Document Type

Thesis

Date of Degree Completion

Summer 2017

Degree Name

Master of Science (MS)

Department

Chemistry

Committee Chair

Dr. Anne Johansen

Second Committee Member

Dr. Dion Rivera

Third Committee Member

Dr. Yingbin Ge

Abstract

Oceanic iron (Fe) fertilization experiments performed in remote regions have established that Fe additions draw carbon into the ocean, at least over the months-long time frame of the experiments. However, the mechanisms that control Fe speciation in atmospheric aerosol particles before and after deposition into the surface ocean remain largely unknown. This is in part due to the analytical challenge of quantifying Fe at environmentally significant sub-nano molar levels. The flow injection analysis method combined with the luminol chemiluminescence analytical system allows us to explore the near-real time determination of pico-molar levels of both Fe(II) and H2O2 produced from real marine aerosol particles collected over the Equatorial Pacific Ocean, as a function of both sunlight and electron donors (EDs) such as dimethyl sulfide and organic acids. Detection limits were as low as 40 pM Fe(II) and 100 pM H2O2. Fe(II)in aerosol concentration was found to be 0.29 ± 1.48 pg m-3 in large, 19.14 ± 18.31 pg m-3 in coarse, 38.80 ± 37.87 pg m-3 in fine, and 43.61 ± 42.93 pg m-3 in ultrafine size aerosol samples. A typical analysis of photochemical reaction with addition of EDs can be performed in five minutes. Results indicate that Fe(III) is reduced in the presence of light with ED that are already present in the collected aerosols, the external additions of ED have an enhancing effect in some of the samples, and the Fe(II) concentration shows positive corrected to non-sea-salt sulfate (NSS-SO42-) and some other anions. Fe(II) is found to be 3% of total Fe in the aerosols. These results contribute to resolving current inconsistencies in chemical models on the speciation of Fe and sulfur cycles in the marine atmosphere.

Share

COinS