65 research outputs found
Ecophysiology of Aspergillus Section Nigri Species Potential Ochratoxin A Producers
After aflatoxins, ochratoxin A (OTA) is the most studied mycotoxin due to the toxicological significance in human and animal diets. OTA presence has been extensively reported worldwide in the last decade in several agricultural products. The main OTA producer in tropical and temperate climates is Aspergillus carbonarius followed by species belonging to A. niger aggregate. Currently, many scientists worldwide have studied the influence of water activity and temperature for growth and biosynthesis of OTA by these species on synthetic media. This article reviews ecophysiological studies of Aspergillus section Nigri strains on synthetic media and natural substrates. The results of these investigations suggest that significant amounts of OTA can be produced in only five days and that the use of different storage practices, such as aW and temperature levels below 0.930 and 15 °C, respectively, allow controlling fungal contamination and minimizing the OTA production in several products as peanuts, corn, dried grapes and derived products for human consumption
Provenancing Archaeological Wool Textiles from Medieval Northern Europe by Light Stable Isotope Analysis (δ13C, δ15N, δ2H)
We investigate the origin of archaeological wool textiles preserved by anoxic waterlogging from seven medieval archaeological deposits in north-western Europe (c. 700-1600 AD), using geospatial patterning in carbon (δ13C), nitrogen (δ15N) and non-exchangeable hydrogen (δ2H) composition of modern and ancient sheep proteins. δ13C, δ15N and δ2H values from archaeological wool keratin (n = 83) and bone collagen (n = 59) from four sites were interpreted with reference to the composition of modern sheep wool from the same regions. The isotopic composition of wool and bone collagen samples clustered strongly by settlement; inter-regional relationships were largely parallel in modern and ancient samples, though landscape change was also significant. Degradation in archaeological wool samples, examined by elemental and amino acid composition, was greater in samples from Iceland (Reykholt) than in samples from north-east England (York, Newcastle) or northern Germany (Hessens). A nominal assignment approach was used to classify textiles into local/non-local at each site, based on maximal estimates of isotopic variability in modern sheep wool. Light element stable isotope analysis provided new insights into the origins of wool textiles, and demonstrates that isotopic provenancing of keratin preserved in anoxic waterlogged contexts is feasible. We also demonstrate the utility of δ2H analysis to understand the location of origin of archaeological protein samples
The Global Network of Isotopes in Rivers (GNIR): integration of water isotopes in watershed observation and riverine research
We introduce a new online global database of riverine water stable isotopes
(Global Network of Isotopes in Rivers, GNIR) and evaluate its longer-term data holdings. Overall, 218 GNIR river
stations were clustered into three different groups based on the seasonal
variation in their isotopic composition, which was closely coupled to
precipitation and snowmelt water runoff regimes. Sinusoidal fit functions
revealed phases within each grouping and deviations from the sinusoidal
functions revealed important river alterations or hydrological processes in
these watersheds. The seasonal isotopic amplitude of δ<sup>18</sup>O in
rivers averaged 2.5 ‰, and did not increase as a
function of latitude, like it does for global precipitation. Low seasonal
isotopic amplitudes in rivers suggest the prevalence of mixing and storage
such as occurs via lakes, reservoirs, and groundwater. The application of a
catchment-constrained regionalized cluster-based water isotope prediction
model (CC-RCWIP) allowed for direct comparison between the expected isotopic
compositions for the upstream catchment precipitation with the measured
isotopic composition of river discharge at observation stations. The
catchment-constrained model revealed a strong global isotopic correlation
between average rainfall and river discharge (<i>R</i><sup>2</sup> = 0.88) and the study
demonstrated that the seasonal isotopic composition and variation of river
water can be predicted. Deviations in data from model-predicted values
suggest there are important natural or anthropogenic catchment processes
like evaporation, damming, and water storage in the upstream catchment
Proficiency testing of 78 international laboratories measuring tritium in environmental waters by decay counting and mass spectrometry for age dating and water resources assessment
Rationale
Tritium (3H) is an important hydrological tracer that has been commonly used for over 60 years to evaluate water residence times and water dynamics in shallow/recent groundwaters, streams, lakes and the ocean. We tested the analytical performance of 78 international laboratories engaged in low‐level 3H assays for water age dating and monitoring of environmental waters.
Methods
Seven test waters were distributed by the IAEA to 78 international tritium laboratories. Set 1 included a tritium‐free groundwater plus three ultra‐low 3H samples (0.5–7 TU) for meeting groundwater dating specifications. Set 2 contained three higher 3H‐content samples (40–500 TU) suitable for testing of environmental monitoring laboratories.
Results
Seventy of the laboratories used liquid scintillation counting with or without electrolytic enrichment, seven utilized 3He accumulation and mass spectrometry, and one used gas‐proportional counting. Only ~50% of laboratories demonstrated the ability to generate accurate 3H data that was precise enough for water age dating purposes.
Conclusions
The proficiency test helped identify recurrent weaknesses and potential solutions. Strategies for performance improvements of 3H laboratories include: (a) improved quantification of 3H detection limits and analytical uncertainty, (b) stricter quality control practices in routine operations along with care and recalibration of 3H standards traceable to primary NIST standards, (c) annual assessment of tritium enrichment factors and instrumental performance, and (d) for water age dating purposes the use of electrolytic enrichment systems having the highest possible 3H enrichment factors (e.g. >50×).</p
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Spatial Radiocarbon and Stable Carbon Isotope Variability of Mineral and Thermal Waters in Slovakia
From the 20th International Radiocarbon Conference held in Kona, Hawaii, USA, May 31-June 3, 2009.Isotope hydrology investigations were carried out with the aim to study isotope variability in mineral and thermal waters (MTW) of Slovakia. The aquifers of MTW were formed by Triassic limestones and dolomites, which are found in the mountains as well as in the pre-Tertiary substratum of depressions and lowlands. The MTW were of artesian and/or open structures. At present, there are only boreholes available, as natural outflows have already been captured by them. Large spatial isotope variability (14C between 2 and 33.6 pMC, 18O between -11.8 and -9.8, and 13C between -12.7 and -3.4 for bicarbonates and -21 and -4.9 for free CO2) and heterogeneity of MTW was observed, indicating different origins of MTW. Corrected radiocarbon apparent ages of MTW indicate that they mostly infiltrated during the Würm and Holocene periods.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202
Improved high-resolution global and regionalized isoscapes of δ¹⁸O, δ²H and d-excess in precipitation
Abstract
Patterns of δ¹⁸O and δ²H in Earth’s precipitation provide essential scientific data for use in hydrological, climatological, ecological and forensic research. Insufficient global spatial data coverage promulgated the use of gridded datasets employing geostatistical techniques (isoscapes) for spatiotemporally coherent isotope predictions. Cluster-based isoscape regionalization combines the advantages of local or regional prediction calibrations into a global framework. Here we present a revision of a Regionalized Cluster-Based Water Isotope Prediction model (RCWIP2) incorporating new isotope data having extensive spatial coverage and a wider array of predictor variables combined with high-resolution gridded climatic data. We introduced coupling of δ¹⁸O and δ²H (e.g., d-excess constrained) in the model predictions to prevent runaway isoscapes when each isotope is modelled separately and cross-checked observed versus modelled d-excess values. We improved model error quantification by adopting full uncertainty propagation in all calculations. RCWIP2 improved the RMSE over previous isoscape models by ca. 0.3 ‰ for δ¹⁸O and 2.5 ‰ for δ²H with an uncertainty <1.0 ‰ for δ¹⁸O and < 8 ‰ for δ²H for most regions of the world. The determination of the relative importance of each predictor variable in each ecoclimatic zone is a new approach to identify previously unrecognized climatic drivers on mean annual precipitation δ¹⁸O and δ²H. The improved RCWIP2 isoscape grids and maps (season, monthly, annual, regional) are available for download at https://isotopehydrologynetwork.iaea.org
Key drivers controlling stable isotope variations in daily precipitation of Costa Rica: Caribbean Sea versus Eastern Pacific Ocean moisture
2013-2017: International Atomic Energy Agency, Vienna, Austria, Project CRP 17947: Stable isotopes in precipitation and paleoclimatic archives in tropical areas to improve regional hydrological and climatic impact modelsCosta Rica is located on the Central American Isthmus, which receives moisture inputs directly from the Caribbean Sea and the Eastern Pacific Ocean. This location includes unique mountainous and lowland microclimates, but only limited knowledge exists about the impact of relief and regional atmospheric circulation patterns on precipitation origin, transport, and isotopic composition. Therefore, the main scope of this project is to identify the key drivers controlling stable isotope variations in daily-scale precipitation of Costa Rica. The monitoring sites comprise three strategic locations across Costa Rica: Heredia (Central Valley), Turrialba (Caribbean slope), and Caño Seco (South Pacific slope). Sporadic dry season rain is mostly related to isolated enriched events ranging from −5.8‰ to −0.9‰ δ18O. By mid-May, the Intertropical Convergence Zone reaches Costa Rica resulting in a notable depletion in isotope ratios (up to −18.5‰ δ18O). HYSPLIT air mass back trajectories indicate the strong influence on the origin and transport of precipitation of three main moisture transport mechanisms, the Caribbean Low Level Jet, the Colombian Low Level Jet, and localized convection events. Multiple linear regression models constructed based on Random Forests of surface meteorological information and atmospheric sounding profiles suggest that lifted condensation level and surface relative humidity are the main factors controlling isotopic variations. These findings diverge from the recognized ‘amount effect’ in monthly composite samples across the tropics. Understanding of stable isotope dynamics in tropical precipitation can be used to a) enhance groundwater modeling efforts in ungauged basins where scarcity of long-term monitoring data drastically limit current and future water resources management, b) improve the re-construction of paleoclimatic records in the Central American land bridge, c) calibrate and validate regional circulation models.Costa Rica está ubicada en el Istmo Centroamericano, que recibe aportes de humedad directamente del Mar Caribe y del Océano Pacífico Oriental. Esta ubicación incluye microclimas montañosos y de tierras bajas únicas, pero solo existe un conocimiento limitado sobre el impacto del relieve y los patrones de circulación atmosférica regional sobre el origen, el transporte y la composición isotópica de las precipitaciones. Por lo tanto, el alcance principal de este proyecto es identificar los impulsores clave que controlan las variaciones de isótopos estables en la precipitación a escala diaria de Costa Rica. Los sitios de monitoreo comprenden tres ubicaciones estratégicas en Costa Rica: Heredia (Valle Central), Turrialba (vertiente del Caribe) y Caño Seco (vertiente del Pacífico Sur). La lluvia esporádica de la estación seca se relaciona principalmente con eventos enriquecidos aislados que van desde −5,8 ‰ a −0,9 ‰ δ18O. A mediados de mayo, la Zona de Convergencia Intertropical llega a Costa Rica, lo que resulta en un notable agotamiento de las proporciones de isótopos (hasta −18,5 ‰ δ18O). Las trayectorias de retroceso de la masa de aire de HYSPLIT indican la fuerte influencia en el origen y transporte de la precipitación de tres mecanismos principales de transporte de humedad, el chorro de bajo nivel del Caribe, el chorro de bajo nivel de Colombia y los eventos de convección localizados. Múltiples modelos de regresión lineal construidos a partir de bosques aleatorios de información meteorológica de superficie y perfiles de sondeo atmosférico sugieren que el nivel de condensación elevado y la humedad relativa de la superficie son los principales factores que controlan las variaciones isotópicas. Estos hallazgos difieren del "efecto de cantidad" reconocido en muestras compuestas mensuales en los trópicos. La comprensión de la dinámica de isótopos estables en la precipitación tropical se puede utilizar para a) mejorar los esfuerzos de modelado de aguas subterráneas en cuencas no calibradas donde la escasez de datos de monitoreo a largo plazo limita drásticamente la gestión actual y futura de los recursos hídricos, Puente terrestre centroamericano, c) calibrar y validar modelos de circulación regional.Escuela de Químic
Evaluation of seawater intrusion on the groundwater data obtained from the monitoring network in Korea
Geochemistry of rainfall at Stromboli volcano (Aeolian Islands): isotopic model and plume-rain interaction
The chemical and isotopic compositions of the precipitation at Stromboli Island, Italy, were
investigated between October 2003 and October 2005. We employed a rain gauge network designed to
cover the range in exposures and elevations of the volcanic edifice. The hydrogen and oxygen isotopic
ratios vary greatly on a seasonal basis and correlate with air temperature. Deuterium excess values show a
positive correlation with altitude. No direct contribution of volcanogenic H or O is evident in the isotopic
composition of the rainwater. The chemical composition of the rainwater is principally controlled by the
sea aerosol contribution at the coastal sites, whereas it is significantly influenced by volcanic activity near
the summit vents. Interaction with volcanic acid gases is indicated by the pH, which is usually 1–2 units
lower near the craters than at the coastal sites. The S/Cl, Cl/F, and S/F molar ratios in rainwater 1.5 km
from the craters are consistent with those measured in the volcanic plume using other methods (diffusive
tubes and Fourier transform infrared spectroscopy). Rising of undegassed magmas changes these molar
ratios because of the differential degassing of sulphur, chlorine, and fluorine from the magma. We therefore
propose that the chemical composition of precipitation, within 1.5 km of the craters, provides additional
information that is useful for monitoring volcanic activity at Stromboli Island. Moreover, this paper
presents estimates of the fluxes of F, Cl, S, Na, K, Ca, and Mg to the soil that could be useful for
geochemical studies on groundwater
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