Temporal variability in residence time of ambient aerosols using environmental ~(210)Pb

摘要

The regional air quality, atmospheric chemistry and climate change are largely influenced by the chemical composition of ambient aerosols and more importantly, by their residence time on a spatial and temporal scale. The environmental radionuclidePb (t_(1/2) = 22.3 years), injected into the atmosphere byin situ decay of its parent nuclide ~(222)Rn (t_(1/2) = 3.8 days) from ground sources, is highly particle reactive and thus serves as an ideal tracer to assess the residence time of anthropogenic and natural aerosols from ground-based sources. We report on the temporal variability in residence time of ambient aerosols studied from an urban site (Ahmedabad) and a high altitude site (Mt Abu) in western India. The residence time of aerosols, ranging from ~2 to 8 days, is predominantly controlled by regional meteorology and high dust abundance (shorter removal time) in semi-arid regions. These observations raise the issue of uncertainty in tracing the source region of atmospheric pollutants basedon air-mass back trajectory analyses without knowing their actual residence time for a given time-period over a study region.