Abstract
An investigation was conducted in Ilha Grande and Sepetiba Bays aiming at identifying the nature of non-aromatic hydrocarbons (NAH) in surface sediments. NAH concentrations ranged from 2.5 µg g-1 to 193.8 µg g-1 of which the major fraction (53 to 93%) was composed by unresolved complex mixture (UMC). In most samples n-alkane distribution was dominated by compounds of odd carbon number showing maxima in nC29 and nC31. Mono-olefins were at low concentrations and the polyolefins including highly branched isoprenoids and squalene varied from 0.099 µg g-1 to 1.387 µg g-1 with lower values relative to NAH appearing in areas of strong terrestrial and anthropogenic influence. Hopanes between C27 and C33 were observed in all samples with the predominant configuration 17a(H),21b(H), characteristic of a petrogenic origin.
Highlights
Estuarine systems are zones of transport, recycling and deposition of organic matter derived from autochthonous biological productivity, from land drainage and anthropogenic inputs
The present paper reports data on non-aromatic hydrocarbons in surface marine sediments collected in Ilha Grande and Sepetiba Bays
The greater organic carbon values were found: (i) at stations 1 and 2 which are nearer to the coast line in the western part of the Ilha Grande Bay, an area of low hydrodynamics that receives inputs from mangroves and from the Parati River; (ii) at station 14 located at the mouth of the sewage contaminated Guandu river; and (iii) at station 9, where the bottom topography and presence of a depression may favor particle settling
Summary
Estuarine systems are zones of transport, recycling and deposition of organic matter derived from autochthonous biological productivity, from land drainage and anthropogenic inputs. Hydrocarbons are component of organic matter derived as much from natural sources as from petroleum and by-products. Most plants and animals synthesize non-aromatic hydrocarbon (NAH) comprising homologous series of n-alkanes and n-alkenes, cyclic alkenes, saturated and unsaturated isoprenoid compounds and triterpenes.[4,5,6,7,8,9,10]. Anthropogenic sources related to production, transfer, storage and refining of petroleum release NAH which are predominantly linear, branched and cyclic alkanes.[11] Hydrocarbons derived from burning petroleum by-products are predominantly of a different nature.[12]
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