Keywords

Highlights

  • The concentrations of the PAHs are distributed in all molecular weight range.

  • PAHs were detected and were found in the range of 563–1,037 ng/g (dryweight).

  • There were 26 compounds of PAHs detected in the samples.

Introduction

Rapid anthropogenic activities have brought about an increase in environmental pollution along the Malaysian coastal environment for decades. Malaysian coasts are subjected to various threats from petroleum pollution including routine and accidental oil spills from tankers, spillage of crude oils from inland and offshore oil fields and run-off from land-based human activities. Selangor is divided into nine administrative districts, one of those is the town of Kuala Selangor which lies in the lower reaches of Selangor River. The Kuala Selangor River is chosen for the study because the river flows through the hub of commercial, industrial and residential areas. Polycyclic aromatic hydrocarbons (PAHs) are example of hydrocarbon pollutants which may originate from sea and land-based. Petrogenic PAHs are hydrocarbons consisting of low molecular weight components and their presence is normally associated fresh input from lateral transport. Examples of petrogenic sources are crude oil, asphalt and gasoline are introduced to the environment through accidental oil spills, discharge from routine tanker operation, as well as municipal and urban run-off. Petrogenic sources with lower molecular weight PAHs (2–3 rings) are more water soluble and readily bioavailable for aquatic animals. Higher level of petrogenic PAHs were found to be accumulated in various organisms. Malaysian sedimentary PAHs impacted by petrogenic sources (Zakaria et al. 2002; Sakari et al. 2008) is unique compared to other industrial countries reported pyrogenic as the main source of sedimentary PAHs (Larsen and Baker 2003; Liu et al. 2009). On the other hand, pyrogenic sources are incomplete combustion of organic matter, biomass burning and mobile sources released to environmental in the form of exhaust and solid residue (Liu et al. 2009; Retnam et al. 2013). Pyrogenic PAHs are more toxic but less bioavailable due to their complex molecular structure and composition. Their concentration is usually high in urban zones but, due to their high diffusion rates and the ability to accumulate in particles, PAHs are easily transported through the air, and are subsequently deposited in soils and waters, sometimes far from the origin sources. Generally soil sites are located too near to potential sources of PAHs such as towns and oil tankers route especially along the Straits of Malacca. The purpose of this research is to determine the distribution of PAHs in the different sampling stations in Kuala Selangor river. Therefore, this study should be able to give some indication of the concentration or level of PAHs in the Kuala Selangor region. In order to promote the understanding of PAHs distribution, this paper also discusses the relationship between sedimentary PAH levels and OC content in the sediments.

Materials and Methods

Selangor River is one of the major rivers in Selangor, Malaysia. It runs from Kuala Kubu Bharu in the east and empties into the Straits of Malacca at Kuala Selangor in the west. The total river catchment’s covers an area of approximately 1,960 km2. The map of sampling locations with detail data are shown in Fig. 64.1. Seven surface sediment samples were collected. 15 g of freeze-dried sediment samples were placed in pre-cleaned cellulose thimbles and soxhlet extracted for about 8–10 h with distilled dichloromethane (DCM). Clean up step is done by using 5 % H2O deactivated silica gel to separate unwanted polar compounds and packed in the column until 9 cm in heights. The 2nd step column chromatography or fraction step is done using 100 % fully activated silica gel. The sample from first column was added to the column and charge through with 4 ml hexane to get alkanes and hopanes fraction, then 4 ml hexane added again to get LABs fraction, and finally 16 ml of Hexane/DCM (3:1 v/v) was added to get PAHs fraction. The extract was analyzed with GCMS.

Fig. 64.1
figure 1

Sampling stations along the coastline of Kuala Selangor River

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Results and Discussion

The concentrations of 26 PAH and some related parameters are . The total concentrations of the 26 PAHs (∑PAHs) in the sample sediments taken from Kuala Selangor River varied significantly (p < 0.05) among the stations and ranged from 563 to 1,037 ng/g (dryweight) (Fig. 64.2). Moreover, it was found that the highest concentration of the total PAHs was recorded in stations three and five which are located near the Kuala Selangor Bridge and jetty (Fig. 64.1). Based on these results as, the concentrations of the PAHs in Kuala Selangor river stations are distributed in all molecular weight range (i.e. low and high molecular weight PAHs). N-Methylphenanthrene (n-MP) is the most abundant parameters which are relative to other PAHs in the samples.

Fig. 64.2
figure 2

Concentrations of PAHs in sampling stations in Kuala Selangor River

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This could be due to the fresh input of PAHs to the landfills such as illegal dumping of waste petroleum products although more data is needed to confirm this suggestion. The results also showed that those PAHs with low molecular weight are more volatile and more bio available than those PAHs having higher molecular weight. Therefore, the availability of Methylphenanthrenes in high concentration is a good indication of this fresh input. Previous research attributed such fresh input of a single diffuse source to the presence of high abundance of Methylphenanthrenes (Zakaria et al. 2005). However, regarding Benzo (k) fluoranthene (BkFl), Benzo (a) pyrene (BaPy), Indeno [1,2,3-cd] pyrene (IndPy) and Benzo [g,h,i] perylene (BghiPer), they were all available in relatively high concentrations. Such compounds are described as carcinogen and mutagen compounds which are capable of disrupting the endocrine system in human body. The results of this study also revealed that the second highest concentration of total PAHs was obtained from the samples taken from station one, four and six which are located in the coastal area of the Strait of Malacca facing the Kuala Selangor port. Furthermore, the samples from station two which is located at Kuala Selangor River displayed the lowest total concentration of PAHs. In this study, the PAHs compositions found in Station one which is located in the upstream of the mangrove estuary were compared for further analysis. SS7 known as soil sample around the sampling sites were collected and analyzed to identify the sources of PAHs. The results show that the high concentrations of PAHs in the sediment sample were 3-Methylphenanthrene (3Mp), 2-Methylphenanthrene (2Mp), Benzo (k)fluoranthene (BkFl), Indeno[1,2,3-cd]pyrene (IndPy) and Benzo[g,h,i] perylene (BghiPer), indicating extensive input of petrogenic PAHs. As proposed by Youngblood and Blumer (1975), many previous studies used the ratio of methylphenanthrenes to phenanthrenes (MP/P) was for the purpose of distinguishing between petrogenic and pyrogenic sources of PAHs (e.g. Zakaria et al. 2002; Sakari et al. 2008; Bakhtiari et al. 2010). As for the methylphenanthrenes, they comprise 3-methylphenanthrene, 2-methylphenanthrene, 9-methylphenanthrene and 1-methylphenanthrene. These all are divided by the phenanthrene concentration. In this study, it was found that the MP/P ratios for all sediment samples (MP/P ratio) were >1.0. Such result implies that sedimentary PAHs in all stations mainly tend to be petrogenic PAHs (Table 1). The significant correlation between PAHs in the sediments and sediments’ OC is achievable only in highly contaminated sites where the total PAH concentrations were >2,000 ng/g. For the current study, the sample sediments collected from all stations showed total PAH concentrations less than this value. Therefore, it can be concluded that the distributions and concentrations of PAHs in sediments of Kuala Selangor River are not controlled by the sediments’ OC content.

Conclusion

The total concentrations of the 26 PAHs (∑PAHs) in the sample sediments taken from Kuala Selangor River varied significantly (p < 0.05) among the stations and ranged from 563 to 1,037 ng/g (dryweight). Moreover, it was found that the highest concentration of the total PAHs was recorded in stations three and five which are located near the Kuala Selangor Bridge and jetty. The concentrations of the PAHs in Kuala Selangor river stations are distributed in all molecular weight range (i.e. low and high molecular weight PAHs).