Organic Carbon Source Research Articles

Growth and Lipid Production of Ankistrodesmus Sp. IFRPD 1061 Under Mixotrophic Culture Condition: Effect of Sodium Acetate Concentration and Period Addition of Sodium Acetate in an Open Pond

AbstractMicroalgae with increased amount of biomass and lipid yield are crucial for biodiesel production. Mixotrophic cultivation has prominence for increasing the micro‐algal cell concentration and hence the volumetric productivity owing to independent utilization of both the photo‐assimilation of CO2 and oxidative assimilation of organic carbon sources. In this study, Ankistrodesmus sp. IFRPD 1061 was examined under various concentrations of sodium acetate for concentration and productivity of biomass and lipid, lipid contents (LCs), and fatty acid profiles. The optimum condition was obtained at Day 21 with 10 mM sodium acetate, which gave 6.940 ± 0.057 g L−1 biomass concentration, 327.619 ± 2.020 mg L−1 day−1 biomass productivity, 2.795 ± 0.191 g L−1 lipid concentration, 131.955 ± 9.275 mg L−1 day−1 lipid productivity, and 40.286 % ± 3.079 % w/w LC. The optimum condition (10 mM sodium acetate) in an open pond cultivation attained maximum values at Day 14, that is, 0.575 ± 0.004 g L−1 biomass concentration, 38.161 ± 0.076 mg L−1 day−1 biomass productivity, 0.203 ± 0.002 g L−1 lipid concentration, 13.440 ± 0.197 mg L−1 day−1 lipid productivity, and 35.219 % ± 0.585 % w/w LC. The lipids recovered from mixotrophic micro‐algae were primarily unsaturated fatty acids, which are appropriate to produce biodiesel. The results revealed that a 10 mM sodium acetate concentration can enhance lipid accumulation within algal cells.

Effect of glucose addition on the morphology and activity of ZnO supported on mesoporous zeolite SBA-15 for the removal of hydrogen sulfide

Zinc oxide with its high equilibrium constant for sulfidation, can be utilized to purify H2S-containing gases, but its low kinetics at room temperature limits its sulfur loading capacity. This study use glucose as an organic additive and carbon source to prepare carbon doped ZnO adsorbents with different ZnO loadings (5-20wt%) through initial wet impregnation. It was observed that the sulfur capacity of 15wt% Zn/SBA-15-G (10.9mg/g) was approximately 1.65 times higher than that of 15wt% Zn/SBA-15 (6.6mg/g). This improvement was attributed to the use of glucose, which led to better ZnO dispersion, a narrower distribution of ZnO particle size, and the formation of C-O-Zn bonds that increased the number of hydroxyl groups on the ZnO surface. DFT calculations also indicated that carbon doping could lower the activation energy of the reaction between ZnO and H2S and shorten the reaction pathway. Consequently, the prepared ZnO adsorbent demonstrated enhanced desulfurization efficiency at room temperature. Furthermore, regeneration experiments conducted on the desulfurizer after use revealed that achieving complete regeneration is a challenge.

Significant annual variations of firework-impacted aerosols in Northeast China: Implications for rethinking the firework bans

Fireworks are banned in many Chinese cities but never eliminated, reflecting strong public demand on this traditional activity for festival celebrations. On the other hand, the assessment of firework contributions to air pollution remains vague, raising concerns on the necessity of the mandatory bans. Here we investigated the characteristics of firework episodes in a megacity in Northeast China, based on field campaigns conducted in four successive winters during 2018–2022. Although prohibited, the firework influences remained evident during the Chinese New Year periods, as suggested by the enhancements of water-soluble potassium (K+). In addition, significant annual variations were identified for the firework episodes, with the following features observed. First, the firework-induced enrichment ratios of K+ and chloride exhibited increasing trends across years, climbing from 4.4 to 8.6 and from 1.7 to 2.9, respectively. Second, the enrichment ratio of sulfate dropped from 2.8 to 1.6, indicating that the firework contributions to sulfate decreased but remained considerable. Third, fireworks turned into an unimportant source for organic carbon and nitrate in the most recent winter of 2021–2022, with enrichment ratios of ∼1 for both species. Fourth, the firework-driven increases in fine particle concentration were as high as ∼100% for the two winters during 2019–2021, whereas the increase dropped sharply to ∼30% for 2021–2022. These variations were in line with the promotion of environmentally friendly fireworks. Our results indicated that the air pollution caused by fireworks could be reduced substantially by advanced manufacturing technologies and thus it is time to rethink the firework bans.

Distinct impacts of microplastics on the carbon sequestration capacity of coastal blue carbon ecosystems: A case of seagrass beds

Seagrass beds, as an important coastal blue carbon ecosystem, are excellent at storing organic carbon and mitigating the impacts of global climate change. However, seagrass beds are under threat due to increased human activities and ubiquitous presence of microplastics (MPs) in marine environments. Bibliometric analysis shows that the distribution and accumulation of microplastics in seagrass beds has been widely documented worldwide, but their impacts on seagrass beds, particularly on carbon sequestration capacity, have not been given sufficient attention. This review aims to outline the potential impacts of MPs on the carbon sequestration capacity of seagrass ecosystems across five key aspects: (1) MPs act as sources of organic carbon, contributing to direct pollution in seagrass ecosystems; (2) Impacts of MPs on seagrasses and their epiphytic algae, affecting plant growth and net primary productivity; (3) Impacts of MPs on microorganisms, influencing production of recalcitrant dissolved organic carbon and greenhouse gas; (4) Impacts of MPs on seagrass sediments, altering the quality, structure, properties and decomposition processes of plant litters; (5) Other complex impacts on the seagrass ecosystems, depending on different behaviors of MPs. Latest progress in these fields are summarized and recommendations for future work are discussed. This review can provide valuable insights to facilitate future multidisciplinary investigations and encourage society-wide implementation of effective conservation measures to enhance the carbon sequestration capacity of seagrass beds.

The super-intensive culture of Penaeus vannamei in low salinity water: A comparative study among recirculating aquaculture system, biofloc, and synbiotic systems

The culture of Penaeus vannamei in inland regions using low salinity water is a reality in several regions of the world. The dissemination of culture techniques that allow high stocking density and reduced water use can be used to optimize the production process, but they require comparative studies to better understand the functioning of these systems in those salinity conditions. Therefore, this study aimed to analyze the effects of different culture systems, which were recirculating aquaculture system (RAS), biofloc technology (BFT), and synbiotic system (Synbiotic) on the water quality, plankton composition, and growth of P. vannamei in low salinity (2 g L−1) and high stocking density (500 shrimp m−3) for 30 days. The shrimp were stocked at a mean weight of 1.27 ± 0.06 g. In the BFT, dextrose was used as the organic carbon source and administered at a carbon: nitrogen ratio of 15:1. In the Synbiotic, rice bran processed by probiotic microorganisms was used as an organic fertilization strategy. In the RAS treatment, all nitrogen species remained stable throughout the trial, without spikes, and with ammonia and nitrate concentrations lower than in BFT and Synbiotic. The BFT treatment had more events when total ammonia nitrogen exceeded 1 mg L−1, requiring water changes. The Synbiotic treatment had better control of nitrogenous compounds, and a more accentuated accumulation of nitrate compared to BFT, suggesting more effective nitrification. The BFT treatment had more microalgae than Synbiotic and RAS. However, the abundance of zooplankton was higher than that of phytoplankton in BFT and Synbiotic, indicating a dominance by heterotrophic organisms. The Synbiotic treatment had a higher abundance of ciliates and amoeba than the other treatments. Furthermore, the Synbiotic treatment provided higher survival, yield, and lower FCR than BFT and RAS. Our findings indicate that the Synbiotic system can be considered as an alternative for the P. vannamei super-intensive culture in low salinity water, as it presented better control of nitrogenous compounds compared to BFT, higher abundance of ciliates and amoeba, and provided better production rates to the culture.

A global assessment of mangrove soil organic carbon sources and implications for blue carbon credit.

Mangroves can retain both autochthonous and allochthonous marine and/or terrestrial organic carbon (OC) in sediments. Accurate quantification of these OC sources is essential for the proper allocation of blue C credits. Here, we conduct a global-scale analysis of sediments autochthonous and allochthonous OC contributions in estuarine and marine mangroves using stable isotopes. Globally, mangrove-derived autochthonous OC was the main contributor to estuarine and marine mangrove top-meter soil organic carbon (SOC) (49% and 62%, respectively). Less marine allochthonous OC (21%) was deposited than terrestrial allochthonous OC (30%) in estuarine mangrove sediments. Estuarine mangroves accumulated more SOC in sediments than marine mangroves (282 ± 8.1 Mg C ha-1 and 250 ± 5.0 Mg C ha-1, respectively), primarily due to the additional terrestrial OC inputs. Globally, marine mangroves held 67% of the total mangrove SOC, reaching 3025 ± 345 Tg C, while 1502 ± 154 Tg C was stored in estuarine mangrove sediments. The findings emphasize the substantial influence of coastal environmental settings on OC contributions, underlining the necessity of accurate OC source quantification for the effective allocation of blue carbon credits.

Characterization of Phytoplankton-Derived Amino Acids and Tracing the Source of Organic Carbon Using Stable Isotopes in the Amundsen Sea.

We utilized amino acid (AA) and carbon stable isotope analyses to characterize phytoplankton-derived organic matter (OM) and trace the sources of organic carbon in the Amundsen Sea. Carbon isotope ratios of particulate organic carbon (δ13C-POC) range from -28.7‱ to -23.1‱, indicating that particulate organic matter originated primarily from phytoplankton. The dissolved organic carbon isotope (δ13C-DOC) signature (-27.1 to -21.0‱) observed in the sea-ice melting system suggests that meltwater contributes to the DOC supply of the Amundsen Sea together with OM produced by phytoplankton. A negative correlation between the degradation index and δ13C-POC indicates that the quality of OM significantly influences isotopic fractionation (r2 = 0.59, p < 0.001). The AA distribution in the Amundsen Sea (5.43 ± 3.19 µM) was significantly larger than previously reported in the Southern Ocean and was associated with phytoplankton biomass (r2 = 0.49, p < 0.01). Under conditions dominated by P. antarctica (DI = 2.29 ± 2.30), OM exhibited greater lability compared to conditions co-dominated by diatoms and D. speculum (DI = 0.04 ± 3.64). These results highlight the important role of P. antarctica in influencing the properties of OM, suggesting potential impacts on carbon cycling and microbial metabolic activity in the Amundsen Sea.

Effects of maize residue and biochar applications on soil δ13C and organic carbon sources in a subtropical paddy rice ecosystem

AbstractThis study investigates the utility of plant δ¹3C natural labeling in predicting the impacts of environmental shifts on carbon cycling within ecosystems, particularly focusing on paddy fields treated with maize (Zea mays L.) residues and biochar. Specifically, it examines how soil δ¹3C and the sources of soil organic carbon (SOC), respond in paddy fields (which cultivate C3 plants like rice) when amended with maize residues, maize biochar, and silica‐enriched biochar (derived from C4 plants). Conducted in the Fuzhou paddy fields, the experiment included control groups and treatment groups with maize residue (4 t ha⁻¹), maize biochar (4 t ha⁻¹), and silicon‐modified maize biochar (4 t ha⁻¹) during both the early and late rice growth periods. The results indicate that all soil treatments increased soil δ¹3C. The application of maize residues notably affected the δ¹3C of the upper soil profile (0–15 cm) differently from the deeper layers (15–30 cm), and it increased soil organic C more than biochar or silicon‐modified maize biochar. Soil available P (AP) and pH emerged as significant factors linking δ¹3C, influencing rice yield through changes in soil physicochemical properties. Unlike maize residues, which reduced rice yields, applications of biochar and silicon‐modified maize biochar increased rice yields. The latter, which was particularly effective in lowering SOC decomposition rates and addressing rice's silica needs, emerged as the preferred option. The study highlights maize biochar and silicon‐modified maize biochar as sustainable alternatives to maize residues for rice cultivation, enhancing soil fertility, carbon pool stability, and yields.

Efficiency of Penicillium sp. and Aspergillus sp. for bioleaching lithium cobalt oxide from battery wastes in potato dextrose broth and sucrose medium

Lithium-ion batteries, a primary power source, generate electronic hazardous waste at the end of their lifespan, which is a richer source of highly concentrated metals such as cobalt and lithium than those in natural resources. The waste is a potential renewable resource for the extraction of metals. Bioleaching, a process utilizing microbial activity, was used in this study to investigate the cobalt and lithium leaching efficiency from battery wastes. Two fungal strains, Aspergillus sp. strain JMET 15 and Penicillium sp. strain JMET 24 were used with different organic carbon sources (sucrose medium and potato dextrose broth) at 1 % pulp density. The sucrose medium derived a higher acid quantity and leached higher concentration of cobalt and lithium than in potato dextrose broth. Leaching efficiency by JMET 24 was higher than JMET 15. Cobalt (32.57 % and 27.19 %) and lithium (65.07 % and 40.58 %) were bioleached by JMET 24 and JMET 15, respectively, after 30 d cultivation in the sucrose medium. Lower pulp density was conducted to achieved higher leaching efficiency by JMET24, cobalt (77.87 % and 74.5 %) and lithium (99.88 % and 78.4 %) were bioleached at 0.1 % and 0.5 % pulp density, respectively. Cobalt oxide (Co3O4) was the product of the one-step recovery (leaching and precipitation) process. Cobalt was transformed from lithium cobalt oxide to cobalt phosphate-oxalate by JMET 24 in the sucrose medium. Thus, the potential of bioleaching as an effective method for recovering valuable metals from lithium-ion battery waste is demonstrated, presenting a promising approach for both waste management and resource recovery.

Source of Ore-Forming Fluids and Ore Genesis of the Batailing Au Deposit, Central Jilin Province, Northeast China: Constraints from Fluid Inclusions and H-O-C-S-Pb Isotopes

The Batailing Au deposit is a vein-type deposit in central Jilin Province, situated in the southern sector of the Lesser Xing’an–Zhangguangcai Range within the eastern Central Asian Orogenic Belt. NE-trending fault-controlled orebodies occur in the Upper Permian Yangjiagou Formation and quartz diorite–porphyrite. The mineralisation process was delineated into three stages: (I) quartz–arsenopyrite–pyrite, (II) quartz–polymetallic sulphides (main Au mineralisation stage), and (III) quartz–pyrite–carbonate. Fluid inclusions (FIs) in quartz were identified as four types: PC-type (pure CO2), C1-type (CO2-bearing), C2-type (CO2-rich), and W-type (aqueous two-phase). Raman spectroscopy analysis revealed that the vapor components of the FIs predominantly comprised CO2 with minor quantities of CH4 in stages I–II. Stages I and II encompassed four types of FIs with homogenisation temperature ranging from 264 to 332 °C and 213 to 292 °C and salinity spanning from 4.7 to 11.2 wt% and 1.8 to 11.6 wt%, respectively. Stage III exclusively contained W-type FIs with homogenisation temperature ranging from 152 to 215 °C and salinity spanning from 1.4 to 6.4 wt%. H-O isotopic values (δD = −84 to −79.6‰, δ18OH2O = 6.2 to 6.4‰ in stage I and δD = −96.4 to −90.4‰, δ18OH2O = 2.8 to 4.4‰ in stage II) and microthermometric data indicated that the ore-forming fluids are initially from a magmatic source, with later meteoric water input. Low C isotopic data from CO2 in FIs in quartz (−24.4 to −24.3‰ in stage I and −23.7 to −22.6‰ in stage II) indicated an organic carbon source. Ore precipitation is mainly attributable to fluid immiscibility. S-Pb isotopic data (δ34S = −3.5 to −1.6‰; 206Pb/204Pb = 18.325–18.362, 207Pb/204Pb = 15.523–5.562, 208Pb/204Pb = 38.064–38.221) revealed that ore metals primarily originated from magma. Based on this research, the origin of the Batailing Au deposit is of the mesothermal magmatic–hydrothermal lode type.

Composition and Biogeochemical Effects of Carbohydrates in Aerosols in Coastal Environment

We adopted a simple and rapid measurement method to analyze the concentrations of monosaccharides (MCHO) and polysaccharides (PCHO) in carbohydrates, a subset of organic carbon found in size-fractionated atmospheric particles. Seasonal and source-related factors influenced carbohydrate concentrations, with total water-soluble carbohydrates (TCHO) accounting for approximately 23% of the water-soluble organic carbon (WSOC) in spring when biological activity was high. We observed that the mode of aerosol transport significantly influenced the particle size distribution of carbohydrates, with MCHO exhibiting relatively high concentrations in fine particles (&lt;1 μm) and PCHO showing higher concentrations in coarse particles (&gt;1 μm). Moreover, our results revealed that MCHO and PCHO contributed 51% and 49%, respectively, to the TCHO concentration. This contribution varied by approximately ±19% depending on the season, suggesting the importance of both MCHO and PCHO. Additionally, through the combined use of principal component analysis (PCA) and positive matrix factorization (PMF), we determined that biomass burning accounts for 30% of the aerosol. Notably, biomass burning accounts for approximately 52% of the WSOC flux, with MCHO accounting for approximately 78% of the carbon from this source, indicating the substantial influence of biomass burning on aerosol composition. The average concentration of TCHO/WSOC in the atmosphere was approximately 18%, similar to the marine environment, reflecting the relationship between the biogeochemical cycles of the two environments. Finally, the fluxes of MCHO and PCHO were 1.10 and 5.28 mg C m−2 yr−1, respectively. We also found that the contribution of atmospheric deposition to marine primary productivity in winter was 15 times greater than that in summer, indicating that atmospheric deposition had a significant impact on marine ecosystems during nutrient-poor seasons. Additionally, we discovered that WSOC accounts for approximately 62% of the dissolved organic carbon (DOC) in the Min River, suggesting that atmospheric deposition could be a major source of organic carbon in the region.

Impact of freeze-thaw cycles and influent C/N ratios on N2O emissions in subsurface wastewater infiltration systems

Subsurface wastewater infiltration system (SWIS) is important source of N2O emission, biological denitrification process relies on organic carbon source as electron donor, enabling denitrifying reductase (NAR, NIR, NOR, and N2OR) to reduce nitrate nitrogen to N2. However, freeze-thaw cycles cause changes in soil structure through physical and biological processes that increase organic matter availability and microbial activity, thereby accelerating upper (aerobic) organic matter degradation. This leads to carbon deficiency in the lower (anaerobic) layer, which reduces denitrification efficiency increasing N2O production and emissions. This study investigated effects of influent C/N ratios on N2O emissions from SWIS under freeze-thaw stress, and changes in denitrifying reductase and microbial communities. Results showed that as influent C/N ratio increased from 6:1–10:1, average TN removal of SWIS decreased from 89.59 % to 84.95 %, while N2O emission rate decreased from 0.106 mg·m−2·h−1 to 0.0333 mg·m−2·h−1, a reduction of 68.61 %. Meanwhile, N2OR activity increased by 29.95 % with C/N ratio increasing from 6 to 10, showing a significant reduction of N2O. High-throughput sequencing results revealed that Proteobacteria and Firmicutes showed a linear relationship with influent C/N. As C/N increased from 6 to 8 and 10, Proteobacteria relative abundance increased from 22.24 % ± 1.79–32.51 % ± 2.51 % and 39.59 % ± 3.45 %, while Firmicutes relative abundance decreased from 31.73 % ± 7.87–3.34 % ± 0.27 % and 2.19 % ± 0.07 %. These results indicated that sufficient supply of organic carbon provided abundant electron donors for denitrifying reductases in freeze-thaw-affected SWIS, promoting influent NO3--N reduction and decreasing N2O release rates. Conversely, under low C/N ratio conditions, electron acceptance capacity of N2OR was limited and N2OR activity was inhibited, resulting in N2O accumulation and emission. SynopsisThis paper shows how increasing the organic carbon supply in SWIS can reduce N2O emissions and improve nitrogen removal under freeze-thaw stress.

Effect of 9-year water and nitrogen additions on microbial necromass carbon content at different soil depths and its main influencing factors

Microbial necromass carbon (MNC) is a major source of soil organic carbon (SOC) pool, significantly influencing soil carbon sequestration. The effects of long-term water and nitrogen addition on MNC in soils at different depths, as well as their interactions, remain poorly understood. In this study, we examined the influence of water addition (+51.67 mm), nitrogen addition (25, 50, 100 kg N ha−1 yr−1), and their interactions on MNC accumulation at different soil depths in temperate grasslands. The addition of water and nitrogen over nine years has been observed to exhibit a decreasing trend in the MNC at different soil depths. Notably, MNC in the topsoil layer (0–10 cm) decreased significantly by 18.56 % under low nitrogen addition treatment, while MNC in the subsoil layer (40–60 cm) declined significantly by 27.19 % under high nitrogen addition treatment. Fungal microbial necromass carbon (FNC) contributed 3.25 times more to SOC than bacterial microbial necromass carbon (BNC). In the 0–10 cm soil layer, MNC is primarily governed by both microbial attributes and the physicochemical properties of the soil, in the 20–40 cm soil layer, the physicochemical properties of the soil predominantly control MNC, in the 40–60 cm layer, microbial characteristics exert a more significant influence on MNC. Collectively, our observations suggest that soil MNC decreased with the addition of water and nitrogen in the 0–60 cm soil slope, which could enable the accurate prediction of global change impacts on the accumulation of soil carbon, thus facilitating the implementation of strategies to augment soil carbon sequestration.

Organic carbon burial dynamics at the Chukchi Shelf margin: Implications for the Arctic Ocean carbon sink

Organic carbon (OC) burial plays a crucial role in regulating the Arctic Ocean's capacity to uptake atmospheric CO₂. In this study, we demonstrate the transport, deposition, and degradation patterns of different sources of OC to reveal burial dynamics at the Chukchi Shelf margin, a region with the highest primary production in the Arctic Ocean currently affected by dramatic sea ice retreat. Observations of suspended particulate material show a pronounced separation of terrestrial and marine OC in the water column, which subsequently influences OC lateral transport and differential deposition. Easily suspendable terrestrial OC is concentrated in the upper 10 m of water or sea ice and transported to the Canada Basin, where it undergoes severe degradation of fresh carbon in the water column and uppermost sediments. In contrast, faster-settling marine OC is more likely to be buried in the canyons and at the Chukchi Shelf margin, with ice algae contributing about 14 % and 55 % of OC burial in areas south and north of 73°N, respectively, leading to higher initial burial efficiency. Increasing Arctic marine primary production could thus enhance the region's role as a carbon sink over millennial timescales, although the burial efficiency of terrestrial OC will eventually exceed that of marine OC with prolonged burial time. Our findings highlight the importance of lateral transport, differential deposition, and selective degradation in Arctic carbon burial, providing a basis for objectively assessing the future capacity of the Arctic carbon sink and its feedback to climate change.

How human activities reshape carbon burial in estuarine sediment systems: Evidence from the Yangtze Estuary

Estuaries are critical zones for understanding the dynamics of organic carbon (OC) burial, particularly in the context of human intervention, yet detailed information remains limited. This study presents comprehensive field observations aimed at assessing the spatial and temporal variations in sedimentary OC sources, composition, and distribution within the Yangtze Estuary. By employing a three-endmember estimation, we determined the contributions of fluvial, marine, and salt marsh plants to OC in the mouth bar as 52 ± 6 %, 28 ± 12 %, and 20 ± 9 %, respectively. To address the complexities introduced by human activities and dispersal processes, we utilized a PCA-MC four-endmember model, which revealed that redispersal terrigenous organic matter from the outer estuary, categorized as “marine origin”, accounted for 26 ± 10 % re-deposited within the estuary. During the construction of the Deep Channel Navigation Project (DCNP), we observed a shift in terrigenous OC deposition from the North Passage (NP) to the South Passage (SP), along with an increased contribution from salt marsh plants. Post-DCNP completion, sedimentary OC compositions exhibited significant differences between the NP and SP, with the SP enriched in fresh terrigenous OC and the NP showing degraded signals due to dredging activities and source discrimination. Human interventions not only altered the estuarine geomorphology and hydrodynamics but also impacted OC burial and sequestration by modifying sources and compositions. This study highlights the transition of estuarine regions from carbon sinks to potential sources, underscoring the necessity for a comprehensive understanding of carbon cycle dynamics in Anthropocene-influenced estuarine environments.

Spatial and historical patterns of sedimentary organic matter sources and environmental changes in the Ross Sea, Antarctic: implication from bulk and n-alkane proxies

Organic carbon (OC) burial in the Antarctic marginal seas is essential for regulating global climate, particularly due to its association with ice shelf retreat. Here, we analyzed total OC (TOC), total nitrogen (TN), radiocarbon isotope, n-alkanes and relative indicators in surface and core sediments from the Ross Sea, West Antarctica. Our aim was to investigate spatial and historical changes in OC sources, and to explore the influencing factors and implications for ice shelf retreat since the last glacial maximum (LGM). Our results revealed distinct spatial patterns of OC sources as indicated by n-alkane indicators in surface sediments. In the Western Ross Sea, n-alkanes predominantly originated from phytoplankton and bacteria, as evidenced by their unimodal distribution, low carbon preference index (CPI) of short-chain n-alkanes (CPIL = 1.41 ± 0.30), and low terrestrial/aquatic ratio (TAR = 0.22 ± 0.14). In the Southwest Ross Sea, n-alkanes were derived from marine algae and terrestrial bryophytes, indicated by bimodal distribution, low ratio of low/high molecular-weight n-alkanes (L/H = 0.62 ± 0.21), low CPI of long-chain n-alkanes (CPIH = 1.18 ± 0.16), and high TAR (1.26 ± 0.66). In contrast, the Eastern Ross Sea exhibited n-alkanes that were a combination of phytoplankton and dust from Antarctic soils and/or leaf waxes from mid-latitude higher plant, as suggested by both unimodal and bimodal distributions, high L/H (1.60 ± 0.58) and CPIH (2.04 ± 0.28), and medium TAR (0.61 ± 0.30). Geologically, during the LGM (27.3 – 21.0 ka before present (BP)), there was an increased supply of terrestrial OC (TOC/TN = 13.63 ± 1.29, bimodal distribution of n-alkanes with main carbon peaks at nC17/nC19 and nC27). From 21.0 to 8.2 ka BP, as glaciers retreated and temperatures rose, the proportion of marine n-alkanes significantly increased (TOC/TN = 9.09 ± 1.82, bimodal distribution of n-alkanes with main carbon peaks at nC18/nC19 and nC25). From 8.2 ka BP to the present, as the ice shelf continued to retreat to its current position, the marine contribution became dominant (TOC/TN = 8.18 ± 0.51, unimodal distribution of n-alkanes with main carbon peak at nC17/nC18/nC19, and low TAR (0.41 ± 0.32)). This research has significant implications for understanding the variations in Antarctic OC sources and their climatic impacts in the context of accelerated glacier melting.

Using the check dam deposit for an individual event to document the sources and erosional loss of sediment-associated organic carbon from a small catchment on the Chinese Loess Plateau

Information on the sources and fate of organic carbon mobilized by soil erosion is crucial for understanding the impact of erosion on carbon (C) cycling. However, few studies have evaluated this in low-order stream systems. In this study, we adopted a novel approach, that used the sediment deposited behind a check dam constructed at the outlet of the Fengzigou catchment (0.91 km2) on the Chinese Loess Plateau by a single high magnitude storm event, to simplify the field sampling requirements. The total sediment-associated organic carbon (TOC) was fractionated into particulate organic carbon (POC) and mineral associated organic carbon (MOC). These results were combined with those from a sediment source tracing exercise. This made it possible to explore further the source and loss of the sediment-associated organic carbon. The results showed that the inter-gully areas contributed the most eroded TOC (52.3 ± 7.6 %) and, together with the gully walls, represented the main TOC source. The primary contributor of the POC fraction in the deposited sediment was the inter-gully areas (80.5 ± 12.6 %), whereas the gully walls were the main contributor of the MOC fraction (54.9 ± 10.2 %). The total output of sediment produced by the event was 1304 ± 48 t and the equivalent value for sediment-associated TOC was 2.94 ± 0.26 t, of which the POC fraction accounted for 27.6 ± 3.6 % and the MOC fraction 72.4 ± 9.8 %. The TOC lost (0.3 ± 0.02 t) through the mobilization and delivery processes was 10.2 ± 1.2 % of the TOC mobilized by erosion, and the lost carbon was dominated by the POC fraction (86.7 ± 8.8 %). The specific TOC output from the catchment associated with the event documented was 0.3 t km−2. This work demonstrates the potential for erosion-induced carbon redistribution to provide a source for atmospheric CO2 in the study area.

Carbohydrate Derived Value-added Products from Lignocelluloses

Abstract: Chemistry is confronted with the pressing issues of depleting non-renewable fossil resources and the imperative to combat environmental pollution, which is crucial for a sustainable future. Biomass stands out as the sole organic carbon source in nature among the array of sustainable resources available, positioning it as a prime substitute for fossil-derived chemicals and fuels. Extensive research has been conducted on the abundant lignocelluloses as a potential source for biofuels, bioenergy, and various valuable products, wherein, the incorporation of various processes in biomass fractionation to separate biopolymers (such as lignin, cellulose, and hemicellulose) has the potential to enhance the overall value of the process. However, industrial demonstration of biomass utilization for commercial products has been limited due to the challenges posed by the recalcitrance and complexity of biomass. Therefore, there is a need for efficient reaction processes to enable the production of bio-chemicals and fuels from renewable lignocellulose. This review focuses on the latest chemical methods developed for producing value-added chemicals from biomass-derived cellulose as a renewable feedstock.

Assessing the aerobic/anoxic enrichment efficiency at different C/N ratios: pilot scale polyhydroxyalkanoates production from waste activated sludge

Polyhydroxyalkanoates (PHA) can be produced using fermentation products of an excess sewage sludge fermentation process. An efficient method to enrich a PHA-producing community is an aerobic-feast/anoxic-famine enrichment strategy. The effect of different carbon to nitrogen (C/N) feed ratios of 1, 2 and 3.5 g COD/g N on the process performance was studied. The study was executed on a pilot plant scale using fermented waste activated sludge as the organic carbon source. The system's performance was monitored in terms of removing contaminants, producing PHA, and reducing N2O emissions. The results indicated that a lower C/N ratio results in lower PHA production, with PHA content in the sludge of 20, 24 and 36 % w/w for C/N ratios of 1, 2 and 3.5 g COD/g N, respectively. At the lowest C/N ratio, the highest nitrite accumulation rate (77%), nitrification efficiency (89%) and denitrification efficiency (89%) were observed, but the N2O production was also the highest (0.77 mg N2O-N/L). The long-term comprehensive monitoring carried out in this study revealed high carbon and ammonia removal efficiencies (never below 80%) despite the C/N shifts and high COD and ammonia concentrations. At the same time, the system showed relatively low PHA production and high environmental impact in terms of high gaseous N2O emission. These findings question the sustainability of the aerobic-feast/anoxic-famine enrichment strategy for PHA production in full-scale plants.

Resolving the Intricate Effects of Multiple Global Change Drivers on Root Litter Decomposition.

Plant roots represent about a quarter of global plant biomass and constitute a primary source of soil organic carbon (C). Yet, considerable uncertainty persists regarding root litter decomposition and their responses to global change factors (GCFs). Much of this uncertainty stems from a limited understanding of the multifactorial effects of GCFs and it remains unclear how these effects are mediated by litter quality, soil conditions and microbial functionality. Using complementary field decomposition and laboratory incubation approaches, we assessed the relative controls of GCF-mediated changes in root litter traits and soil and microbial properties on fine-root decomposition under warming, nitrogen (N) enrichment, and precipitation alteration. We found that warming and N enrichment accelerated fine-root decomposition by over 10%, and their combination showed an additive effect, while precipitation reduction suppressed decomposition overall by 12%, with the suppressive effect being most significant under warming-alone and N enrichment-alone conditions. Significantly, changes in litter quality played a dominant role and accelerated fine-root decomposition by 15% ~ 18% under warming and N enrichment, while changes in soil and microbial properties were predominant and reduced decomposition by 7% ~ 10% under precipitation reduction and the combined warming and N enrichment. Examining only the decomposition environment or litter properties in isolation can distort global change effects on root decomposition, underestimating precipitation reduction impacts by 38% and overstating warming and N effects by up to 73%. These findings highlight that the net impact of GCFs on root litter decomposition hinges on the interplay between GCF-modulated root decomposability and decomposition environment, as well as on the synergistic or antagonistic relationships among GCFs themselves. Our study emphasizes that integrating the legacy effects of multiple GCFs on root traits, soil conditions and microbial functionality would improve our prediction of C and nutrient cycling under interactive global change scenarios.