Carbon Mass Balance Research Articles

Seasonal variability in concentration, composition, age, and fluxes of particulate organic carbon exchanged between the floodplain and Amazon River

The composition, sources, and age of particulate organic matter were determined in an Amazonian river‐floodplain system during rising, high, falling, and low water periods over 7 yr (1999–2006), and a mass balance for total organic carbon (dissolved and particulate) was estimated. The Curuai floodplain, composed of several temporally interconnected lakes, is permanently connected to the Amazon River via channels. Organic matter (OM) is imported to the floodplain from the Amazon River mainly during the rising water period and produced in the floodplain and exported to the river during high and falling water periods. No significant exchanges occurred during low water periods. The OM produced in the floodplain is characterized by low C/N ratios and by high chlorophyll a concentrations (Chl‐a). The δ13C signature has a seasonal trend, with more negative δ13C values during the high water period than other periods. Δ14C results indicate that the bulk OM present in floodplain lakes is predominantly post‐bomb (i.e., post‐1950). Particulate organic carbon (POC) and dissolved organic carbon (DOC) fluxes exported by the Curuai floodplain represent 1.3% and 0.1%, respectively, of the POC and DOC annual fluxes in the mainstem Amazon River at Óbidos but may reach up to 3.3% and 0.8% during falling water. Based on Δ14C, δ13C, Chl‐a, and elemental analysis of the particulate organic matter, we demonstrate that floodplain lakes have intense phytoplankton and macrophyte primary production, which is partly exported to the main river channel. Floodplains are thus a significant source of modern and labile organic carbon to the river mainstem, where it can be rapidly degraded and recycled back to the atmosphere.

Biodegradation of 4-nitrotoluene with biosurfactant production by Rhodococcus pyridinivorans NT2: metabolic pathway, cell surface properties and toxicological characterization

A novel 4-nitrotoluene-degrading bacterial strain was isolated from pesticides contaminated effluent-sediment and identified as Rhodococcus pyridinivorans NT2 based on morphological and biochemical properties and 16S rDNA sequencing. The strain NT2 degraded 4-NT (400mgl(-1)) with rapid growth at the end of 120h, reduced surface tension of the media from 71 to 29mNm(-1) and produced glycolipidic biosurfactants (45mgl(-1)). The biosurfactant was purified and characterized as trehalose lipids. The biosurfactant was stable in high salinity (10% w/v NaCl), elevated temperatures (120°C for 15min) and a wide pH range (2.0-10.0). The noticeable changes during biodegradation were decreased hydrophobicity; an increase in degree of fatty acid saturation, saturated/unsaturated ratio and cyclopropane fatty acid. Biodegradation of 4-NT was accompanied by the accumulation of ammonium (NH4 (+)) and negligible amount of nitrite ion (NO2 (-)). Product stoichiometry showed a carbon (C) and nitrogen (N) mass balance of 37 and 35%, respectively. Biodegradation of 4-NT proceeded by oxidation at the methyl group to form 4-nitrobenzoate, followed by reduction and hydrolytic deamination yielding protocatechuate, which was metabolized through β-ketoadipate pathway. In vitro and in vivo acute toxicity assays in adult rat (Rattus norvegicus) showed sequential detoxification and the order of toxicity was 4-NT >4-nitrobenzyl alcohol >4-nitrobenzaldehyde >4-nitrobenzoate >> protocatechuate. Taken together, the strain NT2 could be used as a potential bioaugmentation candidate for the bioremediation of contaminated sites.

The application of inelastic neutron scattering to investigate the ‘dry’ reforming of methane over an alumina-supported nickel catalyst operating under conditions where filamentous carbon formation is prevalent

The use of CO2 in reforming methane to produce the industrial feedstock syngas is an economically and environmentally attractive reaction. An alumina-supported nickel catalyst active for this reaction additionally forms filamentous carbon. The catalyst is investigated by inelastic neutron scattering as well as elemental analysis, temperature-programmed oxidation, temperature-programmed hydrogenation, X-ray diffraction, transmission electron microscopy and Raman scattering. Isotopic substitution experiments, using 13CO2 for 12CO2, show the oxidant to contribute to the carbon retention evident with this sample. At steady-state operation, a carbon mass balance of 95% is observed. A kinetic scheme is proposed to account for the trends observed.

The quantification of methane formation in Amazon Fan sediments (ODP Leg 155, Site 938) by hydrogeochemical modeling solid – Aqueous solution – Gas interactions

A quantitative simulation of interdependent diagenetic reactions in deep-sea fan sediments is presented. The model scenario describes a growing sediment column and reproduces observed diagenetic signals (distribution of dissolved, mineral, and gaseous species) and predicts the amount of in situ-generated biogenic dissolved methane and methane hydrate at ODP Leg 155, Site 938 (Amazon Fan). The approach relies on thermodynamic calculations of equilibrium reactions in aqueous solutions that are constrained by the irreversible remineralization of organic carbon. Sediments of ODP Leg 155, Site 938 are located within the gas hydrate stability zone. Methanogenesis starts at a shallow depth (10 m below seafloor). The modeled amount of in situ-generated biogenic methane exceeds the solubility of the methane, with respect to methane hydrate in a depth of 115 mbsf. Moreover, anaerobic oxidation of methane (AOM) prevents the diffusion of dissolved methane to the overlying seawater. Dissolved methane and methane hydrate are stored within the sediment column.Authigenic carbonate is the most important carbon sink in the investigated sediments of the Amazon fan. Carbon mass balance calculations reveal the studied Amazon Fan sediments are a net carbon sink. Authigenic siderite precipitation, triggered by AOM, explains the overall gain in carbon within the Amazon fan sediments. Generated methane (as methane gas, hydrate and dissolved methane) is the second most important carbon species found within the sediments. This highlights the significance of organic matter-rich high accumulation areas to biogenic methane formation and storage, and the significance of these areas as possible targets for exploration.

Air emissions from organic soil burning on the coastal plain of North Carolina

Emissions of trace gases and particles ≤2.5 microns aerodynamic diameter (PM2.5) from fires during 2008–2011 on the North Carolina coastal plain were collected and analyzed. Carbon mass balance techniques were used to quantify emission factors (EFs). PM2.5 EFs were at least a factor of 2 greater than those from forest burning of above-ground fuels because of extended smoldering combustion of organic soil layers and peat fuels. This is consistent with CO2 EFs at the low end of previously reported ranges for biomass fuels, indicating less efficient combustion and enhanced emissions of products of incomplete combustion (PICs). CO EFs are at the high end of the range of previously published EFs for smoldering fuels. The biomass burning tracer levoglucosan was found to compose 1–3 percent of PM2.5 from the organic soil fires, similar to fractions measured in smoke from above-ground fine fuels reported in previous studies. Organic soil fuel loads and consumption are very difficult to estimate, but are potentially as high as thousands of tonnes ha−1. Combined with higher emission factors, this can result in emission fluxes hundreds of times higher than from prescribed fires in above-ground fuels in the southeastern US. Organic soil fuel represents a source of particles and gases that is difficult to control and can persist for days to months, jeopardizing human health and incurring considerable costs to monitor and manage. Extended fires in organic soils can contribute substantially to PM2.5 on CO emission inventories and may not be adequately accounted for in current estimates.

Catalytic dechlorination of 2,4-dichlorophenol by Ni/Fe nanoparticles in the presence of humic acid: intermediate products and some experimental parameters

The catalytic dechlorination of 2,4-dichlorophenol (2,4-DCP) by Ni/Fe bimetallic nanoparticles in the presence of humic acid (HA) was investigated in order to understand their applicability for in situ remediation of groundwater. 2,4-DCP was catalytically dechlorinated to form the final products – phenol (P) via two intermediates, o-chlorophenol (o-CP) and p-chlorophenol (p-CP). It was demonstrated that the carbon mass balances during the dechlorination were between 84% and 92%, and other carbons were adsorbed on the surface of Ni/Fe bimetallic nanoparticles. The experimental results suggest that HA competed for reaction sites on the Ni/Fe bimetallic nanoparticles with 2,4-DCP, and thus reduced the efficiency and rate of the dechlorination of 2,4-DCP. The catalytic degradation slowed down as the increase of HA in solution, and when HA's concentrations were 0, 10, 20 and 30 mg L−1, the maximum concentrations of o-CP were 0.025, 0.041, 0.039 and 0.034 mM in 10, 30, 30 and 30 min, respectively. High Ni content, low initial pH value, high Ni/Fe nanoparticles’ dosage and high temperature favoured the catalytic dechlorination of 2,4-DCP. The experimental results show that no other intermediates were generated besides Cl−, o-CP, p-CP and P during the catalytic dechlorination of 2,4-DCP.

Enrichment in <sup>13</sup>C of atmospheric CH<sub>4</sub> during the Younger Dryas termination

Abstract. The abrupt warming across the Younger Dryas termination (~11 600 yr before present) was marked by a large increase in the global atmospheric methane mixing ratio. The debate over sources responsible for the rise in methane centers on the roles of global wetlands, marine gas hydrates, and thermokarst lakes. We present a new, higher-precision methane stable carbon isotope ratio (δ13CH4) dataset from ice sampled at Påkitsoq, Greenland that shows distinct 13C-enrichment associated with this rise. We investigate the validity of this finding in face of known anomalous methane concentrations that occur at Påkitsoq. Comparison with previously published datasets to determine the robustness of our results indicates a similar trend in ice from both an Antarctic ice core and previously published Påkitsoq data measured using four different extraction and analytical techniques. The δ13CH4 trend suggests that 13C-enriched CH4 sources played an important role in the concentration increase. In a first attempt at quantifying the various contributions from our data, we apply a methane triple mass balance of stable carbon and hydrogen isotope ratios and radiocarbon. The mass balance results suggest biomass burning (42–66% of total methane flux increase) and thermokarst lakes (27–59%) as the dominant contributing sources. Given the high uncertainty and low temporal resolution of the 14CH4 dataset used in the triple mass balance, we also performed a mass balance test using just δ13C and δD. These results further support biomass burning as a dominant source, but do not allow distinguishing of thermokarst lake contributions from boreal wetlands, aerobic plant methane, or termites. Our results in both mass balance tests do not suggest as large a role for tropical wetlands or marine gas hydrates as commonly proposed.

Carbon and nitrogen mass balance during flue gas treatment with Dunaliella salina cultures

The biotreatment of flue gases with algae cultures is a promising option to sequestrate CO2, yet the emission of other greenhouse gases (GHG) from the cultures can hamper their environmental benefit. Quantitative data on the sequestration potential for CO2 and NO (x) in relation to the direct production of CH4 and N2O are urgently required. The present study assessed the flows of carbon (C) and nitrogen (N) through cultures of the green alga Dunaliella salina, supplied with biodiesel flue gas, by means of mass balancing. D. salina was grown in artificially lighted, field- (42-L bubble column reactor) and laboratory-scale cultures (23 A degrees C, pH 7.5). In the bubble column reactor, algae grew with an average specific growth rate of 0.237 day(-1) under flue gas supplementation (6.3 % (v/v) CO2, 1.2 ppmv NO (x) ), and CO2 was retained to 39 % in the system. The specific sequestration rate for CO2 was low, with 0.13 g CO2 L-1 day(-1). Cultures emitted up to 13.03 mu g CH4 L-1 day(-1) and 4261 mu g N2O L-1 day(-1). The moderate retention of NO (x) -N was outweighed by emissions of N2O-N, and total N in the system decreased by 15.48 % during the 9-day trial. Results suggest that GHG production was mainly the outcome of anaerobic microbial processes and their emission was lower in pre-sterilized cultures. Under the tested conditions, up to six times more CO2 equivalents were emitted during flue gas treatment. Therefore, the direct GHG emissions of algae culture systems, intended for flue gas treatment (i.e. open ponds) need to be reviewed critically.

Geologic CO2 input into groundwater and the atmosphere, Soda Springs, ID, USA

A set of CO2 flux, geochemical, and hydrologic measurement techniques was used to characterize the source of and quantify gaseous and dissolved CO2 discharges from the area of Soda Springs, southeastern Idaho. An eddy covariance system was deployed for ~one month near a bubbling spring and measured net CO2 fluxes from −74 to 1147gm−2 d−1. An inversion of measured eddy covariance CO2 fluxes and corresponding modeled source weight functions mapped the surface CO2 flux distribution within and quantified CO2 emission rate (24.9t d−1) from a 0.05km2 area surrounding the spring. Soil CO2 fluxes (<1 to 52,178gm−2 d−1) were measured within a 0.05km2 area of diffuse degassing using the accumulation chamber method. The estimated CO2 emission rate from this area was 49t d−1. A carbon mass balance approach was used to estimate dissolved CO2 discharges from contributing sources at nine springs and the Soda Springs geyser. Total dissolved inorganic carbon (as CO2) discharge for all sampled groundwater features was 57.1t d−1. Of this quantity, approximately 3% was derived from biogenic carbon dissolved in infiltrating groundwater, 35% was derived from carbonate mineral dissolution within the aquifer(s), and 62% was derived from deep source(s). Isotopic compositions of helium (1.74–2.37 Ra) and deeply derived carbon (δ13C≈3‰) suggested contribution of volatiles from mantle and carbonate sources. Assuming that the deeply derived CO2 discharge estimated for sampled groundwater features (~35t d−1) is representative of springs throughout the study area, the total rate of deeply derived CO2 input into the groundwater system within this area could be ~350t d−1, similar to CO2 emission rates from a number of quiescent volcanoes.

Mesophilic and thermophilic biofiltration of gaseous toluene in a long-term operation: Performance evaluation, biomass accumulation, mass balance analysis and isolation identification

A thermophilic biofilter (TBF) was developed to treat high temperature gaseous toluene (55°C). The performance of TBF was evaluated under various operating conditions, including different inlet concentrations and gas flow rates, and compared with a control mesophilic biofilter (MBF). Furthermore, the leachate, biomass accumulation and pressure drop of filter bed were investigated. The experimental results showed that the TBF achieved high performance removal efficiencies of 90% when the inlet loading was lower than 100gm−3h−1. Increasing inlet loading resulted in lower performance of TBF compared with MBF. However, the biomass in TBF, in the long-term operation, showed a slow accumulation process than MBF. The specific growth rates of microorganism were 0.0011day−1 and 0.0015day−1 for TBF and MBF, respectively. The slow growth process in TBF further resulted in a lower pressure drop of filter bed (0.1–0.5kPa) than that of MBF (7–10kPa). The leachate from TBF presented a neutral pH and presented a higher TOC contents than those from MBF. The results of three-dimensional fluorescence spectra suggested that the products of toluene biodegradation included some organic acids. A carbon mass balance analysis showed that 47.1% of the removed toluene was converted to biomass in MBF, which was higher than that of MBF with 30.5%. Finally, 16s rRNA gene sequences indicated the dominant microorganisms in the TBF including Brevibacillus sp. and Anoxybacillus sp., while Delftia sp. and Stenotrophomonas sp. in the MBF.

Carbon Mass Balance of Biohydrogen Production Process by &lt;i&gt;Clostridium&lt;/i&gt; &lt;i&gt;butyricum TISTR 1032&lt;/i&gt;: Effect of Oxygen Scavenger

A dark hydrogen fermentation process of food waste by Clostridium butyricum TISTR 1032 was examined under the condition of initial pH 6, 37oC and varied condition with oxygen scavenger in 5 L semi-batch reactors. Results showed that oxygen scavenger significantly elevated the maximum rate of hydrogen production (Rm) (203.5 mL h-1) compared to that without oxygen scavenger (30.6 mL h-1). However, it did not improve the maximum cumulative hydrogen production (Hmax). Carbon mass balance was used to explore the direction of fermentative process including toidentify type of fermentative process. Butyric acid fermentation was recognized as the fermentation type of this study under both conditions. Drop of pH and accumulation of total undissociated acid considerably reduced the hydrogen production.

Electrochemical Decoloration of Synthetic Wastewater Containing Rhodamine 6G: Behaviors and Mechanism

Dye wastewater has posed a great threat to our aqueous environment. In this study, the treatment of synthetic wastewater containing Rhodamine 6G by electrochemical technology using RuO2-coated Ti mesh as anode was investigated. The effects of solution pH, temperature, and dye auxiliaries on the performance were investigated. Carbon and nitrogen mass balance analyses, UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) were used to elucidate the working mechanism. It was found that lower solution pH and lower temperature facilitated the decoloration of the wastewater. The addition of dye auxiliaries did not significantly affect the decoloration. Under optimal condition, complete decoloration of the synthetic wastewater was obtained within 5 min, and 42.3% of the dye was mineralized. The amine and methyl groups were first detached from the dye molecule, leading to a change in the dye structure from polar into nonpolar to fo...

Anaerobic digestion of two biodegradable municipal waste streams

Landfill avoidance for organic wastes is now a high priority worldwide. Two fractions of the municipal waste stream were considered with respect to their potential for diversion through controlled anaerobic digestion. The physical and chemical properties of source segregated domestic food waste (ss-FW) and of the mechanically-recovered organic fraction of municipal solid waste (mr-OFMSW) were analysed, and their methane yields determined in both batch and semi-continuous digestion. Methane potentials were compared with predicted values based on biochemical composition, elemental analysis and carbon mass balance, and the differences explained by compositional analysis of feedstocks and digestates. The ss-FW had a higher percentage biodegradability and higher energy potential on a dry weight basis due to the high proportion of proteins and fats in this waste, although the energy potential of the mr-OFMSW was slightly higher on a wet weight (WW) basis. The mr-OFMSW showed very stable digestion characteristics, whereas the ss-FW had a high digestate ammoniacal-N concentration and volatile fatty acid accumulation leading to some process instability. Digestates from semi-continuous trials with mr-OFMSW had high concentrations of potentially toxic elements (PTE) and a lower nutrient content than ss-FW digestate, making the former unsuitable for application to land used in food production.

Efficacy of a denitrification wall to treat continuously high nitrate loads

Denitrification walls have been proven as an effective, long-term method for remediating nitrogen in groundwater underneath agricultural lands. Utilizing walls to provide large N load reductions requires targeting a significant portion of agricultural effluent. One approach for more efficient application of walls is to locate them adjacent to zones with high groundwater flow, although treatment efficacy in these conditions is uncertain. In this study, a large wall (168m3) receiving high N loads was assessed using a well transect array for hydraulic and water quality evaluations and media were collected from within the wall to evaluate enzyme activity with flow distance. Porewater velocity through the wall was rapid (1.7mday−1) with short detention times (1.7–1.9 days), yet the wall treated 100±28m3 of groundwater per day, effectively removing 228±155kg of total N per year. Maximum nitrate-N removal rates per media volume (4.9–5.5g-Nm−3d−1) were at the upper end of published values. Rapid reduction of potential denitrification rates in media samples from 4.89gNm−3d−1 to undetectable within a quarter of the wall length suggests that nitrate-N depletion drove a rapid reduction in denitrifying enzymes. Based on a carbon mass balance, dissolved organic C leaching was initially the largest C export process and the longevity of total bioavailable C was estimated as 23±5.9 years. These results indicate the ability of walls to reduce high N-loads over long timespans.

Hydrogeochemistry of Alpine springs from North Slovenia: Insights from stable isotopes

Spring water chemistry and carbon cycling in our study mainly depend on geological composition of the aquifer. The investigated Alpine springs in Slovenia represent waters strongly influenced by chemical weathering of Mesozoic limestone and dolomite, only one spring was located in Permo-Carboniferous shales. The carbon isotopic composition of dissolved inorganic carbon (DIC) and suspended organic carbon (POC) as well as major solute concentrations yielded insights into the origin of carbon in Alpine spring waters. The major solute composition was dominated by carbonic acid dissolution of calcite. Waters were generally close to saturation with respect to calcite, and dissolved CO2 was up to fortyfold supersaturated relative to the atmosphere. δ13C of DIC indicates the portion of soil CO2 contributed in water and is related with soil thickness of infiltrating water in aquifer and could be therefore used as a tool for vulnerability assessment. The δ13C of DIC ranged from −15.8‰ to −1.5‰ and indicated less and more vulnerable aquifers. Mass balances of carbon for spring waters draining carbonate rocks suggest that carbonate dissolution contributes from approximately 49% to 86% and degradation of organic matter from 13.7% to 51.4%, depending on spring and its relation with rock type, soil environment, and geomorphic position. Stable oxygen isotope composition of water (δ18OH2O), and tritium values range from −12.2 to −9.3‰ and from 6.4 to 9.8 TU, respectively and indicate recharge from modern precipitation. According to active decay of tritium and tritium in modern precipitation the age of spring waters are estimated to be about 2.6years for springs located in Julian Alps, about 5years for springs located in Karavanke and about 5years for springs located in Kamniško–Savinjske Alps.

Simulation of the Anaerobic Digestion of Microwave Pre-Treated Waste Activated Sludge with ADM1

AbstractThe disposal of sludge originating from municipal waste water treatment is a major issue and represents up to 50% of the operating costs of wastewater treatment plants (WWTP). (Appels et al., 2008) This sludge, a by-product of the treatment processes, however, has the potential to be converted into an energy rich biogas, i.e. a mixture of ca. 65% CH4 and 35% CO2, which can be utilized for the sustainable production of heat and/or electricity. Various pre-treatment methods have been suggested in literature for improving the solids reduction and biogas production rate by enhancing the digestion's rate limiting step, i.e. organic matter hydrolysis. They all induce the solubilization of complex particulate matter so this is more rapidly and completely consumed during the anaerobic digestion process. Methods that have been shown to have a positive effect on anaerobic digestion include chemical, mechanical, biological and thermal processes. Microwave disintegration is one of the more recently applied pre-treatment methods. The disintegration is caused by the combination of thermal and athermal effects and may hence provide superior results compared to a heat treatment (Eskicioglu et al., 2007).The application of mathematical models for the optimization of the digestion process is widely acknowledged. Due to the complexity of the microbial process, accurate modelling of anaerobic digestion is, however, a daunting task. A major stride countering this problem was achieved by the development of the Anaerobic Digestion Model no 1 (ADM1) by the corresponding IWA task group (Batstone et al. 2002). This model is ever since, considered to be the state of the art in modelling of anaerobic digestion and has been the platform for further refinements and numerous applications (Batstone et al. 2006).The main aim of this work is to investigate the ability of ADM1 to describe anaerobic digestion of microwave pre-treated sludge. Compared to untreated sludge, the composition and structure of the sludge is changed dramatically due to the treatment. The recorded data and digester performances were compared with the results of a modelling in ADM1 (Batstone et al., 2002). Practically, the ADM1 implementation as described by Rosen & Jeppsson (Rosen and Jeppsson (2005)) is chosen as it effectively completes the mass balance for COD, carbon and nitrogen.

Waste stabilization mechanism by a recirculatory semi-aerobic landfill with the aeration system

The main purpose of this research is to clarify and compare the mechanism of waste stabilization by a recirculatory semi-aerobic landfill with the aeration system. Our research is proposing the semi-aerobic landfill system for developing countries because of the simple and low-cost technology for the final disposal. Moreover, this system with leachate recirculation can be a more effective system for waste stabilization because of the improvement of leachate quality as an organic pollutant and, also, nitrogen removal. In this research, five different systems of landfill (Ae: aerobic, An: anaerobic, Se: semi-aerobic, SeR: recirculatory semi-aerobic landfill, and SeRA: recirculatory semi-aerobic landfill with aeration system) are compared with lysimeters which are 1 m high with a diameter of 0.3 m. The results of the leachate quality shows that the leachate treatment effect of the SeRA system can be observed to be as high as the Ae system. To determine the mechanism of this process, all lysimeters are dismantled after 1,100 days in the experimental period and the waste composition, the dissolution test, the mass balance of carbon and nitrogen, the determination of bacterial counts, etc., were analyzed. In this research, it was proven that the SeRA system has an optimal leachate treatment effect that is the same as the Ae system. And, from the results of the mass balance of carbon and nitrogen, the SeR and SeRA systems show higher waste stabilization effectiveness and nitrogen removal than the other systems. Moreover, the number of the aerobic bacteria can be observed to be higher in the SeR and SeRA systems. To determine these results, the waste stabilization mechanism is considered by the results of leachate quality, the mass balance of carbon and nitrogen, and, also, the bacterial numbers.

Effects of influent C/N ratios on CO 2 and CH 4 emissions from vertical subsurface flow constructed wetlands treating synthetic municipal wastewater

Greenhouse gases (GHG) emissions from constructed wetlands (CWs) can mitigate the environmental benefits of nutrient removal because reduced water pollution could be replaced by emission of GHG. Therefore, the GHG (CO 2 and CH 4) fluxes of vertical subsurface flow constructed wetlands (VSSF CWs) under different influent C/N ratios of synthetic municipal wastewater were analyzed directly by GHG flux measurements, and estimated by carbon mass balance (CMB) over a 12 month period. The VSSF CWs system achieved the highest biological nutrient removal (BNR) efficiency between C/N ratios of 5:1 and 10:1 across all kinds of pollutants. Variation in influent C/N ratios dramatically influenced GHG fluxes from the VSSF CWs system. The GHG flux measured in situ agreed with those predicted by the CMB model and represented relatively low GHG fluxes when C/N ratios were between 2.5:1 and 5:1. It was determined that the optimum C/N ratio is 5:1, at which VSSF CWs can achieve a relatively high BNR efficiency and a low level of GHG flux.

Growth condition study of algae function in ecosystem for CO 2 bio-fixation

Algae niche play a crucial role on carbon cycle and have great potential for CO 2 sequestration. This study was to investigate the CO 2 bio-fixation by the high rate pond (HRP) to mimic the algae function of nature. All the reactors can keep CO 2 consumption efficiencies over 100%. The statistical analyses proved HRPs were close to the natural system from all the growth conditions. The HRP could show the “natural optimization as nature” to perform as well as the artificial reactor of continuously stirred tank reactor (CSTR). In the nutrition study, the carbon mass balance indicated CO 2 was the main carbon source. Accordingly, the HRPs can keep a neutral pH range to provide dissolved oxygen (DO), to promote total nitrogen (TN)/total phosphorous (TP) removal efficiencies and to demonstrate self-purification process. Furthermore, the observations of different nitrogen species in the reactors demonstrated that the major nitrogen source was decided by pH. This finding logically explained the complex nitrogen uptake by algae in nature. Consequently, this study took advantage of HRP to explore the processes of efficient CO 2 uptake with the corresponding growth condition in the ecosystem. Those results contributed the further understanding of the role of CO 2 bio-fixation in nature and demonstrated HRP could be a potential ecological engineering alternative.

In Situ Kinetic Study on Hydrothermal Transformation ofd-Glucose into 5-Hydroxymethylfurfural throughd-Fructose with13C NMR

Kinetics of hydrothermal reaction of D-glucose was investigated at 0.02 M over a temperature range of 120-160 °C by applying in situ (13)C NMR spectroscopy. D-Glucose was found to be reversibly transformed first into D-fructose (intermediate) and successively into 5-hydroxymethylfurfural (5-HMF) through dehydration. The carbon mass balance has been kept within the detection limit, and no other reaction pathways are present. The hydrothermal reaction of d-glucose is thus understood as that of D-fructose in the sense that the D-glucose reaction proceeds only through D-fructose. All the isomers of D-glucose and D-fructose were detected by the in situ (13)C NMR in D(2)O: they are the open chains and the pyranoses and furanoses of α- and β-types. The β-forms are the most stable due to the hydration. For both D-glucose and D-fructose, the isomers are in a rapid equilibrium for each monosaccharide, and they are treated collectively in the kinetic analysis of the slower hydrothermal reactions. The reactions are of the first order with respect to the concentrations of D-glucose and D-fructose, and D-glucose converts to 5-HMF on the order of hours. The kinetic parameters were determined by the in situ method.