Interlaboratory study of a method for determining nonvolatile organic carbon in aquifer materials

The organic carbon fraction in aquifer materials exerts a major influence on the subsurface mobilities of organic and organic-associated contaminants. The spatial distribution of total organic carbon (TOC) in aquifer materials must be determined before the transport of hydrophobic organic pollutants in aquifers can be modeled accurately. Previous interlaboratory studies showed that it is difficult to measure TOC concentrations 1%. We have tested a new analytical method designed to improve the accuracy and precision of nonvolatile TOC quantitation in geologic materials that also contain carbonate minerals. Four authentic aquifer materials and one NIST standard reference material were selected as test materials for a blind collaborative study. Nonvolatile TOC in these materials ranged from 0.05 to 1.4%, while TIC ranged from 0.46 to 12.6%. Sample replicates were digested with sulfurous acid, dried at 40°C, and then combusted at 950°C using LECO or UIC instruments. For the three test materials that contained >2% TIC, incomplete acidification resulted in a systematic positive bias of TOC values reported by five of the six laboratories that used the test method. Participants did not have enough time to become proficient with the new method before they analyzed the test materials. A seventh laboratory successfully used an alternative method that analyzed separate liquid and solid fractions of the acidified sample residues.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46768/1/254_2004_Article_BF00770471.pd

Benzodiazepine use and aggressive behaviour : a systematic review

Context: The relationship between benzodiazepine consumption and subsequent increases in aggressive behaviour in humans is not well understood. Objectives: The current study aimed to identify, via a systematic review, whether there is an association between benzodiazepine consumption and aggressive responding in adults. Method: A systematic review was conducted and reported in line with the PRISMA statement. English articles within MEDLINE, PsycARTICLES, PsycINFO, Academic Search Complete, and Psychology and Behavioural Sciences Collection databases were searched. Additional studies were identified by searching reference lists of reviewed articles. Only articles that explicitly investigated the relationship between benzodiazepine consumption and subsequent aggressive behaviour, or a lack thereof, in human adults were included. Results: Forty-six studies met the inclusion criteria. It was not possible to conduct a meta-analysis due to the heterogeneity of study design and benzodiazepine type and dose. An association between benzodiazepine use and subsequent aggressive behaviour was found in the majority of the more rigorous studies, although there is a paucity of high-quality research with clinical or forensic populations. Diazepam and alprazolam have received the most attention. Dose-related findings are inconsistent: therapeutic doses may be more likely to be associated with aggressive responding when administered as a once-off, whereas higher doses may be more risky following repeated administration. Trait levels of anxiety and hostility may indicate a vulnerability to the experience of benzodiazepine-related aggression. Conclusions: There appears to be a moderate association between some benzodiazepines and subsequent aggressive behaviour in humans. The circumstances under which aggressive responding may be more likely to follow benzodiazepine use remain unclear, although some evidence suggests dose and/or personality factors may influence this effect.</p

Mobility of heavy metals in dredged harbor sediments

Solubility, mobility, and bioavailability of sediment-bound metals can be increased by four major facors: (1) Lowering of pH; (2) changing of redox conditions; (3) formation of organic complexes; and (4) increasing salinity. While the first two factors are particularly important for on-land deposition of dredged materials, the effect of salinity is particularly important for resuspended cadmium-rich sediments in estuaries. Chemical extraction studies, which were carried out under carefully controlled conditions on both fresh and freeze-dried samples, indicate that aeration of anoxic sediments (e.g., on-land disposal) may both increase and decrease the mobility of heavy metals. Transformation from sulfidic or carbonatic associations to oxidic phases will reduce mobility of manganese, wherease the respective changes from moderately reducible forms to carbonatic and easily reducible phases will enhance the reactivity of zinc during oxidation of dredged material