Progress in the collection of Geogas in China

Geogas surveys have been carried out in China for more than 15 years. Although much valuable experience has been obtained from these studies, little progress (until recently) has been made in understanding the mechanisms involved and in testing procedures. One of the major challenges is to design a collector for the metals in Geogas effectively, using the right medium for complete sorption, without knowing their actual forms. Several absorbers have been tested in China. Almost all solid collectors used in Geogas testing contain variable quantities of metals which are difficult to remove chemically or physically. Thus some of the published data related to Geogas surveys should be re-evaluated. Newly developed liquid collectors, used since 1999, improve the accuracy of the Geogas data because they are low in blank levels, and their use negates the need for time-consuming digestion, the aqueous medium being easily analyzed by inductively coupled plasma-mass spectrometry. With this refinement in collectors, the recent Geogas anomalies obtained in soils over buried mineralization attest to the presence of metals within soil gas and confirm the validity of this technique.