Deposition Process of Sulfate and Elemental Carbon in Japanese and Thai Forests

Hiroyuki Sase,Keiichi Sato,Pojanie Khummongkol,Naoyuki Yamashita,Shigeki Uchiyama,Makoto Nakata,Masamitsu Miyazawa,Kazuhide Matsuda,I Wuled Lenggoro,Hathairatana Garivait,Jesada Luangjame,Thiti Visaratana,Junko Shindo,Bopit Kietvuttinon,Tomomi Endo,Bundit Hongthong

doi:10.5572/ajae.2012.6.4.246

Abstract

Particulate matter deposited on leaf surfaces may cause erosion/abrasion of epicuticular wax and the malfunction of stomata. However, the deposition processes of particulate matter, such as elemental carbon (EC), has not been studied sufficiently in Asian forest ecosystems. Deposition processes for particulate <TEX>${SO_4}^{2-}$</TEX> and EC were studied in a Japanese cedar forest in Kajikawa, Niigata Prefecture, Japan, and in a dry evergreen forest and a dry deciduous forest in Sakaerat, Nakhon Ratchasima province, Thailand. The <TEX>${SO_4}^{2-}$</TEX> fluxes attributed to rainfall outside the forest canopy (RF), throughfall (TF), and stemflow (SF) showed distinct seasonalities at both sites, increasing from November to February at the Kajikawa site and in March/April at the Sakaerat site. Seasonal west/northwest winds in winter may transport sulfur compounds across the Sea of Japan to the Kajikawa site. At the Sakaerat site, pollutants suspended in the air or dry deposits from the dry season might have been washed away by the first precipitations of the wet season. The EC fluxes from RF and TF showed similar variations by season at the Kajikawa site, while the flux from TF was frequently lower than that from RF at the Sakaerat site. Particulate matter strongly adsorbed onto leaf surfaces is not washed away by rainfall and contributes to the EC flux. At the Kajikawa site, Japanese cedar leaf surfaces accumulated the highest levels of particulate matter and could not be neglected when calculating the total flux. When such leaf-surface particles were considered, the contribution of dry deposition to the total EC flux was estimated to be 67%, 77%, and 82% at the Kajikawa site, and at the evergreen and deciduous forests of the Sakaerat site, respectively. Leaf-surface particles must be included when evaluating the dry and total fluxes of particulate matter, in particular for water-insoluble constituents such as EC.

Highlights

Forests in the East Asian region may suffer badly from the effects of air pollutants derived from the large energy consumption in the region
1 SO42- Fluxes Seasonal variations in the SO42- fluxes are shown in Fig. 2 for 9 and 4 water years at the Kajikawa and Sakaerat sites, respectively
The deposition processes of particulate SO42- and elemental carbon (EC) were studied in different types of forests in the East Asian region

Summary

Introduction

Forests in the East Asian region may suffer badly from the effects of air pollutants derived from the large energy consumption in the region. Air pollutants including aerosols deposit on leaf surfaces or bark surfaces in the canopy. The deposition of air pollutants may cause physical and/or chemical alteration of the conditions on the leaf surface, resulting in physiological dysfunction of the trees (Sase et al, 1998). The changes to the leaf surface conditions accelerate cuticular transpiration (uncontrolled water loss) from the leaf surface (Sase et al, 1998) and dysfunction of stomata due to the water stress caused by particulate deposition (Takamatsu et al, 2001a). Degradation of wax and/or deposition of particulate matter caused an increase in the leaf-surface wettability, affecting ion fluxes in the canopy (Sase et al, 2008). It is important to study the deposition processes of air pollutants onto the forest canopy, in particular those of particulate matter

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Discussion

Conclusion