Concentration And Deposition Flux Of Atmospheric Nitric Acid, Nitrous Acid And Ammonia In Qingdao, China

Nitric acid （HNO₃）, nitrous acid （HNO₂） and ammonia （NH₃） are importantreactive nitrogen compounds in the atmosphere. These acidic and basic gases caninfluence atmospheric photochemical oxidation capacity, change the extent of acidityof atmospheric aerosols, and contribute to atmospheric nitrogen deposition. Qingdaois located at the south of Shandong peninsula, bording the Yellow Sea. The previousstudy of atmospheric reactive nitrogen compounds are limited these speciesdistribution, deposition flux and influence to the ocean in aerosols and rainwater.However, the study of HNO₃, HNO₂and NH₃are muchless, therefore it is importantto study HNO₃, HNO₂and NH₃. The three gases were collected using denuders inspring （from4to13May in2012）, summer （from27June to11July in2012）, autumn（from11September to30November in2012） and winter （from1December in2012to16January in2013）.270atmospheric samples were collected, following bychemical analysis using an ion chromatography.The concentrations of HNO₃, HNO₂and NH₃were in the ranges of0.01μg·m^-3-12.69μg·m^-3,0.03μg·m^-3-8.79μg·m^-3and0.03μg·m^-3-17.49μg·m^-3, respectively. Theresults of paralleling samples collected in spring showed that artifact reactions hadlittle influence on the measured concentrations of HNO₃and NH₃, but had about11.7%influence on the measured vales of HNO₂, and high temperature apparentlyincreased the sampling artifact of HNO₂.The season trend of HNO₃was obvious spring (2.06μg·m^-3)>autumn (1.36μg·m^-3)> winter (0.89μg·m^-3)>summer (0.79μg·m^-3). The concentration of HNO₂waswinter (2.15μg·m^-3)>autumn (1.67μg·m^-3)>spring (0.92μg·m^-3)>summer （0.49μg·m-3）. And the season trend of NH₃was obvious summer (6.17μg·m^-3)> autumn (4.39μg·m^-3)> spring (3.03μg·m^-3)> winter (1.85μg·m^-3).Statistically significant differences （p<0.05） were observed between daytime andnighttime of HNO₃concentrations in summer and autumn, were1.67times and0.74times higher concentrations in daytime than nighttime, but the differences were not observed in spring and winter. Statistically significant differences （p<0.05） wereobserved between daytime and nighttime in autumn and winter, were0.35times and0.84times higher concentrations in nighttime than daytime, the differences were notobserved in spring and summer. No statistically significant differences （p>0.05） wereobserved between daytime and nighttime of NH₃concentrations in spring, autumn andwinter, the concentrations of NH₃in nighttime (6.18μg·m^-3) were equel to thedaytime (6.17μg·m^-3) in summer.Concentrations of these three gases were found to be related to weatherconditions and air mass sources. The highest concentration of HNO₃occurred insunny day, followed by fog and haze day and the lowest in rainy day. HNO₂had thehighest concentrations in haze day, follwed by fog day, the lower concentrations insunny and rainy day. The higher concentration of NH₃also occurred in haze and fogday, followed by rainy and sunny day. The concentrations of HNO₃appeared to beindependent on air mass; however the air mass from the north yielded the highestconcentration of HNO₂, while the air mass from the south gave the highestconcentration of NH₃.In addition, the concentration of HNO₃had a positive correlation withtemperature, and a negative correlation with relative humidity in spring and summer.NH₄NO₃could decompos at high temperatures and low humidit. However, highrelative humidity and rainfall enhanced remove of HNO₃from atmosphere. Under ahigh wind speed, long-range transport of air could carry these gases from the north tosampling site. Local emissions were likely the main sources of HNO₂in Qingaoatmosphere, low wind speed favored accumulation of HNO₂in the atmosphere. Theanalysis results showed that the main sources of NH₃were from local emissions, lessthan23%,5.6%,21%and41%from dissociation of NH₄NO₃and NH₄NO₂in spring,summer, fall and winter in Qingdao. Low wind speed led to accumulation of NH₃inthe atmosphere. The concentrations of NH₃increased during high temperature andrainy because of the enhancement of soil release. However, when there wascontinuous rainfall, the concentration of NH₃decreased because of wet deposition.The dry deposition fluxes of HNO₃and NH₃in Qingdao were on average11.8μmol·m^-2·day^-1and23.6μmol·m^-2·day^-1, respectively. The dry deposition fluxes ofgaseous nitrogen （HNO₃and NH₃） were higher1.29times than particulate nitrogen（NO₃^-and NH₄⁺） over the Yellow Sea. If wet deposition fluxes of particulate nitrogen（NO₃^-and NH₄⁺） were included, the ratio of gaseous nitrogen （HNO₃and NH₃） with particulate nitrogen （NO₃^-and NH₄⁺） was0.37. Therefore, about27.2%ofatmospheric nitrogen compounds were underestimated for nitrogen fluxes to ocaen.