Determination of aliphatic hydrocarbons in surface sediments of Mangueira Lagoon (RS—Brazil).

The Lagoa Mangueira (Magueira Lagoon) is a hydrological system with unique characteristics and extreme regional importance. Its water has been used for years, mainly in the production of irrigated rice in a practically closed recycling system. The fragility of this environment, the importance of its waters and the absence of data on the current impact justifies an assessment in relation to some geochemical markers. Hydrocarbons (HCs) in high concentrations in the environment are indicative of pollution. We studied the aliphatic content (AHs), unresolved complex mixture (UCM) and n-alkanes in the superficial sediments of Mangueira Lagoon, located in the state of Rio Grande do Sul in Brazil. Our aim was to assess the impact of hydrocarbons and characterize their sources. The methodology brought together were stages of pre-sonification, extraction by soxhlet and determination by gas chromatography coupled with mass spectrometry (GC/MS). Diagnostic indexes were: Preferred odd/even carbon index (PCI), terrigenous/aquatic ratio (TAR), UCM/∑n-alkanes ratio and Low molecular weight hydrocarbon (LMW) n-alkane/High molecular weight (HMW) ratio, indicated HCs of petrogenic and biogenic origins (aquatic andterrigenous). The concentrations of aliphatic hydrocarbons (AHs) (5.0 mg Kg⁻¹ ± 6.7% to 652.7 mg Kg⁻¹ ± 5.1%) and n-alkanes (0.6 mg Kg⁻¹ to 10.2 mg Kg⁻¹) indicate an environment, in general, slightly impacted, suggesting the west margin with greater collaboration for the entry of these geochemical markers. [ABSTRACT FROM AUTHOR]