We have investigated the effectiveness of deacidification for paper exposed to ambient levels of two major air pollutants, SO2 and NO2. Sulfur dioxide and nitrogen dioxide concentrations were monitored at the exposure chamber inlet and exit with pulsed fluorescence and chemiluminescence techniques, respectively. Paper samples showed a larger capacity for uptake of SO2 than for NO2. Periodically, paper samples were withdrawn from the chambers and analyzed for pH, nitrate, nitrite, sulfate, sulfite, and bisulfite. The results are discussed in terms of pollutant uptake and retention for both deacidified and untreated paper.
Paper degradation is mostly due to the acidic hydrolysis of the glycosidic linkages in cellulose.
In an effort to preserve works of art and historical records, paper deacidification has become a widely practiced protection measure in the conservation community. Paper deacidification neutralizes the acidic content of paper and leaves an alkaline reserve for the uptake of acidic pollutants. The degradation of paper due to uptake of airborne SO2 has been the object of many studies. A potential problem with using such high SO2 concentrations, at which SO2 would readily form sulfuric acid aerosol in air at ambient humidity, is that the observed damage may be due to uptake of sulfuric acid, H2SO4, rather than SO2. In addition, no one has directly measured the expected products of SO2 absorption on paper, i.e., sulfite, bisulfite, and sulfate.