How to Improve Prediction of Risk from Ground VOCs Using in-Borehole Gas Monitoring

Abstract

Volatile organic compounds (VOC’s) have a variety of negative impacts on human health (Harold, 1998;
Barbara et al, 2007), some (e.g. benzene and formaldehyde,) are known to be human carcinogens (IARC,
2004). There is, therefore, often a pressing requirement to monitor these compounds. However,
monitoring these compounds is not straightforward as their concentrations vary with environmental
parameters such as temperature, barometric pressure and groundwater movement. Because of this, the
sampling frequency that is used at present is ineffective for determining their representative concentration;
therefore, a device which can be left in-situ to collect high temporal resolution data has been developed
(Gasclam, Ionscience, UK). VOC’s are measured by Photoionisation detector (PID), however; PID measures
aggregated VOC concentration. Because VOC’s have differing toxicities and behaviours, individual
identification is required, therefore, a sample must be collected. In order to do this, a sorbent material
must be used to transfer the sample to the GC-MS for identification. The sorbent material must be
appropriate for the range of VOC’s and of sufficient capacity for extended exposure (BS EN ISO 16017-
1:2001). To solve these problems, an optimum VOC monitoring methodology known as dual measurement
VOC monitoring has been developed following the incorporation of a suitable sorbent into the latest inborehole
monitoring device, the Gasclam (Ionscience, UK).