Symptom of Environmental Change in Siberian Permafrost Region, Eds. Hatano R and Guggenberger G, p 129-134, Hokkaido University Press, Sapporo, 2006 Surface water chemistry in a continuous permafrost region, Central Yakutia, Eastern Siberia Osamu Nakahara 1,* , Fumiaki Takakai 1 , Alexey R. Desyatkin 2 , Ryusuke Hatano 1,3 , and Roman V. Desyatkin 2 1 Graduate School of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo 060-8589, Japan 2 Institute for Biological Problems of Cryolithozone, Siberian Branch, Russian Academy of Science, Lenin Ave. 41, Yakutsk 677980, Russia 3 Field Science Center for Northern Biosphere, Hokkaido University, Kita 11 Nishi 10, Kita-ku, Sapporo 060-0811, Japan * Corresponding author: nakahara@chem.agr.hokudai.ac.jp 1. INTRODUCTION One of distinct features of the ecosystems of central Yakutia, eastern Siberia, is the abundance of thermokarst depressions called "alases," which form by thawing of the upper part of the continuous permafrost. Alases range from several meters to more than 20 m in depth, and in area they range from less than 1 ha to more than 500 ha. Central Yakutia has about 16 000 alases, covering a total area of about 44 million ha (Fedorov and Konstantinov 2003). While many alases are covered by grassland, with or without small ponds, some alases contain sizeable lakes. Another feature of this region is the accumulation of soluble salts in soils and their high alkalinity (Desyatkin 1993, Lopez et al. this volume). The very low annual precipitation of 230 mm and continuous permafrost in central Yakutia inhibit the leaching of soluble weathering products, causing the soils to be highly saline and alkaline. Alases in particular accumulate substantial amounts of salts that had been stored in the permafrost (Desyatkin 1993). This study's aim was to characterize the surface water chemistry in central Yakutia. 2. STUDY AREA AND METHODS The study area was in central Yakutia (Fig. 1). The annual mean temperature in Yakutsk (62˚05'N, 129˚45'E) is –10 ˚C, and the annual mean precipitation is 230 mm. The soil parent material in the study area is composed mainly of Upper Pleistocene to Holocene alluvial deposits. In summer 2005 (17 July to 5 August), 33 water samples were collected from tributaries of the Lena and Aldan rivers, and six water samples were collected from alas lakes (Fig. 1). Total dissolved nitrogen (TDN) was determined by the method of alkaline persulfate digestion with HCl-acidified UV detection. Anions (NO 3 – , Cl – and SO 4 2– ) and metal cations (Na + , K + , Ca 2+ and Mg 2+ ) were determined by ion chromatography (QIC Analizer; Dionex, Sunnyvale, CA & ICA-2000; DKK-TOA, Tokyo, Japan). NH 4 + was determined by colorimetry using the indophenol blue method. Dissolved organic nitrogen (DON) was calculated by subtracting dissolved inorganic nitrogen (DIN, NO 3 – + NH 4 + ) from TDN. Total dissolved C and inorganic C were determined with a TOC analyzer (TOC-5000A; Shimadzu, Kyoto, Japan), and dissolved organic carbon (DOC) was calculated by subtracting inorganic C from total dissolved C. pH was measured with a glass electrode.