Source and transport of trace metals in the Hatea River catchment and estuary, Whangarei, New Zealand

Abstract A survey of Cu, Pb, Zn, Cr, and As concentrations in bed sediment, fresh waters, storm waters, and suspended particulate matter (SPM) has been undertaken in the Hatea River catchment, Whangarei, New Zealand. The most recently deposited sediment in the Hatea River estuary has elevated levels of Cu, Pb, and Zn, derived from tributaries draining the more densely‐populated western side of the catchment, city stormwater drains, and Cu‐bear‐ing antifoulants used in the marina. All trace metals were transported in both “dissolved” and particulate form in the freshwater tributaries. However, an estimated loading of metal transported by the lower Hatea River under different flow regimes indicated that trace metals were predominantly conveyed by coarse (>0.45 μm) SPM during the periods of highest river flow. Of the trace metals studied, Pb showed the strongest association with coarse SPM and the greatest potential for accumulation in estuarine sediment, demonstrating little tendency to be leached from sediment under simulated estuarine conditions.

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