Variation in characteristics of air concentrations of NH3, NO2 and O3 induced by applications of urea in soils of plastic greenhouses in suburban China

Özet

Few studies have been carried out so far for measuring concentrations of NH3, NO2 and O3 in plasticgreenhouses. In this study, NH3, NO2 and O3 concentrations were measured with passive sampler technologyin a plastic greenhouse located in the Changsha suburb in southern China over a one and a halfmonth period (November 30, 2008 to January 11, 2009). Soil in the greenhouse was subjected to fourtreatment (T) types (no N fertilizer T1, common urea T2, coated urea T3 and common urea with nitrificationinhibitor dicyandiamide (DCD) T4. The average concentrations (mg/m3) of NH3, NO2 and O3 in descendingorder was: T4 (31.66) > T2 (25.93) > T3 (23.52) > T1 (7.96), T2 (10.99) > T3 (8.16) > T4 (7.48) > T1 (5.20), T2(75.05) > T3 (64.20) > T4 (63.85) > T1 (49.02), respectively. This implied that photochemical reactions tookplace and that harmful gases accumulated after application of N fertilizer in the plastic greenhouse. DCDinhibited the conversion of ammonium to nitrate, increased NH3 volatilization and decreased NO2 level.The coated urea decreased the emissions of NH3 and increased nitrogen use efficiency. We found significantpositive correlations (p < 0.01) between temperature and both NH3 and NO2 levels. Correlations betweensoil pH and both NH3 and NO2 concentrations were also significant (p < 0.01). The O3 average concentrationfrom March 31, 2009 to April 10, 2009 in the higher latitude of the Yinchuan suburb in northern China wastwo times greater than that in the Changsha suburb in southern China. The O3 daily concentrations in theYinchuan suburb exceeded 160 mg/m3 (i.e., China's Grade I standard), and the maximal value 214.83 mg/m3exceeded 200 mg/m3 (i.e., China's Grade III standard).