Contaminant pathways in Port Curtis: Final report - OzCoasts

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Contaminant pathways in Port Curtis: Final report2: Dissolved trace metalsA much larger geographical area was investigated than in the SLRA in order toidentify potential sources of trace metals to Port Curtis. Two sampling trips wereundertaken, first along axial transects extending away from possible point sourceswithin the Harbour and second, through The Narrows, and targeted samplingalong transects and up selected waterways, including the Fitzroy River. Periodicsampling at two fixed locations was undertaken to determine possible temporalvariations in dissolved metal concentrations. The influence of small pH variationsand sediment resuspension on metal release was also investigated.2.2 ExperimentalTwo extensive field surveys were carried out in successive years: Survey 1(1–3 December 2003) and Survey 2 (6–9 December 2004). In Survey 1, watersamples were collected from 49 sites approximately 4 km apart along fourtransects: (i) north-west of Gladstone and through The Narrows, (ii) south-east ofGladstone to Hummock Hill Island then north-east into coast water, (iii) north-eastfrom the seaward side of Facing Island, and (iv) north-east from Keppel Bay tobeyond Great Keppel Island (maximum distance from shore was 55 km). InSurvey 2, water samples were collected from 51 sites and included: (i) a repeattransect through The Narrows, (ii) targeted sampling in the larger inlets and creeksof the northern section of Port Curtis and through The Narrows to the FitzroyDelta, (iii) larger inlets and creeks of Fitzroy delta, the Fitzroy mouth and up theFitzroy River.Temporal sampling to assess possible short-term fluctuations in dissolved metalsconcentrations was undertaken at a point 3 km south of Ramsay’s Crossing(7–8 December 2004, hourly sampling for 5 h) and Fisherman’s Landing(8–9 December 2004, sampling over a 29 h period).Since the waters of Port Curtis are well mixed, only surface water samples werecollected. Ultratrace sampling techniques described by Apte et al. (2002) wereemployed. All trace metal sample analyses were undertaken in a trace metalsclean room. Dissolved copper, cadmium, nickel, lead and zinc were analysedusing a dithiocarbamate complexation/solvent extraction, and GF-AAS detectionprocedure described elsewhere (Apte et al. 1998). For all analyses, spikingrecovery tests, duplicate determinations, sea water certified reference material(CRM) CASS-4 (National Research Council of Canada) and blanks wereprocessed as part of routine quality control procedures.9
Contaminant pathways in Port Curtis: Final report2: Dissolved trace metals2.3 Results and discussionQuality control data indicated satisfactory performance with reference materialvalues (cadmium, copper, nickel, lead and zinc) ranging from 86–99% of thecertified values. Spike recoveries ranged from 88–102% for the metals of interest.2.3.1 Dissolved metal concentrationsThe dissolved and particulate metals results for the two surveys are summarisedin Tables 2.1 and 2.2. Figure 2.2 shows the dissolved concentrations of copper,nickel and zinc along the sampling transects of Survey 1 and during Survey 2when the Fitzroy River region was also investigated. Dissolved concentrations ofcopper and zinc were typically in the low parts per billion range (µg/L) anddissolved concentrations of cadmium, nickel and lead were typically in the lowparts per trillion range (ng/L). The lowest metal concentrations occurred in theopen water sites north-east of Facing Island (dissolved cadmium, copper, nickel,lead, and zinc were
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