[Show abstract][Hide abstract] ABSTRACT: The expansion of Moso bamboo forests in Japan might change transpiration and therefore reduce the availability of water resources. Moso bamboo stands are often composed of culms with various ages and older culms may have lower sap flux density (Fd), which may in turn affect individual culm transpiration (Qt), probably because vascular bundles do not regenerate after sprouting. Information related to the differences of Fd and Qt between younger and older culms would be important for (i) understanding the effects of culm age structure changes on stand-scale transpiration (EC), and (ii) developing sampling strategies for EC estimates in Moso bamboo forests. We conducted sap flux measurements for 15 individuals from four culm age classes in a managed Moso bamboo forest in Kameoka, Kyoto, Japan. Differences in Fd were not significant among the four culm age classes with almost the same stem diameter at breast height (DBH). Qt was related to DBH across four age classes, indicating that culm age had no apparent effect on Qt in the forest. Our results suggest the effects of culm age structure changes on EC are small, and contribute to development of sampling strategy without considering culm age structure for EC estimates at this site.
Preview · Article · Jan 2016 · Hydrological Research Letters
[Show abstract][Hide abstract] ABSTRACT: To understand the mechanism of formation of the secondary organic aerosols (SOAs) produced by the ozonolysis of isoprene, proton transfer reaction mass spectrometry (PTR-MS) was used to identify the semi-volatile organic compounds (SVOCs) produced in both the gaseous and the aerosol phases and to estimate the gas aerosol partitioning of each SVOC in chamber experiments. To aid in the identification of the SVOCs, the products were also studied with negative ion-chemical ionization mass spectrometry (NI-CIMS), which can selectively detect carboxylic acids and hydroperoxides. The gaseous products were observed by on-line PTR-MS and NI-CIMS, whereas the SVOCs in SOAs collected on a filter were vaporized by heating the filter and were then analysed by off-line PTR-MS and NI-CIMS. The formation of oligomeric hydroperoxides involving a Criegee intermediate as a chain unit was observed in both the gaseous and the aerosol phases by NI-CIMS. PTR-MS also detected oligomeric hydroperoxides as protonated molecules from which a H2O molecule was eliminated, [M-OH](+). In the aerosol phase, oligomers involving formaldehyde and methacrolein as chain units were observed by PTR-MS in addition to oligomeric hydroperoxides. The gas-aerosol partitioning of each component was calculated from the ion signals in the gaseous and aerosol phases measured by PTR-MS. From the gas-aerosol partitioning, the saturated vapour pressures of the oligomeric hydroperoxides were estimated. Measurements by a fastmobility-particle-sizer spectrometer revealed that the increase of the number density of the particles was complete within a few hundred seconds from the start of the reaction.
No preview · Article · Nov 2014 · Atmospheric Environment
[Show abstract][Hide abstract] ABSTRACT: The increased use of biomass fuel use among rural Indonesian households
for years despite national program on subsidized LPG fuel distribution
pose threat of indoor air pollution for the householders. Indoor air
pollution levels of PM2.5 and CO in the kitchen of 40
households using the fuelwood as the main cooking fuel were measured in
the same season in mountainous and coastal areas in Indonesia. The
temporal variations of PM2.5 and its size distributions were
simultaneously measured using photoelectric UCB monitor and personal
cascade impactor, respectively. While carbon monoxide (CO)
concentrations were measured using USB-CO monitors. Household indoor air
pollution in the mountainous area was generally higher than that in the
coastal area. This is because the households in coastal area have higher
kitchen volume (about three times), smaller ventilation area (about 1.7
times) and shorter cooking duration with wood fuel (0.6 times) than
those in mountainous area. Yet, during cooking with fuelwood, the indoor
PM2.5 concentrations at the cook site showed almost
comparable results for both sites. The wood stove burning in coastal
area tended to be in flaming combustion than in mountainous area. This
can be indicated by a higher fraction of finest particles in
PM2.5, a higher fraction of EC in PM2.5 and a
higher fraction of K+ and Cl- ions in
PM2.5 mass concentrations. The time-averaged CO
concentrations for 22-h measurements at the mountainous area were higher
than those in coastal area. The mountainous area showed higher positive
correlation relationship between the measured concentrations of CO and
PM2.5 than those in the coastal area. The use of cleaner
fuel, e.g., subsidized LPG fuel in rural area should be promoted and
managed intensively in mountainous area than in coastal area to avoid
people exposure of health damaging indoor air pollutants.
No preview · Article · Jan 2014 · Atmospheric Environment
[Show abstract][Hide abstract] ABSTRACT: In order to understand the effect of OH radical scavengers on secondary
organic aerosol formation, aerosol yields from the isoprene ozonolysis
were measured in the presence of sufficient amounts of OH radical
scavengers. Cyclohexane, CO, n-hexane, and diethyl ether were used as
the OH radical scavengers. The aerosol yield was determined to be
0.002-0.023 for experiments without OH radical scavengers in the
aerosol mass range 2-120 μg m-3.
Similar aerosol yields were observed in experiments using cyclohexane.
The aerosol yield observed with n-hexane was close to that observed
without scavengers at 120 μg m-3, but this
aerosol yield was slightly lower than those observed in reactions
without scavengers in the range
3-83 μg m-3. The offline aerosol
samples obtained in experiments with cyclohexane or n-hexane contained
oxygenated hydrocarbons with six or more carbon atoms. Aerosol formation
in experiments that used cyclohexane or n-hexane as the scavenger was
enhanced. This was caused by the oxidation products of the OH radical
scavengers, although the increase in the yield could not be quantified.
The aerosol yields were 0.002-0.014 for experiments with CO and
diethyl ether in the aerosol mass range
4-120 μg m-3. The reaction of CO
with OH radicals forms HO2 radicals, whereas the reactions of
cyclohexane, n-hexane, and diethyl ether, respectively, with OH radicals
form organic peroxy (RO2) radicals. Present results show that
the aerosol yield is independent of the HO2/RO2
ratio or that it decreases with increasing HO2/RO2
ratio. Since the HO2 concentration is much higher than the
RO2 concentration in the atmosphere, the results obtained
using CO in this study will be a good approximation of the aerosol yield
from the ozonolysis of isoprene in the atmosphere.
No preview · Article · Nov 2013 · Atmospheric Environment
[Show abstract][Hide abstract] ABSTRACT: Asian dust storms originating from arid regions of Mongolia and China are a well-known springtime phenomenon throughout East Asia. Evidence is increasing for the adverse health effects caused by airborne desert dust inhalation. Given that people spend approximately 90 % of their time indoors, indoor air quality is a significant concern. The present study aimed to examine the influence of outdoor particulate matter (PM) levels on indoor PM levels during Asian dust events under everyday conditions.
We simultaneously monitored counts of particles larger than 0.3, 0.5, 1, 2, and 5 μm using two direct-reading instruments (KC-01D1 airborne particle counter; Rion), one placed in an apartment room and another on the veranda, under everyday conditions before and during an Asian dust event. We also examined how indoor particle counts were affected by opening a window, crawling, and air purifier use.
An Asian dust event on 24 April 2012 caused 50- and 20-fold increases in PM counts in outdoor and indoor air, respectively. A window open for 10 min resulted in a rapid increase of indoor PM counts up to 70 % of outside levels that did not return to baseline levels after 3 h. An air purifier rapidly reduced PM counts for all particle sizes measured.
It is important to account for occupant behavior, such as window-opening and air purifier use, when estimating residential exposure to particulate matter.
Full-text · Article · Aug 2013 · Environmental Health and Preventive Medicine
[Show abstract][Hide abstract] ABSTRACT: Jatropha curcas has been introduced and sold as cook stove fuel in Indonesia since late 2010, after the progressive phasing-out of the subsidy for kerosene started in 2007. To review the reliability and probable health impacts of J. curcas Seed (JCS) stoves used for cooking, the standard water boiling test (WBT) was used to evaluate the stove's basic performance (thermal efficiency and specific fuel consumption) and the indoor air quality associated with its emissions and these parameters were compared with those of a traditional wood stove (WS). The emissions were analyzed using a CO monitor, photoelectric PM (particulate matter) monitors and the Sioutas Cascade Impactor to characterize the CO (carbon monoxide) concentration, temporal variations in PM mass concentrations and the mass size distributions from the stove emissions respectively.
In general the JCS stove showed higher thermal efficiency and lower specific fuel consumption than the wood stove. Average indoor PM2.5 concentration at a cook site around a traditional wood stove was twelve times that around the JCS stove. Likewise, the JCS stove produced only about half of the indoor CO concentration compared to the wood stove emission. This suggests that replacing traditional wood stoves by JCS stoves reduces the exposure of cooks to PM2.5 and CO. Predominance of organic carbon in the collected aerosol 、during JCS stove combustion indicated that it resulted from the incomplete burning of organic matter in the seed. This study suggests that the JCS stove could be a promising substitute to the traditional wood stove. However the capacity of the stove, its re-fuelling method and tar produced should be improved and overcome to meet the practical needs of the rural cooking environment.
No preview · Article · Aug 2013 · Energy for Sustainable Development
[Show abstract][Hide abstract] ABSTRACT: Quercus serrata Thunb. ex Murray is a widespread deciduous oak in China, the Korean Peninsula, and Japan, and a strong isoprene emitter. Establishing accurate inventories of this species and estimating net carbon budgets, including biogenic volatile organic compounds (BVOC), necessitates detailed evaluation of BVOC emission and oxidation characteristics. Emissions of isoprene, the most abundant BVOC, presumably contribute to atmospheric chemistry through the formation of photochemical oxidants and secondary organic aerosols. We built an isoprene flux monitoring system to simultaneously reveal characteristics of the flux and fate of isoprene at multiple locations in Q. serrata forests. We used proton transfer reaction mass spectrometry (PTR-MS) and an automated closed chamber to measure isoprene emissions from soil and leaves in a warm-temperate Q. serrata forest. We used a relaxed eddy accumulation system with PTR-MS to simultaneously measure the canopy flux. In continuous foliage chamber measurements, we observed daily variations of isoprene emissions and continuous nocturnal emissions from leaves. Nocturnal emissions exceeded 25 % of total daily leaf emissions and were relatively high at sunset and low at sunrise. These results suggest that nocturnal emissions from mature trees may not be negligible. When leaf emissions were high in the daytime, the canopy isoprene flux tended to plateau at an upper limit. Observations of isoprene concentrations and gradients suggest that the plateau was caused by acceleration of isoprene oxidation, and sequential formation of secondary organic aerosols may occur near the leaf just after emission. Elucidation of these linkages may require continuous field measurements with a simultaneous multi-flux monitoring system.
No preview · Article · Feb 2013 · Journal of Forest Research
[Show abstract][Hide abstract] ABSTRACT: Effect of drought on isoprene emission from 2 major Quercus species native to East Asia is investigated. Three individuals of Quercus serrata and 2 individuals of Quercus crispula continued to emit isoprene under moderate and severe drought conditions, although the emission rates were lower than under normal conditions. Diurnal variation in the isoprene emission rates was monitored in real-time when temperature and light intensity were changed stepwise to imitate natural conditions. Under normal and moderate drought conditions, isoprene emission showed hysteresis with regard to the environmental parameters, but generally followed the common G93 model. Under severe drought conditions, isoprene emission rates were not explained using given coefficients in the G93 model, probably due to a depletion of isoprene substrate.
No preview · Article · Nov 2011 · Atmospheric Environment
[Show abstract][Hide abstract] ABSTRACT: We investigated effects of heterogeneous stomatal behavior on diurnal patterns of leaf gas exchange in 10 tree species. Observations were made in middle and upper canopy layers of potted tropical rainforest trees in a nursery at the Forest Research Institute Malaysia. Measurements were taken from 29 January to 3 February 2010. We measured in situ diurnal changes in net photosynthetic rate and stomatal conductance in three leaves of each species under natural light. In both top-canopy and sub-canopy species, midday depression of net assimilation rate occurred in late morning. Numerical analysis showed that patchy bimodal stomatal behavior occurred only during midday depression, suggesting that the distribution pattern of stomatal apertures (either uniform or non-uniform stomatal behavior) varies flexibly within single days. Direct observation of stomatal aperture using Suzuki's Universal Micro-Printing (SUMP) method demonstrated midday patchy stomatal closure that fits a bimodal pattern in Shorea leprosula Miq., Shorea macrantha Brandis. and Dipterocarpus tempehes V.Sl. Inhibition of net assimilation rate and stomatal conductance appears to be a response to changes in vapor pressure deficit (VPD). Variable stomatal closure with increasing VPD is a mechanism used by a range of species to prevent excess water loss from leaves through evapotranspiration (viz., inhibition of midday leaf gas exchange). Bimodal stomatal closure may occur among adjacent stomata within a single patch, rather than among patches on a single leaf. Our results suggest the occurrence of patches at several scales within single leaves. Further analysis should consider variable spatial scales in heterogeneous stomatal behavior between and within patches and within single leaves.
[Show abstract][Hide abstract] ABSTRACT: To estimate net ecosystem exchange (NEE) and net ecosystem production (NEP) in a forest situated on complex terrain, we evaluated the sensitivity of the estimates of NEE to the choice of a friction velocity (u*) correction for the estimation of flux on calm night. And compared these estimates with estimates based on biometric data using a warm-temperate deciduous and evergreen mixed forest in Japan. Biometric approaches were based on analyses of autotrophic carbon pools and heterotrophic carbon fluxes (NEP) versus changes in two major carbon pools (ΔC). To estimate ΔC, we calculated contributions to the soil carbon pool by litter and coarse woody debris (CWD) independently. The 3-year mean annual NEE from 2000 to 2002 was −1.23 MgC ha−1 year−1 (a negative flux indicates carbon gain). Estimated ΔC and NEP were 1.73 and 0.91 MgC m−2 year−1, respectively (a positive flux indicates carbon gain). The increment of live biomass contributed 76% of total ΔC. Estimated NEP varied widely due to large spatial variation in soil respiration. A realistic u* threshold was 0.4 m s−1. The estimated NEE value was larger than NEP. The change in NEE as a function of the u* threshold was marked, and most of the measured data (about 80%) could be eliminated by using the 0.4 m s−1u* threshold. These results seem to be caused by the loss of most nocturnal respiration as a result of horizontal advection or drainage flow (because the study site was located on complex terrain). This tendency was consistent for towers located on a ridge and in a valley.
Full-text · Article · May 2008 · Agricultural and Forest Meteorology
[Show abstract][Hide abstract] ABSTRACT: We conducted field measurements of isoprene emissions from sunlit and shaded leaves of Quercus serrata, which is one of the major tree species in Japan. The measurements were conducted at the Yamashiro Flux Tower site in a deciduous broad-leaved forest. In June 2006, the isoprene emission rate (I), together with the net assimilation rate (A) and photosynthetic photon flux density (PPFD), was measured using a leaf cuvette. The experimental results demonstrated that I peaked at around noon for both the sunlit and shaded leaves, while A of the sunlit leaves peaked in the morning with a subsequent gradual decline. Consequently, the ratio of carbon emitted as isoprene to carbon fixed by photosynthesis (carbon ratio) increased during the afternoon. Data sets obtained at PPFD values higher than 1000 µmol m-2 s-1 revealed that highly correlated with the leaf temperature. The averages of the basal emission rate IS, calculated using the Guenther algorithm (G93), were 42.9 and 20.5 nmol m-2 s-1, respectively, for the sunlit and shaded leaves of Q. serrata. Our result indicates that Q. serrata should be categorized as a strong isoprene emitter. The measured I value estimated by the G93 model was consistent with the I value within a root-mean-square (RMS) error of 4 nmol m-2 s-1, suggesting that the G93 model can be used to determine the isoprene emission response of Q. serrata to PPFD and the leaf temperature.
Full-text · Article · Jan 2008 · Journal of Agricultural Meteorology
[Show abstract][Hide abstract] ABSTRACT: This is the first report of light-dependent monoterpene emissions from an oak species native to Asia. Isoprenoids emitted by Querem phillyraeoides were measured using branch enclosure methods. Sabinene, and. α- and β-pinenes were the major compounds accounting for more than 90% of the total monoterpene emissions. The basal, emission rates of total, monoterpenes on leaf area and leaf dry weight bases ranged from 0.07 to 6.30 nmol m -2 s -1 and from 0.22 to 14.3 μg g -1 h -1, respectively. A proton transfer reaction mass spectrometry measurement revealed that the emissions depend significantly on light intensity and leaf temperature. Q. phillyraeoides may be taxonomically close to European, monoterpene-emitting oaks because it is morphologically close to the oaks native to the Mediterranean area, and because the geographical features of their habitats are similar to each, other.
Full-text · Article · Jan 2008 · Environmental Control in Biology
[Show abstract][Hide abstract] ABSTRACT: 1. INTRODUCTION Isoprene is a biogenic volatile organic compound (BVOC) emitted by many plant species. Isoprene emission contributes to the reactive carbon budget entering the troposphere. In Japan efforts to measure and understand the mechanism controlling BVOC emissions and to establish their emission inventories for the country have not been extensive, despite the fact that Japan has a large area of forests composed of coniferous and/or deciduous tree species (about 70% of total land area) and that forestry statistics across Japan are available (Tani et al. 2002). 2. METHODS The measurements were taken in the deciduous broad-leaved forest, Yamashiro, Kyoto. The isoprene emission, net assimilation rate, stomatal conductance, photosynthetically active radiation (PAR), air and leaf temperature, relative humidity was measured on June, July, August 2006 using a LI-6400 portable photosynthesis system (Li-Cor Inc., Lincoln, NE, USA). Isoprene samples from the LI-6400 cuvette was trapped by adsorbents (Tenax 200mg and Carbotrap 100mg) packed into stainless steel tubes (Perkin Elmer). Samples were analyzed using GC-MS system (Shimadzu QP5050A). Samples underwent two stage thermal desorption (Perkin-Elmer ATD). 3. RESULTS The obvious effect of PAR on isoprene emissions and photosynthesis rates were investigated. Temporal variations of isoprene emissions and photosynthesis rates for sun leaves and a shade leaves were investigated. Isoprene sampling term is 7:00-9:00, 9:00-11:00, 11:00-13:00, 13:00-15:00, 15:00-17:00, and 17:00-18:30. Number of samples is 4-6 leaves. Both sun leaves and shade leaves, isoprene emissions reached their peak around noon, while for sun leaves the largest photosynthesis rates during morning and the subsequent decrease were observed as shown. Carbon ratio (carbon of isoprene emission /carbon of photosynthesis by mass unit) were about 1-3%. REFERENCES Tani, A., Nozoe, S., Aoki, M., Hewiit, C. N., 2002. Monoterpene fluxes measured above a Japanese red pine forest at Oshiba plateau, Japan. Atmospheric Environment, 36(21) : 41-52. Tani, A., Fushimi, K., 2005. Effects of temperature and light intensity on isoprene emission of Edgeworthia chrysantha. J. Agric. Meteorol, 61(2): 113-122.
[Show abstract][Hide abstract] ABSTRACT: Using electron tomography with a transmission electron microscope (TEM), we measured and quantified three-dimensional (3D) information for individual soot aggregates from Asian dust and a diesel vehicle. Soot aggregates are significant factors for evaluating and predicting global climate change. Many studies have been done to determine the physical properties of the individual particles. However, because soot particles have complex structures that are not fully visible in 2D images, with projecting parts and pores overlapping one another, it has been difficult to describe and properly quantify their properties. We are using electron tomography to reconstruct 3D data from series of 2D TEM images obtained at various tilt angles. The results have allowed determination of volume, surface area, maximum length, fractal dimension, and the number of primary particles within given soot aggregates. The Asian dust samples contain mineral dust and anthropogenic particles such as soot, fly ash, and metal particles from Chinese industrial areas, which are major sources of pollutants. From the 3D analyses, we found that the volumes, surface areas, and fractal dimensions of our primary Asian dust particles are generally larger than those of the diesel soot. The generality of this result remains to be tested.
[Show abstract][Hide abstract] ABSTRACT: In this study, qualitative elemental imagination for various atmospheric environmental species was attempted using micro-PIXE. Here, we present the results of an application of micro-PIXE to the study of atmospheric environment. The detailed spatial resolution of multiple elements for various samples like individual ambient particles, individual raindrops, individual fog droplets, and individual snow crystals could be successfully achieved by scanning 2.6 MeV H + micro beam with 1-2 µm diameter.