Leaching of simulated acid rain deteriorates soil physiochemical and mechanical properties in three agricultural soils

Abstract

Acid rain is a long-standing environmental issue that affects ecosystem properties. Great attempts have been made to clarify how acid rain affects soil physiochemical and microbial properties, but soil mechanical properties in response to acid rain conditions have rarely been investigated. This microcosm experiment was conducted to study how simulated acid rain (SAR) with different acidity levels would affect soil mechanical properties and the associated physiochemical indicators of three agricultural soils (Humic Acrisol, Haplic Ferralsol and Rhodic Ferralsol) with different soil properties. The results showed that the soil plasticity index was significantly decreased by the strongly acidic SAR treatments (pH < 3.5) for all the three soils, while the soil penetration resistance was not significantly changed by any of the SAR treatments. Correlation and multiple linear regression analyses suggested that sand content with negligible changes under the SAR treatments contributed substantially to the stable soil penetration resistance. Furthermore, we observed that in comparison to the other two soils, the Haplic Ferralsol appeared to be more vulnerable to acid rain. Such a high sensitivity of the Haplic Ferralsol to the acid rain treatments might have been associated with its relatively poor soil structure and quality, which were indicated by a high sand content and low soil organic matter content. These results suggest that in comparison to high-quality soils, low-quality soils may have experienced greater stress under acid depositions, and the results highlight the necessity of studying in situ how soil mechanical properties would change under acid rain scenarios.