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Organic compounds and trace metals of anthropogenic origin in sediments from Montego Bay, Jamaica: assessment of sources and distribution pathways
Environmental Pollution 123 (2003) 291–299 www.elsevier.com/locate/envpol
Organic compounds and trace metals of anthropogenic origin in sediments from Montego Bay, Jamaica: assessment of sources and distribution pathways Rudolf Jaffe´a,b,*, Piero R. Gardinalia,b, Yong Caia,b, Aaron Sudburrya, Adolfo Fernandeza,c, Bernward J. Hayd a
Environmental Geochemistry Laboratory, Southeast Environmental Research Center, Florida International University, Miami, FL 33199, USA b Department of Chemistry, Florida International University, Miami, FL 33199, USA c Department of Environmental Studies, Florida International University, Miami, Fl 33199, USA d The Louis Berger Group, Inc., 75 Second Avenue, Suite 700, Needham, MA 02494, USA Received 4 June 2002; accepted 13 September 2002
‘‘Capsule’’: Sources and distribution pathways were identified. Abstract Surface sediments throughout Montego Bay, Jamaica were collected in 1995 and analyzed for their trace metal and trace organic contaminant content. A variety of trace metals, petroleum hydrocarbons, polycyclic aromatic hydrocarbons, coprostanol as well as chlorinated hydrocarbons such as pesticides and polychlorinated biphenyls were detected and provide evidence for several anthropogenic inputs to the bay. Two main sources of these chemicals are the Montego River and the North Gully, the latter being more significant. Particle-associated pollutants were found to be distributed along the Montego River plume, as well as being transported by the prevailing water currents to the South-Western sections of the bay, probably through re-suspension of enriched fine sediments from the North Gully outfall area. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: Trace metals; Hydrocarbons; Pesticides; PCBs; Sewage; Sediments; Montego Bay; Jamaica
1. Introduction The City of Montego Bay is the second largest city in Jamaica (population about 100,000). The center of the city is located around a shallow embayment, Montego Bay (Fig. 1), which includes an engineered port basin to the southwest that serves commercial shipping and large cruise ships. Montego Bay is an open bay, approximately 2 km wide and 1.5 km long at its entrance. Water depths gradually increase from shore to the open sea. At its mouth, the Bay is about 50–100 m deep, whilst the port is only 10 m in depth, and is surrounded by urban and some industrial developments, including an oil storage facility. Point source discharges from * Corresponding author. Tel.: +1-305-348-24-56; fax: +305-34840-96. E-mail address: jaffer@fiu.edu (R. Jaffe´).
these facilities are largely limited to stormwater runoff. Sediments in the bay consist of mainly sand and silt with greater concentrations of silt at the mouth of the Montego River (Berger, 1996), which is the largest freshwater body entering the bay. Otherwise, there are several small drains and gullies. The river extends approximately 10 km inland, and has a mean annual discharge rate of about 2 m3 s 1 (Berger, 1996). Highest discharge occurs during the two rainy seasons in June and in October/November. The flow during a 100-year rainstorm has been estimated at 720 m3 s 1 (Berger, 1996). The watershed is rural with undeveloped woodlands, small towns, pastures, banana and sugar cane plantations, and other agricultural fields. The river does receive effluents near its mouth from the water treatment facility of the City of Montego Bay (0.12 m3 s 1). This has increased since 2000 due to the construction of a new plant along with an expanded sewage collection
0269-7491/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(02)00368-8
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Fig. 1. Map of Montego Bay indicating sample locations. For convenience, the site numbering system used was the same as in Berger (1996). General water circulation pattern is indicated by arrow.
system. In addition to treated sewage, the Bay receives raw sewage and street runoff through small drains and gullies. Our purpose was to assess existing environmental conditions of Montego Bay through detailed chemical analyses of its sediments. Between 1992 and 1996 Louis Berger Group, Inc. was contracted by the US Agency for International Development to conduct an extensive monitoring study for the coastal waters and surrounding areas of Montego Bay in preparation for the construction of the new wastewater treatment facility. This study provided an opportunity to evaluate additionally the environmental conditions of the sediments in the Bay. Potential contaminants were analyzed in sediment grab samples from the Bay, including trace metals, polychlorinated biphenyls (PCBs), petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), sewage markers such as coprostanol and chlorinated pesticides in an effort to evaluate different pollution sources to the Bay. To the best of our knowledge this is the first report on the detailed characterization of sedimentary organic contaminants in coastal waters of Jamaica.
2. Methods 2.1. Sampling Sediment grab samples were collected in 1995 from 16 stations across the Bay (Fig. 1) using an Ekman Dredge (Wildco, Michigan). Surface sediment samples were stored both in pre-combusted glass jars with solventrinsed Teflon liners for organic analysis, and in acid washed polyethylene jars for trace metal analysis. Samples were placed on ice in the field, transferred to a freezer at 10 C and kept frozen until analysis. All were analyzed for bulk sediment characteristics such as grain size distribution (% sand, silt and clay), % organic matter (% OM), and C/N, PCBs, pesticides and trace metals. A pre-selected number of samples were submitted for analysis of petroleum hydrocarbons, PAHs and coprostanol. 2.2. Bulk sediment characteristics Complete results and methods of bulk sediment analyses have been reported elsewhere (Berger, 1996).
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Briefly, sediment grain size distribution was determined by wet sieve and hydrometer analysis (Table 1). 2.3. Trace organic analyses Sediments for organic analysis were subjected to two procedures, for chlorinated hydrocarbons (PCBs and pesticides), and for petroleum hydrocarbons, PAHs and coprostanol (see Table 2). Sample preparation, extraction and analysis of PCBs and pesticides have been published elsewhere (Lauenstein and Cantillo, 1998; Sericano et al., 1990; Wade et al., 1988). Briefly, wet sediments (20–40 g) were chemically dried with anhydrous sodium sulfate, spiked with the appropriate surrogate standards (Di-bromo-octafluoro-biphenyl (DBOFB), PCB 103, and PCB 198) and soxhlet extracted with methylene chloride (16 h). The concentrated organic extracts were then purified using a Table 1 Bulk sediment parameters Site No.
% Clay
% Silt
% Sand
% OMa
C/N
51 53 55 59 61 64 67 70 73 75 77 80 83 87 91
27 41 26 43 15 18 57 n.a. 34 22 16 7 0 33 n.a.
66 35 55 57 40 44 27 n.a. 63 61 14 50 1 67 n.a.
7 24 19 0 45 38 16 n.a. 3 17 70 43 99 0 n.a.
0.81 0.74 0.97 1.47 0.38 1.14 0.53 1.21 1.22 0.83 1.73 0.45 n.d. 1.56 1.02
12.3 11.9 11.8 11.9 9.6 14.0 9.4 11.2 10.4 10.7 12.1 8.3 10 11.2 8.6
a % OM=% organic matter. n.a.=not analyzed.
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mixed bed silica–alumina column (20g, 5% deactivation and 10 g 1% deactivation respectively) to isolate the aromatic fraction containing the chlorinated pesticides and PCBs from other components of the sample. After chromatographic cleanup, the sample extracts were concentrated to a final volume of 1 ml hexane using a combination of a water bath and a stream of purified nitrogen and, upon addition of the appropriate recovery standard (tetrachloro-m-xylene), analyzed by gas chromatography with electron capture detection (GC/ECD). Quantitation of the PCBs and chlorinated pesticides was performed on a Hewlett-Packard 5890 GC fitted with a DB5-M capillary column (30 m, 0.25 mm id, 0.25 mm film thickness; J&W, Folsom, California) using helium as a carrier gas at a head pressure of 25 psi. Quantitative results were based upon comparison with PCB 103 as a surrogate standard, using second order calibration curves constructed from authentic standards at five concentrations ranging from 5 to 200 pg/ul. Quantification of the pesticides are reported as total concentrations representing the summation of a- and g-chlordane, cis- and trans-nonachlor, heptachlor and heptachlor epoxide for total chlordanes and the o,p- and p,p- isomers of DDE, DDD, and DDT for total DDTs. QA/QC Samples included blanks, fortified blanks and samples, as well as the analysis of reference materials (NIST 1941a—Organics in marine sediments). Samples selected for the analysis of petroleum hydrocarbons, PAHs and coprostanol were freeze dried and Soxhlet extracted (24 h) with methylene chloride (Optima, Fisher). The extract was dried in vacuo (35 C) and the solvent exchanged to hexane. The extract was then fractionated by silica gel column chromatography as described elsewhere (Simoneit et al., 2000). Identification of the analytes was based on comparison of their retention times with those of authentic standards and by interpretation of mass spectra. Quantitative results were based upon comparison of analyte peak areas with
Table 2 Concentrations of anthropogenic organic compounds in sediments from Montego Baya Station No. Location
55 Montego Port
Parameter Chlordanes DDTs Dieldrin PCBs
0.4 1.45 0.27 49
PAHs UCM Carbon Preference Index (CPI) Hopanes Coprostanol a
n.a. n.a. n.a. n.a. n.a
All concentrations given in mg/kg of dry sediment. n.a.=not analyzed.
61 Pies River
0.38 1.5 0.24 0.76 21 69816 3.1 154 5.4
64 Montego River
0.92 1.46 1.66 5.7 158 19231 14 486 256
67 South Gully
75 Montego Bay
0.62 1.9 0.52 2.3
0.22 0.93 1 3.7
0.97 1158 3 349 1126
22 10904 6 112 8.8
77 North Gully
8.9 23 6.13 73 358 143841 2.6 5758 1610
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nologies Inc., Omaha, NE). Instrument configuration and general experimental conditions have been reported previously (Cai et al., 2000). Mercury was analyzed by atomic fluorescence spectroscopy as described by Jones et al. (1995).
those of the quantification standards (i.e. squalane for the aliphatic hydrocarbons and coprostanol, and perdeuterated PAHs for the PAHs). A response factor of one was assumed for the aliphatic hydrocarbons and coprostanol, thus the data for these compounds should be taken as semi-quantitative. Qualitative and quantitative determinations were performed by GC/MS on a Hewlett-Packard 5971 GC/MS fitted with a DB5-MS capillary column (25 m, 0.22 mm id, 0.25 mm film thickness; J&W, Folsom, California). Aliphatic hydrocarbons and coprostanol were analyzed running the MS system in the electron impact (EI) mode (ionization energy 70 eV). The PAHs were determined by selected ion monitoring (SIM).
3. Results and discussion 3.1. Bulk sediment characteristics In Montego Bay, sediment grain size and organic carbon and nitrogen contents were consistent with the geographical location and potential supply of particulate matter derived from riverine inputs. Highest organic matter and nitrogen concentrations were observed along the Montego River plume, through the central section of the bay. Excluding the North Gully site (77) the organic matter content correlated well with the sediment particle size distribution, where higher %OM was observed for sites with higher silt and clay content (see Table 1; r2=0.72, n=15). This suggests a strong influence of river-borne, particle-associated pollutant transport to the bay, following deposition along the river plume. Physical sorting, distribution and deposition of particulate matter (and associated pollutants) within the bay will be strongly dependent on water circulation. In the generally low energy environment of Montego Bay the particles essentially serve as tracers of water movement, and can provide an indication of long-term depositional patterns in surface sediments. Accordingly, the observed sediment grain-size distribution patterns are in agreement with a reported hydrodynamic study of the bay (Berger, 1996) which indicates that water enters the bay from the north along the coast and moves landward towards the mouth of the Montego River. Return of
2.4. Trace metal analysis Ten metals were selected for analysis in sediments (Table 3). Samples were digested using CEM (MARS5) Microwave Digestion System and the analyses were performed by ICP-MS. Briefly, sediment samples (0.2 g dry weight basis) were placed in microwave digestion vessels. After adding concentrated HNO3 (10 mL), the vessels were sealed and the samples were digested (15 min) following a standard operating procedure (SOP, 2000), which was based on the EPA method 3051. After digestion, the samples were quantitatively transferred to 100-ml volumetric flasks and diluted to the mark with distilled, deionized water. After the particulates had settled, 2 ml of the clear solution was placed in a 10-ml plastic test tube and diluted to 10 ml with water. Internal standards (Y, Sc, and In, 50 ml, 10 ppm) were added, thoroughly mixed, and the samples were ready for ICP/ MS analysis. The ICP-MS instrument used for metal analysis was Model HP 4500 plus (Hewlett-Packard Co., Wilmington, DE) equipped with a Babington-type nebulizer and an ASX-500 autosampler (Cetac Tech-
Table 3 Metal concentrations (mg/kg) in sediments from Montego Bay, Jamaica Sitea
51
53
55
59
61
64
70
73
75
77
80
83
87
92
Metal V Cr Co Ni Cu Zn As Cd Pb Hg
26.5 13.4 2.8 7.7 17.7 21.4 6.02 n.d.b 6.4 n.a.c
71.2 28.7 9.9 20.5 49.7 67.0 5.7 n.d. 19.4 n.a.
52.5 22.0 7.5 15.8 41.3 57.7 7.03 n.d. 20.2 0.30
61.3 20.9 10.1 16.3 42.2 48.6 5.8 n.d. 15.2 0.17
112 20.7 13.6 13.3 30.4 53.0 4.02 n.d. 15.5 n.a.
78.1 24.0 13.6 20.6 62.3 68.3 4.3 n.d. 26.5 n.a.
72.8 24.2 15.5 23.3 73.8 67.2 4.7 n.d. 18.5 0.30
80.6 21.8 15.5 21.0 73.1 74.5 4.5 10.0 21.6 n.a.
96.0 27.0 16.1 23.7 73.6 71.5 3.6 n.d. 24.2 0.17
30.6 48.0 4.8 20.4 27.5 147 3.4 0.86 185 0.29
6.6 5.0 0.68 3.7 3.5 7.9 1.4 n.d. 6.8 n.a.
12.1 7.9 1.08 5.2 6.4 13.5 1.5 n.d. 8.1 0.05
71.8 21.0 15.3 20.1 56.7 66.4 4.9 n.d. 28.2 0.09
82.0 28.3 15.0 23.9 61.8 70.0 6.2 n.d. 31.1 n.a.
a b c
Site 67 n.a. n.d.=not detected. n.a.=not analyzed.
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water to the open sea appears to be along the central section of the bay along the river plume, and along the southwest coastal section. While sediments along the northeast coast consist predominantly of sand, along the central and southwest coast silts and clays predominate. While nutrient concentrations and other water-quality patterns were found to reflect rapid flushing of the bay waters, dissolved nitrogen and phosphorus concentrations were reported to be greatest at sites influenced by the river plume and the gullies (Berger, 1996), suggesting that these are the most likely sources of nutrient loading to the bay. In agreement with this, the same study reports highest particulate organic carbon (POC) concentrations measured at the mouths of the gullies and the river, where the POC load undergoes rapid dilution, sedimentation and/or is flushed out to sea. The distribution of sediment and %OM in the bay suggests that a significant portion of this POC and its associated pollutant load may become incorporated in the bay’s sediments. Regarding the source of sedimentary OM in the bay, C/N ratios were found to range from 8 to 15, and are in the same range as those reported for other coastal embayments (e.g. Eganhouse and Sherblom, 2001). While C/N ratios of 6–8 are typical for marinederived OM, terrestrial OM usually results in C/N ratios above 12 (e.g. Jaffe´ et al., 2001). Based on this, the sedimentary OM in Montego Bay contains a significant terrestrial signal, most likely derived from runoff and particularly from OM introduced by the gullies and the river, since two of the most elevated C/N values were found at stations 77 and 64 (North Gully and river mouth respectively). 3.2. Organic contaminant distribution The aliphatic hydrocarbon fraction isolated from the sediment extracts showed the presence of a homologous series of n-alkanes ranging from C15 to C35. In all cases,
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the most abundant homologues were the high molecular weight n-alkanes with 29, 31 and 33 carbon numbers (Cmax=31), indicative of higher plant sources (Colombo et al., 1989). Although present, none of the samples analyzed showed the predominance or significant abundance of the C17 homologue, an indicator of planktonicderived OM (e.g Jaffe´ et al., 2001), suggesting that marine organisms are not a significant contributor to the sedimentary OM pool in Montego Bay. The rapid flushing of bay waters and associated nutrients may prevent the occurrence of algal blooms that would be significant enough to affect the sedimentary OM signal of the samples analyzed. This is in agreement with a mean C/N value of 11.2 for this sub-set of samples. Although the n-alkane distribution is strongly influenced by higher plant derived compounds, an anthropogenic OM input is also clear in these samples. Fig. 2 shows a chromatogram of the aliphatic hydrocarbon fraction of sample 77 (North Gully). While the higher plant derived n-alkane homologues C27, C29, C31 and C33 dominate the distribution, a significant contribution of an unresolved complex mixture (UCM) of hydrocarbons is clearly present, and this is typical of OM inputs from fossil fuels and/or residual crankcase oil (Farrington, 1980; Volkman et al., 1997). The UCM is a commonly observed feature in anthropogenically impacted coastal areas (Eganhouse and Sherblom, 2001 and references therein; Jaffe´ et al., 1995; Jaffe´ et al., 1998). UCM concentrations were particularly high at the site closest to the river mouth and at the North Gully (sites 64 and 77; see Table 2). In addition, the lower molecular weight alkane distribution (< C25) does not show an odd/even carbon number preference as would be observed for many biomass-derived materials. Instead, there does not seem to be any carbon preference in this carbon range, also suggesting contributions from fossil fuels. While the carbon preference index (CPI) of the higher molecular weight homologues
Fig. 2. Ion chromatogram (m/z=57) for the aliphatic hydrocarbon fraction at the North Gully station (77). Main n-alkanes with carbon number are indicated as well as the presence of Pristane (Pr), Phytane (Ph), the unresolved complex mixture (UCM), and the internal standard (I.S.).
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(> C25) is commonly used to assess the presence of fossil fuel hydrocarbons in environmental samples (e.g. Eganhouse and Sherblom, 2001) its values are relatively high (about 3–6; see Table 2) even for samples with an elevated UCM. This may be due to the fact that the samples contain, in addition to the anthropogenic hydrocarbons, a significant amount of higher plant cuticular wax-derived alkanes (see above), which will affect the CPI values (e.g. Nishigima et al., 2001). However, the lowest CPI values were again observed at the river site and the North Gully (sites 64 and 77), which seem to be the most impacted by anthropogenic activities in the area. The presence of a homologous series of triterpenoids, namely the 17a,21b, 22R&S hopanes (see Fig. 3 and Table 2), commonly used to trace petroleum hydrocarbon sources in the environment (e.g. Hostettler et al., 1992; Riesebrough et al., 1983), confirms that there are fossil fuel-derived OM inputs to Montego Bay. The 17a,21b homohopanes have a 22S/22S+22R ratio of about 0.6, which implies a mature source, such as crude oil (Peters and Moldowan, 1993). As shown in Fig. 3, in addition to the hopanes, a series of tri- and tetra-cyclic triterpenoids were also observed. These included a homologous series of tricyclic hopanes (C23 as the most abundant homologue) as well as the trisnorhopanes (Ts and Tm; Peters and Moldowan, 1993). It is likely that these fossil fuel derived hydrocarbons are introduced into the bay through street runoff and illegal dumping of petroleum products and used crankcase oil via the gullies and the river, and/or through contamination caused by commercial and recreational shipping activities and the oil storage facility in the bay area. These compounds were particularly abundant at the North Gully station (77). Polycyclic aromatic hydrocarbons (PAHs) are pollutants that are ubiquitous in aquatic environments and a product of combustion and fossil fuels (Laflamme and Hites, 1978) as well as from oil pollution (e.g.
Nishigima et al., 2001 and references therein). Total PAH concentrations for some selected samples are shown in Table 2. As for the aliphatic hydrocarbons, the PAHs show elevated concentrations at the mouth of the river (site 64) and at the North Gully (site 77). PAH concentrations at the sites corresponding to the southcentral and southern bay were one order of magnitude lower, probably as a result of dilution. In comparison, South Gully (site 67) concentrations were surprisingly low. This could be due to differences in the pollutant sources and input levels between the two gullies, but also due to the lower%OM at the South Gully station. Total PAH concentrations for the analyzed samples ranged from 0.97 to 358 mg/kg. Based on literature reports, such levels are typical for the lower end of the concentration range for industrial and port areas (e.g. Nishigima et al., 2001 and references therein) and well below the low effect range (ERLs), threshold effect levels (TELs), and probable effect levels (PELs) reported by Long et al. (1995) and Mac Donald et al. (1996) of 4022 mg/kg, 1684 mg/kg, and 6676 mg/kg respectively. Concentrations of chlorinated hydrocarbons such as PCBs and pesticides were determined in all of the samples. Table 2 reports only the sites with concentrations significantly above background values. The only pesticides that were detected in significant amounts were those of the chlordane and DDT series (see Table 2). The concentrations of pesticides and PCBs were relatively evenly distributed throughout the analyzed sites with the exception of the North Gully (site 77) where concentrations were 1–2 orders of magnitude higher than at the rest of the sites. Total PCB concentrations in Montego Bay ranged from 0.76 to 73 mg/kg, which falls in the low to intermediate level compared to other anthropogenically impacted coastal bays and ports such as Boston Harbor (Eganhouse and Sherblom, 2001; about 10–800 mg/kg). Excluding the North Gully site,
Fig. 3. Ion chromatogram (m/z=191) for the aliphatic hydrocarbon fraction at the North Gully station (77). Hopanes are indicated based on carbon number (C29 to C35).
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the river mouth (site 64) had higher levels of PCBs and possibly chlordanes than the other bay sites, while the port (site 55) showed elevated levels of PCBs probably as a result of commercial shipping/port activities. The North Gully, however, seems to be the dominant source of chlorinated hydrocarbons to the bay. Considering that this site has 70% sand content, the silt/clay fraction is highly enriched in chlorinated hydrocarbons and can act as a potential point source for these compounds within the bay. The total PCB levels observed at this station (73 mg/kg) considerably exceed both the ERL of 22.7 mg/kg total PCBs used by Long et al. (1995) and the TEL criteria (21.6 mg/kg total PCBs) proposed by MacDonald et al. (1996) to quantify degradation of sediment quality in estuaries within the USA. Although the chlorinated pesticide levels found at Montego Port are not as elevated as at the north Gully, the PCB concentrations (49 mg/kg) also exceeded the ERL and TEL guidelines. Coprostanol has been widely used to trace sewage inputs to aquatic environments (Takada and Eganhouse, 1998 and references therein). The presence of coprostanol in Montego Bay sediments reflects the inputs of raw sewage to this environment. Greatest concentrations were observed at both gully sites (77 and 67), particularly at the North Gully, although the difference was in this case not as pronounced as for other contaminants (see Table 2). The levels at the gully sites were followed by the river mouth site (64), which was one order of magnitude lower, and the other two bay sites (61 and 75), which were 3 orders of magnitude lower. Coprostanol concentrations were within the low to middle range reported for other sewage-impacted coastal bays in the United States (Eganhouse and Sherblom, 2001 and references therein). While a sewage source from within the Montego River basin is likely (i.e. effluents from the WWTF), the bay sediments could be considerably influenced by sewage derived from the two gullies. High PCB concentrations at the North Gully site and elevated coprostanol levels suggest that a significant portion of the PCBs in the bay may be sewage-derived. Such a correlation has previously been suggested to exist in the Boston Harbor area (Eganhouse and Sherblom, 2001). In the case of Montego Bay, an exception may be the elevated PCB concentrations in the Port area, which are too far removed from the gully site, and most likely may have another anthropogenic source.
suspected pollutant sources such as the Montego River, the North and South gullies and the port area. In addition, these sites are influenced by incoming waters to the bay and therefore unlikely to be affected by entrained trace metals. On the contrary, and in agreement with the distribution of the organic pollutants in the Bay, the river plume sites and particularly the North Gully site (77) have generally much greater trace metal concentrations. For example, Cr, Pb and Zn (and potentially Cd) show highest concentrations at site 77. Although these metals also have higher than average concentrations at the river plume sites, these are much lower than at site 77. In the case of Cr and Pb, these metals also show higher than average concentrations at some of the central bay sites (75, 87 and 92), which are both in-line with site 77 through the predominant water circulation patterns for the bay, and may therefore be affected by particles transported from the North Gully outfall into the central and western side of the bay. Cd was not detected in the majority of the samples except at 77 and at surprisingly elevated levels at site 73. We have no explanation for this distribution. While metals such as Hg and As did not present a particular source-dependent distribution in the bay, Ni, Co, Cu and V seem to find their main source in the Montego River basin and are fairly concentrated along the river plume (sites 64, 70, 73, 75 and 87), and not as much at the mouth of the North Gully. However, these metals are also abundant in the port area (sites 53, 55 and 59) and other south-western locations (e.g. site 92). It is unclear why the concentrations of V were highest at the southern-most site (61), but there might potentially be a source of this metal in the Pies River catchment. Zn was also found to be somewhat more concentrated in the port and southwest sampling sites compared to the river plume sites. In comparison with data obtained from estuarine and coastal marine sediments of the southeastern United Sates (Windom et al., 1989), concentrations of most metals in Montego Bay, except for Zn and Pb, are within the range of those from the United Sates. Very high concentrations of Zn and Pb found at the North Gully (77), as for other pollutants, suggest a strong anthropogenic impact to this area. High concentrations of Zn and Pb often indicate inputs of anthropogenic toxicants and have been used in numerous surveys performed in US estuaries to assess environmental impacts (NOAA, 1998).
3.3. Trace metal distribution
4. Conclusions
Table 3 gives concentrations of 10 trace metals at a variety of sampling stations in Montego Bay. In all cases, trace metal concentrations were lowest at the two stations located on the north-eastern shore of the bay (sites 80 and 83). These sites are most remote from
The quality of bottom sediments of Montego Bay, is clearly affected by anthropogenic activities in the city, the port area and the drainage of the Montego River. While the North Gully seems to be the main point source of pollutants into the bay, both the port area and
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the river plume seem associated with the distribution of trace metals and organic compounds of anthropogenic origin. The predominantly southerly inflow into the bay, followed by an outflow to the southwest, allows particle-associated metals and organics to become distributed throughout the bay area. The Montego River may deposit such materials along its plume, in a northwestern direction from the river mouth. However, an apparent preferential accumulation of trace metals at site 92 seems to indicate particle transport into a more westerly direction of the river plume (possibly during low water discharge periods) and/or transport of resuspended particles from the port area into the bay. As to the nature of anthropogenic inputs into the Montego Bay area, both industrial (trace metals, PCBs and petroleum hydrocarbons), agricultural (pesticides) and sewage (coprostanol) sources were found to be important. The two gullies, particularly the North Gully, represent the most significant source of anthropogenically-derived inputs to the bay. High concentrations of raw sewage (as indicated by high coprostanol levels), street runoff (UCM, hopanes, PAHs and Pb), and industrial chemicals (PCBs, pesticides, Zn, Pb and Cr) are clearly introduced into Montego Bay through this means. With a few exceptions, such as the trace metals Co, Ni and Cu, the North Gully is the main pollution point source reported in this study. The environmental effects of sewage-derived waste-waters to Montego Bay are expected to improve after the completion of the new waste-water treatment facility in 2000 (samples reported in this study were collected prior to this date).
Acknowledgements The authors thank The Louis Berger Group, Inc. for assistance with sediment sampling and access to some bulk sediment data. Thanks also to the Southeast Environmental Research Center and the Department of Chemistry Advanced Mass Spectrometry Facility at FIU for providing instrument time. A.S. and A.F. thank FIU for student fellowships. SERC contribution 188.
References Berger, 1996. Montego Bay Environmental Monitoring Program. Final Report. Submitted to the US Agency for International Development. Louis Berger Group, Inc. Cai, Y., Georgiadis, M., Fourqurean, J.D., 2000. Determination of arsenic in seagrass using inductively coupled plasma mass spectrometry. Spectrochimica Acta, Part B 55, 1411–1422. Colombo, J.C., Pelletier, E., Brochu, C., Khalil, M., 1989. Determination of hydrocarbon sources using n-alkane and polyaromatic hydrocarbon distribution indexes. Case study: Rio de la Plata estu-
ary, Argentina. Environmental Science and Technology 23, 888– 894. Eganhouse, R.P., Sherblom, P.M., 2001. Anthropogenic organic contaminants in the effluent of a combined sewer overflow: impact on Boston Harbor. Marine Environmental Research 51, 51–74. Farrington, J.W., 1980. An overview of the biogeochemistry of fossil fuel hydrocarbons in the marine environment. In: Petrakis, L., Weiss, F.T. (Eds.), Petroleum in the Marine Environment, Advances in Chemistry Series 185. ACS, Washington, pp. 1–22. Hostettler, F.D., Rapp, J.B., Kvenvolden, K.A., 1992. Use of geochemical biomarkers in bottom sediments to track oil from a spill, San Fransisco Bay, California. Marine Pollution Bulletin 24, 15–20. Jaffe´, R., Leal, I., Alvarado, J., Gardinali, P.R., Sericano, J.L., 1995. Pollution effects of the Tuy River on the central Venezuelan coast: anthropogenic organic compounds and heavy metals in Tivela mactroidea. Marine Pollution Bulletin 30, 820–825. Jaffe´, R., Leal, I., Alvarado, J., Gardinali, P.R., Sericano, J.L., 1998. Baseline study on the levels of organic pollutants and heavy metals in bivalves from the Morrocoy National Park, Venezuela. Marine Pollution Bulletin 36, 925–929. Jaffe´, R., Mead, R., Hernandez, M.E., Peralba, M.C., DiGuida, O.A., 2001. Origin and transport of sedimentary organic matter in two subtropical estuaries: a comparative biomarker-based study. Organic Geochemistry 32, 507–526. Jones, R.D., Jacobson, M.E., Jaffe´, R., West-Thomas, J., Arfstrom, C., Alli, A., 1995. Method development and sample processing of water, soil, and tissue for the analysis of total and organic mercury by cold vapor atomic fluorescence spectrometry. Water, Air, and Soil Pollution 80, 1285–1294. Laflamme, R.E., Hites, R.A., 1978. The global distribution of polycyclic aromatic hydrocarbons in recent sediments. Geochimica et Cosmochimica Acta 42, 289–303. Lauenstein, G., Cantillo, A., 1998. Sampling and analytical methods of the National Status and Trends Program Mussel Watch Project: 1993–1996 Update. NOAA Technical Memorandum NOS ORCA 130. National Oceanic and Atmospheric Administration. Silver Spring, MD. Long, E.R., MacDonald, D.D., Smith, S.L., Calder, F.D., 1995. Incidence of adverse biological effects within ranges of chemical concentrations in marine and estuarine sediments. Environmental Management 19, 81–97. MacDonald, D.D., Carr, R.S., Calder, F.D., Long, E.R., Ingersoll, C.G., 1996. Development and evaluation of sediment quality guidelines for Florida coastal waters. Ecotoxicology 5, 253–278. Nishigima, F.N., Weber, R.R., Bicego, M.C., 2001. Aliphatic and aromatic hydrocarbons in sediments of Santos and Cananeia, SP, Brazil. Marine Pollution Bulletin 42, 1064–1072. NOAA Technical Memorandum, National Status and Trends Program for Marine Environmental Quality., 1998. Magnitude and extent of chemical contamination and toxicity in sediments of Biscayne Bay and vicinity. Review Draft. Peters, K.E., Moldowan, J.M., 1993. The Biomarker Guide: Interpreting Molecular Fossils in Petroleum and Ancient Sediments. Prentice-Hall Inc, Englewood Cliffs, New Jersey. Riesebrough, R.W., de Lappe, B.W., Walker, W., Simoneit, B.R.T., Grimalt, J., Albaiges, J., Garcia Regueiro, J.A., Ballester Nolla, A., Fernandez, M.M., 1983. Application of the mussel watch concept in studies of the distribution of hydrocarbons in the coastal zone of the Ebro Delta. Marine Pollution Bulletin 14, 181–187. Sericano, J.L., Atlas, E.L., Wade, T.L., Brooks, J.M., 1990. NOAA’s Status and Trends Mussel Watch Program: chlorinated pesticides and PCBs in oysters (Crassostrea virginica) and sediments from the Gulf of Mexico, 1986-1987. Marine Environmental Research 29, 161–203. Simoneit, B.R.T., Rogge, W.F., Lang, Q., Jaffe´, R., 2000. Molecular characterization of smoke from campfire burning of pine wood (Pinus elliottii). Chemosphere-Global Change Science 2, 107–122.
R. Jaffe´ et al. / Environmental Pollution 123 (2003) 291–299 Standard Operation Procedures (SOP-2000-I-001.1), 2000. Microwave assisted acid digestion of soil, sediments, tissue, and waste samples for total recoverable metal analysis. Southeast Environmental Research Center (SERC), Florida International University. Takada, H., Eganhouse, R.P., 1998. Molecular markers of anthropogenic waste. In: Meyers, R.A. (Ed.), Encyclopedia of Environmental Analysis and Remediation. John Wiley, New York, pp. 2883–2940. Volkman, J.K., Revill, A.T., Murray, A.P., 1997. Application of biomarkers for identifying sources of natural and pollutant hydrocarbons in aquatic environments. In: Eganhouse, R.P. (Ed.),
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Molecular Markers in Environmental Geochemistry. ACS Symposium Series 671, Washington, pp. 110–132. Wade, T.L., Atlas, E.L., Brooks, J.M., Kennicutt III, M.C., Fox, R.G., Sericano, J., Garcia, B., DeFreitas, D., 1988. NOAA Gulf of Mexico Status and Trends Program: trace organic contaminant distribution in sediment and oysters. Estuaries 11, 171–179. Windom, H.L., Schropp, S.J., Calder, F.D., Ryan, J.D., Smith jr, R.G., Burney, L.C., Lewis, F.G., Rawlinson, C.H., 1995. Natural trace metal concentrations in estuarine and coastal marine sediments of the southeastern United States. Environmental Science and Technology 23, 314–320.
Organic compounds and trace metals of anthropogenic origin in sediments from Montego Bay, Jamaica: assessment of sources and distribution pathways Rudolf Jaffe´a,b,*, Piero R. Gardinalia,b, Yong Caia,b, Aaron Sudburrya, Adolfo Fernandeza,c, Bernward J. Hayd a
Environmental Geochemistry Laboratory, Southeast Environmental Research Center, Florida International University, Miami, FL 33199, USA b Department of Chemistry, Florida International University, Miami, FL 33199, USA c Department of Environmental Studies, Florida International University, Miami, Fl 33199, USA d The Louis Berger Group, Inc., 75 Second Avenue, Suite 700, Needham, MA 02494, USA Received 4 June 2002; accepted 13 September 2002
‘‘Capsule’’: Sources and distribution pathways were identified. Abstract Surface sediments throughout Montego Bay, Jamaica were collected in 1995 and analyzed for their trace metal and trace organic contaminant content. A variety of trace metals, petroleum hydrocarbons, polycyclic aromatic hydrocarbons, coprostanol as well as chlorinated hydrocarbons such as pesticides and polychlorinated biphenyls were detected and provide evidence for several anthropogenic inputs to the bay. Two main sources of these chemicals are the Montego River and the North Gully, the latter being more significant. Particle-associated pollutants were found to be distributed along the Montego River plume, as well as being transported by the prevailing water currents to the South-Western sections of the bay, probably through re-suspension of enriched fine sediments from the North Gully outfall area. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: Trace metals; Hydrocarbons; Pesticides; PCBs; Sewage; Sediments; Montego Bay; Jamaica
1. Introduction The City of Montego Bay is the second largest city in Jamaica (population about 100,000). The center of the city is located around a shallow embayment, Montego Bay (Fig. 1), which includes an engineered port basin to the southwest that serves commercial shipping and large cruise ships. Montego Bay is an open bay, approximately 2 km wide and 1.5 km long at its entrance. Water depths gradually increase from shore to the open sea. At its mouth, the Bay is about 50–100 m deep, whilst the port is only 10 m in depth, and is surrounded by urban and some industrial developments, including an oil storage facility. Point source discharges from * Corresponding author. Tel.: +1-305-348-24-56; fax: +305-34840-96. E-mail address: jaffer@fiu.edu (R. Jaffe´).
these facilities are largely limited to stormwater runoff. Sediments in the bay consist of mainly sand and silt with greater concentrations of silt at the mouth of the Montego River (Berger, 1996), which is the largest freshwater body entering the bay. Otherwise, there are several small drains and gullies. The river extends approximately 10 km inland, and has a mean annual discharge rate of about 2 m3 s 1 (Berger, 1996). Highest discharge occurs during the two rainy seasons in June and in October/November. The flow during a 100-year rainstorm has been estimated at 720 m3 s 1 (Berger, 1996). The watershed is rural with undeveloped woodlands, small towns, pastures, banana and sugar cane plantations, and other agricultural fields. The river does receive effluents near its mouth from the water treatment facility of the City of Montego Bay (0.12 m3 s 1). This has increased since 2000 due to the construction of a new plant along with an expanded sewage collection
0269-7491/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(02)00368-8
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Fig. 1. Map of Montego Bay indicating sample locations. For convenience, the site numbering system used was the same as in Berger (1996). General water circulation pattern is indicated by arrow.
system. In addition to treated sewage, the Bay receives raw sewage and street runoff through small drains and gullies. Our purpose was to assess existing environmental conditions of Montego Bay through detailed chemical analyses of its sediments. Between 1992 and 1996 Louis Berger Group, Inc. was contracted by the US Agency for International Development to conduct an extensive monitoring study for the coastal waters and surrounding areas of Montego Bay in preparation for the construction of the new wastewater treatment facility. This study provided an opportunity to evaluate additionally the environmental conditions of the sediments in the Bay. Potential contaminants were analyzed in sediment grab samples from the Bay, including trace metals, polychlorinated biphenyls (PCBs), petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), sewage markers such as coprostanol and chlorinated pesticides in an effort to evaluate different pollution sources to the Bay. To the best of our knowledge this is the first report on the detailed characterization of sedimentary organic contaminants in coastal waters of Jamaica.
2. Methods 2.1. Sampling Sediment grab samples were collected in 1995 from 16 stations across the Bay (Fig. 1) using an Ekman Dredge (Wildco, Michigan). Surface sediment samples were stored both in pre-combusted glass jars with solventrinsed Teflon liners for organic analysis, and in acid washed polyethylene jars for trace metal analysis. Samples were placed on ice in the field, transferred to a freezer at 10 C and kept frozen until analysis. All were analyzed for bulk sediment characteristics such as grain size distribution (% sand, silt and clay), % organic matter (% OM), and C/N, PCBs, pesticides and trace metals. A pre-selected number of samples were submitted for analysis of petroleum hydrocarbons, PAHs and coprostanol. 2.2. Bulk sediment characteristics Complete results and methods of bulk sediment analyses have been reported elsewhere (Berger, 1996).
R. Jaffe´ et al. / Environmental Pollution 123 (2003) 291–299
Briefly, sediment grain size distribution was determined by wet sieve and hydrometer analysis (Table 1). 2.3. Trace organic analyses Sediments for organic analysis were subjected to two procedures, for chlorinated hydrocarbons (PCBs and pesticides), and for petroleum hydrocarbons, PAHs and coprostanol (see Table 2). Sample preparation, extraction and analysis of PCBs and pesticides have been published elsewhere (Lauenstein and Cantillo, 1998; Sericano et al., 1990; Wade et al., 1988). Briefly, wet sediments (20–40 g) were chemically dried with anhydrous sodium sulfate, spiked with the appropriate surrogate standards (Di-bromo-octafluoro-biphenyl (DBOFB), PCB 103, and PCB 198) and soxhlet extracted with methylene chloride (16 h). The concentrated organic extracts were then purified using a Table 1 Bulk sediment parameters Site No.
% Clay
% Silt
% Sand
% OMa
C/N
51 53 55 59 61 64 67 70 73 75 77 80 83 87 91
27 41 26 43 15 18 57 n.a. 34 22 16 7 0 33 n.a.
66 35 55 57 40 44 27 n.a. 63 61 14 50 1 67 n.a.
7 24 19 0 45 38 16 n.a. 3 17 70 43 99 0 n.a.
0.81 0.74 0.97 1.47 0.38 1.14 0.53 1.21 1.22 0.83 1.73 0.45 n.d. 1.56 1.02
12.3 11.9 11.8 11.9 9.6 14.0 9.4 11.2 10.4 10.7 12.1 8.3 10 11.2 8.6
a % OM=% organic matter. n.a.=not analyzed.
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mixed bed silica–alumina column (20g, 5% deactivation and 10 g 1% deactivation respectively) to isolate the aromatic fraction containing the chlorinated pesticides and PCBs from other components of the sample. After chromatographic cleanup, the sample extracts were concentrated to a final volume of 1 ml hexane using a combination of a water bath and a stream of purified nitrogen and, upon addition of the appropriate recovery standard (tetrachloro-m-xylene), analyzed by gas chromatography with electron capture detection (GC/ECD). Quantitation of the PCBs and chlorinated pesticides was performed on a Hewlett-Packard 5890 GC fitted with a DB5-M capillary column (30 m, 0.25 mm id, 0.25 mm film thickness; J&W, Folsom, California) using helium as a carrier gas at a head pressure of 25 psi. Quantitative results were based upon comparison with PCB 103 as a surrogate standard, using second order calibration curves constructed from authentic standards at five concentrations ranging from 5 to 200 pg/ul. Quantification of the pesticides are reported as total concentrations representing the summation of a- and g-chlordane, cis- and trans-nonachlor, heptachlor and heptachlor epoxide for total chlordanes and the o,p- and p,p- isomers of DDE, DDD, and DDT for total DDTs. QA/QC Samples included blanks, fortified blanks and samples, as well as the analysis of reference materials (NIST 1941a—Organics in marine sediments). Samples selected for the analysis of petroleum hydrocarbons, PAHs and coprostanol were freeze dried and Soxhlet extracted (24 h) with methylene chloride (Optima, Fisher). The extract was dried in vacuo (35 C) and the solvent exchanged to hexane. The extract was then fractionated by silica gel column chromatography as described elsewhere (Simoneit et al., 2000). Identification of the analytes was based on comparison of their retention times with those of authentic standards and by interpretation of mass spectra. Quantitative results were based upon comparison of analyte peak areas with
Table 2 Concentrations of anthropogenic organic compounds in sediments from Montego Baya Station No. Location
55 Montego Port
Parameter Chlordanes DDTs Dieldrin PCBs
0.4 1.45 0.27 49
PAHs UCM Carbon Preference Index (CPI) Hopanes Coprostanol a
n.a. n.a. n.a. n.a. n.a
All concentrations given in mg/kg of dry sediment. n.a.=not analyzed.
61 Pies River
0.38 1.5 0.24 0.76 21 69816 3.1 154 5.4
64 Montego River
0.92 1.46 1.66 5.7 158 19231 14 486 256
67 South Gully
75 Montego Bay
0.62 1.9 0.52 2.3
0.22 0.93 1 3.7
0.97 1158 3 349 1126
22 10904 6 112 8.8
77 North Gully
8.9 23 6.13 73 358 143841 2.6 5758 1610
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nologies Inc., Omaha, NE). Instrument configuration and general experimental conditions have been reported previously (Cai et al., 2000). Mercury was analyzed by atomic fluorescence spectroscopy as described by Jones et al. (1995).
those of the quantification standards (i.e. squalane for the aliphatic hydrocarbons and coprostanol, and perdeuterated PAHs for the PAHs). A response factor of one was assumed for the aliphatic hydrocarbons and coprostanol, thus the data for these compounds should be taken as semi-quantitative. Qualitative and quantitative determinations were performed by GC/MS on a Hewlett-Packard 5971 GC/MS fitted with a DB5-MS capillary column (25 m, 0.22 mm id, 0.25 mm film thickness; J&W, Folsom, California). Aliphatic hydrocarbons and coprostanol were analyzed running the MS system in the electron impact (EI) mode (ionization energy 70 eV). The PAHs were determined by selected ion monitoring (SIM).
3. Results and discussion 3.1. Bulk sediment characteristics In Montego Bay, sediment grain size and organic carbon and nitrogen contents were consistent with the geographical location and potential supply of particulate matter derived from riverine inputs. Highest organic matter and nitrogen concentrations were observed along the Montego River plume, through the central section of the bay. Excluding the North Gully site (77) the organic matter content correlated well with the sediment particle size distribution, where higher %OM was observed for sites with higher silt and clay content (see Table 1; r2=0.72, n=15). This suggests a strong influence of river-borne, particle-associated pollutant transport to the bay, following deposition along the river plume. Physical sorting, distribution and deposition of particulate matter (and associated pollutants) within the bay will be strongly dependent on water circulation. In the generally low energy environment of Montego Bay the particles essentially serve as tracers of water movement, and can provide an indication of long-term depositional patterns in surface sediments. Accordingly, the observed sediment grain-size distribution patterns are in agreement with a reported hydrodynamic study of the bay (Berger, 1996) which indicates that water enters the bay from the north along the coast and moves landward towards the mouth of the Montego River. Return of
2.4. Trace metal analysis Ten metals were selected for analysis in sediments (Table 3). Samples were digested using CEM (MARS5) Microwave Digestion System and the analyses were performed by ICP-MS. Briefly, sediment samples (0.2 g dry weight basis) were placed in microwave digestion vessels. After adding concentrated HNO3 (10 mL), the vessels were sealed and the samples were digested (15 min) following a standard operating procedure (SOP, 2000), which was based on the EPA method 3051. After digestion, the samples were quantitatively transferred to 100-ml volumetric flasks and diluted to the mark with distilled, deionized water. After the particulates had settled, 2 ml of the clear solution was placed in a 10-ml plastic test tube and diluted to 10 ml with water. Internal standards (Y, Sc, and In, 50 ml, 10 ppm) were added, thoroughly mixed, and the samples were ready for ICP/ MS analysis. The ICP-MS instrument used for metal analysis was Model HP 4500 plus (Hewlett-Packard Co., Wilmington, DE) equipped with a Babington-type nebulizer and an ASX-500 autosampler (Cetac Tech-
Table 3 Metal concentrations (mg/kg) in sediments from Montego Bay, Jamaica Sitea
51
53
55
59
61
64
70
73
75
77
80
83
87
92
Metal V Cr Co Ni Cu Zn As Cd Pb Hg
26.5 13.4 2.8 7.7 17.7 21.4 6.02 n.d.b 6.4 n.a.c
71.2 28.7 9.9 20.5 49.7 67.0 5.7 n.d. 19.4 n.a.
52.5 22.0 7.5 15.8 41.3 57.7 7.03 n.d. 20.2 0.30
61.3 20.9 10.1 16.3 42.2 48.6 5.8 n.d. 15.2 0.17
112 20.7 13.6 13.3 30.4 53.0 4.02 n.d. 15.5 n.a.
78.1 24.0 13.6 20.6 62.3 68.3 4.3 n.d. 26.5 n.a.
72.8 24.2 15.5 23.3 73.8 67.2 4.7 n.d. 18.5 0.30
80.6 21.8 15.5 21.0 73.1 74.5 4.5 10.0 21.6 n.a.
96.0 27.0 16.1 23.7 73.6 71.5 3.6 n.d. 24.2 0.17
30.6 48.0 4.8 20.4 27.5 147 3.4 0.86 185 0.29
6.6 5.0 0.68 3.7 3.5 7.9 1.4 n.d. 6.8 n.a.
12.1 7.9 1.08 5.2 6.4 13.5 1.5 n.d. 8.1 0.05
71.8 21.0 15.3 20.1 56.7 66.4 4.9 n.d. 28.2 0.09
82.0 28.3 15.0 23.9 61.8 70.0 6.2 n.d. 31.1 n.a.
a b c
Site 67 n.a. n.d.=not detected. n.a.=not analyzed.
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water to the open sea appears to be along the central section of the bay along the river plume, and along the southwest coastal section. While sediments along the northeast coast consist predominantly of sand, along the central and southwest coast silts and clays predominate. While nutrient concentrations and other water-quality patterns were found to reflect rapid flushing of the bay waters, dissolved nitrogen and phosphorus concentrations were reported to be greatest at sites influenced by the river plume and the gullies (Berger, 1996), suggesting that these are the most likely sources of nutrient loading to the bay. In agreement with this, the same study reports highest particulate organic carbon (POC) concentrations measured at the mouths of the gullies and the river, where the POC load undergoes rapid dilution, sedimentation and/or is flushed out to sea. The distribution of sediment and %OM in the bay suggests that a significant portion of this POC and its associated pollutant load may become incorporated in the bay’s sediments. Regarding the source of sedimentary OM in the bay, C/N ratios were found to range from 8 to 15, and are in the same range as those reported for other coastal embayments (e.g. Eganhouse and Sherblom, 2001). While C/N ratios of 6–8 are typical for marinederived OM, terrestrial OM usually results in C/N ratios above 12 (e.g. Jaffe´ et al., 2001). Based on this, the sedimentary OM in Montego Bay contains a significant terrestrial signal, most likely derived from runoff and particularly from OM introduced by the gullies and the river, since two of the most elevated C/N values were found at stations 77 and 64 (North Gully and river mouth respectively). 3.2. Organic contaminant distribution The aliphatic hydrocarbon fraction isolated from the sediment extracts showed the presence of a homologous series of n-alkanes ranging from C15 to C35. In all cases,
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the most abundant homologues were the high molecular weight n-alkanes with 29, 31 and 33 carbon numbers (Cmax=31), indicative of higher plant sources (Colombo et al., 1989). Although present, none of the samples analyzed showed the predominance or significant abundance of the C17 homologue, an indicator of planktonicderived OM (e.g Jaffe´ et al., 2001), suggesting that marine organisms are not a significant contributor to the sedimentary OM pool in Montego Bay. The rapid flushing of bay waters and associated nutrients may prevent the occurrence of algal blooms that would be significant enough to affect the sedimentary OM signal of the samples analyzed. This is in agreement with a mean C/N value of 11.2 for this sub-set of samples. Although the n-alkane distribution is strongly influenced by higher plant derived compounds, an anthropogenic OM input is also clear in these samples. Fig. 2 shows a chromatogram of the aliphatic hydrocarbon fraction of sample 77 (North Gully). While the higher plant derived n-alkane homologues C27, C29, C31 and C33 dominate the distribution, a significant contribution of an unresolved complex mixture (UCM) of hydrocarbons is clearly present, and this is typical of OM inputs from fossil fuels and/or residual crankcase oil (Farrington, 1980; Volkman et al., 1997). The UCM is a commonly observed feature in anthropogenically impacted coastal areas (Eganhouse and Sherblom, 2001 and references therein; Jaffe´ et al., 1995; Jaffe´ et al., 1998). UCM concentrations were particularly high at the site closest to the river mouth and at the North Gully (sites 64 and 77; see Table 2). In addition, the lower molecular weight alkane distribution (< C25) does not show an odd/even carbon number preference as would be observed for many biomass-derived materials. Instead, there does not seem to be any carbon preference in this carbon range, also suggesting contributions from fossil fuels. While the carbon preference index (CPI) of the higher molecular weight homologues
Fig. 2. Ion chromatogram (m/z=57) for the aliphatic hydrocarbon fraction at the North Gully station (77). Main n-alkanes with carbon number are indicated as well as the presence of Pristane (Pr), Phytane (Ph), the unresolved complex mixture (UCM), and the internal standard (I.S.).
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(> C25) is commonly used to assess the presence of fossil fuel hydrocarbons in environmental samples (e.g. Eganhouse and Sherblom, 2001) its values are relatively high (about 3–6; see Table 2) even for samples with an elevated UCM. This may be due to the fact that the samples contain, in addition to the anthropogenic hydrocarbons, a significant amount of higher plant cuticular wax-derived alkanes (see above), which will affect the CPI values (e.g. Nishigima et al., 2001). However, the lowest CPI values were again observed at the river site and the North Gully (sites 64 and 77), which seem to be the most impacted by anthropogenic activities in the area. The presence of a homologous series of triterpenoids, namely the 17a,21b, 22R&S hopanes (see Fig. 3 and Table 2), commonly used to trace petroleum hydrocarbon sources in the environment (e.g. Hostettler et al., 1992; Riesebrough et al., 1983), confirms that there are fossil fuel-derived OM inputs to Montego Bay. The 17a,21b homohopanes have a 22S/22S+22R ratio of about 0.6, which implies a mature source, such as crude oil (Peters and Moldowan, 1993). As shown in Fig. 3, in addition to the hopanes, a series of tri- and tetra-cyclic triterpenoids were also observed. These included a homologous series of tricyclic hopanes (C23 as the most abundant homologue) as well as the trisnorhopanes (Ts and Tm; Peters and Moldowan, 1993). It is likely that these fossil fuel derived hydrocarbons are introduced into the bay through street runoff and illegal dumping of petroleum products and used crankcase oil via the gullies and the river, and/or through contamination caused by commercial and recreational shipping activities and the oil storage facility in the bay area. These compounds were particularly abundant at the North Gully station (77). Polycyclic aromatic hydrocarbons (PAHs) are pollutants that are ubiquitous in aquatic environments and a product of combustion and fossil fuels (Laflamme and Hites, 1978) as well as from oil pollution (e.g.
Nishigima et al., 2001 and references therein). Total PAH concentrations for some selected samples are shown in Table 2. As for the aliphatic hydrocarbons, the PAHs show elevated concentrations at the mouth of the river (site 64) and at the North Gully (site 77). PAH concentrations at the sites corresponding to the southcentral and southern bay were one order of magnitude lower, probably as a result of dilution. In comparison, South Gully (site 67) concentrations were surprisingly low. This could be due to differences in the pollutant sources and input levels between the two gullies, but also due to the lower%OM at the South Gully station. Total PAH concentrations for the analyzed samples ranged from 0.97 to 358 mg/kg. Based on literature reports, such levels are typical for the lower end of the concentration range for industrial and port areas (e.g. Nishigima et al., 2001 and references therein) and well below the low effect range (ERLs), threshold effect levels (TELs), and probable effect levels (PELs) reported by Long et al. (1995) and Mac Donald et al. (1996) of 4022 mg/kg, 1684 mg/kg, and 6676 mg/kg respectively. Concentrations of chlorinated hydrocarbons such as PCBs and pesticides were determined in all of the samples. Table 2 reports only the sites with concentrations significantly above background values. The only pesticides that were detected in significant amounts were those of the chlordane and DDT series (see Table 2). The concentrations of pesticides and PCBs were relatively evenly distributed throughout the analyzed sites with the exception of the North Gully (site 77) where concentrations were 1–2 orders of magnitude higher than at the rest of the sites. Total PCB concentrations in Montego Bay ranged from 0.76 to 73 mg/kg, which falls in the low to intermediate level compared to other anthropogenically impacted coastal bays and ports such as Boston Harbor (Eganhouse and Sherblom, 2001; about 10–800 mg/kg). Excluding the North Gully site,
Fig. 3. Ion chromatogram (m/z=191) for the aliphatic hydrocarbon fraction at the North Gully station (77). Hopanes are indicated based on carbon number (C29 to C35).
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the river mouth (site 64) had higher levels of PCBs and possibly chlordanes than the other bay sites, while the port (site 55) showed elevated levels of PCBs probably as a result of commercial shipping/port activities. The North Gully, however, seems to be the dominant source of chlorinated hydrocarbons to the bay. Considering that this site has 70% sand content, the silt/clay fraction is highly enriched in chlorinated hydrocarbons and can act as a potential point source for these compounds within the bay. The total PCB levels observed at this station (73 mg/kg) considerably exceed both the ERL of 22.7 mg/kg total PCBs used by Long et al. (1995) and the TEL criteria (21.6 mg/kg total PCBs) proposed by MacDonald et al. (1996) to quantify degradation of sediment quality in estuaries within the USA. Although the chlorinated pesticide levels found at Montego Port are not as elevated as at the north Gully, the PCB concentrations (49 mg/kg) also exceeded the ERL and TEL guidelines. Coprostanol has been widely used to trace sewage inputs to aquatic environments (Takada and Eganhouse, 1998 and references therein). The presence of coprostanol in Montego Bay sediments reflects the inputs of raw sewage to this environment. Greatest concentrations were observed at both gully sites (77 and 67), particularly at the North Gully, although the difference was in this case not as pronounced as for other contaminants (see Table 2). The levels at the gully sites were followed by the river mouth site (64), which was one order of magnitude lower, and the other two bay sites (61 and 75), which were 3 orders of magnitude lower. Coprostanol concentrations were within the low to middle range reported for other sewage-impacted coastal bays in the United States (Eganhouse and Sherblom, 2001 and references therein). While a sewage source from within the Montego River basin is likely (i.e. effluents from the WWTF), the bay sediments could be considerably influenced by sewage derived from the two gullies. High PCB concentrations at the North Gully site and elevated coprostanol levels suggest that a significant portion of the PCBs in the bay may be sewage-derived. Such a correlation has previously been suggested to exist in the Boston Harbor area (Eganhouse and Sherblom, 2001). In the case of Montego Bay, an exception may be the elevated PCB concentrations in the Port area, which are too far removed from the gully site, and most likely may have another anthropogenic source.
suspected pollutant sources such as the Montego River, the North and South gullies and the port area. In addition, these sites are influenced by incoming waters to the bay and therefore unlikely to be affected by entrained trace metals. On the contrary, and in agreement with the distribution of the organic pollutants in the Bay, the river plume sites and particularly the North Gully site (77) have generally much greater trace metal concentrations. For example, Cr, Pb and Zn (and potentially Cd) show highest concentrations at site 77. Although these metals also have higher than average concentrations at the river plume sites, these are much lower than at site 77. In the case of Cr and Pb, these metals also show higher than average concentrations at some of the central bay sites (75, 87 and 92), which are both in-line with site 77 through the predominant water circulation patterns for the bay, and may therefore be affected by particles transported from the North Gully outfall into the central and western side of the bay. Cd was not detected in the majority of the samples except at 77 and at surprisingly elevated levels at site 73. We have no explanation for this distribution. While metals such as Hg and As did not present a particular source-dependent distribution in the bay, Ni, Co, Cu and V seem to find their main source in the Montego River basin and are fairly concentrated along the river plume (sites 64, 70, 73, 75 and 87), and not as much at the mouth of the North Gully. However, these metals are also abundant in the port area (sites 53, 55 and 59) and other south-western locations (e.g. site 92). It is unclear why the concentrations of V were highest at the southern-most site (61), but there might potentially be a source of this metal in the Pies River catchment. Zn was also found to be somewhat more concentrated in the port and southwest sampling sites compared to the river plume sites. In comparison with data obtained from estuarine and coastal marine sediments of the southeastern United Sates (Windom et al., 1989), concentrations of most metals in Montego Bay, except for Zn and Pb, are within the range of those from the United Sates. Very high concentrations of Zn and Pb found at the North Gully (77), as for other pollutants, suggest a strong anthropogenic impact to this area. High concentrations of Zn and Pb often indicate inputs of anthropogenic toxicants and have been used in numerous surveys performed in US estuaries to assess environmental impacts (NOAA, 1998).
3.3. Trace metal distribution
4. Conclusions
Table 3 gives concentrations of 10 trace metals at a variety of sampling stations in Montego Bay. In all cases, trace metal concentrations were lowest at the two stations located on the north-eastern shore of the bay (sites 80 and 83). These sites are most remote from
The quality of bottom sediments of Montego Bay, is clearly affected by anthropogenic activities in the city, the port area and the drainage of the Montego River. While the North Gully seems to be the main point source of pollutants into the bay, both the port area and
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the river plume seem associated with the distribution of trace metals and organic compounds of anthropogenic origin. The predominantly southerly inflow into the bay, followed by an outflow to the southwest, allows particle-associated metals and organics to become distributed throughout the bay area. The Montego River may deposit such materials along its plume, in a northwestern direction from the river mouth. However, an apparent preferential accumulation of trace metals at site 92 seems to indicate particle transport into a more westerly direction of the river plume (possibly during low water discharge periods) and/or transport of resuspended particles from the port area into the bay. As to the nature of anthropogenic inputs into the Montego Bay area, both industrial (trace metals, PCBs and petroleum hydrocarbons), agricultural (pesticides) and sewage (coprostanol) sources were found to be important. The two gullies, particularly the North Gully, represent the most significant source of anthropogenically-derived inputs to the bay. High concentrations of raw sewage (as indicated by high coprostanol levels), street runoff (UCM, hopanes, PAHs and Pb), and industrial chemicals (PCBs, pesticides, Zn, Pb and Cr) are clearly introduced into Montego Bay through this means. With a few exceptions, such as the trace metals Co, Ni and Cu, the North Gully is the main pollution point source reported in this study. The environmental effects of sewage-derived waste-waters to Montego Bay are expected to improve after the completion of the new waste-water treatment facility in 2000 (samples reported in this study were collected prior to this date).
Acknowledgements The authors thank The Louis Berger Group, Inc. for assistance with sediment sampling and access to some bulk sediment data. Thanks also to the Southeast Environmental Research Center and the Department of Chemistry Advanced Mass Spectrometry Facility at FIU for providing instrument time. A.S. and A.F. thank FIU for student fellowships. SERC contribution 188.
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