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24241. 题目: Spatial heterogeneity of organic carbon cycling in sediments of the northern Yap Trench: Implications for organic carbon burial The hadal trenches (>6000 m) are considered to be ultimate sinks of organic carbon (OC) from biosphere. However, highly spatial heterogeneity of geographic background and organic matter in different zones make significant influences on the OC cycling, and further the carbon burial. In this study, three sediment cores were drilled across the northern Yap Trench axis (9.8–9.9°N, 138.3–138.7°E). The elemental compositions, stable carbon isotopes of organic matter, mineral-specific surface area, and grain size composition were analyzed to investigate the spatial variations of organic sources, distribution, and its degradation in the northern Yap Trench. The surface sedimentary OC (SOC) contents in the northern Yap Trench increase from 0.25% at abyssal depth (4435 m) to 0.50% at hadal depth (~6674 m). Higher OC content (0.27% ± 0.08%) and sedimentation rate (5.8 cm kyr−1) occur in the station on the gradual oceanward slope (~4.2°) compared to those on the steep landward slope (~10°) (0.17% ± 0.13%, 0.52–1.8 cm kyr−1), suggesting enhanced accumulation of OC on the gradual slope. The allochthonous OC (i.e. marine phytoplankton-derived (55% ± 7%) and terrestrial (16% ± 8%)) dominates the SOC pool on the oceanward slope, whereas autochthonous microbe reworked OC contributes more than 50% in the steep landward slope, based on the evaluation of a three-end-member mixing model using δ13C composition and OC/N ratios as source markers. Correspondingly, radiocarbon age of SOC in the gradual slope is ~700 years younger than that in the steep slope with similar depth, indicating that the relatively fresh allochthonous OC is selectively deposited on the gradual slope. A multi-G degradation model demonstrates that OC degradation rates in the northern Yap Trench range from 0.00015 yr−1 to 0.00068 yr−1, which can be comparable with abyssal plain (3000–6000 m) and are lower than those of neritic environments (<1000 m). Mass accumulation model calculation shows that accumulation rate of surface OC in the northern Yap trench is ~2.7 × 10−2 g C m−2 yr−1, much lower than those from other deep ocean seafloors. This study suggests an inefficient SOC preservation within the northern Yap Trench, which might be induced by high labile marine phytoplankton-derived OC inputs and active heterotrophic microbial activity, and the results have important implications for better understanding the effects of sediment dynamics on OC cycling in hadal zones. | |||||
24242. 题目: Strategies to improve the prediction of bulk soil and fraction organic carbon in Brazilian samples by using an Australian national mid-infrared spectral library At present, organic carbon (OC) levels are measured using techniques that can be very expensive and time-consuming or can generate toxic residue. Mid-infrared (MIR) spectroscopy, which is an inexpensive and safe technique, can be used for OC prediction; however, appropriate modeling is required. This study aimed to evaluate different strategies for MIR modeling calibration in order to improve the accuracy and cost-effectiveness of OC prediction in bulk soils and fractions (e.g., particulate OC, POC; humic OC, HOC; resistant OC, ROC). We used regional topsoil samples (i.e. 0–20 cm) from Brazil (BRreL) and an existing Australian national library (AUnaL) to calibrate different models, which were used to predict OC content in target samples (i.e. subset of the Brazilian sample set). In total, eight strategies were tested, including the use of different soil libraries, different chemometric approaches (i.e. common multivariate regression and local-type modeling), and spiking. The highest accuracy for OC prediction in Brazilian regional target samples for both bulk soils (RPIQ = 5.86; RMSE = 3.17 g kg−1) and fractions (RPIQ = 1.58, 5.72, and 5.21 for POC, HOC, and ROC, respectively) was obtained when the BRreL was used to calibrate a partial least square regression. When AUnaL was used alone as the calibration set, the OC prediction accuracy sharply decreased and even the local-type models Cubist and spectrum-based learning, in general, were not able to achieve high OC predictions accuracy. With this strategy, the averaged RPIQ values (among the three models) were 2.92, 0.55, 2.17, and 0.65 for bulk OC, POC, HOC, and ROC, respectively. However, when 20 Brazilian regional samples (representing 8 and 42% of the original calibration samples used for total and fraction OC, respectively) were spiked to the AUnaL, the OC predictions accuracy markedly improved for all OC pools, regardless of the modeling approach used. With this strategy, the averaged RPIQ values were 4.74, 1.35, 4.49, and 2.29 for bulk OC, POC, HOC, and ROC, respectively. In addition, high OC prediction accuracy (RPIQ = 4.49 for bulk OC; RPIQ = 1.58, 6.87, and 4.26 for POC, HOC, and ROC, respectively) was obtained when models were calibrated with the 20-spiking subset only. Our results suggest that a proper selection of a small calibration set, that could be used alone or to augment an existing library, is critical and could make feasible the OC prediction in bulk soils and fractions by MIR spectroscopy. | |||||
24243. 题目: Preparation of biochar as a coating material for biochar-coated urea Biochar was used as a coating material for slow release urea. However, influence of biochar performance on preparing biochar-coated urea (BCU) and nitrogen release characteristics is rarely reported. In this study, total of 24 biochars were prepared and characterized from six biomass residues (rice straw, chicken manure, vinasse, Phyllostachys pubescens, Arundo donax and sugarcane bagasse) at four pyrolysis temperatures (400–700 °C). Grey correlation analysis (GCA) was used to select biochar as a coating material for BCU based on biochar performance indicators. The feasibility (BCU formability) for preparing BCU and characteristics of nitrogen release in BCU based on hydrostatic dissolution test and soil column leaching experiment were evaluated. Biochar prepared at low pyrolysis temperature was not suitable as a coating material for BCU due to low specific surface area. Biochars derived from pyrolysis of Phyllostachys pubescens (BP6), vinasse (BV6) and rice straw (BR6) at 600 °C were selected as coating materials for BCU based on grey correlation analysis (GCA). The adhesion of biochar to urea surface was related to biomass type that preparing biochar. BV6 was recommended for use as coating material for BCU because the feasibility of the biochars followed the order BR6 > BV6 > BP6, and the practicality of the biochars followed the order BP6 > BV6 > BR6. The findings suggest that biochar with a high specific surface area, hydrophilic oxygen-containing functional groups and low pH is a suitable material for BCU. | |||||
24244. 题目: Roles of molecular weight-fractionated extracellular polymeric substance in transformation of Au(III) to Au nanoparticles in aqueous environments Extracellular polymeric substance (EPS) is widely distributed in natural environments and plays important roles in the biogeochemical cycling of heavy metal. Earlier works reported that EPS could reduce metal ions such as Au(III) and Ag(I) to corresponding metal nanoparticles (NPs). EPS is a complex mixture of microbiogenic polymers with wide molecular weight (MW) distribution, and the specific components of EPS responsible for Au(III) reduction and AuNPs stabilization are still not well understood. In this study, the EPS of Shewanella oneidensis MR-1 was divided into six fractions with MW of <3, 3–10, 10–30, 30–50, 50–100, and >100 kDa, respectively through the ultrafiltration method and the roles of MW-fractionated EPS in the reduction of Au(III) to AuNPs were investigated. It was found that the low MW (<3 kDa) EPS was the major reducing agent in EPS but the fraction itself could not convert high concentration (>25 mg/L) of Au(III) to stable AuNPs due to its inferior AuNPs-stabilizing capacity. The high MW (>50 kDa) EPS could act as coating reagents to increase the stability of the formed AuNPs with sizes of 20–50 nm, but had low Au(III)-reducing activity. The carboxyl-containing substances in EPS may play crucial roles in stabilizing AuNPs. This finding is important for a better understanding of the differential roles of MW-fractionated EPS in the transformation and fate of Au(III) and AuNPs, as well as other metal ions and metal NPs in natural environments. | |||||
24245. 题目: Insights into catalytic removal and separation of attached metals from natural-aged microplastics by magnetic biochar activating oxidation process Natural-aged microplastics with changed surface properties accumulate, redistribute and spread in all water fields as carriers of hazardous substances. The combined hazard of co-contamination of microplastics and hazardous substances expands the ecological risks, which urgently needs to design treatment schemes for pollutant removal from microplastics. In this paper, a facile and applicable magnetic biochar with porosity and graphitization (PGMB) was prepared for realizing the goal of metal removal from the microplastics. Heterogeneous catalysis of persulfate (PS) activated by PGMB achieved the decomposition of organics, with the decrease of more than 60% of the attached Pb on the surface of microplastics, and the adsorbed metal amount by PGMB in this system (31.29 mg/g) is much higher than that by the individual PGMB group (7.07 mg/g). Analysis demonstrated that the organic layer covered on the microplastic surface over the long-term weathering provided the key sites for metal sorption, whose decomposition and peeling were the critical steps in whole process. The prepared PGMB was responsible for activating PS to produce reactive species for decomposing the organic matter accompanied with detaching metals from microplastic surface, also would keep the role for re-adsorption of the released metals and separation from aqueous phase by magnetic force. The influences of natural environmental factors including salinity, common matrix species, and temperature on the performance of PGMB/PS system for metal removal from microplastics were discussed to illustrate the universality of the scheme in saline or organic-rich waters. The results of this study provided underlying insights for removing metals from microplastic surface, and decreasing the harm risks in the co-contamination of microplastics and hazardous substances. | |||||
24246. 题目: Singlet Oxygen Photogeneration in Coastal Seawater: Prospect of Large-Scale Modeling in Seawater Surface and Its Environmental Significance | |||||
24247. 题目: Cation exchange membrane behaviour of extracellular polymeric substances (EPS) in salt adapted granular sludge This paper aims to elucidate the role of extracellular polymeric substances (EPS) in regulating anion and cation concentrations and toxicity towards microorganisms in anaerobic granular sludges adapted to low (0.22 M of Na+) and high salinity (0.87 M of Na+). The ion exchange properties of EPS were studied with a novel approach, where EPS were entangled with an inert binder (PVDF-HFP) to form a membrane and characterised in an electrodialysis cell. With a mixture of NaCl and KCl salts the EPS membrane was shown to act as a cation exchange membrane (CEM) with a current efficiency of ∼80%, meaning that EPS do not behave as ideal CEM. Surprisingly, the membrane had selectivity for transport of K+ compared to Na+ with a separation factor () of 1.3. These properties were compared to a layer prepared from a model compound of EPS (alginate) and a commercial CEM. The alginate layer had a similar current efficiency (∼80%.), but even higher of 1.9, while the commercial CEM did not show selectivity towards K+ or Na+, but exhibited the highest current efficiency of 92%. The selectivity of EPS and alginate towards K+ transport has interesting potential applications for ion separation from water streams and should be further investigated. The anion repelling and cation binding properties of EPS in hydrated and dehydrated granules were further confirmed with microscopy (SEM-EDX, epifluorescence) and ion chromatography (ICP-OES, IC) techniques. Results of specific methanogenic activity (SMA) tests conducted with 0.22 and 0.87 M Na+ adapted granular sludges and with various monovalent salts suggested that ions which are preferentially transported by EPS are also more toxic towards methanogenic cells. | |||||
24248. 题目: Soil pH and C/N ratio determines spatial variations in soil microbial communities and enzymatic activities of the agricultural ecosystems in Northeast China: Jilin Province case Soil microbes and their functions play important roles in the sustainable development of agricultural ecosystems but are vulnerable to climate change and human activity. We measured the contents of microbial phospholipid fatty acids (PLFAs) and enzymatic activities in various soil types (dark-brown soil, albic soils, black soil, chestnut soil, and chernozem) in three climatic zones (humid zone, subhumid zone, and semi-arid zone) of the Songnen Plain in northeastern China. The objectives were to investigate the spatial variations in community structure of soil microbes and to evaluate the functional potential of the microbes in croplands in northeastern China. The C-acquiring activities were highest in the chernozem soil of the semi-arid zone, but N-acquiring and P-acquiring activities and peroxidase were highest in the albic soil of the humid and subhumid zone. Phosphorus deficiencies were indicated by the reduced ratios of N- relative to P-acquiring activity and C-relative to P-acquiring activity in the croplands compared with the global average. Different groups of PLFA contents were highest in the dark-brown soil of the humid zone and the chestnut soil of the semi-arid zone. The community compositions of the microbes varied amongst the soil types and climatic zones, with the ratios of fungi/bacteria and Gram-positive/Gram-negative bacteria highest in chernozemic soil of the semi-arid zone. The variations in soil enzyme activities and microbial community structure were more dependent on climate conditions than soil type. Soil pH, soil organic C content, and the C/N ratio were the most important factors affecting the spatial patterns of the soil enzyme activities and microbial-community compositions across soil types and climatic zones. Mean annual precipitation and clay content strongly influenced enzymatic activities and microbial-community compositions, respectively, when each variable was used as the only factor. Their effects, however, were negligible when combined with other factors. Balanced chemical fertilizer with scientific N-P-K ratio should be applied instead of only N fertilizers. The other combination of different conservational agricultural practices, such as application of organic fertilizer, not tilling, crop rotation, and intercropping, would be more beneficial for restoring the community compositions and functions of soil microbes and achieving sustainable agricultural development. | |||||
24249. 题目: Changes in the chemical and biological characteristics of grape marc vermicompost during a two-year production period In this study, the changes in the chemical and biological characteristics of a grape marc vermicompost during a two-year production period were studied to determine the time required for completion of the maturation phase and production of stable vermicompost. Grape marc was added to the surface of a vermireactor monthly for two years. At the end of the experiment, the resulting vermicompost was 100 cm deep and consisted of layers of fresh (top) to processed (bottom) grape marc approximately 15, 30, 180, 360, 540 and 720 days old. Several chemical and biological characteristics were measured in each vermicompost layer at the end of the experiment: the moisture content; pH; electrical conductivity; organic matter content; total and dissolved carbon content; C:N ratio; nutrient content; earthworm density; basal respiration; and the activity of 12 enzymes associated with the carbon, nitrogen, phosphorus and sulfur cycles. The earthworm density increased 30-fold during the two-year period. In addition, the pH and electrical conductivity as well as the organic matter, total carbon, dissolved organic nitrogen, phosphorus, potassium and copper contents all decreased, while the calcium, sulfur, zinc and manganese contents increased. Basal respiration and carboxylesterase, peroxidase and catalase activities were highest during the first 30 days. By contrast, the urease, acid phosphatase, alkaline phosphatase and arylsulfatase activities were greater after 30 days. The major changes in vermicompost occurred during the initial phase of vermicomposting. However, the chemical and biological characteristics continued to vary during the maturation phase because of microbial activity. Thus, the quality of vermicompost greatly depended on the duration of the maturation (conditioning) phase; therefore, it was difficult to determine the time required to yield a stable product. | |||||
24250. 题目: Changes of substrate microbial biomass and community composition in a constructed mangrove wetland for municipal wastewater treatment during 10-years operation Constructed wetlands (CWs) have been used for wastewater treatment for decades, but research on microorganisms involved, especially long-term changes, is still limited. In this study, we evaluated changes in the substrate microbial community in a pilot-scale horizontal subsurface-flow constructed mangrove wetland during 10-years operation. In the 3rd year of operation, microbial biomass carbon and phospholipid fatty acids (PLFAs) reached peak values in two vegetated belts planted with Aegiceras corniculatum (Ac) and Kandelia obovata (Ko), respectively, then stabilized or declined in the 9th and 10th years of operation. PLFA profiles reflecting microbial community compositions varied significantly in the Ac belt during the operation period. Principal component (PCA) and redundancy analyses (RDA) revealed that microbial community compositions were significantly correlated with organic matter content, especially in the 9th and 10th years of operation, implying that the substrate microbial community in constructed mangrove wetland is sensitive to substrate characteristics and can be used as an indicator for long-term performance of CWs. | |||||
24251. 题目: Bulk sedimentary phosphorus in relation to organic carbon, sediment textural properties and hydrodynamics in the northern Beibu Gulf, South China Sea Bulk sedimentary phosphorus (P) is studied to evaluate its source, distribution, preservation and enrichment in relation with organic carbon (OC), sediment textures and moisture contents in the northern Beibu Gulf. Approximately 80% of surface sediments in the investigated sites were composed of coarse sandy texture (>63 μm). Total P (TP), inorganic P (IP) and organic P (OP) contents were lower to medium range compared to the levels reported for other marginal seas. Sedimentary OC and P were derived from mixed sources, with high terrestrial influence in the coastal areas (molar OC/OP ratios >250:1). The distribution of P corroborated with the variation tendency of fine-grained sediments, moisture contents and OC. Both IP and OP may significantly influence the trophic state of seawater if released from surface sediments. Influenced by hydrodynamics, frequent resuspension and high abundance of sand, TP is less preserved, and shows low to moderate enrichment in surface sediments. | |||||
24252. 题目: Electrochemical behavior of biochar and its effects on microbial nitrate reduction: Role of extracellular polymeric substances in extracellular electron transfer Biochar is extensively used in the remediation of pollutants because of its diverse physicochemical properties. Biochar application can alter the activity of microbial communities involved in bioremediation. However, the electrochemical behavior of biochar and its potential effect on microbial nitrate reduction remains unknown. Electron transfer between microbial cells and electron donor or acceptor species is often across extracellular polymeric substances (EPS). However, the role of EPS in extracellular electron transfer remains unclear. In this study, we examined the electrochemical behavior of biochar and its effects on microbial nitrate reduction to elucidate the role of EPS in extracellular electron transfer (EET). The biochar prepared by the pyrolysis of Aspen wood chips at 400–600 °C. Electrochemical analysis using cyclic voltammetry, electrochemical impedance spectrum, and chronoamperometry showed that biochars could donate and accept electrons. BC 400, BC 500, and BC 600 had an electron donating capacity of 1.03 mmol e− g−1, 0.9 mmol e− g−1, and 0.8 mmol e− g−1, respectively. Furthermore, biochars prepared at 400 °C significantly enhanced the microbial nitrate reduction process. The phenol OH and quinone CO surface functional groups on the biochar probably contributed to the overall electron exchange, and this accelerated the nitrate reduction. Electrochemical analysis revealed that the outer membrane c-type cytochrome and flavin proteins from the biofilm were involved in the electron transfer process, with the EPS acting as a transient media for the microbially-mediated EET. Overall, this study suggested that biochar may be effectively used as an eco-friendly material for the enhancement of microbial denitrification. | |||||
24253. 题目: Combining high electron transfer efficiency and oxidation resistance in nZVI with coatings of microbial extracellular polymeric substances to enhance Sb(V) reduction and adsorption In this work, we prepared microbial extracellular polymeric substances-coated nano zero valent iron () for Sb(V) removal. Batch adsorption experiments showed that the synthesized had superior maximum adsorption capacity (202 mg/g at pH = 5) for Sb(V), much higher than that of bare nZVI especially under nonacidic conditions. The adsorption results fit the pseudo-second-order kinetic model and the Redlich-Peterson model well, implying that the adsorption was more like a chemical adsorption process. The spectral analysis showed that EPS could protect inner Fe0 from air, preventing nZVI from generating a passivation layer on the surface, and decreasing the concentration of hydroxyl radicals in aqueous environment, which increased the reactivity of nZVI and strengthened the reducibility and adsorbability of nZVI. The coated EPS can improve the reactivity of nZVI instead of inhibiting its electron transfer. Moreover, the electrostatic repulsion between and Sb(OH)6− was decreased compared to that of bare nZVI after the introduction of EPS. The functional groups of EPS could play a significant role in the reduction adsorption, especially under alkaline conditions where nZVI was passivated. This work proved that has great prospects in simultaneously combining the reduction activity of nZVI in water and its stability in air. | |||||
24254. 题目: Hydochar and biochar: Production, physicochemical properties and techno-economic analysis Utilization of natural, abundant, and renewable resources for the production of carbon materials with simple and energy-efficient processes is an upsurge interest. The production processes and resultant biochar can address widespread concerns such as climate change, energy crisis, and environmental pollution. The properties of produced chars (biochar/hydrochar) depend on the production methods, feedstock's, and operating parameters, which significantly affect their use for various applications. In this review, production, physiochemical properties, and techno-economic analysis of chars are summarized. This review provides the fundamentals and reaction mechanism of char's production methodologies. Physicochemical properties based on chemical composition, functional groups, structure, porosity, and shapes have been compared. The effects of operating parameters on the physicochemical properties of chars are discussed. In addition, this review offers insights on new directions for char production and research in the future, based on the updated and detailed investigation of energy balance with economy of char's production methodologies. | |||||
24255. 题目: Wood-based activated biochar to eliminate organic micropollutants from biologically treated wastewater Implementing advanced wastewater treatment (WWT) to eliminate organic micropollutants (OMPs) is a necessary step to protect vulnerable freshwater ecosystems and water resources. To this end, sorption of OMP by activated carbon (AC) is one viable technology among others. However, conventional AC production based on fossil precursor materials causes environmental pollution, including considerable emissions of greenhouse gases. In this study, we produced activated biochar (AB) from wood and woody residues by physical activation and evaluated their capability to eliminate OMPs in treated wastewater. Activated biochar produced under optimized conditions sorbed 15 model OMPs, of which most were dissociated at circumneutral pH, to the same or higher extent than commercial AC used as a reference. While wood quality played a minor role, the dosage of the activation agent was the main parameter controlling the capacity of ABs to eliminate OMP. Our results highlight the possibility for local production of AB from local wood or woody residues as a strategy to improve WWT avoiding negative side effects of conventional AC production. | |||||
24256. 题目: Effects of abandonment management on soil C and N pools in Moso bamboo forests Moso bamboo (Phyllostachys Pubescens) forests exhibit a great potential to sequestrate carbon dioxide from atmosphere and to mitigate global climate change. However, they were increasingly under abandoned (i.e., no fertilization, the low intensity and frequency of felling and bamboo shoot digging) due to decreasing economic values of bamboo-related products and increasing labor cost. So far, the changes in soil carbon (C) and nitrogen (N) pools in bamboo forests following abandonment are poorly addressed. In this study, Moso bamboo stands under intensively management and abandonment for different durations were sampled to explore the C and N pool dynamics at the top 40 cm soil. We classified abandonment durations into three categories: discarded or abandoned management for 1–6 years (DM-I), 7–12 years (DM-II) and 13–18 years (DM-III). Our results indicated that (1) soil organic carbon (SOC) storage was significantly increased with abandonment management compared with intensive management (Control, CK), but the durations of abandonment management had no significant effects on SOC. Microbial biomass carbon (MBC) concentration increased from DM-I to DM-III in the 0–40 cm soil layer (P < 0.01), and water-soluble organic carbon (WSOC) concentration decreased through DM-I (P < 0.01). (2) Abandonment management did not significantly affect soil total nitrogen (TN) storage at depth of 0–40 cm, with 9.54 Mg ha−1 for CK, 9.59 Mg ha−1 for DM-I, 9.89 Mg ha−1 for DM-II and 9.69 Mg ha−1 for DM-III. Water-soluble organic nitrogen (WSON) concentration significantly decreased from CK to DM-III. Ammonium nitrogen (NH4+-N) concentration increased from DM-I to DM-III (P < 0.01), and nitrate nitrogen (NO3−-N) concentration decreased from CK to DM-III (P < 0.01). The results of the effects of abandonment durations on soil properties in Moso bamboo forests provide valuable information for forest restoration and management. | |||||
24257. 题目: Are there environmental or agricultural benefits in using forest residue biochar in boreal agricultural clay soil? Short-term agronomic and environmental benefits are fundamental factors in encouraging farmers to use biochar on a broad scale. The short-term impacts of forest residue biochar (BC) on the productivity and carbon (C) storage of arable boreal clay soil were studied in a field experiment. In addition, rain simulations and aggregate stability tests were carried out to investigate the potential of BC to reduce nutrient export to surface waters. A BC addition of 30 t ha−1 increased soil test phosphorus and decreased bulk density in the surface soil but did not significantly change pH or water retention properties, and most importantly, did not increase the yield. There were no changes in the bacterial or fungal communities, or biomasses. Soil basal respiration was higher in BC-amended plots in the spring, but no differences in respiration rates were detected in the fall two years after the application. Rain simulation experiments did not support the use of BC in reducing erosion or the export of nutrients from the field. Of the C added, on average 80% was discovered in the 0–45 cm soil layer one year after the application. Amendment of boreal clay soil with a high rate of BC characterized by a moderately alkaline pH, low surface functionalities, and a recalcitrant nature, did not induce such positive impacts that would unambiguously motivate farmers to invest in BC. BC use seems unviable from the farmer's perspective but could play a role in climate change mitigation, as it will likely serve as long-term C storage. | |||||
24258. 题目: Accumulation of organic matter in a mesotidal Mediterranean lagoon (Boughrara, Tunisia) In the frame of the COZOMED project, concentrations of organic matter (TOC, DOC, POC) were monitored during two seasonal field campaigns (autumn, October 2016 and spring, April 2017) in the Boughrara Lagon, Tunisia. Results indicate strong influence of the seawater exchange and circulation, on the organic matter accumulation inside the lagoon, visible through a significant correlation between TOC and salinity in both seasons. Two times higher concentration of TOC (up to 5.5 mg/l) was recorded in autumn, when high salinity water (46 psμ) was present in the lagoon. POC made a relatively small percentage of TOC in autumn samples when high accumulation of TOC, especially its DOC fraction can be related with the remineralization processes and zooplankton-mediated release of DOC. Indeed, PCA analysis identified DOC as the most significant factor influencing the observed variability in autumn samples, and correlated to NH4+ (p < 0.05) in surface water, while POC was significantly (p < 0.05) correlated to chlorophyll a. During spring, organic matter in the lagoon was depth-dependent and under the high influence of salinity and temperature, and in the surface correlated to N03-. Satellite data on lagoon water optical properties appear to support changes in measured organic matter concentrations indicating different optical properties of the water inside the lagoon during spring and autumn seasons. The ocean color remote sensing, with properly validated and tested robust algorithms, accommodating optically shallow waters, can provide valuable tools for monitoring and timely detection of possibly detrimental changes inside the lagoon. | |||||
24259. 题目: Effects of woody biochar on dry thermophilic anaerobic digestion of organic fraction of municipal solid waste This study presents the results of semi-pilot scale anaerobic digestion tests conducted under dry thermophilic conditions with the addition of biochar (6% on fresh mass basis of inoculum), derived from an industrial gasification plant, for determining biogas and biomethane production from organic fraction of municipal solid waste. By using two types of inocula (from a full-scale dry anaerobic digestion plant and from lab-scale biomethanation tests), the obtained experimental results did not show significant increase in methane yield related to the presence of biochar (330.40 NL CH4 kgVS−1 using plant inoculum; 335.41 NL CH4 kgVS−1 using plant inoculum with biochar, 311.78 NL CH4 kgVS−1 using lab-inoculum and 366.43 NL CH4 kgVS−1 using lab-inoculum with biochar), but led to significant changes in the microbial community composition. These results are likely related with the specific biochar physical-chemical features and low adsorption potential. Resulting digestate quality was also investigated: biochar-enriched digestates were characterized by increased biological stability (809 ± 264 mg O2 kgVS−1 h−1 vs. 554 ± 76 mg O2 kgVS−1 h−1 for biochar-free and biochar-enriched digestates, respectively), lower heavy metals concentrations (with the exception of Cd), but higher polycyclic aromatic hydrocarbons content, with a reported maximum concentration of 8.9 mgPAH kgTS−1 for biochar-enriched digestate derived from AD test with lab-inoculum, which could trigger non-compliance with regulation limits for agricultural reuse of digestates. However, phytotoxicity assessments showed a decreased toxicity of biochar-containing digestates when compared to biochar-free digestates. | |||||
24260. 题目: Biochar addition leads to more soil organic carbon sequestration under a maize-rice cropping system than continuous flooded rice Crop rotation of flooded rice with an upland crop like maize on previous continuous paddy soils is an emerging cropping system in South China. A four-year experiment was conducted at a research area in Hunan province, having a long history of double paddy-rice cropping throughout the year. Maize was introduced as an upland crop in rotation with paddy rice, thus providing two parallel cropping systems i.e., the previous flooded rice-rice (R–R) and the new maize-rice rotation (M–R) systems. We used three treatments in both cropping systems; namely, farmer's practice (without external C input) as a control, straw addition, and biochar addition. The straw and biochar were added to soil in late rice season on an equal C input basis (3000 kg C ha−1yr-1). In the R–R plots, rice straw was added while in M–R plots maize straw was added during late rice field preparation. Our results show that there were no changes in soil organic carbon (SOC) concentration when R–R was replaced by M–R rotation. Straw addition had no effect on SOC but improved late rice yield. Biochar addition significantly increased SOC and late rice yield in both cropping systems. Moreover, biochar addition resulted in a more significant accumulation of SOC (9% higher) in M–R than R–R. Among soil aggregates, only the 0.25–2 mm fraction had a significantly higher SOC concentration with biochar relative to the control and straw return; and this increase was significantly more pronounced under M–R (28% higher) than R–R cropping system. In general, a significantly higher proportion of small macro-aggregates (0.25–2 mm) were found under M–R, while smaller aggregates (0.05–0.25 and <0.05 mm) were more abundant under R–R. δ13C analyses from M–R plots reveal that the quantity of maize-derived C was marginally higher in the straw treatment than control, but this was not reflected in any significant impact on total SOC of the bulk soil or of aggregates. In conclusion, no detectable changes in SOC were observed over four years experimental period following shift from R-R to M-R cropping system. M-R system with biochar addition led to higher productivity and environmental benefits. | |||||
