Welcome to visit Geoscience!

Geoscience ›› 2022, Vol. 36 ›› Issue (02): 462-473.DOI: 10.19657/j.geoscience.1000-8527.2021.169

• Water Resources and Environmental Research • Previous Articles     Next Articles

Salt Content Features and Sedimentary Environmental Evolution in Shallow-Level (<100 m) Soils from the Yangtze River Estuary

GOU Fugang1,2(), GONG Xulong1,2, YANG Lumei1,2, ZHANG Yan1,2, LIU Mingyao1,2   

  1. 1. Geological Survey of Jiangsu Province, Nanjing, Jiangsu 210049, China
    2. Key Laboratory of Earth Fissures Geological Disaster, Ministry of Natural Resources, Nanjing, Jiangsu 210049, China
  • Received:2021-08-30 Revised:2021-12-05 Online:2022-04-10 Published:2022-06-01

Abstract:

Soil salinity is an important reference indicator for engineering foundation design and agricultural development. By collecting and analyzing the soil salinity of 907 soil samples from the Yangtze River estuary region, the content of eight ions and pH value of the soil soluble salts were obtained. Accordingly, the study area (<100 m depth) was systematically analyzed in a brine-bearing characteristics of the light soil. The results show that each layer contains 0.028%-1.226% salt. The Holocene land has higher soil salt content with depth, with the maximum and minimum salinity (NaCl) occurring in layer 4-1 soft soil (26 m depth) of the lower Rudong Formation and layer 7-2 sand (81 m depth) of the lower Gehu Formation, respectively. For the latter, the HC03- ion content is the highest, followed by the Cl- and Na+ contents. Deep soil layer (Gehu Formation) has lower salt content, and the amount of viscous soil is generally greater than sand. Earth layer ESR value is higher than local surface freshwater SAR. The ESR maximum is 27.7 times that of the freshwater SAR, whilst the minimum is 2.7 times that of local surface freshwater ESR, indicating that the exchangeable soil Na content is high. Soil salinity (<100 m depth) was largely controlled by the Late Pleistocene transgression and Holocene transgression. The soil salinity comprises mainly NaCl, and the most important salt source is seawater impregnation or soaking. The Pleistocene layers contain terrestrial sediments, and have high salinity due to the Pleistocene and Holocene transgression. The lower and middle members of Rudong Formation are of deltaic facies, which are affected by Yangtze River and transgression, and the soil salinity ranges widely. The Rudong Formation (upper member) comprises continental sediments, and the soil has been widely desalted, with the highest HC03- content. The Cl- content has high corrosiveness in concrete construction, especially for the 4-1 silty clay layer, where the proportion of soils with at least low corrosive grade account for up to 99%, and basic anti-corrosion treatment should be done. The 2-1 and 2-2 soil layers (exposed on the surface) of the upper Rudong Formation are more alkaline, which has high impact on agriculture and engineering construction. It is necessary to add improved agents for soil improvement.

Key words: sedimentary environment, salt characteristic, soluble salt, soft soil, salinization, coastal saline soil

CLC Number: