Evaluation of Critical Sulfur Loads based on Weathering Rate Modeling in Three Gorges Reservoir Area, China.

Evaluation of Critical Sulfur Loads based on Weathering Rate Modeling in Three Gorges Reservoir Area, China.

This study developed a new empirical model to reduce the number of parameters required to assess the weathering rate and to facilitate its accurate calculation. The critical loads of sulfur were assessed based on the weathering rate calculated using the empirical model. Seven types of soil were studied in five districts of the Three Gorges Reservoir Area, i.e., yellow soil, rice soil, purple soil, yellow brown soil, yellow rendzina, brown soil, and yellow-red soil. A PROFILE model combined the soil properties to perform a regression analysis and filter appropriate parameters for establishing the empirical model. Finally, the silt and pH levels were selected. The weathering rates varied from 0.27 to 2.21 keq ha- 1 yr-1 in the empirical model. The coefficient of determination was relatively high (R2 = 0.653) for the weathering rates obtained using the empirical model and the PROFILE model test. Thus, the empirical model could predict the weathering rates better in the study area. The critical loads of sulfur were relatively high and ranged from 2.35 to 4.83 keq ha-1 yr-1 based on the weathering rates calculated using the empirical model. Compared with other acid rain areas, the risk of soil acidification is relatively low in this region. However, we should remain aware of the harmful effects of acidic substances.