Characterization Of Organic Matter Research Articles

Novel insight into arsenic enrichment in aquifer sediments under different paleotemperatures from a molecular-level characterization of sedimentary organic matter

The heterogeneous distribution of As in sediments is governed by the abundance and type of SOM, which is closely associated with the depositional environment. However, few studies have revealed the effect of depositional environment (e.g., paleotemperature) on As sequestration and transport in sediments from the perspective of the molecular characteristics of sedimentary organic matter (SOM). In this study, we characterized the optical and molecular characteristics of SOM coupled with organic geochemical signatures to illustrate in detail the mechanisms of sedimentary As burial under different paleotemperatures. We identified that alternating paleotemperature changes result in the fluctuation of H-rich and H-poor organic matter in sediments. Further, we found aliphatic and saturated compounds with higher nominal oxidation state of carbon (NOSC) values predominate under high-paleotemperature (HT) conditions, while polycyclic aromatics and polyphenols with lower NOSC values accumulate under low-paleotemperature (LT) conditions. Under LT conditions, thermodynamically favorable organic compounds (higher NOSC values) are preferentially degraded by microorganisms to provide sufficient energy to sustain sulfate reduction, favoring sedimentary As sequestration. Under HT conditions, the energy gained from the decomposition of low NOSC value organic compounds approaches the energy required to sustain dissimilatory Fe reduction, leading to sedimentary As release into groundwater. This study provides molecular-scale evidence of SOM that indicates LT depositional environments favor sedimentary As burial and accumulation.

Characteristics of dispersed organic matter in the Inoceramian Beds from the Dukla Unit

Scharakteryzowano skład i dojrzałość rozproszonej materii organicznej w warstwach inoceramowych jednostki dukielskiej na obszarze polskiego fragmentu Karpat zewnętrznych. Podstawą dokonanej charakterystyki były wyniki obserwacji mikroskopowych w świetle odbitym, połączonych z analizą refleksyjności witrynitu. Uzupełniająco na wybranych próbkach przeprowadzono pirolizę Rock-Eval. Prace terenowe objęły 23 odsłonięcia, z których pobrano i przebadano w sumie 85 próbek, reprezentujących warstwy ciśniańskie, łupkowskie oraz – odsłaniające się w zachodniej części obszaru badań – warstwy inoceramowe (nierozdzielone). Skład macerałowy przebadanych próbek jest stosunkowo monotonny. W analizowanych skałach dominuje materiał witrynitowo-inertynitowy, zwykle z niewielkim dodatkiem macerałów grupy liptynitu. Macerały grupy witrynitu reprezentowane są przez większe, przeważnie wydłużone fragmenty kolotelinitu oraz drobne fragmenty witrodetrynitu. Ich łączny udział sięga maksymalnie 14% obj., przy czym zwykle nie przekracza 1% obj. Obserwowane macerały grupy inertynitu to w głównej mierze ostrokrawędziste fragmenty semifuzynitu i fuzynitu oraz drobny inertodetrynit, których udział najczęściej nie przekracza 2% obj. Macerały grupy liptynitu są najmniej licznie reprezentowaną grupą. Obserwuje się głównie alginit (lamalginit) oraz rzadziej sporynit, kutynit i liptodetrynit. Udział materii organicznej (wyznaczony na podstawie parametru TOC) mieści się w zakresie od 0,3% do 5,6%, przy czym w przypadku ¾ próbek nie przekracza 2%. Jest to materia organiczna reprezentująca III i IV typ kerogenu. Dojrzałość materii organicznej określono na podstawie pomiarów refleksyjności witrynitu (Ro) oraz za pomocą parametru Tmax. Oba parametry wskazały na stopień przeobrażenia termicznego badanych utworów na poziomie okna ropnego – od jego wczesnej fazy, poprzez fazę główną, aż do fazy późnej. Obserwuje się regionalny trend zmienności opisywanych parametrów Ro i Tmax, wskazujący na wyższą dojrzałość utworów w części wschodniej badanego obszaru. Przebadane próbki charakteryzują się najczęściej niskim potencjałem generacyjnym i nie są dobrymi skałami macierzystymi.

Sustainable Use of Organic Matter Obtained from the Bottom of a Post-Mining Pit Reservoir—A Case Study on the Creation of Raduszyn Lake in Poland

According to historical sources, a watermill existed in the valley of the Trojanka River on the north-western shore of Raduszyn Lake from the 15th century. Its dams lasted for centuries causing the water flow through the Raduszyn reservoir to slow down and deposit various mineral fractions in it. The aim of paper was to develop a scientific background for the sustainable management of organic matter extracted from the peat top and from deeper layers that are unsuitable for direct use, that is, decomposed peat. A SWOT (strengths, weaknesses, opportunities, threats) analysis was used to describe ways of restoration of the water reservoir alongside the characterization of organic matter and the financial condition of the studied enterprise. For the use of the studied material as a homogeneous substrate for plant cultivation, the contents of nitrogen, phosphorus, potassium, and copper were insufficient, whilst calcium was excessive. Microbiological analyses of the organic materials intended as an additive for horticultural substrates confirmed the presence of plant growth-promoting bacteria. The occurrence of such microorganisms in the substrate can limit the use of mineral fertilizers and chemical plant protection products. The results of the research can be an example for enterprises restoring or creating water reservoirs by extraction of organic matter, which is often considered as waste that generates costs and does not bring financial benefits. Such a measure can be used to improve the efficiency of water reservoir restoration enterprises and at the same time contribute to sustainable land development.

Enrichment of geogenic phosphorus in a coastal groundwater system: New insights from dissolved organic matter characterization

High concentrations of geogenic phosphorus (P) in coastal aquifer systems pose a serious and continuous threat to the health of marine ecosystems. A major source for geogenic P enrichment in aquifer systems is the mineralization of P-containing organic matter. However, the mechanisms that drive the enrichment remain unclear. Therefore, our study sought to characterize the occurrence, sources, and enrichment mechanisms of geogenic P in a coastal confined aquifer system of the Pearl River Delta, southern China. To achieve this, we conducted Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and fluorescence excitation-emission-matrix spectra (EEMs) as well as hydrochemistry and stable carbon isotope analyses. Our findings indicated that intense degradation of P-containing organic matter produced up to 8.07 mg/L of geogenic P in a reducing environment with abundant organic matter. The dissolved organic matter (DOM) of high-P groundwater (P > 1 mg/L) contained more humic-like fluorophores and exhibited higher humification. Groundwater with high P concentrations contained more aliphatic compounds and highly unsaturated-low O compounds, and the enrichment of P was mostly associated with CHOP compounds in the region of aliphatic compounds and CHON2P compounds in the region of highly unsaturated-low O compounds. Different types of dissolved organic phosphorus (DOP) can be mineralized into P, and even the mineralization of phosphonates takes precedence over the more unstable phosphate esters. P produced by the metabolism of different types of DOP was assimilated by marine microorganisms (e.g., heterotrophic bacteria and archaea), and the newly synthesized organic P compounds by chemosynthesis were subsequently released into the groundwater. Over time, P continues to be enriched in the aquifer system. This study provides new insights into subsurface P cycling in coastal aquatic systems.

Unveiling the Role of Dissolved Organic Matter on the Hg Phytoavailability in Biochar-Amended Soils.

Biochar can effectively reduce the phytoavailability of mercury (Hg) in soil, but the mechanisms are not fully understood. In this study, the dynamic changes in Hg content adsorbed by the biochar (BC-Hg), Hg phytoavailability in the soil (P-Hg), and soil dissolved organic matter (DOM) characteristics were determined over a 60-day treatment period. Biochar obtained at 300 °C, 500 °C and 700 °C reduced the P-Hg concentration assessed by MgCl2 extraction by 9.4%, 23.5% and 32.7%, respectively. However, biochar showed a very limited adsorption on Hg, with the maximum BC-Hg content only accounting for 1.1% of the total amount. High-resolution scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) results showed that the proportion of Hg atoms in biochar after 60 d was barely detectable. Biochar treatment can shift soil DOM toward higher aromatic content and molecular weight. Additionally, the addition of high-temperature biochar increased more humus-like components, but low-temperature biochar increased more protein-like components. Correlation analysis and partial least squares path modeling (PLS-PM) showed that biochar promoted humus-like fractions formation to reduce the Hg phytoavailability. This research has deepened the understanding of the mechanisms by which biochar stabilizes Hg in agricultural soils.

Erratum: Precipitation-derived effects on the characteristics of proteinaceous soil organic matter across the continental United States

ERRATUM article Front. Soil Sci., 14 February 2023Sec. Soil Biogeochemistry & Nutrient Cycling Volume 3 - 2023 | https://doi.org/10.3389/fsoil.2023.1143273

Sampling terrigenous diffuse sources in watercourse: Influence of land use and hydrological conditions on dissolved organic matter characteristics

Diffuse and point sources of dissolved organic matter (DOM) in streams influence its composition, interactions and fate in the aquatic ecosystem. These inputs can be very numerous at the scale of a watershed, and their identification remains a challenge, especially for diffuse sources related to land use. The complexity of the transfer mechanisms and the reactivity of DOM throughout the soil-water column continuum raise questions about the sampling of diffuse sources in watercourses. To answer this issue, we compared the characteristics of soil-extracted DOM influenced by a particular land use (homogenous sub-catchment of forest and vineyard) and DOM collected from the watercourse adjacent to the soil samples. A 28-day incubation experiment of soil extracts was designed to remove the labile fraction of DOM. During the first 3 days, between 40 and 70 % of the DOC mass was lost for both types of soils. A set of optical indicators (UV–Visible, EEM fluorescence and HPSEC/UV-fluorescence) showed that the labile fraction was mostly composed by low (<1 kDa) and high (>10 kDa) protein-like molecules. At the end of the incubation, soil-extracted DOM was mainly composed of medium molecules (1–10 kDa) associated to terrigenous humic-like compounds. Its optical and size molecular signature tended towards that in the adjacent watercourses and was specific to land use. However, the characteristics of DOM in watercourses was also influenced by the hydrological conditions, probably due to a transfer of top soil DOM during high water periods and both deep soil and autochthonous DOM during low water periods. These results were obtained by a set of indicators, including novel ones derived from HPSEC/UV-fluorescence. Finally, this study demonstrated that it is possible to sample the DOM representative of a land use directly in the river downstream of the homogeneous sub-basin by multiplying the samples during contrasting hydrological conditions.

Rock–Fluid Interactions of Alkyl Ether Carboxylate Surfactants with Carbonates: Wettability Alteration, ζ-Potential, and Adsorption

This work evaluated the rock–fluid interactions of two linear alkyl ether carboxylate (AEC) surfactants C11E11A and C12E7A in carbonates: wetting ability, ζ-potential, and adsorption capacity. Contact angle measurements showed that the ability of AECs to hydrophilize the surface is strongly affected by the ethylene oxide (EO) chain length and the presence of electrolytes. An AEC with a shorter EO chain C12E7A demonstrated a better wetting ability and decreased the contact angle value on the limestone surface from 113 to 27 ± 11° in deionized (DI) water and until 17 ± 5° in 5 wt % NaCl. The mechanism of surfactant action was assessed through thermodesorbed hydrocarbon analysis and organic matter characterization with the help of the Rock-Eval (RE) pyrolysis technique for the first time. The analysis results revealed that all surfactant compositions partially removed free oil and heavy oil components from limestone samples. Also, the presence of C12E7A molecules was detected in the samples after surfactant treatment that indicates that a better wetting ability is achieved by the combination of washing hydrocarbons and adsorption of surfactants on clean sites. The combination of ζ-potential measurements and static adsorption test on crushed limestone demonstrated that the adsorption of AECs in deionized water is not governed by electrostatic interactions and mainly occurs due to hydrogen bonding. Salinity has a significant effect on the adsorption behavior of AECs and leads to the partial destruction of hydrogen bonds and the shift from monomolecular adsorption in DI water to polymolecular adsorption in brines. The adsorption of C11E11A achieved ∼9 mg/g-rock and was higher than that of C12E7A, showing a maximum value of ∼4 mg/g-rock. This work provides a set of experiments that characterize the behavior of AECs during interactions with carbonate rock and describes a novel approach of the wettability shift mechanism assessment through RE pyrolysis.

Effect of cover cropping on soil organic matter characteristics: Insights from a five-year field experiment in Nebraska

Cover crops are increasingly incorporated into crop rotations to improve soil health including the postulated positive impact on soil organic carbon (SOC) storage. However, a consistent positive response of SOC to cover cropping was not observed in several studies, necessitating further clarification of mechanisms by which cover crops impact soil organic matter (SOM) dynamics. In this study, we evaluated the effect of five years of winter cover cropping within a corn-soybean rotation in Nebraska under no-till on SOC and nitrogen (N) storage in the bulk topsoil (0–10 cm depth) as well as in particulate (free and occluded), water-extractable, and mineral-associated organic matter fractions. Furthermore, cover crop effects on potential C and N losses from the topsoil in form of CO2 and N2O emissions and leached organic C and N were evaluated. The different SOM fractions were analyzed for their functional group composition using diffused reflectance infrared Fourier transform spectroscopy to account for potential changes in the SOM composition due to cover crops. Our results indicated no effect of cover cropping on C and N losses (gaseous and leaching) and on bulk SOC and total N storage five years after implementation. Differences were detected for the SOM fractions, with a positive effect of cover crops on the amount of water-extractable organic matter. The spectroscopic results suggested a significant cover crop effect on the composition of free particulate organic matter fraction. Both fractions seem to be suitable for detecting early changes in SOM characteristics due to cover cropping under the studied conditions. A significantly measurable impact on bulk SOC and N storage in 0–10 cm depth for the studied corn-soybean systems might require more than five years of cover cropping, or management changes that target an increase in cover crop biomass production and input into the soil.

Effects of adding different carbon sources on the microbial behavior of sulfate-reducing bacteria in sulfate-containing wastewater

Excessive sulfate levels pose a threat to the environment and human health. To address the problem of sulfate pollution and provide a basis for sulfate removal and sulfur recovery, this study searched for organics readily available to sulfate-reducing bacteria (SRB). To investigate the utilization characteristics of different organic matter by SRB, this study investigated microbial sulfate reduction under different carbon sources, including alcohols, small organic acids and sugars, and at different carbon-sulfur (C/S) ratios. Differences in the conversion pathways of different carbon sources were the main factors affecting the sulfate reduction process. Due to the presence of incompletely oxidizing SRB (incomplete oxidizers), the rapid incomplete oxidation of sugars and alcohols that produced acetic acid inhibited the activity of SRB by lowering the solution pH. In contrast, the conversion of small organic acids with stable pH produced more sulfides. Among all the tested carbon sources, faster sulfate reduction was observed using propionate, lactate, ethanol and formate, and the optimal C/S ratio was three times higher than the stoichiometric ratio. The type of carbon source also influenced sulfate reduction by shaping the microbial community. The presence of ethanol and propionate favored the vigorous proliferation of the incomplete oxidizers Desulfomicrobiaceae and Desulfovibrionaceae, while the completely oxidizing SRB Desulfuromonadaceae and Desulfococcaceae dominated formate-containing cultures. Incomplete oxidizers generally grow faster and tend to have higher electron transport system activity but lower carbon source utilization efficiency.

A potential application for life-related organics detection on Mars by diffuse reflectance infrared spectroscopy

Life information searching is a hot point for Mars exploration. Ancient Mars was very likely to reach a habitable environment, and there was a real possibility of arising life on Mars. However, the current Mars has a harsh environment. Under such conditions, life materials on Mars are supposed to have taken the form of relatively primitive microbial or organic residues, which might be preserved in some mineral matrices. Detection of these remnants is of great significance for understanding the origin and evolution of life on Mars. The best detection method is in-situ detection or sample return. Herein, diffuse reflectance infrared spectroscopy (DRIFTS) was used to detect characteristic spectra and the limit of detection (LOD) of potential representative organic compounds with associated minerals. In view of high oxidation due to the electrostatic discharge (ESD) during dust actives on Martian surface. The degradation of organic matter by ESD process was studied under simulated Mars conditions. Our results show that the spectral characteristics of organic matter are significantly different from that of associated minerals. The different organic samples have different mass loss and color change after ESD reaction. And the signal intensity of infrared diffuse reflection spectrum can also reflect the changes of organic molecules after ESD reaction. Our results indicated that the degradation products of organics rather than organic itself are most likely to be founded on current Martian surface.

Predicting the Stability of Organic Matter Originating from Different Waste Treatment Procedures.

Recycling organic wastes into farmland faces a double challenge: increasing the carbon storage of soil while mitigating CO2 emission from soil. Predicting the stability of organic matter (OM) in wastes and treatment products can be helpful in dealing with this contradiction. This work proposed a modeling approach integrating an OM characterization protocol into partial least squares (PLS) regression. A total of 31 organic wastes, and their products issued from anaerobic digestion, composting, and digestion-composting treatment were characterized using sequential extraction and three-dimension (3D) fluorescence spectroscopy. The apportionment of carbon in different fractions and fluorescence spectra revealed that the OM became less accessible and biodegradable after treatments, especially the composting. This was proven by the decrease in CO2 emission from soil incubation. The PLS model successfully predicted the stability of solid digestate, compost, and compost of solid digestate in the soil by using only the characterized variables of non-treated wastes. The results suggested that it would be possible to predict the stability of OM from organic wastes after different treatment procedures. It is helpful to choose the most suitable and economic treatment procedure to stabilize labile organic carbon in wastes and hence minimize CO2 emission after the application of treatment products to the soil.

A Study on the Material Composition and Traceability of the Wellhead Blockage in the Process of Oil and Gas Exploitation—A Case of the DH231 Well in the Tarim Basin, China

The formation of wellhead blockage increases operating costs and seriously affects the safe production of oil wells. It is crucial to correctly analyze the blockage composition and determine the reasons for wellhead blockage to improve the production efficiency of oil wells. In this study, the material composition and origin of the wellhead blockage in Well DH231 are systematically investigated by means of a thin-section observation, scanning electron microscope, energy spectrum analysis, and molecular geochemical characterization of organic matter. The results show that the wellhead blockage in Well DH231 consists of organic and inorganic materials. The inorganic material was mainly composed of dolomite, fine sand, and unknown black minerals. Four elements, Fe, O, Na, and Cl, could account for 95% of the total elemental content in the unknown minerals. It is speculated that they may have come from rust on the metal parts of the inner wall of the wellbore while being influenced by groundwater during the formation process. The organic matter in the blockage was an oil stain from the geological body. The coexistence of n-alkanes and 25-norhopanes in the oil stain was obvious. It indicated that the oldest crude oil in Well DH231 experienced severe biodegradation, followed by the secondary injection of hydrocarbons. The distribution characteristics of hopanes and steranes in oil stains in Well DH231 were comparable to those of the carboniferous crude oil in neighboring Wells DH4 and DH5. The oil stains in the wellhead blockage may be the product of oil and gas migration in Wells DH4 and DH5.

Saline soil organic matter characteristics of aggregate size fractions after amelioration through straw and nitrogen addition

AbstractSaline soil organic matter (SOM) composition and distribution are largely unknown. A coastal field experiment was designed to investigate the effects of straw and nitrogen addition on SOM characteristics by diffuse reflectance Fourier‐transform mid‐infrared (FTIR) spectral and amino sugar analysis. In each growing season, maize/wheat straw was applied at rates of 5.0 × 103 kg ha−1 (S5) and 1.0 × 104 kg ha−1 (S10), and inorganic nitrogen was applied at rates of 75 kg ha−1 (N75), 150 kg ha−1 (N150), and 300 kg ha−1 (N300). N150 without straw addition was the control treatment (CK). Dry‐sieving technique was used to fractionate soils into macroaggregates (&gt;0.25 mm, MA), microaggregates (0.053–0.25 mm, MI), and silt‐plus‐clay particles (&lt;0.053 mm, SC). Results showed that SOM and amino sugar contents were efficiently increased in the S5 and S10 treatments compared with CK, which were significantly higher in MA and MI than in SC (p &lt; 0.05). In straw‐addition treatments, SOM and amino sugar contents were significantly higher in S5N300 and S10N300 (p &lt; 0.05). The contribution of microbial necromass C to soil organic C (SOC) was 8.9–17.1%, and the fungal residue was dominant in bulk and aggregate soils. The amount of recalcitrant form of organic C decreased with SOM content increase, and the abundance of aromatic C groups increased under higher salt stress. Therefore, we suggested that microbial necromass accumulation could not be the main pathway of SOC sequestration, and enriching recalcitrant organic C probably led to SOM stability in saline soils.

Ecological water replenishment to the Yongding River, China: effects of different water sources on inorganic ions and organic matter characteristics.

Ecological water replenishment is considered to be an important project to adjust river ecosystems with water shortages and degradation, and its impact on the water quality of the target river section deserves attention. By investigating the characteristics of inorganic ions and organic components of the Beijing section of the Yongding River (YDR) from upstream to downstream, the sources of inorganic ions and dissolved organic matter (DOM) during an ecological water replenishment event were analysed and discussed. This study illustrated the hydrochemical response to different supplemental water sources in three sections of the YDR (mountain gorge section (MGS), urban plain section (UPS), and suburb plain section (SPS)). The results showed that the total dissolved solids (TDS) and ion concentrations were significantly different (p < 0.001) in the three river sections due to different supplemental water sources. The highest concentration of TDS was found in the UPS (870.92mg/L) replenished by reclaimed water, while the lowest concentration of TDS was found in the SPS (306.95mg/L) replenished by the water of the South-to-North Water Diversion Project (SNWD). Despite the differences in the water sources of replenishment, the optical parameters of DOM and fluorescent components showed similar protein-like dominated endogenous source characteristics in the three river sections of the YDR, which was due to the influence of reservoir water (MGS and SPS) and reclaimed water (UPS). Our study emphasizes the importance of understanding the impact of different water sources on the water replenishment process, which provides a scientific reference for the management of ecological water replenishment.

Transformation characteristics of organic matter and phosphorus in composting processes of agricultural organic waste: Research trends

Agricultural waste is rich in organic matter and an important secondary source of phosphorus, which can be converted into valuable products through various technologies. Composting is an effective way to treat agricultural waste and further produce organic fertilizer, achieving waste minimization and stabilization. This paper reviews the current situation of agricultural waste pollution and composting technology, introduces the parameters that influence of the composting process and the optimal conditions, and presents the indicators for evaluating the decay of compost products and the evaluation criteria as well. In the composting process, small-molecule organic acids produced by the degradation of easily degradable organic matter such as sugars and lipids and various enzymes produced by microorganisms (phytase, phosphatase, etc.) can mineralize organic phosphorus such as phytate and phospholipids, promote phosphorus activation and provide phosphorus sources for microorganisms, so the conversion of organic matter and phosphorus is related to the fertilizer effect of composted products. Therefore, the clarification of the characteristics of organic matter and phosphorus transformation in the composting process is an important prerequisite for the resource utilization of agricultural organic waste. This paper provides theoretical support for the sustainable utilization of agricultural organic waste resources.

Enhanced electrocoagulation process for natural organic matter removal from surface drinking water sources: coagulant dose control &amp; organic matter characteristics

An optimized electrocoagulation process was investigated for enhanced removal of dissolved organic matter for eco-friendly drinking water production from surface water sources. A model-based control system was developed for electro-coagulant dosing.

Using UV–Vis differential absorbance spectra of tropical peat water DOM fraction to determine trihalomethanes formation potential and its estimated cytotoxicity

Absorbance differential spectra could be utilized to identify dissolved organic matter (DOM) characteristics such as the disinfection by products (DBPs) formation. This research purposed to establish the relationship between absorbance differential spectra and trihalomethanes-4 (THM4) formation potential, as well as the estimated cytotoxicity of tropical peat water DOM percentage. The ion exchange resin was used to separate the DOM components from peat water. In addition, the UV–Vis spectrum was examined between 200 and 700 nm. The hydrophobic-acid (HPOA) fraction contains the highest concentration of dissolved organic carbon (DOC), THM4 production potential, and calculated cytotoxicity. On the other hand, the hydrophilic-neutral (HPIN) fraction has the lowest potential THM4 production. The UV–Vis absorbance spectra of all DOM fractions showed a comparable peak at 277 nm. The differential spectra of 277 nm (ΔA277) indicated a significant association with DOC concentration (99.6 %), trichloromethane (TCM) creation (86.6 %), total-THM4 (TTHM4) (81.3 %) formation, THM4 estimated cytotoxicity (89.7 %), and a moderate correlation with bromodichloromethane (BDCM) formation (55.6 %). Meanwhile, ΔA277 had a poor correlation with brominated THM4 formation potential (chlorodibromomethane (CDBM): 2.59, tribromomethane (TBM): 2.78 %). The absorbance differential spectra might be employed as a surrogate measure for the peat water DOM fraction and its precursor properties to form THM4 during the chlorination process, as well as its estimated cytotoxicity.

Quantitative and Qualitative Characteristics of Organic Matter Under Long-Term Exposure to Natural and Anthropogenic Factors

Studies have found that the increase in differences between the amount of energy subsidies invested in agrobiocenoses and alienated from them over a 105-year period changes the direction of biochemical processes of organic matter transformation, which leads to significant losses of organic carbon reserves, which amount to 17.5 t/ha in highly degraded soils, 7.3 t/ha in poorly cultivated soils, and in highly cultivated increases them by 2.8 t /ha, respectively, compared with the initial content. Long-term use of arable land affects the qualitative characteristics of the state of organic matter of sod-podzolic soil, which are expressed in a change in the ratio of the peripheral and central parts, the enrichment of humus with nitrogen. The humus substances of medium (57%) and highly cultivated soils (54%) are characterized by the highest degree of participation of peripheral groupings in the construction, and the least highly degraded (29%).

Biogeochemical and oceanographic conditions provide insights about current status of an Antarctic fjord affected by relatively slow glacial retreat.

Understand the origin, transport, and character of organic matter entering Antarctic fjords is essential as they are major components of the global carbon cycle and budget. Macromolecular pools of particulate organic matter, bulk organic geochemistry, major and trace elements in surface sediments from Collins Bay were analysed as source indicators. Oceanographic conditions, bathymetry (multibeam) and grain size were considered as environmental controlling factors. Sediment samples were taken with a van Veen grab, during the ANTAR XXV Peruvian expedition (February 2018), onboard the R/V "BAP Carrasco" from the Peruvian Navy. Biopolymeric composition revealed the predominance of fresh marine protein-rich organic matter in the seafloor of Collins Bay, denoting high quality food resource for marine benthic heterotrophs. Based on Igeo values (between 0 and 1) Collins Bay can be considered unpolluted with natural levels of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. Distribution of most of these elements with a gradient of decrease from the shallow inner fjord towards the outer deepest fjord, suggest their association with the deposition of detrital material and lithogenic particles supplied by Collins Glacier frontal ablation and runoff. This first comprehensive baseline information would assist in interpreting downcore sedimentary reconstructions and future climate-induce changes.