A new method for measuring ²²⁴Ra in sediments is established by use of a pulsed ionization chamber (PIC). Based on the difference in their half-lives, ²²⁰Rn can be distinguished from ²²²Rn so that one can easily measure ²²⁴Ra and its parent ²²⁸Th in sediment samples. Results show that the measurement efficiency is 0.22 ± 0.02 cpm/dpm, and is not readily affected by moisture. At an optimum airflow rate of 1.2 L/min, the precision of the ²²⁴Ra and ²²⁸Th measurements is estimated at ±8%. Based on controlled experimental field application and a field application, we show that the ²²⁴Ra/²²⁸Th disequilibrium in sediments can be assessed and both ²²⁴Ra deficits and ingrowth to equilibrium may be quantified. The PIC device is simple to use, inexpensive and portable, making it especially suitable for determinations of sediment samples in the field.

使用脉冲电离室 (PIC) 建立了一种测量沉积物中²²⁴ Ra的新方法。根据其半衰期的差异，可以将^{220 Rn 与222} Rn区分开来，从而可以轻松地测量沉积物样品中的²²⁴ Ra 及其母体²²⁸ Th。结果表明，测量效率为0.22±0.02 cpm/dpm，不易受水分影响。在 1.2 L/min 的最佳气流速率下，²²⁴ Ra 和²²⁸ Th 测量的精度估计为 ±8%。基于受控实验现场应用和现场应用，我们表明²²⁴ Ra/ ²²⁸可以评估沉积物中的不平衡，并且可以量化^{224 Ra 不足和向内生长达到平衡。}PIC 设备使用简单、价格低廉且便于携带，特别适用于现场测定沉积物样品。