南京地区^7Be沉降特征

DEPOSITIONAL FLUXES OF ~7BE AT NANJING REGION

7Be是研究大气科学与地球化学的核元素之一,对研究短期过程的地表土壤颗粒迁移具有较大价值。为了解南京地区利用7Be进行土壤侵蚀示踪研究的合适时机,于2010年1月～2011年12月收集南京地区各月的7Be沉降样品,经实验室化学实验处理和γ谱仪测量,计算7Be沉降通量,并分析7Be大气沉降的季节性变化趋势。结果表明:南京地区平均7Be沉降量为1 621.78Bq/(m2·a),沉降通量为0.66～14.49Bq/(m2·d),平均沉降通量为4.44Bq/(m2·d);7Be沉降通量的季节变化呈现双峰型趋势,冬末春初和夏季是两个高值区;7Be沉降的а值冬春季较大,夏季最低;降雨量大小与沉降量存在明显的正相关。

7Be which is one of the most investigated radionuclides in the atmosphere has wide applications in meteorology and geochemistry.It also has been a useful tracer for documenting soil erosion rates over much shorter timescales.In order to find the suitable time of soil erosion by using 7Be tracer in Nanjing region,monthly atmospheric deposition samples of 7Be were collected from January 2010 to December 2011.Deposition samples were experimented to obtain residual samples which was followed by measurement with a HPGe detector for 7Be.Deposition fluxes and seasonal variation pattern of atmospheric deposition of 7Be were analyzed.The results showed that the depositional fluxes of 7Be ranged from 0.66 to 14.49 Bq/（m2·d） and a mean value was 4.44 Bq/（m2·d）,annual average depositional fluxes were 1 621.78 Bq/m2.The seasonal variation of depositional fluxes of 7Be showed double peaks,higher flux value was in late winter and early spring,another higher flux value was in summer.The fractor of precipitation-normalized depositional fluxes of 7Be were higher value in winter and spring,but the minimum value was in summer.Furthermore,a positive correlation between the 7Be fluxes and precipitation was observed in this study.