酸雨及鹽分危害之風化材保存特性

Conservation Characteristics of Weathered Wood Degraded by Acid Rain and Salt

本試驗乃模擬受酸雨（pH3.6 的硫酸與硝酸混合液（H2SO4：HNO3＝3：1））及鹽分（5 %氯化鈉溶液）危害後杉木之性質變化，以供木質文物保存之參考。酸雨使杉木表面顏色快速改變，吸濕性與吸水率均增高，主要與木材表面劣化及鹽分沉積有關。從傅立葉轉換紅外線光譜（FTIR）吸收峰相對強度比值中發現，受酸雨影響的試體木質素含量會大量減少，而產生多量的羧基（carboxyl groups）和羰基（carbonyl groups）；多醣類被破壞形成多量C-O 和C-OH 官能基。受鹽分危害的試體，O/C 和O/H 比值較高，顯示劣化極為嚴重。鹽分會阻礙膠合，造成膠合強度顯著下降。 Test wood (Cunninghamia lanceolata Hook, China-fir) was treated with simulated acid rain (3.6 pH of mixtures with sulfuric acid and nitric acid (SO42-：NO3-＝3：1)) and salt (5 % NaCl solutions) to investigate their effects on the properties of these weathered wood to give reference for the conservation of wood-based cultural relics. After natural weathering for one year, the color of specimen surface was significantly changed to gray which accounts for severe deterioration from acid. The increase in the hygroscopicity and water absorption of acid rain and salt treated wood was found out as well. This phenomenon may be resulted from the adverse effect of acid rain and salt treatments. By the results of FTIR analysis, the present of CO- and COOH groups indicating the abundant lignin components were liberated upon the acid rain and salt treatments. The degradation of polysaccharides to C-O and C-OH groups demonstrated that acid rain and salt gave apparent influence on the specimens. By the elemental analysis, the higher O/C and O/H ratios in weathered wood showed that the salt has severe effect on specimen. The bonding ability i.e., the decreased bonding strength was significantly retarded for the salt treated wood tested with PVAc adhesive. In addition, the apparent craking on wood surface and the falling in bonding was also appeared for acid rain treated wood tested with Epoxy adhesive.

Test wood (Cunninghamia lanceolata Hook, China-fir) was treated with simulated acid rain (3.6 pH of mixtures with sulfuric acid and nitric acid (SO42-：NO3-＝3：1)) and salt (5 % NaCl solutions) to investigate their effects on the properties of these weathered wood to give reference for the conservation of wood-based cultural relics. After natural weathering for one year, the color of specimen surface was significantly changed to gray which accounts for severe deterioration from acid. The increase in the hygroscopicity and water absorption of acid rain and salt treated wood was found out as well. This phenomenon may be resulted from the adverse effect of acid rain and salt treatments. By the results of FTIR analysis, the present of CO- and COOH groups indicating the abundant lignin components were liberated upon the acid rain and salt treatments. The degradation of polysaccharides to C-O and C-OH groups demonstrated that acid rain and salt gave apparent influence on the specimens. By the elemental analysis, the higher O/C and O/H ratios in weathered wood showed that the salt has severe effect on specimen. The bonding ability i.e., the decreased bonding strength was significantly retarded for the salt treated wood tested with PVAc adhesive. In addition, the apparent craking on wood surface and the falling in bonding was also appeared for acid rain treated wood tested with Epoxy adhesive.