泵吸式土壤测氡仪气压校正方法的初步研究

Study on pressure correction method of radon in soil detecting instrument with pump

泵吸采样过程中,当土壤透气性差时,实际采样到的土壤气进气量将不同程度偏小,引起收集室内气体被扩张,气压降低,影响氡浓度测量结果。根据密闭容积气体特性,可以推导出气压校正系数,校准泵吸式测氡仪进气量难以预计引起的测量误差。为验证校正效果,设计制作了带气压校正器的便携瞬时土壤测氡仪,已获国家专利。两条剖面实验数据表明,校正后氡浓度测量结果更接近理论值,且由进气量原因引起的平均相对偏差高达60%,可用该项校正技术解决。

In the case of breathless soil, the real sample quantity of soil gas will be less than expected. Thus it results in higher error with radon concentration result. The pressure in the collecting chamber will be reduced while air expanding during pumping due to the breathless soil According to the characteristic of air in a tight chamber, the coefficient for error correcting is derived. This method was carried out for sniff-typed radon detector calibration, so as to avoid error caused by unexpected sample quantity of soil gas. For a verifying purpose, a portable instantaneous radon in soil detecting instrument with pressure corrector was then developed. An item of Chinese Utility Model Patent was also awarded. Experiment data has been collected on two geological sections. It shows that relatively error, which caused by various sample quantity of soil gas, would be up to 60%. Therefore, good results were achieved after the pressure correcting method had been applied.