percent deficient of exchangeable calcium, magnesium and available sulphur in soils was 25.6, 30.4 and 6.8 %, respectively. Based on critical limit, all soils were adequately supplied with DTPA-extractable Fe, Mn and Cu content. In respect of zinc and boron, soils exhibited 90.4 and 73 per cent under sufficient, while, 2.4 and 12 per cent were found deficient in DTPA -Zn and HWS-B, respectively. Soil pH and EC showed positive correlation with macro nutrients and negative correlation with micronutrients. The macro- and micronutrient showed significant positive relation with soil organic carbon and cation exchange capacity.

The role of pedogenesis and natural fertiliser as vectors for essential metal content in agricultural topsoils, Central India

Essential trace metals are well known for their environmental toxicity and for being part of complex bio-chemical cycles. Their role as critical micronutrients, delivering vital health benefits, is less widely discussed and understood, holding back strategies for combatting malnutrition. Crops grown on many Indian soils suffer from deficiencies in essential metals, notably iron (Fe), zinc (Zn), and molybdenum (Mo). The list of deficient metals will likely grow due to increasing future crop demand. Geostatistical analysis of soils and farmyard manure (FYM), the predominant fertiliser, implies that residual oxide minerals carry high concentrations of the essential trace metals Fe, Zn, copper (Cu), chromium (Cr), nickel (Ni), cobalt (Co), manganese (Mn) not only in soil but also in FYM (especially Fe, Cr, Cu, Co and Ni). A geochemical survey across a road traverse of 600 km, encompassing an area of c. 15,000 km2, was conducted in Central India to evaluate reported essential metal deficiency in key agricultural topsoils. Importantly, our evaluation of the element cycling in this system reveals that despite high bulk concentrations, some key metals remain bio-unavailable. In effect, the existence of refractory (weathering-resistant) oxides is likely a significant factor for deficiency symptoms in the soil–plant-fertiliser cycle. Further, mass balance calculations of the bioavailable pool of metals imply that only Fe and Mn are present in sufficient quantities to combat deficiency problems. Notwithstanding this limitation of FYM, its high organic carbon content, as well as its importance for Zn, Cu and Fe, validates its traditional use to maintain the fertility and physical condition of Indian topsoils.

Characterisation and classification of arecanut-growing soils of Karnataka

The present investigation was carried out to characterise the soils of areca based cropping system considering soil type and agro-climatic variability. Ten typical soil profiles were studied representing five different agro-climatic zones (ACZs) of Karnataka, namely, Tumkur and Hesarghatta (Eastern Dry Zone), T. Narasipura and Maddur (Southern Dry Zone), H D Kote and Hassan (Southern Transition zone), Mudigere and Sirsi (Hilly Zone), and Belthangady and Kumata (Coastal Zone). These pedons were studied for their morphological characteristics, physical and physicochemical properties. The arecanut-growing soils of Karnataka are generally deep to very deep, non-gravelly and well-drained soils. Texture ranged from sandy clay loam to clay in sub-surface. Soils of coastal and hilly zones were strongly acidic and had high organic carbon. In contrast, other sites of the southern transition zone to southern and eastern dry zone soils were near neutral to moderately alkaline with medium to high organic carbon content. Cation exchange capacity (CEC) ranged 2.5 to 32.6 cmol (p+) kg-1 base saturation varied 21.9 to 99.6 per cent. The major taxa of the soils identified at sub-group level of soil taxonomy were Rhodic Kanhaplustalfs, Typic Haplustalfs, Rhodic Paleustalfs, Typic Rhodustalfs, Vertic Haplustepts, Typic Haplustepts, Ustic Kanhaplohumults, Kanhaplic Haplustults and Typic Paleustults.

Mid- and Late Holocene hydrological and geochemical changes in Lake Chokrak (NE Crimea)

<p>The Crimean Peninsula has around 50 saline lakes, which formed during the Holocene marine transgression. These lakes are valuable archives of the Holocene sea-level changes in the Black Sea, but their chronologies and evolution remain largely unknown. This study presents reconstructions of evolution of the Lake Chokrak basin and its depositional environment during the last 8000 years. At present, the lake is hypersaline and separated from the Sea of Azov by a narrow sandbar. The environmental reconstructions are based on multi-proxy data including shell content, organic geochemical and x-ray fluorescence analyses and radiocarbon dating of an 11-m sediment core. The aim of the study is to provide new insights into the evolution history of the lake in the region where such data are limited. Based on the interpretation, the following succession of stages was recognized in the lake evolution. Around 8000 cal yr BP, an open relatively shallow marine embayment existed in the study area, which is evidenced by high contents of Mn, indicating well-oxygenated waters, and presence of shells of <em>Cerastoderma edule</em>, which is favoured by shallow calm waters. Lamination of the sediments during this stage indicates relatively stable marine conditions. A deeper transgressive stage is observed from 7000 to 6500 cal yr BP when waters became less oxygenated, the grain size decreased and laminations disappeared. Precipitation of carbonates at the end of this stage indicates seawater evaporation. A dry stage from 6500 to 6200 cal yr BP is characterized by further decrease in water level and precipitation of gypsum. Starting from 6200 cal yr BP, a renewed transgressive stage is observed with increased water oxygenation, accumulation of fine sediments and precipitation of carbonates. From 5400 to 5000 cal yr BP higher erosion is demonstrated by an increase in Zr, Ti, Rb and Si contents and occurrence of sand layers in the sediment core. After 5000 cal yr BP starts a dry stage of the basin, which is connected to the slower rate of the Holocene sea transgression. Precipitation of evaporites (carbonates, halite, gypsum) increased at this time and fine-grained clays accumulated in the basin. This stage is also characterized by virtually continuous presence of <em>C. edule</em> shells. Relatively high organic carbon content and C/N ratios imply increased input of terrestrial organic material throughout this stage. The infilling of the basin and formation of the sandbar started around 3000 cal yr BP when clay sediments intermixed with sand layers. A transitional stage from semi-open to closed basin lasted from 1400 to 800 cal yr BP and it is characterized by precipitation of evaporites and disappearance of shells. The current stage (from 800 cal yr BP to present) of the closed lake basin is characterized by sediment lamination, high precipitation of gypsum and potassium salts, and complete absence of molluscs due to high salinity of the brine. The obtained results show that hydrological regime and geochemical composition of the lake were influenced by complex interaction of climatic, local tectonic and eustatic factors throughout its history.</p>

Effect of biomass cutting on soil CO2 efflux in a sandy grassland

<p>Carbon storage in grassland ecosystems is realized mostly belowground. The changes in the management activities of grasslands also influence the below-ground carbon stocks. Soil carbon-dioxide efflux (Rs) takes a major part of the ecosystem’s carbon cycle. R<sub>s</sub> includes the respiration of different components. Rs gives 60-80% of ecosystem respiration or 40-60% of gross primary production. It is known from the literature that respiration is affected by abiotic (temperature (Ts), soil water content (SWC)) and the biotic factors.</p><p>In our study we investigated the biotic one, namely the belowground carbon allocation on soil respiration. The study was performed in a semi-arid sandy grassland at Bugac (Kiskunság National Park, Hungary). The vegetation of the pasture was dominated by Festuca pseudovina, Carex stenophylla and Cynodon dactylon and the soil is a chernozem type soil with high organic carbon content.</p><p>The soil CO<sub>2</sub> effluxes were measured continuously by an automated soil respiration system consisted of 10 soil respiration chambers. The chambers measured 3 different experimental plots. Data was collected in every half-hour from each chamber for 6 days before the cutting event. After the cutting data was recorded from 1) non-cut, 2) half cut and 3) completely removed treatments also for 6 days. The study was repeated under laboratory conditions (constant temperature, illumination, humidity) on grass patches planted in pots. We observed that the respiration in half cut and completely removed treatments increased after they were cut off. The proportion of respiration after cutting in the completely removed treatment reduced to 85% compared to the control one. Our results highlight that the soil respiration is largely affected by belowground carbon allocation.</p>

Adsorption Isotherms of Diuron and Hexazinone in Drinking Water Using Four Agro-Industrial Residues

ABSTRACT: Materials with high organic carbon content are studied for the removal of herbicides from water, such as activated carbon. Low cost alternatives should be investigated for the substitution of this type of material in the removal of herbicides from water. In this context, the aim of this research was to evaluate four agro-industrial residues (white grape bagasse, corn straw, peanut shell and soybean hull) as adsorbents of diuron and hexazinone in drinking water. Samples of drinking water were collected from sources used for human consumption. Five concentrations (1, 2, 3, 4 and 5 mg mL-1) of each herbicide were added to the potable water samples. Each experimental unit consisted of 10 mL of a solution of water and herbicide with 0.1 g of each agro-industrial residue. Sorption was evaluated using the batch equilibrium method. High performance liquid chromatography (HPLC) was used to determine the amount of herbicide present in the aqueous solution. The Kf (Freundlich coefficient) of diuron was higher (2.99-11.93 mmol(1-1/n) L1/n kg-1) than hexazinone (2.31-4.61 mmol(1-1/n) L1/n kg-1) for all adsorbents used. Diuron percentage sorption was higher with white grape bagasse (51.15%) and peanut husk (52.44%), and hexazinone with corn straw (22.77%) and white grape marc (21.48%), than other agro-industrial waste for both herbicides. Even though the sorption of diuron was more pronounced than that of hexazinone, the sorption values obtained in this study were less than 52.44% and considered unsatisfactory in terms of effective removal from contaminated water.

The deep structure of the Nepa‐Peleduy arch of the Nepa‐Botuoba anteclise in the development of B.A. Sokolov's hypothesis

The studies were conducted in the territory of the Nepa‐Peleduy arch (NPA) of the Nepa‐Botuoba anteclise (NBA), which is strategically important for the Russian Federation as it contains large and unique hydrocarbon fields, including those essential for the ESPO oil pipeline and the presently under‐construction Power of Siberia gas pipeline. Because the hydrocarbon potential of the sedimentary cover is largely exhausted, the aim is now to increase the regional stocks. Verifying the hypothesis of the Corresponding Member of the Russian Academy of Sciences B.A. Sokolov, stating that the allochthonous block of the crystalline basement, overlapping the aulacogen Riphean sediments, lies at the base of the NPA, would open the possibility of increasing the hydrocarbon reserves in the ‘subbasement’ formations. It would also clarify the controversial nature of the NPA deposits, which have no sediments with a high organic carbon content. In this study, we present a Hilbert transform of a time section of the common midpoint method (CDP) from a fragment of the Batholith‐1 geotraverse passing through the Katanga saddle, the NPA and the Pre‐Patom trough, as well as geophysical materials and well data from the same profile. Supporting B.A. Sokolov’s hypothesis, we confirm the existence of a relict crystalline terrane crosscut by the wells at the base of the NPA and forming the roof of the underlying lower Vendian and Riphean sediment units. Our data clearly document the position of the western side of the inverted paleorift, the thickness of the terrane and the physical characteristics of the underlying sediments. These results are justifying hydrocarbon exploration of the ‘subbasement’ sediments.

Fast immersion to test the stability of aggregates in water: consequences for interpreting results from tropical soil classes

Aggregates are the primary structural components of soil and have been used as an indicator of soil quality in conservation systems. The objective of this study was to analyse the effect of slow pre-wetting on the results of the aggregate stability test for different classes of tropical soils. Data were arranged in a 2 x 4 factorial design with three replications, in which the first factor comprised the two methods of pre-treatment on soil aggregates: without pre-wetting (WOPW), which considered the moisture of the aggregates in the field, and with pre-wetting (WPW), which considered the slow wetting of aggregates through capillarity on wet filter paper for 24h. The second factor consisted of four soil classes: Typic Dystrustept (Cambissolo Aplico distrófico in Embrapa), Typic Hapludult (Argissolo Amarelo distrófico), Rhodic Kandiudult (Nitossolo Vermelho distrófico), and Anionic Acrudox (Latossolo Vermelho distróferrico) and considered horizons A and B. The pre-wetting significantly increased the values of the weighted average diameter, geometric mean diameter and aggregate stability index. In soils with high organic carbon content, the practice of pre-moistening did not provide variation in aggregation.