Study of relationship between water-soluble Ca2+ and lidar depolarization ratio for spring aerosol in the boundary layer

The backscattering ratio, depolarization ratio and water-soluble ions of aerosols inside the boundary layer were measured by a depolarization lidar and an in situ ion chromatography (IC) in the spring of 2004 and 2005. To study the relationship between depolarization and aerosol compositions, depolarization ratios were compared with mixing ratio of soluble ions like calcium, potassium, and sodium from surface ground measurements. About 70% of the daily maximum depolarization ratios were distributed between 1.5% and 3.5% with a mean value of 2.14±0.83%. High correlation coefficients (R>0.8) were found between depolarization and ion calcium for all of the depolarization episodes (DP≈5–12%), which suggest the existence of mineral dust. As the tracer of biomass burning and sea salt, the mixing ratio of K+ and Na+ usually are greater than Ca2+ but did not show dependences with depolarization implying that biomass burning and sea salt aerosols may transport along with Asian dust but not exhibit significant non-spherical properties.