Because of these fluctuations, estimating the annualmeanconcentration of radon in indoor air requires measurements of mean radon concentrations for at least three months.
鉴于这种起伏，估算室内空气中氡的年平均浓度需要对氡的平均浓度至少进行三个月的测定。
2
Air quality is represented by annualmeanconcentration of fine particulate matter (PM10 and PM2.5, i.e. particles smaller than 10 or 2.5 microns).
Construction fugitive dust showed great impact on the ambient PM10 level in Guiyang, and contributed 12% to the annualmeanconcentration of PM10 over the urban area.