Wednesday, All Day in Poster Hall
, Thursday, All Day in Poster Hall
(subject to change)
We have measured near-source dry deposition of nitrogen gases (NOx, NH3) from vehicle emissions on Cape Cod, MA. Recent evidence suggests that total nitrogen deposition in urban and suburban areas can be substantially higher than estimated using data from national monitoring stations, which are located purposefully away from such areas, and which do not measure dry deposition of some important gaseous components. We examined summertime patterns of nitrogen pollution and deposition along 5 to 150 meter gradients away from two roads (16,000 veh/day average), using gas concentration measurements made with passive samplers and literature-based depositional velocities, and measurements of nitrogen in bulk (open field) and throughfall collectors. Bulk nitrogen deposition shows no pattern along the gradient, whereas throughfall nitrogen is greater than bulk, and is highest nearest the road and decreases with distance. Gaseous nitrogen deposition is highest near the road and falls exponentially with distance, decreasing 60 to 80% over 20 meters. We estimate that within 50 meters of the road, dry nitrogen deposition is half of total nitrogen deposition, with two thirds from NH3, and one third from oxidized nitrogen. Our results indicate that vehicle traffic is likely a significant source of nitrogen deposition to developed coastal areas.
