Pollutant Distribution: A Review of Hydrocarbons in Marine Sediments

Abstract

Over the last century, human activity has resulted in an increasing rate of release of hydrocarbons that, in one way or another, have become parts of marine sediments. This trend is especially evident in sediments that have been deposited in the vicinity of industrialized urban centres.In this paper, hydrocarbon distribution-patterns of coastal marine sediments near to two urban centres (Providence, Rhode Island, and Los Angeles, California) are examined in detail. At each location the spatial distribution of sedimentary hydrocarbons shows the greatest concentrations in areas of natural sediment-deposition near to the urban center. Examination of sediment cores from these areas shows that fossil hydrocarbons have increased from a minor fraction of total sedimentary hydrocarbons a century ago to being the major contributors today. Results from other industrialized areas of North America and Europe indicate that these patterns are typical.Sediments that are remote from population centres have markedly lower concentrations of hydrocarbons than those deposited near to such centres, as might indeed be expected. Yet indications of anthropogenic contributions of hydrocarbons are detectable even in remote polar locations. In addition to hydrocarbons coming directly from fossil fuels, aromatic hydrocarbons that had been formed during incomplete combustion of other carbonaceous material, also accumulate in marine sediments. Fortunately, hydrocarbons from these two sources (fossil-fuel and other combustion) can be distinguished chemically.