This is the 6685th most frequent Russian word.
pdk
"PDK" in Russian is an abbreviation for "предельно допустимая концентрация," meaning "maximum permissible concentration."
Here, the root 'подк' is part of the verb 'подкрепитесь' (have some food), derived from 'подкрепить' which means 'to support or reinforce oneself by eating'.
Подкрепитесь перед дорогой, ведь путь будет долгий.
Have some food before the journey, as it will be long.
In this sentence, 'подк' serves as part of the word 'подконтрольные' (under control), indicating a level of supervision.
Подконтрольные территории должны подвергаться периодическим инспекциям.
Subordinated territories should undergo periodic inspections.
The root 'подк' in 'подкреплений' refers to reinforcements, stemming from the concept of 'supporting or strengthening'.