Sulphur dioxide measurements in Nairobi

Abstract

Sulphur dioxide in ambient air at Nairobi's major Industrial area and its environs was measured using pararosaniline method. In this study, concentrations for a period of six months (June - November, 1993) at six sampling sites are presented. The data was collected in Nairobi Industrial area and two residential areas, South Band Makadara. Sampling was done during morning hours, from 9.00 am to 11.30 am and from 2.00 pm to 4.30 pm for afternoon hours, to give the average concentration for a given day. The monthly average concentrations was higher at the Industrial area (24.4-175.5mglm3) than at the residential sites (14.2-72.5mglm\ Sampling sites located closer to major Industries recorded higher values than those far away. Sites downwind of the industrial area recorded higher concentrations than sites located upwind. In all sampling sites, higher concentrations were found in the morning hours (9.00-11.30am) than the afternoon hours (2.00-4.30pm). June-september period recorded generally high concentrations (14.2-175.5mglm\ Climatological information indicated that this period is characterized by high frequency of stable conditions and calm winds. October -November period had lower concentrations (14.0 - 157.8mglm3) due to favourable dispersion conditions (higher wind speeds and unstable conditions) experienced during this period. The average monthly concentrations at the industrial area was found to exceed World Health Organization(WHO) guidelines on some occasions, implying this could pose serious health problems to the people staying nearby. In the context of Sulphur dioxide emissions, the industrial development in Kenya has not reached a level where serious health problems may arise except during those months characterized by poor dispersion conditions and in those areas closer to industries.