Any moneys not otherwise subvened or allocated by the state board pursuant to this chapter may be used for supplemental subventions, upon application, up to a one-to-one matching basis or, in the state board’s discretion, for any other purpose related to the control of nonvehicular sources. Matching supplemental subventions having unusual merit shall be given preference over expenditures for other purposes. In making supplemental subventions, the state board may consider federal grants received by the applicant and by other districts.