Physico-Chemical Properties of Soil and Quantitative Analysis of a Herbaceous Community after Blowout of an Oil Well

The effects of pollution by crude petroleum on the soil physico-chemical properties like colour, moisture content, porosity, water holding capacity, pH, total nitrogen, organic carbon, phosphorus, potassium, C/N and C/P ratios, crude oil content and the periodical effects on some ecological parameters have been investigated after eight years of accidental blowout of an oil well in upper Assam, India. Crude oil pollution has a significant impact on soil environment. The total number of species decreases with increasing oil level in the different sites. Annuals are more affected than the perennials; the effect being more severe in the dry period. The highest similarity index (SI) (0.724) was found between site B (moderately polluted site) and C (less polluted site). Species diversity index (SDI) decreases with the increasing oil level while index of dominance (CD) showed an increasing trend with the increasing pollution level. Eleocharis palustris, a perennial monocot, is the highest percentage contributor of total community IVI. The dual mode of propagation and well-developed underground system of the perennials help it to be oil tolerant or oil resistant.