Retardation of arsenic transport through a Pleistocene aquifer.

Groundwater drawn daily from shallow alluvial sands by millions of wells over large areas of south and southeast Asia exposes an estimated population of over a hundred million people to toxic levels of arsenic. Holocene aquifers are the source of widespread arsenic poisoning across the region. In contrast, Pleistocene sands deposited in this region more than 12,000 years ago mostly do not host groundwater with high levels of arsenic. Pleistocene aquifers are increasingly used as a safe source of drinking water and it is therefore important to understand under what conditions low levels of arsenic can be maintained. Here we reconstruct the initial phase of contamination of a Pleistocene aquifer near Hanoi, Vietnam. We demonstrate that changes in groundwater flow conditions and the redox state of the aquifer sands induced by groundwater pumping caused the lateral intrusion of arsenic contamination more than 120 metres from a Holocene aquifer into a previously uncontaminated Pleistocene aquifer. We also find that arsenic adsorbs onto the aquifer sands and that there is a 16-20-fold retardation in the extent of the contamination relative to the reconstructed lateral movement of groundwater over the same period. Our findings suggest that arsenic contamination of Pleistocene aquifers in south and southeast Asia as a consequence of increasing levels of groundwater pumping may have been delayed by the retardation of arsenic transport.

Reversible adsorption and flushing of arsenic in a shallow, Holocene aquifer of Bangladesh.

The spatial heterogeneity of dissolved arsenic (As) concentrations in shallow groundwater of the Bengal Basin has been attributed to transport of As (and reactive carbon) from external sources or to the release of As from within grey sand formations. We explore the latter scenario in this detailed hydrological and geochemical study along a 300 m transect of a shallow aquifer extending from a groundwater recharge area within a sandy channel bar to its discharge into a nearby stream. Within the 10-20 m depth range, groundwater ages along the transect determined by the 3H-3He method increase from <10 yr in the recharge area to a maximum of 40 yr towards the stream. Concentrations of groundwater As within the same grey sands increase from 10 to 100 to ∼500 µg/L along this transect. Evidence of reversible adsorption of As between the groundwater and sediment was obtained from a series of push-pull experiments, traditional batch adsorption experiments, and the accidental flooding of a shallow monitoring well. Assuming reversible adsorption and a distribution coefficient, Kd, of 0.15-1.5 L/kg inferred from these observations, a simple flushing model shows that the increase in As concentrations with depth and groundwater age at this site, and at other sites in the Bengal and Red River Basins, can be attributed to the evolution of the aquifer over 100-1000 years as aquifer sands are gradually flushed of their initial As content. A wide range of As concentrations can thus be maintained in groundwater with increases with depth governed by the history of flushing and local recharge rates, without external inputs of reactive carbon or As from other sources.

Type of pain, pain-associated complications, quality of life, disability and resource utilisation in chronic pancreatitis: a prospective cohort study.

OBJECTIVE: To compare patients with chronic pancreatitis (CP) with constant pain patterns to patients with CP with intermittent pain patterns. METHODS: This was a prospective cohort study conducted at 20 tertiary medical centers in the USA comprising 540 subjects with CP. Patients with CP were asked to identify their pain from five pain patterns (A-E) defined by the temporal nature (intermittent or constant) and the severity of the pain (mild, moderate or severe). Pain pattern types were compared with respect to a variety of demographic, quality of life (QOL) and clinical parameters. Rates of disability were the primary outcome. Secondary outcomes included: use of pain medications, days lost from school or work, hospitalisations (preceding year and lifetime) and QOL as measured using the Short Form-12 (SF-12) questionnaire. RESULTS: Of the 540 CP patients, 414 patients (77%) self-identified with a particular pain pattern and were analysed. Patients with constant pain, regardless of severity, had higher rates of disability, hospitalisation and pain medication use than patients with intermittent pain. Patients with constant pain had lower QOL (by SF-12) compared with patients who had intermittent pain. Additionally, patients with constant pain were more likely to have alcohol as the aetiology for their pancreatitis. There was no association between the duration of the disease and the quality or severity of the pain. CONCLUSIONS: This is the largest study ever conducted of pain in CP. These findings suggest that the temporal nature of pain is a more important determinant of health-related QOL and healthcare utilisation than pain severity. In contrast to previous studies, the pain associated with CP was not found to change in quality over time. These results have important implications for improving our understanding of the mechanisms underlying pain in CP and for the goals of future treatments and interventions.

Community organization factors affecting veteran participation in adaptive sports.

Objective: This study aims to describe United States military veteran participation in adaptive sports and to assess the demographic make-up and organizational characteristics of existing adaptive sports programs.Design: Prospective, cross-sectional survey.Setting: Community organizations with adaptive sports programs.Participants: 85 adaptive sports programs.Interventions: Nine question survey.Outcome Measures: Demographic data and sports offered by adaptive sports programs in the United States.Results: The survey response rate was 70%. The median number of total participants in an organization was 75 and the median number of veterans was 50. 76% of organizations had some degree of affiliation with a VAMC. Organizations affiliated with a VAMC are more likely to be rehabilitation centers, whereas community organizations with no VAMC affiliation are most commonly independent organizations with no rehabilitation component. Individuals of all ages participate in adaptive sports, with increasing participation associated with increasing age. Golf was the sport offered most commonly by adaptive sports programs in this survey. Low-contact sports were offered more often than high-contact sports, and the majority of programs offered adaptive sports year-round.Conclusions: Our results suggest that U.S. Military veterans represent a large proportion of the individuals participating in adaptive sports. Further research specifically focusing on factors veterans find desirable when considering participating in adaptive sports is indicated to identify programs that should be promoted, developed, and funded to increase veteran participation in adaptive sports.

Establishing the validity of the personality assessment inventory drug and alcohol scales in a corrections sample.

Although not originally designed for implementation in correctional settings, researchers and clinicians have begun to use the Personality Assessment Inventory (PAI) to assess offenders. A relatively small number of studies have made attempts to validate the alcohol and drug abuse scales of the PAI, and only a very few studies have validated those scales in nonclinical correctional samples. The current study examined evidence of convergent and discriminant validity for the substance abuse scales on the PAI in a large, nonclinical sample of offenders. The net sample for the current study consisted of 1,120 federal inmates. Both the drug abuse and alcohol scales showed good convergent validity through high correlations with relevant proximal and distal indicators of substance use across multiple measures from several data sources. Discriminant validity was established as neither scale showed any "erroneous" correlations after controlling for the other scale. Implications for future research and practice are discussed.

Immobilization of mercury by pyrite (FeS2).

Elemental mercury (Hg(0)) is a metal with a number of atypical properties, which has resulted in its use in myriad anthropogenic processes. However, these same properties have also led to severe local subsurface contamination at many places where it has been used. As such, we studied the influence of various parameters on Hg(II) sorption onto pyrite (pH, time, Hg(II) concentration), a potential subsurface reactive barrier. Batch sorption studies revealed that total Hg(II) removal increases with both pH and time. X-ray absorption spectroscopy analysis showed that a transformation in the coordination environment at low pH occurred during aging over 2 weeks, to form an ordered monolayer of monodentate Hg-Cl complexes on pyrite. In column studies packed with pure quartz sand, the transport of Hg(II) was significantly retarded by the presence of a thin pyrite-sand reactive barrier, although dissolved oxygen inhibited Hg(II) sorption onto pyrite in the column.