相对湿度对光散射法测定大气细颗粒物浓度的影响

目的探讨相对湿度对光散射法测定大气细颗粒物(PM2.5)浓度的影响。方法在2010年冬季和2011年夏季分别用光散射法和滤膜称重法对大气PM2.5浓度进行24d平行测定,同时收集采样期间的相对湿度数据,分析比较不同相对湿度对光散射法测定大气PM2.5浓度的影响。结果采样时期光散射法测定结果与滤膜称重法结果呈统计学相关(r=0.948,P<0.001),但是两种测定方法结果的一致性随着相对湿度的变化而改变。相对湿度<50%时,两种方法的测定结果差异无统计学意义(P=0.114);相对湿度>50%时,光散射法测定结果与滤膜称重法结果差异有统计学意义(P=0.001),且两种方法的测定结果比值与相对湿度呈正相关(r=0.894,P<0.001)。结论相对湿度>50%会对光散射法测定大气PM2.5的准确性造成影响,因此在采用光散射法测定大气PM2.5浓度时应考虑采样期间相对湿度的影响。

Effect of relative humidity on concentration of ambient fine particles measured by light-scattering method

Objective To investigate the effect of relative humidity on concentration of ambient fine particles(PM2.5) measured by light-scattering method.Methods Both Light-scattering and gravimetric sampling methods were used simultaneously to measure the ambient PM2.5 concentrations in the winter of 2010 and summer of 2011 for 12 consecutive days of each period.Data of real-time relative humidity of every sampling day were also collected.Results PM2.5 levels measured by light-scattering and gravimetric sampling methods were significantly correlated with each other in the sampling period(r=0.948,P<0.001).However,the consistency of the two methods changed as the relative humidity varied.When relative humidity was lower than 50%,there were no big differences between(P=0.114);but when it was higher than 50%,the differences were statically significant(P=0.001).The ratios of concentrations measured by these two methods were positively correlated with relative humidity(r=0.894,P<0.001).Conclusions Relative humidity higher than 50% can greatly affect the accuracy of PM2.5 concentration measured by light-scattering method.Therefore,relative humidity should be taken into account when light-scattering method is used to measure the concentrations of ambient PM2.5.