عنوان مقاله [English]
During the last years, oil and gas exploration, extraction and refinery activities caused a lot of damage to the sensitive environment of the Persian Gulf. In the current study, the Pars Special Economic Energy Zone in the northern Persian Gulf was investigated, where oil and gas explorations, extractions, refineries and export infrastructures are concentrated. Each year, large amounts of petroleum-related pollutants discharge into the Persian Gulf in this region. In this research, the spatial distribution and the origin of oil-associated hazardous pollutants i.e., Polycyclic Aromatic Hydrocarbons (PAHs) in Assaluyeh Port were investigated.
Material and methods:
Fifteen samples of the surface sediment of the study area were collected in March 2016, using the Van Veen Grab sampler in five half lines perpendicular to the coast in phases one to five of the Pars Special Economic Energy Zone. Samples were packed in aluminum foils and transferred to the laboratory. Using freeze-drying process, the water was removed from the samples. Pollutants tend to accumulate in fine sediment particles due to the high specific surface area of these particles, and therefore, fine-grained particles (≥63 μm) were separated by physical screening. Finally, 16 compounds of PAHs, which are known as the toxic compounds by the U.S. Environmental Protection Agency (USEPA), were analyzed with gas chromatography-mass spectrometry. Total concentrations of the compounds were measured and their spatial distribution was illustrated using ArcGIS software. The origin of the observed Aromatic Hydrocarbons was also estimated using some indices.
Results and discussion:
Total concentrations of the 16 compounds ranged from 46.6 to 84.7 ng/g dry weight in the sampling stations. The source of compounds was identified using certain petrogenic multiple indices. Furthermore, the environmental risk of the presence of these compounds was estimated using the sediment quality guidelines of the state of Florid. It was shown that except for Naphthalene and Acenaphthene, concentration levels of other PAHs were lower than the threshold level, which is the concentration that destructive biological effects in benthic communities is rarely expected.
Total concentrations of 16 PAH compounds in the study area showed that the concentration of no compound exceeded the concentration of Effects Range, so it can be concluded that the possibility of harmful effects on benthos communities and other organisms in the food chain and also humans at the top of the chain is low. Considering the high rates of sedimentation and erosion and also the fossil origin of the pollutants, it seems that contaminations are continuously being buried under the new layers of sediment in the study area. Therefore, the continuing source of pollution could not cause serious contamination in the surface sediment of the region.