Project Materials

LEVELS OF POLYCYCLIC AROMATIC HYDROCARBON IN FRESH WATER FISH DRIED UNDER DIFFERENT DRYING REGIMES

ABSTRACT

Fish can be preserved by drying in various heat regimes. However, there has been no complete comparison of the potential contamination associated with these drying regimens. The purpose of this study was to determine the quantities of PAHs that are likely to build in the bodies of freshwater fish dried using heat from charcoal, sun (sun drying), electric oven, and polythene-augmented drying regimes (burning of used cellophone materials). The amounts of sixteen PAHs were evaluated in fish samples collected from the Otuocha River in Anambra State, Nigeria. The fish samples were dried, pulverised, and extracted with n-hexane at 600 °C for 8 hours. The water content of the eluants was further reduced with florisil clean-up prior to gas chromatography-mass spectrometry measurement. Sun-dried fish included 35.7+0.2µg/g of PAHs, while oven-dried fish had 47.7+0.2µg/g, charcoal-dried fish had 79.53+0.2µg/g, and firewood-dried fish had 188.1+0.2µg/g. Charcoal drying with polythene resulted in a PAH level of 166.2 + 0.1µg/g, while fish dried with heat from burning firewood and polythene material resulted in a PAH concentration of 696.3 +0.2µg/g. Preliminary investigation of fresh water samples and undried fish samples (control) found that the fresh water contains total PAHs of 2.86+0.1µg/ml, whereas the fresh fish had 4.97+0.2µg/g. The concentration of PAHs in all dried fish using various drying methods was substantially greater than in the control.

Chapter one

INTRODUCTION

Polycyclic aromatic hydrocarbons (PAHs) are chemical compounds composed of two or more fused benzene rings (linear, cluster, or angular configuration), or carbon and hydrogen atoms arranged in rings of five or six carbon atoms.

They are referred to as “PAH derivatives” when an alkyl or other radical is added into the ring, and heterocyclic aromatic compounds (HACs) when one carbon atom in a ring is replaced by a nitrogen, oxygen, or sulphur atom.

PAHs are mostly derived from anthropogenic processes, particularly incomplete combustion of organic fuels. PAHs are widely diffused in the atmosphere. Natural events like volcanic eruptions and forest fires also contribute to the presence of PAHs in the environment (Suchanova et al., 2008).

PAHs can exist in both particulate and gaseous forms, depending on their volatility. Low molecular weight PAHs (LMW PAHs) with two or three aromatic rings (molecular weight from 152 to 178g/mol) are emitted in the gas phase, whereas high molecular weight PAHs (HMW PAHs) with five or more rings (molecular weight from 228 to 278g/mol) are emitted in the particulate phase (ATSDR, 1995).

PAHs in the atmosphere can photodegrade and react with other pollutants like ozone, nitrogen oxides, and sulphur dioxide. Because of their diverse sources and lasting properties, PAHs disseminate through air transport and are found practically everywhere.

There are hundreds of PAH compounds in the environment, but PAH analysis is often limited to the detection of six (6) to sixteen (16) molecules. Humans are exposed to PAH mixtures in ambient air, which can be gaseous or particulate.