Differential bioavailability of polychlorinated biphenyls associated with environmental particles: Microplastic in comparison to wood, coal and biochar

Microplastic particles are increasingly being discovered in diverse habitats and a host of species are found to ingest them. Since plastics are known to sorb hydrophobic organic contaminants (HOCs) there is a question of what risk of chemical exposure is posed to aquatic biota from microplastic-associated contaminants. We investigate bioavailability of polychlorinated biphenyls (PCBs) from polypropylene microplastic by measuring solid-water distribution coefficients, gut fluid solubilization, and bioaccumulation using sediment invertebrate worms as a test system. Microplastic-associated PCBs are placed in a differential bioavailability framework by comparing the results to several other natural and anthrogenic particles, including wood, coal, and biochar. PCB distribution coefficients for polypropylene were higher than natural organic materials like wood, but in the range of lipids and sediment organic carbon, and smaller than black carbons like coal and biochars. Gut fluid solubilization potential increased in the order: coal < polypropylene < biochar < wood. Interestingly, lower gut fluid solubilization for polypropylene than biochar infers that gut fluid micelles may have solubilized part of the biochar matrix while bioaccessibility from plastic can be limited by the solubilizing potential of gut fluids dependent on the solid to liquid ratio or renewal of fluids in the gut. Biouptake in worms was lower by 76% when PCBs were associated with polypropylene compared to sediment. The presence of microplastics in sediments had an overall impact of reducing bioavailability and transfer of HOCs to sediment-ingesting organisms. Since the vast majority of sediment and suspended particles in the environment are natural organic and inorganic materials, pollutant transfer through particle ingestion will be dominated by these particles and not microplastics. Therefore, these results support the conclusion that in most cases the transfer of organic pollutants to aquatic organisms from microplastic in the diet is likely a small contribution compared to other natural pathways of exposure.

Effects of activated carbon on reductive dechlorination of PCBs by organohalide respiring bacteria indigenous to sediments

Polychlorinated biphenyls (PCBs) have accumulated in aquatic sediments due to their inherent chemical stability and their presence poses a risk due to their potential toxicity in humans and animals. Granular activated carbon (GAC) has been applied to PCB contaminated sediment sites to reduce the aqueous concentration by sequestration thus reducing the PCB exposure and toxicity to both benthic and aquatic organisms. However, it is not known how the reduction of PCB bioavailability by adsorption to GAC affects bacterial transformation of PCBs by indigenous organohalide respiring bacteria. In this study, the impact of GAC on anaerobic dechlorination by putative organohalide respiring bacteria indigenous to sediment from Baltimore Harbor was examined. It was shown that the average Cl/biphenyl after dehalogenation of Aroclor 1260 was similar between treatments with and without GAC amendment. However, GAC caused a substantial shift in the congener distribution whereby a smaller fraction of highly chlorinated congeners was more extensively dechlorinated to mono- through tri-chlorinated congeners compared to the formation of tri- through penta-chlorinated congeners in unamended sediment. The results combined with comparative sequence analysis of 16S rRNA gene sequences suggest that GAC caused a community shift to putative organohalide respiring phylotypes that coincided with more extensive dechlorination of ortho and unflanked chlorines. This shift in activity by GAC shown here for the first time has the potential to promote greater degradation in situ by promoting accumulation of less chlorinated congeners that are generally more susceptible to complete mineralization by aerobic PCB degrading bacteria.

Polyoxymethylene passive samplers to monitor changes in bioavailability and flux of PCBs after activated carbon amendment to sediment in the field

Field and laboratory exposures of polyoxymethylene passive samplers to sediments and the water column were applied to monitor changes in bioavailability and flux of polychlorinated biphenyls (PCBs) following a pilot-scale amendment of activated carbon in Grasse River. Following amendment, reductions in passive sampler uptake tracked reductions in bioaccumulation in a freshwater invertebrate, which supports a biological basis for utilizing passive samplers for in situ site investigations following a remediation. Freely dissolved concentrations of PCBs were reduced in sediment pore waters compared to untreated sediments indicating reduced bioavailability of PCBs after activated carbon amendment. Freely dissolved PCB concentrations in sediment pore water in treated sites were also lower than overlying water concentrations indicating a reversal of the sediment from being a source to a sink of PCBs from the water column. These observations indicate that activated carbon amendment to sediment limits contaminant exposure to both the benthic and pelagic food webs through reductions in bioavailability and flux of PCBs into the water column.

Enteric fever in an HIV/AIDS patient: Atypical manifestations

Bloodstream infections with Salmonella typhi, is uncommon in human immunodeficiency virus (HIV)-infected persons. The symptoms in such patients are often non-specific and have a rather insidious onset and progression. We report a patient with sepsis and lower limb gangrene due to Salmonella typhi infection in an HIV-infected patient.

Pilot plant experiences using physical and biological treatment steps for the remediation of groundwater from a former MGP site

The production of manufactured gas at a site in Vienna, Austria led to the contamination of soil and groundwater with various pollutants including PAHs, hydrocarbons, phenols, BTEX, and cyanide. The site needs to be remediated to alleviate potential impacts to the environment. The chosen remediation concept includes the excavation of the core contaminated site and the setup of a hydraulic barrier to protect the surrounding aquifer. The extracted groundwater will be treated on-site. To design the foreseen pump-and-treat system, a pilot-scale plant was built and operated for 6 months. The scope of the present study was to test the effectiveness of different process steps, which included an aerated sedimentation basin, a submerged fixed film reactor (SFFR), a multi-media filter, and an activated carbon filter. The hydraulic retention time (HRT) was 7.0 h during normal flow conditions and 3.5h during high flow conditions. The treatment system was effective in reducing the various organic and inorganic pollutants in the pumped groundwater. However, it was also demonstrated that appropriate pre-treatment was essential to overcome problems with clogging due to precipitation of tar and sulfur compounds. The reduction of the typical contaminants, PAHs and BTEX, was more than 99.8%. All water quality parameters after treatment were below the Austrian legal requirements for discharge into public water bodies.

Particle-scale investigation of PAH desorption kinetics and thermodynamics from sediment

Dredged sediment from Milwaukee Harbor showed two primary classes of particles in the <2 mm size range: a lighter-density coal- and wood-derived fraction with 62% of total PAHs and a heavier-density sand, silt, and clay fraction containing the remaining 38% of the PAHs. Room-temperature PAH desorption kinetic studies on separated sediment fractions revealed slow desorption rates for the coal-derived particles and fast desorption rates for the clay/silt particles. The effect of temperature on PAH release was measured by thermal program desorption mass spectrometry to investigate the desorption activation energies for PAHs on the different sediment particles. Three activated diffusion-based models and an activated first-order rate model were used to describe the thermal desorption of PAHs for four molecular weight classes. PAH binding with the coal-derived particles was associated with high activation energies, typically in the range of 115-139 kJ/mol. PAHs bound to the clay/silt material had much lower activation energy, i.e., in the range of 37-41 kJ/ mol for molecular weight 202. Among the desorption models tested, a spherical diffusion model with PAHs located like a rind on the outer 1-3 microm region best described the PAH thermal desorption response for coal-derived particles. This internal PAH distribution pattern on coalderived particles is based on prior direct measurement of PAH locations at the subparticle scale. These studies reveal that heterogeneous particle types in sediment exhibit much different amounts and binding of PAHs. PAHs associated with coal-derived particles aged over several decades in the field appear to be far from reaching an equilibrium sorption state due to the extremely slow diffusivities through the polymer-like coal matrix. These results provide an improved mechanistic perspective for the understanding of PAH mobility and bioavailability in sediments.

Community care services: views of patients attending a geriatric day hospital

The NHS and Community Care reforms give increased emphasis to meeting the needs of patients as consumers of services, but little is known about patients' perceptions of services. In this study, we obtained the views of patients attending a geriatric day hospital about community care services and professional support; their knowledge of services, perceived unmet needs and perceptions of benefit. Forty-seven patients with a mental status score above 7/10 who attended the day hospital in a four week period were interviewed using structured questionnaires for consumer opinion, modified for this population. Patients had poor knowledge of services, especially of those which support carers and of private sources of support. When informed about the availability and purpose of local services, they recognised few unmet needs on average, less than one per patient, nearly always a need for social services, especially other forms of day care. Patients' perceptions of benefit from services and professional support were highest for day hospital care itself (98% of maximum possible benefit). There could be scope for the development of social work case management programmes in geriatric day hospitals; the methods used in this study provide a model for obtaining consumer opinion.

Transformation and regeneration of mung bean (Vigna radiata)

The procedure relied on a protocol in which shoot organogenesis was induced on cotyledons of mung bean genotypes selected for susceptibility to agrobacterium seems to work reproducibly if not efficiently. Approximately 4-5% of the shoots produced on the kanamycin selected cotyledons are transgenic based on assays on kanamycin resistance and GUS activity. This demonstrated that transformation and regeneration in mung bean are possible. However, raising the transformed plants in field condition is yet to be perfected.

Mitochondrial malic enzyme polymorphism in an Indian population

Mitochondrial malic enzyme (MEM) was examined by starch-gel electrophoresis in 182 brain samples from 102 male and 62 female subjects of Indian origin in Calcutta, Eastern India. The estimated gene frequencies of MEM were 0.56 for MEM1 and 0.44 for MEM2 in this population. There was no difference in gene frequency between the sexes. No deviation from the Hardy-Weinberg equilibrium was observed. MES did not show any polymorphism.