TY - JOUR
T1 - Seasonal and Spatial Variations of Chemical Weathering in the Mekong Basin
T2 - From the Headwaters to the Lower Reaches
AU - Kajita, Hiroto
AU - Ota, Yuki
AU - Yoshimura, Toshihiro
AU - Araoka, Daisuke
AU - Manaka, Takuya
AU - Ziyu, Ouyang
AU - Iwasaki, Shinya
AU - Yanase, Takuya
AU - Inamura, Akihiko
AU - Uchida, Etsuo
AU - Zheng, Hongbo
AU - Yang, Qing
AU - Wang, Ke
AU - Suzuki, Atsushi
AU - Kawahata, Hodaka
N1 - Funding Information:
We would like to thank students and researchers at Yunnan University for their great help in the fieldwork. We also thank for valuable suggestions that helped to improve this manuscript by Editor Dr. Marc Benedetti and anonymous reviewers. This research was partly supported by the Graduate Research Abroad in Science Program (GRASP) of the University of Tokyo for H. Kajita. It was also jointly supported by the Second Tibetan Plateau Scientific Expedition and Research (STEP) (2019QZKK0704), the Strategic Priority Research Program of Chinese Academy of Sciences (XDB26020301), and National Natural Science Foundation of China (NSFC) (U1902208, 41991323) to H. Zheng.
Funding Information:
We would like to thank students and researchers at Yunnan University for their great help in the fieldwork. We also thank for valuable suggestions that helped to improve this manuscript by Editor Dr. Marc Benedetti and anonymous reviewers. This research was partly supported by the Graduate Research Abroad in Science Program (GRASP) of the University of Tokyo for H. Kajita. It was also jointly supported by the Second Tibetan Plateau Scientific Expedition and Research (STEP) (2019QZKK0704), the Strategic Priority Research Program of Chinese Academy of Sciences (XDB26020301), and National Natural Science Foundation of China (NSFC) (U1902208, 41991323) to H. Zheng.
Publisher Copyright:
© 2020, Springer Nature B.V.
PY - 2020/6/1
Y1 - 2020/6/1
N2 - Chemical weathering in the Himalayan river basins is among the highest in the world and has received vast research attention related to past climate change. Many early estimates of chemical weathering are based on a small number of water property data that ignore those spatial and seasonal variations. Therefore, this study analyzed spatial and seasonal variations in chemical weathering in the Mekong Basin, where the geology, climate, and hydrologic cycle of the basin vary significantly from the lower to upper reaches and from dry to rainy seasons. We separately estimated the origins of dissolved elements and potential CO2 consumption rates using the numerous chemical compositions of river water throughout the entire basin and in both seasons. The CO2 consumption rate in the rainy season is three to five times that in the dry season that may be due to the high temperature and precipitation. Despite the low temperatures and dryness of the upper and middle basins, the CO2 consumption rate is approximately twice that in the lower reaches; this can be attributed to active physical denudation in steep mountainous areas which increases the surface area for water–rock interactions. The total CO2 consumption obtained by combining each season and basin was 48‒70 × 109 mol/a and 148‒159 × 109 mol/a for silicate and carbonate weathering, respectively, which are almost half the values of previous estimates. Our results suggest that seasonally and spatially separated evaluations are important for generating estimates of chemical weathering in large Himalayan rivers.
AB - Chemical weathering in the Himalayan river basins is among the highest in the world and has received vast research attention related to past climate change. Many early estimates of chemical weathering are based on a small number of water property data that ignore those spatial and seasonal variations. Therefore, this study analyzed spatial and seasonal variations in chemical weathering in the Mekong Basin, where the geology, climate, and hydrologic cycle of the basin vary significantly from the lower to upper reaches and from dry to rainy seasons. We separately estimated the origins of dissolved elements and potential CO2 consumption rates using the numerous chemical compositions of river water throughout the entire basin and in both seasons. The CO2 consumption rate in the rainy season is three to five times that in the dry season that may be due to the high temperature and precipitation. Despite the low temperatures and dryness of the upper and middle basins, the CO2 consumption rate is approximately twice that in the lower reaches; this can be attributed to active physical denudation in steep mountainous areas which increases the surface area for water–rock interactions. The total CO2 consumption obtained by combining each season and basin was 48‒70 × 109 mol/a and 148‒159 × 109 mol/a for silicate and carbonate weathering, respectively, which are almost half the values of previous estimates. Our results suggest that seasonally and spatially separated evaluations are important for generating estimates of chemical weathering in large Himalayan rivers.
KW - Carbon cycle
KW - Chemical weathering
KW - Mekong river
KW - Seasonal variation
KW - Spatial variation
UR - http://www.scopus.com/inward/record.url?scp=85084128503&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85084128503&partnerID=8YFLogxK
U2 - 10.1007/s10498-020-09374-y
DO - 10.1007/s10498-020-09374-y
M3 - Article
AN - SCOPUS:85084128503
SN - 1380-6165
VL - 26
SP - 137
EP - 159
JO - Aquatic Geochemistry
JF - Aquatic Geochemistry
IS - 2
ER -
