Jim McQuaid - Home Page.

Dr. Jim McQuaid.

Research Fellow

email: jimm@chem.leeds.ac.uk
Phone: +44 (0) 113 233 6787

Current Research:

The development of an airbourne instrument for the in situ determination of NMHC, more details can be found here

Previous Work.

"Studies of Tropospheric Chemistry in Urban and Remote Areas." This work studied several aspects of the tropospheric system:
1) In-situ VOC sampling and analysis of data (EASE 96 & 97 campaigns) - goto
2) Spatio-temporal concentrations of atmospheric pollutants - goto
3) Simulated atmospheric reactions using a photo-chemical reactor - goto

BACKGROUND.

The troposphere can be regarded as a continually mixing chemical vessel, with its composition being dependent on a large number of factors such as temperature, position (relative to population centres, industrial areas), solar aspect and weather conditions. Although it represents only a small fraction of the whole atmospheric volume, the troposphere is the region into which most of the anthropogenic and all the biogenic emissions are released. The increasing atmospheric concentrations of species such as carbon monoxide and the oxides of nitrogen are of special importance as they strongly influence the concentrations of ozone and the highly reactive hydroxyl radical, which are responsible for the atmospheric oxidation of many gases including Volatile Organic Compounds (VOCs). In order to test models that can be used to predict the changing concentrations of the primary atmospheric pollutants and the secondary pollutants which they form (nitrogen dioxide, ozone and peroxyacyl nitrates), it is necessary to obtain real measurement of these gases.

Monitoring Hydrocarbons in the marine boundary layer

As part of the ACSOE programme we took part in two campaigns at the University of Galway Atmospheric Field Station located at Macehead on the west coast of Ireland. Our objective was to make continuous speciated hydrocarbon measurements for the duration of the campaigns. We successfully deployed instruments with a detection limit of 5 parts per trillion for both campaigns. In depth analysis of the concentrations present in different air masses has produced many interesting theories including the detection of oilfield emissions. For more info try our EASE results pages.

Spatio-temporal concentrations of atmospheric pollutants

This aspect of my work is to develop a system for measuring a variety of atmospheric pollutants, being capable of being located to remote sites and whilst in motion. From the data collected we plan to construct both spacial and temporal based models. Initial species monitored, along with the method of sampling and the form of detection are presented in Table 1.

Table 1.

Species Monitored.	Sampling Technique	Detection Method
Nitric Oxide (NO)	Manifold	Chemiluminescence
Ozone (O₃)	Manifold	Photometric
Carbon Monoxide (CO)	Manifold	Gas Filter Correlation

Static Sampling Sites.

Sampling sites have been carefully selected with regard to such things as; surrounding topography, road layout and industrial influences. Currently we have a series of motorway sites consisting of a 'c' road crossing the motorway, both under and over. Some of these sites have already been used to gather preliminary data. The concentration data is collected on a minute averaging basis along with basic meteorological data (wind direction, speed and air temperature).

Mobile Sampling and Location Monitoring.

In order to study the urban atmosphere using the mobile lab we must be able to ascertain the position the van at anytime. We will be collecting spacial measurements using GPS (Global Positioning System) to do this. This is a technique which uses an array of satellites orbiting the planet to plot precise locations using triangulation. However, a problem of outage can arise, mainly in built-up areas but especially in city centres due to the presence of significantly taller buildings than can be found in suburban and rural locations. This occurs when the GPS instrument cannot receive from four (fourth is required for a time base correction), of the visible satellites to obtain a fix on its position. Outages can be as much as 50% in a typical urban environment where deep street canyons form a large part of the surroundings. In order to increase the accuracy of the GPS we will be using a differential configuration which increases the positioning accuracy from ą10 m to ą 2 m. DGPS consists of a base receiver at a known position (in our case on top of the School of Chemistry) and a mobile receiver (in the van) both logging their positions, and the error in the position of the fixed receiver can be then combined into the positioning calculations for the van. These differential calculations will be carried out in post processing work. All the collected data will then be imported into a Geographical Information System (GIS) such as ARCVIEW. A GIS is a visual database used to display information e.g. pollutant concentration in which the base level is basicaly a map allowing information to be shown on a spacial basis. I will be working in conjunction with the Leeds Environment Centre who have considerable expertise in the field of GIS.

The Worth Valley

Located on the edge of industrial West Yorkshire, The Worth Valley includes towns such as Keighley and Haworth. It has a very well defined simple geographical layout with steep sides to the valley rising up to the surrounding moorlands. We have recently carried out a preliminary survey of the area using the mobile unit looking at the variations in pollutant concentrations between urban, light industrial, background suburban and rural areas.

Further Work.

There is a great deal of interest currently in the monitoring of atmospheric pollutants. Interesting sites at which to monitor pollution include traffic calming measures such as speed humps and "weaves" commonly used near playgrounds and schools but in slow traffic the levels of pollution increase. We are currently involved with a variety of projects including power station plume chasing with Dr Alison Tomlin from the Department of Fuel and Energy.

Previous Work.

A STUDY OF THE 137 CAESIUM-BINDING PROPERTIES OF A BY-PRODUCT FROM THE FOOD INDUSTRY USED IN RUMINANT DIETS.
(6/95-11/96)

This was a research project conducted jointly with Dr. Stewart Telfer and Dr. Paul Owens from the Department of Animal Physiology and Nutrition here at the university.
After the Chernobyl accident (1986) there was very high contamination of some of the upland areas of Britain, and through grazing on these areas sheep subsequently became contaminated with radio-isotopes (caesium 134 & 137). This work was involved in the use of a by-product from the citric acid industry being extracted using supercritical fluid extraction techniques and subsequent incorporation into a soluble glass bolus suitable to be used with hill grazing sheep.