Dicyandiamide (DCD) could reduce composting nitrogen (N) losses, but the decomposes at high temperatures limited its efficacy, which might be mitigated by co-application with biochar (BC) and wood ...vinegar (WV). Our study revealed that DCD alone or co-applied with BC and WV did not reduce N2O emissions during the composting of chicken manure and wheat straw. However, it significantly decreased NH3 and CH4 emissions by 22.6–45.6% and 53.8–85.6%, respectively, equivalent to a 24.1–44.8% reduction in GWP compared to the control. Furthermore, the combined use of DCD with BC and WV enhanced total N content by 5.6–36.6%, increased the compost accumulation temperature by 3.8–6.1%. DCD alone addition increased the compost dissolved organic matter (DOM) content by 12.2%, and when coupled with BC and WV, it enhances the biological index value to promote new DOM generation. DCD combined with BC could increase the final humus content of compost, thereby enhancing its quality, which approach also produced greater economic benefits (266.3 CNY t−1), compared to conventional composting. In conclusion, co-application of DCD with BC and WV in composting not only reduces the emission of NH3, N2O and CH4, but also increases the compost fertility and provides more economic benefits.
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•DCD was alone or co-applied with BC and WV into composting.•DCD effectively reduced gaseous N losses during composting.•DCD plus BC reduced composting NH3 volatilization by 45.6%.•All DCD-amended treatments lowered the GWP of composting by 24.1–44.8%.•DCD plus BC amended composting yields the highest net benefits.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To assess the influence of dissolved organic matter (DOM) on the acid–base system of the Baltic Sea, 19 stations along the salinity gradient from Mecklenburg Bight to the Bothnian Bay were sampled in ...November 2011 for total alkalinity (AT), total inorganic carbon concentration (CT), partial pressure of CO2 (pCO2), and pH. Based on these data, an organic alkalinity contribution (Aorg) was determined, defined as the difference between measured AT and the inorganic alkalinity calculated from CT and pH and/or CT and pCO2. Aorg was in the range of 22–58μmolkg−1, corresponding to 1.5–3.5% of AT. The method to determine Aorg was validated in an experiment performed on DOM-enriched river water samples collected from the mouths of the Vistula and Oder Rivers in May 2012. The Aorg increase determined in that experiment correlated directly with the increased DOC concentration caused by enrichment of the >1kDa DOM fraction. To examine the effect of Aorg on calculations of the marine CO2 system, the pCO2 and pH values measured in Baltic Sea water were compared with calculated values that were based on the measured alkalinity and another variable of the CO2 system, but ignored the existence of Aorg. Large differences between measured and calculated pCO2 and pH were obtained when the computations were based on AT and CT. The calculated pCO2 was 27–56% lower than the measured value whereas the calculated pH was overestimated by more than 0.4 pH units. Since biogeochemical models are based on the transport and transformations of AT and CT, the acid–base properties of DOM should be included in calculations of the CO2 system in DOM-rich basins like the Baltic Sea. In view of our limited knowledge about the composition and acid/base properties of DOM, this is best achieved using a bulk dissociation constant, KDOM, that represents all weakly acidic functional groups present in DOM. Our preliminary results indicated that the bulk KDOM in the Baltic Sea is 2.94·10−8molkg−1. Although this KDOM has no thermodynamic meaning, it can be a useful tool in numerical studies as it allows an approximation of Aorg in seawater.
•Organic alkalinity (Aorg) constitutes 1.5–3.5% of AT in the Baltic Sea.•Ignoring Aorg causes significant uncertainty in the calculations of pH and pCO2.•The highest uncertainty occurs when pH and pCO2 are calculated from CT and AT.•Bulk dissociation constant of DOM (KDOM) in the Baltic Sea amounts to 2.94·10−8molkg−1.
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•Lignin content is inversely proportional to DOM release from the biochar.•Biochar pyrolyzed sawdust with more lignin extracted less Fe from soil.•Sawdust biochar with less lignin can ...enhance the As leaching from soil.
Biochar is widely used material whose physical and chemical characteristics been widely investigated. Nevertheless, dissolved organic matter (DOM) released from biochar has received relatively little attention. In particular, little research has been conducted to understand the effects of feedstock biomass components on biochar DOM release. To control the amount of DOM released from biochar, this study focuses on the role of lignin, a component of biomass. To this end, samples of sawdust containing different lignin contents and a binary mixture of cellulose and lignin were pyrolyzed at 400 and 700 °C, and then the physico-chemical properties of the resulting biochar, and Fe(II) and As mobility were investigated in arsenic-contaminated soil amended by the biochar. This study showed that lignin is an critical factor in controlling the release of DOM. The amount of DOM released from the sawdust biochar with the lowest lignin content was 33% (400 °C) and 44% (700 °C) lower than those produced from lignin-rich biochar (sawdust without the extraction of lignin). The amount of oxalic acid in DOM decreased with increased lignin content. In addition, As mobility and the transformation of Fe(II) were minimized when lignin-rich biochar was applied to the As-contaminated soil. More importantly, these results suggest that controlling the lignin content of biomass can be universally applied to predict DOM concentrations of the biochars produced.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Peptides-like and protein-like compounds in mass spectrum increased after 28 days.•AOM degraded after 28 days still inhibited the MeHg uptake by phytoplankton.•Inhibition after 28 days on MeHg ...uptake resulted from bacterial metabolites.
Methylmercury (MeHg) uptake by phytoplankton represents a key step in determining the exposure risks of aquatic organisms and human beings to this potent neurotoxin. Phytoplankton uptake is believed to be negatively related to dissolved organic matter (DOM) concentration in water. However, microorganisms can rapidly change DOM concentration and composition and subsequent impact on MeHg uptake by phytoplankton has rarely been tested. Here, we explored the influences of microbial degradation on the concentrations and molecular compositions of DOM derived from three common algal sources and tested their subsequent impacts on MeHg uptake by the widespread phytoplankton species Microcystis elabens. Our results indicated that dissolved organic carbon was degraded by 64.3‒74.1% within 28 days of incubating water with microbial consortia from a natural meso‑eutrophic river. Protein-like components in DOM were more readily degraded, while the numbers of molecular formula for peptides-like compounds had increased after 28 days’ incubation, probably due to the production and release of bacterial metabolites. Microbial degradation made DOM more humic-like which was consistent with the positive correlations between changes in proportions of Peaks A and C and bacterial abundance in bacterial community structures as illustrated by 16S rRNA gene sequencing. Despite rapid losses of the bulk DOM during the incubation, we found that DOM degraded after 28 days still reduced the MeHg uptake by Microcystis elabens by 32.7‒52.7% relative to a control without microbial decomposers. Our findings emphasize that microbial degradation of DOM would not necessarily enhance the MeHg uptakes by phytoplankton and may become more powerful in inhibiting MeHg uptakes by phytoplankton. The potential roles of microbes in degrading DOM and changing the uptakes of MeHg at the base of food webs should now be incorporated into future risk assessments of aquatic Hg cycling.
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The behavior and composition of hydrochar-based dissolved organic matter (DOM) would affect the efficiency of copper (Cu) removal from wastewater through adsorption. In this study, the reed was ...hydrolyzed in the presence of feedwater with and without ZnCl2, FeCl3, and SnCl4 to produce pristine hydrochars (PHCs), which were named H2O-HC, ZnCl2-HC, FeCl3-HC, and SnCl4-HC. After removal of DOM, washed hydrochars (WHCs) were obtained, labelled as W–H2O-HC, W-ZnCl2-HC, W-FeCl3-HC, and W-SnCl4-HC. The release dynamics of DOM from PHCs were analyzed, and the adsorption behaviors of Cu2+ on both PHCs and WHCs were investigated. The results showed that chloride-modifications were beneficial for the porosity, specific surface area (SSA), and functional groups of WHCs. Meanwhile, the quantity of hydrochar-based DOM was significantly affected by chloride-modifications. In particular, the relative contents of Ar–P and Fa-L in the DOM released from hydrochars varied with time and modification. Furthermore, the Qe of Cu2+ adsorption on WHCs followed the order of W-SnCl4-HC > W-FeCl3-HC > W-ZnCl2-HC > W–H2O-HC at 15 °C. Compared to PHCs, the adsorption capacity of Cu2+ on WHCs was improved by 7.15–119.77% at the temperature of 35 °C. Simultaneously, the adsorption capacity of Cu2+ in WHCs showed a significant correlation with the SSA via physical adsorption (P < 0.05). Moreover, XPS analysis revealed that Cu2+ adsorption also occurred via complexation and chelation through newly formed Cu–O group between W-SnCl4-HC and Cu2+. Notably, the increase of Cu2+ adsorption in WHCs was significantly correlated with the release of Fa-L and Ar–P from PHCs (P < 0.05). This study found that the content and composition of hydrochar-based DOM could be a major driving factor for Cu2+ adsorption.
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•The adsorption performance of chlorides-modified hydrochars for Cu2+ was studied.•The Qe of Cu2+ adsorption followed the order of W-SnCl4-HC > W-FeCl3-HC > W-ZnCl2-HC > W–H2O-HC at 15 °C.•Cu2+ removal efficiency of hydrochars was improved significantly by removing DOM.•Due to complexation, DOM should not be overlooked in the adsorption of Cu2+ on hydrochars.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Sponge holobionts (i.e., the host and its associated microbiota) play a key role in the cycling of dissolved organic matter (DOM) in marine ecosystems. On coral reefs, an ecological shift from ...coral-dominated to algal-dominated ecosystems is currently occurring. Given that benthic corals and macroalgae release different types of DOM, in different abundances and with different bioavailability to sponge holobionts, it is important to understand how the metabolic activity of the host and associated microbiota change in response to the exposure to both DOM sources. Here, we look at the differential gene expression of two sponge holobionts 6 hours after feeding on naturally sourced coral- and macroalgal-DOM using RNA sequencing and meta-transcriptomic analysis. We found a slight, but significant differential gene expression in the comparison between the coral- and macroalgal-DOM treatments in both the high microbial abundance sponge Plakortis angulospiculatus and the low microbial abundance sponge Haliclona vansoesti. In the hosts, processes that regulate immune response, signal transduction, and metabolic pathways related to cell proliferation were elicited. In the associated microbiota carbohydrate metabolism was upregulated in both treatments, but coral-DOM induced further lipid and amino acids biosynthesis, while macroalgal-DOM caused a stress response. These differences could be driven by the presence of distinct organic macronutrients in the two DOM sources and of small pathogens or bacterial virulence factors in the macroalgal-DOM. This work provides two new sponge meta-transcriptomes and a database of putative genes and genetic pathways that are involved in the differential processing of coral- versus macroalgal-DOM as food source to sponges with high and low abundances of associated microbes. These pathways include carbohydrate metabolism, signaling pathways, and immune responses. However, the differences in the meta-transcriptomic responses of the sponge holobionts after 6 hours of feeding on the two DOM sources were small. Longer-term responses to both DOM sources should be assessed to evaluate how the metabolism and the ecological function of sponges will be affected when reefs shift from coral towards algal dominance.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Formaldehyde (HCHO) is either a reactant, intermediate, or product in numerous industrial catalytic reactions; therefore, revealing the full transformation process of HCHO during heterogeneous ...catalysis is of prime importance in understanding the mechanisms of many HCHO-related reactions and designing more efficient catalysts. As two main intermediates in HCHO transformation, the conversion of dioxymethylene (DOM) to formate is one of the key steps. There are three recognized pathways for this step, including direct dissociation of DOM, DOM combining with surface O, or through a Cannizzaro-type reaction. Herein, we reveal that the catalytic reaction between DOM and the abundant surface OH groups is a facile pathway for the transformation of DOM to formate species on TiO2 and also on TiO2-supported noble metal catalysts. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results demonstrate that the presence of water vapor is favorable for the conversion of DOM to formate species on TiO2, and the loading of noble metals (Ir/Pt) on TiO2 further promotes the activation of H2O, thereby boosting the transformation of DOM into formate. Density functional theory (DFT) calculations show that HCHO consumes the bridging OH groups to form DOM species first followed by the reaction between DOM and the terminal OH groups on the TiO2 surface to produce formate, and the latter reaction is both thermodynamically and kinetically favorable. These results provide deeper insight into HCHO transformation and demonstrate another role of surface hydroxyl groups in catalytic reaction.
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IJS, KILJ, NUK, PNG, UL, UM
Dissolved organic matter (DOM), as the most active ingredient in compost, directly determines the speciation and environmental behavior of HMs. Here, the binding properties of DOM derived from ...chicken-manure compost (CHM), cow-manure compost (COM) and pig-manure compost (PIM) with HMs were explored by analyses of Fluorescence excitation-emission matrix parallel factor (EEM-PARAFAC) and two-dimensional correlation Fourier transform infrared spectroscopy (2D-FTIR-COS). Results showed that the binding characteristics vary with origin of DOM and type of HMs. The fulvic-like component dominated the transformation of HMs speciation, and CHM-DOM had higher affinity with HMs and greater risk causing pollution due to its higher aromaticity, molecular weight and distribution of fluorescent components. Moreover, Cu(II) can efficiently bind to DOM with the stability constants (log kM) ranging from 4.53 to 5.38, followed by Pb(II) (3.34–3.57), whereas Cd(II) can hardly bind to DOM. The amide and polysaccharide were the predominant sites for HMs binding in CHM-DOM, and polysaccharide and phenolic in COM-DOM, while phenolic and amide in PIM-DOM, respectively. Although the proportion of protein-like components and non-fluorescent polysaccharides in DOM were low, their role in HMs binding should not be ignored. In brief, the environmental risk caused by livestock manure compost may originate from interactions between DOM and HMs.
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•Binding characteristics vary with origin of DOM and type of HMs.•CHM-DOM may cause environmental risk due to its interaction with HMs.•Protein and polysaccharides should not be ignored in HMs binding.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Microbes promoted the dissolution of oxides on mineral surfaces in water.•Extracellular polymeric substances contributed to mineral biotransformation.•Electronic transfer between minerals and ...microbes changed the mineral activation.•FT-ICR-MS measured the decomposition of organic matters at the molecular level.•Biotransformation of minerals inhibited the decomposition of organic matters.
Photochemical reactions that widely occur in aquatic environments play important roles in carbon fate (e.g., carbon conversion and storage from organic matter) in ecosystems. Aquatic microbes and natural minerals further regulate carbon fate, but the processes and mechanisms remain largely unknown. Herein, the interaction between Escherichia coli and pyrite and its influence on the fate of carbon in water were investigated at the microscopic scale and molecular level. The results showed that saccharides and phenolic compounds in microbial extracellular polymeric substances helped remove pyrite surface oxides via electron transfer. After the removal of surface oxides on pyrite, the photochemical properties under visible-light irradiation were significantly decreased, such as reactive oxygen species and electron transfer capacity. Unlike the well-accepted theory of minerals protecting organic matter in the soil, the organic matter adsorbed on minerals preferred degradation due to the enhanced photochemical reactions in water. In contrast, the minerals transformed by microbes suppressed the decomposition of organic matter due to the passivation of the chemical structure and activity. These results highlight the significance of mineral chemical activity on organic matter regulated by microbes and provide insights into organic matter conversion in water.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The occurrence of microplastics (MPs) as emerging contaminants in the environment may cause changes in water or sediment characteristics, and further affect their biogeochemical cycles. Thus, ...insights into the interactions between dissolved organic matter (DOM) and MPs are essential for the assessment of environmental impacts of MPs in ecosystems. Integrating spectroscopic methods with chemometric analyses, this work explored the chemical and microstructural changes of DOM-MP complex to reveal the mechanism of DOM-MP interaction at a molecular level. MPs were found to interact with the aromatic structure of DOM via π-π conjugation, then be entrapped in the DOM polymers by the carboxyl groups and C=O bonds, constituting a highly conjugated co-polymer with increased electron density. This induced the fluorescence intensity increase in DOM. The interaction affinity of DOM-MP was highly dependent on the MP size and solution pH. This work offers a new insight into the impact of MP discharge on environment and may provide an analytical framework for evaluating MP hetero-aggregation and the roles of MPs in the transportation of other contaminants. Furthermore, the integrated methods used in this work exhibit potential applications in exploring the fragmentation processes of MPs and formation of secondary MPs under natural conditions.
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•DOM is adhered onto MPs via π-π conjugation, carboxyl groups and C=O bonds.•MP-DOM constitutes a conjugated co-polymer with an elevated electron density.•Interaction between DOM and MP depends on MP size and solution pH.•The approach has a great potential in elucidating plastics fragmentation and secondary MPs formation.
The interaction mechanism between humic acid and polystyrene microplastics is explored and new insights into the impact of MP discharge on environment are provided.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
