Persistent organic pollutants influence the marine benthic macroinvertebrate assemblages in surface sediments of Nayband National Park and Bay, Northern Persian Gulf, Iran.

Macroinvertebrate communities have been influenced by chemical substances, originated from petrochemical developments, that caused many problems in the marine biota. This study investigated the surface sediments of Nayband National Park and Bay (northern Persian Gulf) for polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs) in terms of their distribution, source, and impacts on benthic macroinvertebrate assemblages. To this end, a total of 180 surface sediment samples from 20 stations were collected using Van-Veen grab sampler during winter 2018. The concentration of PAHs, TPHs, total organic carbon (TOC). and total organic matter (TOM) were evaluated, and grain size measurements were conducted on sediment samples in this study. Benthic macroinvertebrates were then identified in terms of presence and distribution. The results indicated that coarse granulometric fractions of sands were prevalence in all samples stations. The total concentration of PAHs ranged from 47.57 to 657.68 ng/g and TPHs 5.72 to 42.16 µg/g dw. The risk of ΣPAHs and TPHs in the sediments was relatively low to moderate according to the sediment quality guidelines. Analysis of the results revealed a significant negative correlation between ΣPAHs (R-value = - 0.917; P < 0.01), TPHs (R-value = - 0.849; P < 0.01) and macrofaunal abundance. Findings demonstrated that the species richness and abundance were at the lowest levels in stations where concentrations of PAHs, TPHs, TOC, and TOM were in the highest values, suggesting that these contaminants could negatively influence the benthic organisms in Nayband National Park and Bay. The results of correspondence analysis (CA) and principal component analysis (PCA) analysis showed that sedimentary habitats in Nayband National Park and Bay are being negatively affected by PAHs and TPHs, released from Pars Special Economic Energy Zone (PSEEZ). Moreover, the marine biotic index (AMBI) and Shannon-Weiner Diversity (H') results suggest that Nayband National Park and Bay can be classified as slightly to moderate polluted area. In conclusion, Northern Persian Gulf is significantly affected by oil industry developments and petrochemical activities. The unique ecosystem like Nayband National Park and Bay has been in a cautious status in terms of the PSEEZ pollutants and the levels of PAHs and TPHs concentration, warning that urgent environmental programs should be considered to protect the diversity and ecology of this valuable marine systems.

An evaluation of CO, CO2, and SO2 emissions during continuous and non-continuous operation in a gas refinery using the AERMOD.

Air quality modeling can be considered as a useful tool to predict air quality in the future and determine the control strategies of emissions abatement. In this study, the AERMOD dispersion model has been applied as a tool for the analysis of the values of pollutant emissions from the flares of the Maroon gas refinery located in the suburb of Ahvaz, Iran. First, the values of pollutant emissions from the refinery's flares were investigated by measurement and using the emission factors during cold and warm seasons of 2018. The gas burns continuously in two flares and the other 11 flares are used in emergency situations and only their spark plugs are lit. The type of compounds and their molar, volumetric, and weight percentages were determined by gas chromatography (GC) injection. By entering data such as emission rate, flare characteristics, and topographic and meteorological data of the study area into the AERMOD model, dispersion of pollutants was predicted by using the AERMOD model in the region with an area of 2500 km2. The statistical evaluation showed that the maximum 8-h concentration of CO in the cold season was 133441 µg/m3 which was higher than the standard and reached 9755 µg/m3 in the warm season that was close to the standard. The maximum hourly concentration of SO2 was in the cold season with 215 µg/m3 that was higher than the standard value, occurred in a local scale of 50 km2. This can be attributed to the high concentration of SO2 wet deposition. According to the direction of the wind from the northwest, pollutant emissions can lead to adverse health effects on the population of refinery employees, residents around the refinery, and occupants of passing vehicles. The concentration of pollutants generated due to the high volume of heavier compounds in the gas in the winter season was higher than that of the warm season. Comparison of maximum concentrations of the predicted results with the national and international standards showed that SO2 and CO concentration is higher than standard values. In total, according to the evaluation of the predictions made, the performance of the AERMOD model was acceptable in the prediction of pollutant concentrations in the study area.

CO2 chemical absorption from fluid catalytic cracking unit flue gases of Abadan Oil Refinery in Iran, using diethanolamine solvent.

The Fluid Catalytic Cracking Unit process converts heavy vacuum gas oil into more valuable products in the presence of zeolite catalyst at 520 °C and 2.5 bar. The coke is burned off with air in the regenerator tower at 700 °C and 230 ton / h of flue gases are produced. The flue gases consist of CO2 (12.7% mole), N2 (66.2% mole), H2O (19.2% mole), O2 (1.7% mole), and SO2 (0.2% mole). In this study, the chemical absorption of CO2 in an absorption and desorption pilot plant was investigated and this process was simulated by Aspen Hysys. The pilot plant used has an absorber tower of 15 cm in diameter and a stripper tower of 10 cm. The towers were filled up to 1.5 m with 3-mm Raschig ring packing. A concentration of 30 wt% diethanolamine (DEA) solvent is used for CO2 absorption. Absorption was carried out at 1.1 bar, solvent temperature of 40 °C, flue gas temperature of 60 °C, and liquid to gas ratio (L/G = 3.7). Amine regeneration was carried out at 125 °C and 1.9 bar. The CO2 absorption efficiency in the pilot plant was obtained 96% and in Aspen Hysys simulation its 95%. The CO2 recovery efficiency in the stripper tower obtained 95% and CO2 purity is 94.6%. The overall efficiency of the chemical absorption with this process is 92%, and the regeneration energy in the stripper tower is 2.52 GJ/ton-co2. With this method, 1003 ton/day CO2 is captured from the FCCU flue gases and preventing emission to the atmosphere.

Ecological risk of potentially toxic elements (PTEs) in sediments, seawater, wastewater, and benthic macroinvertebrates, Persian Gulf.

In the current study, ecological risk of potentially toxic elements (PTEs) in sediments, seawater, wastewater, soft tissues and shell of a major fouling species Callista florida (C. florida) and soft tissue of rocky oyster, Saccostrea cucullata (S. cucullata) are investigated. For this purpose, 25 sediment samples, 24 seawater samples, 28 wastewater samples, and 100 bivalve samples were collected for PTEs analysis. Risk index (RI) and sediment quality guidelines along with calculated enrichment factors (EF) and PTEs profiles revealed that Musa Estuary is threatened by contamination, especially with respect to Hg, Cu, and Zn. The decreasing trend of average element enrichment factor is: Hg > Cu > Ni > Cd > Zn > Co > Cr > Mn > Fe > As > Pb > Mo > Sb. Among the investigated elements, Hg indicated the highest potential ecological risk factor in sediment (RI and EF are 1341.6 and 214.66 close to the industrial area). The Ficklin chart results demonstrated that seawater samples almost plot in regions with high metal load and pH values were the same. Mean concentrations of PTEs in water samples were 1.2 (for Cu) to 6565 (for Hg) times higher than world seawater. Regarding wastewater, pH values changed from very acidic to alkaline while PTEs load ranged from low to high load. In general, PTEs concentration in water samples was higher compared to those of the world seawater. Based on the results obtained in this biomonitoring study, elevated concentrations of Al, Fe, Cu, and Zn were found in soft tissue of C. florida and S. cucullata. Statistical analysis revealed significant differences in PTEs concentration between the two studied species. Generally, most PTEs concentration including Al, Co, Cr, Fe, Mn, Ni, Pb, and Sb in soft tissue fall between water and sediment samples i.e., sediment > biota > water.