I've done the 'search' for you right here in this forum. As you can imagine, this topic comes up all the time and has been answered backwards, forwards, upside down, rightside up, and inside out! lol. I'd suggest that you sit down and do a little reading of some of these very interesting past threads, and then see if you have further questions to ask.

You will soon realize that 'dirt' is not 'dirt' is not 'dirt'. ;-)

Here is a link that might be useful: Search the Container Forum

My thought on the soil question is what are you going to do with it. 70 years ago my mother had some beautiful plants in pots filled with soil or dirt from the garden, so now there are different mixes of a lot of different things and it is soil. I use my own mixture trying to keep it light in weight but good for the plant. So far I am having good luck with my garden and a lot of fun. About teapot100 worrying about being too close to the highway, dont worry about it just think about those vegetables you bought in the store and what kind of "DIRT" they were grown in. Just a thought.