<smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place" downloadurl="http://www.5iantlavalamp.com/"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="country-region" downloadurl="http://www.5iantlavalamp.com/"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City" downloadurl="http://www.5iamas-microsoft-com:office:smarttags"> Number concentration characteristics of ultrafine aerosols (atmospheric nanoparticles / aitken nuclei) during 2008 over western Himalayan region, Kullu-Manali, India </smarttagtype></smarttagtype></smarttagtype>

Abstract

<smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place" downloadurl="http://www.5iantlavalamp.com/">

The ultrafine particles of three sizes 200, 30 and 10 A [20 nm (aitken mode), 3 nm, 1 nm (nucleation mode / nano particles)] were monitored with water based condensation particle counter during January-December 2008 at Mohal in Kullu-Manali area of North western Himalayas. The results indicate that diurnal pattern has faint bimodal structure with two peaks, one in morning and other in evening but is not as distinct as found in plains. There is rather constant particle density pattern consistent with vehicular movement from morning till evening. This may also be due to abnormally large bursts of particles (nucleation bursts) which are found to be more in summer than winter, more during sunrise and less during afternoon. The weak nucleation bursts are found to be frequent throughout the year than very strong nucleation bursts which are mostly found during months of June, July and August. The monthly 24 h average density gradually picks up from January, increases rapidly in summer months and then decreases in winter. The density is more in summer than in winter, a trend opposite to plains, may be due to development of warm thermal layer on valley floor while cold layer developed along snowy hilltops in winter leading to convection of fine particles up the slopes of valley during daytime. The relatively more value in September and October is due to month long international Dussehra festival in the valley and unexpected lower values in November and December may be due to low local as well as tourist traffic flow; washout/rainout effects; and higher inversion layer. The vehicular survey conducted agrees well with diurnal, monthly as well as yearly averaged diurnal variation of fine particles. The annual average of 24 h average value of ultrafine particles of three size range is 18045±1212, 16811±2790, and 15407±3109 N cm^-3, respectively. The comparison with earlier results shows significant increase of ultrafine particles indicating impact of vehicular increase in the region.

</smarttagtype>