Voters in 38 of the largest cities in the United States will go to the polls today to elect mayors, and four states will conduct referenda on national issues as diverse as pornography, geothermal and solar energy, and instant Election Day registration.

While unlikely to produce any significant political trends or be remembered as a fateful moment for the nation, Election Day this year across America promises to deliver its share of singularities and footnotes to history.

Black candidates who won dramatic primary victories in major cities are trying to gain control of municipal governments by reversing racial voting patterns that have been set for years.

Voters will pass judgment on the youngest mayoral aspirant of a major city - in Cleveland - and the oldest incumbent in terms of length of service - in Albany.

Some city hall regimes have already been ousted in bitterly fought primaries, and some other mayors are leaving office voluntarily, paving the way for political newcomers.

In any case, issues that seem parochial and abstract when viewed from afar will be decided amidst intense political passion by the only electorate that counts - the local one.

Two states - Virginia and New Jersey - will elect governors in this off-year, in which most local races have been dominated more by personalities than by substantive issues.

Of the nation's 35 largest cities, 10 will hold mayoral elections. Only three races involve incumbents - those in Detroit, Pittsburgh and Minneapolis.

Primary focus today will be on New York City, where Mayor Abraham D. Beame was eliminated in a primary runoff by Rep. Edward Koch (D-N.Y.). Koch is heavily favored to defeat three opponents in the general election, including Liberty Party candidate Mario Cuomo and Republican state Sen. Roy Goodman, who is given little chance of splitting the vote and slipping into Gracie Mansion the way John V. Lindsay did in 1965.

Elsewhere, there are some political innovations and curiosities.

Detroit will be the first major American city to match a black against another black in a general election runoff.

Incumbent Coleman A. Young, elected the city's first black mayor in 1973, is heavily favored against Councilman Ernest C. Browne Jr. to retain control of the nation's fifth-largest city.

Detroit is 60 per cent black, and Young has charged Browne, who received 5 per cent of the black primary vote, with pandering to white voters. Browne, in turn, vowed to fight Young for every black vote in the city.

In heavily Italian-Slavic, blue-collar Buffalo, Arthur O. Eve, a militant civicl rights leader who once tried to have then-Gov. Nelson A. Rockefeller impeached, is a strong favorite over his Republican and Conservative Party opponents.

Eve, a state assemblyman, would become New York state's first black mayor.

Seattle's runoff contest is a battle between two neophytes who survived a 15-candidate open primary to run for the seat vacated by retiring Wesley C. Uhlman, one of the nation's best known big-city mayors.

Charles Royer, a former television newsman, argues that his 15 years in journalism taught him how government works, while his opponent, Paul Schell says his two years' experience in "the trenches" of a community development program gives him the edge in municipal know-how. Both are liberal Democrats.

In Albany, N.Y., the longest surviving political dynasty in America is seeking to extend its tenure another term.

Erastus Corning II, 67, who has been major since 1942 and presides over a Democratic machine founded 55 years ago by his mentor, Daniel P. O'Connell, is a shoo-in for his 10th term. Corning's token Republican opposition is E. Michael Roberti, a college teacher.

If voters in Minneapolis are experiencing a feeling of deja vu, it is understandable.

Mayor Charles Stenvig and former mayor Al Hofstede, who have been fighting political wars against each other for years, are competing for the mayor's job once again.

Stenvig, a former police office who often says that "God is my helper" and is again campaigning for re-election on a tough law-and-order theme, has been elected every two years since 1969, except in 1973 when his tenure was interrupted by Hofstede.

Hofstede is the candidate of the Democrat-Farmer-Labor Party and a political associate of Sen. Hubert H. Humphrey (D-Minn.). Stenvig is running as an independent this time.

No matter who wins in Cleveland's election, he will become the youngest big city mayor in the nation.

Republican Mayor Ralph Perk was defeated in Cleveland's open primary, and he will be replaced by either of two young Democrats, state Sen. Edward Feighan, 30, or Municipal Court Clerk Dennis Kucinich, 31.

In Pittsburgh, maverick Democrat Richard Caliguiri, who was appointed acting mayor when Peter Flaherty left city hall to take a top Justice Department post, is expected to win on the independent line against Allegheny County Commissioner Thomas J. Foerster, who won the Democratic primary.

Opposing them in a traditionally wide-open Pittsburgh mayoral election will be City Treasurer Joseph Cosetti, who drew little support in the primary as a Democrat and then switched his registration to the Republican Party 13 minutes before the filing deadline.

The election today in Hoston looks as if it may determine nothing more than which of 12 candidates will be forced into a December runoff to succeed retiring Mayor Fred Hofheinz, a chief spokesman for burgeoning Sun Belt cities. Recent polls show that none of the 12 candidates has more than 18 per cent support.

Politicians will be watching several referenda that may reflect on a national scale voter sentiment on various issues.

Attention has focused on a vote in Ohio to repeal the state's recently enacted election day registration law which is a copy of President Carter's moribund plan to allow voters to register at the polls the same day they vote. The Carter plan died in the House earlier this year, and the outcome of Ohio's referendum may help determine if congressional leaders will try to revive the issue in 1978.

Other referenda with national implications:

Washington State: A strong anti-pornography measure which would effectively ban all adult bookstores and movie houses. If passed, the measure would undoubtedly face a court challenge on constitutional grounds.

Oregon: A constitutional amendment to establish a $400 million program for development of nonn clear energy resources, including hydroelectric, geothermal and solar energy. Last year, Oregon voters defeated a referendum designed to prohibit nuclear power development in the state.

North Carolina: Voters will decide whether to allow their governor to serve two consecutive terms, a decision that could continue a national trend toward allowing gubernatorial succession. Similar referenda has been defeated in only one of the 14 states that have recently voted on the issue.

Pittsburgh: Voters in steel industry Allegheny County will decide whether laws intended to curb pollution should be restricted in order to save jobs.The question to be voted upon, which some politicans have labeled a choice between air and water quality or employment. [WORD ILLEGIBLE]

"Should county and municipal elected officials fight to change federal environmental laws in order to preserve existing jobs in the steel industry."

The question has been attacked as meaningless and misleading by environmentalists and labor unions.