森林立地学会誌 森林立地37(1). 1995. pp. 9〜18
論 文
中国北西部の乾燥地における水の塩類濃度
斉 藤 昌 宏・谷 本 丈 夫
1993年の8月, 9月にタクラマカン砂漠北部および西部で，1994年9月に河西回廊で調査を行い，各オアシスの飲用水，河川水，地下水の電気伝導度を測定した。ほとんどのサンプルが電気伝導度で0.3mS／cmを超え，硬水であった。ただし，飲用水の中で最も電気伝導度の高いアラルのサンプルでも3.5mS／cmで，飲用の許容限界値4.7mS／cm以下であった。山間地を流れる河の水は概して電気伝導度が低く，タリム盆地に流れ込むと蒸発量が急に高まるため塩類の濃縮が激しくなることが示唆された。塩類濃度の高まりは蒸発作用だけでなく，低山丘陵地では地質年代に形成された含塩層が露出している地域を流れる間に，また，低地では塩類集積地の表層あるいは地下を流れる間に急激に起こることが推測された。一般的に塩類濃度は総可溶性固体量（TDS）で示され，WHOの水質基準もこれによって表されている。溶存する塩類の組成は水系によって異なるため，総可溶性固体量と電気伝導度の間には緩やかな回帰式しか求められないが，両者の関係式を用いて水質の基準を電気伝導度に換算し，両地域で得たサンプルの水質を評価した。この結果，少数のサンプルを除外すれば，ほとんどの水で耐塩性の作物に潅漑を行うことが可能と判断された。
Masahiro
SAITO and Takeo TANIMOTO: Water salinity
in northwest China
The salinity of many kinds of water was
studied in arid areas of northwestern China. Although values for total
dissolved solids (TDS) are usually used for estimating salinity, we mainly used
simpler electric conductivity (EC) method. EC values were obtained for about
sixty samples of water collected from various places in the Taklimakan Desert
and the Hexi Corridor in the summers of 1993 and 1994. Samples of drinking
water (tap water) from various oases, river water (excluding that from high
mountain areas) , and groundwater were classified as hard water because their
EC values were all over 0.3 mS/cm. However, even the two samples of drinking
water collected at Alaerh which had registered the highest salinity (3.5 and
2.98 mS/cm on EC), were still below the maximum level for potability. Samples
of river water from high mountain areas were usuauy low in salinity, though
salinity in samples from areas farther downstream gradually increased. High
salt concentrations are probably caused not only by intense evaporation in the
arid environment , but also by the dissolution of salt in water which traverses
ancient saline layers or flows through lowland areas where salt has
accumulated. The World Health Organization (WHO) and United States Public
Service (USPS) has recommended saline water levels, which are usually expressed
in terms of TDS. Since the constitution of saline solutions differs among
hydrological systems, it could only be obtained by a loose regression formula
between TDS and EC. Using this formula、water quality was converted into terms of EC and
evaluated for the region. As a result, with a few exceptions, we determined
that it would be possible to use most of this water to irrigate salt-resistant
crops.