Anaerobic Incubation Research Articles

Effects of Land Use Types on CH4 and CO2 Production Potentials in Subtropical Wetland Soils

Changes in land use types can alter the soil and environmental characteristics of wetlands, which in turn influence the magnitude of greenhouse gas production by soil microbes. However, the effects of land use change on the production potential of methane (CH4) and carbon dioxide (CO2) in subtropical wetland soils and the underlying controls are still largely unknown. In this study, we examined the soil CH4 and CO2 production potentials under five different land use types (natural mangrove, Gei Wai water channel, Gei Wai forest, reedbed, and freshwater pond) and their relationships with soil physico-chemical properties in a subtropical wetland in Hong Kong using aerobic and anaerobic laboratory incubation experiments. Our results showed an overall decreasing trend of CH4 and CO2 production potentials down the soil profile at all sites, which could be attributed to a reduction in the concentrations of soil organic matter (SOM), total Kjeldahl nitrogen (TKN) and ammonium nitrogen (NH4+-N). Moreover, the soil CH4 and CO2 production potentials varied significantly in the surface soils among land use types, but were more similar across the sites in the deeper soils. The conversion of natural mangrove to other land use types significantly reduced both the aerobic and anaerobic CO2 production potentials in the top 10 cm soils, except for Gei Wai forest, which demonstrated significantly higher CO2 production rates (61.15–97.91 μg g−1 day−1). Meanwhile, the mean CH4 production potential in the surface soils of natural mangrove (0.05 μg g−1 d−1) was significantly lower than that in the Gei Wai forest and Gei Wai channel (0.26–0.27 μg g−1 day−1) but slightly higher than that in the freshwater pond and reedbed (0.00–0.02 μg g−1 day−1). The high soil CH4 and CO2 production potentials observed in the Gei Wai forest could be explained by the high soil concentrations of SOM, TKN and NH4+-N. On the other hand, the lower anaerobic CH4 and aerobic CO2 productions observed in the reedbed could be attributed to the lower concentrations of NH4+-N and available phosphorus. Our findings highlighted the significant impacts of land use types on the CH4 and CO2 production potentials of subtropical wetland soils, which had practical implications for wetland management for climate change mitigation.

Effect of a Flaxseed Lignan Intervention on Circulating Bile Acids in a Placebo-Controlled Randomized, Crossover Trial.

Plant lignans and their microbial metabolites, e.g., enterolactone (ENL), may affect bile acid (BA) metabolism through interaction with hepatic receptors. We evaluated the effects of a flaxseed lignan extract (50 mg/day secoisolariciresinol diglucoside) compared to a placebo for 60 days each on plasma BA concentrations in 46 healthy men and women (20–45 years) using samples from a completed randomized, crossover intervention. Twenty BA species were measured in fasting plasma using LC-MS. ENL was measured in 24-h urines by GC-MS. We tested for (a) effects of the intervention on BA concentrations overall and stratified by ENL excretion; and (b) cross-sectional associations between plasma BA and ENL. We also explored the overlap in bacterial metabolism at the genus level and conducted in vitro anaerobic incubations of stool with lignan substrate to identify genes that are enriched in response to lignan metabolism. There were no intervention effects, overall or stratified by ENL at FDR < 0.05. In the cross-sectional analysis, irrespective of treatment, five secondary BAs were associated with ENL excretion (FDR < 0.05). In vitro analyses showed positive associations between ENL production and bacterial gene expression of the bile acid-inducible gene cluster and hydroxysteroid dehydrogenases. These data suggest overlap in community bacterial metabolism of secondary BA and ENL.

Characterization of dissolved organic matter extracted from water treatment sludge

Abstract The characteristics of dissolved organic matter (DOM) that formed during the aerobic and anaerobic incubation of drinking water treatment sludge stored at different temperatures (5 °C, 20 °C, 40 °C) for long periods (7, 14, and 21 days) were investigated. Anaerobic incubation at high temperatures with prolonged storage was found to result in higher organic content than aerobic incubation (3.6–6.8 times at 40 °C). The high temperatures caused changes in the DOM fractions, with humic-like substances mainly formed in aerobic incubation and protein-like substances in anaerobic incubation. Results showed that the fluorescence intensity of humic-like and protein-like substances increased by 45% and 22%, respectively, at the end of the anaerobic incubation period. The UV-absorbing DOM constituents in aerobic incubation had lower molecular weights and were more heterogeneous than those in anaerobic incubation.

Organo-mineral interactions and soil carbon mineralizability with variable saturation cycle frequency

The response of mineral-stabilized soil organic carbon (SOC) to environmental change is a source of uncertainty in the understanding of SOC cycling. Fluctuating wet-dry cycles and associated redox changes in otherwise well-drained soils may drive mineral dissolution, organic carbon (OC) mobilization, and subsequent OC mineralization. However, the extent to which rapid fluctuations between water-saturated and unsaturated conditions (i.e., flashy conditions) result in long-term changes in mineral composition and organo-mineral interactions is not well understood. In this study, the effect of variable saturation frequency on soil mineral composition, mineral-associated OC, and OC mineralizability was tested using selective dissolution, bulk spectroscopy, microscale imaging, and aerobic-anaerobic incubation experiments. Previous water table fluctuation measurements and diagnostic profile characteristics at Hubbard Brook Experimental Forest (NH) were used to identify soils with high, medium, and low saturation frequency regimes (defined by historical water table cycling frequency; i.e., water table presence and recession in the upper B horizon). We found the amount of OC released during extractions targeting non-crystalline minerals was of similar magnitude as extracted iron (Fe) in lower saturation frequency soils. However, the magnitude of extracted OC was 2.5 times greater than Fe but more similar to extractable aluminum (Al) in higher saturation frequency soils. Bulk soil Fe was spatially more strongly correlated to soil organic matter (SOM) in lower saturation frequency soils (Spearman Rank rs = 0.62, p < 0.005), whereas strong correlations between Al and SOM were observed in higher saturation frequency soils (rs = 0.88, p < 0.005) using nanoscale secondary ion mass spectrometry (NanoSIMS) imaging. Characterization of bulk soil Fe with X-ray absorption spectroscopy showed 1.2-fold greater Fe(II) and 1-fold lower contribution of Fe-organic bonding in soils with high saturation frequency. Fe(III) interactions with carboxylic and aromatic C were identified with 13C nuclear magnetic resonance (NMR) spectroscopy Fe(III) interference experiments. Additionally, carboxylic acid enrichment in high saturation frequency soils quantified by C K-edge X-ray absorption spectroscopy point towards the role of carboxylic functional groups in Al-organic in addition to Fe-organic interactions. In our incubation experiments, a doubling in short-term CO2 evolution (per unit total soil C) was detected for high relative to low saturation frequency soils. Further, an order of magnitude increase in CO2 evolution (per unit water-extractable OC) following anaerobic incubation was only detected in high saturation frequency soils. The observed shift towards Al-dominated SOC interactions and higher OC mineralizability highlights the need to describe C stabilization in soils with flashy wet-dry cycling separately from soils with low saturation frequency or persistent saturation.

Impact of Different Parameters upon the Production of Virulence Factors in Escherichia coli Strains Isolated from Marine Water

This study aimed to look into the expression of 10 virulence factors (VF) in 100 Escherichia coli strains harvested from the Black Sea Coast. E. coli strains were grown under different conditions, simulating various environmental stressors. The VF production [esculinase, amylase, pore-forming enzymes (hemolysin - spot and CAMP-like hemolysis; lipase; lecithinase)], lysine-decarboxylase, proteases (caseinase, gelatinase) and DNase was investigated at variable temperatures (4°C, 22°C, 37°C, 44°C and 56°C), NaCl (from 0 to 10%) and glucose concentrations (1.5% and 3%), different pH values (5.0, 7.2 and 9.6) and also in aerobic or anaerobic incubation conditions. The investigation of E. coli strains unraveled their ability to grow at 22°C, 37°C, 44°C, regardless of the salinity, pH, and glucose concentration, both in aerobic and anaerobic incubation conditions. The VF were better expressed at 37°C, followed by 22°C, especially siderophores, amylase, and caseinase production. The expression of different VF was variable at a certain salinity, i.e., at 0% NaCl, only amylase and siderophores production was observed. At 2% and 3%, the amylase was better expressed. The best expression of siderophores and caseinase was at 6% NaCl. At higher salinity, the expression of VF started to decrease. The amylase and caseinase were better expressed at pH 9.6 and siderophores at pH 7.2. Higher glucose concentrations (3%) proved to have an inhibitory effect on amylase expression and caseinase. The aerobic/anaerobic incubation conditions exhibited no significant differences in the VF expression. In conclusion, these outcomes reveal the ability of enterobacterial aquatic strains to survive in the presence of different stressors and maintain the expression of potential VF expression even in extreme environmental conditions.

Mechanisms of enhanced methane emission due to introduction of Spartina anglica and Phragmites australis in a temperate tidal salt marsh

Introductions of exotic plants are widespread ecological threats disturbing the carbon and nutrient cycles in global coastal wetlands. Previous studies have found that the invasion has enhanced methane emission through increased primary production and a changed methanogenic pathway. However, the previous studies did not determine the depth profiles of the changes while the depth in the soil profile to which the disturbance propagates is one of the critical issues to be addressed. In this study, we illustrated the depth profiles of the effect of the introductions of S. anglica and P. australis on the potential methane production, soil biogeochemistry, and soil microbial community which play a substantial role in enhanced methane emission due to the invasions. The in situ field measurements and anaerobic incubation were conducted to determine the mechanistic differences of depth profiles. Both introductions of S. anglica and P. australis increased methane emission through different microbial mechanisms depending on depth profile. Potential methane production was stimulated in shallow and deep soil layer of S. anglica and P. australis-introduced marshes, respectively. S. anglica increased the contribution of methylotrophic methanogenesis in top soil layers while P. australis decreased competitive inhibition by sulfate reducers in all soil layers. These results emphasize the importance of below-ground microbial activity and vertical distribution in carbon cycles in tidal marshes. Further plant invasion studies should focus on depth profiles of microbial processes, as their distribution and activity vary substantially across soil depths.

1260 Retrieval Number: G5927059720/2020©BEIESP DOI: 10.35940/ijitee.G5927.059720 Journal Website: www.ijitee.org Published By: Blue Eyes Intelligence Engineering &amp; Sciences Publication Bio Degradable Polymers for Replacement of Plastics

One of the most crucial ingredients of municipal waste is plastics. Plastic has been posing a problem of disposal and surrounding pollution difficulties because of their non disposable character. To minimize their surrounding influence and making them to be converted during process of organic waste reusable processes, many materials in a little while back been introduced to enhance the nature of being biodegradable in plastics. In the following review, the speed and scale of mineralization process of a wide range of plastics that are commercially obtained alternative materials were sought out during the process of an anaerobic digestion, composting and soil incubation. The extent of biodegradability was evaluated by critically calculating the scale of carbon mineralized during the process from these materials while incubation under the conditions that imitated those three spaces and by testing of the materials by inspect electron micrographic. The outcome showed that during those 660 days of soil incubation, fundamental mineralization was observed for the material of poly-hydroxyalkanoate plastics; plastics that are starch based and for materials which were made from compost. Moreover, only the plastic based on poly-hydroxyalkanoate-were biodegraded at a speed that is similar to the positive control. Polymers that are synthetic biodegradable have found more resourceful as well as various biomedical and other applications owing to their tailor able plot or improvement. Biodegradable polymers now have been extensively utilized and extensively encouraged the enlargement of biomedical fields due to the tremendous abilities of being biocompatible and biodegradable. The enlargement of the fields of biotechnology and technological improvement of medical field has imposed higher demands of bio-medical materials. Now a day the biodegradable polymers with novel character and specific properties are on high demand.

Simulating the effects of soil temperature and soil moisture on CO2 and CH4 emissions in rice straw-enriched paddy soil

Paddy soil from a site in northeast China was incubated with 13C-labeled rice straw in a laboratory study, and the effects of soil temperature and moisture on CO2 and CH4 emissions were measured using stable isotope ratio mass spectrometry. Aerobic incubation experiments were conducted at three soil temperatures (−10 °C, 0 °C, and 10 °C) and two soil moistures (60% and 100% water-filled pore space (WFPS)) in a laboratory for 24 weeks to simulate the rice-fallow season. An anaerobic incubation experiment was carried out for 16 weeks under a soil temperature of 25 °C and a 1 cm submerged layer to simulate the rice-growing season. Our results showed that increases in both soil temperature and soil moisture significantly promoted the cumulative CO2 emissions from rice straw during aerobic incubation. Furthermore, during anaerobic incubation, the cumulative emissions of CO2 and CH4 from rice straw decreased with increasing aerobic incubation soil temperature and soil moisture. The CO2 and CH4 emission ratios from rice straw throughout the incubation duration ranged from 6.6–15.7% and 0.0–3.0%, respectively. The addition of rice straw promoted a priming effect on native soil organic carbon (SOC) mineralization and produced CO2 emissions, which positively impacted priming during the aerobic (rice-fallow season) and anaerobic incubation (rice-growing season). The positive priming effect of rice straw on the CO2 emission duration ranged from 75.0% to 274.3% by the end of the 40-week incubation period. Furthermore, the aforementioned effect first increased and then decreased as the aerobic incubation soil temperature increased, with the greatest effect at 0 °C and lowest at 10 °C. These results suggest that high temperature during the rice-fallow season promotes the decomposition of rice straw C and leads to a decreased positive priming effect on native SOC during the rice-fallow and rice-growing seasons under the seasonal conditions of northeast China, and that it also leads to decreased CH4 production during the rice-growing season. These results have scientific significance for rational utilization of rice straw and mitigation of greenhouse effect in northeast China.

Biogas from Tannery Solid Waste Anaerobic Digestion Is Driven by the Association of the Bacterial Order Bacteroidales and Archaeal Family Methanosaetaceae.

The search for renewable energies has been one of the biggest challenges of the last decades. Sludge and solid wastes of many sources have been used to produce biogas of high calorific value. Thus, this work aimed to evaluate the biogas production of solid waste originating from a tannery that uses chromium salts as a tanning agent and to characterize the physicochemical parameters and microbial composition of the biogas-producing biomass. Wastes were collected and the parameters were evaluated at the initial and final time points of the anaerobic incubation process. At the end of 150days, there was a production of 26.1mLg-1 VSS of biogas with 52% of methane. The highest amount of biomethane observed was related to the archaeal family Methanosaetaceae and bacterial order Bacteroidales. Knowledge about changes in the microbial composition can provide tools for manipulation, isolation, and inoculation of the microorganisms inside the bioreactors to maximize methane production.

Microbial communities in anaerobic digesters change over time and sampling depth.

Anaerobic digestion (AD) is a process resulting from the anaerobic metabolism of specific microorganisms that produce an eco-friendly type of energy and a stabilized soil fertilizer. We described the microbial communities and their changes in three depths of BioKöhler® biodigester, fed with cattle manure for 18days, under anaerobic incubation at the psychrophilic temperature range (~ 20°C). During the experiment, the maximum methane content in the raw biogas was 79.9%. Non-metric multidimensional scaling (MDS) showed significant differences among microbial communities in the bottom, medium, and upper depths. Considering all the periods of incubation, the microbial communities changed until the eighth day, and they remained stable from eighth to seventeenthdays. Bacteroidetes, Firmicutes, and Synergistetes were the most abundant phyla in samples, representing approximately 41% of the total OTUs. The relative abundance of the phyla Euryarchaeota, Actinobacteria, Firmicutes, and Verrucomicrobia changed from bottom to medium sampling points. Moreover, Crenarchaeota differed in frequencies from medium to upper, and Acidobacteria from bottom to upper samples. Lentisphaerae, Chloroflexi, and LD1 were different solely at the bottom, whereas OP9 and Tenericutes only in the medium. Psychrophilic AD performed in this work removed pathogens like Salmonella and Escherichia, as observed at the digestate analyzed. This type of treatment of raw manure besides producing eco-friendly energy efficiently also generates a stabilized and safe biomass that can be used as fertilizer in soils.

Light inhibition of carbon mineralization associated with iron redox processes in calcareous paddy soil

The iron redox cycle is closely tied to the fate of carbon in terrestrial ecosystems, especially paddy soils. Varies diurnally and seasonally, light—the crucial environmental factor—may be a fundamental factor elucidating temporal and spatial variabilities of carbon-containing gases emission. The role of sunlight in the iron-mediated carbon cycle, however, has not been fully elucidated. We conduct this study to test the role of light in the iron-mediated carbon cycling. In this study, we conducted anaerobic incubation experiments of a calcareous paddy soil in serum vials under alternating dark and light conditions. The dynamic evolution of the carbon and iron contents was evaluated by measuring the CO2, CH4, and O2 concentrations in the headspace of the vials, as well as the water-soluble inorganic carbon, microbial biomass carbon, and HCl-extractable ferrous iron contents in soil slurries. We also analyzed the soil microbial community structure by high-throughput 16S rRNA gene sequencing. The results highlighted the positive correlation between carbon mineralization and ferric iron reduction under dark conditions. Under light conditions, however, ferrous iron was oxidized by the O2 generated via oxygenic photosynthesis of phototrophic bacteria such as Cyanobacteria, along with a decreased production of CO2, CH4, and water-soluble inorganic carbon. The abundance of Cyanobacteria positively correlated to O2 levels and MBC content significantly. Light-induced periodic variations in the redox conditions facilitated carbon fixation in microbial biomass and up to 31.79 μmol g−1 carbon was sequestrated during 30 days light incubation. These results indicate that light inhibits the emission of carbon-containing greenhouse gases associated with the iron redox cycle in calcareous paddy soil. Assimilation of inorganic carbon by phototrophs may responsible for the inhibition of carbon mineralization. Our study suggests that procedures allowing more light to reach the soil surface, for instance, reducing the planting density, may mitigate greenhouse gas emissions and promote carbon sequestration in paddy soils.

Anti-caries effect of resin infiltrant modified by quaternary ammonium monomers

ObjectivesResin infiltrant is used in early enamel caries. However, commercial resin infiltrant lacks persistent antibacterial activity. Dimethylaminododecyl methacrylate (DMADDM) was added to resin infiltrant to give it sustainable antibacterial properties and inhibit demineralization. MethodsAfter the application of resin infiltrant to bovine enamel, cytotoxicity, surface roughness, and aesthetics were assessed. A multi-species biofilm was incubated on the enamel disk before and one month after microbial-aging. After a 48-h anaerobic incubation, biomass accumulation, metabolic activity, and lactic acid were analyzed using a crystal violet assay, an MTT (3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and a lactic acid assay. Biofilm structure and composition were determined by live/dead staining, exopolysaccharide (EPS) staining, scanning electron microscopy (SEM), and quantitative polymerase chain reaction (qPCR). The depth and content of demineralization were tested by transverse microradiography (TMR). ResultsIncorporating DMADDM did not increase the cytotoxicity or change the physical properties when the mass fraction of the DMADDM was 2.5–10 %. The modification decreased the amount of bacterial biofilm, metabolic activity, lactic acid production, EPS, and the proportion of Streptococcus mutans in the biofilms. It also provided anti-demineralization effects. The surface roughness and antibacterial ability were not changed after one month of microbial-aging. ConclusionThe incorporation of DMADDM improved the antibacterial and anti-demineralization effects of the material. It demonstrated a sustained antibacterial effect. Clinical significanceThe antibacterial modification might be a potential choice for future clinical applications to inhibit early enamel caries.

Mercury methylation potential in a sand dune on Lake Michigan's eastern shoreline

Lake Michigan hosts the largest freshwater sand dune system in the world and is economically important for the fishery industry and tourism. Due to industrial pollution and atmospheric mercury (Hg) deposition, toxic levels of methylmercury (MeHg) have been found in the Lake biota, but little information is known regarding MeHg sources and Hg methylation potential in the shoreline sand dunes. We conducted anaerobic incubation experiments with beach sands collected from Ludington, Michigan, and examined the effects of organic carbon substrate addition, inorganic nitrogen, and mineral magnetite on Hg methylation. Despite nutrient poor and low-organic carbon conditions, appreciable Hg methylation activity coupled with carbon degradation was observed in the sands. Addition of acetate as a carbon source substantially increased MeHg production from 2 to 380 ng/kg sediment while acetate was rapidly degraded in the first 19 days of incubation. Ammonium addition showed little influence on carbon degradation or Hg methylation, whereas iron oxide addition (~1% dry weight) significantly inhibited both carbon degradation and MeHg production (by up to 90%), highlighting strongly coupled interactions between microbes, carbon substrates, and minerals. This research demonstrates the potential of microbial Hg methylation in the sand dunes, which may play a role in MeHg input and bioaccumulation in the Lake Michigan ecosystem.

The Effects of pH, Temperature, and Humic-Like Substances on Anaerobic Carbon Degradation and Methanogenesis in Ombrotrophic and Minerotrophic Alaskan Peatlands

Methane production usually increases from the acidic sphagnum-dominated ombrotrophic peatlands to minerotrophic ones with more neutral pH and higher coverage of vascular plants. Along this ombrotrophic–minerotrophic gradient, pH, microbial communities, and properties of dissolved organic matter in porewater all vary greatly. The hydrographic change resulted from permafrost thaw and projected global warming can potentially connect the minerotrophic and ombrotrophic sites via porewater and turn acidic bogs to minerotrophic fens. It is thus very important to investigate how the anaerobic carbon degradation processes respond to changes in fundamental factors like pH, temperature, properties of dissolved organic matter, and microbial communities resulted from such hydrographic change. In this study, one ombrotrophic (pH = 3.9) and one minerotrophic peatland site were sampled in Fairbanks, Alaska in Sep 2017 and a 42-day-period anaerobic laboratory incubation was conducted to study the changes in anaerobic carbon degradation processes including primary and secondary fermentation, methanogenesis, and acetogenesis when pH, temperature, and porewater were manipulated individually and a combination of two or three of these factors. The results suggested lowering pH would inhibit many anaerobic carbon degradation processes in the minerotrophic peatland except primary fermentation. Elevating pH in the ombrotrophic site did not stimulate its methanogen community, but primary fermentation responded better with increasing pH than with increasing temperature alone. Replacing the porewater in the minerotrophic site with that from the ombrotrophic site with high aromaticity did not inhibit methanogenesis but potentially brought in highly efficient primary fermenters. Acetoclastic methanogenesis, acetogenesis, and syntrophy only exist in the minerotrophic site but not at the ombrotrophic one. Porewater from the minerotrophic site could potentially introduce acetoclastic methanogens and syntrophs to the ombrotrophic site but would not make them active unless both pH and temperature were increased. When ground water connects ombrotrophic and minerotrophic peatlands due to thawing of permafrost, secondary fermenters and acetoclastic methanogens could be introduced to acidic bogs and cooperate efficiently to degrade the stored carbon in ombrotrophic peatlands especially under elevated temperature conditions.

Shifts in short-chain fatty acid profile, Fe(III) reduction and bacterial community with biochar amendment in rice paddy soil.

Biochar, a valuable product from the pyrolysis of agricultural and forestry residues, has been widely applied as soil amendment. However, the effect of different types of biochar on soil microorganisms and associated biochemical processes in paddy soil remains ambiguous. In this study, we investigated the impact of biochars derived from different feedstocks (rice straw, orange peel and bamboo powder) on the dynamics of short-chain fatty acids (SCFAs), iron concentration and bacterial community in paddy soil within 90 days of anaerobic incubation. Results showed that biochar amendment overall inhibited the accumulation of SCFAs while accelerating the Fe(III) reduction process in paddy soil. In addition, 16S rRNA gene sequencing results demonstrated that the α-diversity of the bacterial community significantly decreased in response to biochar amendments at day 1 but was relatively unaffected at the end of incubation, and incubation time was the major driver for the succession of the bacterial community. Furthermore, significant correlations between parameters (e.g. SCFAs and iron concentration) and bacterial taxa (e.g. Clostridia, Syntrophus, Syntrophobacter and Desulfatiglans) were observed. Overall, our findings demonstrated amendment with different types of biochar altered SCFA profile, Fe(III) reduction and bacterial biodiversity in rice paddy soil.

Front Cover: Use of Physiologically Based Kinetic Modeling to Predict Rat Gut Microbial Metabolism of the Isoflavone Daidzein to S‐Equol and Its Consequences for ERα Activation

Mol. Nutr. Food Res. 2020, 64, 1900912 DOI: 10.1002/mnfr.201900912 In article 1900912, Qianrui Wang and co-workers predict plasma concentrations of daidzein and its gut microbial metabolite, S-equol, following daidzein ingestion using a PBK model that includes a gut microbial compartment. In vitro anaerobic incubations of rat feces are optimized to derive kinetic parameters of gut microbial metabolism of daidzein to DHD, S-equol, and O-DMA, which are used as input for the PBK model.

The effect of microenvironment in the sediment on phosphorus immobilization under capping with ACPM and Phoslock®.

Currently, in situ capping is a typical popular geoengineering method for eutrophication control. It is crucial to better understand the effect of microenvironment change due to capping, such as amended calcium peroxide material (ACPM) and Phoslock®, on phosphorus (P) adsorption and immobilization under the addition of external P. The microenvironment in sediment was presented by the concentration of O2, NH4+, and Fe2+ and microbial activity. The P removal and immobilization were also analyzed. The results show that the stronger oxidation in the microenvironment under the capping with ACPM was due to the higher reduction of NH4+ and Fe2+ and the higher increase of microbial activity, compared to Phoslock®. Although, under the capping of ACPM, less amount of external P was removed and there was a faster release of sedimentary P, compared to Phoslock®, ACPM improved the transformation of P from mobile P fractions to inert P fractions. In addition, sedimentary P under the capping of ACPM presents less release than that under the capping of Phoslock® during the anaerobic incubation. However, the settlement of suspended solids decreased the function of capping. All these results indicated that the mechanism of P removal and immobilization was different under the capping of ACPM and Phoslock®.

Effects of high concentrations of sulfate on dissolved organic matter in paddy soils revealed by excitation-emission matrix analyzing

The problem of sulfate pollution is becoming increasingly serious in freshwater and wetlands. Since paddy fields are the largest constructed wetland in Earth’s surface, the increased sulfate input may have great effect on dissolved organic matter (DOM) in paddy soils. To understand these effects, a 24-day anaerobic incubation experiment was conducted with four Chinese paddy soils amended with high concentrations (0, 10, 25, 50, and 100 mmol L−1) of Na2SO4. Dissolved organic carbon (DOC) and chlorophyll a (Chl a) concentrations were determined after incubation. Parallel factor analysis (PARAFAC) of the excitation–emission matrix (EEM) spectra was used to analyze the DOM composition. In all four soils, DOC concentrations generally increased with increasing sulfate concentration, while the Chl a concentrations decreased. The EEM spectra of DOM were resolved into four components by PARAFAC. With increasing sulfate concentration, the proportion of the ultraviolet C humic acid-like compound decreased and the tyrosine-like compound increased in two algae-rich soils (Sichuan and Tianjin). No obvious variation was observed in the humification index (HIX) or the ratio of peak β to peak α (β:α) in any soils with added sulfate. Specific ultra-violet absorbance at 254 nm (SUVA254) decreased with increasing sulfate concentration in Jilin, Tianjin, and Ningxia soils, and the fluorescence index (FI) decreased in two algae-rich soils. In conclusion, although sulfate addition increased the DOC concentration, the DOM composition depended more strongly on soil type and physicochemical properties than sulfate. Sulfate addition only affected soil DOM origin and composition by inhibiting algal growth in algae-rich paddy soils.

Thiolated arsenic species observed in rice paddy pore waters

The accumulation of carcinogenic arsenic in rice, the world’s main staple crop, represents a health threat to millions of people. The speciation of arsenic controls its mobility and bioavailability and therefore its entry into the food chain. Inorganic and methylated oxyarsenic species have been a focus of research, but arsenic characterization in the field has largely ignored thioarsenates, in which sulfur takes the place of oxygen. Here, on the basis of field, mesocosm and soil incubation studies across multiple paddy soils from rice cultivation areas in Italy, France and China, we find that thioarsenates are important arsenic species in paddy-soil pore waters. We observed thioarsenates throughout the cropping season, with concentrations comparable to the much-better-investigated methylated oxyarsenates. Anaerobic soil incubations confirmed a large potential for thiolation across a wide diversity of paddy soil types in different climate zones and with different parent materials. In these incubations, inorganic thioarsenates occurred predominantly where soil pH exceeded 6.5 and in the presence of zero-valent sulfur. Methylated thioarsenates occurred predominantly at soil pH below 7 and in the presence of their precursors, methylated oxyarsenates. High concentrations of dissolved iron limited arsenic thiolation. Sulfate fertilization increased thioarsenate formation. It is currently unclear whether thiolation is good or bad for rice consumption safety. Nevertheless, we highlight thiolation as an important factor to arsenic biogeochemistry in rice paddies. Thioarsenates are found in the pore waters of rice paddy fields, comparable in concentration to methylated oxyarsenates, according to field, mesocosm and soil incubation studies.

Risk Factors and Outcomes of Cutibacterium acnes Postoperative Central Nervous System Infection: A Case–Control Study

Cutibacterium acnes has emerged as a significant cause of postoperative central nervous system infections (PCNSIs). We sought to determine risk factors and outcomes associated with C.acnes PCNSI. This was a single-center 1:1 case-control study of patients with monobacterial C.acnes-associated PCNSI (cases) and unmatched controls with PCNSI caused by aerobic organisms. Patient and procedure-related characteristics were compared between groups. The main outcome was cure at 90 days after diagnosis. Mortality and neurologic disability were secondary outcomes. We identified 13 patients with C.acnes PCNSI and 13 controls. All patients had postoperative intracranial abscess. Onset of infection was significantly later for cases versus controls (median and range, 22 [19-116] days and 15 [1-27] days, respectively; P= 0.002). Prolonged anaerobic incubation was required for C.acnes isolation (median, 8 days vs. 2 days for aerobic pathogens; P<0.0001). The use of sealant and implants, fever at presentation, and white blood cell and C-reactive protein levels were similar between the 2 groups. All patients underwent surgical drainage. Patients received a median of 4 antibiotic drugs and 85 antibiotic days of treatment, with no significant between-group differences. Cure at 90days was achieved for 10 patients (76.9%) with C.acnes PCNSI and 11 (84.6%) controls (P= 1.0). C.acnes PCNSI presents later than infection with aerobic bacteria but is associated with similar risk factors and clinical outcomes. These results underscore the importance of prolonged anaerobic incubation to optimize the recovery of C.acnes in the laboratory.