the origin of oil hydrocarbons in southern coastal sediments of the caspian sea in vicinity of gholestan and mazandran province

the caspian sea as the biggest surrounded water body (lake) in the world is bordered by the states of azerbaijan, russia, iran, kazakhstan and turkmenistan. urban development in addition to the increase of industrial and oil production activities (oil refinery and petrochemical plants) in the northern and eastern regions of caspian sea in recent years have caused entrance of high amount of oily pollutants in to this sensitive area. former studies in this area, report important pollution of the sediment to petroleum hydrocarbons in central and south eastern coast of the sea in vicinity of azerbaijan and iran shore. considering different origins of hydrocarbons (biogenic and petrogenic) in the marine sediment, distinguishing the origin and the source of the observed hydrocarbons has been received more attentions by the environmental scientists. in the current paper through surface sediment sampling in the large area of golestan and mazandaran provinces shores, concentrations of resolved and unresolved parts of aliphatic and aromatic hydrocarbons are identified and also compared with former reported concentrations. moreover in order to differentiate the origins of the hydrocarbons, based on the observed aliphatic parameters, needed indices have been developed. the developed indices show the biogenic and nonpetroleum origin of the hydrocarbon in the surface sediment of the study area, whereas the petrogenic origin of the hydrocarbons in the south eastern coast of the caspian sea, near the west area of gilan province, has been previously reported. the biogenic origin of hydrocarbons in the coastal areas of mazandaran and golestan provinces then apparently remarks non-pollution of the area by the oil production activities of the azerbaijan in the far west part of the study area.