The study looked at how acid rain affects the levels of copper (Cu) and lead (Pb) in soil. By spraying different levels of simulated acid rain on a vegetable field, the researchers found that as the soil became more acidic, the levels of available Cu and Pb increased. Cu moved deeper into the soil layers, while Pb stayed mostly in the middle layer. Over time, Cu levels decreased while Pb levels increased, suggesting Cu may move into groundwater and pose a threat, while Pb may accumulate in soil and be taken up by plants, posing a risk to food safety.