Variations of anions (SO42-, NO3-, NO2-, Cl- and F-), cations (K+, Na+, Ca2
+, Mg2+ and NH4+) and pH values in precipitation, througfall and stemflow s
amples collected over a four-year period (1995-1998) in Beijing (two sites
Zhongguancun and Mangshan) are presented. The annual volume-weighted range
of pH values were 6.57-7.11 in precipitation, 5.46-6.86 in thoughfall and 5
.32-6.41 in stemflow. The fominant anion was SO42-, while Ca+ and NH4+ were
the main cations in precipitation, throughfall and stemflow. Most of ion c
oncentrations with precipitation, throughfall and stemflow volume showed ne
gative correlation, except for some ones. Significant correlation values we
re also found between ions (SO42-, NO3-, Cl-, F-, Ca2+, Mg2+ and Na+) in pr
ecipitation, throughfall and stemflow indicated the common sources of these
ions such as coal combustion, automobile emission and fertilizers applicat
ion. Compared to precipitation, there was an increased ion concentration in
throughfall or in stemflow. Changes of ion concentrations were in Quercus
liatungensis Koiz. and Pinus tabulaefornis Carr. throughfall (or stemflow)
because of different crown and bark qualities of tree species.