『Abstract
　Trace metal adsorption to suspended particulate matter (SPM) influences bioavailability and toxicity of trace metals in natural waters. For highly contaminated urban catchments in the greater Auckland (New Zealand) area, trace metal adsorption to SPM was assessed and compared to similar data from non-urban catchments in the Auckland region, to determine whether there was any difference in the ability of the SPM to adsorb Cu, Pb and Zn. The degree of trace metal adsorption onto the SPM was assessed by way of adsorption edge experiments. It was found that the ability of the Auckland urban SPM to adsorb trace metals decreased in the order Pb＞Cu＞Zn. Little difference in adsorption was observed between the non-urban Waikato and Kaipara River SPM and urban SPM, or between urban SPM from different flow regimes and seasons, despite some compositional differences in the SPM. This suggests that on the basis of a single surface-binding site, metal adsorption onto SPM could be readily predicted across a range of urban and non-urban catchments in the Auckland region. Adsorption edges were modelled with a diffuse layer, surface complexation model to assess the role of Fe-oxide in adsorption. The MINTEQA2 model was used, assuming Fe-oxide (as HFO) was the only adsorbing surface. There was generally good agreement between observed and modelled adsorption for Pb, indicating the importance of Fe-oxide surfaces for Pb adsorption. However, the model did not predict Zn or Cu adsorption as well. The TOC content of the SPM, and presence of dissolved ligands and organic matter in the water column, appeared to play an important role in Cu adsorption to the SPM. For Zn, the presence of adsorbing surfaces other than HFO appeared to influence adsorption.』

1. Introduction
2. Methodology
　2.1. Urban site description
　2.2. SPM collection and characterisation
　2.3. Trace metal adsorption experiments
　2.4. Non-urban site description and SPM collection
　2.5. Adsorption modelling using MINTEQA2
3. Results
　3.1. Urban SPM adsorption edges
　3.2. Comparison of urban and non-urban adsorption edges
　3.3. Modelling metal adsorption edges using MINTEQA2
　3.4. Modelling in situ metal adsorption using MINTEQA2
4. Discussion
　4.1. Flow effects on trace metal adsorption
　4.2. Seasonal effects on trace metal adsorption
　4.3. Catchment use effects on trace metal adsorption
　4.4. Assessing the role of Fe-oxide in trace metal adsorption to SPM
　　4.4.1. Lead adsorption to SPM
　　4.4.2. Copper adsorption to SPM
　　4.4.3. Zinc adsorption to SPM
5. Conclusions
Acknowledgements
References