Adsorption behavior of 2,4-dichlorophenol and pentachlorophenol in an allophanic soil

The adsorption of 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP) by a variable-charge soil from southern Chile was studied in a series of batch equilibration experiments. 2,4-DCP and PCP adsorption behavior was evaluated as a function of pH (pH values of 4.5, 6.0 and 7.5) in a 0.1M KCl (25 degrees C) background solution for soil material collected at three different depths (0-20 cm, 20-40 cm, and 40-60 cm). 2,4-DCP and PCP adsorption decreased with increasing soil pH, suggesting that the undissociated species were adsorbed more readily and that electrostatic repulsion may inhibit partitioning as pH increases. The PCP adsorption was greater than observed for 2,4-DCP and decreased with soil depth. Multiple regression analysis between K(d) and various soil properties indicated that the soil organic carbon content is a strong indicator of chlorophenol adsorption, and in addition to organic carbon, the soil pH is an important property controlling adsorption behavior.     

Photocatalytic mechanisms of indoleamine destruction by the quinalphos metabolite 2-hydroxyquinoxaline: a study on melatonin and its precursors serotonin and N-acetylserotonin

The redox-active quinalphos main metabolite, 2-hydroxyquinoxaline, is particularly effective under excitation by light. We have studied the photocatalytic destruction of melatonin and its precursors, because the cytoprotective indoleamine has been detected in high quantities in mammalian skin. In photooxidation reactions, in which melatonin, N-acetylserotonin and serotonin are destroyed by 2-hydroxyquinoxaline, the photocatalyst is virtually not consumed. Rates of melatonin and serotonin destruction are not changed by the singlet oxygen quencher 1,4-diazabicyclo-(2,2,2)-octane, indicating that this oxygen species is not involved in the primary reactions, so that the persistence of 2-hydroxyquinoxaline has to be explained by redox cycling. This should imply formation of an organic radical, presumably the quinoxaline-2-oxyl radical, from which 2-hydroxyquinoxaline is regenerated by electron abstraction from indolic radical scavengers. Electron donation by 2-hydroxyquinoxaline is demonstrated by reduction of the 2,2'-azino-bis-(3-ethylbenzthiazolinyl-6-sulfonic acid) cation radical under ultrasound excitation. The compound 2-hydroxyquinoxaline interacts with the specific superoxide anion scavenger Tiron. Formation of oligomeric products from melatonin and serotonin is strongly inhibited by sodium dithionite. Products from photocatalytic indolamine conversion are predominantly dimers and oligomers. No kynuramines were detected in the case of serotonin oxidation, and melatonin's otherwise prevailing oxidation product N(1)-acetyl-N(2)-formyl-5-methoxykynuramine, another cytoprotective metabolite, is only formed in relatively small quantities. The proportion between products from melatonin is changed by 1,4-diazabicyclo-(2,2,2)-octane: singlet oxygen, also formed under the influence of excited 2-hydroxyquinoxaline, only affects secondary reactions.     

Permanent aggregations of a pelagic predator at shallow seamounts

The effectiveness of marine reserves for highly mobile reef fishes such as jacks and trevallies is normally assumed to be small, even though we generally lack the understanding of their long-term movement patterns. In this work, we combined the analysis of multi-year landings and underwater visual census with acoustic telemetry to investigate the long-term movement patterns (up to 4 years) of almaco jack, Seriola rivoliana, a large reef top predator, in one protected and one unprotected offshore shallow seamount in the Azores, central North Atlantic. Although the analysis of visual census and landing data suggests a pronounced seasonal pattern of occurrence, we found that tagged fish were almost continuously detected at the seamounts for up to four consecutive years. Some individuals showed a few long periods of undetection of 1–2 months in the Formigas reserve, mostly in the fall and winter. Mobility within this seamount increased during spring and summer, and geostrophic current speed was negatively correlated with detection probability. Overall, the acoustic telemetry results showed that adult almaco jacks were resident year-round, refuting the traditional view that these fish are essentially migratory and a seasonal occurrence in the Azores. Given the intrinsic vulnerability of resident fish to fishing, our results highlight the importance of protecting these sites in order to preserve these mature fish aggregations with high reproductive potential.     

Improving an algorithm for classifying error types of front-line workers: Insights from a case study in the construction industry

The objective of this study was to propose improvements in an algorithm for classifying error types of front-line workers. The improvements involved: (a) making recommendations on organizing the data needed to apply the algorithm (e.g. identify actions and decisions that may serve as a reference for analysing the types of errors) and (b) drawing up guidelines for interpreting the questions that are part of the algorithm (e.g. how to define what counts as a procedure). The improvements were identified on the basis of testing the algorithm on construction sites, an environment in which it had not yet been implemented. Thus, 19 occupational accidents which had occurred in a small-sized construction company were investigated and the error types of both workers who had been injured and crew members were classified. The accidents investigated were used as a basis both to illustrate how the improvements proposed should be put in practice and to illustrate how practical insights for safety management might be derived from the algorithm.     

Overview of Traditional and Environmental Factors Related to Bone Health

Environmental Science and Pollution Research - Bone mass in adulthood depends on growth and mineralization acquired during childhood and adolescence. It is well known that these stages of life are...