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Speciation of organotin in environmental sediment samples
Talanta 46 (1998) 395 – 405
Speciation of organotin in environmental sediment samples M. Ceulemans, S. Slaets, F. Adams * Department of Chemistry, Uni6ersity of Antwerpen (UIA) B-2610 Wilrijk, Belgium Received 25 May 1997; accepted 14 October 1997
Abstract An optimized sample preparation procedure for organotin speciation in sediment samples has been applied to the analysis of sediments collected in the environment. The method is based on tropolone complexation of the ionic organotins, followed by extraction into a hexane – ethylacetate mixture and derivatization by NaBEt4. The method was applied to the determination of organotin in various harbour, shipyard and dry-dock sediments in Belgium. Butyltin compounds were detected in all samples analyzed, often at high mg kg − 1 levels. A limited number of samples showed the presence of phenyltin compounds. Further, the method was adapted to the analysis of river sediments sampled from the vicinity of shipyards. Butyltin concentrations were detected at the mg kg − 1 level in the majority of samples. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Speciation; Organotin; Gas chromatography; Atomic emission spectrometry
1. Introduction The input levels of organotin compounds in the environment have been considerably restricted in the recent past in most countries due to legislation. Tributyltin (TBT), and to a lesser extent triphenyltin (TPT) used as biocides in anti-fouling paints, nevertheless remain common pollutants of the marine environment, particularly in the sediment matrix. It appears that tri-organotins and the products of their degradation accumulate in the sediment. Attention given to sediment analysis is increasing, considering that the sediment is recognized as the ultimate ‘sink’ for organotin compounds which are released into the aquatic * Corresponding author. Fax: +32 3 8202376.
environment and may create an eco-toxicological risk long after anthropogenic sources are banned from a given area. Therefore, the short residence time of TBT in the water column alone is not an adequate criterion for evaluating its potential environmental hazards. Hence, it is essential that reliable analytical methods are developed for the determination of butyl- and phenyltin compounds in sediments. In natural waters, TBT has a short residence time, with a half-life in the range of several days to weeks [1,2]. Adsorption of TBT onto suspended particulate matter is thought to be an important removal process. Randall and Weber reported that between 57 and 95% of TBT in the water column is sorbed under simulated estuarine conditions [3]. In this way a significant proportion
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of TBT appears to be deposited, and concentration factors of 103 relative to the overlying waters are common [4 – 6]. Slow degradation of TBT in sediments would increase its persistence in the aquatic environment. Studies of TBT degradation in sediment/water mixtures under experimental conditions have been carried out by Maguire et al. [7] and Stang et al. [8] and suggested that TBT has a half-life in sediments of several months. An alternative approach consists in obtaining profiles of TBT concentrations within sediment cores [9], which yields a longer half-life of 1.85 years. Similarly, Quevauviller et al. [10] in a study of sediment cores of Arcachon Bay, France, reported that TBT concentration remains high long after regulation was implemented, hence that this compound is not rapidly degraded in sediment as was previously assumed. Further, TBT has been found to accumulate to concentrations which can probably inhibit biological degradation. The same is valid for TPT compounds which have been shown to have low mobility, low aqueous solubility, and strong binding to soil and sediments in the aquatic environment [11]. Sample preparation procedures for organotin speciation analysis in sediments are generally more complicated than those for water samples. Since organotin compounds are not involved in mineralogical processes and bind onto the surface of the sediment the complete dissolution of the sediment matrix prior to the analysis is not considered necessary. The basic approach to release organotin compounds from the sediment involves, e.g. acid leaching in aqueous or methanolic medium by sonification, stirring or Soxhlet extraction with an organic solvent. Generally, sample preparation procedures for the separation of organotin compounds from sediments are time consuming (several hours). A recent alternative is the use of a low power microwave field which was shown to accelerate the leaching of the organotin species from the sediments considerably and to reduce actual leaching times to a few minutes [12,13]. Data of organotin contents detected in sediments originating from the environment in Belgium are scarce. The only study on TBT contamination, to our knowledge, was carried out
in the frame of a quality survey of dredging sludge originating from some important marine yacht- and fishing harbours [14]. The highest TBT concentrations were found in the harbour of Zeebrugge, as can be seen from Table 1. Further, it was found that locations displaying a high TBT content were also characterized by a strong organic pollution, mainly polycyclic aromatic hydrocarbons. Since TPT compounds strongly adsorb to suspended matter and sediments, they are readily detected in this matrix. During a Belgian survey on the presence of various pesticides in the environment, phenyltin compounds were found in 15% of the sediment samples, with contents ranging from 120 to 190 mg kg − 1. The highest concentrations were found in the mouth of the Yser river, in the Gaverbeek, a small tributary of the river Scheldt at Harelbeke and in the river Scheldt itself at Doel [15]. This paper presents the application of a sample preparation procedure based on tropolone complexation, liquid–liquid extraction and NaBEt4 derivatization in a monitoring study to assess the organotin pollution in a number of environmental sediments originating from various waterways in Belgium. The aim was to investigate the impact of dry-docking operations on the contamination of both surficial sediments from shipyard terrains and in river sediments originating from the vicinity of shipyards with regard to their organotin content.
2. Experimental
2.1. Apparatus GC–AES. Organotin species were separated on an HP-1 capillary column using a Model 5890 Table 1 TBT concentrations detected in marine Belgian harbours [14] Location
TBT concentration (mg kg−1)
Zeebrugge Nieuwpoort Oostende Blankenberge
8 – 895 15 29 41
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Series II gas chromatograph and detected by means of an HP Model 5921 A atomic emission detector (Hewlett – Packard, Avondale, PA). The GC was equipped with a KAS 503 (Gerstel, Mulheim, Germany) programmable temperature vaporization (PTV) injector. GC–AAS. A Varian Model 3700 gas chromatograph (Varian, Sunnyvale, CA) fitted with a RSL-150 (RSL, Eke, Belgium) megabore column, or an HP Model 5890 Series II gas chromatograph fitted with an HP-1 capillary column were used to separate the analytes prior to the detection by quartz furnace atomic absorption spectrometry (QFAAS); PE Model 2380 (Perkin Elmer, Norwalk, USA). For megabore column GC, samples were introduced on-column through a septum in a wide bore hot on-column liner. Injections on the capillary column were done using PTV as described earlier [16]. Injector, gas chromatograph, interface and detector operating conditions have been described in detail earlier for GC – AAS [17] and GC–AES [18].
2.2. Reagents Analytical reagent grade chemicals obtained from Merck (Darmstadt, Germany) were used unless otherwise stated. Deionized water, further purified in a Milli-Q system (Millipore, El Paso, TX) system was used throughout. Pentylmagnesiumbromide (2 mol l − 1 in diethylether) was obtained from Aldrich (Milwaukee, WI). Sodium tetraethylborate was obtained from Strem Chemicals (Bischheim, France). A 0.3% (w/v) aqueous solution was prepared daily. Diethyldithiocarbamic acid was prepared by dissolving 2.25 g of sodium diethyldithiocarbamate (NaDDTC) salt in water. The solution of DDTC in pentane was obtained by shaking the aqueous solution with 20 ml of 0.5 mol l − 1 of H2SO4 and extracting with 10 ml of pentane for 5 min. Acetate buffer (pH 5; 0.1 mol l − 1) was prepared by dissolving 13.6 g of sodium acetate trihydrate in 1 l of water, followed by pH adjustment with concentrated acetic acid. A 0.05% tropolone solution was prepared by dissolving the appropriate amount in hexane/ethylac-
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etate (1/1). The sources, purity and synthesis of organotin standards have been described earlier [19].
2.3. Procedure Circa 1 g of sediment was accurately weighed and placed in a centrifugation vessel with glass stopper together with 2 ml of hydrochloric acid (32%) and 8 ml of water; 25 ml of the hexane/ ethylacetate mixture (1/1), containing 0.05% tropolone were added and the mixture was sonicated for 1 h, followed by centrifugation at 3000 rpm for 5 min. The organic phase was transferred into an extraction vessel and evaporated to dryness using rotary evaporation. Then, 0.5 ml of hexane, containing Pe3SnEt as an internal standard, were added and the complexes were derivatized by addition of 1 ml of the NaBEt4 solution together with 50 ml of acetate buffer solution. The mixture was shaken manually for 5 min and after phase separation the hexane phase was sampled for clean up/analysis. A detailed description and discussion of extract clean-up has been presented previously [20]. A Pasteur pipette was filled with basic alumina to form a plug of 5 cm. The sediment extract was introduced onto the clean-up column. After elution of the original extract volume, an additional volume of 1 ml diethylether was brought onto the clean-up column. The diethylether was evaporated from the combined eluate using a gentle stream of nitrogen.
2.4. Sampling Sampling of superficial sediments was done using a Peelman drill, or by simple collection by means of a spade. Water-underlying sediments were collected using a Van Veen grab. After removal of stones, leaves and pieces of wood, the sediment was grounded with an agate mortar and pestle. Sediments were either oven-dried at 50°C or freeze-dried and stored at −20°C until analysis, i.e. in agreement with recommendations on sampling and storage procedures for organotin analysis in the marine environment [21,22].
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Table 2 Results for the analysis of shipyard and dry-dock sediments Sample
TBT
DBT
MBT
TPT
DPT
MPT
1.26 9 0.15 0.38 90.07 —a 5.55 9 0.72
0.65 90.08 0.27 9 0.05 — 1.55 922
1.32 90.18 0.40 9 0.06 — 6.48 9 0.91
Concentration 995% confidence interval (mg g−1) 1 3 5 6
35.89 2.9 6.82 9 0.42 26.4 91.8 141 910
13.6 9 1.0 3.03 9 0.16 10.0 90.6 103 9 6
6.23 90.50 1.00 90.09 26.4 9 1.8 46.2 93.4
Concentration9 95% confidence interval (ng g−1) 2 4
3909 35 20.3 9 2.2
173 915 11.69 1.0
199 918 11.3 91.4
— —
— —
— —
Mean results for three replicate analyses of each sediment. Concentration below detection limit (B1 ng g−1).
a
2.5. Certified reference materials
3. Results
To evaluate the performance of the plethora of existing sample preparation procedures and instrumental setups used among different laboratories, certified reference materials (CRM’s) were prepared by different organizations for the quality control of analytical results. Analysis results of CRM’s presented in some reports show that the reliability of sample preparation is often not sufficient and that several limitations still remain. Especially the accurate determination of monobutyltin (MBT) remains doubtful since, according to some reports on certification experiments [23– 25], no reliable method for the determination of this compound has been reported up to now. This is apparent from Table 2. Analysis of CRM’s proved that the method presented is able to accurately determine TBT and dibutyltin (DBT) in sediments, while MBT determination in general still remains doubtful due to the absence of reliable, or no or only indicative values for this compound in reference materials. However, the method was shown to be suitable for MBT determination in certain sediments [16]. An attempt to apply the developed procedure to the analysis of phenyltin compounds led to the conclusion that the determination of these species is most favorable in the absence of any tropolone complexing agent and using acetic acid for leaching.
3.1. Determination of organotin in harbour and dry-dock sediments 3.1.1. Shipyard located in the Antwerp harbour Huge point sources such as dry-dock facilities are responsible for the release of the largest fraction of TBT into the aquatic environment. An investigation was carried out to assess the contamination of a shipyard terrain after years of intense dry-docking activities. Further, the influence of these activities on the contamination of the harbour sediment was also investigated. Fig. 1 shows the location of the sampling sites with the sampling points indicated. A total of five surface samples was taken from the shipyard terrain, three at places where grit blasting activities had taken place, and two samples from other locations at the yard, this in order to assess the background concentration found at the terrain. The investigated ship repair yard was located in the Antwerp harbour, which itself is characterized by intense shipping in an almost enclosed environment with a low flushing rate. In a previous study on the determination of organotins in waters of the Antwerp harbour, which was carried out over a 4-month period between May and August 1991, two sampling locations (W1, W2) were situated in the vicinity of the shipyard investigated in the present study [26].
M. Ceulemans et al. / Talanta 46 (1998) 395–405
Fig. 1. Sampling locations.
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M. Ceulemans et al. / Talanta 46 (1998) 395–405
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This previous study indicated an overall TBT contamination level in the harbour in the range of 10–45 ng l − 1. The concentrations detected at locations W1 and W2 were significantly higher with concentrations ranging between 50 and 440 ng l − 1 over the 4-month study period for these two locations. These elevated concentrations found in the water column at these two locations were found due to the discharge of hazardous amounts of TBT in hosing-down water which originates from the washing of ships’ hulls, with a high-pressure hosing system before repainting activities. The contaminated water first remains for several days in a sinking-basin and is afterwards released into the poorly flushed harbour dock area. This study already showed the impact of dry-dock activities on the contamination levels in waters of the Antwerp harbour. In the present study, the impact of dry-docking operations on the contamination of the yard terrain, and harbour sediment was evaluated. The results of the analyses are presented in Table 3. From the results it can be seen that sediments 1, 3 and 6, sampled at locations where grit blasting takes place, generally display very high TBT concentrations at the mg kg − 1 level. Comparison with the Environmental Quality Target (EQT) value for TBT in sediments, set at 1 – 2 mg kg − 1 and implemented now in most European countries indicates severe contamination of these surface sediments [27]. Especially the concentration found in sediment 6 (141 mg kg − 1), originating from another smaller dry-dock located in the Antwerp harbour, is at extremely high level. Also Table 3 Results for the analysis of dredging sludge samples originating from the Ostend harbour Sample
1 2 3 4
Concentration 9 95% confidence interval (mg g−1) TBT
DBT
MBT
1112 9 120 169 9 14 394 9 31 450 9 32
2329 24 63.9 9 6.0 1819 13 217 9 14
80.5 98.1 29.292.3 10698 123 99
Mean results of three replicate analyses for each sediment.
DBT and MBT, the intermediate products of TBT degradation to inorganic tin, were found in all the samples. Further, phenyltin compounds were as well detected in these samples, however at much lower concentrations. The presented concentration figures for monophenyltin (MPT) should be considered as indicative values, as extraction and derivatization for this compound was found to be irreproducible as shown earlier [28]. Triphenyltin compounds (mainly TPT fluoride and small amounts of TPT chloride) are used in anti-fouling paints, however to a much lesser extent compared to TBT compounds. About 80% of all anti-fouling paints used contain TBT oxide or TBT metacrylate/methylmetacrylate copolymer, 12% are TBTF based and 8% are TBTF based [29,30]. Since TPT compounds are only used in free-association paints, and since there seems to be a general agreement to discontinue the use of this type of paint it is expected that discharges of TPT compounds from anti-fouling paints will decrease in the near future. The detected contents in samples 2 and 4 taken at places on the yard where no dry-docking operations such as grit blasting, washing, painting, etc. take place display much lower contents at mg kg − 1 level. However, the fact that butyltin compounds are detected at these locations may be attributed to an overall contamination of the yard terrain. Sediment 5, collected in the harbour, displays very high TBT concentrations, most probably originating from the hosing-down of TBT waste water in the harbour water and accumulation in the underlying sediments which act as a ‘sink’ for TBT. A chromatogram for this sediment after sample preparation and GC–AAS measurement is shown in Fig. 2. The results of this study indicate the need for strict dockyard management to minimize waste generation from dry-docking activities and treatment of contaminated waste waters. Potential waste minimization methods for marine maintenance and repair operations include the minimization of fugitive oversprays of paint (e.g. by changing application methods), the minimization of abrasive blast wastes and of chemical stripping wastes. Apart from high pressure hydro-washing abrasive blasting is often used to remove paint
M. Ceulemans et al. / Talanta 46 (1998) 395–405
Fig. 2. Chromatogram for a sample of Antwerp harbour sediment: (1) MBT; (2) DBT; (3) TBT; (is) internal standard (Pe3SnEt).
layers. The most commonly used blasting media are sand or grit together with a large volume of water. The presence of paint chips containing hazardous metallic and/or organometallic biocides makes abrasive blasting wastes potentially hazardous. Blast waste water generally constitutes the largest single waste stream for many yards. For instance, wet abrasive blasting of an average sized naval vessel can generate up to 180 tons of wet abrasive and ca. 2 000 000 l of contaminated water [31]. At the moment research and testing is underway on a number of innovative alternatives to both grit blasting and chemical stripping [32]. Segregation and recycling of blast media is possible because of the difference in density between the grit materials and the waste paint chips. Therefore, in many cases the contaminated grit can be reused several times before becoming too contaminated and requiring off-site disposal. An
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approach to prevent fugitive dust emissions would be to enclose the area with plastic sheeting or screening, this confining the waste to the immediate vicinity of the blasting. After blasting has been completed, the waste should be collected and transported to a licensed landfill. Chemical stripping wastes primarly consist of the stripping agent, of which methylenechloride is the most commonly used, and paint sludges. Waste minimization would include the use of less toxic stripping agents such as inorganic strippers consisting of aqueous solutions of caustic soda, and the reuse and recycling of contaminated strippers. Waste water should be treated in such a way that its TBT contents reduced to a level acceptable for discharge to river or estuarine waters. Equipment for this purpose is commercially available and generally uses a 4-stage process, two concerned with solids (principally paint solids) reduction and two concerned with removing TBT from the water. Briefly, the different stages are as follows: (1) flocculation and settling in which the pH of the raw wash water is adjusted to effect flocculation and agglomeration of the solids present; (2) filtration where the supernatant water from the settling stage is pumped to a 2-stage filtration system, and particles are removed to the sub-micron diameter range to ensure that paint particles which could still release TBT to the surrounding water are not present in the subsequent treatment steps; (3) carbon adsorption where the first stage of dissolved TBT removal is effected by adsorption onto activated carbon; (4) after passing through the carbon bed, the process water passes through a filter, to remove residual carbon particles and then to a device whereby it is irradiated with short-wave UV light. The concentrations of TBT can be effectively reduced to concentrations less than 0.2 mg l − 1 by oxidation reactions induced by the UV light, producing harmless tin oxide. The UV light irradiation step is the final stage in this type of waste water treatment plant. However, the majority of commercial shipyards discharge their effluents directly to the aquatic environment at no direct costs. Any treatment system thus becomes an additional cost burden to their operations. This cost burden will only be acceptable commercially if all yards (in-
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side and outside EU) are required to undertake environmental protection measures simultaneously. It is estimated that through the use of waste water treatment plants a reduction of emissions up to 85% could be accomplished.
height of the TBT concentration detected, plus the pattern of the concentrations of the degradation products DBT and MBT, which were found in much lower concentrations, indicate recent dis-
3.1.2. Dredging sludge from the Ostend harbour Dredging sludge samples were originating from various locations in the Ostend harbour where dredging activities had taken place. The harbour is characterized by intense shipping activities from pleasure crafts and ferry ships. Samples were analyzed in order to assess the organotin levels present in the Ostend harbour. Further, analyses of these samples would give an idea about the organotin contamination which may be introduced into non-contaminated areas, through dumping of these dredging sludges. The results of the analyses are presented in Table 4. All samples showed the presence of butyltin compounds at concentrations up to mg kg − 1 level, indicating contamination of the Ostend harbour due to shipping activities. Further, results suggest that dredging sludges originating from harbours and marinas should be collected and treated with care in order to avoid contamination of other areas through dumping of this sludge. Contaminated soils must be removed and either incinerated in special plants or be deposited at special waste disposal sites according to local or government regulations. Generally, it was found that dredging activities reduce TBT concentrations in harbours and marinas [33]. Dredging removes TBT-contaminated sediments, and because of the sediment-water partitioning, finally results in lower TBT concentrations in the water phase.
Table 4 Results for the analysis of river sediments originating from the vicinity of shipyards
3.1.3. Shipyard for pleasure crafts A surface sediment was taken from a small shipyard located at the Zuidwillemsvaart (Bocholt, Limburg). The yard is mainly used for the maintenance of small vessels and pleasure crafts. Amounts detected were 6.6090.08 mg kg − 1 for TBT, 1.67 90.20 mg kg − 1 for DBT and 1.15 9 0.05 mg kg − 1 for MBT. A chromatogram for this sediment, after sample preparation and GC– QFAAS measurement is shown in Fig. 3. The
Shipyard
Concentration 995% confience interval (mg kg−1) TBT
DBT
MBT
Rupelmonde
17.3 9 2.8 30.5 92.8 65.8 911.8 76.8 94.5 73.3 95.8 21.2 91.3 63.5 95.5 2.37 91.12a
30.5 9 3.3 61.5 95.8 97.8 915.3 221 9 11 169 931 41.5 94.3 117 96 2.78 9 0.80
19.4 91.6 34.3 91.8 47.8 9 10.5 130 99 77.0 915.3 19.2 9 3.1 69.394.3 0.83 9 0.13
Nieuwe
54.0 9 6.0
106 9 8
49.39 5.3
Scheldewerven
55.3 98.5 227 9 24 89.0 96.0 85.0 94.3 88.3 9 3.5 95.0 911.3 BDLa
98.3 98.8 196 9 12 155 911 144 99 181 9 15 168 99 5.38 9 1.20
52.3 99.8 111 96 70.8 9 5.5 70.3 9 5.5 72.0 9 6.8 78.094.5 2.69 9 0.58
Boelwerf
133 917 316 930 82.0 910.4 43.7 9 6.1 BDLa 4.49 90.63a
166 911 286 931 90.6 910.8 96.6 9 11.0 3.49 9 1.2 4.10 9 0.82
60.0 94.2 108 910 32.3 9 2.3 34.9 9 4.2 9.65 9 2.6 7.75 9 1.55
Fulton Marine
50.3 94.8 271 978 51.2 95.6 68.2 96.2 4.44 91.00 134 99 9.11 91.40 7.71 91.1
140 914 1499 9173 194 918 260 916 47.3 9 5.2 119 99 43.5 9 4.1 58.7 95.2
82.0 9 10.5 717 9144 81.0 910.0 150 9 15 20.4 9 2.7 47.3 9 4.4 19.9 9 2.5 26.4 9 2.6
Langerbrugge
105 96 34.6 93.8 88.5 910.1 2.91 9 0.72a BDLa
42.4 92.6 31.1 9 2.2 22.1 93.5 BDL BDL
15.4 91.1 19.3 92.5 9.50 91.9 BDL BDL
BDL, below detection limit (B1 mg kg−1). Mean results of three replicate analyses for each sediment. a Sediments taken at larger distances from the yard.
M. Ceulemans et al. / Talanta 46 (1998) 395–405
Fig. 3. Chromatogram for a sample of Bocholt shipyard sediment: (1) MBT; (2) DBT; (3) TBT; (is) internal standard (Pe3SnEt).
charges of TBT, suggesting the illegal usage of TBT-containing anti-fouling paints, since following current legislation the use of these paints is forbidden on ships smaller than 25 m.
3.1.4. Determination of organotin in ri6er sediments Analyses of sediment samples originating from shipyards and dry-dock terrains revealed the presence of very high concentrations of various organotin compounds. In cooperation with the Flemish Environmental Agency (VMM) a sampling campaign was carried out (Summer ‘95) in which river sediments were taken from the vicinity of shipyards. The aim of the study was to investigate whether the pollution is restricted to the yard and dock terrains itself or also has a wider effect on the contamination of the adjacent rivers. A total of 35 river sediments, originating from the vicinity of five different yards located in Flanders were analyzed. For a given shipyard sampling was carried at different locations in the river. Further, for each shipyard sediments were also taken at larger distances from the yard, up- and down-stream on the river, in order to assess the polluting impact of shipyard activities over longer distances.
403
The results of all 35 sediments are presented in Table 4. Generally, butyltin compounds were detected in all river sediments which were sampled in the vicinity of the shipyards. Phenyltin compounds were not detected in any of the samples. The detected levels are, in comparison with contents detected on the yard terrain itself, generally much lower, however in the majority of the samples analyzed they are a multiple of the EQT value for TBT in sediments, set at 1–2 mg kg − 1. Concentrations detected in river sediments sampled at larger distances, generally display contents below detection limits or at the low mg kg − 1 levels indicating the local impact of dry-dock operations on the contamination of adjacent rivers. A chromatogram for a sample of river sediment is shown in Fig. 4. TBT concentrations detected in the river sediments originating from the vicinity of the Rupelmonde shipyard range between 17–77 mg kg − 1 representing an overall contamination level in the seven sediments sampled in the vicinity of the
Fig. 4. Chromatogram for a sample of river sediment: (1) MBT; (2) DBT; (3) TBT; (is) internal standard (Pe3SnEt).
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yard. TBT contents detected in the river Scheldt in the vicinity of the Nieuwe Scheldewerven range between 54 and 95 mg kg − 1 for the seven sediments analyzed, with one peak value of 227 mg kg − 1. This higher value may be attributed to the fact that this sampling location could have been close to a waste water disposal line of the shipyard. TBT contents detected in Scheldt river sediments taken from the vicinity of the Boelwerf display more varying concentrations ranging between 44 and 316 mg kg − 1,a concentration level suggesting a high transfer of TBT contaminants from the yard into the river. The concentrations detected in the Wintham – Brussel Canal near the Fulton Marine yard are more variable and range from 4 to 271 mg kg − 1. The same variability of detected contents occurs in the vicinity of the yard in Langerbrugge with concentrations between 35 and 105 mg kg − 1. Analysis of water samples taken from the draining system of this particular yard already showed butyltin concentrations up to the mg l − 1 level. The results of this study clearly indicated that organotin contamination of the environment through dry-docking activities is not only restricted to the yard terrain itself, but also has wider polluting effects on the adjacent waterways. Further, it was shown that through the analysis of sediments originating from larger distances that the polluting impact is restricted to the immediate vicinity of the yard.
4. Conclusions This work describes the application of a novel method for the speciation analysis of organotins to a number of environmental sediment samples. Through the analyses of surficial sediments originating from shipyards and dry-docks it was concluded that dry-dock operations may create severe organotin contamination of the yard territories. Further, the results from the analysis of river sediments sampled in the vicinity of dry-docks and shipyards showed the transfer of organotin contaminants from shipyards to the adjacent rivers and show the need for effective dry-dock management and waste water treatment in order
to protect the aquatic environment. TBT was detected in the majority of the samples analyzed, often at concentrations much higher than the Environmental Quality Target for TBT in sediments, indicating that the problem of contamination of the marine environment is far from solved, despite recent alternative anti-foulants, legislation and EU directives towards the use of this compound.
References [1] R.F. Lee, A.O. Valkirs, P.F. Seligman, Environ. Sci. Technol. 23 (1989) 1515. [2] J.E. Thain, M.J. Waldock, M.E. Waite, Oceans ’87, 1987, p. 1256. [3] L. Randall, J.H. Weber, Sci. Total Environ. 57 (1986) 191. [4] R.J. Maguire, R.J. Tkacz, Y.K. Chau, G.A. Bengert, P.T.S. Wong, Chemosphere 15 (1986) 253. [5] V.F. Hodge, S.L. Seidel, E.D. Goldberg, Anal. Chem. 51 (1979) 1256. [6] C. Stewart, S.J. de Mora, Environ. Technol. 11 (1990) 565. [7] R.J. Maguire, R.J. Tkacz, J. Agric. Food Chem. 33 (1985) 947. [8] P.M. Stang, P.F. Seligman, Oceans ’86, 1986, p. 1256. [9] S.J. de Mora, N.G. King, M.C. Miller, Environ. Technol. Lett 10 (1989) 901. [10] Ph. Quevauviller, O.F.X. Donard, H. Etcheber, Environ. Pollut. 84 (1994) 89. [11] S.J. Blunden, L.A. Hobbs, P.J. Smith, in: P.J. Craig (Ed.), Organometallic Compounds in the Environment, Longman, Harlow, 1986, p. 111. [12] J. Szpunar, M. Ceulemans, V.O. Schmitt, F.C. Adams, R. Lobin˜ski, Anal. Chim. Acta 332 (1996) 225. [13] O.F.X. Donard, B. Lale`re, F.M. Martin, R. Lobin˜ski, Anal. Chem. 67 (1995) 4250. [14] BMM, Diensten van de Vlaamse Executieve, Openbare Werken en Verkeer, Bestuur der Waterwegen en van het Zeewezen, Report, October 1989. [15] C. Plasman, M.A. Demeyere, Rapport sur les Recherches de Pesticides dans les eaux de surface en Belgique, Unite´ de Gestion du Mode`le Mathematique de la Mer du Nord, Report, July 1993. [16] M. Ceulemans, F.C. Adams, Anal. Chim. Acta 317 (1995) 161. [17] W. M. R. Dirkx, R. Lobin˜ski, F.C. Adams, Anal. Sci. 9 (1993) 273. [18] R. Lobin˜ski, W.M.R. Dirkx, M. Ceulemans, F.C. Adams, Anal. Chem. 64 (1992) 159. [19] M. Ceulemans, R. Lobin˜ski, W.M.R. Dirkx, F.C. Adams, Fres. J. Anal. Chem. 347 (1993) 256.
M. Ceulemans et al. / Talanta 46 (1998) 395–405 [20] M. Ceulemans, C. Witte, R. Lobin˜ski, F.C. Adams, Appl. Organomet. Chem. 8 (1994) 451. [21] Ph. Quevauviller, O.F.X. Donard, Fres. J. Anal. Chem. 339 (1991) 6. [22] Ph. Quevauviller, in: O.F.X. Donard, S. Caroli (Eds.), Element Speciation in Bioinorganic Chemistry, vol. 135, Wiley, New York, 1996, p. 331. [23] S. Zhang, Y.K. Chau, W.V. Li, A.S.Y. Chau, Appl. Organomet. Chem. 5 (1991) 431. [24] Ph. Quevauviller, M. Astruc, L. Ebdon, Y. Desauziers, P.M. Sarradin, A. Astruc, G.N. Kramer, B. Griepink, Appl. Organomet. Chem. 8 (1994) 629. [25] Ph. Quevauviller, M. Astruc, L. Ebdon, G.N. Kramer, B. Griepink, Appl. Organomet. Chem. 8 (1994) 639. [26] W.M.R. Dirkx, R. Lobin˜ski, M. Ceulemans, F.C. Adams, Sci. Total Environ. 136 (1993) 279. [27] M. Ceulemans, Development of organometal speciation analysis by GC based hyphenated techniques and environ-
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mental applications, PhD thesis, 1996. [28] J.A. Sta¨b, U.A.Th. Brinkman, W.P. Cofino, Appl. Organomet. Chem. 8 (1994) 577. [29] O.M. Crijns, Watersysteemverkenningen, een analyse van de problematiek in aquatisch milieu, RIZA nota 92014, April 1992. [30] P.R. Willemsen, G.M. Ferrari, Emissies van organotin naar Nederlands oppervlaktewater, TNO-Report N C92.1004. [31] C.M. Adema, G.D. Smith, Development of cavitating water jet paint removal system, in: Waste Minimization and Environmental Programs within DoD, Proc. 15th Environmental Symposium, April 1987, pp. 270 – 275. [32] EPA, Guides to pollution prevention: the marine maintenance and repair industry, US Environmental Protection Agency, Concinnati, Ohio, OH 45268, EPA/625/7-91/015, October 1991. [33] R. Ritsema, Appl. Organomet. Chem. 8 (1994) 5.
Speciation of organotin in environmental sediment samples M. Ceulemans, S. Slaets, F. Adams * Department of Chemistry, Uni6ersity of Antwerpen (UIA) B-2610 Wilrijk, Belgium Received 25 May 1997; accepted 14 October 1997
Abstract An optimized sample preparation procedure for organotin speciation in sediment samples has been applied to the analysis of sediments collected in the environment. The method is based on tropolone complexation of the ionic organotins, followed by extraction into a hexane – ethylacetate mixture and derivatization by NaBEt4. The method was applied to the determination of organotin in various harbour, shipyard and dry-dock sediments in Belgium. Butyltin compounds were detected in all samples analyzed, often at high mg kg − 1 levels. A limited number of samples showed the presence of phenyltin compounds. Further, the method was adapted to the analysis of river sediments sampled from the vicinity of shipyards. Butyltin concentrations were detected at the mg kg − 1 level in the majority of samples. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Speciation; Organotin; Gas chromatography; Atomic emission spectrometry
1. Introduction The input levels of organotin compounds in the environment have been considerably restricted in the recent past in most countries due to legislation. Tributyltin (TBT), and to a lesser extent triphenyltin (TPT) used as biocides in anti-fouling paints, nevertheless remain common pollutants of the marine environment, particularly in the sediment matrix. It appears that tri-organotins and the products of their degradation accumulate in the sediment. Attention given to sediment analysis is increasing, considering that the sediment is recognized as the ultimate ‘sink’ for organotin compounds which are released into the aquatic * Corresponding author. Fax: +32 3 8202376.
environment and may create an eco-toxicological risk long after anthropogenic sources are banned from a given area. Therefore, the short residence time of TBT in the water column alone is not an adequate criterion for evaluating its potential environmental hazards. Hence, it is essential that reliable analytical methods are developed for the determination of butyl- and phenyltin compounds in sediments. In natural waters, TBT has a short residence time, with a half-life in the range of several days to weeks [1,2]. Adsorption of TBT onto suspended particulate matter is thought to be an important removal process. Randall and Weber reported that between 57 and 95% of TBT in the water column is sorbed under simulated estuarine conditions [3]. In this way a significant proportion
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of TBT appears to be deposited, and concentration factors of 103 relative to the overlying waters are common [4 – 6]. Slow degradation of TBT in sediments would increase its persistence in the aquatic environment. Studies of TBT degradation in sediment/water mixtures under experimental conditions have been carried out by Maguire et al. [7] and Stang et al. [8] and suggested that TBT has a half-life in sediments of several months. An alternative approach consists in obtaining profiles of TBT concentrations within sediment cores [9], which yields a longer half-life of 1.85 years. Similarly, Quevauviller et al. [10] in a study of sediment cores of Arcachon Bay, France, reported that TBT concentration remains high long after regulation was implemented, hence that this compound is not rapidly degraded in sediment as was previously assumed. Further, TBT has been found to accumulate to concentrations which can probably inhibit biological degradation. The same is valid for TPT compounds which have been shown to have low mobility, low aqueous solubility, and strong binding to soil and sediments in the aquatic environment [11]. Sample preparation procedures for organotin speciation analysis in sediments are generally more complicated than those for water samples. Since organotin compounds are not involved in mineralogical processes and bind onto the surface of the sediment the complete dissolution of the sediment matrix prior to the analysis is not considered necessary. The basic approach to release organotin compounds from the sediment involves, e.g. acid leaching in aqueous or methanolic medium by sonification, stirring or Soxhlet extraction with an organic solvent. Generally, sample preparation procedures for the separation of organotin compounds from sediments are time consuming (several hours). A recent alternative is the use of a low power microwave field which was shown to accelerate the leaching of the organotin species from the sediments considerably and to reduce actual leaching times to a few minutes [12,13]. Data of organotin contents detected in sediments originating from the environment in Belgium are scarce. The only study on TBT contamination, to our knowledge, was carried out
in the frame of a quality survey of dredging sludge originating from some important marine yacht- and fishing harbours [14]. The highest TBT concentrations were found in the harbour of Zeebrugge, as can be seen from Table 1. Further, it was found that locations displaying a high TBT content were also characterized by a strong organic pollution, mainly polycyclic aromatic hydrocarbons. Since TPT compounds strongly adsorb to suspended matter and sediments, they are readily detected in this matrix. During a Belgian survey on the presence of various pesticides in the environment, phenyltin compounds were found in 15% of the sediment samples, with contents ranging from 120 to 190 mg kg − 1. The highest concentrations were found in the mouth of the Yser river, in the Gaverbeek, a small tributary of the river Scheldt at Harelbeke and in the river Scheldt itself at Doel [15]. This paper presents the application of a sample preparation procedure based on tropolone complexation, liquid–liquid extraction and NaBEt4 derivatization in a monitoring study to assess the organotin pollution in a number of environmental sediments originating from various waterways in Belgium. The aim was to investigate the impact of dry-docking operations on the contamination of both surficial sediments from shipyard terrains and in river sediments originating from the vicinity of shipyards with regard to their organotin content.
2. Experimental
2.1. Apparatus GC–AES. Organotin species were separated on an HP-1 capillary column using a Model 5890 Table 1 TBT concentrations detected in marine Belgian harbours [14] Location
TBT concentration (mg kg−1)
Zeebrugge Nieuwpoort Oostende Blankenberge
8 – 895 15 29 41
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Series II gas chromatograph and detected by means of an HP Model 5921 A atomic emission detector (Hewlett – Packard, Avondale, PA). The GC was equipped with a KAS 503 (Gerstel, Mulheim, Germany) programmable temperature vaporization (PTV) injector. GC–AAS. A Varian Model 3700 gas chromatograph (Varian, Sunnyvale, CA) fitted with a RSL-150 (RSL, Eke, Belgium) megabore column, or an HP Model 5890 Series II gas chromatograph fitted with an HP-1 capillary column were used to separate the analytes prior to the detection by quartz furnace atomic absorption spectrometry (QFAAS); PE Model 2380 (Perkin Elmer, Norwalk, USA). For megabore column GC, samples were introduced on-column through a septum in a wide bore hot on-column liner. Injections on the capillary column were done using PTV as described earlier [16]. Injector, gas chromatograph, interface and detector operating conditions have been described in detail earlier for GC – AAS [17] and GC–AES [18].
2.2. Reagents Analytical reagent grade chemicals obtained from Merck (Darmstadt, Germany) were used unless otherwise stated. Deionized water, further purified in a Milli-Q system (Millipore, El Paso, TX) system was used throughout. Pentylmagnesiumbromide (2 mol l − 1 in diethylether) was obtained from Aldrich (Milwaukee, WI). Sodium tetraethylborate was obtained from Strem Chemicals (Bischheim, France). A 0.3% (w/v) aqueous solution was prepared daily. Diethyldithiocarbamic acid was prepared by dissolving 2.25 g of sodium diethyldithiocarbamate (NaDDTC) salt in water. The solution of DDTC in pentane was obtained by shaking the aqueous solution with 20 ml of 0.5 mol l − 1 of H2SO4 and extracting with 10 ml of pentane for 5 min. Acetate buffer (pH 5; 0.1 mol l − 1) was prepared by dissolving 13.6 g of sodium acetate trihydrate in 1 l of water, followed by pH adjustment with concentrated acetic acid. A 0.05% tropolone solution was prepared by dissolving the appropriate amount in hexane/ethylac-
397
etate (1/1). The sources, purity and synthesis of organotin standards have been described earlier [19].
2.3. Procedure Circa 1 g of sediment was accurately weighed and placed in a centrifugation vessel with glass stopper together with 2 ml of hydrochloric acid (32%) and 8 ml of water; 25 ml of the hexane/ ethylacetate mixture (1/1), containing 0.05% tropolone were added and the mixture was sonicated for 1 h, followed by centrifugation at 3000 rpm for 5 min. The organic phase was transferred into an extraction vessel and evaporated to dryness using rotary evaporation. Then, 0.5 ml of hexane, containing Pe3SnEt as an internal standard, were added and the complexes were derivatized by addition of 1 ml of the NaBEt4 solution together with 50 ml of acetate buffer solution. The mixture was shaken manually for 5 min and after phase separation the hexane phase was sampled for clean up/analysis. A detailed description and discussion of extract clean-up has been presented previously [20]. A Pasteur pipette was filled with basic alumina to form a plug of 5 cm. The sediment extract was introduced onto the clean-up column. After elution of the original extract volume, an additional volume of 1 ml diethylether was brought onto the clean-up column. The diethylether was evaporated from the combined eluate using a gentle stream of nitrogen.
2.4. Sampling Sampling of superficial sediments was done using a Peelman drill, or by simple collection by means of a spade. Water-underlying sediments were collected using a Van Veen grab. After removal of stones, leaves and pieces of wood, the sediment was grounded with an agate mortar and pestle. Sediments were either oven-dried at 50°C or freeze-dried and stored at −20°C until analysis, i.e. in agreement with recommendations on sampling and storage procedures for organotin analysis in the marine environment [21,22].
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Table 2 Results for the analysis of shipyard and dry-dock sediments Sample
TBT
DBT
MBT
TPT
DPT
MPT
1.26 9 0.15 0.38 90.07 —a 5.55 9 0.72
0.65 90.08 0.27 9 0.05 — 1.55 922
1.32 90.18 0.40 9 0.06 — 6.48 9 0.91
Concentration 995% confidence interval (mg g−1) 1 3 5 6
35.89 2.9 6.82 9 0.42 26.4 91.8 141 910
13.6 9 1.0 3.03 9 0.16 10.0 90.6 103 9 6
6.23 90.50 1.00 90.09 26.4 9 1.8 46.2 93.4
Concentration9 95% confidence interval (ng g−1) 2 4
3909 35 20.3 9 2.2
173 915 11.69 1.0
199 918 11.3 91.4
— —
— —
— —
Mean results for three replicate analyses of each sediment. Concentration below detection limit (B1 ng g−1).
a
2.5. Certified reference materials
3. Results
To evaluate the performance of the plethora of existing sample preparation procedures and instrumental setups used among different laboratories, certified reference materials (CRM’s) were prepared by different organizations for the quality control of analytical results. Analysis results of CRM’s presented in some reports show that the reliability of sample preparation is often not sufficient and that several limitations still remain. Especially the accurate determination of monobutyltin (MBT) remains doubtful since, according to some reports on certification experiments [23– 25], no reliable method for the determination of this compound has been reported up to now. This is apparent from Table 2. Analysis of CRM’s proved that the method presented is able to accurately determine TBT and dibutyltin (DBT) in sediments, while MBT determination in general still remains doubtful due to the absence of reliable, or no or only indicative values for this compound in reference materials. However, the method was shown to be suitable for MBT determination in certain sediments [16]. An attempt to apply the developed procedure to the analysis of phenyltin compounds led to the conclusion that the determination of these species is most favorable in the absence of any tropolone complexing agent and using acetic acid for leaching.
3.1. Determination of organotin in harbour and dry-dock sediments 3.1.1. Shipyard located in the Antwerp harbour Huge point sources such as dry-dock facilities are responsible for the release of the largest fraction of TBT into the aquatic environment. An investigation was carried out to assess the contamination of a shipyard terrain after years of intense dry-docking activities. Further, the influence of these activities on the contamination of the harbour sediment was also investigated. Fig. 1 shows the location of the sampling sites with the sampling points indicated. A total of five surface samples was taken from the shipyard terrain, three at places where grit blasting activities had taken place, and two samples from other locations at the yard, this in order to assess the background concentration found at the terrain. The investigated ship repair yard was located in the Antwerp harbour, which itself is characterized by intense shipping in an almost enclosed environment with a low flushing rate. In a previous study on the determination of organotins in waters of the Antwerp harbour, which was carried out over a 4-month period between May and August 1991, two sampling locations (W1, W2) were situated in the vicinity of the shipyard investigated in the present study [26].
M. Ceulemans et al. / Talanta 46 (1998) 395–405
Fig. 1. Sampling locations.
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M. Ceulemans et al. / Talanta 46 (1998) 395–405
400
This previous study indicated an overall TBT contamination level in the harbour in the range of 10–45 ng l − 1. The concentrations detected at locations W1 and W2 were significantly higher with concentrations ranging between 50 and 440 ng l − 1 over the 4-month study period for these two locations. These elevated concentrations found in the water column at these two locations were found due to the discharge of hazardous amounts of TBT in hosing-down water which originates from the washing of ships’ hulls, with a high-pressure hosing system before repainting activities. The contaminated water first remains for several days in a sinking-basin and is afterwards released into the poorly flushed harbour dock area. This study already showed the impact of dry-dock activities on the contamination levels in waters of the Antwerp harbour. In the present study, the impact of dry-docking operations on the contamination of the yard terrain, and harbour sediment was evaluated. The results of the analyses are presented in Table 3. From the results it can be seen that sediments 1, 3 and 6, sampled at locations where grit blasting takes place, generally display very high TBT concentrations at the mg kg − 1 level. Comparison with the Environmental Quality Target (EQT) value for TBT in sediments, set at 1 – 2 mg kg − 1 and implemented now in most European countries indicates severe contamination of these surface sediments [27]. Especially the concentration found in sediment 6 (141 mg kg − 1), originating from another smaller dry-dock located in the Antwerp harbour, is at extremely high level. Also Table 3 Results for the analysis of dredging sludge samples originating from the Ostend harbour Sample
1 2 3 4
Concentration 9 95% confidence interval (mg g−1) TBT
DBT
MBT
1112 9 120 169 9 14 394 9 31 450 9 32
2329 24 63.9 9 6.0 1819 13 217 9 14
80.5 98.1 29.292.3 10698 123 99
Mean results of three replicate analyses for each sediment.
DBT and MBT, the intermediate products of TBT degradation to inorganic tin, were found in all the samples. Further, phenyltin compounds were as well detected in these samples, however at much lower concentrations. The presented concentration figures for monophenyltin (MPT) should be considered as indicative values, as extraction and derivatization for this compound was found to be irreproducible as shown earlier [28]. Triphenyltin compounds (mainly TPT fluoride and small amounts of TPT chloride) are used in anti-fouling paints, however to a much lesser extent compared to TBT compounds. About 80% of all anti-fouling paints used contain TBT oxide or TBT metacrylate/methylmetacrylate copolymer, 12% are TBTF based and 8% are TBTF based [29,30]. Since TPT compounds are only used in free-association paints, and since there seems to be a general agreement to discontinue the use of this type of paint it is expected that discharges of TPT compounds from anti-fouling paints will decrease in the near future. The detected contents in samples 2 and 4 taken at places on the yard where no dry-docking operations such as grit blasting, washing, painting, etc. take place display much lower contents at mg kg − 1 level. However, the fact that butyltin compounds are detected at these locations may be attributed to an overall contamination of the yard terrain. Sediment 5, collected in the harbour, displays very high TBT concentrations, most probably originating from the hosing-down of TBT waste water in the harbour water and accumulation in the underlying sediments which act as a ‘sink’ for TBT. A chromatogram for this sediment after sample preparation and GC–AAS measurement is shown in Fig. 2. The results of this study indicate the need for strict dockyard management to minimize waste generation from dry-docking activities and treatment of contaminated waste waters. Potential waste minimization methods for marine maintenance and repair operations include the minimization of fugitive oversprays of paint (e.g. by changing application methods), the minimization of abrasive blast wastes and of chemical stripping wastes. Apart from high pressure hydro-washing abrasive blasting is often used to remove paint
M. Ceulemans et al. / Talanta 46 (1998) 395–405
Fig. 2. Chromatogram for a sample of Antwerp harbour sediment: (1) MBT; (2) DBT; (3) TBT; (is) internal standard (Pe3SnEt).
layers. The most commonly used blasting media are sand or grit together with a large volume of water. The presence of paint chips containing hazardous metallic and/or organometallic biocides makes abrasive blasting wastes potentially hazardous. Blast waste water generally constitutes the largest single waste stream for many yards. For instance, wet abrasive blasting of an average sized naval vessel can generate up to 180 tons of wet abrasive and ca. 2 000 000 l of contaminated water [31]. At the moment research and testing is underway on a number of innovative alternatives to both grit blasting and chemical stripping [32]. Segregation and recycling of blast media is possible because of the difference in density between the grit materials and the waste paint chips. Therefore, in many cases the contaminated grit can be reused several times before becoming too contaminated and requiring off-site disposal. An
401
approach to prevent fugitive dust emissions would be to enclose the area with plastic sheeting or screening, this confining the waste to the immediate vicinity of the blasting. After blasting has been completed, the waste should be collected and transported to a licensed landfill. Chemical stripping wastes primarly consist of the stripping agent, of which methylenechloride is the most commonly used, and paint sludges. Waste minimization would include the use of less toxic stripping agents such as inorganic strippers consisting of aqueous solutions of caustic soda, and the reuse and recycling of contaminated strippers. Waste water should be treated in such a way that its TBT contents reduced to a level acceptable for discharge to river or estuarine waters. Equipment for this purpose is commercially available and generally uses a 4-stage process, two concerned with solids (principally paint solids) reduction and two concerned with removing TBT from the water. Briefly, the different stages are as follows: (1) flocculation and settling in which the pH of the raw wash water is adjusted to effect flocculation and agglomeration of the solids present; (2) filtration where the supernatant water from the settling stage is pumped to a 2-stage filtration system, and particles are removed to the sub-micron diameter range to ensure that paint particles which could still release TBT to the surrounding water are not present in the subsequent treatment steps; (3) carbon adsorption where the first stage of dissolved TBT removal is effected by adsorption onto activated carbon; (4) after passing through the carbon bed, the process water passes through a filter, to remove residual carbon particles and then to a device whereby it is irradiated with short-wave UV light. The concentrations of TBT can be effectively reduced to concentrations less than 0.2 mg l − 1 by oxidation reactions induced by the UV light, producing harmless tin oxide. The UV light irradiation step is the final stage in this type of waste water treatment plant. However, the majority of commercial shipyards discharge their effluents directly to the aquatic environment at no direct costs. Any treatment system thus becomes an additional cost burden to their operations. This cost burden will only be acceptable commercially if all yards (in-
402
M. Ceulemans et al. / Talanta 46 (1998) 395–405
side and outside EU) are required to undertake environmental protection measures simultaneously. It is estimated that through the use of waste water treatment plants a reduction of emissions up to 85% could be accomplished.
height of the TBT concentration detected, plus the pattern of the concentrations of the degradation products DBT and MBT, which were found in much lower concentrations, indicate recent dis-
3.1.2. Dredging sludge from the Ostend harbour Dredging sludge samples were originating from various locations in the Ostend harbour where dredging activities had taken place. The harbour is characterized by intense shipping activities from pleasure crafts and ferry ships. Samples were analyzed in order to assess the organotin levels present in the Ostend harbour. Further, analyses of these samples would give an idea about the organotin contamination which may be introduced into non-contaminated areas, through dumping of these dredging sludges. The results of the analyses are presented in Table 4. All samples showed the presence of butyltin compounds at concentrations up to mg kg − 1 level, indicating contamination of the Ostend harbour due to shipping activities. Further, results suggest that dredging sludges originating from harbours and marinas should be collected and treated with care in order to avoid contamination of other areas through dumping of this sludge. Contaminated soils must be removed and either incinerated in special plants or be deposited at special waste disposal sites according to local or government regulations. Generally, it was found that dredging activities reduce TBT concentrations in harbours and marinas [33]. Dredging removes TBT-contaminated sediments, and because of the sediment-water partitioning, finally results in lower TBT concentrations in the water phase.
Table 4 Results for the analysis of river sediments originating from the vicinity of shipyards
3.1.3. Shipyard for pleasure crafts A surface sediment was taken from a small shipyard located at the Zuidwillemsvaart (Bocholt, Limburg). The yard is mainly used for the maintenance of small vessels and pleasure crafts. Amounts detected were 6.6090.08 mg kg − 1 for TBT, 1.67 90.20 mg kg − 1 for DBT and 1.15 9 0.05 mg kg − 1 for MBT. A chromatogram for this sediment, after sample preparation and GC– QFAAS measurement is shown in Fig. 3. The
Shipyard
Concentration 995% confience interval (mg kg−1) TBT
DBT
MBT
Rupelmonde
17.3 9 2.8 30.5 92.8 65.8 911.8 76.8 94.5 73.3 95.8 21.2 91.3 63.5 95.5 2.37 91.12a
30.5 9 3.3 61.5 95.8 97.8 915.3 221 9 11 169 931 41.5 94.3 117 96 2.78 9 0.80
19.4 91.6 34.3 91.8 47.8 9 10.5 130 99 77.0 915.3 19.2 9 3.1 69.394.3 0.83 9 0.13
Nieuwe
54.0 9 6.0
106 9 8
49.39 5.3
Scheldewerven
55.3 98.5 227 9 24 89.0 96.0 85.0 94.3 88.3 9 3.5 95.0 911.3 BDLa
98.3 98.8 196 9 12 155 911 144 99 181 9 15 168 99 5.38 9 1.20
52.3 99.8 111 96 70.8 9 5.5 70.3 9 5.5 72.0 9 6.8 78.094.5 2.69 9 0.58
Boelwerf
133 917 316 930 82.0 910.4 43.7 9 6.1 BDLa 4.49 90.63a
166 911 286 931 90.6 910.8 96.6 9 11.0 3.49 9 1.2 4.10 9 0.82
60.0 94.2 108 910 32.3 9 2.3 34.9 9 4.2 9.65 9 2.6 7.75 9 1.55
Fulton Marine
50.3 94.8 271 978 51.2 95.6 68.2 96.2 4.44 91.00 134 99 9.11 91.40 7.71 91.1
140 914 1499 9173 194 918 260 916 47.3 9 5.2 119 99 43.5 9 4.1 58.7 95.2
82.0 9 10.5 717 9144 81.0 910.0 150 9 15 20.4 9 2.7 47.3 9 4.4 19.9 9 2.5 26.4 9 2.6
Langerbrugge
105 96 34.6 93.8 88.5 910.1 2.91 9 0.72a BDLa
42.4 92.6 31.1 9 2.2 22.1 93.5 BDL BDL
15.4 91.1 19.3 92.5 9.50 91.9 BDL BDL
BDL, below detection limit (B1 mg kg−1). Mean results of three replicate analyses for each sediment. a Sediments taken at larger distances from the yard.
M. Ceulemans et al. / Talanta 46 (1998) 395–405
Fig. 3. Chromatogram for a sample of Bocholt shipyard sediment: (1) MBT; (2) DBT; (3) TBT; (is) internal standard (Pe3SnEt).
charges of TBT, suggesting the illegal usage of TBT-containing anti-fouling paints, since following current legislation the use of these paints is forbidden on ships smaller than 25 m.
3.1.4. Determination of organotin in ri6er sediments Analyses of sediment samples originating from shipyards and dry-dock terrains revealed the presence of very high concentrations of various organotin compounds. In cooperation with the Flemish Environmental Agency (VMM) a sampling campaign was carried out (Summer ‘95) in which river sediments were taken from the vicinity of shipyards. The aim of the study was to investigate whether the pollution is restricted to the yard and dock terrains itself or also has a wider effect on the contamination of the adjacent rivers. A total of 35 river sediments, originating from the vicinity of five different yards located in Flanders were analyzed. For a given shipyard sampling was carried at different locations in the river. Further, for each shipyard sediments were also taken at larger distances from the yard, up- and down-stream on the river, in order to assess the polluting impact of shipyard activities over longer distances.
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The results of all 35 sediments are presented in Table 4. Generally, butyltin compounds were detected in all river sediments which were sampled in the vicinity of the shipyards. Phenyltin compounds were not detected in any of the samples. The detected levels are, in comparison with contents detected on the yard terrain itself, generally much lower, however in the majority of the samples analyzed they are a multiple of the EQT value for TBT in sediments, set at 1–2 mg kg − 1. Concentrations detected in river sediments sampled at larger distances, generally display contents below detection limits or at the low mg kg − 1 levels indicating the local impact of dry-dock operations on the contamination of adjacent rivers. A chromatogram for a sample of river sediment is shown in Fig. 4. TBT concentrations detected in the river sediments originating from the vicinity of the Rupelmonde shipyard range between 17–77 mg kg − 1 representing an overall contamination level in the seven sediments sampled in the vicinity of the
Fig. 4. Chromatogram for a sample of river sediment: (1) MBT; (2) DBT; (3) TBT; (is) internal standard (Pe3SnEt).
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yard. TBT contents detected in the river Scheldt in the vicinity of the Nieuwe Scheldewerven range between 54 and 95 mg kg − 1 for the seven sediments analyzed, with one peak value of 227 mg kg − 1. This higher value may be attributed to the fact that this sampling location could have been close to a waste water disposal line of the shipyard. TBT contents detected in Scheldt river sediments taken from the vicinity of the Boelwerf display more varying concentrations ranging between 44 and 316 mg kg − 1,a concentration level suggesting a high transfer of TBT contaminants from the yard into the river. The concentrations detected in the Wintham – Brussel Canal near the Fulton Marine yard are more variable and range from 4 to 271 mg kg − 1. The same variability of detected contents occurs in the vicinity of the yard in Langerbrugge with concentrations between 35 and 105 mg kg − 1. Analysis of water samples taken from the draining system of this particular yard already showed butyltin concentrations up to the mg l − 1 level. The results of this study clearly indicated that organotin contamination of the environment through dry-docking activities is not only restricted to the yard terrain itself, but also has wider polluting effects on the adjacent waterways. Further, it was shown that through the analysis of sediments originating from larger distances that the polluting impact is restricted to the immediate vicinity of the yard.
4. Conclusions This work describes the application of a novel method for the speciation analysis of organotins to a number of environmental sediment samples. Through the analyses of surficial sediments originating from shipyards and dry-docks it was concluded that dry-dock operations may create severe organotin contamination of the yard territories. Further, the results from the analysis of river sediments sampled in the vicinity of dry-docks and shipyards showed the transfer of organotin contaminants from shipyards to the adjacent rivers and show the need for effective dry-dock management and waste water treatment in order
to protect the aquatic environment. TBT was detected in the majority of the samples analyzed, often at concentrations much higher than the Environmental Quality Target for TBT in sediments, indicating that the problem of contamination of the marine environment is far from solved, despite recent alternative anti-foulants, legislation and EU directives towards the use of this compound.
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