Source apportionment of the ionic components in precipitation over an urban region in Western India.
BACKGROUND
Inorganic ion concentrations in event-based wet-only precipitation samples collected during the south-west (SW) monsoon at an urban location in Western India, Ahmedabad between July 2000 and September 2002 were measured by Rastogi and Sarin (2007).


METHODS
For the first time at a location in India, an advanced factor analysis model was retrospectively applied to the measured concentrations of ions (Rastogi and Sarin 2007) in precipitation for source apportionment. Positive matrix factorization resolved five factors, including crustal material, sea salt, nitrate/sulfate-rich factor, ammonium-rich factor, and free acidity.


CONCLUSIONS
Amongst the model-resolved factors, crustal material was the highest contributor to the total dissolved solids (TDS) accounting for 44.1% on average. Potential source contribution function (PSCF) analysis identified source locations along the eastern coast of Somalia, Yemen, Oman, and the United Arab Emirates for this factor. Sea salt was the second highest contributor accounting for 29.8%. The potential source regions of this factor were also identified in the Arabian Sea and the southern Indian Ocean along the coast of Africa, and the Arabian Gulf. This study also examined the spatial relationships between the source locations of chemical species in precipitation and in ambient aerosol (resolved in an earlier study).


CONCLUSIONS
Crustal material was the highest contributor to TDS at the study location. Spatial relationships between aerosol and precipitation factor source regions suggested that below-cloud scavenging of aerosol particles was a likely contributor to the chemical species apportioned to various precipitation factors. Additionally, source types of chemical species in precipitation resolved in this study were qualitatively compared with those identified at other locations in India. The comparison showed that soil was an important contributor to the dissolved mass of chemical species in precipitation at all locations in India.
Raman
Ramya Sunder
RS
Space and Atmospheric Sciences Division, Physical Research Laboratory, Navrangpura, Ahmedabad, 380 009, India. ramyasr@iiserbhopal.ac.in
Ramachandran
S
S
D000351:Africa, Eastern; D000393:Air Pollutants / Q000032:analysis / Q000737:chemistry; D002947:Cities; D016208:Databases, Factual; D004784:Environmental Monitoring; D004787:Environmental Pollution / Q000706:statistics & numerical data*; D006863:Hydrogen-Ion Concentration; D007194:India; D019156:Indian Ocean; D007287:Inorganic Chemicals / Q000032:analysis* / Q000737:chemistry; D008670:Metals / Q000032:analysis / Q000737:chemistry; D008877:Middle East; D015233:Models, Statistical; D017672:Nitrogen Compounds / Q000032:analysis / Q000737:chemistry; D011891:Rain / Q000737:chemistry*; D054712:Salinity; D012621:Seasons; D012987:Soil / Q000032:analysis; D013457:Sulfur Compounds / Q000032:analysis / Q000737:chemistry; D014919:Wind
D000393:Air Pollutants; D007287:Inorganic Chemicals; D008670:Metals; D017672:Nitrogen Compounds; D012987:Soil; D013457:Sulfur Compounds