In the mid 1980s, the National Acid Precipitation Assessment Program (NAPAP), in cooperation with the National Park Service (NPS) and the U.S. Geological Survey (USGS), initiated a Materials Research Program (MRP) that included a series of field and laboratory studies with the broad objective of providing scientific information on acid rain effects on calcareous building stone. Among the several effects investigated, the chemical dissolution of limestone and marble by rainfall was given particular attention because of the pervasive appearance of erosion effects on cultural materials situated outdoors. Runoff solution volume statistics Volume, averages (figure 1(avg)). The runoff volume is the key variable linking the observed concentrations to mass loss. Figure 1(avg) shows a comparison of the blank-runoff volume averaged over all observed events for each MRP site. Detailed statistics, including the range, mean values, standard deviation, and number of samples for the runoff-solution volumes for the blank, limestone, and marble slabs are provided in tables 5, 6, and 7 in the appendix to this report. Volume, histograms and chi-square test (figures 1 to 15). With the exception of figures 7 to 9 (NJ site), a general characteristic of the volume histograms is that their distributions somewhat conform to a gamma distribution. The statistical deviation of the runoff-volume data collected for the limestone, marble and blank slabs at the NJ site from the distributions of runoff-volume data from the DC, NY, NC, and OH sites is evidence of the corruption of the NJ data set by a significant number of entries. 8 In addition, there is a consistent statistical disparity among the limestone, marble, and blank distributions at all of the field sites. In general, the gamma distributions for the limestone volume data are more exponential-like 9 than are the distributions for marble-volume or blank-volume data. Note that the ranges and the mean values for the limestone volume measurements are significantly less than the ranges and means for the marble or blank volume measurements. These findings are consistent with the imbibition of about 1.5 L of rain by the limestone slabs. Volume (figures 16 to 20):(a) limestone vs. marble; (b) limestone, marble, and blank (sorted on blank); and (c) marble (sorted on marble volume). The plots in figures 16 to 20 reveal the degree of correlation and the extent of statistical consistency among the runoff volumes from the
