No. The bombs were detonated very high above the ground. This means that while there were radioactive effects on the ground, they were primarily in the form of "prompt" radiation. Think of it as one big blast of radiation that lasted far less than a second. Now this radiation does have the capability of making things it touches radioactive (the phenomena is known as artificial radioactivity), but generally speaking it doesn't make very long-lived radioactive things. It is a hazard to living things primarily in its first moments and maybe a few hours after the attack, but not in the long term.

The more long-lived radioactive contamination one thinks of with regards to nuclear weapons is the result of fallout, which are the by-products of the explosion itself. When the fireball of a nuclear weapon touches the ground it can mix with dirt and debris. This "weighs down" the fallout particles and causes them to fall relatively soon back to Earth, depositing a lot of radioactivity in a relatively small area. When the fireball is detonated far above the surface, however, the particles stay hot and light and disperse over thousands of square miles before falling back to Earth. So no part of the ground gets very much radioactivity as a result. This was the situation in Hiroshima and Nagasaki.