Analysis of Spatial Variation of Soil Salinization Using a Hydrochemical and Stable Isotopic Method in a Semiarid Irrigated Basin, Hetao Plain, InnerMongolia, North China

This paper focuses on using data of total dissolved solids and stable isotopes of groundwater to confirm the spatial variation of soil salinization on the Hetao Plain of Inner Mongolia. The results show that soil salt contents, total dissolved solids and stable isotopes in the northwestern Hetao Plain have increased values. This was caused by water sources with large values of total dissolved solids and delta O-18, the rise of the groundwater table, and strong evaporation. However, there was another pattern in the eastern study area. Groundwater samples showed low delta O-18 values and large total dissolved solids values, but salt contents had a checkered high and low distribution. Irrigation from Yellow River water, which is flushing farmland, has increased the salinity of groundwater, but delta O-18 values were relatively small and clearly have reduced soil salt contents in the mid-eastern area. Near Lake Wuliangsu, substantial farmland drainage water with many nutrients have entered the lake through waste canals, and groundwater with increased total dissolved solids values have increased the soil salt content. Some sites showed lower total dissolved solids and delta O-18 values in the central area, revealing that channeled stream water from the Yellow River is the reason of low soil salt contents. A combined method of hydrochemistry and stable isotopes may be advantageous for analyzing soil salinization in a semiarid irrigated basin and for oases of semiarid regions in the world.