School of Natural and Environmental Sciences


Source variability of water-soluble organic carbon in atmospheric precipitation


Water soluble organic carbon is a suite of organic molecules that readily dissolve in rainwater.  WSOC can assist cloud formation and rainwater acidity.  A large WSOC fraction fluoresces when stimulated by light, potentially yielding valuable WSOC 'source fingerprints'.  In this project rainfall fluorescence properties were combined with meteorological and air-mass back-trajectory data to identify likely WSOC source regions. The aim was to better understand the origin and fate of WSOC. 

Project description

A suite of natural and man-made organic molecules that readily dissolve in water are collectively known as WSOC (water soluble organic carbon). WSOC is an important, reactive constituent of rainwater. It can also be an important source of cloud condensation nuclei (CCN), it contributes to rainwater acidity, and it can be a nutrient source to lakes, rivers and the ocean.  

Some WSOC components are thought to be photo-reactive, potentially influencing atmospheric chemistry both locally and globally. Recent global trends of increasing rainfall prompt a need for detailed WSOC study.

While in-depth chemical analysis of WSOC is costly, a large fraction of WSOC fluoresces when stimulated by incident radiation of the appropriate wavelength. Emitted wavelength spectra might be valuable and distinct WSOC 'fingerprints' providing WSOC source information.  Fluorescence measurements are simple and low cost.

This project targeted specific rainfall 'events' and examined their fluorescence properties. Combining these with meteorological data from an adjacent meteorological mast and predictions of air-mass back-trajectories, it is theoretically possible to identify the regions from which the fingerprinted WSOC originated.

This is an important first step towards better understanding the origin and subsequent fate of WSOC in the environment. Results from projects such as this can help in formulating more detailed future programmes of WSOC research.