The study analyzed soil samples from different parts of Scotland to understand the sources of lead contamination. They found that lead concentrations were higher in the top soil layers compared to the bottom layers. The lead in organic soil layers mostly came from human activities, while in mineral soil layers, it was a mix of human-made and natural lead. The researchers also discovered that the northern part of Scotland had more radiogenic lead in the soil compared to the south, indicating different sources of contamination. Overall, the study showed that long-range transport of lead from human activities has significantly impacted the soil in Scotland.