The researchers studied how acid rain affects soil acidity in paddy fields. They used columns of soil from the Tai Lake region and simulated rain with different pH levels. They found that leaching with acid rain caused a decrease in soil pH and a reduction in soil buffer capacity. This could lead to soil acidification over time. The amount of cations leached out of the soil increased with lower pH levels of the simulated rain. Calcium and potassium were leached out the most, while magnesium was leached out most efficiently. The top layer of soil was most affected by the acid rain, with pH levels decreasing the most in that layer.