The following questions are designed for longer, more comprehensive responses. Synthesize information from across the source document to construct your arguments. Answers are not provided.

1. Discuss the evolution of acid rain research from the early work of Robert Anges Smith in 1872 to the massive National Acid Precipitation Assessment Program (NAPAP) in the 1980s. What key findings and hypotheses drove the surge of interest in the topic during the 20th century?
2. Using the spatial pattern maps (Figures 2-6) and associated text, analyze and explain the geographic distribution of sulfate, calcium, and pH across the United States. How do the patterns of acidic anions and basic cations interact to produce the observed national pH pattern?
3. Explain the chemical equilibrium model used to calculate precipitation pH from ion concentrations. What is the role of the “Net Ions” quantity in the calculation, and how do factors like temperature and atmospheric carbon dioxide concentration (Pco₂) influence the final pH value?
4. Evaluate the challenges associated with establishing and maintaining a scientifically rigorous precipitation monitoring network. Discuss the importance of site selection, sampling mode (e.g., bulk vs. wet-only), sample handling, and a comprehensive Quality Assurance/Quality Control program.
5. Analyze the temporal trends of acid rain in the United States. Cover the difficulties in interpreting historical data, the seasonal patterns identified by researchers, the long-term trends observed in the NADP/NTN data from 1980-1992, and the measurable impact of environmental legislation.