Contribution of road dust from Low Impact Development (LID) construction sites to atmospheric pollution from heavy metals.

The re-suspension of road dust due to intense Low Impact Development (LID) construction activities may be a major contributor to atmospheric metal pollution. However, the distribution characteristics, mobility potential, and pollutant load of atmospheric particles at LID construction sites are not clear. Consequently, management practices to mitigate air pollution from LID construction are lacking. We investigated the atmospheric metal pollution from road dust produced during different construction stages of rain gardens and porous pavements and estimated the ecological risks posed by the heavy metals. Although concentrations of heavy metals in road dust at LID construction sites were lower than at sites without LID construction, the ecological risks posed by the atmospheric heavy metals at LID construction sites were generally higher due to the greater mass of road dust produced during LID construction. Hence, LID management practices should focus on the removal of road dust, especially finer particles (<44 μm) produced during early construction stages. In roads, the zones influenced by LID construction is related to road types based on traffic volume; these road types in descending order of zone influenced by LID construction are: arterial road (400-600 m) > collector road (100-150 m) > access road (50-100 m) > laneway (30-50 m). Based on the study sites, we estimate LID construction in China will contribute 2.31 and 6.23 times as much as the current load of atmospheric particles by 2020 and 2030; and we project atmospheric heavy metals will be 1.45-2.18 and 2.82-4.73 times greater than the current load by 2020 and 2030 from the intense LID construction. Based on our results, several regulatory recommendations are presented to mitigate air pollution at LID construction sites.