Sulfur dioxide biochemical effects

These data and those of others (1, 5, 6, 26, 27) indicate a change in growth rate and/or a reduction in leaf area after prolonged exposure to sulfur dioxide. These effects indicate possible alterations in the normal physiological functioning of the plant, and therefore probably have both a visible (ultrastructure) and biochemical basis. 

Table 9-5 presents data from various animal studies on the acute toxicity of sulfur dioxide. These studies support findings from the human studies, indicating that sulfur dioxide exerts its effect primarily on the respiratory system. Acute effects at relatively low concentrations (<20ppm) induced transient bronchoconstriction and increases in airway resistance. Higher concentrations produced more sustained biochemical, clinical, and histologic changes in the respiratory system. No material effects were noted in organs outside of the respiratory tract after acute exposure to sulfur dioxide. 

Malhotra, S.S. and D. Hocking. 1976. Biochemical and cytological effects of sulfur dioxide on plant metabolism. New Phytol. 76 227-237. 

The chemical components of calcium carbonate — dissolved calcium ions and carbon dioxide — are widely distributed. Calcium is the fifth most common element in the earth s crust (after oxygen, silicon, aluminium and iron). It was extracted from early igneous rocks by the combined effects of erosion by the weather and corrosion by acidic gases (oxides of sulfur, oxides of nitrogen and carbon dioxide dissolved in rain water). Carbon dioxide makes up about 0.03 % by volume of the earth s atmosphere and is dissolved in both fresh and sea water. Combination of dissolved calcium ions and carbon dioxide resulted in the sedimentary deposition of calcium carbonate, which was subsequently converted into limestone rock. Early limestones (Precambrian — Table 2.1) are believed to have been deposited as precipitates of CaCOa, and/or as a result of the biochemical activity of very simple organisms, such as bacteria. 

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