Ambient volatile organic compound (VOC) concentrations around a petrochemical complex and a petroleum refinery

Abstract

Air samples were collected between September 2000 and September 2001 in Izmir, Turkey at three sampling sites located around a petrochemical complex and an oil refinery to measure ambient volatile organic compound (VOC) concentrations. VOC concentrations were 4–20-fold higher than those measured at a suburban site in Izmir, Turkey. Ethylene dichloride, a leaded gasoline additive used in petroleum refining and an intermediate product of the vinyl chloride process in the petrochemical complex, was the most abundant volatile organic compound, followed by ethyl alcohol and acetone. Evaluations based on wind direction clearly indicated that ambient VOC concentrations measured were affected by the refinery and petrochemical complex emissions. VOC concentrations showed seasonal variations at all sampling sites. Concentrations were highest in summer, followed by autumn, probably due to increased evaporation of VOCs from fugitive sources as a result of higher temperatures. VOC concentrations generally increased with temperature and wind speed. Temperature and wind speed together explained 1–60% of the variability in VOC concentrations. The variability in ambient VOC concentrations that could not be explained by temperature and wind speed can be attributed to the effect of other factors (i.e. wind direction, other VOC sources).

Introduction

Volatile organic compounds (VOCs) in the urban and industrial atmosphere mainly originate from motor vehicle exhausts and other combustion processes utilizing fossil fuels, petroleum storage and distribution, solvent usage and other industrial processes. Leaks, as well as regulated emissions, contribute to ambient concentrations of VOCs. Emission from vegetation is also an important source of some highly reactive hydrocarbon species (Kalabokas et al., 2001). Several effects of VOCs are recognized, such as their contribution to stratospheric ozone depletion, tropospheric photochemical ozone formation, toxic and carcinogenic human health effects, and enhancement of the global greenhouse effect (Dewulf and Langenhove, 1999).

Petroleum refineries and petrochemical plants are generally large industrial installations. Their operation is associated with the emission of various organic compounds into the atmosphere, mainly originating from the production processes, the storage tanks and the waste areas (Kalabokas et al., 2001). In petrochemical industries, most of the organic compounds are derived from petroleum fractions, and actually from only a few basic hydrocarbons such as methane, ethane, propane, benzene, toluene, and xylene (Crosby, 1998). Petroleum refining is the physical, thermal and chemical separation of crude oil into its major distillation fractions. The primary products of the industry fall into three major categories (EPA, 1995): fuels (motor gasoline, diesel and distillate fuel oil, liquefied petroleum gas, jet fuel, residual fuel oil, kerosene and coke); finished non-fuel products (solvents, lubricating oils, greases, petroleum wax, petroleum jelly, asphalt and coke); and chemical industry feedstocks (naphtha, ethane, propane, butane, ethylene, propylene, butylenes, butadiene, benzene, toluene and xylene). Leaks, burning of fuels in process heaters and various refinery processes are the emission sources in refineries (EPA, 1995). Along with VOCs, various other pollutants (i.e. sulfur dioxide, reduced sulfur compounds, carbon monoxide, nitrogen oxides and particulate matter) are emitted from petroleum refineries (Buonicare and Davis, 1992).

Recently, atmospheric concentrations of hydrocarbons were measured at several sites around an oil refinery near the city of Corinth, Greece (Kalabokas et al., 2001). This study by Kalabokas et al. (2001) indicated that the ambient air concentrations of saturated and aromatic hydrocarbons in a large area surrounding an oil refinery were lower than the ambient air quality standards and the ambient air concentrations measured in the two large urban centers in Greece.

Izmir metropolitan city, with a population of 2 700 000 is the center of a highly industrialized area on the Aegean Sea shoreline of Turkey. There are many industries emitting high quantities of air pollutants in the area. A petroleum refinery and a connected petrochemical complex are located at approximately 60 km northwest of Izmir city center in the Aliaga region. The refinery processed 9.14×10⁶ t of crude oil in 2001 and produced 8.42×10⁶ t of petroleum products (liquefied petroleum gas, naphtha, unleaded gasoline, premium gasoline, regular gasoline, jet fuel, kerosene, gas oil, heating oil, fuel oil No 6, asphalt, lubricating oil, extract, wax and sulfur). The petrochemical complex has a production capacity of 1.28×10⁶ t year⁻¹. Its major products are caustic soda, hypochlorite, liquefied chlorine, polyvinyl chloride, low-density polyethylene, high-density polyethylene, ethylene glycol, polypropylene, acrylonitrile, aromatic oil, benzene, gasoline, phthalic anhydride, p-xylene and pure terephthalic acid. A recent study by Elbir (2002) indicated that the fuel oil use in Aliaga is high due to the petroleum refinery and petrochemical plant, accounting for 69% of high-sulfur fuel oil used in Izmir area. The petroleum refinery and petrochemical plant are the largest sources of air pollution in the region, together contributing approximately 72% to total industrial SO₂ emissions and 66% to overall SO₂ emissions (Elbir, 2002).

The objectives of this study were: (1) to measure VOC concentrations around a petrochemical complex and a petroleum refinery; (2) to investigate the effect of meteorological parameters (wind speed, wind direction and temperature) on the concentrations measured; and (3) to compare the concentrations measured with the values measured in urban and suburban sites in Izmir, Turkey and other sites around the world.