Mean δD Research Articles

The Chemical Properties and Formation Mechanisms of Shallow Groundwater in the Guohe River Basin, China

An investigation of the distribution and control factors of groundwater is significant for the rational exploitation and utilization of groundwater resources. This study analyzes the hydrogeochemical processes and control factors of shallow groundwater in the Guohe River Basin. A hydrogeological survey was conducted, and hydrochemical and hydrogen–oxygen isotopic data of 125 samples of surface water and groundwater were analyzed. The results showed that the total dissolved solid (TDS) content in shallow groundwater was 138–2967 mg/L, with an average of 831 mg/L. A decline in the TDS was observed from the upper to the lower reaches. The contents of the anions and cations in the shallow groundwater were in the order HCO3− > Cl− > SO42− and Na+ and K+ > Mg2+ > Ca2+, respectively. The cation exchange increased the aqueous concentrations of Na+ and K+, and the TDS content was highly correlated with the contents of Na+, Cl−, and SO42− ions. The δD and δ18O values in shallow groundwater increased from the upper to the lower reaches, with the mean δD values being −59.72‰, −53.58‰, and −47.17‰ and the mean δ18O values being −8.33‰, −7.37‰, and −6.43‰. The contribution rates of the recharge source, evaporation, and water–rock interaction to the groundwater TDS concentration were 20.4%, 29.5%, and 50.1%, respectively. The water–rock interaction dominated the formation of shallow groundwater in the Guohe River Basin. The dissolution of salt rock and gypsum contributed to ion formation in shallow groundwater. The research findings can be used to improve the groundwater quality in the Guohe River Basin.

Simulation Experiment Study on Impacting the δD Value of Aromatic Compounds

Little is known about the effects of sedimentary environment and maturity on δD values of aromatic compounds deposited in geological bodies. Our simulation experiments showed that the δD value of pyrolytic polycyclic aromatic hydrocarbons (PAHs) was significantly different between the studied samples from high and low latitude regions. Comparative studies showed that the δD values of PAHs produced by pyrolysis were related to those of water in the two regions. With increasing maturity, the δD value of the PAHs becomes higher. Additionally, it was observed that some PAHs exhibited a propensity to increase the δD value upon demethylation. The thermodynamic fractionation of hydrogen isotopes between the PAHs produced by pyrolysis and both the n-alkanes and methane produced by pyrolysis indicated that the hydrogen isotopic value of the PAHs was higher than that of the n-alkanes or methane. The long-chain alkylbenzene produced by pyrolysis has a higher mean δD value compared with the n-alkanes produced by pyrolysis, but it is lower than that of the PAHs in the same sample. The lowest δD value among the aromatics was found in the ring A monoaromatic steroids produced by pyrolysis. The low δD values of these steroids should originate from isotopic fractionation during isoprenoid lipid biosynthesis.

Brain motion networks predict head motion during rest- and task-fMRI.

The capacity to stay still during scanning, which is necessary to avoid motion confounds while imaging, varies markedly between people. Here we investigated the effect of head motion on functional connectivity using connectome-based predictive modeling (CPM) and publicly available brain functional magnetic resonance imaging (fMRI) data from 414 individuals with low frame-to-frame motion (Δd < 0.18 mm). Leave-one-out was used for internal cross-validation of head motion prediction in 207 participants, and twofold cross-validation was used in an independent sample (n = 207). Parametric testing, as well as CPM-based permutations for null hypothesis testing, revealed strong linear associations between observed and predicted values of head motion. Motion prediction accuracy was higher for task- than for rest-fMRI, and for absolute head motion (d) than for Δd. Denoising attenuated the predictability of head motion, but stricter framewise displacement threshold (FD = 0.2 mm) for motion censoring did not alter the accuracy of the predictions obtained with lenient censoring (FD = 0.5 mm). For rest-fMRI, prediction accuracy was lower for individuals with low motion (mean Δd < 0.02 mm; n = 200) than for those with moderate motion (Δd < 0.04 mm; n = 414). The cerebellum and default-mode network (DMN) regions that forecasted individual differences in d and Δd during six different tasks- and two rest-fMRI sessions were consistently prone to the deleterious effect of head motion. However, these findings generalized to a novel group of 1,422 individuals but not to simulated datasets without neurobiological contributions, suggesting that cerebellar and DMN connectivity could partially reflect functional signals pertaining to inhibitory motor control during fMRI.

In-vivo Comparison of Planned and Measured Rectal Doses during Cobalt-60 HDR CT-based Intracavitary Brachytherapy Applications of Cervical Cancer Using the PTW 9112 Semiconductor Probe.

A semiconductor rectal probe was used to compare planned and measured rectal doses during Co-60 high dose rate (HDR) CT-based intracavitary brachytherapy applications (ICBT) of cervical cancer. A total of 22 HDR brachytherapy applications were included from 11 patients who were first treated with EBRT to the whole pelvis with a total prescribed dose of 50 Gy in 25 fractions. During each application, a PTW 9112 probe rectal probe having a series of five semiconductor diodes (R1 to R5) was inserted into the patient's rectum and a CT-based HDR ICBT application with a prescribed dose per fraction of 7 or 7.5 Gy to HRCTV was performed. Measurements were carried in water phantom using PTW rectal and universal adaptor plugs. Doses measured in phantom and with patients were compared to those calculated by the treatment planning system. The mean percentage dose difference ΔD (%) between calculated and measured values from phantom study were -5.29%, 1.89%, -2.72%, -4.76, and 0.72% for R1, R2, R3, R4, and R3 diodes, respectively and the overall mean ΔD (%) value with standard deviation (SD) was -2.03%±9.6%. From the patient study, a ΔD (%) that ranged from -19.5% to 24.0%, which corresponded to dose disparities between -0.77 Gy and 0.66 Gy. The median ΔD (%) ranged from 0.4% to 1.3%, or -0.03 to 0.05 Gy, respectively. ΔD (%) values exceeded 10% in approximately 26.4% of measurements (29 out of 110 in 22 applications). The location of Rmax in computed and measured values differs in 5 of 22 applications might be due to possible displacement of rectal probe between simulation and treatment. Despite the likely geometrical shift of measuring detectors between insertion and treatment, in-vivo dosimetry is feasible and can be used to estimate the dose to the rectum during HDR ICBT.

INTERPRETATION OF ISOTOPIC DATA FOR GROUNDWATERS IN THE OLĂNEŞTI AREA. COMPARISONS WITH OTHER CARPATHIAN ZONES

The research activities consisted in the inventory of stable hydrogen isotopic and geochemical data for mineral and geothermal waters belonging to the Olănești resort in order to define their origin, genetic relationships and underground dynamics in the geological context of the Getic Depression. Comparative study with other Carpathian zones (i. e. East Carpathians, Apuseni Mountains, Pannonian Basin, Transylvanian Basin, Getic Depression, and External Flysch) has also been performed. Previous hydrogeological, hydrochemical and isotopic studies identified three components for the groundwaters in the Olănești area: deep formation waters, local infiltration waters (especially from the Olăneşti Valley), and waters from high altitudes. Formation waters from Olănești and from other resorts in the Getic Depression (Călimenești – Căciulata and Govora) display mean δD and TDS values similar to those of formation waters in the Balvanyos - Covasna area (East Carpathians), and also to the salt waters in the Transylvanian Basin. The major contribution of formation water to the genesis of mineral waters in the Getic Depression makes them extremely vulnerable to degradation over time because formation water is a „fossil” not renewable component.

Novel Simulation for Dosimetry Impact of Diaphragm Respiratory Motion in 4D VMAT for Esophageal Cancer

<h3>Purpose/Objective(s)</h3> Respiratory motion affects the robustness of the dose distribution. For esophageal cancer (EC) near the esophagogastric junction, respiratory motion causes unintentional over- or under- dose distributions for the target. Although four-dimensional computed tomography (4DCT) is useful for robust evaluation, it increases the exposure dose and acquisition time. The objective of the current study is to propose the framework of the virtual 4DCT based robust evaluation method. Moreover, the robust evaluation with the virtual 4DCT was applied to EC patients. <h3>Materials/Methods</h3> We retrospectively evaluated 10 superficial (T1a - T1b) EC patients, had real 4DCT scans (real-4DCT). Target delineation was as follows; GTV: the primary lesion, CTV: GTV + 10mm (horizontal direction (H)), and 30mm (cranial and caudal direction (CC)). PTV: CTV + 8mm (H), and 15mm (CC). Volumetric modulated arc therapy (VMAT) was planned using double arcs which rotated 360° including two 60° lateral avoidance sectors during delivery. The virtual 4DCT defined as simulated 4DCT images (sim-4DCT) was generated with the simulated-organ motion function in commercial treatment planning system. Each sim-4DCT of 10 phases was generated from the end-inhalation CT image (reference image) by moving the diaphragm with mathematical equation proposed by Lujan et al (Med Phys 2003). First, we validated the accumulated CTV dose (D_99%, D_mean and D_1%) of 4D dose distribution in the sim-4DCT by comparing with the real-4DCT. The diaphragm motions (max, min and 60-90% tile of value) in the real 4DCT were obtained from an in-house program and adapted to sim-4DCTs. Then, the robustness of the CTV (D_99%, D_mean and D_1%) was evaluated by moving diaphragm from 5 to 20 mm. The percentage dose difference (ΔDx) between sim 4D-CT and static 3D-CT images which were used for planning was investigated. <h3>Results</h3> The accumulated CTV dose difference between sim-4DCT and real-4DCT was within 1% at 70% tile of the diaphragm motion. The mean CTV value of ΔD_99%, ΔD_mean and ΔD_1%, increased from 0.2% to 2.3%, 0.1% to 0.7 % and 0.1% to 0.6%, respectively, along with an increase in the diaphragm amplitude. For the diaphragm amplitude up to 15 mm, the mean ΔD_99%, ΔD_mean and ΔD_1% of CTV were within 3%. The largest percentage change was ΔD_99%, which was 2.2%. For the diaphragm amplitude of 20 mm, ΔD_99% for one patient was over 5%. The ΔD_99% of CTV for the other patients was within 3.9%. <h3>Conclusion</h3> This study proposed a novel method to evaluate the robust by generating virtual 4DCT. For EC case near the esophagogastric junction, the robust was enough if the diaphragm motion was within the PTV margin. The treatment planning with virtual 4DCT based robust evaluation method could propose an appropriate margin for PTV.

Feasibility of artificial-intelligence-based synthetic computed tomography in a magnetic resonance-only radiotherapy workflow for brain radiotherapy: Two-way dose validation and 2D/2D kV-image-based positioning.

Magnetic Resonance Imaging (MRI)-only workflow eliminates the MRI-computed tomography (CT) registration inaccuracy, which degrades radiotherapy (RT) treatment accuracy. For an MRI-only workflow MRI sequences need to be converted to synthetic-CT (sCT). The purpose of this study was to evaluate a commercially available artificial intelligence (AI)-based sCT generation for dose calculation and 2D/2D kV-image daily positioning for brain RT workflow. T1-VIBE DIXON was acquired at the 1.5 T MRI for 26 patients in RT setup for sCTs generation. For each patient, a volumetric modulated arc therapy (VMAT) plan was optimized on the CT, then recalculated on the sCT; and vice versa. sCT-based digitally reconstructed radiographs (DRRs) were fused with stereoscopic X-ray images recorded as image guidance for clinical treatments. Dosimetric differences between planned/recalculated doses and the differences between the calculated and recorded clinical couch shift/rotation were evaluated. Mean ΔD50 between planned/recalculated doses for target volumes ranged between -0.2 % and 0.2 %; mean ΔD50 and ΔD0.01ccm were -0.6 % and 1.6 % and -1.4 % and 1.0 % for organ-at-risks, respectively. Differences were tested for clinical equivalence using intervals ±2 % (dose), ±1mm (translation), and ±1° (rotation). Dose equivalence was found using ±2 % interval (p < 0.001). The median differences between lat./long./vert. couch shift between CT-based/sCT-based DRRs were 0.3 mm/0.2 mm/0.3 mm (p < 0.05); median differences between lat./long./vert. couch rotation were -1.5°/0.1°/0.1° (after improvement of RT setup: -0.4°/-0.1°/-0.4°, p < 0.05). This in-silico study showed that the AI-based sCT provided equivalent results to the CT for dose calculation and daily stereoscopic X-ray positioning when using an optimal RT setup during MRI acquisition.

Stable hydrogen and oxygen isotopes reveal aperiodic non-river evaporative solute enrichment in the solute cycling of rivers in arid watersheds

We investigated the spatial and temporal variations of the stable isotope composition of hydrogen (δD) and oxygen (δ18O) and the total dissolved ions (TDI) concentrations in the Okavango River in the middle Kalahari Desert. We aimed to elucidate the role of evaporation in controlling river solute enrichment from samples collected at a one- to two-month frequency from nine stations along a ∼460 km river transect for one year. We found that the δD and δ18O composition and the TDI concentrations increased downriver. Seasonal increases in the δD and δ18O composition and TDI concentrations during the hot, rainy season were subdued or decreased during the cool, dry season from pulse flooding. The δD and δ18O values of the samples plot along the Okavango Delta Evaporation Line consistent with evaporation. The effect of evaporation during river transit was related to the mean δD (δD = 0.07*River distance (km) − 37.9; R2 = 0.98) and mean d-excess (d-excess = −0.04*River distance (km) + 9.9; R2 = 0.94). The effect of evaporation on the river solute behavior is characterized by the mean d-excess and TDI concentrations (d-excess = −0.29*TDI (mg/L) + 15.0; R2 = 0.97). Some samples from this study and those compiled from published studies plot at greater than one sigma standard deviation above and below the mean TDI concentration vs. mean d-excess regression model line. We use these marked deviations from the mean TDI concentration vs. the mean d-excess regression model to suggest that additional solutes from river-floodplain-wetland-island interaction driven by pulse flooding are delivered into the river. While our findings support an evaporation-dominated solute enrichment during river transit at the seasonal scale, we conclude that intermittent hydrology (pulse flooding) plays an important role in the sub-seasonal spatiotemporal behavior of solutes in rivers in arid watersheds, which must be considered in solute cycling models.

Aesthetical and Accuracy Outcomes of Reconstruction of Maxillary Defect by 3D Virtual Surgical Planning.

BackgroundReconstruction of maxillary defect resulting from trauma or oncology surgery is of great importance for patients with physical and psychological complications. The virtual surgical planning (VSP) and 3D printing technics had been used in recent years which simplified the surgical procedure and promoted success and accuracy. To assess the accuracy and outcome of VSP surgery, here we report our experience in maxillary reconstruction retrospectively.MethodPatients who received maxillary defect reconstruction from 2013 to 2020 were analyzed retrospectively. These patients were divided into two groups. Group 1 received VSP and 3D printed guiding plates in the surgery, while group 2 underwent free-hand surgery (FHS). Patients with different vertical and horizontal defects were classified according to Brown and Shaw classification. Clinical information and postoperative complications of all patients were collected. For patients with unilateral maxillary defect, orbit volume, orbit height, and the contour of the reconstructed side were compared with the normal side.ResultThirty-four patients who achieved the criteria were analyzed, of which 20 patients underwent VSP surgery. There were primary and secondary reconstruction cases in both two groups. Vascularized iliac crest flap was used in three cases, and fibula flap was performed in the other cases. One flap collapse occurred in FHS group. Seven patients in VSP group received dental implants, while the number in FHS group was 0. In vertical class III cases, the differences in orbit height (ΔD) and orbit volume (ΔV) between normal side and reconstructed side were measured and compared in the two groups. The mean ΔD is 1.78 ± 1.33 mm in VSP group and 4.25 ± 0.95 mm in FHS group, while the mean ΔV is 2.04 ± 0.85 cm3 in VSP group and 3.25 ± 0.17 cm3 in FHS group. The alterations of orbit height and volume in VSP group were much smaller than that in FHS group with statistical significance. From the perspective of aesthetics, the color-gradient map indicates a more symmetric and smoother curve of post-operation appearance in VSP group.ConclusionCompared with traditional free-hand surgical technics, VSP and 3D printing guiding plates can allow for a more accurate maxillary reconstruction with improved aesthetics.

Feasibility of commercially available underwear during radiation therapy for breast cancer: build-up and surface dose measurements

AbstractAim:When patients receive radiation therapy for breast cancer, they need to take off their underwear to avoid build-up effects. However, it is a mental burden for female patients to take off their underwear at every fraction of radiation therapy. The purpose of this study was to investigate whether commercially available thin underwear can be worn during radiation therapy for breast cancer.Materials and methods:In this phantom study, we investigated whether commercially available underwear can be worn during radiation therapy for breast cancer using six thin non-disposable brassieres and one disposable paper brassiere. The dose increase rate (ΔD) was calculated by measuring skin doses with or without each brassiere.Results:The mean ΔD values of six non-disposable brassieres were 13.5% (9.0–21.8%), whereas that of disposable ones was 2.0%.Findings:Due to the risk of excessive radiation to the skin, wearing commercially available underwear is not recommended during radiation therapy for breast cancer, but a thin disposable paper brassiere may be safe to be used.

Alpine Holocene tree-ring dataset: age-related trends in the stable isotopes of cellulose show species-specific patterns

Abstract. Stable isotopes in tree-ring cellulose are important tools for climatic reconstructions even though their interpretation could be challenging due to nonclimate signals, primarily those related to tree aging. Previous studies on the presence of tree-age-related trends during juvenile as well as adult growth phases in δD, δ18O, and δ13C time series yielded variable results that are not coherent among different plant species. We analyzed possible trends in the extracted cellulose of tree rings of 85 larch trees and 119 cembran pine trees, i.e., in samples of one deciduous and one evergreen conifer species collected at the tree line in the Alps, covering nearly the whole Holocene. The age trend analyses of all tree-ring variables were conducted on the basis of mean curves established by averaging the cambial-age-aligned tree series. For cambial ages over 100 years, our results prove the absence of any age-related effect in the δD, δ18O, and δ13C time series for both the evergreen and the deciduous conifer species, with the only exception being larch δD. However, for lower cambial ages, we found trends that differ for each isotope and species; i.e., mean δ13C values in larch do not vary with aging and can be used without detrending, whereas those in cembran pine show a juvenile effect, and the data should be detrended. Mean δ18O values present two distinct aging phases for both species, complicating detrending. Similarly, mean δD values in larch change in the first 50 years, whereas cembran pine changes between 50 and 100 years. Values for these two periods of cambial age for δD and δ18O should be used with caution for climatic reconstructions, ideally complemented by additional information regarding mechanisms for these trends.

Dose prediction using a deep neural network for accelerated planning of rectal cancer radiotherapy

PurposeTo apply a deep neural network to predict dose distributions of rectal cancer patients for accelerated volume modulated arc technique (VMAT) planning. Materials and methodsComputed tomography scans and approved VMAT plans together with Doseapproved of 187 patients treated from February 2018 to April 2019 were randomly selected for this retrospective study. The deep neural network DeepLabv3+ was applied for dose distribution prediction. A prior dose information-aided planning scheme was introduced. Prediction precision was evaluated by mean square error (MSE), normalized dose difference (δD), and dose–volume histogram (DVH) indices using a paired t test. Information-aided and experienced replanning were performed by 1-year and 6-year experienced dosimetrists, respectively. Replanning time and DVH indices were evaluated by two-way variance analysis. ResultsThe DeepLabv3+ prediction results (DoseDeepLabv3+) were all clinically acceptable. Taking Doseapproved as the baseline, the MSE was 0.001 and mean δD was 0.40% with an inter-quartile range of 0.079%–0.30% for DoseDeepLabv3+. No significant differences were found for the planning target volume quantitative parameters between Doseapproved and DoseDeepLabv3+, except for the conformality index. For the two-way variance analysis, a significantly different replanning time was found between the information-aided and experienced replanning with maximum time-saving of 15.76 min. Information-aided replans had the advantage of lower maximum dose, higher minimum dose, and lower homogeneity index, and the disadvantage of lower conformality index and higher machine unites with significant differences. ConclusionDeepLabv3+ successfully predicted rectal cancer dose distribution, and the predicted prior information helped save planning times for multi-level experienced dosimetrists.

Water Sources and Factors Controlling Hydro-chemical Compositions in the Yiluo River Basin

An important tributary in the middle stream of the Yellow River, the Yiluo River consists of the Luohe River and Yihe River, which converge at Yanshi City. Mining activities were widely distributed in the upstream of the Yiluo River Basin (YRB), while residential areas concentrated in the downstream were coupled with extensively industrial and agricultural activities. To illustrate the influences of variable anthropogenic activities on the hydro-chemical composition of river water of the YRB, water samples from the main stream and tributaries were collected in the flood season (August) and normal season (December), respectively. The hydrogen and oxygen isotope values coupled with cation and anion content were analyzed. Temporal and spatial variations of hydrogen and oxygen isotopes and ion content were utilized to elucidate the sources and factors controlling the hydro-chemical composition of the river water, and to illustrate the pathways of human effects. The results demonstrated that:① Average hydrogen and oxygen isotope values (δD and δ18O) of Luo River water were -56‰ and -7.9‰, and -55‰ and -8.1‰ in the flood season and normal season, respectively. Mean δD and δ18O values of Yi River water were -49‰ and -6.9‰, and -53‰ and -7.8‰ in the flood season and normal season, respectively. These temporal variations indicated that river water was mainly recharged by local atmospheric precipitation. ② The dominant water hydro-chemical type was HCO3-SO4-Ca-Mg in the main stream of the YRB, and the ratios of Ca2+ and HCO3- molar equivalent concentrations in the flood season were lower than those in the normal season, while the ratios of SO42- molar equivalent concentrations were higher than those in the normal season, indicating more sulfate dissolved in the river water in the flood season. ③ Carbonic acid and sulfuric acid simultaneously reacted with carbonate and silicate rocks, and in the Luo River more carbonate rocks were weathered, while in the Yi River more silicate rocks were weathered. ④ Human effects on river water were mainly concentrated in the upstream where wastewater input was derived from mining activities, while in the downstream pollution of the river was due to industrial wastewater and sewage input. ⑤ Spatial variations of sulfate sulfur isotope values were mostly due to differences between anthropogenic activities in the upstream and downstream of the Yiluo River. Negative sulfur isotope values in the upstream river water confirmed dissolved sulfate from sulfide mineral oxidation, which also indirectly verified the rock chemical weathering by sulfuric acid in this area. Positive sulfur isotope values in downstream river water were connected with industrial wastewater and sewage.

An entropy-based analysis method of precipitation isotopes revealing main moisture transport corridors globally

Abstract The hydrogen (δD) and oxygen (δ18O) isotopic compositions in the water molecule have been widely used as tracers for studying the global water cycle. In 1961, the Global Network of Isotopes in Precipitation (GNIP) was established to measure D and 18O isotopes contents in precipitation around the world. However, on the spatial scale, the long-term arithmetic and/or long-term precipitation weighted mean δD and δ18O have been most commonly used to interpret the GNIP isotope data for over sixty years. The spatial distributions of mean δD and δ18O depict well the regional moisture transport, but they vary predominantly with latitude on the global scale, especially over continental areas, obscuring the continental and circulation effects. We developed a new method of using the entropy concept to reanalyze precipitation isotopic compositions data from GNIP. Calculated entropies of isotopic compositions in precipitation at GNIP stations around the world strongly correlate in a linear fashion with a slope coefficient close to unity. The spatial distributions of both isotopic compositions entropies generally reveal oceanic sources of water vapor and main moisture transport pathways from oceans to continents globally, with different patterns between summer and winter seasons. Although these results have mostly been reported in previous studies, they provide the verification of this new analysis method. The entropy method proposed here is expected to provide a new tool for data interpretation of water isotopic compositions, with implications for tracing global hydrological processes.

Stable isotope signatures of Holocene syngenetic permafrost trace seabird presence in the Thule District (NW Greenland)

Abstract. Holocene permafrost from ice wedge polygons in the vicinity of large seabird breeding colonies in the Thule District, NW Greenland, was drilled to explore the relation between permafrost aggradation and seabird presence. The latter is reliant on the presence of the North Water Polynya (NOW) in the northern Baffin Bay. The onset of peat accumulation associated with the arrival of little auks (Alle alle) in a breeding colony at Annikitisoq, north of Cape York, is radiocarbon-dated to 4400 cal BP. A thick-billed murre (Uria lomvia) colony on Appat (Saunders Island) in the mouth of the Wolstenholme Fjord started 5650 cal BP. Both species provide marine-derived nutrients (MDNs) that fertilize vegetation and promote peat growth. The geochemical signature of organic matter left by the birds is traceable in the frozen Holocene peat. The peat accumulation rates at both sites are highest after the onset, decrease over time, and were about 2-times faster at the little auk site than at the thick-billed murre site. High accumulation rates induce shorter periods of organic matter (OM) decomposition before it enters the perennially frozen state. This is seen in comparably high C∕N ratios and less depleted δ13C, pointing to a lower degree of OM decomposition at the little auk site, while the opposite pattern can be discerned at the thick-billed murre site. Peat accumulation rates correspond to δ15N trends, where decreasing accumulation led to increasing depletion in δ15N as seen in the little-auk-related data. In contrast, the more decomposed OM of the thick-billed murre site shows almost stable δ15N. Late Holocene wedge ice fed by cold season precipitation was studied at the little auk site and provides the first stable-water isotopic record from Greenland with mean δ18O of -18.0±0.8 ‰, mean δD of -136.2±5.7 ‰, mean d excess of 7.7±0.7 ‰, and a δ18O-δD slope of 7.27, which is close to those of the modern Thule meteoric water line. The syngenetic ice wedge polygon development is mirrored in testacean records of the little auk site and delineates polygon low-center, dry-out, and polygon-high-center stages. The syngenetic permafrost formation directly depending on peat growth (controlled by bird activity) falls within the period of neoglacial cooling and the establishment of the NOW, thus indirectly following the Holocene climate trends.

Impact of hotel septic effluent on the Jinfoshan Karst aquifer, SW China

The karst aquifer of Jinfoshan Karst (JFK) in UNESCO’s South China Karst World Heritage Site was investigated. An artificial tracer test, geochemistry, and oxygen and hydrogen isotopes were employed to assess the impacts of effluent from the Jinfoshan Holiday Hotel (JHH), Chongqing, on the karst aquifer and its outlet, Shuifang spring (SFS). Most of the fluorescent dye (uranine) flushed into a JHH toilet was recovered at SFS, suggesting a strong hydraulic connection between JHH and SFS. The waters of SFS were of HCO3–Ca type, whereas the effluent had more complex hydrochemical characteristics. The effluent was characterized by higher mean δD and δ18O values. The slope of the δD–δ18O evaporation line for effluent was significantly lower than that of the local meteoric water line, indicating evaporation. Concentrations of major elements at SFS were below the threshold values of the Chinese Standard for Groundwater Quality. However, hydrogen and oxygen isotopic compositions of SFS waters were influenced by the effluent and mixing with water from diffuse sources within the aquifer. Low values of d-excess at SFS corresponded well to periods of high tourism activity (weekends and holidays), suggesting that declining d-excess probably signifies an increased release of contaminants from the hotel. The contribution of effluent to the discharge of the SFS was ~18%. Because of tourism activities and their production of wastewater, the results of this study may be relevant to other karst environments and World Heritage Sites throughout the world.

A Pilot Study of Trophic Level and Human Origins at the Xiaoshuangqiao Site, China (ca. 1400 BC) Using δD Values of Collagen

AbstractWe present here a pilot study to examine trophic level effects and migration patterns at the middle Shang Dynasty site of Xiaoshuangqiao in Henan Province using δD results combined with δ13C and δ15N values. A total of 33 specimens (17 humans, 7 cattle, 5 pigs, 3 sheep, 1 dog) of bone collagen were isotopically analyzed for δ13C, δ15N, and dD values. A strong positive correlation (R2 = 0.94) between mean δ15N and δD values of herbivores (cattle and sheep), omnivores (pig), carnivores (dog) and humans was observed. The δD results were found to increase by ∼10‰ to 20‰ from herbivores to omnivores to carnivorous, evidence that collagen δD results are a useful indicator for the study of trophic levels and dietary patterns at archaeological sites. The δD results were also used to examine the origins of two different groups of individuals buried at Xiaoshuangqiao. Individuals buried in sacrificial pits of district V had mean δD values (−47.0 ± 2.9‰, n = 11) that were significantly (p = 0.049) elevated compared to the people buried in the stratigraphy of district IX (−51.3 ± 3.3‰, n = 3), indicating that they were ingesting water from different locations. In addition, the D values of the people buried in the stratigraphy were similar to the pigs (−54.5 ± 4.2‰, n = 5) at Xiaoshuangqiao, suggesting that they were most probably of the local population, and that the individuals buried in the sacrificial pits were most possibly from the coast and prisoners of the Dongyi (“东夷”) people. Thus, δD results have the potential to examine human origins and migration patterns and should be increasingly used in conjunction with δ13C and δ15N values at archaeological sites.

Last glacial and Holocene stable isotope record of fossil dripwater from subtropical Brazil based on analysis of fluid inclusions in stalagmites

The stable isotope composition of fossil dripwater preserved in stalagmites fluid inclusions is a promising tool to reconstruct paleopluviosity in the tropics and subtropics. Here we present δD and δ18O records of fossil dripwater from two stalagmites collected in Botuverá Cave (subtropical Brazil), covering the last glacial period and the Holocene. The observed millennial-scale variability of fossil dripwater δD and δ18O values is of the order of 10 to 20‰ and 1 to 3.5‰ (V-SMOW), respectively. Fluid inclusion δD and δ18O values are higher than the weighted mean δD and δ18O values of modern precipitation, suggesting a possible intensification of extratropical cold surges during both the last glacial period and the Early Holocene, followed by a progressive Late Holocene transition towards modern pluviosity conditions. Fluid inclusions δ18O values vary in parallel with stalagmite δ18O values during the Holocene but not during the last glacial period. This suggests that the δ18O value of precipitation may not be the only dominant factor controlling the δ18O values of the analyzed stalagmites. Isotope disequilibrium effects arising from Prior Calcite Precipitation (PCP) possibly affected stalagmites δ18O values to a greater extent than previously considered, though this effect does not bias non-quantitative paleopluviosity reconstructions based on stalagmite δ18O values. Isotope-based paleotemperature calculated for the Late Holocene matches modern cave temperature (19°C) within ±2.4°C. This encourages further application of isotope analyses of fluid inclusion for climatic reconstructions.

Stable hydrogen and oxygen isotope compositions in soil-plant-atmosphere continuum (SPAC) in rocky mountain area of Beijing, China

The stable hydrogen and oxygen isotopes are environmental isotopes, which widely exist in various kinds of water. Their relative abundance variation in water can indicate the water circulation and mechanism of water use in plant. This research selected two major kinds of greening tree species, evergreen coniferous Platycladus orientalis and deciduous broad-leaved Quercus variabilis, in Beijing mountainous area, and the water movement process in soil-plant-atmosphere continuum was investigated by the variation characteristics analysis of stable hydrogen and oxygen isotope compositions in precipitation, soil water, groundwater, plant stem water and leaf water. The results showed that the meteoric water line equation of the study area was δD=7.17δ18O+1.45 (R2=0.93), and the soil evaporation line equation was δD=3.85δ18O+1.45 (R2=0.76). A certain degree of evaporation fractionation existed in the processes of rainfall infiltration into soil water. In different seasons, the δD and δ18O values of precipitation, soil water and spring water had different variation regularity. In rainy season, the mean δD and δ18O values were in order of precipitation> spring water>soil water, with the precipitation and soil water supplied spring water together; in dry season, the order was precipitation > soil water > spring water, and the precipitation and spring water both contributed to soil water. The δD and δ18O fitting line equations of stem water of P. orienta-lis and Q. variabilis were respectively δD=5.03δ18O-30.78 and δD=3.0δ18O-48.92. The uptake water of Q. variabilis was more enriched than that of P. orientalis, and the depth of Q. variabilis water uptake in soil profile was shallower than P. orientalis. The leaf water isotopic variation of Q. varia-bilis was more sensitive to atmospheric environment, with the kinetic isotopic fractionation of Q. variabilis being more enriched than that of P. orientalis, but they had the same response to variation of environmental condition.

A particle filter based autocontouring algorithm for lung tumor tracking using dynamic magnetic resonance imaging.

This study introduces a novel autocontouring algorithm based on particle filter for lung tumors. It is validated on dynamic magnetic resonance (MR) images and is developed in the context of MR-linac treatments. A sequential Monte Carlo method called particle filter is used as the main structure of the algorithm and is combined with Otsu's thresholding technique to contour lung tumors on dynamic MR images. Four non-small cell lung cancer (NSCLC) patients were imaged with a 1.5 T MR for 60 s at a rate of 4 images/s and were asked to breathe normally. Prior to treatment, some image processing is required by the proposed algorithm, which includes a manual contour of the tumor, the tumor's displacement, and its descriptive statistics. During treatment, the contours are automatically generated by thresholding around the center of mass of the particles. A comparison with the expert's contours is obtained by calculating the Dice similarity coefficient (DSC), the precision, the recall, the Hausdorff distance, and the difference in centroid positions (Δd). This autocontouring algorithm is independent of pretreatment training and presents continuous adaptability as provided by the nature of particle filters. The number of particles is proportional to the area of the tumor and increases the computational time at a rate of 2 ms for every 500 particles, whereas the contouring step adds a constant 14 ms. The contours' comparison is obtained with a mean DSC of 0.89-0.91, mean precision of 0.88-0.91, mean recall of 0.89-0.95, and mean Δd of 0.6-2.0 mm. This work presents a proof of concept of a new autocontouring algorithm for NSCLC patients on dynamic MR images. The contours were generated in good agreement with the expert's contours.