An idea that may be too removed from the general field of expertise here. For those who live in suburbs (and have gardens/front yards/...), look at your weeds. Some of them, like Conyza canadensis (incidentally, a very aggressive alien in Europe), may hyperaccumulate certain substances (in this particular case, Hg, Pb, As and some other things you don't want in your food beyond micro levels). If you leave them to grow until just fruiting and then take out with roots, you will reduce pollution there (and the aliens' spread). However, you will need to put them somewhere, which may be inconvenient.
you will reduce pollution there
While technically true, will it make any difference? How much heavy metals (e.g. in mcg) would one plant accumulate? How many plants will it take to reduce the heavy metal pollution of a patch of ground by, say, half?
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.