Contaminant pathways in Port Curtis: Final report - OzCoasts

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!!!!!!!!!! ! !!! ! !!!! !!! !!!! ! !!!!!!! ! !! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! !! !! ! !!!!!!!!!!!!! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! !!! ! ! !!!!!!!! !! ! !! ! ! ! ! ! ! !! ! ! ! ! ! ! !! ! !! ! !! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! !!!!!!!!! ! ! ! ! ! !!!! ! ! ! !! ! ! !! !!! !! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! !!!!! !!!!! !! ! ! ! ! ! ! !! !! ! ! ! ! ! ! !! ! !!! ! ! ! ! ! !!!! ! ! ! !! ! ! !! !!! !!!Contaminant pathways in Port Curtis: Final report2: Dissolved trace metals! ! !pH! ! ! ! !! ! ! ! !7.79 - 7.957.95 - 8.068.06 - 8.138.13 - 8.178.17 - 8.208.20 - 8.228.22 - 8.248.24 - 8.298.29 - 8.358.35 - 8.46! ! ! !! ! ! ! !! ! ! ! !Salinity (ppt)35.79 - 36.0136.01 - 36.1836.18 - 36.3036.30 - 36.3936.39 - 36.4636.46 - 36.5536.55 - 36.6736.67 - 36.8436.84 - 37.0637.06 - 37.36Figure 2.4. Water pH and salinity in the Port Curtis regionThe higher salinities and lower pH values measured in The Narrows will influencethe partitioning of metals towards the dissolved phase. The Narrows is also likelyto contain greater quantities of dissolved organic matter than the harbour due to agreater mangrove surface area to water volume ratio in this area. Complexation ofmetals (especially Cu) by natural organic ligands is therefore expected in theseareas.17
Contaminant pathways in Port Curtis: Final report2: Dissolved trace metals2.3.5 Sources of dissolved metalsA comparison of the dissolved metals concentrations measured in Port Curtis, TheNarrows and coastal waters is presented in Table 2.3. Based on this summarydata and the transect plots shown in Figure 2.2, it is clear that The Narrows regionis elevated in trace metals—especially nickel and copper. During Survey 1,dissolved copper and nickel concentration maxima occurred in The Narrows andwere 637 and 905 ng/L, respectively. The dissolved nickel maxima occurredfurther (~8 km) north in The Narrows than dissolved copper, which may reflectdifferent sources of these metals. Dissolved lead and zinc concentrations,however, were higher in Port Curtis (Table 3) and may reflect the importance ofindustrial inputs. As shown in Table 2.3, the Fitzroy River plume is particularlyenriched in dissolved nickel and to a lesser extent dissolved copper. This may actas a potential source of dissolved metals to the north of The Narrows.The maxima in dissolved copper and nickel, occurring in The Narrows do notnecessarily imply that this region is a source of these metals to Port Curtis. Thevolume of water in The Narrows is small compared to the volume of water in theharbour and may not be a significant source to Port Curtis. Mass balancecalculations using the hydrodynamic model are required to explore this issue.2.4 Conclusions1. This study has provided the first accurate data on dissolved trace metalconcentrations in the coastal waters of Central Queensland and in closeproximity to the Great Barrier Reef. It is somewhat surprising that theaccurate measurement of dissolved metal concentrations in this sensitiveecological region has been previously overlooked. This is probably areflection of the technical difficulties in making such measurements at part pertrillion concentration ranges. In the offshore coastal waters, dissolved metalconcentrations were extremely low and were comparable to concentrationsmeasured at open Pacific Ocean and New South Wales coastal waterlocations. Trace metal limitation rather than trace metal contamination islikely to be more of an issue for organisms inhabiting these waters.2. Intensive surveying of Port Curtis has confirmed the presence of elevatedmetal concentrations within the harbour. The Narrows region was found tohave the highest concentrations of copper and nickel. This was previouslythought to be a relatively pristine area.18
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Contaminant pathways in Port Curtis: Final report - OzCoasts

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