Private water supplies, which are the primary source of drinking water for rural communities in developed countries, are at risk of becoming fecally contaminated. It is important to identify the source of contamination in order to better understand and address this human health risk. Microbial source tracking methods using human, bovine and general Bacteroidales markers were performed on 716 well water samples from southeastern Ontario, which had previously tested positive for Escherichia coli. The results were then geospatially analyzed in order to elucidate contamination patterns. Markers for human feces were found in nearly half (49%) of all samples tested, and a statistically significant spatial cluster was observed. A quarter of the samples tested positive for only general Bacteroidales markers (25.7%) and relatively few bovine specific marker positives (12.6%) were found. These findings are fundamental to the understanding of pathogen dynamics and risk in the context of drinking well water and will inform future research regarding host-specific pathogens in private well water samples.

Abstract.Research to date has provided limited insight into the complexity of water-borne pathogen transmission. Private well water supplies have been identified as a significant pathway in infectious disease transmission in both the industrialised and the developing world. Using over 90,000 private well water submission records representing approximately 30,000 unique well locations in south-eastern Ontario, Canada, a spatial analysis was performed in order to delineate clusters with elevated risk of E. coli contamination using 5 years of data (2008)(2009)(2010)(2011)(2012). Analyses were performed for all years independently and subsequently compared to each other. Numerous statistically significant clusters were identified and both geographic stability and variation over time were examined. Through the identification of spatial and temporal patterns, this study provides the basis for future investigations into the underlying causes of bacterial groundwater contamination, while identifying geographic regions that merit particular attention to public health interventions and improvement of water quality.

An investigation of some of the volatile compounds produced by boiling potatoes has been carried out by gas chromatography. The method used for the concentration, separation and identification of small samples of such compounds is described. These were shown to include hydrogen sulphide, acetaldehyde, methanethiol, acrolein, acetone, ethanethiol, dimethyl sulphide, iso-and n-butyraldehyde, isovaleraldehyde and methyl isopropyl ketone, along with some unidentified components. These findings are discussed in relation t o the Strecker degradation of amino-acids, and in the light of present knowledge of flavour components.chem.

Following the evolution of sulphur compounds from cultures of marine organisms in methionine solution, the collection of thiols and disulphides in mercuric cyanide and mercuric chloride was studied. The subsequent conversion of the mercaptides and mercury complexes to z,4-dinitrophenyl sulphides was found to be possible by decomposing the mercury compounds with acid and collecting the mercaptan in caustic ethanol and then treatment with 1-chloro-z,4-dinitrobenzene. A method for the chromatography of the n,4-dinitrophenyl sulphides on paraffin-impregnated paper was devised and studied. IntroductionDuring attempts to separate and identify the metabolites of marine organisms cultured with methionine, an odour, closely resembling that of organic sulphur compounds, was 0bserved.l This was also noticed when samples of marine organisms were treated with a solution of 10% caustic soda. These volatile sulphur compounds were collected successfully in mercuric cyanide and mercuric chloride according to the method of Challenger.2 The further identification of the alkali-decomposable precipitate3 from mercuric chloride, by paper chromatography of the regenerated sulphide as the sulphidimine4 was found to be satisfactory. This method of Challenger & Leaver has recently been extended and improved by the use of 9-nitrobenzenesulphonchloramide, NO,*C,H,.SO,N(Cl)Na, instead of chloramine T.5There are, however, few methods, apart from the melting points of the mercaptides of mercury and lead, for the further identification and separation of thiols. The thiols were either given off as thiols from the cultures and decomposition experiments, or were obtained from the acid decomposition of mercury complexes formed in mercuric chloride and mercuric acetate solution from fission of the disulphides.21 3The reaction of thiols with mercuric cyanide leads, it is supposed,2 to the formation of the insoluble complex (RS),Hg and (RS)2Hg.Hg(CN),. By boiling with water3 the mixture is converted to the pure mercaptide which may be recrystallised to give a well defined melting point. If the material for examination consists of mixture of thiols, the separation could only be effected by gas chromatography.In earlier work 1-chloro-z,4-dinitrobenzene was used by Boost and others6 to prepare 3,4-dinitrophenyl sulphides from thiols ; these sulphides were also prepared by Carson & Wong7 from lead mercaptides by refluxing with the reagent named. The latter authorss chromatographed the z,4-dinitrophenyl sulphides on silicic acid and fluorescent zinc sulphide. It was felt, however, that paper chromatography of the z,4-dinitrophenyl sulphide might be more suitable. It was not possible to prepare crystalline z,4-dinitrophenyl sulphides by refluxing 1-chloro-z,4-dinitrobenzene with a mercury mercaptide.The crystalline z,4-dinitrophenyl sulphides were finally prepared, both from the mercury mercaptides and the mercury complex resulting from disulphide fission, by decomposition with acid and aspiration of the acid-free thiol vapours into ethanolic sodium hydroxi...