SENSITIVITY OF MONUMENT CORROSION FOR THE DETERMINATION OF THE SPATIAL AND TEMPORAL DISTRIBUTION OF ACID RAIN, BIRMINGHAM, ENGLAND

Birmingham, England, has been an industrial center for two centuries, and the burning of high-sulfur coal has led to severe air pollution and acid rain problems. In industrial areas such as this, monument corrosion has been used effectively as a quantitative measure of acid rain and therefore acid deposition rates. However, careful analysis of marble tombstones that use the flush lead lettering technique have allowed us to construct a database that establishes natural background corrosion rates, effects of residential expansion, the efficacy of pollution control measures, and to some degree discriminates between industrial and residential sources of pollution.

Flush lead lettering is accomplished by carving letters in the stone and hammering lead into the recesses. The lead is then trimmed flush with the stone surface using a sharp, broad-head chisel. Corrosion of the marble leaves the lead raised above the surface, and the distance can be measured with the use of a micrometer. The loss of calcite on stones of various ages can then be used to determine the time-dependent acid deposition rate. Our corrosion database consists of 386 individual measurements on 121 tombstones in 19 cemeteries. Each measurement is an average of 10 readings with the high and low discarded. Corrosion rates vary from a minimum of 0.1 mm/century in the rural southwestern part of the study area to 3.0 mm/century in industrial areas. In the Birmingham city center, corrosion rates are essentially constant from 1860 until 1965 when implementation of pollution control measures dramatically reduced acid rain. In residential areas, however, little corrosion occurred until after World War I when population grew rapidly. Total acid deposition can be calculated. Assuming that the corrosion is due solely to sulfuric acid (from high sulfur coal), sulfur deposition rates vary from a minimum of 2.1 to a maximum of 56 tons/mi2/year.