Toxic hazards of the industrial atmospheric pollutant, SO2,on tree crops

Abstract

A study was conducted to assess the effects of the industrial atmospheric pollutant, sulphur dioxide, on tree crops. The Veli area in Thiruvananthapuram district, Kerala which has been established as a polluted zone, due to the working of the Travancore Titanium products, was selected as the experimental site. Since coconut dominates the tree crops in the area, and due to its added importance as an oilseed, the study was conducted on coconut palms near the factory. Influence of sulphur dioxide pollution on plant parameters like sulphur content of foliage, pigment concentration, macro and micro nutrients, plant metabolites like glucose and ascorbic acid, catalase activity and the copra and oil contents of nuts were studied. Leaf and nut samples were taken at distances of 250, 500, 1000, 1500, 2000 and 5000 m, with the samples at 5000m taken as control. Visual observations, detailed chemical analysis of leaf samples and study of nut characters were conducted on the sampled palms. Visual observations revealed a high degree of chlorosis and necrosis of palms near the factory. As distance from the pollution source increased, the intensity of damage decreased, with the control palms at 5000 m showing no signs of visible injury. Data from Chemical analyses showed significantly higher concentration of total sulphur and sulphate sulphur in palms near the Titanium factory (1.731 and 0.364 per cent respectively). A drastic reduction was noticed in the plant nutrients like nitrogen, phosphorus, potassium and calcium in palms exposed to higher sulphur dioxide concentrations. Magnesium content was not affected significantly though in palms near the factory, there was a decrease in concentration. Among the micronutrients analysed, iron, copper and boron were affected, with the contents of iron and copper increasing with increased sulphur dioxide pollution and boron showing a decrease. Sulphur dioxide had no effect on the zinc, molybdenum and manganese contents while sodium and chlorine contents was reduced. The contents of aluminium was increased significantly in palms near the pollution source. Plant metabolites like ascorbic acid and glucose were decreased but the activity of catalase enzyme in leaf remained unaffected. The plant pigments like chlorophyll and carotenoids were also reduced in quantity, which may either be due to their degradation or decreased production. Among the nut characters studied, the contents of copra and oil were drastically reduced. The adverse effects of increased sulphur dioxide content in the atmosphere was high upto 1 km from the source and gradually decreased with the effect not felt at 5 km. These findings reveal that concentrations of sulphur dioxide higher than normal in the atmosphere can lead to plant injury in the surrounding area, in addition to the effects on human beings. The establishment of new industries and thermal power stations pose a new treat to the cultivated and native plants in that area. Since industrialization is the forerunner of development, the contribution of industries to toxic gases should be reduced by the adoption of suitable pollution control measures, if plant life in nature should proceed unhindered.