The extent of hydrocarbon contamination in the marine environment from a research station in the Antarctic

Martne I'othaion Bulletin, Volume 25, 9 12, pp. 288 292, 1992. Printed in (]teat Britain

0 0 2 ) 3 2 6 X / 9 2 $5 (t0+0.00 © 1992 Pergamon Press l.td

The Extent of Hydrocarbon Contamination in the Marine Environment from a Research Station in the Antarctic G. C. CRIPPS

British Antarctic Survey, Natural Environment Research Council, High Cross, Madinglev Road, Cambridge ('B3 0ET, UK

Low level hydrocarbon contamination is measurable in the vicinity of Antarctic stations, N-alkane and polycyclic aromatic hydrocarbon (PAH) concentrations in seawater and sediment at Signy Station, South Orkney Islands indicated contamination was confined to within a few hundred metres of the station. Total n-aikane concentrations in seawater decreased from 7.6 to 2.6 lag i -I within 5 0 0 m of the station. All n-alkane values in seawater were within the limits of variation for oceanic waters proposed by cripps (1992), although the distribution pattern suggested pollution from the station. The total PAH concentration in seawater varied between 110 and 2 1 6 ng I-~. These values showed no trend with distance from the station and were all slightly higher than for the open ocean. The n-alkane and PAH concentations in the surface sediment declined to low levels within 3 7 5 m of the station. This indicates that a large proportion of the hydrocarbons entering Factory Cove was deposited from the water column. Sediment n-alkane concentrations were similar at all depths of the cores when collected more than 125 m from the station. PAH levels in the sediment appeared to be due to local input, including a small spill in 1965.

Hydrocarbon pollution of the Antarctic marine environment remains relatively insignificant (Cripps, this volume). In addition to isolated incidents, principally shipwrecks, there is continuous low-level contamination due to derelict whaling stations, research stations and associated activities, such as shipping. It may be expected that hydrocarbon concentrations will be elevated in the vicinity of coastal research stations, as a result of the small amounts of fuel and other materials accidentally introduced into the environment. This paper describes the extent of hydrocarbon contamination at a research station on Signy Island, South Orkney Islands in the northern Weddell Sea. The British Antarctic Survey (BAS) have maintained a research station at Factory Cove, Signy Island, since 1947. The'station is not large, with a maximum summer 288

population of 27. In 1964, a 400 t capacity bulk fuel tank was constructed. This is replenished annually by ship. In the early period of operation it was also used to resupply ships during the Antarctic season. Fuel transfers amounted to about 100 t every auslral summer. With the installation of larger generators, this has increased to over 200 t during the last decade. Prior to the establishment of the research station, there was a history of whaling at Signy Island, that commenced in 1907. Although most of the whaling was undertaken using floating factory ships which anchored in Factory Cove, a shore station was built in 1921 on the site now occupied by the BAS station. This operated for only 4 yr, and whaling at Signy Island declined during the 1930s. The history and location of the research station makes it ideal to study the impact of low-level contamination associated with human activity in the Antarctic. The extent of contamination from the statxon was investigated by analysing the n-alkanes and polycyclic aromatic hydrocarbons (PAH) in the seawater and sediment from Factory Cove and Borge Bay (Fig. 1). Sampling and Methods

Samples of seawater and sediment were taken from six sites on a transect between the station and Billie Rocks and in Borge Bay (Fig. 1). Seawater was sampled with glass stoppered bottles and sediment was taken with a 10 cm diameter corer to a depth of 20 cm. An uncontaminated seawater sample was also taken in open ocean, 3 km from the station. Sediment was only sampled to a depth of 10 cm before bedrock was encountered at the site nearest the station and in Borge Bay. All the sediment samples were fine silt, except from Borge Bay where some larger material was found. A sample of 'soil' contaminated with diesel from the shore near the station was taken for comparison with the samples from Factory Cove. All the samples were collected in February 1988 and stored at - 2 0 ° C for analysis in the UK. The seawater samples (500 ml) were filtered through 0.45 ~tm Whatman WCN membranes and passed

Volume 25/Numbers 9-12

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through a Millipore SEP-PAK C~s cartridge to extract the total dissolved organic fraction. The organic fraction was then eluted from the cartridge with hexane (1 ml) and concentrated to 100 ~tl. The sediment samples were dried at 40°C, ground in a mortar and pestle then sieved at 2 mm. Some larger material was removed from the Borge Bay sample which accounted for 20% of the total dry weight. Portions of sediment (10 g) were then extracted with chloroform in a Soxhlet apparatus. The chloroform solution was evaporated under vacuum and the residue redissolved in a small volume of hexane ( = 2 5 0 ~tl). The n-alkanes and PAH were isolated from the concentrated extacts by liquid chromatography on 5% deactivated silica gel. Individual n-alkanes were quantified by capillary GC and PAH by H P L C using squalane and triphenylene as internal standards. The analytical procedures and detection limits have been described in full by Cripps (1989). • 0tal n-alkane was estimated by the summation of the C~5-C~ 4 compounds and total PAH by summation of the compounds resolved by HPLC.

Results and Discussion The hydrocarbons in a small area of soil, close to the shore and heavily loaded with diesel, were used as a guide to identify pollution in Factory Cove and Borge Bay. The contaminated soil had a total n-alkane concentration of 1 220 000 Fg kg -~ and a total PAH of 71 000 #g kg-L The n-alkane pattern was dominated by compounds with less than 20 carbon atoms (Fig. 2). This is typical of fresh contamination--weathered samples have a smaller proportion of lower carbon number compounds. Phenanthrene, fluoranthene,

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Fig. 2 N-alkane profiles for the contaminated soil on shore and the

seawater from Factory Cove, Borge Bay and nearby open ocean. pyrene, dibenzanthracene and benz(ghi)perylene were the major components in the PAH fraction (Table 1). The hydrocarbon content of the seawater in Factory Cove reflected the most recent input of contamination in the area. The residence time of water in this small cove has not been defined, but it is likely that it is effectively flushed on a scale of days during the summer. Total n-alkane concentrations decreased with distance from the station (from 7.6 to 2.6 btg 1-*) but showed a slight increase offshore at the deeper site in Borge Bay and in the open ocean (Fig. 3). The concentrations were all within the limit of variation for the Southern Ocean (8.1 btg 1 I) proposed by Cripps (1992). The distribution patterns of the n-alkanes compared to the open ocean between the station and Billie Rocks (Fig. 1) had a higher proportion of the C,s289

Marine Pollution Bulletin TABLE l Polycyclic aromatic hydrocarbons in contaminated soil, seawater and surface sediment (to a depth of 2.5 cm) 125 m from Signy research station. Contaminated soil (btg kg -I )

Compound Naphthalene Phenanthrene Anthracene Fluoranthene Pyrene Benz(a)anthracene Chryscne Benz(b)fluoranthene Benz(k)fluoranthene Benz(a)pyrene Dibenzanthracene Benz(ghi)perylene

Seawater (ng 1-I )

Surface sediment (~ag kg -1)

nd 136.7 1(I.S 4.3 nd 0.3 1.3 1.1 nd 0.1 0.8 nd

nd 9.{1 3.9 18.6 4.2 4.7 20.6 3.7 5.4 1.3 1.3 7.4

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ponents were anthracene and fluoranthene, comprising 5 - 1 0 % of the total PAH in Factory Cove and Borge Bay and 39% in the open ocean. The profiles were similar for each inshore site, which suggested the same origin for the PAH. The hydrocarbons in the surface sediment (top 2.5 cm) were another record of recent input, reflecting the deposition of hydrocarbon material associated with particulates from the water column or direct run-off. Concentrations of n-alkane and PAH showed a sharp decline within a few hundred metres of the station (Fig. 4). Levels of n-alkanes were highest (1731 lag kg -I) [n the core taken from the site 125 m from the station, arid lowest at Billie Rocks (64 lag kg -t) and in Borge Bay (44 p,g kg-~). The n-alkane profiles varied with distance from the station. At the two sites nearest the station low carbon number compounds (C~7-C>) predominated, similar to the contaminated soil on shore. The sites further away from the station were dominated by higher carbon numbers, in particular the C_~7 to C3o compounds, as in the seawater. The total PAH concentration in the surface sediment was also highest close to the station and decreased from 280 to 14 lag kg -~ within 500 m (Fig. 4). Major PAH components in the sediments were phenanthrene, fluoranthene and chrysene. Phenanthrene and fluoranthene were also major components in the contaminated soil on shore (Table 1). High levels of PAH in the sediment compared to seawater were probably due to the deposition of compounds adsorbed onto particulate

0

3000 (a)

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Fig. 3 Total n-alkanes and total polycyclic aromatic hydrocarbons (PAH) in seawater with distance from Signy research station.

1500-

C~ compounds. The presence of lower carbon number compounds indicated a contribution to the alkane fraction from diesel, such as that which contaminated the soil near the soil. The proportion of C~5-C~s compounds decreased with distance from the station, compared to the C > - C > compounds which were present in similar concentrations for all the samples except at the Billie Rocks site 500 m from the station. At this site higher molecular weight n-alkanes (>C2~) were not detected and the highest level of total PAH was observed (Fig. 3), indicating recent contamination. The C > - C > compounds predominated at the sites which were farthest from the station in Borge Bay and the open ocean (Fig. 2), and these samples had the same n-alkane patterns as those found throughout the Atlantic sector of the Southern Ocean (Cripps, 1992). In contrast to the n-alkanes the levels for PAH in seawater did not show a trend with distance from the station, varying between 110 and 216 ng 1-~ in Factory Cove and Borge Bay (Fig. 3). The inshore PAH levels were higher than in the limit of variation proposed by Cripps (1992) for the open ocean (76 ng 1-~). Total PAH content of the open ocean sample was the lowest (53 ng 1-~). Phenanthrene was the major component at all the sites, comprising 8 5 - 9 0 % of the PAH fraction inshore and 43% offshore. The other significant corn290

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Volume 25/Numbers 9-12

matter. The association between hydrocarbons and particulates is well known and is accentuated at low temperatures (Meyers & Quinn, 1973). The sampling programme was carried out in the season of high deposition (Gilbert, 1991), when up to 300 mg (dry wt) m 2 day -~ of particulate matter may be deposited in Borge Bay (Clarke, unpublished results). The depth profiles of the sediment cores from Factory Cove should contain a historical record of Hydrocarbon concentrations. However there were no consistent patterns. In three out of five cores total n-alkane levels decreased with increasing depth (Fig. 4). One core taken 375 m from station had marginally higher levels of n-alkanes at the middle depth (2.5-10 cm). In the sediment 125 m from the station the n-alkane pattern varied with depth. The dominant n-alkane was the C w compound in the top 2.5 cm, C:~ in the next 2.5-10 cm and C3~ in the 10-20 cm deep section (Fig. 5). Only the top sediment near to the station had a high proportion of the lower carbon number compounds. At the other sampling sites, further from the station, the pattern was similar to the 10-20 cm deep section at each depth. Localized and continuous input was reflected in the elevated levels of PAH in the samples taken closest to the station. Nearest to the station the total PAH concentration did not change with depth and 125 m distant levels decreased with depth (Fig. 4). At 250 m from the slation levels increased with depth. This could be a record of an incident in 1965 when high winds parted the supply ships mooring lines and the refueling pipe was severed. The refuelling pipe would have been run ashore close to where the core was taken. The extent of the contamination was not documented. Sediment age ~as calculated from the rate of deposition in the cove of 750 g (dry wt) m 2 yr -r (Clarke, unpublished results). The age of the sediment at 10 cm was estimated at 34 yr. ignoring any bioturbation. The middle depth (2.510 cm) 375 m from the station had the highest levels for that core, which mirrored the concentrations of n-alkanes. This may have been the result of a more recent unrecorded spill. The lowest levels were at Billie Rocks, 500 m from station, and were the same for each depth in the core. This was probably the local background level for total PAH in sediment. The change in 250-

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Fig. 5 N-alkane patterns for sediment at different depths from the site 125 m from Signy research station.

PAH concentrations were much less marked with depth than those for n-alkanes. This was due to the loss of lower carbon number compounds from the top 2.5 cm. The distribution of PAH in Factory Cove was similar at all the sites and at each depth suggesting that any contamination was of the same origin. Recent reports provide comparisons to the levels of hydrocarbon contamination at Signy Island. Lenihan et al. (1990) found hydrocarbons in the sediment adjacent to the ice-dock at McMurdo Station to be in excess of most polluted temperate harbours (total purgeable hydrocarbons up to 4 500 000 btg kg ~). The contamination was chronic, but as at Signy, very localized. Kennicutt et al. (1991) reported on the fate of oil spill related hydrocarbons near Palmer Station, one year after the Bahia Paraiso rain aground in Arthur Harbor, Anvers Island. Sediments close to the wreck were contaminated with levels up to 1723 Fg kg -~ for n-alkanes and 1653 btg kg -I for PAH. Close to the station the sediments reflected the non-spill related activities with up to 280 btg kg -~ n-alkanes and 550 btg kg -j PAH. All these concentrations were higher than those from Signy Island except for n-alkanes close to the station, which were similar to those close to the shipwreck. The hydrocarbon contamination at Arthur Harbor was spread over a much wider area ( = 3 0 km 2) than at Factory Cove. At the sub-Antarctic island of South Georgia, Platt & Mackie (1980) reported on hydrocarbon levels in King Edward Cove. The level of total n-alkanes in the seawater (5.8 btg 1-~) was similar to Factory Cove. There were higher total n-alkane concentrations in the top sediment ( = 3 0 0 0 btg kg -~) and lower total PAH (100 #g kg -~) compared to the sample site next to the station at Signy. The highest PAH concentrations were below 20 cm depth in the sediment. This was a record of pollution when Grytviken whaling station was operating in the cove, The hydrocarbon input was much reduced after the station was closed in 1965. The extent of contamination at Factory Cove, Signy Island is restricted to a few hundred metres from the station and represents a small threat to the Antarctic environment. The sediment close to the station has elevated levels of hydrocarbons, but the levels in seawater is put into perspective when compared to the inherent variation of the Southern Ocean as a whole (Cripps, 1992). Although the pattern of n-alkanes in seawater nearest the station suggested a measure of contamination, the total n-alkane concentrations did not exceed oceanic levels. Total PAH concentrations were also within the range of values for the ocean, but all above the upper quartile of that dataset. The fact that PAH levels were similar for all inshore sites and higher than the bulk of the open ocean implies that scavenging of PAH by particulates was rapid within the cove or that PAH entered the water column in the particulate phase. Using the same deposition rate as that for calculating sediment age, total input to the cove is estimated to be 68 g of n-alkanes and 8 g of PAH per year (the area of the cove was calculated to be 1 × 105 me). The deposition of hydrocarbons to the sediment would not be uniform throughout the cove and patches 291

Marine Pollution Bulletin of higher

PAH

levels might be expected

to have

a

physiological impact on the benthos. Any hydrocarbons t h a t r e m a i n e d in t h e d i s s o l v e d p h a s e w e r e d i s p e r s e d in the Southern Ocean, where there was no perceptible change in concentration.

1 would like to thank Neil Gilbert who collected the water and sediment cores, and Julian Priddle for his advice on the manuscript.

Cripps, G. C. (1992). Natural and anthropogenic hydrocarbons in the Antarctic marine environment. Mar. Pollut. Bull. 25,266-273. Cripps, G. C. (1992). Baseline levels of hydrocarbons in seawater of the Southern Ocean--natural variability and patterns. Mar. Pollut. Bull. 24, 109-114.

292

Cripps, G. C. (1990). Hydrocarbons in the seawater and pelagic organisms of the Southern Ocean. Polar Biol. 10, 393-402. Cripps, G. C. (1989). The Extraction and Analysis of Hydrocarbons in Marine Samples. British Antarctic Survey, Cambridge. Gilbert, N. S. (1991). Microphytobenthic seasonality in near-shore marine sediments at Signy Island, South Orkney Islands, Antarctica. Estua~ Coast. Shelf Sci. 33, 89-104. Kennicutt, M. C., Sweet, S. T., Fraser, W. R., Stockton, W. L. & Culver, M. (1991). Grounding of the Bahia Paraiso at Arthur Harbor, Antarctica. 1. Distribution and fate of oil spill related hydrocarbons. Envir. Sci. Technol. 25,509-518. Lenihan, H. S, Oliver, J. S., Oakden, J. M. & Stephenson, M. D. (1990). Intense and localised benthic marine pollution around McMurdo station, Antarctica. Mar. Pollut. Bull. 21,422-430. Meyers, P. A. & Quinn, J. G. (1973). Association of mineral particles and hydrocarbons in saline solution. Nature, Lond. 244, 23-24. Platt, H. M. & Mackie, P. R. (1980). Distribution and fate of aliphatic and aromatic hydrocarbons in Antarctic fauna and environment. Helgola'nder Meeresunters. 33. 236-245.