Chemical composition of dew in Amman, Jordan

Twenty-six dew samples were collected on a glass surface from an urbanized area in Amman city during the period October 1999 to June 2000. They were a nalyzed for the major ions (Cl, SO4, NO3, Ca, Mg, Na, K and NH4) in additio n to three heavy metals (Pb, Cd and Co). Rain samples were collected for th e same period and compared to the chemical constituents of dew. It was found that both rain and dew samples were of almost neutral acidity due to the buffering effect of CaCO3. Dew composition was mainly from CaSO4 solution due to conversion of CaCO3 to CaSO4 when left exposed to a sulfat e-rich atmosphere. The total dissolved solids were higher in dew than rain samples of the same period. This was attributed to higher evaporation effec t on dew than rain. The heavy metal content in dew is highest during the cold winter season (De cember-March) due to excess fossil fuel combustion for heating purposes in this period. The heavy metal content in dew was lower than that for rain du ring the same period because of the shorter period of dew formation than ra inwater. (C) 2001 Elsevier Science B.V. All rights reserved.