Simorn May, Amnat Chidthaisong, Sirintornthep Towprayoon, and Winai Somboon

pp. 543 - 552

Abstract

To estimate wet deposition of nitrogen in Phnom Penh city, Cambodia, rainwater samples at four locations in the center and suburb areas were collected and analyzed during 24 June 2005 to 21 July 2005. The results showed that concentrations of NO₂^- were lower than that of NO₃^- and NH₄⁺ at all investigated
sites. The NO₂^- concentration range was 0.18-0.33 mg L^-1 (average ± S.D., 0.23±0.05 mg L^-1). The major inorganic nitrogen species in rainwater were     NO₃^-  and NH₄⁺. The NO₃^- concentrations ranged from 1.43 to 1.98 mg L^-1 (average 1.71±0.18 mg L^-1) while that of NH₄⁺ ranged from 0.49 to 0.75 mg L^-1 (average 0.61±0.07 mg L^-1). Statistically, both the average NO₃^-  and NH₄⁺ concentrations were not significantly different among the sampling sites (p<0.05). The amount of wet deposition during study period was then estimated by multiplying these concentrations with the amount of rainfall. It was found that wet deposition depended mainly on the rainfall amount. The average ± S.D wet depositions of NO₂^-, NO₃^- and NH₄⁺ during the onemonth study period were 110±30, 610±230, and 740±260 g N ha^-1, respectively. During the study period,
NO₂^- , NO₃^- , and NH₄⁺ contributed 8, 42, and 50% to the total wet deposition of inorganic nitrogen compounds in Phnom Penh city.