三江平原典型湿地系统大气湿沉降中氮素动态及其生态效应

Dynamics of nitrogen in the atmospheric wet deposition and its ecological effects in typical wetland ecosystem of Sanjiang plain

  • 摘要: 2004年7月至2005年6月对三江平原典型湿地系统大气湿沉降中的氮素动态进行了研究,并探讨了其生态效应。结果表明,各形态氮月均浓度之间差别较大,具有明显的季节性,原因主要与人类活动、降水强度及频次、风向、地理位置以及氮氧化物自然排放有关;湿沉降的TN组成以TIN为主(51.38%~98.96%),TIN又以NH4+-N和NO3--N特别是NH4+-N为主,降水天气系统的路径在很大程度上影响着降水中各形态氮的组成;降水量与各形态氮浓度均呈较弱的负相关(p>0.05),而NH4+-N与NO3--N、TON均呈显著正相关(p<0.05),它们可能具有同源性。NH4+-N与NO3--N的良好相关性与其在液相中的反应有关;生长季是全年氮沉降的重要时期,其TN沉降量为非生长季的1.84倍,二者所占比例分别为64.78%和35.22%。除NO2--N外,其它各形态氮的沉降量均以生长季为主体;全年TN沉降量为7.57 kg/hm2,TIN/TON之比为5.47,TIN为沉降主体,占84.56%。NH4+-N和NO3--N是TIN沉降的主体,其所占全年的比例分别为52.55%和30.03%;氮是该区植物生长的限制因素,生长季的氮沉降对于促进植物生长直接生态意义重大,而非生长季的氮沉降对于大量补充次年植物生长初期所需养分的间接生态意义明显,其生态作用不容忽视;近年来湿地系统氮沉降量的降低可能是导致其退化的重要原因,其生态影响也不容忽视。

     

    Abstract: The dynamics of nitrogen(N)in the atmospheric wet deposition in typical wetland ecosystem of Sanjiang plain was studied from July 2004 to June 2005,and its ecological ef ects were also analyzed. The results show that there are significant differences among monthly average N concentrations,and the seasonality is evident. The reasons are mainly correlated with human activities,precipitation intensity and frequency,wind direction,geographical location and NOx natural emission. The total inor ganic nitrogen(TIN)is the main body of the total nitrogen(TN)in wet deposition(51.38%~98.96%),and the ammonium nitrogen(NH4+-N),nitrate nitrogen(NO3--N),especially NH4+ N,are the main body of TIN. The path of precipitation synoptic system,to a greatextent,affects the composition of N in wet deposition. The precipitation only has faintish negative correla tions with N concentrations(p>0.05),but the NH4+-N has significant positive correlations with NO3--N and TON(p<0.05), and they might have homologue. The better correlation between NH4+-N and NO3--N is mainly related with their reactions in liquidoid. The growing season is the important phase of N deposition in a year,its deposition amount is 1.84 folds of that in non growing season,and their proportions are 64.78% and 35.22%,respectively. The deposition amounts of N in growing season are much higher than those in non growing season except nitrite nitrogen(NO2--N)The total N deposition amount in a year is 7.57 kg/hm2,and TIN/TON ratio is 5.47. These show that TIN is the main deposit ion body and its proportion is 84.56% Moreover, NH4+-N and NO3--N are the main body of TIN,and their proportions are 52.55% and 30.03%,respectively Further analysis indicates that N is the limited factor that affects the growth of plant. The N deposition in growing season has direct ecological signification which might stimulate the growth of plant,but in non growing season,the N deposition has indirect ecological signification which can greatly supplement the nutrient in initial growth stage of plant in the second year.Anyhow the ecological func tions can not be neglected. In recent years,the decrease of N deposit ion amount in wetland ecosystem might be the important cause which induces the wetland degradation,nor can its ecological effects be neglected.

     

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