Global Patterns of Metal and Other Element Enrichment in Bog and Fen Peatlands

Peatlands are found on all continents, covering 3% of the global land area. However, the spatial extent and causes of metal enrichment in peatlands is understudied and no attempt has been made to evaluate global patterns of metal enrichment in bog and fen peatlands, despite that certain metals and rare earth elements (REE) arise from anthropogenic sources. We analyzed 368 peat cores sampled in 16 countries across five continents and measured metal and other element concentrations at three depths down to 70 cm as well as estimated cumulative atmospheric S deposition (1850-2009) for each site. Sites were assigned to one of three distinct broadly recognized peatland categories (bog, poor fen, and intermediate-to-moderately rich fen) that varied primarily along a pH gradient. Metal concentrations differed among peatland types, with intermediate-to-moderately rich fens demonstrating the highest concentrations of most metals. Median enrichment factors (EFs; a metric comparing natural and anthropogenic metal deposition) for individual metals were similar among bogs and fens (all groups), with metals likely to be influenced by anthropogenic sources (As, Cd, Co, Cu, Hg, Pb, and Sb) demonstrating median enrichment factors (EFs) > 1.5. Additionally, mean EFs were substantially higher than median values, and the positive correlation (< 0.40) with estimated cumulative atmospheric S deposition, confirmed some level of anthropogenic influence of all pollutant metals except for Hg that was unrelated to S deposition. Contrary to expectations, high EFs were not restricted to pollutant metals, with Mn, K and Rb all exhibiting elevated median EFs that were in the same range as pollutant metals likely due to peatland biogeochemical processes leading to enrichment of these nutrients in surface soil horizons. The global patterns of metal enrichment in bogs and fens identified in this study underscore the importance of these peatlands as environmental archives of metal deposition, but also illustrates that biogeochemical processes can enrich metals in surface peat and EFs alone do not necessarily indicate atmospheric contamination.

Variation in carbon and nitrogen concentrations among peatland categories at the global scale

Peatlands account for 15 to 30% of the world's soil carbon (C) stock and are important controls over global nitrogen (N) cycles. However, C and N concentrations are known to vary among peatlands contributing to the uncertainty of global C inventories, but there are few global studies that relate peatland classification to peat chemistry. We analyzed 436 peat cores sampled in 24 countries across six continents and measured C, N, and organic matter (OM) content at three depths down to 70 cm. Sites were distinguished between northern (387) and tropical (49) peatlands and assigned to one of six distinct broadly recognized peatland categories that vary primarily along a pH gradient. Peat C and N concentrations, OM content, and C:N ratios differed significantly among peatland categories, but few differences in chemistry with depth were found within each category. Across all peatlands C and N concentrations in the 10-20 cm layer, were 440 ± 85.1 g kg-1 and 13.9 ± 7.4 g kg-1, with an average C:N ratio of 30.1 ± 20.8. Among peatland categories, median C concentrations were highest in bogs, poor fens and tropical swamps (446-532 g kg-1) and lowest in intermediate and extremely rich fens (375-414 g kg-1). The C:OM ratio in peat was similar across most peatland categories, except in deeper samples from ombrotrophic tropical peat swamps that were higher than other peatlands categories. Peat N concentrations and C:N ratios varied approximately two-fold among peatland categories and N concentrations tended to be higher (and C:N lower) in intermediate fens compared with other peatland types. This study reports on a unique data set and demonstrates that differences in peat C and OM concentrations among broadly classified peatland categories are predictable, which can aid future studies that use land cover assessments to refine global peatland C and N stocks.

Periostracum of bivalve mollusk shells for sampling engineered metal nanoparticles: A case study of silver-based nanoparticles in Canada's experimental lake

Given the ability of engineered metal nanoparticles to be transformed in natural waters in unpredictable manners, various sampling methods must be developed. Here, we took a novel approach to collection silver nanoparticles (AgNPs) that involved the use of the intact periostracum, the outer proteinaceous organic layer, of freshwater unionid mussels Pyganodon sp. Eight adult mussels were collected in August 2019 from a small boreal lake (L222) at the International Institute for Sustainable Development - Experimental Lakes Area (northwestern Ontario), which had been dosed with 15 kg of poly(vinylpyrrolidone)-coated silver nanoparticles (PVP-AgNPs) in 2014-2015. Additionally, three adult mussels were collected from a control lake (L375). Numerous silica (SiO₂) diatom frustules were adhered to periostracum of all mussels. Intact periostracum promotes the formation of layer composed of diatoms and sand grains. The Ag content in soft tissues and shells of the mussels from L375 was as low as ≤ 0.1 μg/g. In mussels from L222, Ag concentrations in the periostracum of five shells were in detectable amounts (1-4 μg/g); in three shells concentrations were as high as 86, 122, and 494 μg/g. The underlying mineral shell is depleted in Ag (<0.1 μg/g). The Ag content in soft tissue organs (whole body) ranged from 44 to 191 μg/g. AgNPs occur on the surface of both periostracum and diatoms. Single AgNPs (d = 20-60 nm) were partly sulfidized to Ag₂S. The observed AgNPs often form aggregates with an average and a maximal size of circa 100 nm and 1.5 μm, respectively. Scraping small fragments of intact periostracum of unionid shell is non-lethal to mussels, and is easy to do under field conditions. This simple sampling protocol could be used to detect metal-based nanoparticles (engineered or accidental) with the use of unionid and dreissenid bivalves.

Pre-exposure to Cu2+ and CuO NPs leads to infection of caged blue mussels, Mytilus edulis L., by pathogenic microalga: Pilot study in the Lower St. Lawrence Estuary (Québec, Canada)

As evidenced from literature, exposure to non-lethal concentrations of dissolved copper (Cu²⁺) and copper nanoparticles (CuO NPs) promotes blue mussels susceptibility to various bacterial infections. We study whether pre-exposure (3.5 h) with CuSO₄ (100 μg Cu L^-1) and CuO NPs (1000 μg Cu L^-1) will result in infection of M. edulis L. with pathogenic microalga Coccomyxa sp. under field conditions. In May - September 2019, cages were installed in the site Metis-sur-Mer, St. Lawrence Estuary (QC, Canada) where the native mussel population is known to be infected with the pathogen. Untreated and pre-exposed mussels were grown for up to 130 days. Only the mussels pre-exposed to copper were infected by Coccomyxa. This finding allows proposing that occurrences of Coccomyxa-infected mussels worldwide might have an association with water pollution with xenobiotics. Pre-exposure of caged mussels to copper, as a protocol monitoring for other infectious agents, can be recommended to test.

Blended municipal compost and biosolids materials for mine reclamation: Long-term field studies to explore metal mobility, soil fertility and microbial communities

Application of stable soil amendments is often the key to successful phytostabilization and rehabilitation of mine tailings, and microbial guilds are primary drivers of many geochemical processes promoted by these amendments. Field studies were set up at a tailings management area near Sudbury, Ontario to examine performance of blends of lime stabilized municipal biosolids and compost at nine different rates over thick (1 m) municipal compost covers planted with agricultural crops. Based on biogeochemical variability of the substrates four and ten years after application of the initial compost cover, the experimental plots could be classified into three categories: "Low" rate (0-100 t ha^-1 biosolids), "Medium" rate (200-800 t ha^-1), and "High" rate (1600-3200 t ha^-1) treatments. The addition of biosolids materials to the thick compost cover at rates higher than 100 t ha^-1 significantly reduced C:N ratio of the substrates, available phosphorus, and some of the nutrient cations, while notably increasing inorganic carbon and the potential solubility of Ni and Cu. This suggests that increasing biosolids application rates may not equivalently ameliorate soil quality and geochemical stability. Correspondingly, microbial communities were altered by biosolids additions, further intensifying the negative impacts of biosolids on long-term efficiency of the initial compost cover. Abundance of cellulose, hemicellulose, and lignocellulose decomposers (as key drivers of mineralization and humification) was significantly reduced by "Medium" and "High" rate treatments. Most DNA sequences with high affinity to denitrifiers were detected in "High" rate treatments where geochemical conditions were optimal for higher microbial denitrification activities. These findings have implications for improving the long-term efficiency of reclamation and environmental management programs in mine tailings of northern temperate climates.

Organic amendments potentially stabilize metals in smelter contaminated Arctic soils: An incubation study

The long-term emission impacts of the nickel processing industry in the Kola Peninsula, the largest source of sulfur dioxide and heavy metals emissions in Northern Europe, have created vast technogenic barrens near the mineral industry complexes. The pace of rehabilitation using the improved remediation technologies to enhance sustainable environmental management and regional economic development is of crucial social and economic importance. In a 120-day incubation experiment, we evaluated the prospects for the restoration of two soils at different degradation stages via carbon pool regulation comparing to mineral ameliorants - NPK fertilizer, and liming agent. Organic additives used included a humic preparation based on an alkaline brown coal extract, wood-derived biochar, and peat-derived gel, supplied by mycorrhizae fungi. The results demonstrate that the selected organic amendments are suitable for restoration of acidic metal contaminated soils. Specifically, the treatments provided a measurable increase in soil carbon content, a marked decrease in acidity, a decrease in extractable metal contents, together with an enhanced nutrient uptake and vegetative growth. A stabilization effect increased from biochar to peat-gel, liming agent and humic preparation, with an accompanying increase in soil pH. Although biochar showed a reduced ability to metal stabilization, the associated treatments were the most productive. The most effective amendments in multi-metallic contaminated soils need to be able to stabilize bioavailability of metals, adjust pH to the optimum for plant growth, and regulate nutrient consumption.

First report of signs of infection by Coccomyxa-like algae in wild blue mussels, Mytilus spp., in the Gulf of Maine (USA, Maine)

In August 2019, visual inspection of intertidal zones of the Gulf of Maine (ME, USA) revealed young and adult wild blue mussels, Mytilus spp., in Alley Bay (Jonesport area) with the distinctive L-shaped shell deformity (LSSD) and green spots (GS) in the mantle and adductor muscle. LSSD is a characteristic sign of current or previous mussel infection by photosynthetic unicellular alga from the group Coccomyxa, while GS are algal colonies. Based on these findings, this study represents the first report of infection signs by pathogenic Coccomyxa-like algae in mussels from the coastal waters of the Northeastern United States, providing a base for future large scale monitoring of the alga in the region.

Rhizobioaugmentation of Casuarina glauca with N-fixing actinobacteria Frankia decreases enzymatic activities in wastewater irrigated soil: effects of Frankia on C. glauca growth

The use of wastewater for irrigation in agroforestry is cost-effective for water management. It is well established that rhizospheric microorganisms such as N₂-fixing bacteria are able to modulate rhizobioaugmention and to boost phyoremediation process. To date, no study has been conducted to evaluate biological effects of rhizobioaugmentation in Casuarina glauca trees induced by their symbiont N-fixing actinobacteria of the genus Frankia. The objective of the present study was to evaluate the main effects of rhizobioaugmentation on the biological activity in the C. glauca's rhizosphere and on C. glauca growth in soils irrigated with industrial wastewater. Two Frankia strains (BMG5.22 and BMG5.23) were used in a single or dual inoculations of C. glauca seedlings irrigated with industrial wastewater. Soil enzymes activity related to carbon, phosphorus, sulfur and nitrogen cycling were measured. Results revealed that the BMG5.22 Frankia strain increases significantly the size (dry weight) of C. glauca shoots and roots while dual inoculation increased significantly the root length. Surprisingly, β-glucosidase (BG), cellobiohydrolase (CBH), β-N-acetylglucosaminidase (NAGase), aryl sulfatase (AS), acid phosphatase (AP), alkaline phosphatase (AlP), glycine aminopeptidase (GAP), leucine aminopeptidase (LAP), and peroxidase (PER) activity in the rhizosphere decreased significantly in soils treated with the two strains of symbionts. This suggests no positive correlations between enzymatic activity and C. glauca growth.

Practical advice on monitoring of U and Pu with marine bivalve mollusks near the Fukushima Daiichi Nuclear Power Plant

Following the Fukushima Daiichi nuclear power plant accident in 2011, some marine radionuclide monitoring studies report a lack of evidence for contamination of Japanese coastal waters by U and Pu, or state that marine contamination by them was negligible. Nevertheless, Fukushima-derived U and Pu were reported as associated with Cs-rich microparticles (CsMPs) found in local soil, vegetation, and river/lake sediments. Over time, CsMPs can be transported to the sea via riverine runoff where actinides, as expected, will leach. We recommend establishing a long-term monitoring of U and Pu in the nearshore area of the Fukushima Prefecture using marine bivalve mollusks; shells, byssal threads and soft tissues should all be analyzed. Here, based on results from Th biosorption experiments, we propose that U and Pu could be present at concentrations several times higher in shells with a completely destroyed external shell layer (periostracum) than in shells with intact periostracum.

Shell deformity as a marker for retrospective detection of a pathogenic unicellular alga, Coccomyxa sp., in mytilid mussels: A first case study and research agenda

An L-shaped shell deformity (LSSD) on the posterior shell edge is known exclusively in wild mytilid mussels infected with photosynthetic Coccomyxa-like algae. LSSD forms due to the appearance of extra shell material; it only occurs if the mussel is heavily infected with the alga. Traditionally, observation of high amount of the green spots (algal colonies) on a large area of host soft tissues (most of the mantle and in adductor muscle) has been used to indicate a high infection rate. We examined 300 Mytilus spp. (100 small, 20-30 mm; 200 large, 40-60 mm) with a high degree of LSSD (parameter "d" > 5 mm) from the Lower St. Lawrence Estuary (Québec, Canada). Green spots were absent in two large mussels, and were only present along the mantle posterior edge in 14 large mussels; other individuals had high infection levels. Our observations suggest that some individuals could be in a state of remission, or, even more optimistically - mussels may be able to resist the pathogen. LSSD is the stable through-time marker for detection of mytilid mussels that are or were infected with Coccomyxa algae, and, thus, may provide information for the study of mussel immunity and control of alga distribution/migration in coastal waters worldwide.

Impact of social care supply on healthcare utilisation by older adults: a systematic review and meta-analysis

Objective

to investigate the impact of the availability and supply of social care on healthcare utilisation (HCU) by older adults in high income countries.

Design

systematic review and meta-analysis.

Data sources

medline, EMBASE, Scopus, Health Management Information Consortium, Cochrane Database of Systematic Reviews, NIHR Health Technology Assessment, NHS Economic Evaluation Database, Database of Abstracts of Reviews of Effectiveness, SCIE Online and ASSIA. Searches were carried out October 2016 (updated April 2017 and May 2018). (PROSPERO CRD42016050772).

Study selection

observational studies from high income countries, published after 2000 examining the relationship between the availability of social care (support at home or in care homes with or without nursing) and healthcare utilisation by adults >60 years. Studies were quality assessed.

Results

twelve studies were included from 11,757 citations; ten were eligible for meta-analysis. Most studies (7/12) were from the UK. All reported analysis of administrative data. Seven studies were rated good in quality, one fair and four poor. Higher social care expenditure and greater availability of nursing and residential care were associated with fewer hospital readmissions, fewer delayed discharges, reduced length of stay and expenditure on secondary healthcare services. The overall direction of evidence was consistent, but effect sizes could not be confidently quantified. Little evidence examined the influence of home-based social care, and no data was found on primary care use.

Conclusions

adequate availability of social care has the potential to reduce demand on secondary health services. At a time of financial stringencies, this is an important message for policy-makers.

Blended pulp mill, forest humus and mine residual material Technosols for mine reclamation: A growth-chamber study to explore the role of physiochemical properties of substrates and microbial inoculation on plant growth

A growth chamber trial was conducted to investigate the effects of blends of pulp and paper mill residuals and forest humus on soil properties, microbial communities and germination rate and biomass production of annual ryegrass (Lolium multiflorum) in both acid-producing and neutral to mildly alkaline mine tailings in a mine reclamation context. The organic residual amendments improved the nutritional status of the tailings substrates, and increased pH in acid-generating tailings, leading to higher germination rates and improved plant growth. A trace addition (<0.02% of sludge by dry weight) of natural forest floor material as a microbial inoculum to the sludge could increase plant biomass up to four-fold. The effects of sludge application on bioavailability of metals were variable, with the concentration of soluble copper (Cu) and nickel (Ni) increasing in some of the substrates following organic amendments. Addition of paper mill residuals to mine tailings modified the microbial communities observed in the oligotrophic tailings with the majority of DNA sequences in the sludge amended substrates being found to be closely related to heterotrophic bacterial species rather than the chemolithotrophic communities that dominate tailings environments.

Rates and processes affecting As speciation and mobility in lake sediments during aging

Sediments from an arsenic (As) contaminated groundwater vent site were used to investigate As(III) binding, transformation and redistribution in native and iron oxide amended lake sediments using aging spiked batch reactions and a sequential extraction procedure that maintains As(V) and As(III) speciation. In the native sediments, fractionation analysis revealed that 10% of the spiked As(III) remained intact after a 32-day aging experiment and was predominantly adsorbed to the strongly sorbed (NH₄H₂PO₄ extractable) and amorphous Fe oxide bound (H₃PO₄ extractable) fractions. Kinetic modelling of the experimental results allowed identifying the dominant reaction path for depletion of dissolved As(III) to As(III) absorbed on to the solid phase, followed by oxidation in the solid phase. Arsenite was initially adsorbed primarily to the easily exchangeable fraction ((NH₄)₂SO₄ extractable), then rapidly transformed into As(V) and redistributed to the strongly sorbed and amorphous Fe oxide bound fractions. Oxidation of As(III) in recalcitrant fractions was less efficient. The iron oxide amendments illustrated the controls that iron oxides can have on As(III) binding and transformation rates. In goethite amended samples As(III) oxidation was faster and primarily occurred in the strongly sorbed and amorphous Fe oxide bound fractions. In these samples, 19.3μg Mn was redistributed (compared to the native sediment) from the easily exchangeable and crystalline Fe oxide bound fractions to the strongly sorbed and amorphous Fe oxide bound fractions, indicating that goethite may act as a catalyst for Mn(II) oxidation, thereby producing sorbed Mn(III/IV), which then appears to be involved in rapidly oxidizing As(III).

Variation in whole DNA methylation in red maple (Acer rubrum) populations from a mining region: association with metal contamination and cation exchange capacity (CEC) in podzolic soils

Although a number of publications have provided convincing evidence that abiotic stresses such as drought and high salinity are involved in DNA methylation reports on the effects of metal contamination, pH, and cation exchange on DNA modifications are limited. The main objective of the present study is to determine the relationship between metal contamination and Cation exchange capacity (CEC) on whole DNA modifications. Metal analysis confirms that nickel and copper are the main contaminants in sampled sites within the Greater Sudbury Region (Ontario, Canada) and liming has increased soil pH significantly even after 30 years following dolomitic limestone applications. The estimated CEC values varied significantly among sites, ranging between 1.8 and 10.5 cmol(+) kg^-1, with a strong relationship being observed between CEC and pH (r = 0.96**). Cation exchange capacity, significantly lower in highly metal contaminated sites compared to both reference and less contaminated sites, was higher in the higher organic matter limed compared to unlimed sites. There was a significant variation in the level of cytosine methylation among the metal-contaminated sites. Significant and strong negative correlations between [5mdC]/[dG] and bioavailable nickel (r = -0.71**) or copper (r = -0.72**) contents were observed. The analysis of genomic DNA for adenine methylation in this study showed a very low level of [6N-mdA]/dT] in Acer rubrum plants analyzed ranging from 0 to 0.08%. Significant and very strong positive correlation was observed between [6N-mdA]/dT] and soil bioavailable nickel (r = 0.78**) and copper (r = 0.88**) content. This suggests that the increased bioavailable metal levels associated with contamination by nickel and copper particulates are associated with cytosine and adenine methylation.

Validation of an updated fractionation and indirect speciation procedure for inorganic arsenic in oxic and suboxic soils and sediments

A sequential extraction procedure (SEP) for the speciation analysis of As(III) and As(V) in oxic and suboxic soils and sediments was validated using a natural lake sediment and three certified reference materials, as well as spike recoveries of As(III) and As(V). Many of the extraction steps have been previously validated making the procedure useful for comparisons to similar previous SEP studies. The novel aspect of this research is the validation for the SEP to maintain As(III) and As(V) species. The proposed five step extraction procedure includes the extraction agents (NH₄)₂SO₄, NH₄H₂PO₄, H₃PO₄ + NH₂OH·HCl, oxalate + ascorbic acid (heated), and HNO₃ + HCl + HF, targeting operationally defined easily exchangeable, strongly sorbed, amorphous Fe oxide bound, crystalline Fe oxide bound, and residual As fractions, respectively. The third extraction step, H₃PO₄ + NH₂OH·HCl, has not been previously validated for fraction selectivity. We present evidence for this extraction step to target As complexed with amorphous Fe oxides when used in the SEP proposed here. All solutions were analyzed on ICP-MS. The greatest concentrations of As were extracted from the amorphous Fe oxide fraction and the dominant species was As(V). Lake sediment materials were found to have higher As(III) concentrations than the soil materials. Because different soils/sediments have different chemical characteristics, maintenance of As species during extractions must be validated for specific soil/sediment types using spiking experiments.

Multi-dimensional water quality assessment of an urban drinking water source elucidated by high resolution underwater towed vehicle mapping

Spatial surveys of Ramsey Lake, Sudbury, Ontario water quality were conducted using an innovative underwater towed vehicle (UTV) equipped with a multi-parameter probe providing real-time water quality data. The UTV revealed underwater vent sites through high resolution monitoring of different spatial chemical characteristics using common sensors (turbidity, chloride, dissolved oxygen, and oxidation/reduction sensors) that would not be feasible with traditional water sampling methods. Multi-parameter probe vent site identification is supported by elevated alkalinity and silica concentrations at these sites. The identified groundwater vent sites appear to be controlled by bedrock fractures that transport water from different sources with different contaminants of concern. Elevated contaminants, such as, arsenic and nickel and/or nutrient concentrations are evident at the vent sites, illustrating the potential of these sources to degrade water quality.

Radionuclide release from simulated waste material after biogeochemical leaching of uraniferous mineral samples

Biogeochemical mineral dissolution is a promising method for the released of metals in low-grade host mineralization that contain sulphidic minerals. The application of biogeochemical mineral dissolution to engineered leach heap piles in the Elliot Lake region may be considered as a promising passive technology for the economic recovery of low grade Uranium-bearing ores. In the current investigation, the decrease of radiological activity of uraniferous mineral material after biogeochemical mineral dissolution is quantified by gamma spectroscopy and compared to the results from digestion/ICP-MS analysis of the ore materials to determine if gamma spectroscopy is a simple, viable alternative quantification method for heavy nuclides. The potential release of Uranium (U) and Radium-226 ((226)Ra) to the aqueous environment from samples that have been treated to represent various stages of leaching and passive closure processes are assessed. Dissolution of U from the solid phase has occurred during biogeochemical mineral dissolution in the presence of Acidithiobacillus ferrooxidans, with gamma spectroscopy indicating an 84% decrease in Uranium-235 ((235)U) content, a value in accordance with the data obtained by dissolution chemistry. Gamma spectroscopy data indicate that only 30% of the (226)Ra was removed during the biogeochemical mineral dissolution. Chemical inhibition and passivation treatments of waste materials following the biogeochemical mineral dissolution offer greater protection against residual U and (226)Ra leaching. Pacified samples resist the release of (226)Ra contained in the mineral phase and may offer more protection to the aqueous environment for the long term, compared to untreated or inhibited residues, and should be taken into account for future decommissioning.

What percentage of the oceanic mixed layer is accessible to marine Lidar? Global and the Gulf of Mexico prospective

The oceanic mixed layer is a nearly homogenous region of the upper ocean which, in principle, has a little or no variation in turbulence strength, temperature or density with depth. This layer mediates oceanic fluxes of gas, momentum and heat. Here, based on the chosen marine Lidar system, we have carried out estimates of the depth penetration of the Lidar when compared to the local mixed layer depth. On average, we have found that at least 50% of the global oceanic mixed layer depth is accessible to the Lidar observations. When operating in a single scattering mode, which is more attenuating but more amenable to analysis, the modeled Lidar was found to access 0.4 of global mixed layer depth in half of the cases. The single scattering Lidar was found to access a large fraction of the equatorial mixed layer - a region very important when addressing global climatic issues. In a coastal environment such as the Gulf of Mexico the single scattering Lidar was found to penetrate upper half of the mixed layer, underscoring the potential for Lidar to address environmental issues there.

Systematic review of international evidence on the effectiveness and costs of paediatric home care for children and young people who are ill

Promoting 'care closer to home' for ill children is a policy and practice objective internationally. Progress towards this goal is hampered by a perceived lack of evidence on effectiveness and costs. The aim of the work reported here was to establish the strength of current international evidence on the effectiveness and costs of paediatric home care by updating and extending an earlier systematic review. A systematic review following Centre for Reviews and Dissemination guidelines involved updating electronic searches, and extending them to cover paediatric home care for short-term acute conditions. Twenty-one databases were searched from 1990 to April 2007. Hand searching was also carried out. Pairs of team members, guided by an algorithm, selected randomized controlled trials (RCTs), other comparative studies and studies including health economics data. A third reviewer resolved any disagreements. The quality of RCTs was assessed, but a 'best-evidence' approach was taken overall. Data were extracted into specifically designed spreadsheets and a second team member checked all data. Narrative synthesis was used throughout. This paper reports findings from RCTs and studies with health economics data. In total, 16 570 publications were identified after de-duplication. Eleven new RCTs (reported in 17 papers) and 20 papers with health economics data were included and reviewed. Evidence on costs and effectiveness of paediatric home care has not grown substantially since the previous review, but this updated review adds weight to the conclusion that it can deliver equivalent clinical outcomes for children and not impose a greater burden on families. Indeed, in some cases, there is evidence of reduced burden and costs for families compared with hospital care. There is also growing evidence, albeit based on weaker evidence, that paediatric home care may reduce costs for health services, particularly for children with complex and long-term needs.

Effects of estimates from different geochemical models on metal fate predicted by coupled speciation-fate models

Coupled metal speciation-fate models are an improvement over stand-alone fate-transport models for accurately assessing metal fate and transport. These coupled models estimate fate-controlling partition coefficients using geochemical speciation/complexation models. Commercially available geochemical models are practical options for a two-step, loose coupling with fate-transport models. These models differ in their partitioning estimates because of differences in assumptions, databases, and so on. The present study examines the effects of differences in estimates from geochemical models on estimates of cationic metal fate using two geochemical models: the Windermere humic aqueous model (WHAM) and the minicomputer equilibrium+ model (MINEQL+). The results from each geochemical model were used as input to the fate module of TRANSPEC (a general, coupled metal transport and speciation model). The two versions of the TRANSPEC model were then used to assess the fate of five cationic metals (Cd, Cu, Ni, Pb, and Zn) in Ross Lake (Flin Flon, MB, Canada; alkaline, eutrophic, mine impacted), Kelly Lake (Sudbury, ON, Canada; circumneutral, mesotrophic, mine influenced), and Lake Tantaré (Quebec City, QC, Canada; acidic, oligotrophic, pristine). For relatively soluble metals (Cd, Ni, and Zn), the WHAM and MINEQL+ estimates of speciation/complexation were similar for Ross and Kelly lakes but differed for Lake Tantaré. These differences, however, did not result in significant differences in overall fate estimates. Marked differences were observed between the WHAM and MINEQL+ estimates of partition coefficient, Kd, for more particle-reactive Cu and Pb that translated into the greatest impact on fate in mesotrophic Kelly Lake, in which particle movement is important for fate.

Emergency (999) calls to the ambulance service that do not result in the patient being transported to hospital: an epidemiological study

OBJECTIVE

To describe the demographic and clinical characteristics of patients who are not transported to hospital after an emergency (999) call to the East Midlands Ambulance Service, the reason for non-transportation, and the priority assigned when the ambulance is dispatched.

METHODS

The first 500 consecutive non-transported patients from 1 March 2000 were identified from the ambulance service command and control data. Epidemiological and clinical data were then obtained from the patient report form completed by the attending ambulance crew and compared with the initial priority dispatch (AMPDS) code that determined the urgency of the ambulance response.

RESULTS

Data were obtained for 498 patients. Twenty six per cent of these calls were assigned an AMPDS delta code (the most urgent category) at the time the call was received. Falls accounted for 34% of all non-transported calls. This group of patients were predominantly elderly people (over 70 years old) and the majority (89%) were identified as less urgent (coded AMPDS alpha or bravo) at telephone triage. The mean time that an ambulance was committed to each non-transported call was 34 minutes.

CONCLUSIONS

This study shows that falls in elderly people account for a significant proportion of non-transported 999 calls and are often assigned a low priority when the call is first received. There could be major gains if some of these patients could be triaged to an alternative response, both in terms of increasing the ability of the ambulance service to respond faster to clinically more urgent calls and improving the cost effectiveness of the health service. The AMPDS priority dispatch system has been shown to be sensitive but this study suggests that its specificity may be poor, resulting in rapid responses to relatively minor problems. More research is required to determine whether AMPDS prioritisation can reliably and safely identify 999 calls where an alternative to an emergency ambulance would be a more appropriate response.