wet deposition of inorganic nitrogen compounds associated with rainfall in phnom penh, cambodia

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 majorinorganic 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.