13241. 题目: Temperature sensitivity of soil organic matter decomposition in response to land management in semi-arid rangelands of Iran
作者: Behzad Behtari, Zeinab Jafarian, Hosseinali Alikhani
摘要: The biotic and abiotic factors can alter the temperature sensitivity of soil organic matter (SOM) decomposition in rangeland areas. This is a key issue that directly affects soil fertility and productivity. On the other hand, most of the rangelands in Iran are involved overgrazing. However, there is a lack of information about these effects, especially, in semi-arid environments. Therefore, the aim of this study was to assess the effect of land management on soil nutrient contents and their stoichiometry on the temperature sensitivity of SOM decomposition (Q10) in semi-arid rangeland ecosystems. Soil samples (at three different soil depths) were collected in adjacent rangeland areas with different management in Iran. Soils were incubated at three different temperatures. The soil heterotrophic respiration was measured using an Alkali absorption method and then was calculated Q10. The decrease in Q10 values was observed with increasing carbon (C), nitrogen (N) and phosphorus (P) of soil content. Changes of Q10 in relation to stoichiometry C:N and P:N showed a linear model and a second-order polynomial model in grazed and ungrazed rangeland respectively. Ungrazed rangeland had the lower Q10 value (0.97) compared to grazed rangeland (1.21). Labile C variability at soil due to effects in land management such as trampling and erosion, altering plant biomass and microbial communities may be able to partly explained variation of Q10 values. Overall, trend of decreasing Q10 values associated with increasing C, N and P contents of soil in all rangeland management can be explained by the high microbial CUE. The obtained results presumably indicated that stoichiometry of C:P:N can play as an important determinant in increase CUE and decrease Q10 in rangeland ecosystems. Overall, the results of this research will valuable for prediction of the condition and succession trend via Q10 and C losses in various grazing management in semi-arid rangeland ecosystems.
13242. 题目: Detection of new long-chain mid-chain keto-ol isomers from marine sediments by means of HPLC APCI-MS and comparison with long-chain mid-chain diols from the same samples
期刊: Organic Geochemistry
作者: Gerard J.M. Versteegh, Julius Lipp
摘要: Long-chain mid-chain-keto-1-ol positional isomers in sediments provide important information on past environments. Unfortunately, we are unable to assess their full potential since conventional GC–MS analysis of sediment extracts is unable to reliably qualify and quantify long-chain mid-chain-keto-1-ol positional isomers, especially if these are of minor abundance. Here, we use NP-HPLC–APCI-MS to separate these isomers at baseline resolution for a given chain-length, providing a reliable alternative method to detect and quantify these molecules. We detected unknown saturated and unsaturated long-chain mid-chain-keto-1-ols and suggest that the C32:1 keto-ol has the keto-group at the C14 position on the basis of the patterns of abundance and retention times. Based on dissimilarities in isomer composition with that of the long-chain mid-chain diols, obtained from the same analysis, we reject the hypothesis that diagenetic oxidation of the mid-chain diol functionality is the major source of the long-chain mid-chain-keto-1-ols. We rather favor the hypothesis that the keto-ols are predominantly produced by currently uncharacterized source organisms.
13243. 题目: Effect of multiple iron-based nanoparticles on availability of lead and iron, and micro-ecology in lead contaminated soil
作者: Dinghua Peng, Bin Wu, Hang Tan, Siyu Hou, Min Liu, Hao Tang, Jiang Yu, Heng Xu
摘要: Although iron nanoparticles (NPs) have been used for environmental remediation of heavy metal, their potential to remediate lead (Pb) contaminated soil and effect on soil micro-ecology is unclear. The purpose of this study was to investigate the potential of nanoscale zerovalent iron (nZVI), nanoscale zerovalent iron supported by biochar (nZVI@BC), ferrous sulfide (FeS-NPs), ferrous sulfide supported by biochar (FeS-NPs@BC), ferriferrous oxide (Fe3O4-NPs) and ferriferrous oxide supported by biochar (Fe3O4-NPs@BC) to remediate Pb contaminated soil and the influences for soil micro-ecology. The results showed that biochar (BC) could improve the crystal shape and superficial area of iron-based nanoparticles. Soil pH values was significantly decreased by FeS-NPs and FeS-NPs@BC, but increased by other iron-nanoparticles. The ability to reduce available Pb concentration showed significant difference among these iron-nanoparticles, that is, the immobilized rate were nZVI by 45.80%, nZVI@BC by 54.68%, FeS-NPs by 2.70%, FeS-NPs@BC by 5.13%, Fe3O4-NPs by 47.47%, Fe3O4-NPs@BC by 30.51% at day 90. Almost all soil enzyme activities in Fe3O4-NPs and Fe3O4-NPs@BC groups were increased, but the majority of the enzyme activities were inhibited in other iron-based nanoparticles groups, while the maximum bacterial number was determined in FeS-NPs group. Furthermore, microbial diversity analysis showed that FeS-NPs has significantly changed microbial community richness and diversity, followed by nZVI and Fe3O4-NPs. Accordingly, our results suggested that nZVI@BC had the best immobilization effect on Pb in high-concentration Pb-contaminated alkaline soil, but the toxic effect of Fe3O4-NPs on soil micro-ecology was relatively minimal.
13244. 题目: Development of correlation spectroscopy (COS) method for analyzing fluorescence excitation emission matrix (EEM): A case study of effluent organic matter (EfOM) ozonation
作者: Huarong Yu, Fangshu Qu, Xiaolei Zhang, Senlin Shao, Hongwei Rong, Heng Liang, Langming Bai, Jun Ma
摘要: Two-dimensional correlation spectroscopy (2DCOS) has been used as a powerful tool for analyzing spectral features, but it has never been applied to fluorescence excitation-emission matrix (EEM) data due to the incompatible dimensions. This study first investigated EEM-COS by reducing the dimensions of the EEM (using parallel factor analysis, PARAFAC) for fitting to 2DCOS (EEM-PARAFAC-COS). The fluorescence changes of effluent organic matter (EfOM) during ozonation were studied using EEM-COS and synchronous fluorescence (SF)-2DCOS. The conventionally used SF-2DCOS proved to be biased due to the intrinsic drawback of SF, while the EEM-PARAFAC-COS gave accurate and trustworthy results. Homo-EEM-PARAFAC-COS indicated that the fluorescence protein-like and fulvic-like substances in EfOM were preferentially ozonated compared to humic-like substances. Hetero-EEM-PARAFAC-COS analyses on the EEM, FTIR, UV–vis absorbance, and size-exclusion chromatography showed that the fluorescence protein-like and fulvic-like substances in EfOM were associated with lower molecular weight (MW, ∼0.95 kDa), UV absorbance at ∼280 nm, and more electron-enriched aromatics (with amide and phenolic groups), which explained their ozonation preference, while humic-like substances were related to carboxylic groups, UV absorbance at ∼255 nm, and organics at MW of ∼4.50 kDa. This work demonstrated the great potential of EEM-PARAFAC-COS in studying fluorescence change and correlating fluorescence with other spectra.
13245. 题目: Aquatic behavior and toxicity of polystyrene nanoplastic particles with different functional groups: Complex roles of pH, dissolved organic carbon and divalent cations
作者: Fan Zhang, Zhuang Wang, Se Wang, Hao Fang, Degao Wang
摘要: Herein we systematically examined the roles of water chemistry (pH, dissolved organic carbon (DOC), and divalent cations) and particle surface functionality that control the aqueous stability, aggregation, and toxicity of engineered nanoplastic particles in simulated natural environmental conditions. Model polystyrene latex nanoparticles (PLNPs) with three different functional groups, namely unmodified (uPLNPs), amine-modified (aPLNPs), and carboxyl-modified (cPLNPs), were investigated. Results indicate that the presence of only DOC increased the surface charge and exhibited negligible effects on the size distribution of the PLNPs in aqueous suspensions. The presence of the divalent cations (Ca2+ and Mg2+) was observed to decrease the surface charge and increase the size of the PLNPs. The coexistence of DOC and the divalent cations enhanced the extent of aggregation of the PLNPs in the water columns. The surface modification and pH were sensitive factors influencing the stability of PLNPs during long-term suspension when DOC and the divalent cations coexisted. Direct visual further testified the conclusions on the combined effects of solution and surface chemistry parameters. Furthermore, in situ transmission electron microscope observations revealed that the enhancement of PLNP aggregation in the presence of DOC and the divalent cation was caused by bridge formation. Toxicity test indicated the PLNPs exhibited acute toxicity and physical damage to Daphnia magna. The more complex the solution conditions, the more toxicity the aPLNPs and cPLNPs. Analysis of mode of toxic action implied that the PLNPs mainly caused the accumulation of oxidative damage to the gut of D. magna.
13246. 题目: Contrasting photoreactivity of β2-adrenoceptor agonists Salbutamol and Terbutaline in the presence of humic substances
作者: Lei Zhou, Mohamad Sleiman, Ludovic Fine, Corinne Ferronato, Pascal de Sainte Claire, Emmanuelle Vulliet, Jean-Marc Chovelon, Guangli Xiu, Claire Richard
摘要: The photodegradation reactions of two typical β2-adrenoceptor agonists, salbutamol (SAL) and terbutaline (TBL), alone, and in the presence of Aldrich humic acid (AHA) or Suwannee River fulvic acid (SRFA) were investigated by steady-state photolysis experiments, laser flash photolysis (LFP), kinetic modeling and quantum calculation. AHA and SRFA (2–20 mgC L−1) accelerated the phototransformation of both SAL and TBL. For SAL, an inhibiting effect of oxygen on the photodegradation was observed that is fully consistent with the main involvement of excited triplet states of HS (3HS*). On the contrary, oxygen drastically enhanced the photodegradation of TBL showing that 3HS* were negligibly involved in the reaction. The involvement of singlet oxygen was also ruled out because of the low reaction rate constant measured between TBL and singlet oxygen. Quantum calculations were therefore performed to explore whether oxygenated radicals could through addition reactions explain the differences of reactivity of TBL and SAL in oxygen medium. Interestingly, calculations showed that in the presence of oxygen, the addition of phenoxyl on TBL led to the formation of adducts and to the loss of TBL while the same addition reaction on SAL partly regenerated the starting compound and at the end degraded SAL less efficiently. This study is of high relevance to understand the processes involved in SAL and TBL phototransformation and the photoreactivity of HS. Moreover, our findings suggest that TBL might be a promising probe molecule to delineate the role of oxygenated radicals.
13247. 题目: Changes in dissolved organic matter composition and dynamics in a subtropical mangrove river driven by rainfall
期刊: Estuarine, Coastal and Shelf Science
作者: Morimaru Kida, Mai Tanabe, Mitsutoshi Tomotsune, Shinpei Yoshitake, Kazutoshi Kinjo, Toshiyuki Ohtsuka, Nobuhide Fujitake
摘要: Dissolved organic matter (DOM) plays an important role in sustaining ecosystem services of mangrove forests through well-described biogeochemical and ecological functions. This study was conducted in the Fukido River (Ishigaki Island, Japan) to better understand the seasonal and episodic changes in DOM concentration and composition in a subtropical mangrove system. Water samples were collected seasonally along a headwater–mangrove–sea transect on 10 occasions from September 2014 through June 2016. DOM was fractionated based on hydrophobicity into two fractions (hydrophobic and hydrophilic) and also analyzed by excitation-emission matrix spectroscopy combined with parallel factor analysis (PARAFAC). Although seasonal changes in DOM concentration and composition were not observed, both hydrophobic and hydrophilic DOM concentrations and levels of the identified three PARAFAC components clearly increased during a typhoon event. It is suggested that episodic increases in freshwater input due to a typhoon caused enhanced leaching of DOM from mangrove litter and dissolution of mangrove soil organic matter (SOM), which was otherwise retained in the mangrove soil by salinity-induced aggregation. The aggregation–dissolution properties of SOM are crucial in determining the magnitude of DOM outwelling and possibly SOM accumulation rate by enhancing advective DOM exchanges. Future studies are needed to evaluate the size of the carbon pool and outwelling of DOM after classifying mangrove forests based on the hydrological regime that influences biogeochemical conditions in the forests.
13248. 题目: Using a coupled geochemical/physical mass balance model to gain insights into the deposition of subrecent evaporites: Searles Valley, California, USA
期刊: Journal of Paleolimnology
作者: Joseph J. Janick, Robert V. Demicco
摘要: Modern and ancient saline lakes are important sites for the deposition of carbonates and evaporites. Here we describe a generalized computer model of chemical sediment production in a closed-basin lake subject to: (1) variable inflow sources through time; (2) variable volumes of these inflows; (3) variable temperature, and; (4) variable evaporation rates through time. We then apply our model to gain insights into some aspects of late Pleistocene evaporite deposits beneath Searles Lake, California, a well-described chemical sedimentary deposit. We tuned our model to match the masses and proportions of the major saline minerals trona and halite deposited in layers circa 32 ka to 24 ka. However, we could not reproduce the thicknesses of mixed siliciclastic, carbonate and organic layers sandwiched between the evaporites. The model is useful for interpreting and constraining the environmental conditions in and around any ancient saline lakes during evaporite deposition where the amounts, mineralogies, and vertical distribution of chemical sediments are known.
13249. 题目: The properties and removal efficacies of natural organic matter fractions by South African drinking water treatment plants
期刊: Journal of Environmental Chemical Engineering
作者: Welldone Moyo, Nhamo Chaukura, Titus A.M. Msagati, Bhekie B. Mamba, Sebastian G.J. Heijman, Thabo T.I. Nkambule
摘要: This study presents an investigation on the fate of natural organic matter (NOM) and its dynamics throughout the treatment train at various drinking water treatment plants (WTP) in South Africa. The characteristics, concentration and removal efficiencies of NOM at various treatment stages on the basis of dissolved organic carbon, UV absorbance, specific ultra-violet absorbance, spectroscopic indices, maximum fluorescence intensity (Fmax), and polysaccharides removal, were studied. The highest polysaccharide concentration was in coastal plants compared to inland plants for the raw water samples. A Parafac model fitting four components was established for the raw waters, and validated based on the split half criteria. The Fmax values of the components was higher for terrestrial humic-like component (C1) and fulvic-like component (C2) than for humic-like components (C3), and for protein-like component (C4). Strikingly, the mean Fmax values for C2 and C3 were higher for plants located on the south west coast of South Africa than the plants located inland. While the humification index and UV254 removal correlated (R2 = 0.797), the correlation between the freshness index (β:α) and UV254 removal was also mild (R2 = 0.787). The removal efficiencies of bulk NOM were higher than for FNOM in the rapid sand filtration (RSF) stage, regardless of the location of the plants, suggesting that the RSF process is more efficient in removing non-fluorescent NOM than FNOM fractions. This study demonstrated the capability of optical methods in characterizing the fate, occurrence and removal of NOM in surface waters.
13250. 题目: Variability of Particulate Bioavailable Phosphorus, Particulate Organic Carbon and Nitrogen in Agricultural and Urban rivers
期刊: Journal of Environmental Chemical Engineering
作者: James Mbabazi, Takanobu Inoue, Kuriko Yokota, Makoto Saga
摘要: Suspended sediments (SS) play a key role as carriers of particulate nutrients which support primary productivity in aquatic systems. In this study, we assessed the relationship between particulate bioavailable phosphorus (PBAP), particulate organic carbon (POC) and particulate organic nitrogen (PON) in rivers flowing through contrasting land use at high and low flow. PBAP as a percentage of particulate phosphorus varied from 5 to 54%, and at low flow, there was a significant increase in PBAP fraction in the urban river as compared to the agricultural river. In addition, elevated POC and PON concentrations in both rivers were associated with low flow. POC and PON concentrations in both rivers declined at high flow presumably due to the mixing effects of water from different sources in the watershed which could have altered the particulate organic matter composition. A significant correlation existed between POC and SS in both rivers, and POC to PON ratios of SS from the rivers point to the change in the nature of particulate organic matter at varying flow conditions. PBAP exhibited a positive relationship with POC and PON concentration in both rivers possibly an indication that particulate organic matter contributes to bioavailable phosphorus in the rivers.
13251. 题目: The Subtropical Ocean's Biological Carbon Pump Determined from O 2 and DIC/DI 13 C Tracers
期刊: Geophysical Research Letters
作者: Bo Yang, Steven R. Emerson, Paul D. Quay
摘要: The Ocean's biological organic carbon pump regulates the pCO2 of the atmosphere and helps maintain the oxygen distributions in the ocean. Global models of this flux are poorly verified with observations. We used upper‐ocean budgets of O2 and the 13C/12C of dissolved inorganic carbon (DIC) to estimate the biological pump in the subtropical gyres. These two tracers yield, within errors, similar result (~ 2.0 mol C m2 yr‐1) at three Northern Hemisphere subtropical locations. Values for three Southern Hemisphere subtropical regions are lower and more variable determined by the O2 mass balance than by the DI13C method (‐0.5 to 0.8 and 0.9 to 1.3 mol C m2 yr‐1, respectively). Both methods suggest that the subtropical ocean is, on the whole, autotropic. The gas exchange residence times of O2 and DIC result in different spatial and temporal averaging creating complementary tracers for biological pump model verification.
13252. 题目: Shining light on the storm: in-stream optics reveal hysteresis of dissolved organic matter character
作者: M. C. H. Vaughan, W. B. Bowden, J. B. Shanley, A. Vermilyea, A. W. Schroth
摘要: The quantity and character of dissolved organic matter (DOM) can change rapidly during storm events, affecting key biogeochemical processes, carbon bioavailability, metal pollutant transport, and disinfection byproduct formation during drinking water treatment. We used in situ ultraviolet–visible spectrophotometers to concurrently measure dissolved organic carbon (DOC) concentration and spectral slope ratio, a proxy for DOM molecular weight. Measurements were made at 15-minute intervals over three years in three streams draining primarily agricultural, urban, and forested watersheds. We describe storm event dynamics by calculating hysteresis indices for DOC concentration and spectral slope ratio for 220 storms and present a novel analytical framework that can be used to interpret these metrics together. DOC concentration and spectral slope ratio differed significantly among sites, and individual storm DOM dynamics were remarkably variable at each site and among the three sites. Distinct patterns emerged for storm DOM dynamics depending on land use/land cover (LULC) of each watershed. In agricultural and forested streams, DOC concentration increased after the time of peak discharge, and spectral slope ratio dynamics indicate that this delayed flux was of relatively higher molecular weight material compared to the beginning of each storm. In contrast, DOM character during storms at the urban stream generally shifted to lower molecular weight while DOC concentration increased on the falling limb, indicating either the introduction of lower molecular weight DOM, the exhaustion of a higher molecular weight DOM sources, or a combination of these factors. We show that the combination of high-frequency DOM character and quantity metrics have the potential to provide new insight into short-timescale DOM dynamics and can reveal previously unknown effects of LULC on the chemical nature, source, and timing of DOM export during storms.
13253. 题目: Initial soil formation in an agriculturally reclaimed open-cast mining area - the role of management and loess parent material
期刊: Soil and Tillage Research
作者: Evelin Pihlap, Miljenka Vuko, Maik Lucas, Markus Steffens, Michael Schloter, Doris Vetterlein, Manuel Endenich, Ingrid Kögel-Knabner
摘要: After reclamation of open-cast mining pits, soil formation starts from the deposited calcareous loess characterised by its basic physical and chemical properties whereas soil biology and structure need to develop to achieve a fully functional soil. In this study we used a chronosequence approach to elucidate soil formation on agriculturally reclaimed loess soils in an open-cast lignite mining area in Garzweiler (Germany). We selected six fields aged 0, 1, 3, 6, 12, and 24 years after the first seeding in order to observe the initial stage of development of soil properties and assess the role of management with conventional crop rotation in soil structure formation and soil organic carbon (SOC) accumulation. Loess parent material had a strong impact on aggregation, as CaCO3 acted as a strong cementing agent. Alfalfa cultivation in the pioneering phase was of high importance in the development of microbial biomass, as it protects microbes from N limitation. Soil macroporosity and pore connectivity increased only after compost application and ploughing during agricultural crop rotation. Soil organic matter (SOM) build-up was strongly dependent on the addition of compost, as crop residues from conventional crop rotation are not sufficient to maintain high SOC contents.
13254. 题目: DBP alteration from NOM and model compounds after UV/persulfate treatment with post chlorination
期刊: Water Research
作者: Zhechao Hua, Xiujuan Kong, Shaodong Hou, Shiqian Zou, Xibing Xu, Huang Huang, Jingyun Fang
摘要: The UV/persulfate process is an effective advanced oxidation process (AOP) for the abatement of a variety of micropollutants via producing sulfate radicals (SO4•-). However, when this technology is used to reduce target pollutants, the precursors of disinfection byproducts (DBPs), such as natural organic matter (NOM) and organic nitrogen compounds, can be altered. This study systematically investigated the DBP formation from NOM and five model compounds after UV/H2O2 and UV/persulfate treatments followed with 24 h chlorination. Compared to chlorination alone, the yields of trichloromethane (TCM) and dichloroacetonitrile (DCAN) from NOM decreased by 50% and 54%, respectively, after UV/persulfate treatment followed with chlorination, whereas those of chloral hydrate (CH), 1,1,1-trichloropropanone (1,1,1-TCP) and trichloronitromethane (TCNM) increased by 217%, 136%, and 153%, respectively. The effect of UV/H2O2 treatment on DBP formation shared a similar trend to that of UV/persulfate treatment, but the DBP formation was higher from the former. As the UV/persulfate treatment time prolonged or the persulfate dosage increased, the formation of TCM and DCAN continuously decreased, while that of CH, 1,1,1-TCP and TCNM presented an increasing and then decreasing pattern. SO4•- activated benzoic acid (BA) to form phenolic compounds that enhanced the formation of TCM and CH, while it deactivated resorcinol to decrease the formation of TCM. SO4•- reacted with aliphatic amines such as methylamine (MA) and dimethylamine (DMA) to form nitro groups, which significantly increased the formation of TCNM in post chlorination, and the rate was determined to be higher than that of HO•. This study illuminated the diverse impacts of the structures of the precursors on DBP formation after UV/persulfate treatment, and DBP alteration depended on the reactivity between SO4•- and specific precursor.
13255. 题目: Modelling partition coefficients of radium in soils
期刊: Applied Geochemistry
作者: L. Urso, V. Hormann, A. Diener, M. Achatz
摘要: A thermodynamic sorption model is used to calculate partition coefficients (Kd) of radium in soils. It accounts for the dominant chemical interactions of radium with soil by assuming that non-available thermodynamic constants for radium can be replaced by those of barium. The retention processes considered include sorption on clay surfaces, on organic matter and on hydrous ferric oxide as well as the co-precipitation of radium with barium. The modelled Kd values are compared to experimental Kd values available in the relevant literature. The results show that the experimental Kd values are within a factor of 2–3. The model is also applied to two representative German soil types. The calculated Kd values agree with the finding that Kd values for radium are generally low. The conclusion is that radium retention can be modelled reasonably well, but that it is necessary to account for specific properties such as the ability of radium to co-precipitate with barium and competition from other alkaline earth metals for surface sites.
13256. 题目: Effects of exotic and native mangrove forests plantation on soil organic carbon, nitrogen, and phosphorus contents and pools in Leizhou, China
作者: Jianxiang Feng, Xiaowei Cui, Jian Zhou, Liming Wang, Xiaoshan Zhu, Guanghui Lin
摘要: The fast growing exotic Sonneratia apetala had been widely used to restore the mangroves in China. Planted mangroves play important roles in enhancing carbon sequestration and nutrient storage. The contents and pools of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) of simultaneously planted exotic S. apetala and native mixing mangrove (Avicennia marina, accompanied by Aegiceras corniculatum and Kandelia obovata) were quantified to evaluate the ecological restoration effects. Comparing with unvegetated mudflat, the colonization of mangrove can increase the SOC content within 60 cm and total nitrogen contents within 40 cm. No significant differences existed between S. apetala and native mangrove communities for the SOC, TN and TP contents. The restoration of mangrove forests enhanced the soil carbon stock relative to mudflat but significant differences existed only between native mangrove and mudflat. The TN and TP pools were not impacted by the plantation of mangroves. Therefore, plantation of S. apetala less than two decades did not show any advantages on the stocks of organic carbon and nutrients. The mixing native mangrove community should be recommended to enlarge the area of mangrove and enhance the carbon stock capability in the future.
13257. 题目: Effects of season and interval of prescribed burns on pyrogenic carbon in ponderosa pine stands in the southern Blue Mountains, Oregon, USA
作者: Lauren M. Matosziuk, Yvan Alleau, Becky K. Kerns, John Bailey, Mark G. Johnson, Jeff A. Hatten
摘要: In ponderosa pine (Pinus ponderosa) forests of the western United States, prescribed burns are used to reduce fuel loads and restore historical fire regimes. The season of and interval between burns can have complex consequences for the ecosystem, including the production of pyrogenic carbon (PyC). PyC plays a crucial role in soil carbon cycling, displaying turnover times that are orders of magnitude longer than unburned organic matter. This work investigated how the season of and interval between prescribed burns affects soil organic matter, including the formation and retention of PyC, in a ponderosa pine forest of eastern Oregon. In 1997 a prescribed burn study was implemented in Malheur National Forest to examine the ecological effects of burning at 5 and 15-year intervals in either the spring or fall. In October 2015, both O-horizon and mineral soil (0–15 cm) samples were collected and analyzed for PyC concentration, content, and structure using the benzene polycarboxylic acid (BPCA) method. O-horizon depth, carbon and nitrogen concentration and content, pH, and bulk density were also measured. Plots burned in the spring and fall had lower C and N stocks in the O-horizon compared to the unburned controls due to a reduction in O-horizon depth; however, we did not observe any differences in O-horizon concentration of C or N. Moreover, the concentrations and stocks of C and N in the mineral soil of plots burned in the spring or fall were the same as or only very slightly different from the unburned controls, suggesting that the prescribed burns on these sites have not adversely affected SOM quantity in the surface mineral soil carbon pools over the course of this 18-year experiment. Compared to unburned controls, we estimate that fall burns increased the mean PyC concentration of the mineral soil by 8.42 g BPCA/kg C. We did not detect a difference in mean PyC concentration of the mineral soil between the spring burns and the unburned controls; however, the spring burn plots did contain a number of isolated pockets with very high concentrations of PyC, suggesting a patchier burn pattern for these plots. In general, there was no detectable difference in any of the response variables when comparing the various prescribed burn treatments to one another. Reestablishing fire in these forests resulted in minor effects on the PyC concentration and pH, which may have beneficial impacts on soil carbon and available nutrients, while having few effects on other soil characteristics. This suggests that the application of low severity prescribed fires should result in little detrimental change to soils of ponderosa pine forests of the Southern Blue Mountains, while achieving management objectives such as reduction of surface fuels.
13258. 题目: Fate of antibiotics and antibiotic-resistance genes in a full-scale restaurant food waste treatment plant: Implications of the roles beyond heavy metals and mobile genetic elements
期刊: Journal of Environmental Sciences
作者: Pinjing He, Zhuofeng Yu, Liming Shao, Yizhou Zhou, Fan Lü
摘要: Is our food safe and free of the crisis of antibiotics and antibiotic resistance (AR) And will the derived food waste (FW) impose AR risk to the environment after biological treatment This study used restaurant FW leachates flowing through a 200 tons-waste/day biological treatment plant as a window to investigate the fate of antibiotics and antibiotic-resistance genes (ARGs) during the acceptance and treatment of FW. Sulfonamides (sulfamethazine, sulfamethoxazole) and quinolones (ciprofloxacin, enrofloxacin, ofloxacin) were detected during FW treatment, while tetracyclines, macrolides and chloramphenicols were not observable. ARGs encoding resistance to sulfonamides, tetracyclines and macrolides emerged in FW leachates. Material flow analysis illustrated that the total amount of antibiotics (except sulfamethazine) and ARGs were constant during FW treatment processes. Both the concentration and total amount of most antibiotics and ARGs fluctuated during treatment, physical processes (screening, centrifugation, solid–liquid and oil–water separation) did not decrease antibiotic or ARGs concentrations or total levels permanently; the affiliated wastewater treatment plant appeared to remove sulfonamides and most ARGs concentrations and total amount. Heavy metals Ni, Co and Cu were important for disseminating antibiotics concentrations and MGEs for distributing ARGs concentrations. Humic substances (fulvic acids, hydrophilic fractions), C-associated and N-associated contents were essential for the distribution of the total amounts of antibiotics and ARGs. Overall, this study implied that human food might not be free of antibiotics and ARGs, and FW was an underestimated AR pool with various determinants. Nonetheless, derived hazards of FW could be mitigated through biological treatment with well-planned daily operations.
13259. 题目: Soil physical properties of a Luvisol developed on loess after 15 years of amendment with compost
期刊: Soil and Tillage Research
作者: Remigio Paradelo, Marie Eden, Ingrid Martínez, Thomas Keller, Sabine Houot
摘要: Recycling composted organic residues in agriculture can reduce the need for mineral fertilizers and improve the physicochemical and biological properties of cultivated soils. However, more studies dealing with soil physical properties after compost amendment are still needed. The objective of this study was to investigate the impact of long-term compost amendment on soil physical properties in a silt loam Luvisol under a maize-wheat rotation in the Paris Basin. Since 1998, three composts and one manure were applied every second year after wheat harvest, at a rate of ca. 4 Mg C ha−1. Bulk density, organic carbon concentration on a mass basis, water holding capacity, gas transport properties and Atterberg limits were measured on topsoil samples taken 15 years after the beginning of the experiment. Soil moisture was monitored in the field down to a depth of 160 cm during two years with different climatic conditions: a year with a dry summer (2010) and a year with a wet summer (2012). Compost and manure amendments reduced bulk density and increased organic carbon concentrations, which improved apparent air permeability and gas diffusivity, but only one of the amendments (a green waste-sewage sludge compost) increased water-holding capacity. The amendments also increased the water contents at the Atterberg limits and overall produced better soil conditions for tillage and other agricultural operations, in particular in wet years. However, field moisture measurements showed that in general, soil water contents were not higher in the amended soils than in the control at any of the periods considered.
13260. 题目: Arsenic volatilization in flooded paddy soil by the addition of Fe-Mn-modified biochar composites
期刊: Science of The Total Environment
作者: Lina Lin, Zhengguo Song, Xuewei Liu, Zulqarnain Haider Khan, Weiwen Qiu
摘要: We investigated the potential role of Fe-Mn-modified biochar composites (FMBCs) in the volatilization of toxic arsenic (As) in flooded paddy soil, by considering As fractionation, enzyme activities, and bacterial abundance. The results indicated that the addition of FMBCs reduced As volatilization from polluted soil, and this effect was more pronounced at higher dosages. Two types of FMBCs (i.e., FMBC1 and FMBC2) were analyzed, and FMBC2 exhibited a superior performance to FMBC1. Maximum volatilization was achieved in the fourth week and was followed by stabilization. In addition, the majority of As in the soil corresponded to crystalline and residual phases. Furthermore, the addition of FMBCs had little influence on the activities of various enzymes, although FMBC1 significantly affected catalase and peroxidase activities (P < 0.05). Moreover, FMBC application changed the relative abundances of different bacteria, where the abundances of Firmicutes were reduced, but a 2 g dose of FMBCs in highly polluted soil increased the bacterial abundance. In addition, the As volatilization, As fractionation, and enzyme activities displayed some correlation, in that As volatilization was negatively correlated to the presence of residual As phases but positively correlated to amorphous and poorly crystalline hydrous oxides of Fe and Al. As such, As fractionation and an improvement in soil properties are important mechanisms for reducing As volatilization.