Quantifying the Spatial Variability of Airborne Pollutants to Stormwater Runoff in different Land-Use Catchments

An understanding of the effects of land-use activities on atmospherically derived pollutant loadings in stormwater is helpful for determining appropriate treatment strategies for different catchments. Impervious concrete boards (≈1 m²) were deployed for 11 months in different land-use areas (industrial, residential and airside of an airport’s runway) throughout Christchurch, New Zealand, to determine the spatial variability of atmospherically derived pollutants in stormwater runoff. Runoff was analysed for metals (principally Cu, Zn and Pb) and total suspended solids (TSS). All three land-use areas exhibited similar temporal patterns of varying metal and TSS loads, indicating that atmospherically deposited metals and TSS had a homogenous distribution within the Christchurch airshed. However, mean pollutant loadings for all total metals and TSS were significantly higher in the industrial area compared to the residential and airside areas, which had statistically similar mean metal loadings. The signature ratios of specific heavy metals (As, Cr, Mn, Ni, Pb, Sr and Zn) to Cu were relatively homogeneous between the three land-use areas, indicating that the pollutants originate from a similar source and that surrounding land-use was not as an important factor in determining atmospheric pollutant loadings to stormwater runoff as previously thought.