Wet And Dry Deposition Studies Of Aerosol Hazes Around A Major Sawdust Open Burning Area
Keywords:
Dry Deposition, Wet Deposition, Deposition Velocity, Scavenging RatioAbstract
The continuous generation of aerosol species from natural and anthropogenic sources around saw dust open burning sites necessitates extensive deposition study of such areas. This work used the concepts of deposition velocity and scavenging ratio to study the removal mechanisms of heavy metal constituents of the aerosol in a sawdust open burning area. The aerosol concentration of the area was determined using gravimetry method with a high volume sampler fitted with a two-filter holder and exposed filters. A sampling period of 6-hours was adopted. Twenty seven deposition gauges were deployed to the sampling site to measure the flux of settleable particulate matter. Aerosol samplings and deposition flux rates measurements were carried out in the area in the wet (July, 2008; May, 2009) and dry (October, 2008; February, 2009) seasons. The measured average deposition flux rates in wet were evaluated to be 1.092 x 10-3 µgm-2s-1 in July, 2008; 1.388 x10-3 µgm-2s-1 in May, 2009 while that of dry season were evaluated to be 1.587 x 10-3 µgm-2s-1 in October, 2008 and 1.933 x 10-3 µgm-2s-1 in February, 2009. The calculated deposition velocities for the trace metals in the area had values between 3.87 x 10-7 – 2.11 x 10-4 m/s while the estimated scavenging ratios were found to be between 0.82 – 1224.31 in the study area. The results showed that Cd, Pb, and Sb are better removed through gravitational settling of particles while Fe, Mn, Cr and Ti are scavenged by precipitation.
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