Mayor-elect Andrew Young, who swept into City Hall Tuesday on a tide of racial bloc voting, now faces his first crucial task--dousing the racial bitterness generated in the mayoral election runoff's final days.

Young, the city's second black mayor in history, was up at dawn and on the streets this morning to shake hands with sleepy workers at a rapid transit station.

"I would hope that most of the polarization and the hostility was in the press and that it really does not exist in this city nearly to the extent we thought it does," Young said.

"The campaign has put a strain on it racial harmony , but I think we've gone through that strain and there have been no broken relationships and there will be none in the future," said a subdued Young, who rose to prominence with Dr. Martin Luther King Jr., in the civil rights movement and then served as ambassador to the United Nations.

He then pledged a new era of "peace and harmony."

In a heavy turnout, Young defeated Sidney Marcus, a liberal white state legislator, with 55 percent of the vote to Marcus' 45 percent, a pattern that virtually mirrors the voter registration of blacks and whites in the city.

Marcus, a veteran state legislator who enjoyed biracial support, was annointed by the white business establishment which searched two years for a white candidate to recapture the mayor's job after eight years under a mayor they viewed as their nemesis, Maynard Jackson, the city's first black mayor and a strong Young supporter.

Marcus' black supporters sniped at Jackson for meager accomplishments and asserted that a white mayor would be better able to work with rural legislators and produce more jobs for poor blacks. Jackson exploded. He labeled them "shuffling, grinning . . . Negroes" in a carefully crafted speech that lit the fuse on racial feelings and set the tone for the runoff.

Local newspapers' analysis of key precincts showed a slight increase in Marcus' black crossover vote from the general election, a result attributed to some "blacklash" against Jackson. In Young's home precinct, Marcus got 17 percent of the vote--up from 14 percent in the general election three weeks ago, a pattern reflected in several black precincts.

Young slipped from 12.4 percent of the overall white vote to 10.6 percent, which also was attributed to black leaders' attacks on Marcus.

Yet some read the results with optimism.

"In spite of all the provocation, more than 10 percent of each race picked the other guy and that's fairly healthy," said Atlanta Constitition political editor Frederick Allen. "The bottom line is that blacks are a majority of the registered voters."

Young's first test as a veteran civil rights leader turned mayor-elect comes in two weeks when he sits down with white business leaders to receive a task force report by Central Atlanta Progress, a coalition of downtown businessmen. The report contains their proposals for police protection, economic development, transportation and human services.

Charles Loudermilk, a white businessman who abandoned the pack to work as Young's treasurer, maintains that pro-business policies at city hall will produce prosperity for business and jobs in the black community. This is one way to heal the wounds from the bitter mayor's race and perhaps stem white flight, he says.

"The worst thing that could happen would be for Atlanta to become an "all-black city," he says. "The business community has the economic power and needs the suppport of City Hall. The black community has the political power and needs the business community to provide jobs . . . . We've got to give Andy Young a fair chance."