Investigating Anthropogenic Impacts on Central Greenland Ice-core Nitrate Using Isotopic Composition of Nitrate

Author

• Lei Geng

Document Type

Dissertation - University Access Only

Award Date

2012

Degree Name

Doctor of Philosophy (PhD)

Department / School

Chemistry and Biochemistry

First Advisor

Jihong Cole-Dai

Abstract

The atmospheric oxidation capacity, represented by the abundance of tropospheric oxidants of 0 3 and OH radicals, regulates the levels of environmentally important trace gases (e.g., CH4) and gaseous pollutants (e.g., CO, SO2, volatile organic compounds) in the atmosphere. Human activities, through emissions of important precursors of 0 3 and OH, have affected and will probably continue to affect the oxidation capacity. Knowledge of the past variations of the oxidation capacity or of the tropospheric oxidants is needed to model their future development and to predict the impact on the global atmospheric environment. Unfortunately, measurements of the short-lived oxidants began only recently and the records are very short. Longer history will need to be found in . proxy records including ice cores. The production of atmospheric nitrate and its subsequent deposition and preservation in polar ice sheets provide a potential natural archive containing information regarding past atmospheric oxidation capacity because 1) the precursor of nitrate, nitrogeri oxides (NOx =NO+ NO2), affect atmospheric oxidation capacity through the interactions with the oxidants, and 2) the oxygen-17 excess (~ 17 0) of nitrate is indicative of the relative abundance of atmospheric oxidants (OH, 03) and has been proposed as a proxy to reconstruct atmospheric oxidation capacity. Since the beginning of the industrial revolution ( around 1850), human activities have gradually and steadily changed the atmospheric environment including the concentrations ofNOx and oxidants through anthropogenic emissions of environmentally important gases such like NOx and oxidant precursors. These changes have altered the atmospheric nitrate production as well as the isotopic composition (