ABSTRACT
The deterioration of monument or building stone materials is mostly due to the growth of black crusts that cause blackening and disaggregation of the exposed surface. This study reports on new oxygen (δ17O, δ18O and Δ17O) and sulphur (δ33S, δ34S, δ36S, Δ33S and Δ36S) isotopic analyses of black crust sulphates formed on building stones in Sicily (Southern Italy). The measurements are used to identify the possible influence of volcanic emissions on black crust formation. Black crusts were mostly sampled on carbonate stone substrate in different locations subject to various sulphur emission sources (marine, anthropogenic and volcanic). Unlike atmospheric sulphate aerosols that mostly exhibit Δ33S > 0, here most of the analysed black crust sulphates show negative Δ33S. This confirms that black crust sulphates do not result from deposition of sulphate aerosols or of rainwater but mostly from the oxidation of dry deposited SO2 onto the stone substrate. The δ34S and δ18O values indicate that most of black crust sulphate originates from anthropogenic activities. Δ17O values are found to be related to the sampling location. The largest 17O-anomalies (up to ~4) are measured in black crust from areas highly influenced by volcanic emissions, which demonstrates the strong involvement of ozone in the formation of black crusts in volcanically influenced environments.
ABSTRACT
RECENT observations suggest that the eruption of Mount Pinatubo in June 1991 has had a considerable effect on ozone concentrations in the tropical stratosphere (refs 1, 2, and J. W. Waters, personal communication). Although stratospheric ozone losses following volcanic eruptions are generally attributed to the presence of sulphate aerosol3-7, we present model calculations which demonstrate that gas-phase sulphur chemistry may have played a part in the tropical ozone perturbations that followed the Pinatubo eruption. We find that in the first month or so after the eruption, the large amount of SO2 injected into the tropical atmosphere catalyses mid-stratospheric ozone production. On the other hand, the SO2 cloud absorbs solar radiation, thereby reducing the rate of O2 photolysis (and hence of ozone production) below it. These two effects cancel each other out at an altitude of about 25 kilometres. After one or two months, most of the SO2 has been oxidized to sulphate; the efficiency of these two mechanisms then becomes negligible (although ozone remains perturbed in the lower stratosphere because of its long photochemical lifetime in this region). The model features show good agreement with initial ozone measurements following the eruption, including both the mid-altitude switch from ozone loss to ozone gain1, and the increase and subsequent decrease in the total ozone column2,7.
ABSTRACT
Using clinical, radiological and histologic examinations, 41 cases with the rapidly destructive coxarthrosis (RDC) were studied. (a) The radiological findings of RDC were classified into the following three types; type I suddenly started from the normal hip joint and terminated in the upper outer subluxation with destruction of the head and acetabulum resulting in narrowing of the joint space; type II was clinically very similar to type I. The joint was destructed but remained in the primary acetabulum; type III developed into sudden destruction of the joint during ordinary course of secondary RDC. (b) The histological findings of RDC were classified into those involving avascular necrosis and those involving osteoarthritis. (c) 65% of cases of radiological Type I showed avascular necrosis, 33% in Type II, and 12.5% in Type III. (d) The clinical examinations revealed that most cases have some immunological abnormality. The present study, therefore, indicates that the most common pathogenesis of RDC has a basic condition of avascular necrosis in the femoral head in the elderly, in addition, the accompanying rapid destruction appears to be related to an immunological abnormality.
