Polycyclic aromatic hydrocarbons (PAHs) in small island coastal environments: A case study from harbours in Guam, Micronesia

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants derived mainly from anthropogenic activities with minor contributions from natural sources (Law et al., 1997). Most PAHs enter the marine environment in urban runoff, municipal and industrial waste discharges, in bilge and fuel oil leaks associated with day-to-day shipping operations, and in oil spills from maritime accidents, and they are rapidly scavenged out of the water column by sediments (McElroy et al., 1989). Harbours, because of the associated shipping activities, are often sites of such marine pollution. Recent concern about the potential carcinogenic properties of some PAHs has led to an increased need to determine the extent of pollution caused by this group of compounds (Cerniglia and Heitkamp, 1989). Guam (13 28 0N, 144 45 0E) is the largest and most densely populated island in Micronesia and has served as the major shipping centre for the region for over 400 years. In spite of this, the impact of human activities on the island’s coastal environment has received little attention. This paper reports on the first major study of PAHs in the sediments and organisms in four local harbours (Fig. 1): Agana Boat Basin (small boat harbour located in the business centre of the island – 5 sites); the Outer Apra Harbour (heavily used commercial and military port for over 50 years – 30 sites); Agat Marina (newly constructed suburban facility – 4 sites); and Merizo Pier (small boat harbour and ferry terminal located in a rural residential area – 5 sites). The site locations and sampling collection details for sediments are given in Denton et al. (1997, 2005). PAH analyses were based on USEPA SW 846 methods (USEPA, 1996). All reagents used were analytical grade and all glassware was acid-washed and deionized water rinsed prior to use. Standard stock solutions were purchased from a commercial supplier. All analyses were performed in duplicate and were accompanied by appropriate method blanks and matrix spikes. Air-dried, sieved (1 mm) sediment samples (1–1.5 g) were weighed into a 10 mL Teflon centrifuge tube and extracted with methylene chloride (3 mL) in a commercial microwave oven (700 W)with a rotating turntable for sequential periods of 30, 15 and 15 s (Ganzler et al., 1986). Each tube was touched against a vortex mixer for 5 s between heating cycles to ensure thorough mixing. Upon standing overnight, the samples were further vortexed and centrifuged at 2500 rpm for 5 min. After decanting into 10 mL graduated glass centrifuge tubes, the samples were reduced in volume ( 0.75 mL) under a gentle stream of nitrogen in a water bath ( 45 C). Solvent exchange into hexane ( 1.25 mL) and further reduction in volume ( 0.5 mL) was necessary prior to clean up on silica gel (0.5 g) microcolumns (see Denton et al., 1997 The objective of BASELINE is to publish short communications on different aspects of pollution of the marine environment. Only those papers which clearly identify the quality of the data will be considered for publication. Contributors to Baseline should refer to ‘Baseline—The New Format and Content’ (Mar. Pollut. Bull. 42, 703–704).