Abstract: Vehicular emission is the key source of air pollution in the urban environment. This includes both fine particles (PM2.5) and coarse particulate matters (PM10). However, particulate matter emissions from road traffic comprise emissions from exhaust tailpipe and emissions due to wear and tear of the vehicle part such as brake, tire and clutch and re-suspension of dust (non-exhaust emission). This study estimates the share of the two sources of pollutant particle emissions from on-roadside vehicles in the Addis Ababa municipality, Ethiopia. To calculate its share, two methods were applied; the exhaust-tailpipe emissions were calculated using the Europeans emission inventory Tier II method and Tier I for the non-exhaust emissions (like vehicle tire wear, brake, and road surface wear). The results show that of the total traffic-related particulate emissions in the city, 63% emitted from vehicle exhaust and the remaining 37% from non-exhaust sources. The annual roads transport exhaust emission shares around 2394 tons of particles from all vehicle categories. However, from the total yearly non-exhaust particulate matter emissions’ contribution, tire and brake wear shared around 65% and 35% emanated by road-surface wear. Furthermore, vehicle tire and brake wear were responsible for annual 584.8 tons of coarse particles (PM10) and 314.4 tons of fine particle matter (PM2.5) emissions in the city whereas surface wear emissions were responsible for around 313.7 tons of PM10 and 169.9 tons of PM2.5 pollutant emissions in the city. This suggests that non-exhaust sources might be as significant as exhaust sources and have a considerable contribution to the impact on air quality.
Abstract: In this paper the influence of heterogeneous traffic on
the temporal variation of ambient PM10, PM2.5 and PM1
concentrations at a busy arterial route (Sardar Patel Road) in the
Chennai city has been analyzed. The hourly PM concentration, traffic
counts and average speed of the vehicles have been monitored at the
study site for one week (19th-25th January 2009). Results indicated
that the concentrations of coarse (PM10) and fine PM (PM2.5 and
PM1) concentrations at SP road are having similar trend during peak
and non-peak hours, irrespective of the days. The PM concentrations
showed daily two peaks corresponding to morning (8 to 10 am) and
evening (7 to 9 pm) peak hour traffic flow. The PM10 concentration is
dominated by fine particles (53% of PM2.5 and 45% of PM1). The
high PM2.5/PM10 ratio indicates that the majority of PM10 particles
originate from re-suspension of road dust. The analysis of traffic flow
at the study site showed that 2W, 3W and 4W are having similar
diurnal trend as PM concentrations. This confirms that the 2W, 3W
and 4W are the main emission source contributing to ambient PM
concentration at SP road. The speed measurement at SP road showed
that the average speed of 2W, 3W, 4W, LCV and HCV are 38, 40,
38, 40 and 38 km/hr and 43, 41, 42, 40 and 41 km/hr respectively for
the weekdays and weekdays.
Abstract: In hydrocyclones, the particle separation efficiency is
limited by the suspended fine particles, which are discharged with the
coarse product in the underflow. It is well known that injecting water
in the conical part of the cyclone reduces the fine particle fraction in
the underflow. This paper presents a mathematical model that
simulates the water injection in the conical component. The model
accounts for the fluid flow and the particle motion. Particle
interaction, due to hindered settling caused by increased density and
viscosity of the suspension, and fine particle entrainment by settling
coarse particles are included in the model. Water injection in the
conical part of the hydrocyclone is performed to reduce fine particle
discharge in the underflow. The model demonstrates the impact of
the injection rate, injection velocity, and injection location on the
shape of the partition curve. The simulations are compared with
experimental data of a 50-mm cyclone.