A standardized method for determining buffering capacity of plant foliage

Summary A method for determining the buffering capacity (B.C.) of foliage extracts was standardized and evaluated. Sources of variations (biological, field and laboratory) were identified. These variations were reflected in inter-specific differences, seasonal fluctuations, age of the foliage and duration and the conditions of storage of the extracts. Procedures have been recommended to eliminate or minimize sources of variations (other than inherent specific) by standardizing the field sampling, laboratory processing and methods, and calculations of the buffering capacity. Plants such as lichens, known to be sensitive to air pollutants, had very low B.C. whereas species of intermediate sensitivity such as balsam fir had higher B.C. The B.C. being inherited and significantly different among species, has potential for its use in indexing the relative sensitivity of species to air pollutants especially in areas where large numbers of species are to be compared.