Argon is also one of the densest of the atmospheric gases. It has a density of 1.78 kg/m3 , which is just 10% less than that of carbon dioxide (1.98 kg/m3). Carbon dioxide readily accumulates and often displays pronounced seasonal variations in cave air concentration and distribution.
|
Argon (Ar) is the most abundant of the heavier-than-air gasses found in cave atmospheres, and like CO2 and radon (Rn), it should have the potential to accumulate in areas with restricted air flow.
Argon's density is among the highest and it's rate of diffusion the lowest of all the principal gases in cave atmospheres, so it seems logical that it may have the tendency to accumulate. Argon has a very low rate of diffusion, which is the primary factor for predicting gas accumulation. Gaseous rates of diffusion are compared by their respective diffusion coefficients. Assuming an average cave temperature of 10C (50F), argon's diffusion coefficient is 0.173 cm2/s, which is only 18% higher than that of CO2 (0.147 cm2/s). Overall, it is the third lowest after radon (0.104 cm2/s) amongst common cave-air gases. |