Carbon Molecular Sieving Membranes Derived from Lignin-Based Materials

Carbon molecular sieving membranes were prepared by pyrolysis of lignocresol derived from lignin by the phase-separation method. Lignocresol membranes formed by a dip process on a porous -alumina tubing were carbonized at 400–800°C under nitrogen atmosphere. The thickness of the membrane formed on the outer surface of the substrate was about 400 nm judging from SEM observation. Gas-evolving behavior of lignocresol was measured using thermogravimetry-mass spectrometry (TG-MS). The gaseous products evolved from lignocresol included a number of fragments with higher molecular weights; whereas those from phenolic resin are mainly due to phenol and methylphenol. These evolved pyrolysis fragments effectively contribute to micropore formation of carbonized lignocresol membranes. Gas permeation rates through the membrane decreased in the order of increasing kinetic molecular diameter of the penetrant gas, and the membrane behaved like a molecular sieve. The permeation properties were dependent on heating conditions, and a pyrolysis temperature of 600°C gave the best membrane performance. Gas selectivities of the membrane prepared at 600°C were 50, 8, 290, and 87 for CO₂/N₂, O₂/N₂, H₂/CH₄, and CO₂/CH₄ at 35°C, respectively.     

Degradation of microcystins using immobilized microorganism isolated in an eutrophic lake

The final purpose of our series of studies is to establish a biological removal method of cyanobacteria and their toxic products using immobilized microorganisms that can lyse cyanobacteria and decompose microcystins. To establish the biological removal method in non-point areas and water purification plants, as the first step, we explored bacteria active against the cyanobacterial hepatotoxin microcystin in the present study. Eleven active bacteria were isolated from samples taken from Lakes Tsukui and Sagami, Japan. Among 3 strains (B-9 to B-11) with degradative activity, strain B-9 exhibited the strongest activity. The 16S rDNA sequence of the strain B-9 showed the highest similarity to that of Sphingomonas sp. Y2 (AB084247, 99% similarity). Microcystins-RR and -LR were completely degraded by strain B-9 (SC16) within 1d, which led to an immobilized microorganism with a polyester resin. The degradation of microcystin-RR in a bioreactor using the immobilized strain B-9 was observed and microcystin-RR (> 90%) was completely degraded after 24 h. Microcystin-RR was added to the lake water at regular intervals and the degradation after 24 h was observed in the bioreactor over a 72-d period. An over 80% removal efficiency continued for 2 months, showing that the life of the immobilized B-9 in terms of activity was at least 2 months under the optimized conditions. From these results, this immobilized B-9 is feasible for the practical treatment of microcystins in non-point areas and water purification plants.     

Stable C and N isotope analysis elucidated the importance of zooplankton in a tropical seagrass bed of Santiago Island,Northwestern Philippines

The role of zooplankton in a tropical seagrass ecosystem was investigated in milkfish farms pollution-impacted and -unimpacted seagrass beds in Santiago Island coral reefs, Northwestern Philippines. The aim was to compare between the two sites: (1) abiotic factors and zooplankton community parameters, and (2) the trophic structure using C and N stable isotopes. Low water (98–119?mV) and sediment (–121 to ?138?mV) Oxidation Reduction Potential values indicated a reducing environment in the impacted site. Zooplankton in the impacted site showed the typical community response to eutrophication (low diversity, but high total abundance due to the dominance of the cyclopoid copepod Oithona oculata), generally few elevated δ¹⁵N values, but a significant shift towards depleted ¹³C due to the organic enrichment of fish-farm feeds. Apart from suggesting a highly complex food web with POM and zooplankton as main food sources in the unimpacted site, the Bayesian mixing model simulation generated reduced complexity in feeding interactions between basal sources, zooplankton, and fish including adults of a key fish species, Siganus fuscescens, in the impacted sites. In this study, C and N stable isotope analysis has clarified the importance of zooplankton as fish prey in a seagrass bed food web.     

Decomposition reactions of epoxy resin and polyetheretherketone resin in sub- and supercritical water

Epoxy resin and polyetheretherketone (PEEK) resin were decomposed into their monomers such as phenol, cresols, and their analogues by thermal treatment in sub- and supercritical water in a 10-ml tubing bomb reactor. The addition of basic compounds such as Na₂CO₃ was effective in promoting the decomposition reaction of the resins. In the reaction of epoxy resin, the yield of identified products reached 10% for the reaction at 703K over 1h. In the reaction of PEEK resin, the total yield of phenol and dibenzofuran reached 88% for the reaction at 703K over 3h. Chemical participation of water in the decomposition reaction was confirmed by the reaction of dinaphthylether.     

Methane and CO2 fluxes from an Indonesian peatland used for sago palm (Metroxylon sagu Rottb.) cultivation: Effects of fertilizer and groundwater level management

Tropical peatland is a vast potential land source for biological production, but peatland is a major natural source of greenhouse gases, especially methane (CH₄). It is important to evaluate the changes in greenhouse gas emissions induced by cultivation practices for sustainable agricultural use of tropical peatland. We investigated the effects of fertilizer application and the groundwater level on CH₄ and carbon dioxide (CO₂) fluxes in an Indonesian peat soil. The crop cultivated was sago palm (Metroxylon sagu Rottb.), which can grow on tropical peat soil without drainage and yield great amounts of starch. CH₄ emission through sago palm plants was first estimated by collecting gas samples immediately after cutting sago suckers using the closed chamber method. The CH₄ fluxes ranged from negative values to 1.0 mg C m⁻² h⁻¹. The mean CH₄ flux from treatment with macroelements (N, P, and K) and microelements (B, Cu, Fe, and Zn) applied at normal rates did not differ significantly from that of the No fertilizer treatment, although increasing the application rates of macroelements or microelements by 10-fold increased the CH₄ flux by a factor of two or three. The relationship between CH₄ flux and the groundwater table was regressed to a logarithmic equation, which indicated that to maintain a small CH₄ flux, the groundwater table should be maintained at <−45 cm. The CO₂ fluxes ranged between 24 and 150 mg C m⁻² h⁻¹, and were not significantly affected by either fertilizer treatments or the groundwater level. The inclusion of sago palm suckers in a chamber increased CH₄ emission from the peat soil significantly. Thus, gas emissions mediated by certain kinds of palm plants should not be disregarded.     

Eco-balance analysis of land use combinations to minimize environmental impacts and maximize farm income in northern Japan

Relationships among global warming potential (GWP), farmland surplus nitrogen (FSN) and income for major land uses in the Ikushunbetsu watershed were compared using the eco-balance method. An empirical model was created for carbon dioxide, methane and nitrous oxide for both uplands and paddy rice using monitoring data from 22 fields. The greenhouse gas emissions were converted into GWP, whereas yield and FSN were obtained from interviews with farmers and a literature survey. Land use distribution was obtained by ground surveys in 2002, 2005 and 2007. The analysis showed that paddy rice and soybeans were characterized by a high GWP, low FSN and high income, whereas onions and vegetables had a high FSN but low GWP and moderate income. Wheat showed a negative GWP in some years, and abandoned areas always exhibited negative values. The total GWPs for the region were 14,184, 11,085 and 8,337 Mg CO₂ year⁻¹ for 2002, 2005 and 2007, respectively. The contribution of paddy rice to GWP was highest, ranging from 40 to 75%. To find optimal land use combinations that provide higher incomes and lower GWPs and FSNs than at present, all possible land use combinations were analyzed by changing the land use proportion from 0 to 100% at an interval of 10%. The number of land use combinations meeting the requirements in the three investigated years was 205. Abandoned area, which had the smallest environmental load, was included in every land use combination, indicating that land uses with low environmental impacts should be maintained at a certain proportion to mitigate the environmental load accompanying land uses with high production.     

Episodic release of methane bubbles from peatland during spring thaw

Methane (CH(4)) flux into the atmosphere during spring thaw was investigated in a small ombrotrophic peatland (141 degrees 48'E, 43 degrees 19'N, Japan) using the conventional chamber method. More than 50 chamber deployments on top of the snow cover were carried out and continued for more than 165h until the surface snow and underlying ice cover on top of the peat layer had thawed completely. Methane emissions were almost absent in the presence of snow cover. At the very moment the surface ice cover thawed, a large CH(4) flush (>10mgCH(4)m(-2)h(-1)) was recorded, which was on the same order of magnitude as episodic ebullition previously observed in the high-summer. Gas bubbles trapped in the ice layer on top of the waterlogged peat were preliminarily analyzed for the volumetric percentage in the total ice volume and their gas species compositions. Results showed that the bubbles occupied about 3.2% volume and that the mixing ratio of CH(4) in the bubbles was about 20%. The abundance of the bubble-form CH(4) was sufficient to explain the observed episodic CH(4) release during the thaw. Results of this study show that CH(4) emissions during the thaw season have great temporal variability; emission occurs as an episodic release of bubble-form CH(4) stored in the frozen layer. The results also imply the possibility that gas-phase CH(4) plays an important role, not only during the growing season but also in cold-season CH(4) dynamics in northern peatlands.     

Measurement of ammonia volatilization from a field,in upland Japan,spread with cattle slurry

Ammonia volatilization from livestock manure is one of the most important pathways of nitrogen loss from agricultural cultivated fields. In this paper, we report the measurement of ammonia emission from cattle slurry manure applied to upland in Miyazaki, Japan. It has been determined that after the cattle slurry was sprayed on the upland surface, the emission flux of the first day was 110 microg N ha(-1) s(-1). The loss of NH4(+) -N in the applied slurry was 60% after 5 days following the spraying of cattle slurry.     

Enzymatic Degradation and Aminolysis of Microbial Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) Single Crystals

Solution-grown single crystals of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] were hydrolyzed by polyhydroxybutyrate (PHB) depolymerase from Ralstonia pickettii T1. Enzymatic degradation proceeded from the edges of lamellar crystals, yielding serrated contour and small crystal fragments. Gel permeation chromatography analysis revealed that the molecular weights of the crystals decreased during enzymatic degradation, suggesting that the enzymatic hydrolysis of chain-folding regions at the crystal surfaces occurred in addition to the enzymatic degradation at crystal laterals or edges. After P(3HB-co-4HB) single crystals were aminolysed in 20% aqueous methylamine solution to remove the folded-chain regions and enzymatic degradation by lipase from Rhizopus oryzae to remove 4HB components at crystal surfaces of single crystal aminolyzed, it was found that a small amount (up to ca. 2 mol%) of 4HB component can be incorporated into the P(3HB) mother crystal lattice irrespective of the 4HB content.