The effects of haze on dew quality in the urban ecosystem of Changchun, Jilin Province, China.

Dew samples were collected during both normal weather and haze events (hazy days) to investigate the chemical characteristics of dew in Changchun, Jilin, China, from 2013 to 2015. The analysis included measures of the following parameters: pH, electrical conductivity (EC), total dissolved solid (TDS), and the concentration of PM2.5, PM10, major cations (NH4(+), Na(+), K(+), Ca(2+), and Mg(2+)), and major anions (F(-), Cl(-), SO4 (2-), and NO3(-)). The results demonstrated that dew water quality from hazy days was much lower quality than that on normal days with a lower mean pH during hazy days (5.75) when compared with that of normal days (6.56); that is, dew water was more acidic in stable atmospheric conditions. Both EC (542.71 μs/cm) and TDS (271.36 mg/L) of dew on hazy days were higher than that on normal days. The mean concentration of particulate matter <2.5 and 2.5-10 μm in diameter (PM2.5 and PM10, respectively) was 21.69 and 51.56 mg/L on normal days and were over 2.48 and 1.79 times higher on hazy days, respectively; that is, dew removed more fine particles on hazy days. On hazy days, the concentrations of water-soluble ions were 3.01-9.32 times higher than levels on normal days. The concentrations of secondary species and K(+) on hazy days were much higher than those of other ions. The results indicated dew mainly removed aerosols from automobile exhaust, and industrial waste gas emissions, while to a lesser extent dew did scavenge some water-soluble crustal ions.