Organic Matter Components Research Articles

Fluorescent Dissolved Organic Matter Components as Surrogates for Disinfection Byproduct Formation in Drinking Water: A Critical Review.

Disinfection byproduct (DBP) formation, prediction, and minimization are critical challenges facing the drinking water treatment industry worldwide where chemical disinfection is required to inactivate pathogenic microorganisms. Fluorescence excitation-emission matrices-parallel factor analysis (EEM-PARAFAC) is used to characterize and quantify fluorescent dissolved organic matter (FDOM) components in aquatic systems and may offer considerable promise as a low-cost optical surrogate for DBP formation in treated drinking waters. However, the global utility of this approach for quantification and prediction of specific DBP classes or species has not been widely explored to date. Hence, this critical review aims to elucidate recurring empirical relationships between common environmental fluorophores (identified by PARAFAC) and DBP concentrations produced during water disinfection. From 45 selected peer-reviewed articles, 218 statistically significant linear relationships (R2 ≥ 0.5) with one or more DBP classes or species were established. Trihalomethanes (THMs) and haloacetic acids (HAAs), as key regulated classes, were extensively investigated and exhibited strong, recurrent relationships with ubiquitous humic/fulvic-like FDOM components, highlighting their potential as surrogates for carbonaceous DBP formation. Conversely, observed relationships between nitrogenous DBP classes, such as haloacetonitriles (HANs), halonitromethanes (HNMs), and N-nitrosamines (NAs), and PARAFAC fluorophores were more ambiguous, but preferential relationships with protein-like components in the case of algal/microbial FDOM sources were noted. This review highlights the challenges of transposing site-specific or FDOM source-specific empirical relationships between PARAFAC component and DBP formation potential to a global model.

Viral lysing can alleviate microbial nutrient limitations and accumulate recalcitrant dissolved organic matter components in soil.

Viruses are critical for regulating microbial communities and biogeochemical processes affecting carbon/nutrient cycling. However, the role of soil phages in controlling microbial physiological traits and intrinsic dissolved organic matter (DOM) properties remains largely unknown. Herein, microcosm experiments with different soil phage concentrates (including no-added phages, inactive phages, and three dilutions of active phages) at two temperatures (15 °C and 25 °C) were conducted to disclose the nutrient and DOM dynamics associated with viral lysing. Results demonstrated three different phases of viral impacts on CO2 emission at both temperatures, and phages played a role in maintaining Q10 within bounds. At both temperatures, microbial nutrient limitations (especially P limitation) were alleviated by viral lysing as determined by extracellular enzyme activity (decreased Vangle with active phages). Additionally, the re-utilization of lysate-derived DOM by surviving microbes stimulated an increase of microbial metabolic efficiency and recalcitrant DOM components (e.g., SUV254, SUV260 and HIX). This research provides direct experimental evidence that the "viral shuttle" exists in soils, whereby soil phages increase recalcitrant DOM components. Our findings advance the understanding of viral controls on soil biogeochemical processes, and provide a new perspective for assessing whether soil phages provide a net "carbon sink" vs. "carbon source" in soils.

Reductive Sequestration of Cr(VI) and Immobilization of C during the Microbially Mediated Transformation of Ferrihydrite-Cr(VI)-Fulvic Acid Coprecipitates.

Cr(VI) detoxification and organic matter (OM) stabilization are usually influenced by the biological transformation of iron (Fe) minerals; however, the underlying mechanisms of metal-reducing bacteria on the coupled kinetics of Fe minerals, Cr, and OM remain unclear. Here, the reductive sequestration of Cr(VI) and immobilization of fulvic acid (FA) during the microbially mediated phase transformation of ferrihydrite with varying Cr/Fe ratios were investigated. No phase transformation occurred until Cr(VI) was completely reduced, and the ferrihydrite transformation rate decreased as the Cr/Fe ratio increased. Microscopic analysis was uncovered, which revealed that the resulting Cr(III) was incorporated into the lattice structure of magnetite and goethite, whereas OM was mainly adsorbed on goethite and magnetite surfaces and located within pore spaces. Fine line scan profiles showed that OM adsorbed on the Fe mineral surface had a lower oxidation state than that within nanopores, and C adsorbed on the magnetite surface had the highest oxidation state. During reductive transformation, the immobilization of FA by Fe minerals was predominantly via surface complexation, and OM with highly aromatic and unsaturated structures and low H/C ratios was easily adsorbed by Fe minerals or decomposed by bacteria, whereas Cr/Fe ratios had little effect on the binding of Fe minerals and OM and the variations in OM components. Owing to the inhibition of crystalline Fe minerals and nanopore formation in the presence of Cr, Cr sequestration and C immobilization can be synchronously favored at low Cr/Fe ratios. These findings provide a profound theoretical basis for Cr detoxification and synchronous sequestration of Cr and C in anoxic soils and sediments.

Applying Fluorescence Dissolved Organic Matter Spectra and Phytoplankton Biology Index for Assessing Urban River Quality

The relationship between phytoplankton dynamics and dissolved organic matter (DOM) in aquatic systems based on fluorophore organic matter properties results in poor implementation of methods for water quality monitoring. This study aimed to investigate the relation between fluorophore organic matter and phytoplankton index and to estimate the phytoplankton index by fluorescent organic components for water quality assessment. The research was conducted by sampling urban river water, followed by measuring the biological phytoplankton index and dissolved organic matter during the wet and dry seasons. Fluorescence Excitation Emission Matrices (FEEMs) analysis combined with Parallel Factor (PARAFAC) analysis identified three main components of the fluorescence organic matter, i.e., a fulvic acid-like component (C1) and humic acid-like components (C2 and C3), in the aquatic system, whether in the dry season or the wet season. C1 was mainly generated by phytoplankton species, i.e., Nitzschia sp., Plectonema sp., Navicula sp., and Pinnularia sp., and C2 and C3 had a less significant relationship with phytoplankton species. The diversity of Bacillariophyta had a stronger contribution to the release of DOM than the diversity of Cyanobacteria. The abundance index of a particular phytoplankton species can be used to determine the organic components of FEEM-derived fluorescence organic matter.

Applying Fluorescence Dissolved Organic Matter Spectra and Phytoplankton Biology Index for Assessing Urban River Quality

The relationship between phytoplankton dynamics and dissolved organic matter (DOM) in aquatic systems based on fluorophore organic matter properties results in poor implementation of methods for water quality monitoring. This study aimed to investigate the relation between fluorophore organic matter and phytoplankton index and to estimate the phytoplankton index by fluorescent organic components for water quality assessment. The research was conducted by sampling urban river water, followed by measuring the biological phytoplankton index and dissolved organic matter during the wet and dry seasons. Fluorescence Excitation Emission Matrices (FEEMs) analysis combined with Parallel Factor (PARAFAC) analysis identified three main components of the fluorescence organic matter, i.e., a fulvic acid-like component (C1) and humic acid-like components (C2 and C3), in the aquatic system, whether in the dry season or the wet season. C1 was mainly generated by phytoplankton species, i.e., Nitzschia sp., Plectonema sp., Navicula sp., and Pinnularia sp., and C2 and C3 had a less significant relationship with phytoplankton species. The diversity of Bacillariophyta had a stronger contribution to the release of DOM than the diversity of Cyanobacteria. The abundance index of a particular phytoplankton species can be used to determine the organic components of FEEM-derived fluorescence organic matter.

Diversity of complex polysaccharide degrading bacteria from the sediments of interlinked high Arctic fjords, Svalbard

Polysaccharides comprise a major component of marine organic matter and are mostly produced by phytoplankton through primary production. The present study reports the polysaccharide degrading ability of cold-adapted heterotrophs from interlinked high Arctic fjords in the Svalbard archipelago. One hundred and ninety-five polysaccharide degrading bacteria isolated from inner and outer fjord sediments, 148 bacterial isolates showed complex polysaccharide degrading enzyme activity. Pectinase was the most predominant polysaccharide-degrading enzyme, followed by agarase, alginate lyase, chitinase, and laminarinase. Xylanase and carboxy methyl cellulase were showed in a relatively lesser activity. Heterotrophic bacterial isolates from the inner and outer shelf regions showed variation in their complex polysaccharide utilization ability. In Kongsfjorden, pectinase producing bacteria were more prevalent in the outer fjord, while chitinase producing bacteria dominated the inner fjord. In Krossfjorden, chitinase producing bacteria were frequently encountered in the outer fjord, whereas pectinase, laminarinase, and alginate lyase producing bacteria dominated the inner fjord. The results of the study indicated that a significant difference in polysaccharide-degrading bacterial phylotypes between the inner and outer fjords (p<0.05). Major polysaccharide-degrading bacteria belonged to phylum Proteobacteria, followed by Firmicutes, Actinobacteria, and Bacteroidetes. The dominant polysaccharide-degrading genera are Marinobacter, Bacillus, Salinibacterium, Alcaligenes, and Planococcus. The findings reveal the availability of a wide range of polysaccharide substrates in fjord sediments and the significant functional role of the heterotrophic bacterial community in the remineralization process of fjord environments.

Long‐term fertilization and plastic film mulching modify temporal incorporation of 13C/15N‐labelled particulate organic matter

AbstractPlastic film mulching (PFM) is critical for agricultural planting and maximizing production in semiarid and arid areas. Particulate organic matter (POM) is assumed to be a sensitive indicator for evaluating the effects of different agricultural practices on soil fertility and the soil organic carbon (SOC) pool. Soil aggregates have the function of ‘wrap’ and protect the POM stored in them. However, there is limited information regarding how PFM and fertilization jointly influence the dynamic changes of newly added stalk‐derived POM in brown earth. Consequently, an in‐depth study of the fate of carbon (C) and nitrogen (N) derived from maize stalk residues within the particulate organic carbon (POC) and particulate organic nitrogen (PON) fractions in soil aggregates was undertaken. Its outcome would contribute to better predictions on the active organic matter components sequestered in the soil. The dynamics and accumulation of newly added maize stalk C and N as POC and PON in different soil aggregates (using the dry sieving method divided into &gt;2, 1–2, 0.25–1 and &lt;0.25 mm) were analysed by an in situ 13C/15N‐tracing technique under PFM and different fertilization treatments. Over 360 days of cultivation, the POC and PON contents were significantly (p &lt; 0.05) larger in the nitrogen (N) and organic manure (M) treatments than in the MN (manure combined with nitrogen) and Control treatments. The PFM treatment accelerated the decomposition of maize stalk C in the N fertilizer treatment, with an increase of 64% in stalk‐derived POC after the 1‐day cultivation period. Stalk‐derived POM tended to accumulate in &lt;0.25 mm microaggregates in the early cultivation period and then decreased rapidly with the extension of the cultivation period affected by PFM coupled with fertilization. However, stalk‐derived POM accumulation in macroaggregates (&gt;0.25 mm) fluctuated over the 360‐day cultivation period. Accordingly, PFM application and fertilization practices had important effects on the accumulation of newly added stalk‐derived POM in soil aggregates. We conclude that the accumulation of maize residue POM was primarily affected by soil fertilization type, rather than by the presence or absence of PFM. These results provide new insights into agricultural management strategies for improving soil carbon sequestration capacity.

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Ecology LettersVolume 26, Issue 5 p. ii-ii COVER IMAGEFree Access Cover Image First published: 12 April 2023 https://doi.org/10.1111/ele.14047AboutPDF Comments ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract The cover image is based on the Letter Molecular 14c evidence for contrasting turnover and temperature sensitivity of soil organic matter components by Juan Jia et al., https://doi.org/10.1111/ele.14204. Comments Please enable JavaScript to view the comments powered by Disqus. Volume26, Issue5May 2023Pages ii-ii RelatedInformation

Analysis of CO2 effects on porosity and permeability of shale reservoirs under different water content conditions

CO2 technology has been the key technology to enhance oil and gas recovery for shale oil and gas reservoir development. After injection, CO2 can react with water and generate carbonic acid, which then can react with various minerals in shale, leading to changes of porosity and permeability. However the specific research conclusions remain controversial on whether the effect of CO2 is improvement or damage for porosity and permeability. In CO2 hybrid fracturing, The areas with varied water content are formed due to the difference in mobility. So in this article, we carried out systematic research to clarify the interaction between CO2 and shale in different water content conditions (sufficient water, deficient water and water-free) and draw a pertinent conclusion. And the results show that the effects of CO2 treatment on shale have significant differences among different water content. Under sufficient water conditions, CO2 fully dissolves into water to generate carbonic acid, and large dissolved pores are generated by the massive dissolution of minerals such as feldspar and carbonates in the shale matrix, leading to the increase of porosity and permeability. Under deficient water conditions, only a small amount of carbonic acid is formed after the reaction of CO2 and water, leading to a significant decrease of porosity and permeability. Under water-free conditions, no dissolution is observed on the shale matrix, while some soluble components of organic matter may be extracted by CO2 to form organic pores, leading to slight changes in porosity and permeability. In large scales, although both porosity and permeability in the near-wellbore water-sufficient area is improved, the CO2-affected region presents the overall decline of porosity and permeability, due to the negative effects on the water-deficient area. So, it is necessary to enlarge the volume of water-sufficient areas to get a better effect of enhanced oil and gas recovery.

The importance of blue carbon as a food source to oysters (Saccostrea cucullata) inside a tropical pristine Australian estuary

This study investigated the importance of blue carbon (carbon captured from the atmosphere by algae, mangrove and seagrass leaves) as a component of particulate organic matter (POM) along the pristine King George River (Kimberley region, Australia), and how this modulates the diet of common suspension feeding bivalves (Mussels: Brachidontes sp. and Oysters: Saccostrea cucullata). These species utilise a range of different carbon sources (e.g., mangrove and seagrass detritus and plankton), which dictate the composition of locally available POM), which could then be used to evaluate shifts in consumer diet away from blue carbon within the estuary, to an increasing reliance on marine phytoplankton in offshore areas. The differences in δ13C of different organs (i.e., mantle, gill and adductor muscle) of oysters further affirm a greater discrepancy between ‘slow-turnover’ muscle and ‘fast-turnover’ gill and mantle tissue at offshore sites, when compared to inner estuarine sites.

Microbial necromass under global change and implications for soil organic matter.

Microbial necromass is an important source and component of soil organic matter (SOM), especially within the most stable pools. Global change factors such as anthropogenic nitrogen (N), phosphorus (P), and potassium (K) inputs, climate warming, elevated atmospheric carbon dioxide (eCO2 ), and periodic precipitation reduction (drought) strongly affect soil microorganisms and consequently, influence microbial necromass formation. The impacts of these global change factors on microbial necromass are poorly understood despite their critical role in the cycling and sequestration of soil carbon (C) and nutrients. Here, we conducted a meta-analysis to reveal general patterns of the effects of nutrient addition, warming, eCO2 , and drought on amino sugars (biomarkers of microbial necromass) in soils under croplands, forests, and grasslands. Nitrogen addition combined with P and K increased the content of fungal (+21%), bacterial (+22%), and total amino sugars (+9%), consequently leading to increased SOM formation. Nitrogen addition alone increased solely bacterial necromass (+10%) because the decrease of N limitation stimulated bacterial more than fungal growth. Warming increased bacterial necromass, because bacteria have competitive advantages at high temperatures compared to fungi. Other global change factors (P and NP addition, eCO2 , and drought) had minor effects on microbial necromass because of: (i) compensation of the impacts by opposite processes, and (ii) the short duration of experiments compared to the slow microbial necromass turnover. Future studies should focus on: (i) the stronger response of bacterial necromass to N addition and warming compared to that of fungi, and (ii) the increased microbial necromass contribution to SOM accumulation and stability under NPK fertilization, and thereby for negative feedback to climate warming.

Elucidating the composition of organic matter in water-repellent forest soils using analytical pyrolysis combined with gas chromatography–mass spectrometry (Py-GC–MS)

Soil water repellency (SWR) is an inability of soil to spontaneously absorb water. It affects the spatial distribution of soil moisture, may cause formation of preferential flow, increase surface runoff and the risk of water erosion, or affect nutrient availability for crops. Although there is a general agreement among published data that SWR is caused by hydrophobic components of soil organic matter (SOM), more comprehensive information is needed. Additionally, the link between SWR occurrence and SOM genesis has not been studied sufficiently. In this work, we analyzed SOM in water-repellent soils by pyrolysis combined with gas chromatography and mass spectrometry (Py-GC–MS). The samples were taken from two forest ecosystems in Slovakia: relatively dry pine–oak forest, located in the Záhorská nížina lowland (Záhorie), and spruce forest in the High Tatras with a colder and more humid climate. The results showed that the composition of SOM at both sites is dominated by partially decomposed residues of plant biomass. Whereas most compounds detected in the Záhorie samples were identified as pyrolysis products of lignin, the pyrolysates of the High Tatras soils originated mainly from polysaccharide-like substances. Although lauric (12:0), myristic (14:0) and palmitic (16:0) fatty acids were detected in pyrograms of water-repellent samples, the results suggest that the residues of lignin decomposition may contribute to SWR as well. Pyrolysates such as methylguaiacol, vinylguaiacol, dimethylphenol, or the methyl ester of vanillic acid are examples of less polar lignin-like moieties. Py-GC–MS data, as well as other soil properties, suggest that SWR at both sites is associated with the accumulation of certain SOM components in the topsoil. Acidic pH, higher C/N ratio and coarse soil texture prevent organic carbon stabilization in the studied soils. As a result, SOM is in great part composed of accumulated particulate residues with lignin-like origin and lipidic coatings, which contribute to SWR development during drier conditions.

Evaluation of current natural and anthropogenic radionuclide activity in coastal area bottom sediments of the Barents Sea (North of the Kola Peninsula)

This article is devoted to the study of the activity of technogenic 137Cs and 90Sr, as well as natural radionuclides 40K, 232Th and 226Ra in bottom sediments of the Kola coast of the Barents Sea, where a significant number of radiation objects are concentrated. In order to characterize and assess the accumulation of radioactivity in the bottom sediments, we studied the particle size distribution and some physicochemical parameters, such as the content of organic matter, carbonates and ash components. The average activities of natural radionuclides 226Ra, 232Th and 40K were 325.0, 25.1 and 466.7 Bq·kg−1, respectively. Levels of natural radionuclides in the coastal zone of the Kola Peninsula are within the range of marine sediments worldwide. Still, they are slightly higher than those observed in the central areas of the Barents Sea, most likely due to the formation of coastal bottom sediments as a result of the destruction of the natural radionuclide-enriched crystalline basement rocks that make up the Kola coast. The average activities of technogenic 90Sr and 137Cs in the bottom sediments of the Kola coast of the Barents Sea are 3.5 and 5.5 Bq·kg−1, respectively. The highest activities of 90Sr and 137Cs were found in the bays of the Kola coast, while they remain below detection limits in the open parts of the Barents Sea. Despite the presence of potential sources of radiation pollution in the coastal zone of the Barents Sea, we did not find any short-lived radionuclides in the bottom sediments, which indicates the absence of a significant influence of local sources on the transformation of the technogenic radiation background. The study of particle size distribution and physicochemical parameters showed that the accumulation of natural radionuclides is largely related to the content of organic matter and carbonates, while the accumulation of technogenic isotopes occurs in the composition of organic matter and the smallest fractions of bottom sediments.

Tofu by-product soy whey substitutes urea: Reduced ammonia volatilization, enhanced soil fertility and improved fruit quality in cherry tomato production

Soy whey is an abundant, nutrient-rich and safe wastewater produced in tofu processing, so it is necessary to valorize it instead of discarding it as sewage. Whether soy whey can be used as a fertilizer substitute for agricultural production is unclear. In this study, the effects of soy whey serving as a nitrogen source to substitute urea on soil NH3 volatilization, dissolved organic matter (DOM) components and cherry tomato qualities were investigated by soil column experiment. Results showed that the soil NH4+-N concentrations and pH values of the 50% soy whey fertilizer combined with 50% urea (50%-SW) and 100% soy whey fertilizer (100%-SW) treatments were lower than those of 100% urea treatment (CKU). Compared with CKU, 50%-SW and 100%-SW treatments increased the abundance of ammonia oxidizing bacteria (AOB) by 6.52–100.89%, protease activity by 66.22–83.78%, the contents of total organic carbon (TOC) by 16.97–35.64%, humification index (HIX) of soil DOM by 13.57–17.99%, and average weight per fruit of cherry tomato by 13.46–18.56%, respectively. Moreover, soy whey as liquid organic fertilizer reduced the soil NH3 volatilization by 18.65–25.27% and the fertilization cost by 25.94–51.87% compared with CKU. This study provides a promising option with economic and environmental benefits for soy whey utilization and cherry tomato production, which contributes to the win-win effectiveness of sustainable production for both the soy products industry and agriculture.

Experimental study on extraction of organic matter from coal by liquid CO2

Liquid CO2 injection into coal seam for CH4 displacement is one of the important means to strengthen gas extraction and carbon sequestration in recent years. Liquid CO2 is a non-polar solvent, based on the principle of “similar phase solubility”, part of non-polar or weakly polar organic matter can be dissolved in liquid CO2. By controlling the key parameters of liquid CO2 in the extraction process, small molecular organic matter can be dissolved and migrated from the pore structure of coal as far as possible. In order to clarify the main factors affecting the process of liquid CO2 extraction of coal body, the experimental platform of liquid CO2 extraction of organic matter in coal body was built by ourselves, the single factor experimental design method was used to analyze the evolution law of organic matter components in the process of liquid CO2 extraction of coal body. The experimental results showed that: the macromolecular structure of coal was not significantly damaged by liquid CO2 extraction; after liquid CO2 extraction, the relative contents of aliphatic hydrocarbon and aromatic hydrocarbon are positively correlated with pressure, the dissolution of ketones, alcohols, ethers and esters has the characteristics of stage, time sequence and explosion; at the initial stage of extraction, the dissolved compounds are free in the structure of the macromolecular network. With the increase of extraction pressure and time, the small molecular compounds of hydrocarbons and non-hydrocarbons in the embedded state are dissolved.

Fiber-Degrading Enzyme Increases Body Weight and Total Serum Cholesterol in Broiler Chickens Fed a Rye-Based Diet ,

Broiler chickens were fed diets based on either outer or inner endosperm from rye. These diets were fed with or without a fiber degrading enzyme to study the effects of the dietary fiber fraction on production results, body composition, serum lipid concentrations and apparent ileal digestibility of nutrients. Elimination of the dietary fiber effect by the enzyme generally improved the production results and caused an increase in total serum cholesterol concentrations. On average, at d 21 of the experiment chickens fed the enzyme supplemented outer endosperm diet had body weights and serum total cholesterol concentrations -23% and 37% higher, respectively, than those of birds fed the corresponding unsupplemented diet. The body fat content tended to be higher and the protein content was generally lower in chickens fed enzyme-supplemented diets. Chickens fed the unsupplemented outer endosperm diet had a low apparent ileal crude fat digestibility of only 23%, and birds fed the enzyme-supplemented diet had crude fat digestibility that was 113% higher but still lower than that of birds fed the inner endosperm diet. Birds fed enzyme-supplemented diets generally had higher apparent ileal digestibilities of organic matter, crude protein, starch, crude fat and dietary fiber components.

Insight into the fate of metal ions in response to the refined classification and transformation order of dissolved organic matter components during municipal solid waste composting

The refined classification and subtle transformation order of dissolved organic matter (DOM) components may govern the fate of metal ions (MIs) during composting. However, the classification of DOM components is still rough and the fate of MIs in response to the refined transformation order of DOM during municipal solid waste composting (MSWC) has not been studied. Here, the refined classification and evolution order of DOM components were redefined by two-dimensional correlation spectroscopy (2DCOS) analysis. Eight DOM components were redefined and their evolution order was: tyrosine-like (peak B)>humic acid-like (peak C1>peak C2)>terrestrial humic-like with small molecular size (peak A)>UVA humic-like with medium molecular size (peak D2)>UVC humic-like with medium molecular size (peak D1)>UVA humic-like with large molecular size (peak E2)>UVC humic-like with large molecular size (peak E1). Na and As were releasing in the whole process of DOM transformation. Cu and Al showed strong affinity with humic-like fraction, the anabolism of which leading to storage of Cu and Al in compost. Si, Fe, Mn, Co, Zn, Ni, Sr, Mg and Cr tend to combine with humic-like fraction with small molecular size. These responses were influenced by synergistic effect of key microorganisms (two bacterial groups and three fungal groups), in which the contribution of bacteria was greater than fungus. Finally, partial least-square path models of “environmental factors-key microorganisms-transformation order of DOM-MIs” were constructed. The combination of humic-like fractions continuously produced during MSWC and MIs made compost product with potential environmental risks. It is of great significance to develop abiotic factors regulation approach based on refined classification and transformation of organic components for reducing environmental risks of compost product.

Experimental drought increased the belowground sink strength towards higher topsoil organic carbon stocks in a temperate mature forest

Reduced carbon assimilation by trees is often considered to lower the overall carbon sink function of drought-stressed forests. However, soil organic carbon (SOC) stocks may respond differently to drought than ecosystem carbon flux dynamics, leading to imprecise predictions of soil carbon sequestration when one value is inferred from the other. As a major component of soil organic matter, SOC is the largest actively cycling terrestrial carbon reservoir, and thus fulfills various important ecosystem services. Yet, there is uncertainty about how SOC quantity and quality respond to drought in temperate forests. This study addressed the depth distribution of SOC stocks and soil organic matter stability in a forest exposed to artificial drought for five consecutive growing seasons below clusters of temperate mature deciduous beech (Fagus sylvatica L.) and coniferous spruce (Picea abies (L.) Karst.). In addition to SOC stock determination, we measured concentrations of water-extractable organic carbon (WEOC), performed density fractionation, and determined beta values of SOC (slopes of linear regressions between δ13C of soil and log-transformed SOC content throughout soil depth profiles). Following drought, SOC stocks down to 30 cm depth increased by a factor of 1.5 under P. abies while they did not change with drought under F. sylvatica. Under both species, SOC stocks in the mineral topsoil (0–5 cm soil depth) increased by >80 % with drought, increasing the relative contribution of this thin depth section to total SOC from 5 % to >30 %. At 5–15 cm soil depth, SOC stocks decreased with drought under F. sylvatica but not under P. abies. With drought, carbon in the free light fraction (fLF) increased under F. sylvatica but declined marginally under P. abies. Results from density fractionation and beta values suggest decreased soil organic matter stability under F. sylvatica and increased stability under P. abies. Greater SOC accumulation suggests that the belowground carbon sink strength of drought-stressed forests increases, which contrasts with reduced ecosystem carbon uptake under drought.

Adsorption behaviour and mechanism of Avermectin-based pesticides in soil driven by H-bonds formed between the compounds and humus

Adsorption is an essential process in regulating pesticide distribution in soil. However, the relationship between soil adsorption mechanisms and the structure of the compounds is unclear. Different soil samples (S1, S2, S3) were selected for adsorption tests of avermectin B2a (AVB2a), avermectin B1a (AVB1a), and emamectin benzoate (EB) to investigate the influence of adsorbent properties and compound structure on the adsorption. The adsorption of the three chemicals by the three soils was extensive and irreversible. Soil adsorption of AVB2a was strongest, followed by AVB1a and EB. Soil adsorption tests of three avermectin-based pesticides showed that the –OH groups of the compounds were the main adsorption site. The humus fraction, a significant component of the soil organic matter, was extracted for further adsorption tests on the compounds. The humus fraction most strongly adsorbs AVB2a, followed by AVB1a and EB, indicating that –OH is also the main site for the humus fraction to adsorb compounds. Differences in the content of polar groups in the humus fraction by elemental analysis and 13C NMR analysis suggested that the –OH of avermectin-based pesticides interacts with the polar groups of humus. Quantum chemical calculations confirm that the –OH groups of the compound form hydrogen bonds with amino, hydroxyl, carboxyl, and carbonyl groups in the humus, thus demonstrating that hydrogen bonding is the mechanism by which avermectin-based pesticides are adsorbed to the soil.

Combined hydrothermal and biological treatments for valorization of fruit and vegetable waste into liquid organic fertilizer

This study investigated the effects of hydrothermal treatment, biological treatment and their combination on nutrients recovery from fruit and vegetable waste (FVW) and evaluated the feasibility of fruit and vegetable waste juice (FVWJ) from the combined treatment as liquid organic fertilizer. In this study, following conditions were determined suitable for FVW treatment: the temperature of 165 °C and retention time of 45 min for hydrothermal treatment, 20 h for biological treatment, and Weissella, as the dominant microbial genus present in FVW, was suggested as inoculum for biological treatment. In the combined treatment, based on the above conditions of hydrothermal and biological treatments, the yield of FVWJ was 93.03 g out of 100 g FVW, and concentrations of organic matter (1.45%, w/w), primary nutrients (0.51%, w/w), and toxic components in the FVWJ complied with the requirements for use concentration in both Chinese and European standards for liquid organic fertilizer. The economic analysis showed the net saving of 13.60 USD per ton FVW, indicating that it is an economical approach to valorize fruit and vegetable waste into liquid organic fertilizer through the combined treatment.