Dominant Contribution\nof Non-dust Primary Emissions\nand Secondary Processes to Dissolved Aerosol Iron

Solubility largely determines the impacts of aerosol\nFe on marine\necosystems and human health. Currently, modeling studies have large\nuncertainties in aerosol Fe solubility due to inadequate understanding\nof the sources of dissolved Fe. This work investigated seasonal variations\nof Fe solubility in coarse and fine aerosols in Qingdao, a coastal\ncity in the Northwest Pacific, and utilized a receptor model for source\napportionment of total and dissolved aerosol Fe. Desert dust was found\nto be the main source of total Fe, contributing 65 and 81% annually\nto total Fe in coarse and fine particles, respectively; in contrast,\ndissolved aerosol Fe originated primarily from combustion, industrial,\nand secondary sources. The annual average contributions to dissolved\nFe in coarse and fine particles were 68 and 47% for the secondary\nsource and 32 and 33% for the combustion source, respectively. Aerosol\nFe solubility was found to be highest in summer and lowest in spring,\nshowing seasonal patterns similar to those of aerosol acidity. Increase\nin Fe solubility in atmospheric particles, when compared to desert\ndust, was mainly caused by secondary processing and combustion emission,\nand the effect of secondary processes was dictated by aerosol acidity\nand liquid water content.