The Loudoun County Board of Supervisors signaled its intention Tuesday to hold a $5 million bond referendum on March 12 that would allow the county government to purchase several hundred acres of "sensitive natural areas" in the county.

At least four sites have been identified tentatively as candidates for purchase and preservation, though portions of them would be open to the public for limited recreational uses such as hiking, say county officials and members of a citizens committee that proposed the bond issue. Two potential sites are in eastern Loudoun and two are in northwestern Loudoun.

The properties are considered to be important wildlife habitats, and in some cases they include plants uncommon in Virginia, according to members of the Open Space Advisory Committee.

Some county board members and others have questioned the plan at a time when the county is facing extreme budget problems. The total interest on the bonds could exceed $4 million during 20 years. At least one supervisor has suggested that the board develop a comprehensive policy on county government purchase and preservation of open space.

The county faces a potential revenue shortfall in the next fiscal year of as much as $30 million, though the supervisors and County Administrator Philip A. Bolen have begun to take steps to reduce that figure.

The concept of buying open space land, or purchasing guarantees that certain lands remain undisturbed, is supported by the draft of the county's General Plan, which is under review.

All 23 speakers at Tuesday's public hearing supported the March bond referendum, in which the voters would decide if open space lands could be preserved through use of county bond funds.

Scenic views and substantial unspoiled areas are "what make Loudoun great," Piedmont Environmental Council representative Howard Armfield said at the public hearing. The bond funding mechanism "is very necessary to meet the changing needs of Loudoun County," resident Charles Jones said.

On a vote of 6 to 0, with Supervisors James F. Brownell (R-Blue Ridge) and Steve W. Stockman (R-Broad Run) absent, the board indicated its intent to approve the referendum question at its next meeting on Tuesday, after the county attorney's review of wording changes.

Also this week, the supervisors and School Board members met with state Sen. Charles L. Waddell (D-Loudoun) and state Dels. Linda M. Rollins (R-Loudoun) and Robert T. Andrews (R-Fairfax/Loudoun) to discuss priorities for state legislation at this winter's General Assembly session. Money for the county school system and stronger local powers to make development pay its way are among the chief concerns of the Board of Supervisors.

Heading the Loudoun board's 1991 package of legislative requests is a provision that would guarantee that the county public schools receive at least as much state aid in the next two budget years as they are now getting.

Under a complicated formula designed to help relatively poor jurisdictions, some localities judged to be relatively wealthy, including Loudoun, have lost some of the state aid they had expected.

In addition, a state commission is studying a proposal that would accelerate that shift of funds to the neediest communities in an effort to boost their quality of instruction. State budget cuts imposed by Gov. L. Douglas Wilder will add to the intense struggle for education funding in the coming months.

The Board of Supervisors has made it clear to the county School Board that the supervisors won't be able to make up huge state aid cuts.

On Tuesday, Waddell reminded Loudoun officials that they face an uphill battle in getting significantly more money out of Richmond in 1991. "We don't have the votes" to make major changes in education funding formulas that will benefit Northern Virginia, he said.

Several land-use provisions are on the supervisors' "wish list." One would broaden the county's authority to impose transportation impact fees on developers to formalize their contributions to the local road system, to the extent that they are not provided under the voluntary proffer system.

In addition, Loudoun officials say they would like the authority to set up a system under which development rights in one area could be transferred to a nearby area in the county, plus a law that would require that public facilities be in place before some development can proceed.