Soil in the city I live in is quite often contaminated with nasty things like arsenic and lead. Levels are sometimes twice or more what's considered acceptable. For this reason, people usually garden in imported soil in raised beds rather than directly in their own backyards.
I'm wondering how risky it would be to use leaves (most commonly maple) from untested soil as mulch or as bedding for vermicomposting worms. Would different varieties of trees be more/less likely to deposit contaminants in their leaves?