| With the development of economy and the increase of population,a large number of fossil fuel combustion,vehicle emissions lead to nitrogen atmosphere surged.Nitrogenous substance composition of the reactive nitrogen emissions to the atmosphere impacts on the ecological environment and human health.Though the increase of reactive nitrogen such as chemical fertilizer,provides the human food security,large amount of reactive nitrogen transfer to land water,and atmosphere lead to soil acidification,eutrophication and biodiversity reduction and a series of environmental problems.The Taihu Lake Region(TLR)is one of the most economically developed areas in China.With the speeding up of urbanization,the TLR city scale expands unceasingly,rising population,energy consumption increases rapidly,motor vehicle number increases year by year,these factors make the TLR reactive nitrogen atmosphere pollution levels more and more serious.This study selected the TLR typical urban,suburban and rural as three sampling points.The monitoring was conducted during March 2014 to February 2014.Gaseous reactive nitrogen concentration and particle state was analyzed by the spatial and temporal variation,and all the influence factors such as temperature,rainfall of reactive nitrogen atmosphere were discussed.The results are as follows:(1)Mean atmospheric NH3 concentration in the TLR was 21.67 ?gN·m-3,and mean concentration of NH3 in Suzhou,Changshu,Yixing three sampling sites were 14.50,17.16,33.34 ?gN·m-3 respectively;Mean atmospheric HNO3 concentration in the TLR was 6.11?gN·m-3,and mean concentration of HNO3 in Suzhou,Changshu,Yixing three sampling sites were 6.67,6.71,4.96 ?gN·m-3 respectively;Mean atmospheric NO2 concentration in the TLR was 6.90 ?gN·m-3,and mean concentration of NO2 in Suzhou,Changshu,Yixing three sampling sites were 7.87?8.85?3.98 ?gN·m-3 respectively;the whole atmospheric gas reactive nitrogen(NH3,HNO3,NO2)in urban,rural and suburban were 29.05,32.72,42.28?gN·m-3 respectively.All data above indicate heavy gas reactive nitrogen pollution in the TLR.(2)Atmospheric NH3 concentration in the TLR was affected by human activity obviously.Nitrogen fertilizer application increased the local atmospheric concentrations of NH3 significantly,and rainfall?temperature had significantly influence on atmospheric NH3 concentration at each sample site.The agricultural source of ammonia emissions is a major cause of high concentrations of atmospheric NH3 in this region,thus reduce ammonia emissions from its source is the most effective measures to reduce the concentration of NH3 in the atmosphere.Rural atmospheric HNO3 concentration was lower than those in the cities and suburbs,but not significantly.Industry and transport were the main sources of NOx in urban sites,and nitrogen application also contributed to NOx emission partly in rural area,owing to the joint effects of agriculture and industry.Suburban areas should become the focus site in this region for controlling the nitrogen pollution;factors such as rainfall,temperature and other meteorological factors on HNO3 and NO2 concentration in the atmosphere in this region were not significant.(3)Mean atmospheric particles concentration of NH4,in the TLR was 7.82 ?gN·m-3,and 6.31,8.75,8.41 ?gN·m-3 in Suzhou,Changshu,Yixing three sampling sites respectively.Mean atmospheric particles concentration of NO3-in the TLR was 5.03?gN·m-3,and 4.40,5.50,5.19 ?gN·m-3 in Suzhou,Changshu,Yixing three sampling sites respectively.Mean atmospheric particles concentration of DON was 2.07 ?gN·m-3,which was obtained by minusing,and 2.21,1.92,2.09?gN·m-3 in Suzhou,Changshu,Yixing three sampling sites respectively.The total atmospheric particle state reactive nitrogen in urban,suburban and rural were 13.47,16.17,15.58 ?gN·m-3 respectively,and it had no significant difference in urban,suburban and rural sites.(4)Under the background of NH3 concentration higher in TLR,acid gases in the atmosphere is a main factor particles state of NH4+,three sampling sites particle concentration of NH4+,HNO3 and acid gas have varying degrees of positive correlation;Particle state NH4+ concentration and temperature showed negative correlation with temperature,because of temperature promoted the particles in the atmosphere the NH4+decomposition;Atmospheric particles state of NO3-concentration were negative correlation with temperature,as the high temperature made the secondary aerosols,such as NH4NO3 and Ca(NO3)2,easy to decompose,so that reduced the concentration of particle NO3-in the atmosphere.Rainfall has certain scavenging impact on atmospheric particles NO3-as well.There were good linear relationship between particles state NO3-and particle state NH4+ in the three sampling sites,which illustrated that NH4NO3 may be the main existence form of particles NO3-under the condition of high concentration in the TLR.The concentration of DON in winter was higher than other seasons,because under the condition of low temperature dust could react with NOx or NH3 to produce organic nitrogen,a number of fertilizer volatilize to the atmosphere directly under the condition of high temperature in summer,therefore,to guide farmers reasonable arrangement of fertilization time is particularly important.(5)In the TLR,the proportion of TN in DON was from 0.25%to 29.71%,it showed obvious seasonal variation and regional differences in urban,suburban and rural.The DON proportion in summer and winter was higher than that in spring and autumn,the DON proportion in Yixing sampling site was lower than those in Suzhou and Changshu,which indicated that the organic nitrogen emissions in urban or suburban was higher than that in rural area,it was obvious that exhaust from cars and industries made the significant contribution to the atmospheric organic nitrogen.It showed nondeterminacy in calculating atmospheric concentration of DON by minusing,therefore,further research needs to be done to make further understanding of atmospheric pollution situation of DON in the TLR... |
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