Ecology, Environment and Conservation Paper

ACCUMULATIONS OF HEAVY METALS IN SOME SELECTED PLANT PARTS (RICE GRAINS, RICE HUSKS, PAPAYA FRUITS AND TEA LEAVES) COLLECTED FROM CRUDE OIL CONTAMINATED SITES IN ASSAMA

Mukut Kalita, K G Bhattacharyya and Arundhuti Devi

Abstract

In an oil field oil from the wells is pumped to Group Gathering Stations (GGS) where the oil undergoes some treatment and is stored for transporting to refineries. A large number of contaminants including heavy metals enter into the nearby agricultural fields of a GGS through spills, leaks as well as through emissions from gas flaring and from effluents which are likely to pollute the environment. Plants can take up heavy metals from air and water as well as from soil and sediment. Excess concentrations of heavy metals in plants are toxic to both plants and animals. We investigated heavy metal accumulation in plants at crude oil contaminated sites near the five well-known GGSs, i.e., Rudrasagar GGS1, Rudrasagar GGS2, Lakowa GGS1, Lakowa GGS3 and Lakowa GGS9 operated by the Oil and Natural Gas Corporation Limited in Assam. Rice grains, papaya fruits and tea leaves in crude oil contaminated areas and uncontaminated areas were sampled. The concentrations of seven heavy metals (Cd, Cu, Zn, Fe, Mn, Ni and V) in rice grains, rice husks, papaya fruits, and tea leaves for different locations were determined. Soil samples were also taken (at 0-45 cm depth) for the measurement of total petroleum hydrocarbon content. Variation in heavy metal accumulation in a plant part depending upon the growth sites was studied. Results indicated that the concentrations of heavy metals in the plants increased with the increase in crude oil contamination of the growth sites. Substantial differences in the abilities of various plant species to accumulate the heavy metals were also observed. In the plant samples, the element wise variations in metal concentrations were found to be very complicated. Our results indicate that the consumption of rice grown in contaminated soils may pose a serious risk to human health.