A New Method for Assessing the Contribution of Atmospheric Deposition to the Stormwater Runoff Metal Load in a Small Urban Catchment

Abstract

The contribution of atmospheric deposition to the metal load at the outlet of a small urban catchment (Pin Sec, France) was studied. A new method taking into account the nature of urban surfaces (glass, tile, bitumen, zinc sheet, grass, facade coating, and slate) was developed to measure atmospheric dry deposition. Dry deposition, wet deposition and stormwater loading were measured from September 2010 to August 2011. At the year scale, atmospheric deposition was not a major contributor to the metal load at the outlet of this small catchment. Wet deposition ranged from < 1 % to 29 %. The contribution of dry deposition (generally less than 5%) was especially low and appeared to be smaller than that reported in previous studies. On this catchment, the major part of the metal load could be attributed to stormwater runoff (64-99%). Though several hypotheses were made e.g. grass (not an impervious surface) was not taken into account and it was considered that all the deposits were washed off. This methodology looks promising and should be taken into consideration when carrying out new researches on the contribution of atmospheric deposition to the pollution load in urban catchments.