Analysis of polycyclic aromatic hydrocarbons (Pah) in soil of mangrove forest of the venezuelan caribbean coast

Abstract

In order to identify the levels of contamination of mangrove soils by polycyclic aromatic hydrocarbons (PAH), their concentration was determined by gas chromatogra-phy coupled to mass spectrometry in the fraction of aromatic hydrocarbons obtained from soluble organic matter (SOM). Soils are located in Cuare Inlet and Morrocoy National Park from Venezuela, and samples were collected in Punta La Matica (PLM) and Tucacas Bay (ETU) respectively. Naphthalene, acenaphthene, acenaphthalene, benzo(ghi)perylene, dibenzo(ah)anthracene and indene have concentrations lower than the detection threshold for the technique employed (≤ 20 ng/g). Fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(k)fluoranthene, benzo(b)fluoranthene and benzo(a)pyrene present concentrations ranging from 24 to 967 ng/g, and in some cases were not detected (≤ 20 ng/g). The PAHs concentration are classified in a pollution level from moderate to high in ETU and low in PLM. These results indicate a major anthropogenic pollution level of soils from ETU in relation to PLM soils. Based on the fact that the PAHs detected are not substituted and dominate the 3-and 4-rings, three diagnostic ratios to identify the contamination source were cal-culated: [anthracene/(anthracene+phenanthrene), fluoranthene/(fluoranthene+pyrene); and benzo(a)anthracene/(benzo(a)anthracene+chrysene)]; these ratios suggest a source from combustion of organic matter. Additionally, the normalization of total PAHs related to total organic carbon (TOC) or SOM represents a linear relationship between total PAHs with PAH/TOC and PAH/SOM, and suggests that the PAHs detected are from the same source, that is, the combustion of organic matter from anthropogenic activity or natural fires.