Temperature and relative humidity in a palaeontological collection: the buffering effect of microenvironments

Abstract Adequate values of environmental parameters are crucial for the long-term preservation of the fossils in a palaeontological collection. In particular, incorrect or fluctuating temperature (T) and relative humidity (RH) can affect glued or repaired materials, induce the proliferation of mould, provoke mechanical breakage, recrystallization or mineral decay. From April 2015 to March 2017, six hygrothermometers were incorporated in selected microenvironments of the Palaeontological Collection at the Facultad de Ciencias, Universidad de la Republica at Montevideo, Uruguay. The main aim of this study was to test the buffering effect of different enclosures compared to the ambient environmental parameters (AMB). The selected storage units were a mobile rack of shelves (C1), a cardboard box inside C1 (C2), a lidded plastic polypropylene box inside C1 (C3), a drawer in a non sealed cabinet (P), and a drawer inside a tightly sealing cabinet (G1). Maximum and minimum values of T and RH were manually gathered on a weekly basis. Linear graphs and statistical analysis (i.e. mean values, standard deviation and Kruskall-Wallis non-parametric variance analysis) were used to compare the measurements obtained. Regarding both T and RH, the more extreme values and fluctuation of these parameters were achieved in the ambient. With respect to T, all enclosures protected from Tmax variations as lower Tmax were recorded inside enclosures. With respect to RH, only C3 and G1 showed significantly lower values of RHmax than ambient values. Additionally, C3 and G1 showed an almost constant amplitude between maximum and minimum values which indicates that specimens were less exposed to fluctuations in RH. The results herein obtained show that to minimize the impact of environmental instability, it is safer for specimens to substitute cardboard by plastic containers, and closed storage units are better than open ones. In addition, sealed containers and cabinets protect the specimens from other agents of deterioration such as dust and pests.