Dr Graham Nickless - Research Interests
An understanding of the processes involving the movement of both natural and
anthropogenic compounds through the various phases comprising the biosphere
rest upon the ability to monitor such movement. The process of monitoring implies
the ability to measure such compounds at a regular number of time intervals. In
this group we are developing ways to determine the very low levels of such
compounds as they move through the environment. The techniques of chromatography,
atomic spectroscopy and mass spectroscopy have revolutionised our understanding
of these movements over the last two decades.
Determination of Trace Atmospheric Pollutants
In recent work, we have developed methods for the determination of many of the
hydrofluorocarbons (HFCs), the replacements for the CFCs of ozone destruction fame.
However, because of the properties, the HFCs are not amenable to the GC/ECD techniques
used for the CFCs. Because the HFCs will be present in ambient air at low parts per
trillion, we have had to develop concentration, chromatographic and mass spectrometric
techniques for their determination. The simple olefins, such as ethene, propene, as well
as conjugated dienes such as butadiene, can be precursors to the toxic peroxy-acylnitrates
(PAN) by reaction with NO2. The determination in air of such simple olefins represents a
serious challenge to the analytical chemist. The development of a reactor/gas chromatographic
system based on the addition of bromine to the double bonds forms the basis of the method for
the determination of 100 vapour parts per trillion in the C3 to C6 series. Similar investigations
are in progress to (a) determine the Halons and other low molecular weight brominated
compounds and (b) the natural sulphur compounds such as dimethylsulphide (DMS) or
methylthiol (MeSH).
Biogeochemical Cycling of Heavy Metals
The speciation of biogeochemical cycling of metals following absorption by soils and
sediments is a major topic for environmental study. The interaction of heavy metals like
cadmium, copper, lead and zinc with the iron/manganese oxide phase or the organic material
(fulvic or humic acids) is being studied particularly at suitably chosen sites, such as
Avonmouth, Mendips and Ringinglow (Sheffield). The techniques involve sequential extraction
using a variety of reagents and atomic spectroscopy. A detailed investigation of the fate of
selenium discharged into a river system has been made. The interchange of various valencies from
Se(-II) to Se(VI) has been studied using a novel derivitization method followed by GLC/ECD for
the low levels encountered.
References: J. of Chromatography, 630, (1993) 264-270.