Bq: the abbreviation for Becquerel, which is defined as one disintegration per second and is a measure of the amount of the radioactivity.
Bq m-3: Becquerels per cubit meter, a measure of the radioactivity per unit volume, that is a concentration.
FDNPP: Fukukshima-Daichi Nuclear Power Plant
Half-life: the time it takes for the radioactivity associated with a specified isotope to fall to half its original value
PBq: the abbreviation for Peta Becquerel equal to 1015 Bq, that is one thousand trillion which is the same as a million billion.