Atmospheric Environment 38 (2004) 4175–4181 Suspended particulate matter and its relations to the urban climate in Dar es Salaam, Tanzania P. Jonsson a, *, C. Bennet a,b , I. Eliasson a , E. Selin Lindgren c a Earth Sciences Centre, Physical Geography, Go¨teborg University, P.O. Box 460, SE 406 30 Go¨teborg, Sweden b SMHI (Swedish Institute of Meteorology and Hydrology), Folkborgsva¨gen 1, SE 601 76 Norrko¨ping, Sweden c University College of Bora˚s, SE 501 90 Bora˚s, Sweden Received 29 October 2003; received in revised form 2 April 2004; accepted 20 April 2004 Abstract Relationships between sources and levels of particulate matter and climatic parameters (urban heat island intensity, wind speed, temperature and relative humidity) were investigated in the coastal city of Dar es Salaam, Tanzania’s largestcity.Measurementsweremadeduringthewetanddryseasonsof2001atanurbanandaruralsite.Fiveelements were used to represent different sources: K in fine particles (biomass), Zn in fine particles (industry), Cl in coarse particles(seaspray),Tiincoarseparticles(soil)andPbinfineparticles(traffic).Theconcentrationsoftheseelements variedconsiderablybetweentheurbanandruralsiteduringboththewetanddryseason,withtheurbansiteinthedry seasonhavingthehighestconcentrations.Diurnaldifferencesarealsoapparent,althoughnotasstraightforward.Inan attempt to explain these differences, correlations between all elements and the climatic parameters were investigated. The results show that the nocturnal urban heat island intensity was positively correlated and wind speed negatively correlated with particulate levels, presumably due to the increased atmospheric stability. r 2004 Elsevier Ltd. All rights reserved. Keywords: Urban climate; Suspended particulate matter; Elements; Energy dispersive X-ray fluorescence; Dar es Salaam; Seasonal variations 1. Introduction Urbanclimateandtheairpollutionsituationofacity are connected in several ways. Topography set aside, climaticparameterssuchasstability,winddirectionand speed govern the dispersion of air pollution. However, alltoooftenurbanclimateandairpollutionaretreated separately. In areas of rapid urbanization, such as Africa,understandingoftheinteractionbetweenthetwo can be a valuable tool for urban planners to mitigate potentialnegativeeffects.Thebestdocumentedexample of urban climate modification is the urban heat island wherebyanurbanareaiswarmerthanitssurroundings. The study of urban climate becomes more complex if a coastal city is considered. The land/ocean temperature contrast generates the well described diurnal sea breeze, and the contrast is further strengthened by the urban heat island (Yoshikado and Tsuchida, 1996). Nieuwolt (1973) illustrates the effect of the sea breeze on comfort climateinDaresSalaam,Tanzania.Coastalstationsare colder than inland counterparts when the sea breeze is welldeveloped.Itisalsoshownthatthecycleofdiurnal sea breeze and nocturnal land breeze only exists in March, early April, September and October. In many African cities air pollution is neither monitored nor controlled, and there are no long-term records of pollution levels and impacts. There are some major differences in anthropogenic air pollution between Africa and the industrialized world. In Africa biomass burningfrombushfiresandfuelwoodconsumptionisa major source of pollutants (The World Bank, 1996). Transport is a more dominant source in industrialized countries. ARTICLE IN PRESS AE International – Africa & the Middle East *Corresponding author. E-mail address: pelle@gvc.gu.se (P. Jonsson). 1352-2310/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2004.04.021