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| 3. |
- White, S. A., et al.
(författare)
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Natural attenuation of large anthropogenic nitrate loads in a subtropical stream revealed by delta N-15 and delta O-18
- 2021
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 598
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen pollution in subtropical waters is rapidly increasing due to land-use change, but specific sources, transformations, and attenuation rates remain understudied compared to cooler temperate catchments. Here, we quantify high-resolution nitrate (NO3--N) loads, sources and natural attenuation in a subtropical creek in Australia over contrasting hydrological conditions. We observed large creek NO3-N loads (ranging from 44 to 2938 mu mol m(-2) catchment d(-1)) exceeding the bottom-up estimates of nitrogen input to the catchment at the most upstream sites. Stable isotope natural abundances (delta N-15 and delta O-18 in NO3--N) and Bayesian analysis revealed that greywater was the dominant source accounting for similar to 55% of NO3--N in the upper creek, but fertilisers (similar to 29%) and rainfall (similar to 16%) were also relevant NO3--N sources. NO3--N loads at the most downstream site were only 0.2-9.7% of loads at the most upstream site. The resulting NO3--N attenuation efficiency (mainly via denitrification) was 52-84% of original upstream load per km of creek, depending on hydrological conditions. This large capacity to attenuate NO3--N during dry and first-flush events exceeds the attenuation found in temperate creeks subject to several decades of pollution in the northern hemisphere. During periods of high water flow and saturated soils, high NO3--N loads were exported downstream, turning the creek from a natural bioreactor to a system resembling a flow-through pipe. In spite of effective natural nitrogen attenuation providing a valuable ecosystem service, concentrations and loads remained well above expected for natural systems and water quality guidelines. Overall, our results highlight the need for modifying fertiliser use, capturing nitrogen on farms and reducing greywater nitrogen to prevent significant losses to subtropical waterways.
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| 4. |
- Woodrow, R. L., et al.
(författare)
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Nitrous oxide hot moments and cold spots in a subtropical estuary: Floods and mangroves
- 2022
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Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714. ; 264
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Tidskriftsartikel (refereegranskat)abstract
- Flood events can transport large nitrogen loads to the ocean in short periods with the potential to produce significant nitrous oxide (N2O) emissions along an estuarine gradient. Here, we evaluate temporal and spatial N2O air-water fluxes from both seasonal, and flood-event timescales in an urban subtropical estuary surrounded by mangroves (Coffs Creek, Australia). Overall, the estuary was a minor atmospheric source of N2O with emissions of 3.9 ± 1.2 μmol m−2 d−1. However, the mangrove-dominated lower estuary was a sink of N2O in the dry months (−5.4 ± 2.2 μmol m−2 d−1), then a source in the wet months (11.7 ± 1.6 μmol m−2 d−1) and also during an eight-day flood event (66.9 ± 9.8 μmol m−2 d−1). The flood event drove changes in estuary N2O dynamics, creating a ‘hot moment’ with the highest N2O emissions following the transport of nitrate + nitrite (NOX) from the modified catchment. The hot moment coincided with a 13-fold increase in mean daily N2O emissions and increased annual net emissions estimates to the atmosphere by 41%. In the mangrove-dominated creek sections, N2O was consumed in the dry conditions (cold spots). Seasonal variation was prominent in the attenuation and consumption of N2O in the mangrove dominated sections of the creek, while flood events potentially reduce natural creek NOX attenuation capacity and elevate N2O emissions. Without observation s in both seasonal and episodic rainfall timeframes, estuarine N2O studies in subtropical regions may underestimate N2O emissions and budgets. © 2021 Elsevier Ltd
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| 5. |
- Conrad, S. R., et al.
(författare)
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Cryptic night-time trace metal and metalloid contamination in an intensively cultivated coastal catchment
- 2021
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491. ; 276
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Tidskriftsartikel (refereegranskat)abstract
- Detailed, high resolution time-series observations were performed to investigate sources, diel cycling, natural attenuation, and loadings of dissolved trace metals/metalloids in a subtropical headwater stream draining intensive horticulture in Australia. A transect of similar to 3 km away from the source (farms) showed >75% reduction in concentration and loads of most trace elements. Mercury and arsenic had elevated loads downstream relative to other elements. Hourly time-series sampling revealed elevated creek discharge at night, accompanied by elevated nickel, selenium, copper, and mercury loads. Inputs from groundwater or treated sewage used for irrigation within the catchment are likely sources. Groundwater bore and treated sewage samples were highly contaminated with either zinc, copper, or mercury. Comparisons of daily and hourly samples indicated common sampling strategies can underestimate horticultural contaminant loadings. Load estimates for mercury and copper derived from hourly samples were 1.6- to 7- fold greater than loads from daily sample data collected over 79 days with varying rainfall. These high contaminant concentrations and loads are of concern to food products receiving irrigation and protected waterbodies downstream. (C) 2021 Elsevier Ltd. All rights reserved.
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| 6. |
- Conrad, S. R., et al.
(författare)
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Land use change increases contaminant sequestration in blue carbon sediments
- 2023
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 873
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Tidskriftsartikel (refereegranskat)abstract
- Coastal blue carbon habitats perform many important environmental functions, including long-term carbon and an-thropogenic contaminant storage. Here, we analysed twenty-five 210Pb-dated mangrove, saltmarsh, and seagrass sed-iment cores from six estuaries across a land-use gradient to determine metal, metalloid, and phosphorous sedimentary fluxes. Cadmium, arsenic, iron, and manganese had linear to exponential positive correlations between concentrations, sediment flux, geoaccumulation index, and catchment development. Increases in anthropogenic development (agricul-tural or urban land uses) from > 30 % of the total catchment area enhanced mean concentrations of arsenic, copper, iron, manganese, and zinc between 1.5 and 4.3-fold. A similar to 30 % anthropogenic land-use was the threshold in which blue carbon sediment quality begins to be detrimentally impacted on an entire estuary scale. Fluxes of phosphorous, cadmium, lead, and aluminium responded similarly, increasing 1.2 to 2.5-fold when anthropogenic land-use increased by at least 5 %. Exponential increases in phosphorus flux to estuary sediments seem to precede eutrophication as ob-served in more developed estuaries. Overall, multiple lines of evidence revealed how catchment development drives blue carbon sediment quality across a regional scale.
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| 7. |
- Goode, Chloe K., et al.
(författare)
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Control of high-speed jumps in muscle and spring actuated systems : a comparative study of take-off energetics in bush-crickets (Mecopoda elongata) and locusts (Schistocerca gregaria)
- 2023
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Ingår i: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology. - : Springer Nature. - 0174-1578 .- 1432-136X. ; 193, s. 597-605
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Tidskriftsartikel (refereegranskat)abstract
- The Orthoptera are a diverse insect order well known for their locomotive capabilities. To jump, the bush-cricket uses a muscle actuated (MA) system in which leg extension is actuated by contraction of the femoral muscles of the hind legs. In comparison, the locust uses a latch mediated spring actuated (LaMSA) system, in which leg extension is actuated by the recoil of spring-like structure in the femur. The aim of this study was to describe the jumping kinematics of Mecopoda elongata (Tettigoniidae) and compare this to existing data in Schistocerca gregaria (Acrididae), to determine differences in control of rotation during take-off between similarly sized MA and LaMSA jumpers. 269 jumps from 67 individuals of M. elongata with masses from 0.014 g to 3.01 g were recorded with a high-speed camera setup. In M. elongata, linear velocity increased with mass0.18 and the angular velocity (pitch) decreased with mass−0.13. In S. gregaria, linear velocity is constant and angular velocity decreases with mass−0.24. Despite these differences in velocity scaling, the ratio of translational kinetic energy to rotational kinetic energy was similar for both species. On average, the energy distribution of M. elongata was distributed 98.8% to translational kinetic energy and 1.2% to rotational kinetic energy, whilst in S. gregaria it is 98.7% and 1.3%, respectively. This energy distribution was independent of size for both species. Despite having two different jump actuation mechanisms, the ratio of translational and rotational kinetic energy formed during take-off is fixed across these distantly related orthopterans.
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| 10. |
- Kamel, Ihab R., et al.
(författare)
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N-Methyl-D-Aspartate (NMDA) Antagonists-S(+)-ketamine, Dextrorphan, and Dextromethorphan-Act as Calcium Antagonists on Bovine Cerebral Arteries
- 2008
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Ingår i: Journal of Neurosurgical Anesthesiology. - 1537-1921. ; 20:4, s. 241-248
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Tidskriftsartikel (refereegranskat)abstract
- Ketamine an intravenous anesthetic and a major drug of abuse, is a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist. Ketamine's enantiomer. S(+)-ketamine, acts stereoselectively on neuronal NMDA receptors. The purpose of this in vitro study was to compare the direct effects of S(+)-ketamine. 2 other noncompetitive NMDA receptor antagonists (dextrorphan and dextromethorphan), and the calcium entry blocker nimodipine on the cerebral vasculature, using bovine middle cerebral arterics as an experimental model. Arterial rings were mounted in isolated tissue chambers equipped with isometric tension transducers to obtain pharmacologic dose-response curves. In the absence of exogenous vasoconstrictor, the NMDA antagonists or nimodipine had negligible effects oil cerebral arterial tone. When rings were preconstricted with either potassium or the stable thromboxane A(2) mimetic U46619. the NMDA antagonists and nimodipine each produced dose-dependent relaxation. Prior endothelial stripping had no effect on subsequent drug-induced relaxation of K+-constricted rings. In Ca2+-deficient media containing either potassium or U46619. the NMDA antagonists and nimodipine each produced competitive inhibition of subsequent Ca2+ induced constriction. In additional experiments, arterial strips were mounted in isolated tissue chambers to directly measure calcium uptake, using (45)calcium (Ca-45) as a radioactive tracer. The NMDA antagonists and nimodipine each blocked potasium-stimulated or U46619-stilmulated Ca-45 uptake into arterial strips. These results indicate that S(+)-ketamine, dextrorphan, arteries by acting as calcium antagonists; they all inhibit Ca-45 uptake through both potential-operated (potassium) and receptor-operated (U46619) channels in cerebrovascular smooth muscle.
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| 11. |
- Mansoor, Rashid, et al.
(författare)
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Haematological consequences of acute uncomplicated falciparum malaria : a WorldWide Antimalarial Resistance Network pooled analysis of individual patient data
- 2022
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Ingår i: BMC Medicine. - : Springer Nature. - 1741-7015. ; 20:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundPlasmodium falciparum malaria is associated with anaemia-related morbidity, attributable to host, parasite and drug factors. We quantified the haematological response following treatment of uncomplicated P. falciparum malaria to identify the factors associated with malarial anaemia.MethodsIndividual patient data from eligible antimalarial efficacy studies of uncomplicated P. falciparum malaria, available through the WorldWide Antimalarial Resistance Network data repository prior to August 2015, were pooled using standardised methodology. The haematological response over time was quantified using a multivariable linear mixed effects model with nonlinear terms for time, and the model was then used to estimate the mean haemoglobin at day of nadir and day 7. Multivariable logistic regression quantified risk factors for moderately severe anaemia (haemoglobin < 7 g/dL) at day 0, day 3 and day 7 as well as a fractional fall >= 25% at day 3 and day 7.ResultsA total of 70,226 patients, recruited into 200 studies between 1991 and 2013, were included in the analysis: 50,859 (72.4%) enrolled in Africa, 18,451 (26.3%) in Asia and 916 (1.3%) in South America. The median haemoglobin concentration at presentation was 9.9 g/dL (range 5.0-19.7 g/dL) in Africa, 11.6 g/dL (range 5.0-20.0 g/dL) in Asia and 12.3 g/dL (range 6.9-17.9 g/dL) in South America. Moderately severe anaemia (Hb < 7g/dl) was present in 8.4% (4284/50,859) of patients from Africa, 3.3% (606/18,451) from Asia and 0.1% (1/916) from South America. The nadir haemoglobin occurred on day 2 post treatment with a mean fall from baseline of 0.57 g/dL in Africa and 1.13 g/dL in Asia. Independent risk factors for moderately severe anaemia on day 7, in both Africa and Asia, included moderately severe anaemia at baseline (adjusted odds ratio (AOR) = 16.10 and AOR = 23.00, respectively), young age (age < 1 compared to >= 12 years AOR = 12.81 and AOR = 6.79, respectively), high parasitaemia (AOR = 1.78 and AOR = 1.58, respectively) and delayed parasite clearance (AOR = 2.44 and AOR = 2.59, respectively). In Asia, patients treated with an artemisinin-based regimen were at significantly greater risk of moderately severe anaemia on day 7 compared to those treated with a non-artemisinin-based regimen (AOR = 2.06 [95%CI 1.39-3.05], p < 0.001).ConclusionsIn patients with uncomplicated P. falciparum malaria, the nadir haemoglobin occurs 2 days after starting treatment. Although artemisinin-based treatments increase the rate of parasite clearance, in Asia they are associated with a greater risk of anaemia during recovery.
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| 12. |
- Vallejo‐Marín, Mario, Professor, et al.
(författare)
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Biomechanical properties of non-flight vibrations produced by bees
- 2024
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 227:12
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Tidskriftsartikel (refereegranskat)abstract
- Bees use thoracic vibrations produced by their indirect flight muscles for powering wingbeats in flight, but also during mating, pollination, defence and nest building. Previous work on non-flight vibrations has mostly focused on acoustic (airborne vibrations) and spectral properties (frequency domain). However, mechanical properties such as the vibration's acceleration amplitude are important in some behaviours, e.g. during buzz pollination, where higher amplitude vibrations remove more pollen from flowers. Bee vibrations have been studied in only a handful of species and we know very little about how they vary among species. In this study, we conducted the largest survey to date of the biomechanical properties of non-flight bee buzzes. We focused on defence buzzes as they can be induced experimentally and provide a common currency to compare among taxa. We analysed 15,000 buzzes produced by 306 individuals in 65 species and six families from Mexico, Scotland and Australia. We found a strong association between body size and the acceleration amplitude of bee buzzes. Comparison of genera that buzz-pollinate and those that do not suggests that buzzpollinating bees produce vibrations with higher acceleration amplitude. We found no relationship between bee size and the fundamental frequency of defence buzzes. Although our results suggest that body size is a major determinant of the amplitude of non-flight vibrations, we also observed considerable variation in vibration properties among bees of equivalent size and even within individuals. Both morphology and behaviour thus affect the biomechanical properties of non-flight buzzes.
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| 13. |
- Wadnerkar, P. D., et al.
(författare)
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Nitrate removal and nitrous oxide production from hothouse effluent draining to a pipe bioreactor
- 2022
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Ingår i: Ecological Engineering. - : Elsevier BV. - 0925-8574. ; 178
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural hothouses are intensive food production systems relying on high fertilization and irrigation. Runoff from hothouses can contain high levels of nitrogen (N) and drain into streams. Here, we investigate the effectiveness of buried, inline woodchip bioreactors constructed using PVC pipes in removing nitrate (NO3−-N) and the possibility of pollution swapping from nitrate to the greenhouse gas nitrous oxide (N2O). Mean dissolved NO3−-N removal and N2O gas production were 6.0 ± 5.2 g N m−3 h−1 (0.9–12.3 g N m−3 h−1), and 35.1 ± 31.4 mg N L−1 h−1 (14–83 mg N L−1 h−1) respectively, across five surveys. NO3−-N removal and N2O-N production occurred primarily in hypoxic to anoxic conditions. Overall, these inline pipe bioreactors achieved nitrate removal efficiencies (NRE) of 14.5 ± 6.8% (8.2%–25.0%) and N2O production equivalent to 0.7 ± 0.6% (0.3–1.4%) of nitrate removal. Comparisons to the literature indicate that our bioreactors have a low NRE but a very high nitrate removal rate (NRR) on a woodchip volume basis. The bioreactor was operating at 21% water capacity. Therefore, increasing the bioreactor water height would be needed to maximize nitrate removal. Our results imply that these bioreactors can efficiently remove NO3-N without major N2O release to the atmosphere. © 2022 Elsevier B.V.
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| 14. |
- White, S. A., et al.
(författare)
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Anthropogenic nitrate attenuation versus nitrous oxide release from a woodchip bioreactor
- 2022
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491. ; 300
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen loss via overland flow from agricultural land use is a global threat to waterways. On-farm denitrifying woodchip bioreactors can mitigate NO3− exports by increasing denitrification capacity. However, denitrification in sub-optimal conditions releases the greenhouse gas nitrous oxide (N2O), swapping the pollution from aquatic to atmospheric reservoirs. Here, we assess NO3−-N removal and N2O emissions from a new edge-of-field surface-flow bioreactor during ten rain events on intensive farming land. Nitrate removal rates (NRR) varied between 5.4 and 76.2 g NO3−-N m−3 wetted woodchip d−1 with a mean of 30.3 ± 7.3 g NO3−-N m−3. The nitrate removal efficiency (NRE) was ∼73% in ideal hydrological conditions and ∼18% in non-ideal conditions. The fraction of NO3−-N converted to N2O (rN2O) in the bioreactor was ∼3.3 fold lower than the expected 0.75% IPCC emission factor. We update the global bioreactor estimated Q10 (NRR increase every 10 °C) from a recent meta-analysis with previously unavailable data to >20 °C, yielding a new global Q10 factor of 3.1. Mean N2O CO2-eq emissions (431.9 ± 125.4 g CO2-eq emissions day−1) indicate that the bioreactor was not significantly swapping aquatic NO3− for N2O pollution. Our estimated NO3−-N removal from the bioreactor (9.9 kg NO3−-N ha−1 yr−1) costs US$13.14 per kg NO3−-N removed and represents ∼30% NO3−-N removal when incorporating all flow and overflow events. Overall, edge-of-field surface-flow bioreactors seem to be a cost-effective solution to reduce NO3−-N runoff with minor pollution swapping to N2O. © 2022
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| 15. |
- Wynberg, Elke, et al.
(författare)
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Variability in white blood cell count during uncomplicated malaria and implications for parasite density estimation : a WorldWide Antimalarial Resistance Network individual patient data meta-analysis
- 2023
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Ingår i: Malaria Journal. - : Springer Nature. - 1475-2875. ; 22
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Tidskriftsartikel (refereegranskat)abstract
- Background: The World Health Organization (WHO) recommends that when peripheral malarial parasitaemia is quantified by thick film microscopy, an actual white blood cell (WBC) count from a concurrently collected blood sample is used in calculations. However, in resource-limited settings an assumed WBC count is often used instead. The aim of this study was to describe the variability in WBC count during acute uncomplicated malaria, and estimate the impact of using an assumed value of WBC on estimates of parasite density and clearance.Methods: Uncomplicated malaria drug efficacy studies that measured WBC count were selected from the WorldWide Antimalarial Resistance Network data repository for an individual patient data meta-analysis of WBC counts. Regression models with random intercepts for study-site were used to assess WBC count variability at presentation and during follow-up. Inflation factors for parasitaemia density, and clearance estimates were calculated for methods using assumed WBC counts (8000 cells/mu L and age-stratified values) using estimates derived from the measured WBC value as reference.Results: Eighty-four studies enrolling 27,656 patients with clinically uncomplicated malaria were included. Geometric mean WBC counts (x 1000 cells/mu L) in age groups < 1, 1-4, 5-14 and >= 15 years were 10.5, 8.3, 7.1, 5.7 and 7.5, 7.0, 6.5, 6.0 for individuals with falciparum (n = 24,978) and vivax (n = 2678) malaria, respectively. At presentation, higher WBC counts were seen among patients with higher parasitaemia, severe anaemia and, for individuals with vivax malaria, in regions with shorter regional relapse periodicity. Among falciparum malaria patients, using an assumed WBC count of 8000 cells/mu L resulted in parasite density underestimation by a median (IQR) of 26% (4-41%) in infants < 1 year old but an overestimation by 50% (16-91%) in adults aged = 15 years. Use of age-stratified assumed WBC values removed systematic bias but did not improve precision of parasitaemia estimation. Imprecision of parasite clearance estimates was only affected by the within-patient WBC variability over time, and remained < 10% for 79% of patients.Conclusions: Using an assumed WBC value for parasite density estimation from a thick smear may lead to underdiagnosis of hyperparasitaemia and could adversely affect clinical management; but does not result in clinically consequential inaccuracies in the estimation of the prevalence of prolonged parasite clearance and artemisinin resistance.
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