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Dobbie: Hi, Roger.
Roger: Debbie! Hi. I haven't seen you all week. How are you?
D: Oh ... I've been struggling with my Natural Earth assignment. We did our presentation last week on dangers to the environment, but the essay is proving to be a lot more difficult.
R: The one for Professor Black? Me too. I'm writing about volcanic activity. What are you doing yours on?
D: Acid rain. I thought that would be OK, but the process is really complicated.
R: Well, I can help you with that! I know quite a lot about acid rain. I studied the causes and effects last year.
D: Really?
That's great sulphur dioxide from power plants and smelters. Basically, this reacts in the atmosphere to form acid rain.
R: Ah. but it's not just sulphur dioxide, it's also nitrogen oxides.
D: Really?
R: Yes, from things like car exhausts.
D: But aren't nitrogen oxides also caused by natural events like fires, volcanoes, lightning, too?
R: Yes. They're a minor factor, but I still think they're worth mentioning. But, sorry, carry on ...
D: Thanks. I might add that. So anyway, these emissions react in the atmosphere with water, oxygen and oxidants to form acidic compounds like sulphuric acid. These compounds then fall to earth.
R: Are you going to mention the different ways they return to the ground?
D: Do you mean wet and dry deposition?
R: Yes! So, you've done a bit of background reading, then?
D: Yes ... so if I've got it right, acid rain often comes down as rain, but also as snow or fog. This is wet deposition. I'm going to define it as any form of precipitation that removes acids from the atmosphere.
R: Yes, I think that's a good term to define it.
D: Dry deposition. .. Well. I think that's when the pollutants stick to the ground through dust. I'm not really sure of how to define it though, compared to wet deposition.
R: Just think of it as any pollutants that are not caused through precipitation. That's probably the best way. Did you know that sunlight can enhance the effects of acid rain as well?
D: No, I didn't. There is just so much to think about. I'm sure l'll go over my word limit.
R: Well, you sound like you know a lot about the subject. Just try and keep your focus. I've had the same problem writing about volcanoes! There is just so much!
