Jacobs Journal of Organic Chemistry

Investigation of N-Alkanes and Polyaromatic Hydrocarbons in Estuarine Sediments of Patos Lagoon (Brazil) - Anthropogenic Impacts

*Larissa P Costa
Department Of Chemistry, Oceanography Institute, Rio Grande, Italy

*Corresponding Author:
Larissa P Costa
Department Of Chemistry, Oceanography Institute, Rio Grande, Italy
Email:larissap.costa@hotmail.com

Published on: 2018-10-10

Abstract

This paper presents a study of the historical record from organic contamination in two areas (Mangueira Bay (SM) and Arraial Bay (SA)) under the impact of various anthropogenic sources (e.g. pyrolytic and petrogenic) in Patos Lagoon Estuary. Aliphatic hydrocarbons (AH) and polyaromatic hydrocarbons (PAH) were determined by gas chromatography with flame ionization detection (GC/FID) and gas chromatography with mass detection (GC/MS), respectively. Geochemical indexes, pre-established in the literature, were used to diagnose the human impact. Overall, in Mangueira Bay, individual distribution and AH indexes suggested a preferential contribution of petrogenic source of hydrocarbons for the last 60 years, AH little or no prevailing in the odd/even ratio also pointed to an introduction of oil. However, it was also found high concentrations of PAH with 4-6 rings, suggesting the input of pyrolytic sources. The concentration levels reached values of 284.63μg.g-1 and 780.05ng.g-1, for AH and PAH respectively, telling high contamination. In the drill core from Arraial Bay, total aliphatic concentrations were below 69.98μg.g-1 , reaching values less than 10μg.g-1 , suggesting a place free of anthropogenic contamination and with large biogenic contribution. PAH concentrations for Arraial Bay were also low, reaching values of 55.09ng.g-1 or less, with greater contribution of pyrolytics sources. We conclude that in the estuarine region of Patos Lagoon coexist urban, port and industrial activities. Therefore, it was observed the presence of anthropogenic contributions, directly associated with the proximity of potential sources (urban pollution, petrogenic and pyrolytic), considered to have higher concentrations in Mangueira Bay region.

Keywords

Anthropogenic source; geochemical indexes; Hydrocarbons; Historical record

Introduction

The continuous increase in urbanization in estuarine environments has led to the increase and accumulation of organic compounds at levels harmful to the biota and environmental quality [1]. The anthropogenic contributions most commonly found in the aquatic environment refer to dredged material dumps, urban and industrial effluents, leaching of rural areas and atmospheric inputs.[1 2] In a global perspective, the classes of contaminants considered critical to health of aquatic environment are petroleum hydrocarbons, halogenated hydrocarbons, heavy metals and solid waste.[3] Hydrocarbons are a class of compounds that have good chemical stability in water and sediments, so they have been widely used as biomarkers and as indicators of oil pollution. The use of molecules or groups of molecules that can be unmistakably related to specific origins introduces the concept of molecular markers.[4-6] Sedimentary aliphatic hydrocarbons (AHs) have both natural (including biogenic and petrogenic) and anthropogenic sources[7] AH natural inputs are comprised mostly of vascular plants, algae, microorganisms and early diagenesis of natural products[8] and present an AH distribution with predominance of odd carbons.[9] Anthropogenic AHs in sediment originate mainly from petroleum residues and generally exhibit an unresolved complex mixture (UCM) of branched and cyclic hydrocarbons.[10]