Moreover, the most significant PM10 reduction was exhibited when an episode of dust flow accompanied by a south-eastern wind occurred. The main source of this dust flow is long-range particle transference from the Sahara desert and Sinai, due to synoptic conditions (Astitha et al., 2008). In this case, when the dust source was atmospheric, the high efficiency of the treed park with dense foliage volume was demonstrated. PM10 concentration was reduced from a value of 218 mG/m3 in the adjacent street canyon to a value of 64 mG/m3 in the urban park. During the summer, the mean PM10 concentrations found in the urban park were low and unexpectedly, the lowest mean PM10 concentrations were found in the urban square. It seems that anthropogenic activity in the park (sports, recreation and dog activity) lift up dry sand and dust from the soil surface and caused an increase of PM10 concentrations. This phenomenon was not observed in the winter when the soil is moist.