Among the natural resources that are in the womb of Mother Nature crude oil is the most important mineral that is being used by all the nations of the world. It is not a single chemical but a collection of hundred of widely different variety of chemicals. It is such a mineral that the modern human civilization of the earth cannot dream off a single moment in its absence. Crude oil is a conglomeration of a variety of minerals and when mixed with soil it changes the physico-chemical parameters of the soil and water. Secondly, when it penetrates into the soil it directly affects plant root system, vegetation, microbial population and oxygen content .
For the use of mankind oil is extracted through scientific means. While this is extracted and refined, various chemical substances get mixed up with soil and water and hence the contamination of soil and water occurs. This results in environmental degradation of micronutrients of soil and release of toxic elements in the air also affect the productivity of the soil. Water is the liquid for life and safe drinking water is a must for all around development of human health. To satisfy man ̓s needs crude oil is extracted and in the production and extraction processes water in the adjoining areas gets contaminated and affects human health as well as animal health also.
Assam is blessed by nature in respect of oil and natural gas. North East region is one of the major onshore oil producing regions of India. The oil and natural gas corporation was formed in 1959 under an act of parliament to take over the activities of oil and natural gas. In oil and natural gas industry drilling is the only direct method of ascertaining the presence of hydrocarbons at a particular place. During the exploration and exploitation of Petroleum resources of an area, the surrounding area has contaminated. The major waste products during drilling operations are brine, oil-bearing water, the drilling mud, drilling cuttings and various chemicals that are used during drilling and production operations. Drilling operations by ONGC is a major threat to the biodiversity of the area .
The heavy metals may be found in considerable amount in soil and water in and around of the Oil drilling sites. This is because of the wide use of chemicals containing heavy metals being discharged into the environment in petroleum exploration and production activities.
For Lead (Pb) the toxicity characteristic Leachate limits (TCL) is 5.00 mg/kg (Bowen, 1979). Lead is toxic to many plant species, although a few are relatively tolerant when ingested. Lead can cause a disease called Plumbism. Lead can also damage the brain, the central nervous system, kidney, liver and the reproductive system .
The normal concentration level of Copper ranges from 5.00-20.00 mg/kg required by plants in natural soil concentration (Bowen, 1979). Copper is generally higher in soil derived from rocks and tends to be lower in extreme acid and alkaline soil. Copper in excess amount can be harmful. Pollution occurs in areas where copper is found and worked .
The Iron (Fe) toxicity rarely creates problems in this field. Although it can find its way to the groundwater thereby polluting it. The high Iron concentration could be because of the below mentioned reasons–
- D76 which contains Iron is one of the chemicals used for drilling operation.
- Iron contained in the laterite soil, used in sand filling the waste pits after completion of the drilling operation .
The amount of Zinc (Zn) in normal level ranges from 1.00 – 900 mg/kg in soil (Bowen, 1979). Zinc is an essential element in our diet. Lesser or heavy amount of zinc consumed can cause bad effects to our health. Harmful effects generally begin at levels 10-15 times higher than the amount needed for good health. Large doses taken orally even for a short time can cause stomach cramps, nausea, and vomiting. Used longer it can cause anemia and decrease the level of good cholesterol. Zinc can be a pollutant especially in areas close to industrial plants engaged in processing of petroleum because zinc is directly added to the drilling fluids as zinc carbonate and act as corrosion inhibitor for mud formation and part of the zinc can be trapped by the soil layer .
The chromium (Cr) toxicity characteristics Leachate limits (TCL) of 5.00 mg/kg. Chromium (VI) is toxic. Acute toxic effects may occur when breathing very high levels of Chromium (VI) in air, which can damage and irritate the nose, lungs, stomach and intestine. People who are allergic to chromium may also have asthma attacks after breathing high levels of either Chromium (VI) or (III). Long-term exposures to high or moderate levels of Chromium (VI) cause damage to the nose thereby resulting in bleeding, itching, and sores .
Crude oil is certainly responsible for the alternations of soil and water physico-chemical properties, destroy the seed bank, habitats of micro flora and fauna, vegetation, energy flow results in lowering the complexity of terrestrial ecosystem and produce a physically controlled ecosystem rather than a biologically controlled ecosystem by reduction in species diversity so it is utmost necessary to take some perfect steps either to control or to minimize the crude oil pollution in the region where hectic oil exploration activities has recently been geared up in various oil fields .
-  Barua D., Buragohain J., Sarma S.K., Certain physico-chemical changes in the soil brought about by contamination of crude oil in two oil fields of Assam, NE India, European Journal Of Experimental Biology, 2011, 1(3):154-161, ISSN: 2248-9215.
-  Asia I.O., Jerade S.I., Jerade D.A., Bemad A.E., The effects of petroleum exploration and production operations on the heavy metals contents of soil and ground water in the Niger Delta, International Journal of physical Sciences, Vol 2(10), pp 271-275, october 2007, ISBN-1684-5315.