Initial Decomposition Rate Research Articles

Lodgepole Pine Bole Wood Density and Decay Rate 1, 11, and 22 Years After Felling in Central Montana, United States

Estimates of dead and down woody material (DWM) biomass are important for nutrient cycling, wildlife habitat assessment, fire effects and climate change science. Most methods used to sample woody material initially assess volume then estimates of wood density are used to convert volume to biomass. To assess initial wood density and decomposition rate, this study examined in situ wood density of lodgepole pine logs at the Tenderfoot Creek Experimental Forest (TCEF), central Montana, United States, 1, 11, and 22 years after felling. Mean wood density decreased from 0.39 to 0.27 g cm–3 over 22 years and the single exponential decay rate was k = 0.012 yr–1 1 and 11-years post-felling and 0.022 yr–1 11 and 22 years post-felling. A common 5-category decay classification system was evaluated for estimating wood density by decay class, which identified significant difference in three of four observed classes.

Free-Radical Polymerization of Styrene: Kinetic Study in a Spinning Disc Reactor (SDR)

Free-radical polymerization of styrene conducted in a spinning disc reactor (SDR) results in significant increases in conversion in one disc pass, equivalent to a few seconds of residence time, with little change in the number average and weight average molecular weights and polydispersity compared to a SDR feed pre-polymerized in a batch reactor. Results of our experimental studies are presented in this paper and a rationale, based on simulation studies, is offered to explain these observations. It is shown that phenomena such as large increases in conversion that do not impact on molecular weights and molecular weight distribution is a result of a simultaneous increase in both the initiator decomposition rate and the propagation rate. The increases in these rate constants, predicted by our modeling studies, provide the driving forces that characterize a polymerization process in a SDR reactor, with the centrifugal force having different degrees of influence on individual reaction steps. This is attributed to different molecular sizes being involved in each of the polymerization reaction steps. The highest impact is observed on the initiator decomposition rate constant, as this reaction step involves a small molecule. Lesser impact is observed on the propagation rate constant, as this reaction step involves interaction of one small molecule and one large reactive species, whilst no or very small effect is seen in the case of the termination rate constant as large reactive species are involved. Developed constant variance model was used to estimate reaction parameters at different temperatures (i.e., initiator efficiency f, rate constants kd, kp, and kt) from the acquired experimental data in order to estimate activation energy (Ea) and pre-exponential factor (A) in a SDR. Data analysis at various SDR operating temperatures suggested activation energy for the styrene polymerization in the SDR as 40.59 ± 1.11 kJ mol−1.

Root presence modifies the long‐term decomposition dynamics of fungal necromass and the associated microbial communities in a boreal forest

Recent studies have highlighted that dead fungal mycelium represents an important fraction of soil carbon (C) and nitrogen (N) inputs and stocks. Consequently, identifying the microbial communities and the ecological factors that govern the decomposition of fungal necromass will provide critical insight into how fungal organic matter (OM) affects forest soil C and nutrient cycles. Here, we examined the microbial communities colonising fungal necromass during a multiyear decomposition experiment in a boreal forest, which included incubation bags with different mesh sizes to manipulate both plant root and microbial decomposer group access. Necromass-associated bacterial and fungal communities were taxonomically and functionally rich throughout the 30months of incubation, with increasing abundances of oligotrophic bacteria and root-associated fungi (i.e., ectomycorrhizal, ericoid mycorrhizal and endophytic fungi) in the late stages of decomposition in the mesh bags to which they had access. Necromass-associated β-glucosidase activity was highest at 6months, while leucine aminopeptidase peptidase was highest at 18months. Based on an asymptotic decomposition model, root presence was associated with an initial faster rate of fungal necromass decomposition, but resulted in higher amounts of fungal necromass retained at later sampling times. Collectively, these results indicate that microbial community composition and enzyme activities on decomposing fungal necromass remain dynamic years after initial input, and that roots and their associated fungal symbionts result in the slowing of microbial necromass turnover with time.

Thermal Properties of Ethanol Organosolv Lignin Depending on Its Structure

In general, lignin exhibits unpredictable and nonuniform thermal properties due to the structural variations caused by the extraction processes. Therefore, a systematic understanding of the correlation between the extraction conditions, structural characteristics, and properties is indispensable for the commercial utilization of lignin. In this study, the effect of extraction conditions on the structural characteristics of ethanol organosolv lignin (EOL) was investigated by response surface methodology. The structural characteristics of EOL (molecular weight, hydroxyl content, and intramolecular coupling structure) were significantly affected by the extraction conditions (temperature, sulfuric acid concentration, and ethanol concentration). In addition, the correlation between the structural characteristics and thermal properties of the extracted EOLs was estimated. The relevant correlations between the structural characteristics and thermal properties were determined. In particular, EOLs that had a low molecular weight, high phenolic hydroxyl content, and low aryl–ether linkage content exhibited prominent thermal properties in terms of their initial decomposition rate and a high glass transition temperature, Tg. Correspondingly, EOL-PLA blends prepared using three EOL types exhibited improved thermal properties (starting point of thermal decomposition and maximum decomposition temperature) compared to neat PLA and had thermal decomposition behaviors coincident with the thermal properties of the constituent EOLs.

Litter Fall, Leaf Litter Decomposition, Soil Microfungi and Nutrient Content in Cocoa and Food Crop Agroforest Farmlands in Southeastern Ghana

This study is a comparison of the litterfall, litter decomposition and soil microfungi species diversity in cocoa and mixed food crop agroforest farmlands. The study was carried out in the Atewa and Fanteakwa districts of the Eastern region of Ghana. A total of thirty six sampled plots size of five 25 m x 25 m were randomly demarcated in cocoa agroforest, mixed food crop agrorest and the natural forest reserve. Data collected on litterfall mass and leaf litter decomposition at monthly intervals for a period five months. Soil microfungi species diversity was analyzed from soil samples collected at two depths 0-5cm and 0-10 cm respectively using pour plate method. The reduction in mass of cocoa leaf litter was significantly negatively correlated with the number of days of decomposition. The rate of release of NPK was positively correlated with litter mass. Litter mass production significantly declined in the cocoa agroforest and mixed food crop agroforest farmlands. Initial rate of litter decomposition was generally slow in the cocoa and mixed food crop farmlands than in the natural forest. Soil microfungi species diversity was high in natural forest and low in the cocoa and mixed food crop agroforest farmlands.

Benzoyl Peroxide- and Azobisisobutyronitrile-Initiated Polymerization of Acrylic Acid and Methyl Acrylate in the Temperature Range Close to Room Temperature

The kinetics and mechanism of benzoyl peroxide- and azobisisobutyronitrile-initiated polymerization of acrylic acid and methyl acrylate in the temperature range of 20–40°C have been investigated. In the case of evacuation of the monomer + initiator system, the polymerization proceeds without heating or other energetic impacts on the system. The polymer yield depends on the initiator concentration and the temperature and time of sample thermostating. It has been shown by EPR that the monomers affect the rate of initiator decomposition into radicals. The structures of intermediate complexes formed in the acrylic acid + azobisisobutyronitrile system have been determined by quantum-chemical calculations, and the activation energies of the relevant processes have been calculated.

Radical polymerization of butadiene mediated by molecular iodine: A comprehensive kinetic study on solution copolymerization with acrylonitrile

Solution homo- and copolymerization of butadiene (Bu) and acrylonitrile (AN) in 1,4-dioxane (Dox) was carried out in the presence of molecular iodine (I2) and 4,4′-azobis (4-cyanovaleric acid) (ACVA), both acting as an in situ generator of carboxyl-functionalized alkyl iodide as a chain transfer agent (CTA), to synthesize α-carboxyl ω-iodine heterotelechelic polymer architectures. Effect of various variables including solvent concentration and type, ACVA to I2 molar ratio and reaction temperature (60 and 70 °C) on the overall conversion versus time data was investigated. It was found that before complete consumption by initiator-derived radicals during the induction period, molecular I2 inhibits the reaction. Polymerization period was then started in the presence of an in situ generated CTA. From conversion versus time data, rate constant of initiator decomposition (kd), induction time (tind ) and overall average rate constant of k‾p2/k‾t were estimated and compared with those reported for conventional free-radical homo- and copolymerization of Bu and AN. A good agreement between the theoretical and experimental variations in the conversion versus time was also observed, indicating accuracy of the kinetic constants calculated in the present work. Comparison of the theoretical and experimental induction times revealed that molecular I2 reacts with Bu, resulting in butadiene diiodide species (I−Bu−I) which can act along with carboxyl-functionalized alkyl iodide as CTAs. Formation of I−Bu−I was also confirmed by 1H NMR analysis. Also, fraction of I2 consumed by Bu (i.e. [I−Bu−I]/[I2]0) was estimated from kinetic data at hand. [I−Bu−I]/[I2]0 value as high as 20.8% was observed in the case of Bu homopolymerization and decreased by increasing the AN content in the initial feed. In the case of AN homopolymerization, no consumption of I2 by AN was observed.

Thermal Decomposition Mechanism of 1,3,5,7-Tetranitro-1,3,5,7-tetrazocane Accelerated by Nano-Aluminum Hydride (AlH3): ReaxFF-Lg Molecular Dynamics Simulation.

ReaxFF-low-gradient reactive force field with CHONAl parameters is used to simulate thermal decomposition of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and AlH3 composite. Perfect AlH3 and surface-passivated AlH3 particles were constructed to mix with HMX. The simulation results indicate HMX is adsorbed on the surface of particles to form O–Al and N–Al bonds. The decomposition of HMX and AlH3 composite is an exothermic reaction without energy barrier, but the decomposition of pure HMX needs to overcome the energy barrier of 133.57 kcal/mol. Active nano-AlH3 causes HMX to decompose rapidly at low temperature, and the primary decomposition pathway is the rupture of N–O and C–N bonds. Adiabatic simulation shows that the energy release and temperature increase of HMX/AlH3 is much larger than those of the HMX system. Surface-passivated AlH3 particles only affect the initial decomposition rate of HMX. In HMX and AlH3 composites, the strong attraction of Al in AlH3 to O and the activation of the intermediate reaction by H2 cause HMX to decompose rapidly. The final decomposition products of pure HMX are H2O, N2, and CO2, and those of HMX/AlH3 are H2O, N2, and Al-containing clusters dominated by C–Al. The final gas production shows that the specific impulse of HMX/AlH3 is larger than that of HMX.

Decomposition rate and stabilization across six tundra vegetation types exposed to >20 years of warming

AimsLitter decomposition is an important driver of soil carbon and nutrient cycling in nutrient-limited Arctic ecosystems. However, climate change is expected to induce changes that directly or indirectly affect decomposition. We examined the direct effects of long-term warming relative to differences in soil abiotic properties associated with vegetation type on litter decomposition across six subarctic vegetation types. MethodsIn six vegetation types, rooibos and green tea bags were buried for 70–75 days at 8 cm depth inside warmed (by open-top chambers) and control plots that had been in place for 20–25 years. Standardized initial decomposition rate and stabilization of the labile material fraction of tea (into less decomposable material) were calculated from tea mass losses. Soil moisture and temperature were measured bi-weekly during summer and plant-available nutrients were measured with resin probes. ResultsInitial decomposition rate was decreased by the warming treatment. Stabilization was less affected by warming and determined by vegetation type and soil moisture. Soil metal concentrations impeded both initial decomposition rate and stabilization. ConclusionsWhile a warmer Arctic climate will likely have direct effects on initial litter decomposition rates in tundra, stabilization of organic matter was more affected by vegetation type and soil parameters and less prone to be affected by direct effects of warming.

Average leaf litter quality drives the decomposition of single-species, mixed-species and transplanted leaf litters for two contrasting tropical forest types in the Congo Basin (DRC)

Under similar site conditions, leaf litter decomposition beneath Central African rainforests was largely driven by average leaf litter quality. Although significant, the additional variability related to litter mixing and to the decomposition environment was limited. Under given site conditions, litter decomposition is expected to mainly depend on its average quality. However, the additional impacts of litter diversity as well as of the local decomposition environment remain rather inconclusive. This study investigates the litter mixture effects on decomposition and home-field advantage for two emblematic old growth forest types of the Congo Basin: the Scorodophloeus zenkeri Harms mixed forests and the evergreen Gilbertiodendron dewevrei (De Wild.) J. Leonard monodominant forests. Based on a litterbag experiment, variations in leaf litter mass loss were measured from the eight most important tree species under mixed and monodominant forests and for all possible two-species combinations. Remaining mass was largely explained (90%) by a multivariate measure of initial litter quality including 11 functional traits, which performed better than any single leaf litter trait. For the litter mixtures, the average deviation from expectation based on simple additive effects ranged from slightly synergistic (+ 2.56%) to slightly antagonistic (− 0.86%) after 1 and 6 months, respectively. Mixture identity and chemical dissimilarity contributed to explaining the mixing effects, yet the effect of chemical dissimilarity at the whole mixture level was only detected through an interaction with incubation time. In addition, the initial decomposition rates of S. zenkeri and G. dewevrei were accelerated under their own forest type. In agreement with the “home-field advantage” theory, our results highlighted that the functional composition of the host forest did have an indirect impact on decomposition. In addition, leaf litter decomposition was mainly controlled by average litter quality, which in turn was closely related to a multivariate measure of green leaf quality. This suggests that increased knowledge of tree species leaf traits in tropical forests would greatly help in better understanding the litter decomposition dynamics.

Nickel, Graphene, and Yttria-Stabilized Zirconia (YSZ)-Added Mg by Grinding in Hydrogen Atmosphere for Hydrogen Storage

Magnesium (Mg) has good hydrogen storage features except for its slow reaction kinetics with hydrogen and high hydride decomposition temperature. Yttria (Y2O3)-stabilized zirconia (ZrO2) (YSZ), nickel (Ni), and graphene were picked as additives to Mg to solve these problems. Samples with a composition of 92.5 wt% Mg + 2.5 wt% YSZ + 2.5 wt% Ni + 2.5 wt% graphene (designated as Mg + YSZ + Ni + graphene) were prepared by grinding in hydrogen atmosphere. The activation of Mg + YSZ + Ni + graphene was finished at the third cycle (n = 3). Mg + YSZ + Ni + graphene had an efficient hydrogen storage capacity (the amount of hydrogen absorbed for 60 min) over 7 wt% (7.11 wt%) at n = 1. Mg + YSZ + Ni + graphene contained Mg2Ni phase after cycling. The addition of Ni and Ni + YSZ greatly increased the initial hydride formation and decomposition rates, and the amount of hydrogen absorbed and released for 60 min, Ha (60 min) and Hd (60 min), respectively, of a 95 wt% Mg + 5 wt% graphene sample (Mg + graphene). Rapid nucleation of the Mg2Ni-H solid solution in Ni-containing samples is believed to have led to higher initial decomposition rates than Mg + graphene and Mg. The addition of YSZ also enhanced the initial decomposition rate and Hd (60 min) compared to a sample with a composition of 95 wt% Mg + 2.5 wt% Ni + 2.5 wt% graphene (Mg + Ni + graphene).

Decomposition rate of extraradical hyphae of arbuscular mycorrhizal fungi decreases rapidly over time and varies by hyphal diameter and season

Understanding how extraradical mycorrhizal fungal hyphae (EMH) regulate the cycling and retention of plant-assimilated carbon (C) in forest soils requires estimation of the production, mortality, and decomposition of EMH. To do this, the use of mass-balance models in combination with hyphal in-growth mesh bags (“in-growth bags”) was proposed in recent studies. However, poor knowledge on the decomposition of field-grown EMH prevents confirmation of assumed EMH decomposition dynamics. In this study, we determined the decrease in hyphal length density of field-grown EMH of arbuscular mycorrhizal fungi (AM) over eight months in in-growth bags incubated in a warm-temperate Chamaecyparis obtusa forest, to study EMH decomposition under field conditions. We used exponential decay models to describe the changes in the decomposition rate of EMH over the incubation time, between EMH diameter classes, and between seasons. A rapid decrease of the decomposition rate of EMH within two months from 2.5 to 0.1 month−1 was estimated, corresponding to an increase in half-life from 0.3 to 7 months. Furthermore, significant differences in the initial maximum decomposition rate were estimated between fine (1.6 month−1; minimum half-life: 0.4 months) and coarse EMH (3.1 month−1; minimum half-life: 0.2 months) and between incubations during spring-summer (April and August; 2.7 month−1; minimum half-life: 0.3 months) and autumn-winter (October and February; 1.1 month−1; minimum half-life: 0.6 months). This large variability in the decomposition rates of EMH of AM fungi has to be considered in mass-balance models to estimate C fluxes between plants, soil, and the atmosphere.

Effect of nitrogen addition on the decomposition and release of compounds from fine roots with different diameters: the importance of initial substrate chemistry

Initial substrate chemical characteristics are the most important factor in the regulation of fine root decomposition. However, it remains unclear how nitrogen (N) deposition changes the decomposition process by affecting initial substrate chemical characteristics with different fine root diameter sizes. We compared the root decomposition processes across three diameter sizes (very fine roots, 0.05), but low N addition enhanced the correlation coefficients between initial chemical indexes and decomposition rates. (3) Low N addition increased the release rates of C and cellulose in the very fine roots but not intermediate fine and largest fine roots, while the medium and high N addition decreased the release rates of N, P, cellulose and lignin in the very fine and intermediate fine roots by affecting the initial C, N, P, starch, cellulose and lignin concentrations. (4) Release of compounds from large diameter fine roots is less responsive to N addition than that from the small ones. The initial substrate chemistry plays an important role during the N addition affecting fine root decomposition and release of chemical compounds. Our results suggest that N deposition may change the biogeochemical processes of forest ecosystems by affecting the release of compounds from fine roots.

Long-term decomposition of aqueous S-nitrosoglutathione and S-nitroso-N-acetylcysteine: Influence of concentration, temperature, pH and light

Primary S-nitrosothiols (RSNOs) have received significant attention for their ability to modulate NO signaling in many physiological and pathophysiological processes. Such actions and their potential pharmaceutical uses demand a better knowledge of their stability in aqueous solutions. Herein, we investigated the effects of concentration, temperature, pH, room light and metal ions on the long-term kinetic behavior of two representative primary RSNOs, S-nitrosoglutathione (GSNO) and S-nitroso-N-acetylcysteine (SNAC). The thermal decomposition of GSNO and SNAC were shown to be affected by the auto-catalytic action of the thiyl radicals. At 25 °C in the dark and protected from the catalytic action of metal ions, GSNO and SNAC solutions 1 mM showed half-lives of 49 and 76 days, and apparent activation energies of 84 ± 14 and 90 ± 6 kJ mol−1, respectively. Both GSNO and SNAC exhibited increased stability in the pH range 5–7. At high pH the decomposition pathway of GSNO involves the formation of an intermediate (GS-NO22-), which decomposes generating GSH and nitrite. GSNO solutions displayed lower sensitivity to the catalytic action of metal ions than SNAC and the exposure to room light led to a 5-fold increase in the initial rates of decomposition of both RSNOs. In all comparisons, SNAC solutions showed higher stability than GSNO solutions. These findings provide strategic information about the stability of GSNO and SNAC and may open new perspectives for their use as experimental or therapeutic NO donors.

Descomposición de la hojarasca del Matorral Espinoso Tamaulipeco y de una especie vegetal introducida

La descomposición de la hojarasca es un proceso clave en el reciclado de nutrientes en los ecosistemas. Conocer su velocidad de descomposición ayudará a una mejor comprensión de la fertilidad del suelo y a proponer acciones de manejo que favorezcan la disponibilidad de nutrientes. Los objetivos del presente estudio fueron: i) evaluar la descomposición temprana de la hojarasca en un área de Matorral Espinoso Tamaulipeco (MET) y una plantación de eucaliptos (Eucalyptus camaldulensis), especie introducida en la región; y ii) determinar la correlación entre la pérdida de peso de la hojarasca y la precipitación, la temperatura y la evaporación. Para su evaluación se colocaron 64 bolsas de tul (ojo de malla de 1 mm) con hojarasca de MET y eucalipto. Las evaluaciones de masa remanente se hicieron mensualmente, durante seis meses. La descomposición fue mayor en MET (35.11 %) que en eucalipto (24.91 %). La constante de descomposición (k año‒1) fue mayor para MET (k=0.934) que para eucalipto (k=0.479). La masa remanente de la descomposición de la hojarasca mostró correlación negativa con la temperatura y la evaporación, tanto en el sitio de MET como el de eucalipto y solo este tuvo correlación negativa con la precipitación. La deposición de nutrientes al suelo, producto de la descomposición de hojarasca, será más lenta en plantaciones de eucalipto que en áreas de MET, por lo que la disponibilidad de nutrientes pudiera limitarse cuando se presentan los pulsos de precipitación que activan el crecimiento vegetal y las prácticas silvícolas deberán realizarse de acuerdo a ello.

Decomposing litter and associated microbial activity responses to nitrogen deposition in two subtropical forests containing nitrogen-fixing or non-nitrogen-fixing tree species

Atmospheric nitrogen (N) deposition has caused concern due to its effects on litter decomposition in subtropical regions where N-fixing tree species are widespread. However, the effect of N deposition on litter decomposition in N-fixing plantations remains unclear. We investigated the effects of a 2-year N deposition treatment on litter decomposition, microbial activity, and nutrient release in two subtropical forests containing Alnus cremastogyne (AC, N-fixing) and Liquidambar formosana (LF, non-N-fixing). The decomposition rate in AC was faster than in LF when there was no experimental N deposition. In AC, the initial decomposition rate was faster when additional N was applied and was strongly linked to higher cellulose-degrading enzyme activities during the early decomposition stage. However, N deposition reduced litter decomposition and inhibited lignin-degrading enzyme activities during the later decomposition stage. Nitrogen deposition enhanced carbohydrate and alcohol utilization, but suppressed amino acid and carboxylic acid uptake in the AC plantation. However, it did not significantly affect litter decomposition and microbial activity in the LF plantation. In conclusion, N deposition could inhibit litter decomposition by changing microbial enzyme and metabolic activities during the decomposition process and would increase carbon accumulation and nitrogen retention in subtropical forests with N-fixing tree species.

Stabilization versus decomposition in alpine ecosystems of the Northwestern Caucasus: The results of a tea bag burial experiment

Mountainous areas exhibit highly variable decomposition rates as a result of strong local differences in climate and vegetation type. This paper describes the effect of these factors on two major determinants of the local carbon cycle: litter decomposition and carbon stabilization. In order to adequately reflect local heterogeneity, we have sampled 12 typical plant communities of the Russian Caucasus. In order to minimize confounding effects and encourage comparative studies, we have adapted the widely used tea bag index (TBI) that is typically used in areas with low decomposition. By incubating standardized tea litter for a year, we investigated whether (1) initial litter decomposition rate (k) is negatively correlated with litter stabilization (S) and (2) whether k or S exhibit correlations with altitude and other environmental conditions. Our results show that S and k are not correlated. Altitude, pH, and water content significantly influenced the stabilization factor S, while soil-freezing had no influence. In contrast, none of these factors predicted the decomposition rate k. Based on our data, we argue that collection of decomposition rates alone, as is now common practice, is not sufficient to understand carbon input to soils and can potentially lead to misleading results. Our data on community-specific decomposition and stabilization rates further constrain estimates of litter accumulation in subalpine communities and the potential effects of climate change.

Persulfate initiated free-radical polymerization of itaconic acid: Kinetics, end-groups and side products

Persulfate initiated free radical homopolymerization of itaconic acid in aqueous media has been investigated at 65 °C. The research was focused on the elucidation of the chemical structure of low-molecular-weight side products and itaconic oligomers separated from polymeric fraction by dialysis (cut-off of 1000 Da). Nuclear magnetic resonance (NMR) 1H, 13C, 1H–13C me-HSQC and 1H–13C HMBC experiments and direct infusion electrospray ionization mass spectrometry (ESI-MS) operated in the negative ion mode have been combined to investigate the low-molecular fraction. It was found that 2-hydroxyparaconic and itatartaric acid are the primary oxidation products formed during free radical polymerization of itaconic acid. Besides, ESI-MS analysis revealed sulfate, hydroxyl and lactone terminal groups resulted from disproportionation, combination and transfer processes. Kinetics studies using Raman spectrometry in initiator range of 0.07–0.32 mol/L and for monomer concentration between 1.32 and 2.63 mol/L indicated non-classical dependency both polymerization rate and initiator decomposition rate on monomer and initiator concentration.

Effects of soil moisture on litter decomposition of three main tree species in Northeast China.

The effects of soil moisture variation on the litter decomposition of main tree species Betula platyphylla, Abies nephrolepis and Pinus koraiensis were evaluated in a primary forest of Korean pine (P. koraiensis) in Fenglin National Nature Reserve of the Northeast China, based on the measurements of surface (0-10 cm) soil moisture from 1998 to 2017. The results showed that litter decomposition rates increased with the increase of litter quality. The order of litter decomposition rate was B. platyphylla > A. nephrolepis > P. koraiensis at the same soil moisture. The litter decomposition rates decreased with the decrease of soil moisture. The sensitivity index of litter decomposition rates on soil moisture (M10) were 0.782, 0.789 and 0.827, respectively, for B. platyphylla, A. nephrolepis and P. koraiensis. The initial litter decomposition rate decreased by 21.8%, 21.1% and 17.3% for B. platyphylla, A. nephrolepis and P. koraiensis, respectively, when soil moisture decreased by 10%. The decomposition rates of high-quality litter (high nitrogen content, low carbon to nitrogen ratio, and low lignin content) were more sensitive to the variation of soil moisture. The difference in decomposition rate among different litter types was reduced with the decrease of soil moisture. In the recent 20 years, the average soil moisture presented a significantly decreasing trend, which would inhibit litter decomposition in the primary Korean pine forest. Under the scena-rios of global change, soil moisture would further decrease with the increase of air temperature. It would definitely intensify the inhibitory effect on litter decomposition, and partly offset the enhanced effects of increased air temperature.

Efficient removal of benzene in air at atmospheric pressure using a side-on type 172nm Xe2 excimer lamp.

The photochemical removal of benzene was studied in air at atmospheric pressure using a side-on type 172nm Xe2 excimer lamp with a wide irradiation area. After 1.5min photoirradiation, C6H6 (1000ppm) in air was completely converted to HCOOH, CO, and CO2 at a total flow rate of 1000mL/min. The initial decomposition rate of C6H6 was determined to be 1.18min-1. By using a flow system, C6H6 (200ppm) was completely removed at a total flow rate of 250mL/min. The conversion of C6H6 and the energy efficiency in the removal of C6H6 changed in the 31-100% and 0.48-1.2g/kWh range, respectively, depending on the flow rate, the O2 concentration, and the chamber volume. On the basis of kinetic model simulation, dominant reaction pathways were discussed. Results show that the O(3P) + C6H6 reaction plays a significant role in the initial stage of the C6H6 decomposition. Important experimental parameters required for further improvement of the C6H6 removal apparatus using a 172 excimer lamp were discussed based on model calculations.