Fairfax County Supervisor Warren I. Cikins yesterday became the second liberal Democrat on the county board to announce that he will not run for election this fall

Cikins, a first-term supervisor who represents the racially mixed Mount Vernon District, said he will not run because his responsibilities as supervisor take too much time away from his family and his full-time job as asenior staff member at the Brookings Institution.

Supervisor Alan H. Magazine, who represents Mason District, announced last week that he would not seek reelection because he was tired of having too little time for himself or his family.

Cikins and Magazine are the only two supervisors on the nine member board who hold what Cikins yesterday described as "regular 9-to-5 jobs," Cikins said it was a fiction that the supervisor's job is a part-time one.

"It will certainly tax the ingenuity of the Board and the (Virginia) General Assembly to find an answer that will enable persons of Alan's and my status to serve without undue hardship," Cikins said. He said the $15,000-a-year salary now paid supervisors would have to at least double before he could afford to give up his job at the Brookings Intitution, which he said pays about $35,000 a year.

Cikins, 48, who has master's degrees from Harvard in public administration and political economy, said he is worried about the balance of backgrounds on the board with the departure of himself and Magazine. He said the board needs the outlook of people who have full-time jobs.

Commenting on Cikins' and Magazine's announced retirement, Supervisor Amrtha V. Pennino (D-Centreville) said she hated to see them leave, but added that praise should go to those supervisors, such as herself, who choose to remain in office.

Pennino said that coping with the responsibilities of being a supervisor, while at the same tiem taking care of a husband and children, is extremely difficult. She referred to herself and supervisors Audrey Moore (D-Annandale) and Marie B. Travesky (R- Springfield) as "superwives."

Cikins, who calls himself a student and lover of history, said yesterday that "to stay in character" he chose to quote and identify with an "historic personage" -- King Edward VIII, Duke of Windsor, who abdicated the throne in 1936.

"You must believe," Cikins paraphrased the king, "when I tell you that I find it impossible to discharge my duties as supervisor as I would wish to do without the help and support of the woman and children I love." Cikins has two boys, ages 12 and 9.