Maryland's wealthier counties could do well under provisions of last year's federal tax revision act, but the poorer counties could expect only modest increases, or even face revenue declines, according to a new University of Maryland study.

Montgomery County, the state's wealthiest with one of the highest per capita incomes in the country, could receive a three-year windfall exceeding $53 million, according to the report from the university's Institute for Governmental Service. Also in line for big gains are Prince George's with nearly $32 million, Anne Arundel $20 million and Howard with more than $10 million, the study found.

"At the other extreme, counties such as Somerset, Caroline and Dorchester are estimated to experience only modest increasaes in tax revenues and, by some estimates, may even experience revenue decreases," the report stated.

The General Assembly, however, acted this year to protect the smaller counties, providing a minimum guaranteed revenue provision that allows every county to receive at least $3 per capita in windfall revenue next year. Before this provision was enacted, counties with large populations of low income residents risked revenue losses because the new law increased federal exemptions and standard deductions, eliminating most tax liability for many low-income taxpayers.

The 1986 law also changed many of the allowable uses for tax exempt securities and changed the permissible volume of many types of tax exempt bonds.

One of the changes made it more difficult for governments to finance private activities with proceeds of general governmental obligations, the report stated. Another section changed the way states and local governments could deal with industrial development, student loan and mortgage revenue bonds. The new law combined the various ceilings and limited most private purpose bonds that are still tax exempt.

"The new volume caps are not likely to cause policy problems in Maryland governments during 1987," the report stated, since the state issued only $183 million in these bonds, with a ceiling of $329 million.

"However, current estimates produced by the Maryland Department of Fiscal Services suggest that the demand for housing bonds and industrial development bonds in Maryland could seriously exceed the volume caps in 1988."