Soil Atterberg limits of different weathering profiles of the collapsing gullies in the hilly granitic region of south China
Yusong Deng1, Chongfa Cai1, Dong Xia2, Shuwen Ding1, and Jiazhou Chen11Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River) of the Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, People’s Republic of China 2College of hydraulic and Environmental engineering, China Three Gorges University, Yichang 443002, China
Received: 07 Nov 2016 – Accepted for review: 07 Dec 2016 – Discussion started: 09 Dec 2016
Abstract. Collapsing gully erosion is one of the most serious natural hazards in the hilly granitic region of south China. However, few studies have been performed on the relationship of soil Atterberg limits with soil profiles of the collapsing gullies. Soil Atterberg limits, which include plastic limit and liquid limit, have been proposed as indicators for soil vulnerability to degradation. Here, the soil Atterberg limits within different weathering profiles and their relationships with soil physico-chemical properties were investigated by characterizing four collapsing gullies in four counties (Tongcheng County, Gan County, Anxi County and Wuhua County, labeled as TC, GX, AX and WH, respectively) in the hilly granitic region of southern China. The results showed that with the fall of weathering degree (from surface layer to detritus layer), there was a sharp decrease in plastic limit, liquid limit, plasticity index, soil organic matter, cation exchange capacity and free iron oxide, a gradual increase in liquidity index, a sharp increase in particle density and bulk density followed by a slight decline, as well as a decrease in the finer soil particles (silt and clay), a noticeable decline in the clay contents, and a considerable increase in the gravel and sand contents. The plastic limit varied from 19.43 to 35.93 % in TC, 19.51 to 33.82 % in GX, 19.32 to 35.58 % in AX and 18.91 to 36.56 % in WH while the liquid limit varied from 30.91 to 62.68 % in TC, 30.89 to 57.70 % in GX, 32.48 to 65.71 % in AX and 30.77 to 62.70 % in WH, respectively. The soil Atterberg limits in the sandy soil layers and detritus layers were lower than those in the surface layers and red soil layers, leading to the loss of bottom soil layers, the collapse of upper soil layers and finally the occurrence of collapsing gully erosion. The regression equation showed that soil Atterberg limits had significant and positive correlation with SOM, clay content, CEC and Fed, significant and negative correlation with sand content and no obvious correlation with other properties. The results of this study revealed that soil Atterberg limits are an informative indicator to reflect the weathering degree of different weathering profiles of the collapsing gullies in the hilly granitic region.
Deng, Y., Cai, C., Xia, D., Ding, S., and Chen, J.: Soil Atterberg limits of different weathering profiles of the collapsing gullies in the hilly granitic region of south China, Solid Earth Discuss., doi:10.5194/se-2016-152, in review, 2016.