Evaporation measurement for the preservation of the Buddhist Monastery of Ajina Tepa, Tajikistan

One of the decay mechanisms of historical earthen walls of Ajina Tepa (Tajikistan) is represented by salt crystallization. Halite, calcite and gypsum are found in abundance on the historical walls. Because the rate of crystallization is thought to be a function of evaporation, this was measured by using a newly developed a portable evaporation meter. Before the measurement, the accuracy of the evaporation meter was carefully studied under both no-wind and wind conditions in laboratory and field tests in Japan. The effect of average wind velocity on the evaporation measurement was also evaluated before the measurement. It was found that the evaporation rate is high at the foot of the wall and it decreases on top. This feature implies that moisture is mainly supplied from ground and that a protective shelter coat is needed to prevent the destruction of historical wall due to salt crystallization.