FLUORIDE TOXICITY IN RICE FIELDS IN THE PERIPHERY OF AN ALUMINIUM SMELTER IN ODISHA, INDIA.

The prevalence of hydrogen fluoride (HF) toxicity in rice plants with visible foliar injury was observed in rice fields in the vicinity of an aluminium smelter in Odisha, India. The crop was damaged up to 2.5 km from the aluminium smelter by the atmospheric transportation of fluoride (F) under the influence of the prevailing wind and rain. Plants growing nearer to the smelter (1 km) were exposed more to the fluoride toxicity, resulting in reduced vegetative growth with a reduction in the total dry matter production and a light green colour due to a lower chlorophyll content. The grain yield of the plants with chronic fluoride toxicity was reduced by 53.7%. The grain yield increased as the distance from the smelter increased indicating that the industrial F pollution persisted in the study area. The F content in the leaves of the rice plants at a distance up to 2.5 km from the smelter was higher (95.8±28.6 ppm) than the threshold limit of 30 ppm. The F content in the upper layer of the soil within 3 km from the smelter varied from 83.3±0.7 to 203.1±5.9 ppm. The F content in water at 1 to 2 km from the smelter was higher (1.7±0.6 to 3.7±0.9 ppm) than the threshold limit of 1.5 ppm, whereas from 2.5 to 3 km from the smelter, it was within the 1.5 ppm standard (0.6±0.3 to 0.8±0.4 ppm). The range of the F concentration in the rice grains was 0.3±0.1 to 1.4±0.9 ppm with those collected from 2 or more km from the smelter having a F content that was lower than the threshold limit of 1.0 ppm. The F-containing emissions of the aluminium smelter were considered to be the likely cause of the F accumulation and the pollution of the soil, plants, and water in the vicinity of the aluminium smelter. [ABSTRACT FROM AUTHOR]