Explore the vast range of titles available.

The main aim of this work was to develop a suitable sorbent for the separation and determination of .sup.226Ra through .sup.133Ba (radio tracer) in water samples using fly ash sorbent. After the modification with KMnO.sub.4 the effects of pH, competing ions, the possibility of elution, and the effect of water volume were tested. As a suitable eluent 6 mol/L HCl was chosen, while the sorbent worked best at pH 6-8. The developed method is advantageous for minimizing the time required for separation, the volume of chemicals used, and the waste generated after separation.

The complex distribution of CO.sub.2 in the upper troposphere and lower stratosphere (UTLS) results from the interplay of different processes and mechanisms. However, in such difficult-to-access regions of the atmosphere our understanding of the CO.sub.2 variability remains limited. Using vertical trace gas profiles derived from measurements with the balloon-based AirCore technique for validation, we investigate the UTLS and stratospheric CO.sub.2 distribution simulated with the ECHAM/MESSy Atmospheric Chemistry (EMAC) global chemistry-climate model. By simulating an artificial, deseasonalised CO.sub.2 tracer, we disentangle the CO.sub.2 seasonal signal from long-term trend and transport contribution. This approach allows us to study the CO.sub.2 seasonal cycle in a unique way in remote areas and on a global scale. Our results show that the tropospheric CO.sub.2 seasonal cycle propagates upwards into the lowermost stratosphere and is most modulated in the extra-tropics between 300-100 hPa, characterised by a 50 % amplitude dampening and a 4-month phase shift in the Northern Hemisphere mid-latitudes. During this propagation the seasonal cycle shape is also tilted, which is associated with the transport barrier related to the strength of the subtropical jet. In the stratosphere, we identified both, a vertical and a horizontal \"tape recorder\" of the CO.sub.2 seasonal cycle. Originating in the tropical tropopause region this imprint is linked to the upwelling and the shallow branch of the Brewer-Dobson-circulation. As the CO.sub.2 seasonal signal carries information about transport processes on different timescales, the newly introduced tracer is a very useful diagnostic tool and would also be a suitable metric for model intercomparisons.

Based on the high-precision isotopic composition and concentration of dissolved inorganic carbon (DIC) in the Bering Sea waters, their scopes and pathways are estimated in the Pacific sector of the Arctic Ocean. Although [delta].sup.13С(DIC) and [DIC] are not classical conservative tracers, these parameters show the presence of both Atlantic and Pacific marine waters similar to the Bering Sea waters in the basin of the East Siberian Sea, which is a zone of active interaction of river and marine waters. The spatial distribution of Pacific and Atlantic and river waters is estimated using a three-component mixing model along two sections of the East Siberian Sea. The Pacific component propagates from east to west approximately to 160° E (probably, more westward) skirting Wrangel Island not only from the north but also probably from the south. The East Siberian Sea contains waters similar to the Bering Sea summer surface waters of the open sea, which are removed to the northern shelf by the circular Bering Sea Current, and to the upper intermediate waters, which can be involved in the zone of the northern sea shelf due to upwelling or active mixing.

Gross primary productivity (GPP), the CO.sub.2 uptake by means of photosynthesis, cannot be measured directly on the ecosystem scale but has to be inferred from proxies or models. One newly emerged proxy is the trace gas carbonyl sulfide (COS). COS diffuses into plant leaves in a fashion very similar to CO.sub.2 but is generally not emitted by plants. Laboratory studies on leaf level gas exchange have shown promising correlations between the leaf relative uptake (LRU) of COS to CO.sub.2 under controlled conditions. However, in situ measurements including daily to seasonal environmental changes are required to test the applicability of COS as a tracer for GPP at larger temporal scales. To this end, we conducted concurrent ecosystem-scale CO.sub.2 and COS flux measurements above an agriculturally managed temperate mountain grassland. We also determined the magnitude and variability of the soil COS exchange, which can affect the LRU on an ecosystem level. The cutting and removal of the grass at the site had a major influence on the soil flux as well as the total exchange of COS. The grassland acted as a major sink for CO.sub.2 and COS during periods of high leaf area. The sink strength decreased after the cuts, and the grassland turned into a net source for CO.sub.2 and COS on an ecosystem level. The soil acted as a small sink for COS when the canopy was undisturbed but also turned into a source after the cuts, which we linked to higher incident radiation hitting the soil surface. However, the soil contribution was not large enough to explain the COS emission on an ecosystem level, hinting at an unknown COS source possibly related to dead plant matter degradation. Over the course of the season, we observed a concurrent decrease in CO.sub.2 and COS uptake on an ecosystem level. With the exception of the short periods after the cuts, the LRU under high-light conditions was rather stable and indicated a high correlation between the COS flux and GPP across the growing season.

High-precision measurements of the triple oxygen isotope composition of CO.sub.2 (Î.sup.'17 O) can be used to estimate biosphere-atmosphere exchange of CO.sub.2, the residence time of tropospheric CO.sub.2, and stratosphere-troposphere exchange. In this study, we report measurements of the Î.sup.'17 O(CO.sub.2) from air samples collected during two aircraft-based programmes, CARIBIC and StratoClim. CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) provided air samples from numerous transcontinental flights in the upper troposphere-lower stratosphere region. StratoClim (Stratospheric and upper tropospheric processes for better climate predictions) conducted intensive campaigns with the high-altitude aircraft M55 Geophysica during the Asian summer monsoon anticyclone (ASMA), providing air samples from altitudes up to 21 km.

Transit time can be estimated thanks to natural tracers, but few of them are usable in the 0-6-month range. The main purpose of this work is to analyze the potential of the ratio of heavy- to light-weight organic compounds (the humification index (HIX); Ohno, 2002; Zsolnay et al., 1999) as a natural tracer of short transit time (Blondel et al., 2012). Critical analysis of former studies shows that although the link between HIX and transit time seems consistent, the whole methodological approach needs to be consolidated. Natural organic matter fluorescence from 289 groundwater samples from four springs and 10 flow points located in the unsaturated zone of the Vaucluse karst system is characterized by parallel factor analysis (PARAFAC) thanks to the excitation-emission matrix (EEM), thus (i) allowing for the identification of main fluorescent compounds of sampled groundwater and (ii) evidencing the inadequacy of HIX 2D emission windows to characterize groundwater organic matter. We then propose a new humification index called the Transit Time index (TTi) based on the Ohno (2002) formula but using PARAFAC components of heavy and light organic matter from our samples instead of 2D windows. Finally, we evaluate TTi relevance as a transit time tracer by (i) performing a detailed analysis of its dynamics on a selected spring (Millet) and (ii) comparing its mean value over karst springs of the Vaucluse karst system. Principal component analysis (PCA) of TTi and other hydrochemical parameters monitored at Millet spring put in relief the different ranges of transit time associated with the different organic matter compounds. PCA results also provide evidence that TTi can detect a small proportion of fast infiltration water within a mix, while other natural tracers of transit time provide no or less sensitive information. TTi distributions at monitored karst springs are consistent with relative transit times expected for the small-scale, short average transit time systems. TTi thus appears as a relevant qualitative tracer of transit time in the 0-6-month range where existing tracers fail and may remain applicable, even in the case of anthropic contamination thanks to PARAFAC modeling. Transforming it into quantitative information is a challenging task which may be possible thanks to intensive studies of organic matter degradation kinetics in natural waters with the help of radiogenic isotope usage or an artificial tracer test.

Sediment cores collected from Lake Khanka (Xingkaihu) and Amur Bay were analyzed for concentrations of .sup.137Cs and .sup.210Pb, along with the detailed mineralogical and elemental composition. The depth distribution and specific activities of .sup.137Cs in the sediment cores indicated that the investigated area is not contaminated. Maximum activity of .sup.137Cs is 10 Bq/kg, and its inventory is 0.16 Bq/m.sup.2. Despite some variation in mineralogical profiles, the sedimentation process was uniform over the investigated period. The sedimentation rate in the eastern part of Lake Khanka (Xingkaihu) was estimated to be 1.6 mm/year, and 0.43-0.5 mm/year in Amur Bay.

We present an analysis of atmospheric transport impact on estimating CO.sub.2 fluxes using two atmospheric inversion systems (CarboScope-Regional (CSR) and Lund University Modular Inversion Algorithm (LUMIA)) over Europe in 2018. The main focus of this study is to quantify the dominant drivers of spread amid CO.sub.2 estimates derived from atmospheric tracer inversions. The Lagrangian transport models STILT (Stochastic Time-Inverted Lagrangian Transport) and FLEXPART (FLEXible PARTicle) were used to assess the impact of mesoscale transport. The impact of lateral boundary conditions for CO.sub.2 was assessed by using two different estimates from the global inversion systems CarboScope (TM3) and TM5-4DVAR. CO.sub.2 estimates calculated with an ensemble of eight inversions differing in the regional and global transport models, as well as the inversion systems, show a relatively large spread for the annual fluxes, ranging between -0.72 and 0.20 PgC yr.sup.-1, which is larger than the a priori uncertainty of 0.47 PgC yr.sup.-1 . The discrepancies in annual budget are primarily caused by differences in the mesoscale transport model (0.51 PgC yr.sup.-1 ), in comparison with 0.23 and 0.10 PgC yr.sup.-1 that resulted from the far-field contributions and the inversion systems, respectively. Additionally, varying the mesoscale transport caused large discrepancies in spatial and temporal patterns, while changing the lateral boundary conditions led to more homogeneous spatial and temporal impact. We further investigated the origin of the discrepancies between transport models. The meteorological forcing parameters (forecasts versus reanalysis obtained from ECMWF data products) used to drive the transport models are responsible for a small part of the differences in CO.sub.2 estimates, but the largest impact seems to come from the transport model schemes. Although a good convergence in the differences between the inversion systems was achieved by applying a strict protocol of using identical prior fluxes and atmospheric datasets, there was a non-negligible impact arising from applying a different inversion system. Specifically, the choice of prior error structure accounted for a large part of system-to-system differences.

Anthropogenic trace gases often exhibit interhemispheric gradients because of larger emissions in the Northern Hemisphere. Depending on a tracer's emission pattern and sink processes, trace gas observations can thus be used to investigate interhemispheric transport in the atmosphere. Vice versa, understanding interhemispheric transport is important for interpreting spatial tracer distributions and for inferring emissions. We combine several data sets from the upper troposphere (UT) to investigate the interhemispheric gradient of sulfur hexafluoride (SF.sub.6) covering latitudes from â¼ 80.sup.\" N to â¼ 60.sup.\" S: canister sampling based measurements from the IAGOS-CARIBIC infrastructure and data from the in-flight gas chromatography instruments GhOST (Gas chromatograph for Observational Studies using Tracers) and UCATS (Unmanned aircraft systems Chromatograph for Atmospheric Trace Species). The interhemispheric gradient of SF.sub.6 in the UT is found to be weaker than near the surface. Using the concept of a lag time removes the increasing trend from the time series. At the most southern latitudes, a lag time of over 1 year with respect to the northern mid-latitude surface is derived, and lag times decrease over the period 2006-2020 in the extra-tropics and the southern tropics. Observations are compared to results from the two-dimensional Advanced Global Atmospheric Gases Experiment (AGAGE) 12-box model. Based on Emissions Database for Global Atmospheric Research (EDGAR 7) emissions, fair agreement of lag times is obtained for the Northern Hemisphere, but southern hemispheric air appears too \"old\". This is consistent with earlier findings that transport from the northern extra-tropics into the tropics is too slow in many models. The influence of the emission scenario and the model transport scheme are evaluated in sensitivity runs. It is found that EDGAR 7 underestimates emissions of SF.sub.6 globally and in the Southern Hemisphere, whereas northern extra-tropical emissions seem overestimated. Faster southward transport from the northern extra-tropics would be needed in the model, but transport from the southern tropics into the southern extra-tropics appears too fast.