环境放射性核素137Cs和210Pbex的田间原位测定研究

原位现场γ谱仪具有快速准确监测土壤中环境放射性核素137Cs和210Pbex的潜力,可以解决传统环境放射性核素示踪土壤侵蚀在选择参考点和测定时间过长问题。本研究应用现场γ谱仪(ISOCS,In-situObject Counting System),对内蒙古锡林浩特草原土壤中137Cs和210Pbex的含量进行了田间原位(不采样)测定,并与室内γ谱仪测定结果进行了比对。结果显示:现场γ谱仪的探头离地面1m,采用90度准直器,测量时间保证3600s以上时,测定的土壤中137Cs面积浓度与室内测定结果一致,二者的平均偏差为8%,表明现场γ谱仪测定具有较高精度,是快速评价土壤侵蚀速率的有效技术;210Pbex的原位测定结果显著高于室内测定结果,可能由于测定时间较短所致。初步研究结果表明:原位测定具有时间短、精度高的优点,可以克服传统采样造成的空间变异误差。

FIELD MEASUREMENTS OF ENVIRONMENTAL RADIONUCLIDES ~(137)Cs AND ~(210)Pb_(ex) INVENTORIES USING IN-SITU GAMMA-RAY SPECTROMETRY

In-situ measurement of environmental radionuclides()~(137)Cs and ()~(210)Pb_(ex) has a potential to assess soil erosion and sedimentation rapidly.In this study,we measured the inventories of()~(137)Cs and()~(210)Pb_(ex) in the soil of Inner Mongolia grassland using an in-situ gamma detector with the 50 mm shield and Collimator mounted on a cart(ISOCS,Insitu Object Counting System).The detector was set up one meter above the ground with 90° collimator installed: the counting time is more than 3600s.The field survey data were compared with data from laboratory analysis of section cores.The results showed that the mean deviations of measured values between field and laboratory measurements are less than 8%,indicating a high precision for in-situ gamma spectrometry.The inventories of()~(210)Pb_(ex) measured by in-situ γ spectrometry were much higher than the laboratory measurements due to a short measurement time in the field.The results from our pilot study indicated that in-situ gamma-ray spectrometry has the following advantages over traditional laboratory measurements: no time consuming sample collection,prompt availability of the results,averaging radionuclide activity over a large area and high precision.