Microbial diversity and functional response to the redox dynamics of pyrite-rich sediment and the impact of preload surcharge.

Microbial diversity and activities play pivotal biogeochemical roles in a redox-sensitive, pyrite-rich sediment's ecosystem. However, very little is known about the microbial community composition and distribution among the redox zones of pyrite-rich sediment and their response to changes caused by the burial of the sediment beneath compacted fill. In the present work, culture-independent, molecular phylogenetic investigations of the prokaryotic population and its diversity in a naturally occurring pyrite-rich sediment were undertaken to determine the microbial community composition, richness, diversity and distributions among the varying redox zones and their functional response to the imposition of surface surcharge, in the form of compacted fill. It was established that the pyrite-rich sediment is a redox-sensitive environment consisting of microhabitats with distinct and discontinuous physico-chemical characteristics, including DO, pH, Eh, temperature, electrical conductivity and salinity. It is a favourable environment for cyclic transformation of inorganic sulphur compounds and a unique environment for the habitation and growth of various microorganisms. Microbes adapted to the microhabitat and lived together in consortia, in response to their physiological and functional requirements. Microbes involved in the sulphur cycle had their populations concentrated in the oxic zone, while those involved in iron and carbon cycles were prevalent in the anoxic zones. As a result, highly diverse microbial populations occurred in isolated peaks within the sediment. The physico-chemical differences within the sediment changed in response to changes in the sediment redox dynamics. Imposition of the surcharge resulted in significant changes in the pH, temperature, Eh, DO, EC and salinity, reflecting marked re-distribution of the microbial population within the ecosystem. The cable bacteria phenomenon was evident in the sediment studied; however, there were doubt regarding their filamentous occurrence.

Anaerobic pyrite oxidation in a naturally occurring pyrite-rich sediment under preload surcharge.

Pyrite undergoes oxidation when exposed to aqueous oxygen to produce acidic leachate with high concentrations of H+, SO42-, and Fe3+. The oxidation mechanism is currently ascribed to contact between the mineral and aqueous oxygen. Consequently, management of acidic leachate from acid sulfate soils and acid mine drainage is focused on the prevention of contact between the sediment and aqueous oxygen through the surface. Intriguing though is the fact that in aquatic sediments, redox processes occur in sequence with the oxidizing agents. Among the common oxidants in aquatic sediments are O2, [Formula: see text], Mn, and Fe, in the order of efficiency. Consequently, following the depletion of oxygen in pyrite-rich sediment, it would be expected that [Formula: see text], followed by Mn and then Fe, would continue the oxidation process. However, evidence of anaerobic pyrite oxidation in a naturally occurring pyrite-rich sediment is limited. Few studies have investigated the process in aquatic systems but mostly in laboratory experimental set ups. In this study, pyrite oxidation in a naturally occurring pyrite-rich sediment was investigated. A section of the sediment was covered with surface surcharge, in the form of compacted fill. The section of the sediment outside the surcharged area was preserved and used as control experiment. Solid phase soil and porewater samples were subjected to elemental, mineralogical, and microbial analyses. The results show excess accumulation of sulfate and sulfide in the anoxic zones of the original sediment and beneath the surcharge, accompanied by the disappearance of [Formula: see text], Mn, and Fe in the anoxic zones, indicating electron transfers between donors and acceptors, with pyrite as the most likely electron donor. The study outcome poses a significant challenge to the use of surface cover for the management of acidic leachate from pyrite oxidation, particularly, in areas rich in [Formula: see text], MnO-2, or Fe.

The impact of preload on the mobilisation of multivalent trace metals in pyrite-rich sediment.

Trace metals occur at various concentrations in all wetlands. Their proliferation, chemical speciation, mobility and bioavailability are dependent on the redox potential (Eh), pH and the presence of organic and inorganic adsorption surfaces and co-precipitating metals. Consequently, changes in these key parameters have the potential to alter the fate of the dominant trace metal species in the sediment. An imposition of preload surcharge is a technique use in geotechnical engineering to improve in the strength and load carrying capacity of waterlogged sediments. The soil strength improvement is effected through the expulsion of porewater from the sediment. The imposition of surcharge over wetland sediments has the potential to create oxygen-deficient condition within the sediment, and cause pH, temperature, redox, EC and salinity changes in the sediment, which would impact on the mobilisation, chemical speciation, mobility and bioavailability of dominant toxic trace metals and their toxicity in the sediment. In the present work, a case study of the impact of preload surcharge on the proliferation, chemical speciation, mobilisation, mobility and bioavailability of arsenic, chromium, cobalt, copper and zinc in a naturally occurring pyrite-rich sediment is presented. The imposition of preload surcharge over the pyrite-rich sediment was accompanied by changes in the redox dynamics of the sediment, with multi-facet impact on the concentration, mobilisation and bioavailability of toxic trace metals, their redox transformation between oxidation states and on the toxicity within and outside the sediment environment.

Analytical characterisation of nanoscale zero-valent iron: A methodological review.

Zero-valent iron nanoparticles (nZVI) have been widely tested as they are showing significant promise for environmental remediation. However, many recent studies have demonstrated that their mobility and reactivity in subsurface environments are significantly affected by their tendency to aggregate. Both the mobility and reactivity of nZVI mainly depends on properties such as particle size, surface chemistry and bulk composition. In order to ensure efficient remediation, it is crucial to accurately assess and understand the implications of these properties before deploying these materials into contaminated environments. Many analytical techniques are now available to determine these parameters and this paper provides a critical review of their usefulness and limitations for nZVI characterisation. These analytical techniques include microscopy and light scattering techniques for the determination of particle size, size distribution and aggregation state, and X-ray techniques for the characterisation of surface chemistry and bulk composition. Example characterisation data derived from commercial nZVI materials is used to further illustrate method strengths and limitations. Finally, some important challenges with respect to the characterisation of nZVI in groundwater samples are discussed.

Illicit drug use and problem gambling.

Problem gambling, substance use disorders, and their cooccurrence are serious public health concerns. We conducted a comprehensive review of the literature to understand the present state of the evidence on these coaddictions. Our main focus was illicit drug use rather than misuse of legal substances. The review covers issues related to gambling as a hidden problem in the illicit drug use community; prevalence, problem gambling, and substance use disorders as kindred afflictions; problem gambling as an addiction similar to illicit drug use; risk factors and problems associated with comorbidity, and gender issues. We end with some suggestions for future research.

Journey as destination: a recovery model for families affected by concurrent disorders.

We conducted a study offering peer support and education to members of families affected by concurrent disorders (CD). This article is an analysis of the qualitative data from a mixed methods study. Using constructivist grounded theory, we analyzed semistructured interviews with participants, with half attending a 12-week support group and reading weekly workbook assignments, and the others receiving the workbook only and being interviewed 3 months later. We developed a model that describes family journeys into, through, and beyond CD, involving three phases connected by two transitional constructs. Preoccupation with the unresolved CD of an ill family member characterized the journey into and through illness, the first two phases, whereas renewal characterized the passage from illness to journeying on toward recovery. Participants had strong comments about health care providers and the service system, and spoke of the need for self-care, empowerment, support, and inclusion.

In situ ATR FTIR studies of SO4 adsorption on goethite in the presence of copper ions.

Despite the existence of many single ion sorption studies on iron and aluminum oxides, fewer studies have been reported that describe cosorption reactions. In this work, we present an in situ ATR FTIR study of synergistic adsorption of sulfate (SO4) and copper (Cu) on goethite, which is representative of the minerals and ions present in mine wastes, acid sulfate soils, and other industrial and agricultural settings. Sulfate adsorption was studied as a function of varying pH, and as a function of increasing concentration in the absence and presence of Cu. The presence of Cu ions in solution had a complex effect on the ability of SO4 ions to be retained on the goethite surface with increasing pH, with complete desorption occurring near pH 7 and 9 in the absence and presence of Cu, respectively. In addition, Cu ions altered the balance of inner vs outer sphere adsorbed SO4. The solid phase partitioning of SO4 at pH 3 and pH 5 was elevated by the presence of Cu; in both cases Cu increased the affinity of SO4 for the goethite surface. Complementary ex situ sorption edge studies of Cu on goethite in the absence and presence of SO4 revealed that the Cu adsorption edge shifted to lower pH (6.3 --> 5.6) in the presence of SO4, consistent with a decrease of the electrostatic repulsion between the goethite surface and adsorbing Cu. Based on the ATR FTIR and bulk sorption data we surmise that the cosorption products of SO4 and Cu at the goethite-water interface were not in the nature of ternary complexes under the conditions studied here. This information is critical for the evaluation of the onset of surface precipitates of copper-hydroxy sulfates as a function of pH and solution concentration.

Preliminary synchrotron analysis of lead in hair from a lead smelter worker.

Synchrotron X-ray fluorescence has been used to study the distribution of lead in a hair sample collected from a lead smelter worker. A mathematical model was used to imitate the transverse scan signal based on the analysis volume and concentration profiles. The results suggest that the Pb originates both from ingestion and environmental exposure, however direct deposition from the environment is the more important source of hair lead. The model could apply equally to any other analysis involving a thin cylindrical sample.

Time of flight secondary ion mass spectrometry studies of the distribution of metals between the soil, rhizosphere and roots of Populus tremuloides Minchx growing in forest soil.

Time of flight secondary ion mass spectroscopy has been used to study the metal distribution at the soil/root interface of tree roots extracted from smelter-impacted soils. The results, augmented by scanning electron microscopy, show that the technique is capable of resolving metal distributions at the cellular level. In addition, the distribution of metals between the root plaque and the root interior may be useful in interpreting local metal transport mechanisms.

Calcium distributions in human hair by ToF-SIMS.

Calcium distributions on internal and external surfaces of longitudinally sectioned hairs were analysed with Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Externally, calcium deposits were observed at the cuticle scale edges. Internal sections showed that the bulk of calcium exists within or just inside the cuticle layer. The medulla may or may not be enriched and other localised concentrations exist in one of two forms; either associated with granular structures or the hair proteins. Calcium appears to show an affinity for proteins with low sulfur content.

Time-of-flight secondary ion mass spectrometry analysis of hair from archaeological remains.

Hair from four individuals excavated from burial sites in Pacatnamu, Peru from the Moche (450-800 AD) and Lambayeque (900-1100 AD) periods was sectioned longitudinally and analysed with time-of-flight secondary ion mass spectrometry (ToF-SIMS). An attempt was made to distinguish biogenic and diagenetic contributions to the elemental concentrations in the hair samples. Significant contamination was observed to have penetrated the hair samples from the burial environment. Results from the analyses indicate that the burial environment plays an important role in the postmortem variation in elemental content of hair samples. Various elements demonstrated an ability to permeate through the hair matrix over time. In addition, NaCl and what are believed to be aluminosilicates and mineral sulphates, were observed to have accumulated on the surface of the samples. Degradation of the samples was also suspected due to the presence of molecular fragments, possibly resulting from oxidation of the keratin proteins. The results should assist in the identification of reliable elemental signals in the analysis of ancient hair samples and promote caution when considering elements that are abundant in the burial environment.

Gene information for fungal plant pathogens from expressed sequences.

Gaining information on global gene function in fungal plant pathogens through analysis of expressed sequences is a valuable step towards understanding the overall metabolism and biology underlying the pathogenic habit. Such large-scale gene-finding exercises are poised to provide many useful leads for discovering key events that contribute to the processes of infection and colonisation of host plants.

Characterisation of 0.22 caliber rimfire gunshot residues by time-of-flight secondary ion mass spectrometry (TOF-SIMS): a preliminary study.

The application of time-of-flight secondary ion mass spectrometry (TOF-SIMS) for the characterisation of gunshot residue (GSR) from 0.22 caliber rimfire ammunition is reported. Results obtained by TOF-SIMS were compared with conventional scanning electron microscopy (SEM) studies. As could be expected, TOF-SIMS exhibited greater elemental sensitivity than SEM equipped with energy dispersive X-ray detection (SEM-EDX), and was also capable of detecting fragments characteristic of inorganic compounds. This preliminary study indicates that TOF-SIMS offers substantial potential for forensic GSR examinations as a complementary technique to SEM-EDX. In addition TOF-SIMS is applicable to the analysis of individual particles in the typical size range encountered in GSR casework.

Rebuilding organizational culture in the wake of a merger.

More and more, corporate culture is being recognized as an important determinant of organizational effectiveness. This article describes how the Centre for Addiction and Mental Health proactively focused on rebuilding its culture after a mandated merger. The long-term effects of this effort need to be monitored. However, commitment is strong to the ideas articulated in the Statement of Desired Culture that was developed by a staff task force and approved by the Centre's Board.

Sensation seeking and drug use by adolescents and their friends: models for marijuana and alcohol.

OBJECTIVE: To investigate the prospective influence of individual adolescents' sensation seeking tendency and the sensation seeking tendency of named peers on the use of alcohol and marijuana, controlling for a variety of interpersonal and attitudinal risk and protective factors. METHOD: Data were collected from a cohort of adolescents (N = 428; 60% female) at three points in time, starting in the eighth grade. Respondents provided information about sensation seeking, the positivity of family relations, attitudes toward alcohol and drug use, perceptions of their friends' use of alcohol and marijuana, perceptions of influence by their friends to use alcohol and marijuana, and their own use of alcohol and marijuana. In addition, they named up to three peers, whose sensation seeking and use data were integrated with respondents' data to allow for tests of hypotheses about peer clustering and substance use. RESULTS: Structural equation modeling analyses revealed direct effects of peers' sensation seeking on adolescents' own use of both marijuana and alcohol 2 years later. An unexpected finding was that the individual's own sensation seeking had indirect (not direct) effects on drug use 2 years later. CONCLUSIONS: These findings indicate the potential importance of sensation seeking as a characteristic on which adolescent peers cluster. Furthermore, the findings indicate that, beyond the influence of a variety of other risk factors, peer sensation seeking contributes to adolescents' substance use.

Peer networks and sensation seeking: some implications for primary socialization theory.

This article draws on recent work in sensation seeking and peer influences in drug use prevention and considers some possible implications for primary socialization theory. A particular point of focus is a postulate of the theory that an individual's personal characteristics and personality traits do not directly relate to drug use and deviance but ordinarily influence those outcomes only when they affect interactions between the individual and the primary socialization sources. The article suggests a more broadly encompassing perspective which holds that socialization learning through the primary socialization sources gives people's lives direction; it may be the tugs of activation needs which provide impetus for the actions. The authors cite a recent study in which they developed a structural equation model of influence of individual and peer variables on later alcohol and marijuana use. The model indicates an indirect route from individual sensation seeking through peers to drug and alcohol use, with adolescents picking persons of similar sensation-seeking levels, and the sensation-seeking level of these peers tending to influence alcohol and marijuana use. Although previous studies have suggested causal relationships between sensation seeking and drug use and between peer influence and drug use, the findings in this study suggest that the actual process involves both. [Translations are provided in the International Abstracts Section of this issue.]

Laboratory studies of alkali metal filter deposition, ultraviolet transmission, and visible blocking.

Far-ultraviolet alkali metal or Wood's filters have been produced and tested supporting the production of a flight filter for the Wide Field Planetary Camera 2 on the Hubble Space Telescope. Sodium layers 0.5-1-microm thick transmit up to 40% in the ultraviolet while efficiently blocking visible wavelengths. The prevention of visible pinholes is assisted by a clean, sleek-free surface and a cooled substrate during deposition. The coatings are stabilized efficiently by a bismuth overcoating whose transmission spectrum is presented. We also report for the first time, to our knowledge, the first demonstrated long-wavelength cutoff from a lithium filter, with a shorter cutoff wavelength than sodium and potentially higher stability for astronomical imaging.

A single amino-acid substitution in the iron-sulphur protein subunit of succinate dehydrogenase determines resistance to carboxin in Mycosphaerella graminicola.

A gene encoding the iron-sulphur protein (Ip) subunit of succinate dehydrogenase (Sdh, EC 1.3.99.1) from Mycosphaerella graminicola (Septoria tritici) has been cloned andsequenced. The deduced amino-acid sequence exhibited a high degree of homology to Ip subunits of Sdh from other organisms; three cysteine-rich clusters associated with the iron-sulphur centres involved in electron transport were particularly conserved. Expression studies using a synthetic green fluorescent protein (SGFP) expression vector demonstrated that the cloned DNA also contained a functional promoter region and confirmed that the deduced initiation codon could act as a translational start site. Mutants resistant to the fungicide carboxin (Cbx), a known inhibitor of Sdh, were found to contain a single amino-acid substitution in the third cysteine-rich domain of the Ip protein. These mutations resulted in the conversion of a highly conserved His residue, located in a region of the protein associated with the [3Fe-4 S] high-potential non-heme iron sulphur-redox (S3) centre, to either Tyr or Leu. AnIp gene containing the His -> Tyr mutation was constructed and shown to confer Cbx resistance following co-transformation into the Cbx-sensitive wild-type strain. This confirmed that the mutation identified by sequence analysis was responsible for determining Cbx resistance.

Elemental content of airway surface liquid from infants with cystic fibrosis.

We tested the hypothesis that airway surface liquid (ASL) electrolyte composition is altered in infants with cystic fibrosis (CF) and that the presence of airway inflammation affects ASL composition. We measured the tracheal ASL sodium and chloride concentration and examined bronchoalveolar lavage (BAL) fluid cytology, interleukin-8 (IL-8) concentrations, and quantitative bacterial culture in 19 infants and young children with CF. Seven infants undergoing bronchoscopy for the evaluation of stridor served as non-CF controls. In addition, we measured nasal ASL sodium and chloride concentrations from 10 young adults with CF and from 10 control subjects. On the basis of the BAL findings, the infants with CF were divided into three groups: one with little evidence of pulmonary inflammation (CF-NI, n = 5); one with obvious pulmonary inflammation (CF-I, n = 7); and an intermediate group (CF-MI, n = 7). We found the ASL sodium was not different among any of the four groups (means mM +/- SE, 85 +/- 10 controls; 78 +/- 16 CF-NI; 83 +/- 9 CF-MI, 84 +/- 9 CF-I). In contrast the ASL chloride was lower in the CF-NI group when compared with control subjects (108 +/- 5 control subjects; 77 +/- 7 CF-NI, p < 0.01). In the CF-I and CF-MI groups, the ASL chloride concentrations were of intermediate values (CF-I 95 +/- 10 mM; CF-MI 96 +/- 9 mM) and not significantly different from controls. Results from the nasal ASL analysis showed no significant differences in sodium and chloride concentrations in the CF group compared with control subjects. These results suggest that the primary abnormality of ASL composition is a reduction in chloride concentration. ASL composition appears to be affected by the presence of airway inflammation.

Validation of wind profiles measured with incoherent Doppler lidar.

A high-resolution incoherent Doppler lidar has been constructed at the University of Michigan Space Physics Research Laboratory. The primary purpose of this lidar is to measure vertical profiles of the horizontal wind field with high spatial and temporal resolution. In mid-1994 a rawinsonde system was used to assess the performance of the lidar. The resulting comparisons of profiles from the balloons and the lidar are shown. The comparisons show an ~2-m/s rms error between the two systems. The reasons for this error are discussed, and a sensitivity study is shown to illustrate the sensitivity of the lidar wind measurements to various system parameters. Finally, steps that are being taken to improve the systematic errors are discussed.