Papers by Frank McDermott
Science of the Total Environment, 2020
Untreated sludge from small-scale on-site domestic wastewater treatment systems (septic tanks) wa... more Untreated sludge from small-scale on-site domestic wastewater treatment systems (septic tanks) was spiked with 20, 60 and 100 nm silver nanoparticles (Ag-NPs) to investigate Ag-NP behaviour in these systems that are widely distributed in rural areas. In addition, the release of Ag-NPs from a previously spiked clay-rich loam reference soil (LUFA 2.4) was evaluated, in the presence and absence of untreated sludge, to simulate the common practice of sludge disposal by spreading on agricultural land. Single particle ICP-MS was used to determine
Ag-NP size distribution and the resultswere compared with total Ag (Ag-NP and ionic) measured in acid digested samples. As documented previously for large municipal scale wastewater treatment plants, Ag-NPs are found to be overwhelmingly (~98%) retained in the sludge in these small-scale systems. The Ag-NP retention efficiency on
the LUFA reference soil amended with sludge is approximately 10 times greater than that of LUFA soil alone (in the absence of sludge). For soil spiked with 60 nm Ag-NPs, the calculated average diameter of Ag-NPs in the supernatant, after 24 h was 45±3 nm (dissolution rate 7.2E−06 mol/m2·h for 60 nmAg-NP), smaller than that of supernatant from the combined sludge/soil system (52±2 nm), indicating lower Ag-NP dissolution rates in the sludge-amended soil. This study provides new information about the leachability of Ag-NPs from septic tank sludge and suggests that the effluent and sludge from septic tanks are potential sources of both nano- and dissolved ionic-Ag to environmental waters.
Meteorological Applications, 2020
Increased use of solar photovoltaic electricity requires a better understanding of the impact of ... more Increased use of solar photovoltaic electricity requires a better understanding of the impact of large-scale atmospheric teleconnections on incident short wave (SW) solar radiation. Our focus is on the relationship between winter (December to February) SW radiation in northwest Europe and the dominant Euro-Atlantic atmospheric teleconnection patterns using multiple multi-decadal observational and gridded reanalysis datasets, with a focus on the islands of Ireland and Britain. Our study reveals that the previously reported west-east seesaw in the correlation pattern between the winter North Atlantic Oscillation (NAO) index and winter SW radiation across the United Kingdom is complex, involving several zonal changes in the sign of the NAO-SW correlations (multiple seesaws). By comparison with the NAO, the east Atlantic pattern exerts only a weak control on winter SW radiation across the United Kingdom and Ireland, although in the western part of the Iberian Peninsula and adjacent Atlantic Ocean significant positive correlations occur. High values of the Scandinavian pattern index result in higher than average winter SW radiation in much of northern Europe, although it is evident that some regions (e.g. northeast England, east Scotland and the adjacent North Sea area) exhibit the opposite behaviour. Inter-seasonal variations in the dominant atmospheric flow and moisture transport directions, steered by large-scale atmospheric pressure patterns, combined with orographic uplift and rainout effects on the windward side of hills and mountains are interpreted to be the physical drivers of the observed zonal variations and correlation sign reversals between winter SW anomalies and the NAO index. K E Y W O R D S east Atlantic (EA)
Nature Communications, 2020
Atmospheric circulation is a fundamental component of Earth's climate system, transporting energy... more Atmospheric circulation is a fundamental component of Earth's climate system, transporting energy poleward to partially offset the latitudinal imbalance in insolation. Changes in the latitudinal distribution of insolation thus force variations in atmospheric circulation, in turn altering regional hydroclimates. Here we demonstrate that regional hydroclimates controlled by the Northern Hemisphere mid-latitude storm tracks and the African and South American Monsoons changed synchronously during the last 10 kyrs. We argue that these regional hydroclimate variations are connected and reflect the adjustment of the atmospheric pole-ward energy transport to the evolving differential heating of the Northern and Southern Hemispheres. These results indicate that changes in latitudinal insolation gradients and associated variations in latitudinal temperature gradients exert important control on atmospheric circulation and regional hydroclimates. Since the current episode of global warming strongly affects latitudinal temperature gradients through Arctic amplification, our results can inform projections of likely inter-hemispheric precipitation changes in the future.
Metagenomic analysis is a highly promising technique in paleogenetic research that allows analysi... more Metagenomic analysis is a highly promising technique in paleogenetic research that allows analysis of the complete genomic make-up of a sample. this technique has successfully been employed to archaeological sediments, but possible leaching of DNA through the sequence limits interpretation. We applied this technique to the analysis of ancient DNA (aDNA) from Late Quaternary stalagmites from two caves in Western Georgia, Melouri Cave and solkota. stalagmites form closed systems, limiting the effect of leaching, and can be securely dated with U-series. The analyses of the sequence data from the Melouri Cave stalagmite revealed potential contamination and low preservation of DNA. However, the two solkota stalagmites preserved ancient DNA molecules of mammals (bear, roe deer, bats) and plants (chestnut, hazelnut, flax). The aDNA bearing layers from one of the two Solkota stalagmites were dated to between ~84 ka and ~56 ka BP by U-series. The second Solkota stalagmite contained excessive detrital clay obstructing U-series dating, but it also contained bear bones with a minimum age of ~50 BP uncalibrated years and ancient DNA molecules. the preservation of authentic ancient DNA molecules in Late Quaternary speleothems opens up a new paleogenetic archive for archaeological, paleontological and paleoenvironmental research. Ancient DNA (aDNA) genomics is a valuable information source on past biological diversity and evolutionary trajectories of species 1-3. A particular focus has been on the analysis of human bones yielding high coverage genomes of archaic humans 4-6 and enabling novel insights into human dispersals and migrations 7-9. Additionally, several studies employed a metagenomic approach to the study of DNA sequence data retrieved from soils and sediments from various environments, including caves 10 , lakes 11 , arid 12 and arctic environments 13,14. Slon et al. 15 using a shotgun sequencing approach and analysing the deamination pattern for identification of authentic ancient DNA 16 , reported on the recovery of archaic human aDNA as well as other mammalian aDNA from archaeological deposits at several sites. This metagenomic research shows that not only bones but many other components of the archaeological and paleontological record, such as deposits themselves, may serve as a preservation medium for ancient DNA. The retrieval of authentic aDNA strands from deposits is made possible by the binding of DNA to various sediment and soil components, including clays 17-19 , silica 20,21 , humic acids 22 and calcite 23. However, soil chemistry , e.g. pH 20 , and soil transformation processes, such as the dissolution and precipitation of minerals, greatly impacts preservation. Furthermore, post-depositional movement of sediment components through turbation, such as bioturbation, as well as other soil translocation processes, such as clay illuviation, may negatively impact the integrity and complicate the interpretation of aDNA found in sediments and soils 24,25 .
Impacts of the EA and SCA patterns on the European twentieth century NAO-winter climate relationship
Quarterly Journal of the Royal Meteorological Society, 2014
Much of the twentieth century multidecadal variability in the relationship between North Atlantic... more Much of the twentieth century multidecadal variability in the relationship between North Atlantic Oscillation (NAO) and winter climate over the North Atlantic–European sector can be linked to the combined effects of the NAO and either the East Atlantic pattern (EA) or the Scandinavian pattern (SCA). Our study documents how different NAO–EA and NAO–SCA combinations influence winter climatic conditions (temperature and precipitation) as a consequence of NAO dipole migrations. Using teleconnectivity maps, we find that the zero-correlated line of the NAO–winter-climate relationship migrates southwards when the EA is in the opposite phase to the NAO, related to a southwestwards migration of the NAO dipole under these conditions. Similarly, a clockwise movement of the NAO–winter-climate correlated areas occurs when the phase of the SCA is opposite to that of the NAO, reflecting a clockwise movement of the NAO dipole under these conditions. Our study provides new insights into the causes of spatial and temporal nonstationarity in the climate–NAO relationships, particularly with respect to winter precipitation. Furthermore, interannual variability in the north–south winter precipitation gradient in the UK appears to reflect the migration of the NAO dipole linked to linear combinations of the NAO and the EA. The study also has important implications for studies of the role of the NAO in modulating the wind energy resource of the UK and Ireland, as well as for the selection of locations for terrestrial proxy archive reconstruction of past states of the NAO.
Ooids are sedimentary grains that are distributed widely in the geologic record. Their formation ... more Ooids are sedimentary grains that are distributed widely in the geologic record. Their formation is still actively debated, which limits our understanding of the significance and meaning of these grains in Earth's history. Central questions include the role played by microbes in the formation of ooids and the sources of ubiquitous organic matter within ooid cortices. To address these issues, we investigated the microbial community composition and associated lipids in modern oolitic sands at Pigeon Cay on Cat Island, The Bahamas. Surface samples were taken along a transect from the shallow, turbulent surf zone to calmer, deeper water. Grains transitioned from shiny and abraded ooids in the surf zone, to biofilm-coated ooids at about 3 m water depth. Further offshore, grapestones (cemented aggregates of ooids) dominated. Benthic diatoms and Proteobacteria dominated biofilms. Taxa that may promote carbonate precipitation were abundant, particularly those associated with sulfur cycling. Compared to the lipids associated with surface biofilms, relict lipids bound within carbonate exhibited remarkably similar profiles in all grain types. The enhanced abundance of methyl-branched fatty acids and β-hydroxy fatty acids, 1-O-monoalkyl glycerol ethers and hopanoids bound within ooid and grapestone carbonate confirms a clear association of benthic sedimentary bacteria with these grains. Lipids bound within ooid cortices also contain molecular indicators of microbial heterotrophic degradation of organic matter, possibly in locally reducing conditions. These included the loss of labile unsaturated fatty acids, enhanced long-chain fatty acids/short-chain fatty acids, enriched stable carbon isotopes ratios of fatty acids, and very high stanol/stenol ratios. To what extent some of these molecular signals are derived from later heterotrophic endolithic activity remains to be fully resolved. We speculate that some ooid carbonate forms in microbial biofilms and that early diagenetic degradation of biofilms may also play a role in early stage carbonate precipitation around ooids.
Annual to sub-annual resolution of multiple trace-element trends in speleothems
Journal of the Geological Society, 2001
This study aims to establish evidence for the widespread existence of preserved high-resolution t... more This study aims to establish evidence for the widespread existence of preserved high-resolution trace element variations in speleothems that may have climatic significance. Ion microprobe analysis of speleothems reveals that annual to sub-annual variations in ...
We examine mid-to late Holocene centennial-scale climate variability in Ireland using proxy data ... more We examine mid-to late Holocene centennial-scale climate variability in Ireland using proxy data from peatlands, lakes and a speleothem. A high degree of between-record variability is apparent in the proxy data and significant chronological uncertainties are present. However, tephra layers provide a robust tool for correlation and improve the chronological precision of the records. Although we can find no statistically significant coherence in the dataset as a whole, a selection of high-quality peatland water table reconstructions co-vary more than would be expected by chance alone. A locally weighted regression model with bootstrapping can be used to construct a 'best-estimate' palaeoclimatic reconstruction from these datasets. Visual comparison and cross-wavelet analysis of peatland water table compilations from Ireland and Northern Britain show that there are some periods of coherence between these records. Some terrestrial palaeoclimatic changes in Ireland appear to coincide with changes in the North Atlantic thermohaline circulation and solar activity. However, these relationships are inconsistent and may be obscured by chronological uncertainties. We conclude by suggesting an agenda for future Holocene climate research in Ireland.
Elemental U and Th variations in island arc rocks: implications for U-series isotopes
Chemical Geology, 1997
Isotope and trace element data from well characterised arc suites are used to identify contributi... more Isotope and trace element data from well characterised arc suites are used to identify contributions from fluids and subducted sediments in arc rocks. U-series isotopes are then used to argue that the fluid and sediment components are characterised by different transfer times through ...
Characterization of bacterial community structure on a weathered pegmatitic granite
Microbial ecology, 2006
This study exploited the contrasting major element chemistry of a pegmatitic granite to investiga... more This study exploited the contrasting major element chemistry of a pegmatitic granite to investigate mineralogical influences on bacterial community structure. Intact crystals of variably weathered muscovite, plagioclase, K-feldspar, and quartz were extracted, together with whole-rock granite. Environmental scanning electron microscopy revealed a diversity of bacterial structures, with rods and cocci clearly visible on surfaces of all mineral types. Bacterial automated ribosomal intergenic spacer analysis was used to generate a ribotype profile for each mineral. A randomization test revealed that community fingerprints differed between different mineral types, whereas canonical correspondence analysis (CCA) showed that mineral chemistry affected individual bacterial ribotypes. CCA also revealed that Al, Si, and Ca had a significant impact on bacterial community structure within the system, which contrasts with the finding within fungal communities that although Al and Si also had a s...
Precisely-dated, high-resolution stable isotope and trace element data from a stalagmite from La ... more Precisely-dated, high-resolution stable isotope and trace element data from a stalagmite from La Garma
Cave, northern Spain, reveal several stages of distinct climatic variability along the northern Iberian
Atlantic margin, and provide new constraints on the latitude of North Atlantic westerlies during the
Younger Dryas Event (YD). Westerly wind position (reconstructed using sub-annually resolved Mg data
as a proxy for sea spray contributions associated with wind strength at this coastal cave site) during
the early YD (12.85–12.15 kyr) oscillated meridionally, resembling the decadal-scale component of the
modern North Atlantic Oscillation (NAO). Northward repositioning of westerly storm tracks over northern
Iberia began at ∼12.15 kyr, consistent with other high-resolution wind proxy reconstructions from central
and northern Europe, but occurred more gradually nearer the Atlantic margin. From ∼12.15 kyr to the
YD termination, atmospheric circulation resembled a persistently positive NAO, with westerlies reaching
their maximum northward extent at 11.8 kyr (reflected by a Mg concentration minimum at this time).
Air temperature (reflected by our δ18O data) and Iberian wind strength were predominantly coupled
throughout the YD suggesting that temperature modulated sea-ice extent, and consequently controlled
westerly wind latitude. However our data suggest that abrupt warming at 12.1 kyr was followed by much
more gradual northward shifts in westerly position, and that a lag existed between the warming and
sea-ice retreat. This gradual return of the westerlies to the north beginning at 12.1 kyr is consistent with
inferred changes in wind strength at other European sites. Additionally, atmospheric circulation inferred
from our northern Iberian wind strength proxy record generally tracked low-frequency meridional shifts
in Intertropical Convergence Zone position, corroborating past research that suggested closely coupled
low- and high-latitude atmospheric teleconnections over this period.
Frontiers of Speleothem Research
Stabilisation and Evolution of the Continental Lithosphere
Mass-sepctrometric measurements of 230 Th/232 Th in 45 Ka volcanic rocks
Mantle and slab derived fluxes at destructive plate margins
U-series isotopes in arc magma
Rapid Isotope Profiling of Speleothem by He Flow-through Laser Ablation: Insight Into Abrupt Climate Fluctuations From A new Exceptionally High Resolution Holocene\ delta18O Record From SW Ireland
ABSTRACT Stable isotope analysis of carbonates at high spatial resolution is normally achieved ei... more ABSTRACT Stable isotope analysis of carbonates at high spatial resolution is normally achieved either by microdrilling or by laser sampling, although the latter has not been widely employed, despite early promise, due to higher analytical errors particularly for oxygen isotopes. Laser ablation using a sample chamber continuously swept by He can be shown to significantly improve the accuracy and precision of carbon and oxygen isotope data, with the advantage of the rapid analysis times inherent with He flow-through technology. An automated He flow through laser-ablation system has been used to obtain continuous high resolution isotope profiles along growth axes of speleothem at a resolution of 250 microns or better. The system uses a 25W CO2 laser heat source with a continuous helium flow sample chamber on line to a conventional gas chromatograph-isotope ratio monitoring system (Micromass Optima - Isochrome). In-situ analysis of Carrara Marble yield \delta13C and \delta18O values reproducible to better than +/-0.1\permil. A new high resolution isotope record comprising 1640 analyses has been obtained on a well dated 465 mm Holocene Stalagmite (CC3). For the latter part of the Holocene each analysis represents 10-22 years, but for the period prior to 5,300 years where speleothem growth rates were higher, resolution is sub-decadal. The new data accurately reproduce the first-order variation obtained by drill-sampling with \delta18O varying from -11.65 to -0.82\permil, but with most data varying by +/-1.75% around a mean value of -3.26\permil. Historically cooler periods are associated with lower \delta18O but the new profile also reveals short lived high amplitude (>3\permil) isotope shifts. One of these events exhibits an extremely large shift of c.8\permil over 1mm of calcite dated to between 8445 and 8400 calendar years BP. This high amplitude event is superimposed on a 350 year old episode of lowered \delta18O that commenced at 8470 years BP but is too large to attribute solely to cooling and may reflect change in the isotopic composition of N. Atlantic surface waters consistent with catastrophic release of Laurentide ice sheet melt waters.
Passive and Reactive Transport through Faults using a lattice Boltzmann Approach
ABSTRACT
Solar forcing of Holocene climate; where are the amplifiers?
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Papers by Frank McDermott
Ag-NP size distribution and the resultswere compared with total Ag (Ag-NP and ionic) measured in acid digested samples. As documented previously for large municipal scale wastewater treatment plants, Ag-NPs are found to be overwhelmingly (~98%) retained in the sludge in these small-scale systems. The Ag-NP retention efficiency on
the LUFA reference soil amended with sludge is approximately 10 times greater than that of LUFA soil alone (in the absence of sludge). For soil spiked with 60 nm Ag-NPs, the calculated average diameter of Ag-NPs in the supernatant, after 24 h was 45±3 nm (dissolution rate 7.2E−06 mol/m2·h for 60 nmAg-NP), smaller than that of supernatant from the combined sludge/soil system (52±2 nm), indicating lower Ag-NP dissolution rates in the sludge-amended soil. This study provides new information about the leachability of Ag-NPs from septic tank sludge and suggests that the effluent and sludge from septic tanks are potential sources of both nano- and dissolved ionic-Ag to environmental waters.
Cave, northern Spain, reveal several stages of distinct climatic variability along the northern Iberian
Atlantic margin, and provide new constraints on the latitude of North Atlantic westerlies during the
Younger Dryas Event (YD). Westerly wind position (reconstructed using sub-annually resolved Mg data
as a proxy for sea spray contributions associated with wind strength at this coastal cave site) during
the early YD (12.85–12.15 kyr) oscillated meridionally, resembling the decadal-scale component of the
modern North Atlantic Oscillation (NAO). Northward repositioning of westerly storm tracks over northern
Iberia began at ∼12.15 kyr, consistent with other high-resolution wind proxy reconstructions from central
and northern Europe, but occurred more gradually nearer the Atlantic margin. From ∼12.15 kyr to the
YD termination, atmospheric circulation resembled a persistently positive NAO, with westerlies reaching
their maximum northward extent at 11.8 kyr (reflected by a Mg concentration minimum at this time).
Air temperature (reflected by our δ18O data) and Iberian wind strength were predominantly coupled
throughout the YD suggesting that temperature modulated sea-ice extent, and consequently controlled
westerly wind latitude. However our data suggest that abrupt warming at 12.1 kyr was followed by much
more gradual northward shifts in westerly position, and that a lag existed between the warming and
sea-ice retreat. This gradual return of the westerlies to the north beginning at 12.1 kyr is consistent with
inferred changes in wind strength at other European sites. Additionally, atmospheric circulation inferred
from our northern Iberian wind strength proxy record generally tracked low-frequency meridional shifts
in Intertropical Convergence Zone position, corroborating past research that suggested closely coupled
low- and high-latitude atmospheric teleconnections over this period.