Search the EPA Research Database

Project title

SPectroscopic Investigation of the Climatic Effects of Ultraviolet-absorbing Particles (SPICE-UP): a method-development and field-observation study

Primary Funding Agency

Irish Research Council

Co-Funding Organisation(s)

Environmental Protection Agency

Lead Organisation

University College Cork (UCC)

Lead Applicant

Diarmuid Moynihan

Project Abstract

The climate effects of absorbing atmospheric particles are comparable to that of methane, the most important greenhouse gas after carbon dioxide. While sooty aggregates (Black Carbon, BC) are responsible for most particle light absorption, emerging evidence indicates that absorption by certain organic compounds increases sharply at blue and ultraviolet wavelengths and can be significant. In addition to climate, light absorption by this so-called Brown Carbon (BrC) also influences atmospheric oxidation processes which are largely driven by ultraviolet light. However, the magnitude of ultraviolet absorption is poorly understood. This is because current instrumentation is limited to longer ultraviolet wavelengths and some techniques can modify particle properties. The first step to improving our understanding of ultraviolet properties of particles is to address this methodological gap. This project will do so by developing a novel spectrometer to characterise short wavelength particle absorption in real time, in situ measurements. The spectrometer will use optical cavities and photometric detection to achieve long effective light paths and high sensitivity to particle extinction (absorption plus scattering) with concurrent measurement of particle scattering, allowing sample absorption to be retrieved. Light emitting diodes will be used to determine the wavelength dependence across the 300 to 400 nm region, with a particular focus on wavelengths below 350 nm where measurements are almost non-existent. The spectrometer will be tested in an atmospheric simulation chamber to study the effect of atmospheric aging on the optical properties of biomass burning products. Work in the group I am joining has shown that some of these compounds have extremely high absorption and could affect atmospheric photochemistry and radiative balance. Field observations using the instrument will be used to characterise the absorption of rural and urban ambient particles in Ireland and demonstrate the value of the approach.

Grant Approved

�110,000.00

Research Hub

Climate Change

Research Theme

n/a

Start Date

01/12/2021

Initial Projected Completion Date

30/11/2025