From a reader:
Here’s a transcript from Nova (on PBS, of all places) about the volcano in the Congo. The pertinent portion (about a fourth of the way down) says:
NARRATOR: The satellite identifies the gas as sulfur dioxide, SO2, the primary cause of acid rain. And Nyiragongo is producing more than any place in the world, up to 50,000 tons per day. That’s more than the amount produced by all power plants, factories and cars in the United States. And the high concentration of SO2 is another clue for forecasting the next eruption.