In an atmosphere clouded by the city's financial crises, legal complexities, interunion rivalries and the inexperience of the participants, the District of Columbia government has embarked for the first time on collective bargaining over the wages and working conditions of its employes.

The negotiations, now in their preliminary stages, will determine the salaries of about 30,000 workers for the next three years. For the cash-strapped, deficit-ridden city government and public schools, the negotiations are a major step toward the establishment of fiscal home rule.

But they come at a difficult time: Mayor Marion Barry knows that the wage settlements will commit the city to pay more money that it has.

For the workers, the negotiations represent a chance to regain a treasured asset that they lost for the first time this year -- parity in pay and benefits with their counterparts in the federal service. Until this year, D.C. employes received the same annual pay increase that federal workers received, but with home rule they have been severed from the federal pay scale.

Last September, when federal workers received cost-of-living increases of 9.1 percent, Barry gave city workers only 5 percent, which he said was all the city could afford.

Separate negotiations between the city and its firefighters, police and teachers are expected to be the most crucial because they represent the most workers. As a result, the pay increases they receive starting Oct. 1 will likely set the standard for the other groups, which include nurses, sanitation workers, water and sewer employes, clerks, doctors, librarians and social workers.

Tough negotiations over wages and working conditions have long been part of the political landscape in other cities. The recent history of New York especially has been marked by dramatic confrontations between mayors pleading municipal poverty and pugnacious union chiefs like the late Michael J. Quill, a transport union leader, proclaiming their contempt for the politicians and their determination to strike.

In Washington, such espisodes have been rare, until now. The portent for a long summer of confrontation may have been set, however, in an early round of the talks between the police department and the International Brotherhood of Police Officers. The negotiations broke off in an angry clash between union president Lawrence Simons and the police labor relations chief, Inspector Bobby Wallace.

The union declared the talks at an impasse, a prelude to giving up bargaining and seeking arbitration, and the city responded by filing an unfair labor practice charge, accusing the union of refusing to negotiate.

Donald Weinberg, Barry's labor relations director, said it was "a little early to declare an impasse," especially since the police negotiations had not even reached the issue of wages. "We're not mad at anybody. We'd like to resume."

Simons however, pointed out that it might be to the union's advantage to gamble on arbitration. Police officers in some suburban jurisdictions have recently won pay increases greater than the District is likely to give in a negotiated settlement, and an arbitration panel might use those contracts as precedent.

The negotiations are being conducted under the terms of the city's 1978 "Merit Personnel Act." The law runs 354 typewritten pages and was intended to regulate every aspect of labor relations of municipal workers. But its very complexity has created obstacles for the unions and for the city's negotiators as they set out on the arduous path to new labor contracts.

The law resulted in the creation of bargining units for the workers that include more than one union -- all nurses on city payrolls, for example, are grouped together as a bargaining unit, though they are not all members of the same union and their unions do not necessarily agree on the issues. The law also left unclear or ambiguous some critical terms and processes. The example most frequently cited by union officials is that the law sets out conditions for bargaining over "compensation," but does not define the term.

"I anticipate some difficulty in determining what is compensation, especially when multiple unions are in a bargaining unit," said Donald McIntyre, national vice president of the American Federation of Government Employees. "What about uniform allowances, or the cost of reproducing the contract? Since this is the first time we're going at it under this law, we're going to have to be very creative."

Hanging over the negotiations is the uncertainty about the outcome of a court case that could affect the entire process. The Dictrict's Public Employee Relations Board, which was created by the Merit Personnel Act, ruled that Barry was required to negotiate with the unions over wage scales for the current year, as well as for next year. Barry declined, saying it was too late in the budget cycle, and appealed the ruling to D.C. Superior Court.

Judge James A. Belson is expected to rule within the next two weeks on whether the city is obliged to bargain retroactively for 1981 or whether, in the absence of bargaining, city workers were entitled to the same pay raise as federal workers received.

A ruling in the unions' favor on either point would be a devastating blow to Barry's attempts to balance the city's budget and begin paying off a cumulative deficit. Barry's budget director, Gladys Mack, calculated that the difference between the cost of a 5 percent increase and the cost of the 9.1 percent the unions were asking would be almost $29 million, which the city does not have. More than 4,300 workers would have to be cut from the payroll to give the increase to those who remained, she said.

If Belson upholds the city government, the 5 percent increase will stand and will become the base to which the increases for the next three years will be added. Barry's budget for the 1982 fiscal year, which begins Oct. 1, contains only enough money for an increase of about 2 percent, but he has acknowledged that the workers will have to receive more than that. The question is where the extra money will come from.

Mack has calculated that each percentage point of salary increase for all city workers, including school teachers and staff of the University of the District of Columbia, costs the city about $8 million. Therefore an 8 percent increase in October, which some labor experts say is the minimum for which the unions will settle, would cost about $64 million, but there is only $16.8 million for wage increases in the budget. Barry has said that he hopes to use a $36-million increase in the annual federal payment to the District, which Congress is now considering, to defray the cost of the salary settlements, but even if that is approved it may not be enough.

The workers are represented by 15 separate bargaining units. Some of them negotiate with the school board and UDC, the others with Weinberg and his staff. Some of the units represent different groups of workers affiliated with different unions, which do not always stress the same issues.

"They tried that before in other places and it didn't work," said Karen Fennell, chief negotiator for the D.C. Nurses Association.