Heavy metal contamination is often pronounced in urban watersheds as urban stormwater runoff generally contains higher concentrations of heavy metals than that from watersheds dominated by other land cover types, with serious consequences for aquatic ecosystems. Pollution involving heavy metals is of particular concern due to their toxicity and persistence. Contamination can impact stream biota as well as shellfish and invertebrates living or feeding in bottom substrates. Our previous work demonstrates that landscape composition and configuration indicators (e.g. land cover in % and spatial arrangement) generated from high spatial resolution map are promising in explaining instream water chemistry and biotic community variability. Here, we improve upon current stormwater management approaches by developing landscape indicators suited to monitoring heavy metal concentrations in urban streams. Furthermore, roads are a key feature of urban landscapes that impacts heavy metal concentrations. As such, we use high spatial resolution urban land cover to provide greater discrimination among different road features (e.g. local, collector, arterial roads) within the study region and then link these landscape indicators to concentrations of Copper (Cu), Lead (Pb), Zinc (Zn), Cadmium (Cd) and Iron (Fe) in streams across the Greater Vancouver Region in British Columbia, Canada.
Results/Conclusions
Overall, our work demonstrates the explanatory power of landscape indicators varies with the temporal and spatial scale over which they are measured. The spatial arrangement of land cover also plays a large role in explaining heavy metal concentrations. We found that landscape compositional indicators individually explained up to 30% of the variability in heavy metal concentrations. As an improvement, incorporation of landscape configuration into the models explained nearly 60% of the variability in heavy metal concentrations. Our results also showed that differentiating deciduous and coniferous forest types was important in explaining the variation in heavy metal concentrations. As such, investigation of heavy metal concentrations in urban streams using improved landscape indicators will provide further improvements to our ability to assessment urban aquatic ecosystem health. This work creates a monitoring approach applicable and transferable across all Canadian cities interested in maintaining the ecological health of their urban streams while supporting growth and urban expansion.