Distribuição espaço-temporal de hidrocarbonetos de petróleo no estuário do Rio Vaza Barris-SE

The Vaza Barris river estuarine system is located at 11o 08 ´S and 37o 10´ W, at sea level. It has a total area of 115 km2, with a ecosystem with great biological diversity and vegetation composition. Due its great importance in biological and vegetative diversity, it has been inserted in an Environmental Protection area, called EPA. The Vaza Barris river estuarine system has been suffering with human actions, such as recreation and leisure, traffic of maritime vessels, shrimp farming and real estate activities. The present work aims to understand the spatial and temporal distribution of geochemical biomarkers, the Aliphatic Hydrocarbons (AH) and Polycyclic Aromatic Hydrocarbons (PAH) on the superficial sediments of the Vaza Barris river. This work also intends to understand how sedimentary deposition has happened and the importance of this deposition. To conduct this study, samples were collected in two campaigns (Winter and Summer). During the winter, 13 sites were sampled with a triplicate in the station 13 (13a, 13b and 13c). In the summer campaign, it was repeated the 13 sites previous sampled and added two others, giving a total of 15 sites. For the extraction of hydrocarbons from the sediments, it was used Ultrasonic extraction, with dichloromethane as the extraction solvent. In the samples clean-up (alumina and silica), hexane was used for the AH (F1) Fraction elution and dichloromethane/n-hexane (1:1) for the elution of PAH fraction (F2). The analysis was carried out by Gas Chromatography/Mass Spectrometry (GC/MS). To understand the distribution of hydrocarbons, it as used several Diagnostic Index Ratios (DIR). The AH and its isoprenoid (Pristane and Phytane) had good recoveries, wit values between 50.74 and 108.95% and a mean recovery above 60% with relative standard deviation RSD of 18.8%. Their concentrations ranged from 0.19 up to 8.5 Êg.g-1 of dry sediment. The Carbon Preference Index (CPI) calculated for all points (except for VB2 and VB3 in winter) associated with reasons °alifaticos/n-C16 and BMM/AMM (ratio of Low Molecular Weight/High Molecular Weight) suggested biogenic contribution. Their values of RTA (Terrestrial to Aquatic Ratio) and predominance of odd chains and high concentrations of the n-C29 homologue indicated biogenic contribution with significant contribution of higher terrestrial plants. The recoveries of PAH ranged between 45.46 and 163.0% with a mean recovery above 100% and RSD of 28.31%. Their total concentrations ranged from 0.09 a 410.4 ng.g-1 of dry sediment, with levels above the TEL (NOAA) and PQT (Environment Canada). Its DIR indicated a mixture of contributions (petrogenico, pyrolytic and combustion of biomass), with a strong tendency of pyrolytic contribution. Its distribution shows a predominance of high molecular weight compounds, registering significant concentrations for Benzo(a)pyrene, Pyrene, followed by Benzo(b)fluoranthene and Benzo(a)anthracene, both considered mutagenic and carcinogenic. The predominance of pyrolytic contribution may be justified by the existing heavy boat traffic in the estuary.O estuario do Rio Vaza Barris esta situado a 11o 08 f S e 37o 10 f O ao nivel do mar com area total de 115 km2, apresenta grande diversidade biologica e vegetativa e esta inserida em uma Area de Protecao Ambiental (APA). O estuario do Rio Vaza Barris vem sofrendo diferentes tipos de acoes antropicas: atividades de recreacao e lazer, intenso trafego de embarcacoes maritimas, cultivo de camarao em viveiros e tanques, desmatamento com possiveis queimadas e especulacao imobiliaria. Desta forma o presente trabalho visa compreender a distribuicao espaco-temporal dos marcadores geoquimicos, Hidrocarbonetos Alifaticos (HA) e Hidrocarbonetos Policiclicos Aromaticos (HPA), no sedimento superficial do estuario do Rio Vaza Barris, o processo de deposicao sedimentar, assim como o aporte e o impacto causado. Para o desenvolvimento do presente estudo, foram realizadas coletas em duas estacoes, (Inverno e Verao), no inverno foram 13 pontos com uma triplicata no ponto 13 (13a, 13b e 13c), no verao foram repetidos os 13 pontos anteriores e foram acrescentados outros dois, totalizando 15 pontos. Para a extracao dos hidrocarbonetos em sedimento, foi utilizada a extracao assistida por ultrassom tendo diclorometano como solvente de extracao. No clean-up (silica e alumina), foi utilizado n-Hexano para a eluicao da fracao de HA (F1) e diclorometano/n-hexano 1:1 para a eluicao da fracao de HPA (F2). As analises foram realizadas por Cromatografia a Gas/Espectrometria de Massas (GC-MS). Para a compreensao da distribuicao desses hidrocarbonetos na regiao, foram considerados alguns Indices de Razao Diagnostica (IRD). Os HA e seus isoprenoides (Pristano e Fitano) apresentaram recuperacoes entre 50,74 e 108,95% com recuperacao media acima de 60% e desvio padrao relativo RSD de 18,8%. Suas concentracoes variaram entre 0,19 Êg.g-1 a 8,5 Êg.g-1 de sedimento seco. O Indice Preferencial de Carbono (IPC) calculado para todos os pontos (exceto para VB2 e VB3 no inverno) associado as razoes °alifaticos/n-C16 e BMM/AMM (razao de Baixa Massa Molecular/Alta Massa Molecular) sugeriu aporte biogenico. Seus valores de RTA (Razao Terrestre Aquatica) e predominancia das cadeias impares e do homologo n-C29 indicaram aporte biogenico com significativa contribuicao de plantas terrestre superiores. As recuperacoes dos HPA variaram entre 45,46 e 163,0% com recuperacao media acima de 100% apresentando RSD de 28,31%. Suas concentracoes totais variaram entre 0,09 ng.g-1 a 410,4 ng.g-1 de sedimento seco, registrando niveis de concentracao acima do TEL (NOAA) e PQT (Environment Canada). Seus IRD indicaram uma mistura de aportes (petrogenico, pirolitico e de combustao de biomassa), com predominancia para o aporte pirolitico. Sua distribuicao mostra predominancia de compostos de alta massa molecular, registrando concentracoes expressivas para Benzo(a)pireno, Pireno, seguido do Benzo(b)fluoranteno e Benzo(a)antraceno, ambos considerados mutagenicos e carcinogenicos. A predominancia do aporte pirolitico pode ser justificada, por existir intenso trafego de embarcacoes no estuario e por ser uma regiao turistica