Basically, I am a animal nutritionist, not plant scientist or plant breeder, though my research area also included maize crop as forage. Maize is a C4 plant and it has capacity to utilize environmental Co2 and  Carbon sequestration in the soil. Naturally,  if the soil is contaminated with heavy metals, where any type of plant or forage is grown, it would intake higher amount of heavy metal compared to normal soil. But   I have gone through literature i couldn't find such characteristics of maize, there are some floating plant like Pistia they  have the capacity to accumulate more heavy metal. So, you go through literature for further reading and you can talk to a plant breeder.         '