Naturally occurring isotopes of radon in indoor air are identified as the second leading cause of lung cancer after tobacco smoking. Radon-222 (radon gas) and radon-220 (thoron gas) are the most common isotopes of radon. While extensive radon surveys have been conducted, indoor thoron data are very limited. To better assess thoron exposure in Canada, radon/thoron discriminating detectors were deployed in 45 homes in Fredericton and 65 homes in Halifax for a period of 3 months. In this study, radon concentrations ranged from 16 to 1374 Bq m(-3) with a geometric mean (GM) of 82 Bq m(-3) and a geometric standard deviation (GSD) of 2.56 in Fredericton, and from 4 to 2341 Bq m(-3) with a GM of 107 Bq m(-3) and a GSD of 3.67 in Halifax. It is estimated that 18 % of Fredericton homes and 32 % of Halifax homes could have radon concentrations above the Canadian indoor radon guideline of 200 Bq m(-3). This conclusion is significantly higher than the previous estimates made 30 y ago with short-term radon measurements. Thoron concentrations were below the detection limit in 62 % of homes in both cities. Among the homes with detectable thoron concentrations, the values varied from 12 to 1977 Bq m(-3) in Fredericton and from 6 to 206 Bq m(-3) in Halifax. The GM and GSD were 86 Bq m(-3) and 3.19 for Fredericton, and 35 Bq m(-3) and 2.35 for Halifax, respectively. On the basis of these results, together with previous measurements in Ottawa, Winnipeg and the Mont-Laurier region of Quebec, it is estimated that thoron contributes ∼8 % of the radiation dose due to indoor radon exposure in Canada.

Gold was mined in 64 districts in southern Nova Scotia between 1861 and the early 1940s, followed by limited, intermittent production up to the present. There is extensive dispersion of arsenic- and mercury-bearing mine tailings in the receiving environment downstream from many of these sites. Elevated mercury concentrations, highest near old stamp mill foundations, occur because of the mercury amalgamation process used to extract gold until the 1940s. Arsenic, on the other hand, occurs naturally in arsenopyrite, which is associated with the gold-bearing quartz veins and host rocks. Tailings are composed of fine sand- to silt-sized quartz, feldspar, illite and chlorite, and represent the primary rock-forming minerals in the metasedimentary host rocks of the Cambro-Ordovician Meguma Supergroup. Carbonate and sulphide minerals occur in minor to trace amounts, along with secondary minerals such as scorodite (FeAsO 4 ·2H 2 O). The extent of tailings dispersal can be mapped through hyperspectral remote sensing methods, as these major mineral components provide an identifiable spectral signature through visible, near infrared and short-wave infrared regions. This paper examines the mineralogy of soils, tills and tailings in the Upper and Lower Seal Harbour gold districts of Nova Scotia. Ground-truthing of space-borne hyperspectral data demonstrates the potential for remote mapping of the spatial extent of these historical mine wastes.

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Detailed geological mapping of the Goldenville and Halifax groups in metropolitan Halifax Regional Municipality, Nova Scotia, resulted in two-fold subdivision of both groups. The Goldenville Group was divided into the metasandstone (feldspathic wacke)-dominated Taylors Head formation and the overlying, metasiltstone-dominated, Mn-rich Beaverbank formation. The Halifax Group was divided into the Cunard formation, dominated by sulphide-rich slate, and the overlying Bluestone formation, consisting of mainly metasiltstone and metasandstone. Lithogeochemical and petrological studies resulted in the characterization of the Beaverbank, Cunard, and Bluestone formations as potential acid-producing units with pyrrhotite as the main iron-sulphide mineral. The presence of acid rock drainage (ARD) is governed by bulk-rock chemical composition and mineral assemblage. To test the predictability of ARD production, a portable XRF instrument was used to obtain relatively inexpensive whole-rock and sulphur data that were used in conjunction with conventional XRF analyses and acid-base accounting tests. Results from the three methods compare favourably. Use of the portable XRF instrument facilitates a timely and cost-effective approach to predicting ARD but does not replace the legally mandated acid-base accounting procedure. RÉSUMÉUne cartographie géologique détaillée des groupes de Goldenville et de Halifax dans la municipalité régionale de Halifax, en Nouvelle-Écosse, a donné lieu à deux divisions de ces deux groupes. Pour ce qui est du groupe de Goldenville, les deux formations suivantes ont été établies: la Formation de Taylors Head, composée principalement de métagrès (wacke feldspathique) et la Formation de Beaverbank sus-jacente, composée principalement de métasiltite riche en Mn. En ce qui concerne le groupe de Halifax, les deux formations que voici ont été identifiées: la Formation de Cunard, composée principalement d'ardoise riche en sulfures, et la Formation de Bluestone sus-jacente, composée surtout de métasiltite et de métagrès. Les études lithogéochimiques et pétrologiques ont permis d'établir que les Formations de Beaverbank, de Cunard et de Bluestone étaient susceptibles d'agir comme précurseurs acides, la pyrrhotite étant le principal minéral à sulfure de fer présent. La présence d'un drainage rocheux acide (DRA) est régie par la composition chimique de la roche brute et l'association minérale. Pour vérifier la possibilité d'un DRA, de concert avec des analyses traditionnelles à fluorescence X et de bilan acide-base, un appareil portatif à fluorescence X a été utilisé pour recueillir de manière relativement économique des données sur la roche brute et les sulfures. Les résul-tats obtenus par les trois méthodes se comparent bien. L'utilisation d'un appareil à fluorescence X portatif permet de prédire de manière économique et rapidement la possibilité du DRA, mais cette technique ne saurait se substituer à l'analyse du bilan acide-base prévue par la réglementation.[Traduit par la redaction]