Biomonitoring of Sulfur-Containing Pollutants in an Urban Atmosphere by FTIR Spectroscopy

Abstract

Introduction. Sulfur dioxide (SO2) formed by combustion of S-containing fuels (peat, coal, oil) and by various industrial processes is one of the principal acidic air pollutants. It is converted into an aerosol of sulfuric or sulfurous acid (H2SO4 or H2SO3) by absorbing atmospheric moisture [1–3]. Research on its identifi cation in air and the study of its reactions with biological systems are interesting because of its high toxicity [4–14]. FTIR spectral analysis (FSA) of epiphytic lichens [15, 16] is special among the various methods for studying air pollution in industrially developed regions because it can identify S-containing pollutants, estimate quantitatively their contents, and determine the levels and limits of the contamination. Studies demonstrating the capabilities of this biomonitoring method should be conducted in areas where the principal contamination sources are heat and power plants. The city of Tver is a convenient model for biomonitoring. Compared with other Russian cities, the air-pollution level is much less although the amount of pollutants released into the atmosphere has recently tended to increase [1, 17]. The goals of the present work were to evaluate biomonitoring results of air pollution by S-containing compounds in Tver including an evaluation of the ecological situation from the literature; to determine the monitoring sites based on an analysis of the industrial infrastructure; to evaluate the condition of the atmosphere based on FSA of the chemical composition of lichens; to divide the area in zones according to the pollution levels from the FSA results, to defi ne a network of sites for measuring the SO2 content in air based on the FSA data; to measure directly the SO2 content in air using an IR gas analyzer; and to develop maps showing the nature of SO2 air pollution. Materials and Methods. Biomonitoring sites such as recreation zones (RZ) differing in size, fl ora, and distance from the principal contamination sources located in various districts of the city (Proletarskii, Moskovskii, Tsentralnyi, and Zavolzhskii) were defi ned based on an analysis of the industrial and residential infrastructure of Tver [3] (Table 1). Samples of the lichen Hypogymnia physodes, which is moderately resistant to air pollution, were collected at the selected monitoring sites. This species is broadly distributed in the urban lichen fl ora and is characterized by the greatest chemical composition changes due to air pollution [3, 18]. Lichen samples 1–13 were collected at a height of 1.5 m primarily from the northeast side of one tree species that had no bark irregularities, mechanical damage, and obvious signs of disease. Material was also collected at an ecologically clean (outside the city) site (Feryazkino, Kalininskii District). The collected samples in KBr pellets were studied by FSA in the laboratory using the standard method [19]. For this, each lichen sample (3.0 mg) was dried at 25–30°C, ground in an agate mortar or a vibrational ball mill, and mixed with KBr powder (0.7 g). The mixture was pressed in a special form under vacuum at room temperature. Spectra were recorded on