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24781. 题目: Effects of biochar incorporation and fertilizations on nitrogen and phosphorus losses through surface and subsurface flows in a sloping farmland of Entisol Nitrogen (N) and phosphorus (P) loss in runoffs has been a serious problem in China due to the amount of chemical fertilizer currently applied to farmland. Biochar has been used as a soil amendment for increasing nutrient retention, water holding capacity, and crop yield. However, little is known about the influence of biochar on the runoff erosion from both surface flow and subsurface flow, especially in sloping regions. Experimental runoff plots were, therefore, set up on Entisols in a sloping farmland, involving four treatments: control (CT), conventional NPK fertilization (CF, based on local practices), optimum NPK fertilization (OF, based on the recommendation from local agriculture committee), and biochar combined with 85% of optimum NPK fertilizer (BF). The effects of the four treatments on the runoff fluxes, sediment yields and the runoff coefficients, as well as the N (ammonium (NH4+), nitrate (NO3−) and total N (TN)) and P (phosphate (PO43-), total P (TP), dissolved TP (DTP), particulate P (PP)) losses via both surface runoff (i.e., surface flow, 0–20 cm, ploughed layer) and subsurface runoff (i.e., subsurface flow, 20–60 cm, non-ploughed layer) were all monitored and evaluated from April 2018 to September 2019. Results show that, in this sloping farmland, subsurface flow was the main process of runoff and dominated N transport, but surface flow dominated P transport. The three fertilization treatments reduced the runoff erosion by surface flow, while increasing it from subsurface flow (p < 0.05). Compared with two NPK fertilizations, BF treatment significantly increased the total sediment yield, subsurface runoff flux and subsurface runoff coefficient. Among all three fertilization treatments, the differences of grain yields are found not significant (except for the 4th crop). In surface flow, biochar addition increased the loss flux of NH4+ and P fractions, but reduced the loss flux of NO3− with the comparison of the CF and OF treatments. In subsurface flow, biochar addition didn't significantly changed the runoff of N fractions, but increased P runoffs, especially for TP and PP runoffs (p < 0.05). Overall, the risk of N and P loss, and runoff erosion through subsurface flow in biochar incorporated Entisols sloping farmland needs be highlighted. | |||||
24782. 题目: Increasing soil organic carbon with maize in cotton-based cropping systems: Mechanisms and potential In a rotation, the use of crop species with large root biomass is thought to increase soil organic carbon (SOC) storage deeper in the soil profile, yet the processes and mechanisms that control SOC dynamics at depth are poorly understood. Using a cotton-based field trial, we examined how maize may impact SOC dynamics up to 1 m depth in three systems that differed in tillage and wheat rotation by examining the changes in δ13C signature of SOC and soil C fractions associated with maize during a two-year period. The inclusion of maize increased the whole-profile SOC stock, particularly in the subsoil under minimum tillage and wheat rotation. The increase was associated with the stable C fraction, and could not be attributed solely to the C contribution from maize root biomass alone. We propose that C movement in the form of dissolved organic C (DOC) may have contributed to the observed increase in SOC stock. The strong temporal changes and the possible mechanisms behind the increase suggest that the introduction of maize into cotton-based cropping systems may not yield a consistent benefit. This study highlights the role of DOC in subsoil C stock and the importance of understanding whole-profile SOC dynamics in evaluating the potential of management practice in increasing SOC stock. | |||||
24783. 题目: Impact of Na-selenite fertilization on the microbial biomass and enzymes of a soil under corn (Zea mays L.) cultivation We tested the over time effect of different selenium doses [50 (D50) and 100 (D100) g ha−1 of Se as Na2SeO3] on a soil under corn (Zea mays L.) cultivation. The soil was sampled 18 (t1), 48 (t2) and 59 (t3) days after the addition of Se and analysed for total Se, organic carbon and nitrogen, water-extractable organic carbon, available P, microbial biomass-C (Cmic) contents, the cumulative basal respiration (ΣCO2-C) and some enzymatic activities. Our findings showed Se fertilization increased the total soil Se content, although the differences between the treated and the untreated soils disappeared over time. Se fertilization had a negligible effect on the selected soil chemical and biochemical properties, with the exception of the ΣCO2-C, and fluorescein diacetate hydrolysis and dehydrogenase activity. Indeed, these parameters showed lower values at t3 in the treated than in the untreated soils without significant decrease of the Cmic suggesting a less energy demanded by the soil microorganisms for their own maintenance. This finding suggested a better adaptation of the microbial community to the modified conditions in the treated soils, where Se fertilization might have caused a shift in soil microbial community structure and/or promoted the survival of selected microorganisms. Overall, the obtained data highlighted that Se fertilization with Na-selenite, at the rate of 50 and 100 g ha−1, had no negative impact on soil chemical and biochemical parameters, at least on a short term. | |||||
24784. 题目: The nonconservative distribution pattern of organic matter in the Rajang, a tropical river with peatland in its estuary | |||||
24785. 题目: Clarifying the response of soil organic carbon storage to increasing temperature through minimizing the precipitation effect Considerable attention has been paid to the variation of soil organic carbon (SOC) storage along a temperature gradient. However, the results varied across studies. This inconsistence could be associated with the interference of the precipitation effect. To minimize the interference, this study collected soil samples over broad geographical scale along the 400 mm isohyet in China. Our results showed that SOC storage responded negatively to increasing temperature with a response coefficient of 0.24. Temperature explained more than half of the variability in SOC stock, which was much greater than the combined effects of water availability, soil properties, vegetation type and soil type. The negative relationship between SOC stock and temperature was not affected by vegetation type and soil type, suggesting that this correlation might be a general pattern. | |||||
24786. 题目: A comparison and evaluation of the effects of biochar on the anaerobic digestion of excess and anaerobic sludge The mechanisms and enhancing effects of different biochar loadings on the digesters receiving low and high excess (or anaerobic) sludge loadings were thoroughly examined in the present study. This was done to explore an efficient method for converting excess sludge to anaerobic sludge. Biochar had an obvious effect on the anaerobic digestion of excess sludge but not on the anaerobic sludge. When the amount of biochar added was equivalent to 100% of the sludge TS, the cumulative methane yields of anaerobic digestion inoculated with small and large amounts of excess sludge were respectively 30.2 and 1.7 times that of those without biochar. The number of methanogens in the digesters that received small and large inoculations of excess sludge with 100% biochar, were respectively 105.4% and 20.6% higher than those without biochar. The biochar enhanced the systems performance because it selectively enriched the Trichococcus and Methanomicrobiales tightly attach to it. This enhanced the synergy and overall activity of the system by promoting biofilm development. Ultimately, the integration of 100% biochar and excess sludge can be used as a substitute for anaerobic sludge as an inoculum by giving similar overall performance. | |||||
24787. 题目: Potential of Chlorella vulgaris and Nannochloropsis salina for nutrient and organic matter removal from municipal wastewater reverse osmosis concentrate | |||||
24788. 题目: Soil and microbial biomass stoichiometry regulate soil organic carbon and nitrogen mineralization in rice-wheat rotation subjected to long-term fertilization | |||||
24789. 题目: Biofilm formation and its influences on the properties of microplastics as affected by exposure time and depth in the seawater The effects of microbial colonization and biofilm formation on microplastics in the marine and coastal environments have aroused global concern recently. However, the simultaneous influences of exposure time and depth on biofilm formation, and subsequently on the properties variations of microplastics is less studied. In this study, polyethylene (PE) film was exposed at three depths (2 m, 6 m, and 12 m) for three time periods (30 days, 75 days, and 135 days) in the coastal seawater of Yellow Sea, China. The results show that the total amount of biofilms markedly increased with exposure time, but decreased with water depth. Typical morphologies and compositions of biofilms such as coccus-, rod-, disc-shaped bacteria and filaments, as well as a dense layer of extracellular polymeric substances were observed on the surfaces of the PE microplastics. Biofilm formation could decrease the hydrophobicity of PE microplastics, and increase the abundances of hydrophilic C−O and CO groups on the surface of PE. Alphaproteobacteria, Gammaproteobacteria and Bacteroidia were identified as the core microbiome of the PE associated biofilms, while the dominant bacteria families vary from the early to the late phases of the biofilm formation. Our results indicate that microplastics associated biofilms could affect the environmental processes and fates of microplastics in the marine and coastal environment. | |||||
24790. 题目: Impacts of carrier properties, environmental conditions and extracellular polymeric substances on biofilm formation of sieved fine particles from activated sludge To investigate the effect of properties of carriers, environmental conditions and extracellular polymeric substances (EPS) on the initial adhesion of biofilm formation in biofilm-based reactors, a quartz crystal microbalance with dissipation (QCM-D) was applied to monitor the deposition rates and viscoelastic properties of sieved sludge particles on model biocarriers. The results suggested that surface charge, hydrophobicity and surface coating of five representative carriers influenced deposition rates and viscoelastic properties of biofilm, whose variation with NaCl concentrations was controlled by not only the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction but also non-DLVO forces. On hydrophobic surface, the addition of cationic substances enhanced the deposition rates and the compaction of deposited layer due to strong hydrophobizing effect. For examples, 10 mM Ca2+, 10 mM Mg2+ and 10 mg/L poly-l-lysine enhanced the deposition rates to nearly 3, 2 and 4 times, as well as reduced the softness of deposited layer to almost 35%, 60% and 35%. Conversely, 10 mg/L negatively charged alginate might cause water retainment and steric shielding, thereby reducing the deposition rates to 40% and increasing the softness of deposited film to 120%. The presence of EPS sub-fractions can modify surface properties of sludge particles, to distinct degrees, contributing to biofilm formation. Notably, compared to tightly bound EPS (TB-EPS), loosely bound EPS (LB-EPS) was more conducive to microbial attachment, but the presence of LB-EPS promoted the formation of a soft layer on a hydrophobic surface. Overall, these results provide insights into intrinsic mechanisms of the variation of deposition rates and viscoelastic properties responding to critical factors, which are meaningful to predict and regulate the initial adhesion process in biofilm-based reactors. | |||||
24791. 题目: Biochar addition reinforces microbial interspecies cooperation in methanation of sugar beet waste (pulp) | |||||
24792. 题目: Natural organic matter-enhanced transportation of iodine in groundwater in the Datong Basin: Impact of irrigation activities Local residents in the Datong Basin of northern China are exposed to groundwater with elevated iodine concentrations. Natural organic matter (NOM) has been linked to the heterogeneous distribution of elevated iodine in groundwater used for irrigation purposes, but little is known about the effects of hydrologic fluctuations and NOM characteristics on the transport and enrichment of iodine in the groundwater. Cl/Br molar ratios in Datong Basin groundwater range widely from 133 to 2099. A rapid increase in Cl/Br molar ratio with increasing Cl content indicates hydrologic fluctuations from the upper groundwater to the deeper aquifer due to large-scale irrigation activities in the Basin. A two end-member model of groundwater δ2H and δ18O values suggests the contribution of upper water recharging groundwater ranges from 20.7 to 49.5%. This vertical recharge process predominantly controls iodine enrichment and distribution in the groundwater. Additionally, the correlation between DOC concentration and δ18O signatures indicates considerable fresh organic matter is imported into the aquifer during the vertical recharge process. Iodine mobilization is likely promoted by young carbon transported to the deeper aquifer in the organo‑iodine form. Excitation-emission matrix (EEM) results indicate humic-like substances dominate NOM in the groundwater. Evidence from a PARAFAC model suggests organic matter in groundwater samples is associated with microbially-mediated degradation processes in an anaerobic environment. The drawdown migration of organic matter from the upper soil/sediments or surface could provide an extra energy source that promotes microbial activity. Buried sedimentary iodine coupled with anaerobic microbial respiration of subsurface organic carbon within the aquifer could lead to the release of iodine into the groundwater. These findings pave the way for a more comprehensive assessment of the susceptibility of drinking water aquifers, thereby supporting the management of groundwater resources. | |||||
24793. 题目: Combined application of biochar and N increased temperature sensitivity of soil respiration but still decreased the soil CO2 emissions in moso bamboo plantations Biochar addition to soil is increasing worldwide, the effect of combined application of biochar and nitrogen (N) fertilizer on soil respiration is still unknown. Understanding of the interactive effects of biochar and N fertilizer addition on temperature sensitivity of soil respiration and temporal dynamics of soil CO2 emissions in forest ecosystems remains limited. We conducted a full factorial experiment with biochar (B0, B1 and B2 with 0, 5 and 20 t·ha−1, respectively) and N fertilizer addition (N0 and N1 with 0 and 50 kg·ha−1 NH4NO3, respectively) as factors, to study their effects on soil respiration rate, temperature sensitivity (Q10), soil available nutrients, and their relations in moso bamboo plantations in subtropical China from April 2014 to April 2016. We found that, irrespective of biochar addition rate, N fertilization increased Q10 on the one hand, and irrespective of N fertilization rate, lower application rate of biochar resulted in a higher Q10, on the other hand. In spite of increased Q10, combined application of biochar and N decreased soil respiration rate in both growing season and non-growing season, as well as the annual cumulative soil CO2 emissions. Annual cumulative soil CO2 emissions were found to be significantly positively correlated with soil total nitrogen (STN) (p = 0.028) in 0–10 cm soil layer, and with soil ammonium (NH4+) (p = 0.000) and soil microbial biomass carbon (MBC) (p = 0.000) in both 0–10 cm and 10–20 cm soil layer. The present study suggests that the combined application of biochar and N fertilizer can be widely used in subtropical forest ecosystems where soil N is limited, because it increases soil fertility and, at the same time, decreases soil CO2 emissions. | |||||
24794. 题目: Molecular transformation of dissolved organic matter in process water from oil and gas operation during UV/H2O2, UV/chlorine, and UV/persulfate processes This paper reported the impact of UV/H2O2, UV/chlorine, and UV/persulfate advanced oxidation processes on the molecular transformations of dissolved organic matter (DOM), removal of naphthenic acids (NAs) and acute toxicity in oil sands process water (OSPW). The UV/persulfate process exhibited the highest removal (81.2% with 2 mM dose) towards classical NAs and highest reduction in acute toxicity to Vibrio fischeri among the three processes. The fraction of DOM such as CHOS class species decreased along with the increase of the oxidant doses in all processes. The increase in O/C ratio and lack of change in the H/C and double bond equivalence indicated that H-abstraction followed by the OH-addition was the main reaction pathway for all processes. This observation aligned with previous studies using model compounds and proved that OSPW DOM reacted similarly to model compounds. Sulfur containing organic matters were the most liable compounds in OSPW NOM, while UV/chlorine was the most effective process to oxidize nitrogen containing organic matters. Overall results revealed that the UV/persulfate process could be used as a promising technique for the removal of OSPW NA and reduction of acute toxicity towards Vibrio fischeri. In addition, this DOM characterization approach could be utilized to investigate the transformation of complicated OSPW DOM and to identify the byproducts generated during different water treatment processes. | |||||
24795. 题目: Arsenic behavior during gallic acid-induced redox transformation of jarosite under acidic conditions Jarosite is an important scavenger for arsenic (As) due to its strong adsorption capacity and ability to co-precipitate metal(loid)s in acid mine drainage (AMD) environments. When subjected to natural organic matter (NOM), metastable jarosite may undergo dissolution and transformation, affecting the mobility behavior of As. Therefore, the present study systematically explored the dissolution and transformation of jarosite, and the consequent redistribution of coprecipitated As(V) under anoxic condition in the presence of a common phenolic acid–gallic acid (GA). The results suggested that As(V) incorporating into the jarosite structure stabilized the mineral and inhibited the dissolution process. Jarosite persisted as the dominant mineral phase at pH 2.5 up to 60 d, though a large amount of structural Fe(III) was reduced by GA. However, at pH 5.5, jarosite mainly transformed to ferrohexahydrite (FeSO4·6H2O) with GA addition, while the principal end-product was goethite in GA-free system. The dissolution process enhanced As(V) mobilization into aqueous and surface-complexed phase at pH 2.5, while co-precipitated fraction of As(V) remained dominant under pH 5.5 condition. Result of XPS indicated that no reduction of As(V) occurred during the interaction between GA and As(V)-bearing jarosite, which would limit the toxicity to the environment. The reductive process involved that GA promoted the dissolution of jarosite via the synergistic effect of ligand and reduction, following by GA and release As(V) competing for active sites on mineral surface. The findings demonstrated that phenolic groups in NOM can exert great influence on the stability of jarosite and partitioning behavior of As(V). | |||||
24796. 题目: Heterotrophic diazotrophs in a eutrophic temperate bay (Jiaozhou Bay) broadens the domain of N2 fixation in China's coastal waters N2 fixation in coastal waters represents an overlooked process in the global marine nitrogen cycle, yet the mechanisms and controls are still poorly understood. This study first conducted simultaneous measurements of N2 fixation rates, primary production, chlorophyll a (Chl a) concentration, organic carbon concentration, and the composition of nitrogen-fixing genes (nifH) in a eutrophic temperate bay (Jiaozhou Bay, the western Yellow Sea) from 2015 to 2017. The activity of N2 fixation (not detected–1.53 nmol N L −1 h −1) were observed at most sampling stations, suggesting that the N-replete conditions in Jiaozhou Bay did not prevent N2 fixation. The major N2 fixers in JB were heterotrophic, while N2 fixation were mainly contributed by > 10 μm fraction, indicating the possible active N2 fixation of heterotrophic diazotrophs on large particles or planktonic aggregates. Positive correlations between N2 fixation and organic carbon concentration were observed in spring. Further estimates of the level of phytoplankton-derived organic carbon and its potential relationship with N2 fixation suggest that phytoplankton processes may stimulate N2 fixation in Jiaozhou Bay by increasing the bioavailability of organic carbon or/and providing suitable environmental conditions for N2 fixation. Our results first infer the co-regulation of physical factors and biological processes on N2 fixation. As Jiaozhou Bay has been subject to anthropogenic pollution of inorganic nutrients, our results provide insights into the dominant controls on N2 fixation and relevant biogeochemical processes in coastal waters under anthropogenic disturbance. | |||||
24797. 题目: Biochar-mediated Fenton-like reaction for the degradation of sulfamethazine: Role of environmentally persistent free radicals Swine manure biochar (SBC) pyrolyzed at 300 °C, 600 °C and 900 °C were utilized to degrade sulfamethazine (SMT) in heterogeneous Fenton-like systems which achieved excellent degradation efficiency (over 85% in 30 min). Experiments results demonstrated that SBC possessed the poor SMT adsorption capacity but high catalytic performance. Electron Paramagnetic Resonance (EPR) and X-ray photoelectron spectroscopy (XPS) analysis revealed that there were oxygen-centered environmentally persistent free radicals (EPFRs) and carbon-centered EPFRs with an adjacent oxygen atom in SBC. The oxygen-centered EPFRs played a major role in the catalytic process which tended to convert to carbon-centered EPFRs after the reaction. Besides, the electron transfer pathways were the most likely catalytic mechanism of SBC and the contribution of OH was dominant through Electron capture experiments and Linear sweep voltammetry (LSV) measurements. The acidic or alkaline condition can promote the catalytic ability of SBC. The presence of dissolved salts (NaCl) inhibited the catalytic process but the inhibition was slightly weakened at high concentration of NaCl, which showed the high tolerance of Cl− in Fenton/Fenton-like systems. Moreover, real wastewater application suggested that SBC600/H2O2 system possessed excellent catalytic efficiency and good adaptability. This research provides a novel swine manure reuse process with high practicability and presents a more explicit perspective about the reaction mechanisms of EPFRs in biochar. | |||||
24798. 题目: Spatiotemporal variations of biogenic elements and sources of sedimentary organic matter in the largest oyster mariculture bay (Maowei Sea), Southwest China China is the largest mariculture producer in the world, but detailed information on the spatiotemporal variations of biogenic elements and sources of sedimentary organic matter (SOM) via mariculture is limited. The primary objective of this study was to assess the influence of mariculture on the origin of SOM in relation with biogenic elements and geochemical paramaters due to the importance of SOM as a potential source of nutrients and energy in coastal marine environments. Surface sediments from the Maowei Sea were collected in August (summer) and December (winter), 2016 for grain size, total organic carbon (TOC), total nitrogen (TN), organic phosphorus (OP), biogenic silica (BSi), δ13C and δ15N analyses. Significant correlation (p < 0.01) was observed between TOC and TN in summer and winter respectively, indicating that they have common source in both seasons. The spatiotemporal distributions of TOC, TN, OP and BSi were influenced by the sources and distribution of SOM, grain sizes and hydrodynamic conditions in the Maowei Sea. The overall ranges of δ13C (−26.86‰ to −23.01‰) and δ15N (2.54‰ to 9.82‰) and C/N ratio (5.83 to 18.67) showed that SOM is derived from mixed sources. The δ13C and δ15N-based three-end-member mixing model results revealed that >40% of the deposited SOM originates from terrestrial source during two seasons. The SOM from shellfish mariculture was seasonal, mainly deposited in the intensive mariculture areas, and its proportions were only higher than contributions from marine plankton in summer. Generally, this study indicates that shellfish biodepositions can significantly influence the cycle of carbon and other biogenic elements in the intensive mariculture areas. Nevertheless, the overall dominance of terrestrial and marine SOM suggests that the sources of SOM and factors influencing carbon cycling in the Maowei Sea do not exclusively depend on the intensity of mariculture activities. | |||||
24799. 题目: A review on approaches for hazardous organics removal from Bayer liquors Alumina is a valuable raw material for the production of adsorbents, abrasives, polishing agents, refractory materials, and aluminum. It is generally produced from bauxites through the Bayer process. Several organic compounds such as humic matters and oxalates are introduced into the Bayer liquor during the digestion process, resulting in significant hazards to precipitation of aluminum hydroxide. Therefore, it is crucial to remove these organic compounds from Bayer liquor to enhance the production of alumina. It is difficult to remove these organic compounds. Various approaches for organics removal from Bayer liquors have been developed in the past few decades, including thermal treatment, chemical precipitation, membrane technology, photocatalytic degradation, biodegradation, and wet oxidation. This paper reviews the technologies for organics removal from Bayer liquor and the relative mechanisms proposed in the literature to identify its essential parameters. Chemicals dosage, temperature, pH value, reaction time, and solution concentration are essential factors in the process. Removal efficiency, green principle, and economic viability of various methods are discussed, and potential technologies are suggested. Wet oxidation appears to be a promising method for removing organic matters in Bayer liquors. Moreover, the combination of wet oxidation and electrooxidation shows excellent potential in organics removal. Various approaches for removing organic compounds and perspectives for further investigation are proposed. | |||||
24800. 题目: Effects of Robinia pseudoacacia afforestation on aggregate size distribution and organic C dynamics in the central Loess Plateau of China: A chronosequence approach Afforestation has been proven to have enormous potential for carbon (C) sequestration; however, the dynamics of aggregate-associated organic carbon (OC) following afforestation and their contribution to changes in bulk soil OC are not well understood in regions with serious soil erosion. Therefore, we investigated the dynamics of OC associated with aggregates along a Robinia pseudoacacia (RP) afforestation chronosequence in the Loess Plateau. Soil aggregate size distribution and OC dynamics in bulk soil were analyzed 10, 18, 28, and 42 years after RP afforestation at depths of 0–20 cm and 20–40 cm. Results showed that total macroaggregates (>0.25 mm), mean weight diameter, and geometric mean diameter increased significantly with stand age, after 42 years of afforestation, increased by 433.5%, 437.2%, 302.1% in the 0–20 cm depth, respectively, while microaggregate amounts decreased by 52.9%, and the proportions of silt + clay fraction showed no obvious changes. Long-term afforestation increased OC content and stock, both in bulk soil (245.6% and 222.9% in the 0–20 cm depth, respectively) and soil aggregates. The improvement of soil structure and enrichment of OC stocks were greater at the 0–20 cm depth than the 20–40 cm depth. In addition, small macroaggregates (2–0.25 mm) contained the highest OC content and microaggregates (<0.025 mm) had the highest OC stocks regardless of soil depth and stand age. Across the afforestation chronosequence, OC content and stock in bulk soil positively correlated with large macroaggregate (>2 mm) amounts and small macroaggregate (2–0.25 mm) associated OC dynamics (P < 0.01). These results indicated that changes in bulk soil OC dynamics mainly depend on changes in the proportion of large macroaggregates and in the OC dynamics associated with small macroaggregates after RP afforestation. | |||||
