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17461. 题目: Experimental metatranscriptomics reveals the costs and benefits of dissolved organic matter photo‐alteration for freshwater microbes | |||||
17462. 题目: Effect of salinity on removal performance in hydrolysis acidification reactors treating textile wastewater Hydrolysis acidification (HA) is a classical method for synthetic textile wastewater treatment. However, the salinity effect on the functional mechanism of the microorganisms carrying out HA has rarely been researched. In the present study, the salinity effect on the dye removal efficiency was investigated, and the soluble microbial products (SMP), extracellular polymeric substances (EPS), and microbial community were analyzed at different salinities. The dye and COD removal rates in the HA reactor decreased with increasing salinity. Volatile fatty acids (VFAs) accumulated. The remarkable increases in SMP and EPS were found at high salinity, mainly because more polysaccharides were synthesized than protein. In addition, sequencing analysis showed that high salinity altered the microbial community structure, and Lactococcus, Raoultella and Enterococcus were the decolorizing bacteria at high salinity. This work will improve the understanding of the influence of salinity on the removal efficiency and microbial community during HA. | |||||
17463. 题目: Lignin lags, leads, or limits the decomposition of litter and soil organic carbon | |||||
17464. 题目: Nitrogen input weakens the control of inundation frequency on soil organic carbon loss in a tidal salt marsh The soil carbon (C) sequestration capacity of salt marshes is of considerable importance with respect to the mitigatiing the potentially detrimental consequences of global climate change. Given that tidal salt marshes are subjected to periodic cycles of inundation, it is assumed that soil C cycle in these marshes is expected to be controlled to varing extent by changes in soil moisture and salinity induced by the alternating patterns of drying and rewetting. In addition, with increases in the extent and severity of nitrogen (N) eutrophication becomes serious, we predicted that soil organic carbon (SOC) loss in tidal salt marshes is likely to be highly responsive to increased N loading. In this study, we conducted a two-factor mesocosm experiment (simulated inundation and N input in a tidal salt marsh) to determine the interactive effects of N eutrophication and inundation frequency on CO2 and CH4 emissions and dissolved organic carbon (DOC) contents. Our results showed that increased inundation frequency led to lower levels of CO2 emission but greater CH4 emission, whereas N input weakened the effects of changes in inundation frequency on CO2 and CH4 emissions. Moreover, N input was found to modify CO2 and CH4 emission in response to variations in soil moisture. We also observed an enhancement of soil DOC loss in response to increasing inundation frequency, and that DOC loss in the surface soil was considerably greater than that in subsurface soil. Further, as inundation frequency increased, we detected changes in the relationship between soil DOC and CO2 and CH4. Our findings highlighted that vertical variation in soil moisture induced by inundation is a key factor controlling SOC loss in tidal salt marshes, although N input can weaken this control. | |||||
17465. 题目: Assessing Disinfection Byproduct Risks for Algal Impacted Surface Waters and the Effects of Peracetic Acid Pre-Oxidation | |||||
17466. 题目: Dissolved organic matter characteristics in soils of tropical legume and non-legume tree plantations Dissolved organic matter (DOM) drives many fundamental biogeochemical processes (e.g., carbon storage, nutrient cycling, and soil development) in forest soil. However, the molecular-level characteristics of DOM derived from different types of tropical forest soils are poorly understood. Here, water samples at different soil depths (0, 20, and 40 cm) from tropical legume (Acacia auriculiformis, AA) and non-legume (Eucalyptus urophylla, EU) tree plantations were analyzed using absorption and fluorescence spectroscopy, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and solution-state 1H nuclear magnetic resonance (NMR) spectroscopy. The FT-ICR MS results indicated that DOM persisted in the soil, but its molecular composition notably shifted from low-mass (150–300 Da) and more-aromatic molecules to middle- (300–450 Da) and high-mass (>450 Da) and less-aromatic molecules with increasing soil depth. This was primarily mediated by consumption and mineral sorption of low-mass plant-derived DOM (e.g., low-mass carbohydrates and polyphenols) and further formation of larger microbial products (e.g., protein-like and lipid-like compounds). In addition, a higher abundance of microbial-derived molecules (e.g., protein-like and carboxyl-rich alicyclic molecules) was found at the legume plantation relative to the non-legume plantation, which suggests faster microbial turnover of DOM. Also, the legume plantation had greater enrichment of middle- and high-mass and condensed aromatic-like DOM components in soils. These findings improve our understanding of the drivers that mediate the response of DOM to soil depth and tree species in tropical plantations. | |||||
17467. 题目: Elevated temperature increases the accumulation of microbial necromass nitrogen in soil via increasing microbial turnover Microbial‐derived nitrogen (N) is now recognized as an important source of soil organic N. However, the mechanisms that govern the production of microbial necromass N, its turnover, and stabilization in soil remain poorly understood. To assess the effects of elevated temperature on bacterial and fungal necromass N production, turnover and stabilization, we incubated 15N‐labeled bacterial and fungal necromass under optimum moisture conditions at 10 ℃, 15 ℃ and 25 ℃. We developed a new 15N tracing model to calculate the production and mineralization rates of necromass N. Our results showed that bacterial and fungal necromass N had similar mineralization rates, despite their contrasting chemistry. Most bacterial and fungal necromass 15N was recovered in the mineral‐associated organic matter (MAOM) fraction through microbial anabolism, suggesting that mineral association plays an important role in stabilizing necromass N in soil, independently of necromass chemistry. Elevated temperature significantly increased the accumulation of necromass N in soil, due to the relatively higher microbial turnover and production of necromass N with increasing temperature than the increases in microbial necromass N mineralization. In conclusion, we found elevated temperature may increase the contribution of microbial necromass N to mineral stabilized soil organic N. | |||||
17468. 题目: Herbivores stimulate respiration from labile and recalcitrant soil carbon pools in grasslands of Yellowstone National Park Quantifying the effects of grazing on soil organic carbon (SOC) decomposition is of crucial importance for understanding soil C dynamics. However, less attention has been paid to the pool‐specific SOC decomposition and the underlying factors associated with each C pool, representing critical knowledge gaps on soil C dynamics. In this study, we applied a state‐of‐the‐art Bayesian data assimilation technique to re‐analyze previous soil incubation data to examine how herbivores influenced the fraction and cumulative respiration of labile and recalcitrant soil C pools from seven edaphically diverse sites in Yellowstone National Park, whereas those variables were not explored in the earlier study. Our results showed that grazing significantly increased cumulative respiration from both labile and recalcitrant C pools. Greater cumulative respiration from the labile C pool was related to grazers increasing labile C pool fractions, while higher cumulative respiration from the recalcitrant C pool was associated with grazers accelerating the decomposition rate of the recalcitrant C pool. Cumulative respiration from both labile and recalcitrant C pools was positively correlated with shoot biomass, soil gravimetric moisture, and soil C and nitrogen content. Our results underscore how knowledge of pool‐specific SOC decomposition can provide a better mechanistic understanding of soil C dynamics along topo‐edaphic gradients in grazed grassland. | |||||
17469. 题目: The relationship of structure and organic matter adsorption characteristics by magnetic cattle manure biochar prepared at different pyrolysis temperatures The preparation of magnetic biochar from cattle manure is an effective way for resource utilization. Fe3+-impregnated magnetic biochar for organic matter adsorption was synthesized by pyrolysis at 200, 400, and 600 °C respectively to investigate the influence of pyrolysis temperature on the structure and adsorption properties of magnetic biochar and their interrelationship. Congo red (CR) and Methylene blue (MB) were chosen to a representative of acidic and alkaline organics. The analyses showed that the number of functional groups decreased, and the specific surface area and iron oxides content increased with the increase of pyrolysis temperature. Fe3+ was loaded on biochar in form of γ-Fe2O3 and converted into Fe3O4 when the pyrolysis temperature rose from 400 to 600 °C. As the pyrolysis temperature increased from 200 to 600 °C, the adsorption capacities of magnetic biochar to MB first decreased and then increased, whereas that to CR increased gradually. There are three main structural factors affecting the adsorption properties of magnetic biochar: surface area, functional groups, and iron oxides content. The adsorption of magnetic biochar to MB is mainly related to the competitive mechanism of surface area and functional groups. The main factor affecting the adsorption of MB by MCMB200 (magnetic biochar prepared at 200 °C) and MCMB600 (magnetic biochar prepared at 600 °C) is functional groups and surface area, respectively. The adsorption of CR by magnetic biochar is mainly related to the synergistic mechanism of surface area and iron oxides content. | |||||
17470. 题目: Exploring the microbial mechanisms of organic matter transformation during pig manure composting amended with bean dregs and biochar This study researched the impacts of biochar (B) and bean dregs (BD) on organic matter degradation and humification, as well as the bacterial community and functional characteristics during pig manure (PM) composting. The temperature, pH, and dissolved organic carbon (DOC) were reached the maturity of compost. Results indicated that BD+B treatment promoted organic matter degradation and increased humic acid content by 19.5-25.1% from the control (CK). Additionally, the bacterial communities were determined by high-throughput sequencing, and their metabolic functions were evaluated through the phylogenetic investigation of communities by reconstructing unobserved states (PICRUSt). BD+B influenced the microbial community structure of compost, and the PICRUSt results indicated that BD+B strengthened the metabolism of carbohydrates and amino acids. Redundancy analysis (RDA) was conducted, and a positive correlation was observed between organic matter transformation and temperature, pH, DOC, and community structure. Therefore, regulating these compost properties can effectively promote organic matter transformation during composting. | |||||
17471. 题目: In-situ fluorescence spectroscopy indicates total bacterial abundance and dissolved organic carbon We explore in-situ fluorescence spectroscopy as an instantaneous indicator of total bacterial abundance and faecal contamination in drinking water. Eighty-four samples were collected outside of the recharge season from groundwater-derived water sources in Dakar, Senegal. Samples were analysed for tryptophan-like (TLF) and humic-like (HLF) fluorescence in-situ, total bacterial cells by flow cytometry, and potential indicators of faecal contamination such as thermotolerant coliforms (TTCs), nitrate, and in a subset of 22 samples, dissolved organic carbon (DOC). Significant single-predictor linear regression models demonstrated that total bacterial cells were the most effective predictor of TLF, followed by on-site sanitation density; TTCs were not a significant predictor. An optimum multiple-predictor model of TLF incorporated total bacterial cells, nitrate, nitrite, on-site sanitation density, and sulphate (r2 0.68). HLF was similarly related to the same parameters as TLF, with total bacterial cells being the best correlated (ρs 0.64). In the subset of 22 sources, DOC clustered with TLF, HLF, and total bacterial cells, and a linear regression model demonstrated HLF was the best predictor of DOC (r2 0.84). The intergranular nature of the aquifer, timing of the study, and/or non-uniqueness of the signal to TTCs can explain the significant associations between TLF/HLF and indicators of faecal contamination such as on-site sanitation density and nutrients but not TTCs. The bacterial population that relates to TLF/HLF is likely to be a subsurface community that develops in-situ based on the availability of organic matter originating from faecal sources. In-situ fluorescence spectroscopy instantly indicates a drinking water source is impacted by faecal contamination but it remains unclear how that relates specifically to microbial risk in this setting. | |||||
17472. 题目: Alkaline amendments improve the health of soils degraded by metal contamination and acidification: Crop performance and soil bacterial community responses Soil degradation due to heavy metal contamination and acidification has negative effects on soil health and crop growth. Many previous studies have tried to improve the growth of crops and decrease their metal uptake. The recovery of soil health, however, has rarely been focused in soil remediation. In this study, a pot trial was conducted with lettuce (Lactuca sativa L.) growing in heavy metal contaminated and acidic soils, to examine the effects of alkaline amendments (limestone, LS; calcium magnesium phosphate fertilizer, Pcm) and organic amendments (cow manure compost, CMC; biochar, BC) on the growth of lettuce and on the availability of heavy metals, enzyme activities, and bacterial community structures in the soils. The results showed that, in comparison with the CMC and BC treatments, LS and Pcm were more effective at improving lettuce growth and reducing metal concentrations in shoots. Urease and catalase activities in LS and Pcm amended soils were consistently higher than in those with CMC and BC. Additionally, the alkaline amendments dramatically improved the bacterial diversity and shaped more favorable bacterial community structures. Proteobacteria and Gemmatimonadetes were predominant in soils amended with alkaline treatments. The beneficial bacterial genera Gemmatimonas and f_Gemmatimonadaceae, which are vital for phosphate dissolution, microbial nitrogen metabolism, and soil respiration, were also enriched. The results suggest that alkaline amendments were superior to organic amendments, and thus may be useful for the future recovery of soil functions and health under heavy metal contamination and low pH. | |||||
17473. 题目: Cascading multiscale watershed effects on differential carbon isotopic characteristics and associated hydrological processes Understanding land-use change accompanied by anthropogenic activities under alterations in watershed size regulations or differential carbon (C) isotope characteristics remain a challenge in C cycling research. In this study, we investigate changes in the export of C composition and its isotopic characteristics at multiple scales in a subtropical cascading watershed in China. Results show that C concentrations in rainfall and dissolved total carbon (DTC), dissolved organic carbon (DOC) and δ13C in runoff seasonally fluctuate at a temporal scale. On average, the δ13C from silicate rock weathering was 31–32%, contributing the largest amount of δ13C in the different watersheds. Moreover, the contribution of isotopic composition from atmospheric deposition to the δ13C fraction increased as watershed size increased, while the corresponding contribution from soil organic matter (SOM) decomposition decreased. On the other hand, anthropogenic activities play a dominant role in the isotopic composition of large watersheds. In addition, the correlation coefficient between C transport via runoff and the δ18O value in rainfall increased as watershed size increased. This indicated that as a source rainfall had an obvious influence on C transport in runoff according to proportional values measured in event and pre-event water. | |||||
17474. 题目: Use of spectroscopic indicators for the monitoring of bromate generation in ozonated wastewater containing variable concentrations of bromide Time-resolved monitoring of bromate and other by-products formed into effluents treated with ozone or advanced oxidation processes in wastewater treatment plants (WWTPs) is time-consuming and expensive. This study examined whether concentrations of bromate formed in wastewater after ozonation in the presence of widely varying bromide levels (from ca. 0.7–21.2 mg/L) can be quantified based on measurements of changes in optical properties (differential UV absorbance (ΔUVA), spectral slopes, total or regional fluorescence) of the ozonated samples. Batch ozonation was carried out using a secondary effluent produced at a major wastewater treatment plant located in the Metropolitan Seattle Area. The tests involved raw and bromide-spiked samples treated with ozone doses from 0.1 to 1 mg O3/mg DOC. Measurements of the absorbance at 254 nm (UVA254), fluorescence and bromate concentrations were performed on the treated samples. In the ozonated wastewater the concentration of bromate increased approximately linearly, from <10 ppb to ca. 200 ppb, without showing the lag phase characteristic for lower ozone doses (<0.4 mg O3/mg DOC) that was observed in previous studies carried out with concentrations of bromide in the range of 0.05–0.5 mg/L. The highest bromide concentrations used in this study (>10 mg/L) tended to inhibit the generation of bromate. Relative reduction of UVA254 and total fluorescence (TF) were found to be good predictors of bromate generation. Specifically, exponential curves could adequately fit the non-linear relationships found to exist between the concentrations of bromate and the relative reductions of the UV254 and TF, for any initial bromide concentrations used in this study. Little formation of bromate was found to occur for reduction ranges for UVA254 and TF of 30–40% and 70–80% respectively. Conversely, rapid increases in bromate generation were observed when the decrease of UVA254 or TF exceeded these threshold values. | |||||
17475. 题目: Effects of biochar and straw on greenhouse gas emission and its response mechanism in seasonally frozen farmland ecosystems Freeze-thaw cycle promotes the decomposition of soil organic matter in cold regions, causing carbon and nitrogen to be emitted in the forms of CO2, CH4 and N2O, resulting in positive feedback to climate warming. To effectively regulate greenhouse gas emissions, four different regulation modes, namely, biochar addition (BA), straw addition (SA), combined biochar and straw (CBS) and a natural control (BL), were established. The characteristics of soil greenhouse gas emissions under different treatments and their response relationships to soil water, heat, carbon and nitrogen were explored. The results revealed that the SA and CBS treatments effectively inhibited the substantial reduction in soil temperature, moisture content, inorganic nitrogen and dissolved organic carbon during the freezing period; among them, the average soil inorganic nitrogen under the SA and CBS treatments increased by 15.36 and 11.62 mg·kg−1 compared to that in the BL treatment, respectively. Simultaneously, both N2O and CO2 emission fluxes were low, and the difference was small under the various treatments. However, the soil showed an absorption trend with respect to CH4, and the BA and CBS treatments promoted this effect; furthermore, the response relationships between CH4 and soil water, heat and carbon were enhanced. During the thawing period, the CBS treatment most effectively promoted the increase in soil water, heat, carbon and nitrogen, while it inhibited the flux of CH4 and N2O in soils, and the average CH4 emission flux under the CBS treatment decreased by 8.25 ~ 30.75 μg∙kg−1 relative to that under the other treatments. Concurrently, the responses of CH4 and N2O emission fluxes to soil water, heat, carbon and nitrogen were weakened under this treatment. Although the CBS treatment increased the CO2 emissions flux during this period, in view of the overall effect of the entire freeze–thaw period, the CBS treatment most effectively reduced the global warming potential (GWP) of the soil. Therefore, it is suggested that the joint application of biochar and straw is the most effective strategy for greenhouse gas budget management and soil nutrient restoration in seasonally frozen areas. | |||||
17476. 题目: Prediction of soil organic and inorganic carbon concentrations in Tunisian samples by mid-infrared reflectance spectroscopy using a French national library Mid-infrared reflectance spectroscopy (MIRS, 4000–400 cm−1) is being considered to provide accurate estimations of soil properties, including soil organic carbon (SOC) and soil inorganic carbon (SIC) contents. This approach has mainly been demonstrated by using datasets originating from the same area A, with similar geopedological conditions, to build, validate and test prediction models. The objective of this study was to analyse how MIRS performs when applied to predict SOC and SIC contents, from a calibration database collected over a region A, to predict over a region B, where A and B have no common area and different soil and climate conditions. This study used a French MIRS soil dataset including 2178 topsoil samples to calibrate SIC and SOC prediction models with partial least squares regression (PLSR), and a Tunisian MIRS topsoil dataset including 96 soil samples to test them. Our results showed that when using the French MIRS soil database, i) the SOC and SIC of French validation samples were successfully predicted using global models (R2val = 0.88 and 0.98, respectively), ii) the SIC of Tunisian samples was also predicted successfully both using a global model and using a selection of spectral neighbours from the French calibration database (R2test of 0.96 for both), iii) the SOC of Tunisian samples was predicted moderately well by global model (R2test of 0.64) and a transformation by natural logarithm of the calibration SOC values significantly improved the SOC prediction of Tunisian samples (R2test of 0.97), and iv) a transformation by natural logarithm of SOC values provided more benefit than a selection of spectral neighbours from the French calibration database for predicting Tunisian SOC values. Therefore, in the future, MIRS might replace conventional physico-chemical analysis techniques, or at least be considered as an alternative technique, especially when optimally exhaustive calibration databases will become available. | |||||
17477. 题目: Spartina alterniflora invasion impacts denitrifying community diversity and functioning in marsh soils This study aimed to investigate soil denitrifying bacterial and fungal community structures and potential denitrification rates in the coastal marsh soils of Eastern China across Spartina alterniflora invasive gradients (i.e. native (Nat), native-Spartina coexisted (Ecot) and Spartina-dominated (Mono) vegetations, respectively). Plant biomass and soil chemical properties were also analyzed to understand the patterns of spatial variability of structure and function of denitrifier communities across the studied gradients. Results indicated that total, bacterial and fungal potential denitrification rates (TDR, BDR and FDR) were 5.5, 3.5 and 1.5 times greater respectively in the Mono soil than in the Nat soil. Denitrifying bacterial richness, evenness and α-diversity were 2.0, 1.3 and 1.3 times greater in the Mono soil than those in the Nat soil, while only the richness among denitrifying fungal community parameters was 1.4 times greater in the Mono soil than that in the Nat soil. Plant biomass, soil organic carbon and pH were the most important factors influencing denitrifying bacterial and fungal community structures and functions. Denitrifying bacterial community composition was related closely to BDR and TDR, while denitrifying fungal community composition was not related to FDR and TDR, thus showing that the denitrifying bacterial community is a better predictor of denitrification function following Spartina invasion. | |||||
17478. 题目: Iron index as an organic matter decay intensity indicator in a shallow groundwater system highly contaminated with phenol (case study in northern Poland) | |||||
17479. 题目: Estimating soil organic carbon density in Northern China's agro-pastoral ecotone using vis-NIR spectroscopy | |||||
17480. 题目: Humic acid, dextran, and valeric acid representing macromolecules similar to compounds prevailing in treated wastewater induce soil hydrophobicity | |||||
