arsenic falavoured spuds - yum ;-)

They already contain a fair bit in their skins.

If you are referring to the fact that you shouldn't eat green potatoes
then the poison is not arsenic. The poison is actually and alkaloid
called solanine. The green is actually chlorophyll but it is a good
indication that the potato has produced solanine as well. Solanine is
very poisonous but fortunately present in small quantities even in very
green potatoes (you could eat a green potato and not die). The, I
suppose, positive aspect of solanine is that it is very bitter, as most
alkaloids are, so you wouldn't want to eat it anyway. Deep peeling a
green potato will remove all the solanine as it is only present in the
skin and just below.

As for arsenic, plants will take it up into their leaves and fruit to
some extent if there is any in the ground and some plants are better at
it than others. However, if there isn't arsenic in the ground then there
wont, in fact can't, be any in the plant.

Graham