Nakahara O.,Hokkaido University |
Takahashi M.,Japan Forestry and Forest Products Research Institute |
Sase H.,Acid Deposition and Oxidant Research Center |
Yamada T.,Japan National Institute of Public Health |
And 8 more authors.
Biogeochemistry | Year: 2010
Rapid industrialization in East Asia is causing adverse effects due to atmospheric deposition in terrestrial and freshwater ecosystems. Decreasing stream pH and alkalinity and increasing NO3 - concentrations were observed throughout the 1990s in the forested Lake Ijira catchment in central Japan. We investigated these changes using data on atmospheric deposition, soil chemistry, stream water chemistry, and forest growth. Average atmospheric depositions (wet + dry) of 0.83, 0.57, and 1.37 kmol ha-1 year-1 for hydrogen, sulfur, and nitrogen, respectively, were among the highest levels in Japan. Atmospheric deposition generally decreased before 1994 and increased thereafter. The catchment was acid-sensitive; stream alkalinity was low (134 μmolc l-1) and pH in surface mineral soils decreased from 4.5 in 1990 to 3.9 in 2003. Stream NO3 - concentration nearly doubled (from 22 to 42 μmolc l-1) from the late 1980s to the early 2000s. Stream NO3 - concentration was controlled primarily by water temperature before 1996/1997 and by stream discharge thereafter. Stream NO3 - concentrations decreased during the growing season before 1996/1997, but this seasonality was lost thereafter. The catchment became nitrogen-saturated (changing from stage 1 to 2) in 1996/1997, possibly because of declining forest growth rates due to the 1994 summer drought, defoliation of Japanese red pine by pine wilt disease, maturation of Japanese cedar stands, and stimulation of nitrogen mineralization and nitrification due to alkalinization of soils (increased exchangeable Ca2+ and soil pH) after the summer drought. Stream pH and alkalinity began decreasing in 1996/1997. The enhanced growing-season NO3 - discharge since 1996/1997 appeared to be the major cause of stream acidification. Increased atmospheric deposition since 1994 may have contributed to this change. © Springer Science+Business Media B.V. 2009.
Murata N.,Kyoto University |
Murata N.,Tottori University |
Ohta S.,Kyoto University |
Ishida A.,Japan Forestry and Forest Products Research Institute |
And 4 more authors.
Journal of Forest Research | Year: 2012
In several areas in Northeast Thailand, evergreen and deciduous forests coexist under uniform climatic conditions. To identify the factors that determine the distribution of these different forest types, we compared soil depth and soil physical properties between evergreen and deciduous forests, and monitored soil moisture conditions for a year in both forest types at the Sakaerat Environmental Research Station. The soil was significantly deeper under the evergreen forests (mean 97 cm) than under the deciduous forest (mean 64 cm). The soil under the evergreen forests retained much more water throughout the year than the soil under the deciduous forest, and there was also a clear tendency for the evergreen forests to occur in ravine areas, regardless of soil depth. It is possible that the evergreen trees can maintain transpiration during the dry season on thicker soils or in ravine areas, whereas shallower soils cannot provide enough water for these trees to maintain their evapotranspiration during the dry period. From the present study, we showed that soil water availability could be a significant factor determining the distribution of the deciduous and evergreen forests in our catchments. © 2011 The Japanese Forest Society and Springer.
Li J.,CAS Institute of Atmospheric Physics |
Wang Z.,CAS Institute of Atmospheric Physics |
Wang X.,CAS Institute of Atmospheric Physics |
Yamaji K.,Japan Agency for Marine - Earth Science and Technology |
And 8 more authors.
Atmospheric Environment | Year: 2011
Aerosols in the troposphere influence photolysis frequencies and hence the concentrations of chemical species. We used a three-dimensional regional chemical transport model (NAQPMS) coupled with an accurate radiative transfer model to examine the impacts of aerosols on summertime photochemistry in Central Eastern China (CEC) via changing photolysis frequencies. In addition to looking at changes in concentrations as previous studies have done, we examined the changes in ozone (O3) budgets and the uncertainties related to our estimations. The 1st-12th June 2006 was selected as the simulation period when high aerosol optical depth at 550nm (AOD550) and O3 were found. A comparison of measurements showed that the model was capable of reproducing the spatial and temporal variations in photolysis frequencies, ultraviolet (UV) radiation, AOD550, cloud optical depth, O3 and other chemical constitutes in CEC. Aerosols have important impacts on atmospheric oxidation capacity in CEC. On a regional scale, aerosols decreased the average O3→O (1D) photolysis frequency by 53%, 37% and 21% in the lower, middle and upper troposphere in CEC. The uncertainties of these estimations were 37%, 25% and 14%, respectively. Mean OH concentrations decreased by 51%, 40% and 24% in layers below 1km, 1-3km and 3-10km, with uncertainties of 39%, 28% and 9%, respectively. The changes in HO2 concentrations were smaller but significant. In contrast, NOx showed a significant increase at 0-1km and 1-3km in CEC, with magnitudes of 6% and 8%. The largest relative enhancement occurred in downwind regions below 1km. Summertime boundary layer O3 (below 1km and 1-3km) was reduced by 5% with a maximum of 9% in highly polluted regions. The reduced ozone production (P (O3)) was responsible for this reduction below 3km. © 2011 Elsevier Ltd.
Suthawaree J.,Tokyo Metroplitan University |
Kato S.,Tokyo Metroplitan University |
Pochanart P.,Japan Agency for Marine - Earth Science and Technology |
Pochanart P.,National Institute of Development Administration |
And 5 more authors.
Atmospheric Research | Year: 2012
In order to elucidate an impact of Beijing outflow on air quality in the mountainous area, measurement campaign was carried out in Mt. Mang, located 40. km north of Beijing in September 2007. Volatile Organic Compounds (VOC) observed at the site were mainly influenced by air masses arriving from urban areas. No significant impact of local emission was found. Correlation plots between selected VOC suggests several major emission sources as internal combustion, industrial emission, and coal, oil and biofuel burning. Air masses were classified into "polluted" (influence of Beijing and its satellite cities) and "clean" air mass by using backward trajectory analysis. Two air mass categories revealed significant different characteristics and mixing ratios. Reaction with OH is a major factor controlling mixing ratio of "clean" air mass while impact of dilution is also play important role on "polluted" air mass. Estimation of photochemical age of "polluted" air mass by assuming "clean" air mass for background mixing ratios reveals an averaged of 1.5-1.8. days. © 2012 Elsevier B.V.
Katata G.,Japan Atomic Energy Agency |
Nagai H.,Japan Atomic Energy Agency |
Kajino M.,Tokyo University of Science |
Ueda H.,Acid Deposition and Oxidant Research Center |
Hozumi Y.,Acid Deposition and Oxidant Research Center
Agricultural and Forest Meteorology | Year: 2010
The aim of the present study was to evaluate fog (cloud water) deposition on vegetation and its contribution to the balance of water and energy in semi-arid and arid regions. Fog deposition onto the woodlands in semi-arid environments in Saudi Arabia was estimated using a detailed land surface model (SOLVEG) that included fog deposition on vegetation in meteorological conditions simulated using a three-dimensional mesoscale meteorological model (MM5). MM5 proved capable of reproducing meteorological variables and successfully detected fog events, although it did overestimate the liquid water content of the fog. Despite the margin of an error due to that overestimation, SOLVEG calculations indicated that fog deposition provides a more effective source of water for plant growth than the heavy rainfall typically observed in semi-arid and arid areas. Water evaporation from the surfaces of the leaves (leaf surface water) eases the plant's water stress by reducing the need for transpiration, even if the leaf surface water due to fog deposition does not drip onto the soil and is thus not a source of water for the plants. Latent heat being released through evaporation from the leaf surface water and soil reduces the temperature of the soil and leaves during the daytime, which in turn then eases heat stress in woodlands. Moreover, the decreased transpiration rates that result from the increase in evaporation from the leaf surface water due to fog deposition is an effective source of water for use in photosynthesis for the plants suffering from severe water stress in semi-arid and arid environments. Our results suggest that fog deposition can affect the accuracy of the water and heat exchange that take place in the atmosphere-land interface in semi-arid and arid regions. © 2009 Elsevier B.V. All rights reserved.
Yamashita N.,Acid Deposition and Oxidant Research Center |
Yamashita N.,Kyoto University |
Ohta S.,Kyoto University |
Sase H.,Acid Deposition and Oxidant Research Center |
And 5 more authors.
Forest Ecology and Management | Year: 2010
Seasonal and spatial variability of litterfall and NO3 - and NH4 + leaching from the litter layer and 5-cm soil depth were investigated along a slope in a tropical dry evergreen forest in northeastern Thailand. Using ion exchange resin and buried bag methods, the vertical flux and transformation of inorganic nitrogen (N) were observed during four periods (dry, early wet, middle wet, and late wet seasons) at 15 subplots in a 180-m × 40-m rectangular plot on the slope. Annual N input via litterfall and inorganic N leached from the litter layer and from 5-cm depth soil were 12.5, 6.9, and 3.7 g N m-2 year-1, respectively, whereas net mineralization and the inorganic N pool in 0-5-cm soil were 7.1 g N m-2 year-1 and 1.4 g N m-2, respectively. During the early wet season (90 days), we observed 82% and 74% of annual NO3 - leaching from the litter layer and 5-cm soil depth, respectively. Higher N input via leaf litterfall in the dry season and via precipitation in the early wet season may have led to higher NO3 - leaching rate from litter and surface soil layers during the early wet season. Large spatial variability in both NO3 - vertical flux and litterfall was also observed within stands. Small-scale spatial patterns of total N input via litterfall were significantly correlated with NO3 - leaching rate from the surface soil layer. In tropical dry evergreen forests, litterfall variability may be crucial to the remarkable seasonal changes and spatial variation in annual NO3 - vertical flux in surface soil layers. © 2010 Elsevier B.V. All rights reserved.
Taketani F.,Japan Agency for Marine - Earth Science and Technology |
Kanaya Y.,Japan Agency for Marine - Earth Science and Technology |
Akimoto H.,Acid Deposition and Oxidant Research Center
Journal of Physical Chemistry Letters | Year: 2010
The uptake coefficient(γ) of HO2 for submicrometer aerosol particles of levoglucosan and polystyrene latex (PSL) under ambient conditions (760 Torr and 296 ± 2 K) have been investigated using an aerosol flow tube (AFT) coupled with a chemical conversion/laser-induced fluorescence (CC/LIF) technique. Determined γ values for levoglucosan particles were <0.01, 0.01 ± 0.01, 0.05 ± 0.01, 0.09 ± 0.02, and 0.13 ± 0.03, at relative humidities (RHs) of 20, 40, 55, 75, and 92%, respectively, while the ? values for PSL particles were 0.01 ± 0.01, 0.02 ± 0.01, and 0.03 ± 0.01 at RHs of 22, 58, and 92%, respectively. The dependence of HO2 uptake on RH by levoglucosan and PSL particles is discussed. © 2010 American Chemical Society.