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Organotin and Irgarol-1051 contamination in Singapore coastal waters
Marine Pollution Bulletin 44 (2002) 697–703 www.elsevier.com/locate/marpolbul
Baseline
Edited by Bruce J. Richardson
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).
Organotin and Irgarol-1051 contamination in Singapore coastal waters C. Basheer a, K.S. Tan
b,*
, H.K. Lee
a
a
b
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore Tropical Marine Science Institute, National University of Singapore, 14 Kent Ridge Road, Singapore 119223, Singapore
Abstract The seas surrounding Singapore are principally utilized by the shipping industry but are now also increasingly used for a variety of other purposes, including desalination for supplies of drinking water and intensive aquaculture of food fish. While stringent environmental pollution standards are in place for industrial effluents, there is currently no legislative control over pollution from antifouling paints in Singapore. In this study, the concentrations of toxic antifouling agents tributyltin (TBT), triphenyltin (TPhT) and Irgarol-1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine) were determined from seawater obtained from 26 locations along and off the coast of Singapore in October and November 2000. These compounds were isolated by liquid–liquid extraction derivatized under controlled microwave heating and quantified by gas chromatography–mass spectrometry. TBT concentrations in seawater ranged between 0.43 and 3.20 lg l1 with a mean value of 1:40 0:60 lg l1 . The mean values of DBT and MBT were 1:07 0:80 lg l1 and 0:34 0:50 lg l1 respectively, while TPhT concentrations of up to 0.40 lg l1 were found. Monophenyltin and diphenyltin were not detected in all samples analysed. Irgarol-1051 was found to be present at concentrations of between 3.02 lg l1 and 4.20 lg l1 in seawater with a mean value of 2:00 1:20 lg l1 . Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Antifouling paints; Tributyltin; Irgarol-1051; Microwave-assisted derivatization
Antifouling compounds are incorporated into marine paints used to coat hulls of ships. This is done in order to prevent marine organisms from attaching onto the hull surfaces, thus enhancing fuel efficiency as well as increasing the service life of ships. Various antifouling strategies have been used to prevent such marine growth. The principal antifouling compound in use for the last four decades is tributyltin (TBT) (Bennett, 1996; Champ and Seligman, 1996). While organotin compounds are extremely toxic (Fent, 1996; Morcillo and *
Corresponding author. Fax: +65-77 49654. E-mail address: [email protected] (K.S. Tan).
Porte, 1998), usage of TBT-based antifouling paints is estimated to save the shipping industry some US$5.7 billion per annum (Rouhi, 1998). The annual fuel savings alone are estimated to be 7.2 million tons per year (Bennett, 1996). At the same time, however, organotin compounds are released into the marine environment, which can result in adverse effects on non-target organisms, even at extremely low concentration levels (Beaumont and Newman, 1986; Bryan et al., 1988). In response to increasing public concerns over their deleterious effects on the marine environment, the International Maritime Organisation has implemented a series of recommendations banning the use of TBT-based
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paints by 2003 (Julian, 1999). This has forced the antifouling industry to find alternatives to organotins. A common formulation now in use is to combine copper compounds with an algicide such as Irgarol-1051 (2methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine) (Steen et al., 1997) an s-triazine compound. There are currently over 80 products containing Irgarol-1051 registered for use as antifouling paints (HMSO, 1994). The level of TBT has declined in countries where regulations governing the use of organotin-based antifouling paints are in effect, but at the same time, environmental levels of other toxic antifouling compounds such as Irgarol-1051 have increased (Readman et al., 1993). A recent toxicological study of Irgarol-1051 showed that this compound is highly toxic to non-target marine algae and that it is sufficiently stable to reach toxic concentrations in the environment (Dahl and Blanck, 1996). The mode of action is based on the inhibition of photosynthetic electron transport in chloroplasts (Mets and Thiel, 1989). Irgarol-1051 inhibits photosynthesis at concentrations lower than 1 lg l1 (De Noyelles et al., 1982). It is feared that Irgarol-1051 might inhibit the growth of algae along shorelines, changing biological communities and altering the ecology of coastal areas. The waters surrounding Singapore not only serve as a waterway for vessels plying the Straits of Malacca, but function as one of the world’s busiest harbours, supporting substantial container-handling and oil-refining industries. Singapore has stringent environmental pollution controls over land-based sources, and industrial effluents are strictly monitored with heavy fines imposed on law breakers. However, the more insidious problems caused by antifouling compounds leaching into Singapore waters have not been addressed adequately. There is currently no legislation controlling the use and disposal of organotin-based antifouling compounds in Singapore. The Ministry of Environment to this date monitors neither TBT nor Irgarol. Plans for desalination of coastal waters to supply drinking water to the general public and high-density culture of food fish in Singapore waters within port limits are two future activities that demand monitoring of toxic organic pollution in the sea. This paper provides a first look at the antifouling agents TBT and Irgarol-1051 in Singapore waters. In order to analyse and quantify non-polar organotin and triazine compounds in environmental samples using gas chromatography, derivatization of these compounds is a critical step in sample preparation. Classical derivatization using Grignard reagent is a multi-step, time-consuming process, which is adversely affected by humidity. To overcome this problem, direct derivatization of analytes using sodium tetraethylborate (NaEt4 B) was used under microwave heating to obtain clear separation and complete derivatization of organotins and Irgarol-1051 in a single step. This method was employed to quantify organotin and Irgarol-1051 in coastal waters
around Singapore. It is envisaged that the rapid method will provide for a more efficient means to monitor the marine environment in Singapore. A CEM (Matthews, NC, USA) MARSx Sx -CEM Corporation (USA) microwave extraction system (maximum power: 1200 W) was used in this work. All quantitative analyses were carried out using a Shimadzu QP-5050 GC–MS system with an auto sampler (AOC20i). Ionisation was carried out by electron impact (EI). A DB-5 (30 m 0:32 mm i.d., 25-lm film thickness) general-purpose column obtained from J and W Scientific (Folsom, CA, USA) was used. The optimised temperature programme was as follows: initial temperature 50 °C (hold for 2 min), increased by 20 °C min1 to 140 °C and further increased to 220 °C at 7 °C min1 . The final temperature was 280 °C, achieved at a rate of 15.3 °C min1 . Injector and detector temperatures were set to 280 and 300 °C, respectively. Helium carrier gas was maintained at a flow rate of 1.5 ml min1 . EI ionisation energy level was set at 70 eV and the mass range between 40 and 400 m/z. All glassware was washed with detergent and tap water, soaked in 10% HNO3 for 12 h and subsequently rinsed with deionised water and acetone before use. Monobutyltin (MBT) trichloride (95%), dibutyltin (DBT) dichloride (98%), tributyltin (TBT) chloride (96%), monophenyltin (MPhT) trichoride (99%), diphenyltin (DPhT) dichloride (95%), triphenyltin (TPhT) chloride (99%), and tetrabutyltin (TeBT) (>97%) were purchased from Merck (Germany). Irgarol-1051 was obtained from Ciba Geigy (Switzerland). All other analytical-grade solvents and chemicals were purchased from Merck and Fluka (USA). Sodium tetraethylborate (NaEt4 B) was obtained from Strem chemicals (USA). A 2% (w/v) NaEt4 B solution was prepared daily using Milli-Q (deionised) water. Acetate buffer (pH 5) was prepared by dissolving 1 M sodium acetate in Milli-Q water and adjusted to pH 5.00 using concentrated acetic acid. Stock solutions of MBT, DBT, TBT, MPhT and DPhT were prepared (5 mg ml1 ) in hexane, whereas TPhT and Irgarol-1051 were prepared in ethyl acetate (5 mg ml1 ). Organotins were derivatized with NaEt4 B using acetate buffer (pH 5). The MARS microwave system was used at 60% power for 3 min. A seven-point calibration curve was plotted with a concentration range of 10–2000 ppb (R2 ¼ 0:99). Mixtures of working solutions were prepared daily in hexane from stock solutions. TeBT was used as an internal standard. Seawater samples were collected from 26 locations (see Table 1) along the Singapore coastline over a period of two months during October and November 2000. The salinity of seawater ranged between 28 and 35 ppt; the temperature and pH of the samples ranged from 28 to 32 °C and from 7.9 to 8.6, respectively. All samples were collected during the day, in 1-l HDPE Nalgeneâ bottles which were previously washed with dilute nitric acid and
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Table 1 List of sampling locations and their proximity to potential sources of antifouling contaminants Site no.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Locations
Sembawang Park Punggol Pasir Ris Changi Off Pulau Tekong East Coast Park Off East Coast Park Marina East Off Marina East St. John’s Island Sister’s Island World Trade Centre Labrador Park Pulau Jong Pulau Satumu Pulau Hantu Cyrene Reef West Coast Park Jurong Island Jurong Pier Sultan Shoal Tuas jetty Raffles Marina Sarimbun Lim Chu Kang Kranji
Coordinates Latitude
Longitude
1.28.200 1.25.030 1.23.400 1.22.040 1.22.050 1.18.420 1.17.150 1.17.500 1.16.180 1.13.120 1.12.950 1.15.860 1.17.030 1.12.550 1.09.600 1.14.440 1.15.190 1.17.750 1.15.510 1.18.580 1.14.430 1.17.460 1.20.070 1.26.030 1.27.350 1.25.920
103.49.480 103.54.080 103.57.030 104.05.500 104.02.540 103.56.200 103.54.100 103.52.030 103.52.170 103.51.030 105.50.070 103.49.350 103.46.970 103.47.260 103.44.840 103.38.920 103.45.100 103.43.930 103.42.230 103.42.690 103.38.920 103.37.340 103.39.300 103.41.020 103.41.660 103.44.600
N N N N N N N N N N N N N N N N N N N N N N N N N N
E E E E E E E E E E E E E E E E E E E E E E E E E E
Date of collection (dd mm yyyy)
Potential source of antifouling contaminant
TBT/DBT
TBT/ MBT
‘‘Total’’ antifouling compound concentration (TBT þ Irgarol, in lg l1 )
13.11.2000 03.11.2000 07.11.2000 06.11.2000 16.10.2000 16.10.2000 02.11.2000 09.10.2000 25.10.2000 07.11.2000 25.10.2000 04.10.2000 05.10.2000 05.10.2000 01.11.2000 25.10.2000 02.11.2000 10.10.2000 27.10.2000 13.11.2000 20.10.2000 09.10.2000 12.10.2000 27.10.2000 02.10.2000 02.10.2000
Sy, P P, J, M Sy M, J SL – – P P SL SL P P SL LH SL SL M, J P J, Sy SL, LH J, Sy M, J – J –
1.3 1.0 3.6 0.9 0.8 1.1 1.0 1.0 0.4 0.9 0.9 0.5 4.0 0.4 0.0 1.3 5.0 1.0 2.1 3.6 0.9 3.0 1.1 1.3 0.0 6.0
3.8 1.2 0.0 4.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.4 0.0 0.0 1.3 0.0 0.0 0.0 0.0 0.0 0.0 1.2 0.0 0.0 0.7 1.8
4.06 5.12 4.22 4.99 1.66 5.23 1.90 1.95 0.52 0.88 0.88 2.98 2.85 0.69 1.42 0.89 3.02 2.41 1.93 2.71 1.10 3.78 4.52 1.37 1.38 2.57
The contamination ratios of TBT/DBT and TB/MBT as well as the sum of TBT and Irgarol-1051 contaminations are also provided for each location. (J––Jetty; LH––Lighthouse; P––Port; M––Marina; SL––Shipping lane; Sy––Shipyard).
rinsed in deionised water. Offshore samples were collected from the side of a boat. In order to determine within-location variability, we also collected samples from within a 10-m distance range. Organotin and Irgarol-1051 concentrations in six samples collected from one locality were not significantly different and subsequent sampling was limited to one seawater sample per site. All samples were collected and analysed on the same day. Extraction was performed on unfiltered samples, as the amounts of suspended particles were found to be negligible in surface water. Organotins and Irgarol-1051 were spiked with laboratory seawater (Instant Oceanâ seasalt dissolved in deionised water) made up to a salinity of approximately 32 parts per thousand. Two hundred ml of seawater sample was used to perform extraction with spiked organotins and Irgarol-1051 with 20 ml of 3:2 ethyl acetate:hexane solvent mixture containing 2 ml of saturated NaCl. The pH of the sample was reduced to 2 by adding 6 N hydrochloric acid. Liquid–liquid extraction (LLE) was performed twice with the solvent–seawater mixture. The resulting organic layer was then subjected to derivatization under microwave (60% power, 3 min for 110 °C and held for 3 min) with 5 ml of freshly prepared NaEt4 B solution, 5 ml of pH 4 acetate buffer and 1 ml of
Table 2 Recovery test of ethylated organotins and Irgarol-1051 and their detection limits Analyte
Calibration R2 -value
Mean recovery (%)
RSD% ðn ¼ 3Þ
LOD (ng l1 )
Monobutyltin Dibutyltin Tributyltin Monophenyltin Diphenyltin Triphenyltin Irgarol-1051
0.998 0.998 0.998 0.998 0.995 0.998 0.993
73 92 91 87 70 94 88
5.54 5.58 3.65 4.72 8.85 4.20 6.30
6 5 6 5 12 4 10
R2 ––correlation coefficient; RSD––relative standard deviation; LOD–– limit of detection.
nonane. The addition of n-nonane minimized loss of analytes under microwave radiation at high temperature. After derivatization, the organic layer was separated and trace amounts of water were removed by adding anhydrous Na2 SO4 . Finally the extract was concentrated to 1 ml under a stream of nitrogen, made up with hexane to 1 ml and 1 ll was injected into the GC–MS. Recoveries of organotin and Irgarol-1051 are shown in Table 2. In the classical method of sample preparation using a Grignard reagent, derivatization is a
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Fig. 1. Distribution of MBT, DBT and TBT in Singapore coastal waters. Samples were collected from 26 locations along Singapore Straits and the Straits of Johor during October and November 2000. Geographical coordinates for the locations are given in Table 1.
multi-step process that is complex, tedious and time consuming. In addition, only 50–60% of compounds are typically derivatized with the classical method. Ethylation using NaEt4 B coupled with microwave heating is simpler and faster than the classical methods and clear baseline and separation were obtained in this way. A typical routine classical method would take up to 4 h for extraction and derivatization alone, as compared to the current method using combined LLE microwave, which required only half an hour for extraction and derivatization. TBT and its degradation products (either as DBT or MBT) were present in samples from all 26 sampling locations (Fig. 1). The highest amounts of TBT (3.20 lg l1 ), DBT (3.80 lg l1 ) and MBT (1.60 lg l1 ) were detected in samples from Singapore Straits. The mean values ðn ¼ 26Þ obtained for TBT, DBT and MBT were 1:44 0:60, 1:07 0:80 and 0:34 0:50 lg l1 , respectively. TBT concentrations ranged from 0.43 to 3.20 lg l1 (Fig. 1), with high concentrations occurring in samples obtained from Cyrene Reef, Pulau Jong and Jurong Pier in the vicinity of Jurong Island (locations 17, 19, 20; Fig. 1). Samples obtained from other locations (e.g., World Trade Centre and Labrador Park; locations 12, 13) in the Singapore Straits also contained TBT up to 1.90 lg l1 . Seawater from locations along the northeastern coast of Singapore (locations 2–7) contained between 1.40 and 2.40 lg l1 of TBT. In northwestern coastal areas, TBT concentrations between 0.69 and 3.2 lg l1 were found. DBT was detected in 24 locations (except Pulau Satumu and Lim Chu Kang) where concentrations ranged between 0.61 and 3.83 lg l1 . MBT was detected at only eight locations,
where concentrations ranged between 0.35 and 1.58 lg l1 (see Fig. 2). High ratios of TBT/DBT (Table 1) were found in the Singapore Straits (Cyrene Reef, 5.0; Jurong Pier, 3.6; and Tuas Jetty, 3.0), as were samples from the Straits of Johor (Kranji, 6.0; Pasir Ris, 3.5; Sarimbun, 1.3; and Sembawang Park, 1.2). The ratios of TBT/MBT (Table 1) from the Straits of Johor were also high (Changi, 4.9; Sembawang Park, 3.8; Kranji, 1.8). In contrast, samples from Singapore Straits had generally lower TBT/MBT ratios (World Trade Centre, 1.3; Pulau Satumu, 1.3; Tuas Jetty, 1.2). TPhT was surprisingly detected at only one location (Sembawang Park, 0.4 lg l1 ). MPhT and DPhT were not detected in samples from all locations. Irgarol-1051 was detected in seawater from 13 (of 26) locations sampled (Fig. 2). The maximum concentration of Irgarol-1051 (4.0 lg l1 ) was obtained from seawater collected at Changi. Relatively high concentrations were also detected in the Straits of Johor (Sembawang Park, 3.8 lg l1 ; Punggol, 3.3 lg l1 ; Pasir Ris, 2.8 lg l1 ) and at East Coast Park in the Singapore Straits (3.6 lg l1 ). Irgarol-1051 was below the detection limit in all samples from offshore locations. ‘‘Total’’ antifouling compound concentrations (sum of concentrations of TBT and Irgarol-1051) were generally higher in the vicinity of sailing clubs (East Coast Park, 5.23 lg l1 ; Changi, 4.99 lg l1 ; Raffles Marina, 4.52 lg l1 ) as compared to samples obtained offshore (see Table 1). Organotin compounds were recorded from all 26 locations sampled from Singapore Straits and the Straits of Johor (Fig. 1). Relatively high levels of TBT were detected in the western Singapore Straits and the northeastern Straits of Johor (1.2–2.7 lg l1 ). Lower
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Fig. 2. Distribution of Irgarol-1051 and TPhT in Singapore coastal waters. MPhT and DPhT were not detected in all samples analysed. Samples were collected during October and November 2000 from 26 locations.
amounts of TBT ranging from 0.5 to 1.4 lg l1 were recorded offshore in the Singapore Straits as well as in the northwestern Straits of Johor. These findings are not surprising since shipbuilding industries are located at the southwest and northeast coasts of Singapore Island. Water samples taken near shipyards (Sembawang Park, Jurong Pier, i.e. location 1 and 20) contained moderately high levels of TBT (2.4 and 2.7 lg l1 , respectively in comparison with other international ports and marinas, e.g., Bahrain (Bahrain Marina, 8.35 lg l1 ; Hasan and Juma, 1992), USA (Baltimore Harbour, 4.57 lg l1 ; Matthias et al., 1986), London (Tichmarsh Marina, 3.94 lg l1 ; Dawson et al., 1992), Western Australia (Cockburn Sound, 1.35 lg l1 ; Kohn et al., 1999), Hong Kong (Sai Kung, 1.00 lg l1 ; Lau, 1991), Mexico (Ensenada, 0.47 lg l1 ; Macias-Carranza et al., 1997), France (C^ ote d’Azur) (Beaulieu Marina, 1.56 lg l1 ; Alzieu et al., 1991), Malaysia (Port Klang, 0.28 lg l1 ; Tong et al., 1996), New Zealand (Tutukaka Harbour, 0.32 lg l1 ; King et al., 1989), Japan (Osaka Bay, 0.06 lg l1 ; Harino et al., 1998), South Korea (Masan Bay, 0.06 lg l1 ; Gu et al., 1997) and Taiwan (Lukang, 0.80 lg l1 ; Liu et al., 1997). The widespread occurrence of organotin pollution has raised concerns over the accumulation of organotin compounds in the food chain and the associated risks related to the presence of contaminants (Belfroid et al., 2000). TBT has endocrine disrupting properties in marine gastropods at levels lower than 10 ng l1 (Fent, 1996). Concentrations of TBT in the Singapore coastal environment are between 10 and 100 times the threshold level required to induce imposition of male characteristics (imposex) in females (Smith and McVeagh, 1991; Byran et al., 1988) and shell thickening
in the oyster species Crassostrea gigas (Alzieu et al., 1991). The phenomenon of imposex has previously been reported to occur in Singapore waters (Tan, 1997, 1999), and the present study confirms the presence of organotin compounds in Singapore waters. In this short-term spot survey, the highest amount of TBT (3.20 lg l1 ) was detected at Cyrene Reef (location 17), which is located near several designated anchorages. The lowest amount of TBT (0.43 lg l1 ) was detected in seawater from Lim Chu Kang (location 25) in the eastern Straits of Johor where there is no major source of antifouling compounds. The small amount present here is probably derived from miscellaneous traffic of small vessels as well as its relative proximity to Tuas shipyard industries at the entrance of the eastern Johor Straits. DBT, a degradation product of TBT, was detected in 24 locations, with a maximum concentration of 3.85 lg l1 at World Trade Centre (location 12, Fig. 1). Except at locations 15 and 25, samples from the remaining 23 locations contained DBT in the range of 0.4 and 1.30 lg l1 . The ratios of TBT to DBT (between 0.4 and 1.3 in 18 locations out of 26 locations) in Singapore are in general comparable to those found in Mediterranean (Tolosa et al., 1996). However, the higher TBT:DBT ratios of between 2.1 and 5.9 at six locations (Kranji, Cyrene Reef, Labrador Park, Jurong Pier, Pasir Ris, Jurong Island; locations 26, 17, 13, 20, 3 and 19 respectively) may indicate higher input of TBT. At two other locations (Pulau Satumu and Lim Chu Kang; locations 15 and 25), DBT was below the detection limit. MBT was detected in samples from only eight locations (Sembawang Park, Punggol, Changi, World Trade
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Centre, Pulau Satumu, Tuas Jetty, Lim Chu Kang and Kranji; locations 1, 2, 4, 12, 15, 22, 25, 26) most of which were located in the vicinity of shipyards and marinas in addition to one offshore location (Pulau Satumu; location 15) which was found to have MBT concentrations of up to 1.06 lg l1 (see Fig. 1). TBT:MBT ratio was higher in two locations (Changi: 4.9 and Kranji: 3.8). This could reflect lower TBT degradation. TPhT was detected at only one site (location 1), and its degradation products MPhT and DPhT were not detected at all. This is somewhat surprising since preliminary (unpublished) results from seawater samples we collected in 1999 have indicated the presence of TPhT up to (1.22 lg l1 ) and its degradation products in Singapore coastal waters. The general scarcity of TPhT in this survey may reflect the increasingly restricted use of this compound in antifouling paint formulations (Apte and Gardner, 1988) and possibly high degradation rates in the tropics. Irgarol-1051 was detected at 13 out of 26 sampled locations. The concentrations of Irgarol-1051 were higher in samples obtained from the eastern Straits of Johor than the Singapore Straits (see Fig. 2), probably due to the presence of potential sources of antifouling leachates from Sembawang shipyard, Punggol Marina and Pasir Gudang, a Malaysian port located in the eastern Straits of Johor. Whilst this study reveals the presence of Irgarol-1051 in Singapore coastal waters for the first time, widespread contamination of Irgarol-1051 has been reported in several countries in Europe, e.g., in France (C^ ote d’Azur, 0.100–1.700 lg l1 ; Readman et al., 1993), United Kingdom (Hampshire, <0.002 to 0.50 lg l1 ; Gough et al., 1994), Sweden (Fieskebackski, 0.030–0.400 lg l1 ; Tolosa et al., 1996) and Switzerland (Port d’Ouchy (lake), 0.003–0.145 lg l1 ; Toth et al., 1996). Although the antifouling algicide Irgarol-1051 is highly toxic to non-target marine algae (Ciba Geigy, 1988; Dahl and Blanck, 1996) the ban on TBT is likely to result in a worldwide increase in the use of Irgarol1051 and similar chemicals as antifouling agents (Dahl and Blanck, 1996). Tolosa et al. (1996) reported that due to the legislation restricting the use of TBT at Beaulieu Marinas (Mediterranean coast), TBT contamination decreased markedly from 1.56 lg l1 in 1988 to 0.02 lg l1 in 1995, but at the same time Irgarol-1051 concentration increased from 0.012 to 0.400 lg l1 . The toxic effects of Irgarol-1051 on marine organisms other than marine algae have not been documented so far, but it is clear that environmental toxicology data are required to evaluate the impact of this compound in coastal waters. De Noyelles et al. (1982) showed that low levels of triazine compounds at concentrations in the range of 1 and 5 lg l1 inhibit photosynthesis in phytoplankton communities. The present study clearly shows that Singapore waters suffer from extensive TBT and Irgarol-1051 pollution. There is as yet no legislation
regulating the use of antifouling paints in Singapore, and their presence in Singapore waters represent an ecotoxicological risk that should be addressed.
Acknowledgements We thank Mr. Gerald Neo Wee Kok for his assistance during field sampling. This study was supported by the Tropical Marine Science Institute, National University of Singapore and the United Nations University, Japan under the Environmental Monitoring and Governance: EDCs in East Asian Coastal Hydrosphere programme.
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Baseline / Marine Pollution Bulletin 44 (2002) 697–703 Hasan, M.A., Juma, H.A., 1992. Assessment of TBT in the marine environment of Bahrain. Marine Pollution Bulletin 24, 408– 410. HMSO, 1994. Pesticides approved under the Control of Pesticides Regulations, 1986. Reference Book 500. HMSO, London. Julian, M.H., 1999. The roles and responsibilities of the International Maritime Organisation’s Marine Environment Protection Committee. In: 10th International Congress on Marine Corrosion and Fouling. Melbourne, Australia, 1999. King, N.G., Miller, M.C., de Mora, S.J., 1989. Tributyltin level for seawater, sediment and selected marine species in coastal Northland and Auckland. New Zealand Journal of Marine and Freshwater Research 23, 287–294. Kohn, A.J., Lalli, C.M., Wells, F.E., 1999. Imposex in Conus at Rottnest Island, Western Australia: five years after the first report. In: Walker, D.I., Wells, F.E. (Eds.), The Seagrass Flora and Fauna of Rottnest Island, Western Australia. Western Australian Museum, Perth, pp. 199–209. Lau, M.M.M., 1991. Tributyltin antifoulings: a threat to the Hong Kong marine environment. Archives of Environmental Contamination and Toxicology 20, 299–304. Liu, L.L., Chen, S.J., Peng, W.Y., Hung, J.J., 1997. Organotin concentrations in three intertidal neogastropod from the coastal waters of Taiwan. Environmental Pollution 98, 113–118. Macias-Carranza, V.A., Macias-Zamora, J.V., Villaescusa-Celaya, J.A., 1997. Organotin compound in marine water and sediments from the port of Ensenada, Baja California, Mexico. Ciencias Marinas 23, 377–394. Matthias, C.L., Bellama, J.M., Olson, G.J., Brinckman, F.E., 1986. Comprehensive method for the determination of aquatic butyl tin and butyl methyl tin species at ultra trace levels using simultaneous hybridation extraction with gas-chromatography flame photometric detection. Environmental Science and Technology 20, 609– 615. Mets, L., Thiel, A., 1989. Biochemistry and genetic control of the photosystem. II. Herbicide target site. In: Boeger, P., Sandmann,
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G. (Eds.), Target sites of Herbicide Action. CRC press, Florida, pp. 1–24. Morcillo, P., Porte, C., 1998. Monitoring of organotin compounds and their effects in marine molluscs. Trends in Analytical Chemistry 17, 109–116. Readman, J.W., Liong, W.K.L., Grondlin, D., Bartocci, J., Vielleneuve, J.P., Mee, L., 1993. Coastal water contamination from a triazine herbicide used in antifouling paints. Environmental Science and Technology 27, 1940–1942. Rouhi, A.M., 1998. The squeeze of tributyltin. Chemical Engineering News 27, 41–42. Smith, P.J., McVeagh, M., 1991. Widespread organotin pollution in New Zealand coastal waters as indicated by imposex in dogwhelks. Marine Pollution Bulletin 22, 409–413. Steen, R.J.C.A., Leonards, P.E.G., Brinkman, U.A.Th., Cofino, W.P., 1997. Ultra-trace-level determination of antifouling agent Irgarol1051 by gas chromatography with tandem mass spectrometric detection. Journal of Chromatography A 766, 153–158. Tan, K.S., 1997. Imposex in three species of Thais from Singapore, with additional observations on T. clavigera (K€ uster) from Japan. Marine Pollution Bulletin 34, 577–581. Tan, K.S., 1999. Imposex in Thais gradata and Chicoreus capucinus (Mollusca, Neogastropoda, Muricidae) from the Straits of Johor: a case study using penis length, area and weight as measures of imposex severity. Marine Pollution Bulletin 39, 295–303. Tolosa, I., Readman, J.W., Blaevoet, A., Ghilini, S., Bartocci, J., Horvat, M., 1996. Contamination of Mediterranean (C^ ote d’Azur) coastal water by organotins and Irgarol-1051 used in antifouling paints. Marine Pollution Bulletin 32, 335–341. Tong, S.L., Peng, F.Y., Phang, S.M., Lai, H.C., 1996. Tributyltin distribution in the coastal environment of peninsular Malaysia. Environmental Pollution 91, 209–216. Toth, S., Slooten, K.K., Spack, L., de Alencastro, L.F., Tarradellas, J., 1996. Irgarol-1051, an antifouling compound in freshwater, sediment, and biota of Lake Geneva. Bulletin of Environmental Contamination and Toxicology 57, 426–433.
0025-326X/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 5 - 3 2 6 X ( 0 1 ) 0 0 3 3 0 - 7
Baseline metal concentrations in sediments and fish, and the determination of bioindicators in the subtropical Chi-ku Lagoon, S.W. Taiwan Meng-Hsien Chen
*
Department of Marine Resources, National Sun Yat-sen University, Kaohsiung 80424, Taiwan, ROC
Since the early 1970s, Taiwan has experienced rapid economic growth and thriving industrial activities (including petroleum and plastics). As a result, many contaminants (including Hg and Cd) have been released into the environment, becoming bioavailable to local *
Tel.: +886-7-525-2000x5028; fax: +886-7-525-5020. E-mail address: [email protected] (M.-H. Chen).
seafood organisms and thereby threatening the health of consumers. Recently, barren wetlands of lesser agricultural value have gradually been industrialised throughout the island of Taiwan. One such example is the Chi-ku Lagoon area on the southwestern coast which has thus far remained relatively undeveloped. Its drainage basin has served as farmland since the 19th century, although some areas were converted into salt pan fields
Baseline
Edited by Bruce J. Richardson
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).
Organotin and Irgarol-1051 contamination in Singapore coastal waters C. Basheer a, K.S. Tan
b,*
, H.K. Lee
a
a
b
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore Tropical Marine Science Institute, National University of Singapore, 14 Kent Ridge Road, Singapore 119223, Singapore
Abstract The seas surrounding Singapore are principally utilized by the shipping industry but are now also increasingly used for a variety of other purposes, including desalination for supplies of drinking water and intensive aquaculture of food fish. While stringent environmental pollution standards are in place for industrial effluents, there is currently no legislative control over pollution from antifouling paints in Singapore. In this study, the concentrations of toxic antifouling agents tributyltin (TBT), triphenyltin (TPhT) and Irgarol-1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine) were determined from seawater obtained from 26 locations along and off the coast of Singapore in October and November 2000. These compounds were isolated by liquid–liquid extraction derivatized under controlled microwave heating and quantified by gas chromatography–mass spectrometry. TBT concentrations in seawater ranged between 0.43 and 3.20 lg l1 with a mean value of 1:40 0:60 lg l1 . The mean values of DBT and MBT were 1:07 0:80 lg l1 and 0:34 0:50 lg l1 respectively, while TPhT concentrations of up to 0.40 lg l1 were found. Monophenyltin and diphenyltin were not detected in all samples analysed. Irgarol-1051 was found to be present at concentrations of between 3.02 lg l1 and 4.20 lg l1 in seawater with a mean value of 2:00 1:20 lg l1 . Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Antifouling paints; Tributyltin; Irgarol-1051; Microwave-assisted derivatization
Antifouling compounds are incorporated into marine paints used to coat hulls of ships. This is done in order to prevent marine organisms from attaching onto the hull surfaces, thus enhancing fuel efficiency as well as increasing the service life of ships. Various antifouling strategies have been used to prevent such marine growth. The principal antifouling compound in use for the last four decades is tributyltin (TBT) (Bennett, 1996; Champ and Seligman, 1996). While organotin compounds are extremely toxic (Fent, 1996; Morcillo and *
Corresponding author. Fax: +65-77 49654. E-mail address: [email protected] (K.S. Tan).
Porte, 1998), usage of TBT-based antifouling paints is estimated to save the shipping industry some US$5.7 billion per annum (Rouhi, 1998). The annual fuel savings alone are estimated to be 7.2 million tons per year (Bennett, 1996). At the same time, however, organotin compounds are released into the marine environment, which can result in adverse effects on non-target organisms, even at extremely low concentration levels (Beaumont and Newman, 1986; Bryan et al., 1988). In response to increasing public concerns over their deleterious effects on the marine environment, the International Maritime Organisation has implemented a series of recommendations banning the use of TBT-based
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paints by 2003 (Julian, 1999). This has forced the antifouling industry to find alternatives to organotins. A common formulation now in use is to combine copper compounds with an algicide such as Irgarol-1051 (2methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine) (Steen et al., 1997) an s-triazine compound. There are currently over 80 products containing Irgarol-1051 registered for use as antifouling paints (HMSO, 1994). The level of TBT has declined in countries where regulations governing the use of organotin-based antifouling paints are in effect, but at the same time, environmental levels of other toxic antifouling compounds such as Irgarol-1051 have increased (Readman et al., 1993). A recent toxicological study of Irgarol-1051 showed that this compound is highly toxic to non-target marine algae and that it is sufficiently stable to reach toxic concentrations in the environment (Dahl and Blanck, 1996). The mode of action is based on the inhibition of photosynthetic electron transport in chloroplasts (Mets and Thiel, 1989). Irgarol-1051 inhibits photosynthesis at concentrations lower than 1 lg l1 (De Noyelles et al., 1982). It is feared that Irgarol-1051 might inhibit the growth of algae along shorelines, changing biological communities and altering the ecology of coastal areas. The waters surrounding Singapore not only serve as a waterway for vessels plying the Straits of Malacca, but function as one of the world’s busiest harbours, supporting substantial container-handling and oil-refining industries. Singapore has stringent environmental pollution controls over land-based sources, and industrial effluents are strictly monitored with heavy fines imposed on law breakers. However, the more insidious problems caused by antifouling compounds leaching into Singapore waters have not been addressed adequately. There is currently no legislation controlling the use and disposal of organotin-based antifouling compounds in Singapore. The Ministry of Environment to this date monitors neither TBT nor Irgarol. Plans for desalination of coastal waters to supply drinking water to the general public and high-density culture of food fish in Singapore waters within port limits are two future activities that demand monitoring of toxic organic pollution in the sea. This paper provides a first look at the antifouling agents TBT and Irgarol-1051 in Singapore waters. In order to analyse and quantify non-polar organotin and triazine compounds in environmental samples using gas chromatography, derivatization of these compounds is a critical step in sample preparation. Classical derivatization using Grignard reagent is a multi-step, time-consuming process, which is adversely affected by humidity. To overcome this problem, direct derivatization of analytes using sodium tetraethylborate (NaEt4 B) was used under microwave heating to obtain clear separation and complete derivatization of organotins and Irgarol-1051 in a single step. This method was employed to quantify organotin and Irgarol-1051 in coastal waters
around Singapore. It is envisaged that the rapid method will provide for a more efficient means to monitor the marine environment in Singapore. A CEM (Matthews, NC, USA) MARSx Sx -CEM Corporation (USA) microwave extraction system (maximum power: 1200 W) was used in this work. All quantitative analyses were carried out using a Shimadzu QP-5050 GC–MS system with an auto sampler (AOC20i). Ionisation was carried out by electron impact (EI). A DB-5 (30 m 0:32 mm i.d., 25-lm film thickness) general-purpose column obtained from J and W Scientific (Folsom, CA, USA) was used. The optimised temperature programme was as follows: initial temperature 50 °C (hold for 2 min), increased by 20 °C min1 to 140 °C and further increased to 220 °C at 7 °C min1 . The final temperature was 280 °C, achieved at a rate of 15.3 °C min1 . Injector and detector temperatures were set to 280 and 300 °C, respectively. Helium carrier gas was maintained at a flow rate of 1.5 ml min1 . EI ionisation energy level was set at 70 eV and the mass range between 40 and 400 m/z. All glassware was washed with detergent and tap water, soaked in 10% HNO3 for 12 h and subsequently rinsed with deionised water and acetone before use. Monobutyltin (MBT) trichloride (95%), dibutyltin (DBT) dichloride (98%), tributyltin (TBT) chloride (96%), monophenyltin (MPhT) trichoride (99%), diphenyltin (DPhT) dichloride (95%), triphenyltin (TPhT) chloride (99%), and tetrabutyltin (TeBT) (>97%) were purchased from Merck (Germany). Irgarol-1051 was obtained from Ciba Geigy (Switzerland). All other analytical-grade solvents and chemicals were purchased from Merck and Fluka (USA). Sodium tetraethylborate (NaEt4 B) was obtained from Strem chemicals (USA). A 2% (w/v) NaEt4 B solution was prepared daily using Milli-Q (deionised) water. Acetate buffer (pH 5) was prepared by dissolving 1 M sodium acetate in Milli-Q water and adjusted to pH 5.00 using concentrated acetic acid. Stock solutions of MBT, DBT, TBT, MPhT and DPhT were prepared (5 mg ml1 ) in hexane, whereas TPhT and Irgarol-1051 were prepared in ethyl acetate (5 mg ml1 ). Organotins were derivatized with NaEt4 B using acetate buffer (pH 5). The MARS microwave system was used at 60% power for 3 min. A seven-point calibration curve was plotted with a concentration range of 10–2000 ppb (R2 ¼ 0:99). Mixtures of working solutions were prepared daily in hexane from stock solutions. TeBT was used as an internal standard. Seawater samples were collected from 26 locations (see Table 1) along the Singapore coastline over a period of two months during October and November 2000. The salinity of seawater ranged between 28 and 35 ppt; the temperature and pH of the samples ranged from 28 to 32 °C and from 7.9 to 8.6, respectively. All samples were collected during the day, in 1-l HDPE Nalgeneâ bottles which were previously washed with dilute nitric acid and
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Table 1 List of sampling locations and their proximity to potential sources of antifouling contaminants Site no.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Locations
Sembawang Park Punggol Pasir Ris Changi Off Pulau Tekong East Coast Park Off East Coast Park Marina East Off Marina East St. John’s Island Sister’s Island World Trade Centre Labrador Park Pulau Jong Pulau Satumu Pulau Hantu Cyrene Reef West Coast Park Jurong Island Jurong Pier Sultan Shoal Tuas jetty Raffles Marina Sarimbun Lim Chu Kang Kranji
Coordinates Latitude
Longitude
1.28.200 1.25.030 1.23.400 1.22.040 1.22.050 1.18.420 1.17.150 1.17.500 1.16.180 1.13.120 1.12.950 1.15.860 1.17.030 1.12.550 1.09.600 1.14.440 1.15.190 1.17.750 1.15.510 1.18.580 1.14.430 1.17.460 1.20.070 1.26.030 1.27.350 1.25.920
103.49.480 103.54.080 103.57.030 104.05.500 104.02.540 103.56.200 103.54.100 103.52.030 103.52.170 103.51.030 105.50.070 103.49.350 103.46.970 103.47.260 103.44.840 103.38.920 103.45.100 103.43.930 103.42.230 103.42.690 103.38.920 103.37.340 103.39.300 103.41.020 103.41.660 103.44.600
N N N N N N N N N N N N N N N N N N N N N N N N N N
E E E E E E E E E E E E E E E E E E E E E E E E E E
Date of collection (dd mm yyyy)
Potential source of antifouling contaminant
TBT/DBT
TBT/ MBT
‘‘Total’’ antifouling compound concentration (TBT þ Irgarol, in lg l1 )
13.11.2000 03.11.2000 07.11.2000 06.11.2000 16.10.2000 16.10.2000 02.11.2000 09.10.2000 25.10.2000 07.11.2000 25.10.2000 04.10.2000 05.10.2000 05.10.2000 01.11.2000 25.10.2000 02.11.2000 10.10.2000 27.10.2000 13.11.2000 20.10.2000 09.10.2000 12.10.2000 27.10.2000 02.10.2000 02.10.2000
Sy, P P, J, M Sy M, J SL – – P P SL SL P P SL LH SL SL M, J P J, Sy SL, LH J, Sy M, J – J –
1.3 1.0 3.6 0.9 0.8 1.1 1.0 1.0 0.4 0.9 0.9 0.5 4.0 0.4 0.0 1.3 5.0 1.0 2.1 3.6 0.9 3.0 1.1 1.3 0.0 6.0
3.8 1.2 0.0 4.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.4 0.0 0.0 1.3 0.0 0.0 0.0 0.0 0.0 0.0 1.2 0.0 0.0 0.7 1.8
4.06 5.12 4.22 4.99 1.66 5.23 1.90 1.95 0.52 0.88 0.88 2.98 2.85 0.69 1.42 0.89 3.02 2.41 1.93 2.71 1.10 3.78 4.52 1.37 1.38 2.57
The contamination ratios of TBT/DBT and TB/MBT as well as the sum of TBT and Irgarol-1051 contaminations are also provided for each location. (J––Jetty; LH––Lighthouse; P––Port; M––Marina; SL––Shipping lane; Sy––Shipyard).
rinsed in deionised water. Offshore samples were collected from the side of a boat. In order to determine within-location variability, we also collected samples from within a 10-m distance range. Organotin and Irgarol-1051 concentrations in six samples collected from one locality were not significantly different and subsequent sampling was limited to one seawater sample per site. All samples were collected and analysed on the same day. Extraction was performed on unfiltered samples, as the amounts of suspended particles were found to be negligible in surface water. Organotins and Irgarol-1051 were spiked with laboratory seawater (Instant Oceanâ seasalt dissolved in deionised water) made up to a salinity of approximately 32 parts per thousand. Two hundred ml of seawater sample was used to perform extraction with spiked organotins and Irgarol-1051 with 20 ml of 3:2 ethyl acetate:hexane solvent mixture containing 2 ml of saturated NaCl. The pH of the sample was reduced to 2 by adding 6 N hydrochloric acid. Liquid–liquid extraction (LLE) was performed twice with the solvent–seawater mixture. The resulting organic layer was then subjected to derivatization under microwave (60% power, 3 min for 110 °C and held for 3 min) with 5 ml of freshly prepared NaEt4 B solution, 5 ml of pH 4 acetate buffer and 1 ml of
Table 2 Recovery test of ethylated organotins and Irgarol-1051 and their detection limits Analyte
Calibration R2 -value
Mean recovery (%)
RSD% ðn ¼ 3Þ
LOD (ng l1 )
Monobutyltin Dibutyltin Tributyltin Monophenyltin Diphenyltin Triphenyltin Irgarol-1051
0.998 0.998 0.998 0.998 0.995 0.998 0.993
73 92 91 87 70 94 88
5.54 5.58 3.65 4.72 8.85 4.20 6.30
6 5 6 5 12 4 10
R2 ––correlation coefficient; RSD––relative standard deviation; LOD–– limit of detection.
nonane. The addition of n-nonane minimized loss of analytes under microwave radiation at high temperature. After derivatization, the organic layer was separated and trace amounts of water were removed by adding anhydrous Na2 SO4 . Finally the extract was concentrated to 1 ml under a stream of nitrogen, made up with hexane to 1 ml and 1 ll was injected into the GC–MS. Recoveries of organotin and Irgarol-1051 are shown in Table 2. In the classical method of sample preparation using a Grignard reagent, derivatization is a
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Fig. 1. Distribution of MBT, DBT and TBT in Singapore coastal waters. Samples were collected from 26 locations along Singapore Straits and the Straits of Johor during October and November 2000. Geographical coordinates for the locations are given in Table 1.
multi-step process that is complex, tedious and time consuming. In addition, only 50–60% of compounds are typically derivatized with the classical method. Ethylation using NaEt4 B coupled with microwave heating is simpler and faster than the classical methods and clear baseline and separation were obtained in this way. A typical routine classical method would take up to 4 h for extraction and derivatization alone, as compared to the current method using combined LLE microwave, which required only half an hour for extraction and derivatization. TBT and its degradation products (either as DBT or MBT) were present in samples from all 26 sampling locations (Fig. 1). The highest amounts of TBT (3.20 lg l1 ), DBT (3.80 lg l1 ) and MBT (1.60 lg l1 ) were detected in samples from Singapore Straits. The mean values ðn ¼ 26Þ obtained for TBT, DBT and MBT were 1:44 0:60, 1:07 0:80 and 0:34 0:50 lg l1 , respectively. TBT concentrations ranged from 0.43 to 3.20 lg l1 (Fig. 1), with high concentrations occurring in samples obtained from Cyrene Reef, Pulau Jong and Jurong Pier in the vicinity of Jurong Island (locations 17, 19, 20; Fig. 1). Samples obtained from other locations (e.g., World Trade Centre and Labrador Park; locations 12, 13) in the Singapore Straits also contained TBT up to 1.90 lg l1 . Seawater from locations along the northeastern coast of Singapore (locations 2–7) contained between 1.40 and 2.40 lg l1 of TBT. In northwestern coastal areas, TBT concentrations between 0.69 and 3.2 lg l1 were found. DBT was detected in 24 locations (except Pulau Satumu and Lim Chu Kang) where concentrations ranged between 0.61 and 3.83 lg l1 . MBT was detected at only eight locations,
where concentrations ranged between 0.35 and 1.58 lg l1 (see Fig. 2). High ratios of TBT/DBT (Table 1) were found in the Singapore Straits (Cyrene Reef, 5.0; Jurong Pier, 3.6; and Tuas Jetty, 3.0), as were samples from the Straits of Johor (Kranji, 6.0; Pasir Ris, 3.5; Sarimbun, 1.3; and Sembawang Park, 1.2). The ratios of TBT/MBT (Table 1) from the Straits of Johor were also high (Changi, 4.9; Sembawang Park, 3.8; Kranji, 1.8). In contrast, samples from Singapore Straits had generally lower TBT/MBT ratios (World Trade Centre, 1.3; Pulau Satumu, 1.3; Tuas Jetty, 1.2). TPhT was surprisingly detected at only one location (Sembawang Park, 0.4 lg l1 ). MPhT and DPhT were not detected in samples from all locations. Irgarol-1051 was detected in seawater from 13 (of 26) locations sampled (Fig. 2). The maximum concentration of Irgarol-1051 (4.0 lg l1 ) was obtained from seawater collected at Changi. Relatively high concentrations were also detected in the Straits of Johor (Sembawang Park, 3.8 lg l1 ; Punggol, 3.3 lg l1 ; Pasir Ris, 2.8 lg l1 ) and at East Coast Park in the Singapore Straits (3.6 lg l1 ). Irgarol-1051 was below the detection limit in all samples from offshore locations. ‘‘Total’’ antifouling compound concentrations (sum of concentrations of TBT and Irgarol-1051) were generally higher in the vicinity of sailing clubs (East Coast Park, 5.23 lg l1 ; Changi, 4.99 lg l1 ; Raffles Marina, 4.52 lg l1 ) as compared to samples obtained offshore (see Table 1). Organotin compounds were recorded from all 26 locations sampled from Singapore Straits and the Straits of Johor (Fig. 1). Relatively high levels of TBT were detected in the western Singapore Straits and the northeastern Straits of Johor (1.2–2.7 lg l1 ). Lower
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Fig. 2. Distribution of Irgarol-1051 and TPhT in Singapore coastal waters. MPhT and DPhT were not detected in all samples analysed. Samples were collected during October and November 2000 from 26 locations.
amounts of TBT ranging from 0.5 to 1.4 lg l1 were recorded offshore in the Singapore Straits as well as in the northwestern Straits of Johor. These findings are not surprising since shipbuilding industries are located at the southwest and northeast coasts of Singapore Island. Water samples taken near shipyards (Sembawang Park, Jurong Pier, i.e. location 1 and 20) contained moderately high levels of TBT (2.4 and 2.7 lg l1 , respectively in comparison with other international ports and marinas, e.g., Bahrain (Bahrain Marina, 8.35 lg l1 ; Hasan and Juma, 1992), USA (Baltimore Harbour, 4.57 lg l1 ; Matthias et al., 1986), London (Tichmarsh Marina, 3.94 lg l1 ; Dawson et al., 1992), Western Australia (Cockburn Sound, 1.35 lg l1 ; Kohn et al., 1999), Hong Kong (Sai Kung, 1.00 lg l1 ; Lau, 1991), Mexico (Ensenada, 0.47 lg l1 ; Macias-Carranza et al., 1997), France (C^ ote d’Azur) (Beaulieu Marina, 1.56 lg l1 ; Alzieu et al., 1991), Malaysia (Port Klang, 0.28 lg l1 ; Tong et al., 1996), New Zealand (Tutukaka Harbour, 0.32 lg l1 ; King et al., 1989), Japan (Osaka Bay, 0.06 lg l1 ; Harino et al., 1998), South Korea (Masan Bay, 0.06 lg l1 ; Gu et al., 1997) and Taiwan (Lukang, 0.80 lg l1 ; Liu et al., 1997). The widespread occurrence of organotin pollution has raised concerns over the accumulation of organotin compounds in the food chain and the associated risks related to the presence of contaminants (Belfroid et al., 2000). TBT has endocrine disrupting properties in marine gastropods at levels lower than 10 ng l1 (Fent, 1996). Concentrations of TBT in the Singapore coastal environment are between 10 and 100 times the threshold level required to induce imposition of male characteristics (imposex) in females (Smith and McVeagh, 1991; Byran et al., 1988) and shell thickening
in the oyster species Crassostrea gigas (Alzieu et al., 1991). The phenomenon of imposex has previously been reported to occur in Singapore waters (Tan, 1997, 1999), and the present study confirms the presence of organotin compounds in Singapore waters. In this short-term spot survey, the highest amount of TBT (3.20 lg l1 ) was detected at Cyrene Reef (location 17), which is located near several designated anchorages. The lowest amount of TBT (0.43 lg l1 ) was detected in seawater from Lim Chu Kang (location 25) in the eastern Straits of Johor where there is no major source of antifouling compounds. The small amount present here is probably derived from miscellaneous traffic of small vessels as well as its relative proximity to Tuas shipyard industries at the entrance of the eastern Johor Straits. DBT, a degradation product of TBT, was detected in 24 locations, with a maximum concentration of 3.85 lg l1 at World Trade Centre (location 12, Fig. 1). Except at locations 15 and 25, samples from the remaining 23 locations contained DBT in the range of 0.4 and 1.30 lg l1 . The ratios of TBT to DBT (between 0.4 and 1.3 in 18 locations out of 26 locations) in Singapore are in general comparable to those found in Mediterranean (Tolosa et al., 1996). However, the higher TBT:DBT ratios of between 2.1 and 5.9 at six locations (Kranji, Cyrene Reef, Labrador Park, Jurong Pier, Pasir Ris, Jurong Island; locations 26, 17, 13, 20, 3 and 19 respectively) may indicate higher input of TBT. At two other locations (Pulau Satumu and Lim Chu Kang; locations 15 and 25), DBT was below the detection limit. MBT was detected in samples from only eight locations (Sembawang Park, Punggol, Changi, World Trade
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Centre, Pulau Satumu, Tuas Jetty, Lim Chu Kang and Kranji; locations 1, 2, 4, 12, 15, 22, 25, 26) most of which were located in the vicinity of shipyards and marinas in addition to one offshore location (Pulau Satumu; location 15) which was found to have MBT concentrations of up to 1.06 lg l1 (see Fig. 1). TBT:MBT ratio was higher in two locations (Changi: 4.9 and Kranji: 3.8). This could reflect lower TBT degradation. TPhT was detected at only one site (location 1), and its degradation products MPhT and DPhT were not detected at all. This is somewhat surprising since preliminary (unpublished) results from seawater samples we collected in 1999 have indicated the presence of TPhT up to (1.22 lg l1 ) and its degradation products in Singapore coastal waters. The general scarcity of TPhT in this survey may reflect the increasingly restricted use of this compound in antifouling paint formulations (Apte and Gardner, 1988) and possibly high degradation rates in the tropics. Irgarol-1051 was detected at 13 out of 26 sampled locations. The concentrations of Irgarol-1051 were higher in samples obtained from the eastern Straits of Johor than the Singapore Straits (see Fig. 2), probably due to the presence of potential sources of antifouling leachates from Sembawang shipyard, Punggol Marina and Pasir Gudang, a Malaysian port located in the eastern Straits of Johor. Whilst this study reveals the presence of Irgarol-1051 in Singapore coastal waters for the first time, widespread contamination of Irgarol-1051 has been reported in several countries in Europe, e.g., in France (C^ ote d’Azur, 0.100–1.700 lg l1 ; Readman et al., 1993), United Kingdom (Hampshire, <0.002 to 0.50 lg l1 ; Gough et al., 1994), Sweden (Fieskebackski, 0.030–0.400 lg l1 ; Tolosa et al., 1996) and Switzerland (Port d’Ouchy (lake), 0.003–0.145 lg l1 ; Toth et al., 1996). Although the antifouling algicide Irgarol-1051 is highly toxic to non-target marine algae (Ciba Geigy, 1988; Dahl and Blanck, 1996) the ban on TBT is likely to result in a worldwide increase in the use of Irgarol1051 and similar chemicals as antifouling agents (Dahl and Blanck, 1996). Tolosa et al. (1996) reported that due to the legislation restricting the use of TBT at Beaulieu Marinas (Mediterranean coast), TBT contamination decreased markedly from 1.56 lg l1 in 1988 to 0.02 lg l1 in 1995, but at the same time Irgarol-1051 concentration increased from 0.012 to 0.400 lg l1 . The toxic effects of Irgarol-1051 on marine organisms other than marine algae have not been documented so far, but it is clear that environmental toxicology data are required to evaluate the impact of this compound in coastal waters. De Noyelles et al. (1982) showed that low levels of triazine compounds at concentrations in the range of 1 and 5 lg l1 inhibit photosynthesis in phytoplankton communities. The present study clearly shows that Singapore waters suffer from extensive TBT and Irgarol-1051 pollution. There is as yet no legislation
regulating the use of antifouling paints in Singapore, and their presence in Singapore waters represent an ecotoxicological risk that should be addressed.
Acknowledgements We thank Mr. Gerald Neo Wee Kok for his assistance during field sampling. This study was supported by the Tropical Marine Science Institute, National University of Singapore and the United Nations University, Japan under the Environmental Monitoring and Governance: EDCs in East Asian Coastal Hydrosphere programme.
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Baseline metal concentrations in sediments and fish, and the determination of bioindicators in the subtropical Chi-ku Lagoon, S.W. Taiwan Meng-Hsien Chen
*
Department of Marine Resources, National Sun Yat-sen University, Kaohsiung 80424, Taiwan, ROC
Since the early 1970s, Taiwan has experienced rapid economic growth and thriving industrial activities (including petroleum and plastics). As a result, many contaminants (including Hg and Cd) have been released into the environment, becoming bioavailable to local *
Tel.: +886-7-525-2000x5028; fax: +886-7-525-5020. E-mail address: [email protected] (M.-H. Chen).
seafood organisms and thereby threatening the health of consumers. Recently, barren wetlands of lesser agricultural value have gradually been industrialised throughout the island of Taiwan. One such example is the Chi-ku Lagoon area on the southwestern coast which has thus far remained relatively undeveloped. Its drainage basin has served as farmland since the 19th century, although some areas were converted into salt pan fields