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Identification of sources and transport pathways of heavy metals and major ions is crucial for effective water quality monitoring, particularly in large river systems. The Ganges river basin, the largest and the most populous river basin in India, remains poorly studied in this regard. We conducted a basin-level analysis of major ions, heavy metals, and stable isotopes of nitrate in the Ganges during the pre-monsoon season to constrain the sources and quantify the inorganic chemical composition of the river during its lean flow. Bedrock weathering, anthropogenic interferences, water contribution through tributaries, and surface water-groundwater interaction were identified as the major driver of metal and ion variability in the river. Heavy metals showed the highest concentrations in the upper section of the river, whereas ionic loads were the most variable in the middle. We find a significant impact of tributaries on the metal and ion concentrations of the Ganges in its lower reaches. Isotopic analysis of dissolved nitrate suggested synthetic fertilizers and industrial wastes as the main sources. We find that the otherwise clean waters of the Ganges can show high ionic/metallic concentrations at isolated stretches (As: up to 36 µg/L), suggesting frequent monitoring in the source region to maintain water quality. Except for water collected from the Yamuna and Kannauj in the middle stretch and the Alaknanda and Rishikesh in the upper stretch, the WQI showed acceptable water quality for the sampled stations. These findings provide an insight into the modifications of dissolved inorganic chemical loads and their sources in different sections of the basin, needed for mitigating site-specific pollution in the river, and a roadmap for evaluating chemical loads in other rivers of the world.

A continuous bi-weekly water isotope analysis (δ18O, δD, and d-excess) was done since 2015 from a subtropical reservoir (Feitsui Reservoir) in northern Taiwan. The Feitsui reservoir is an important national freshwater system, as it provides water for the large urban population of Taipei. The isotopic data reveals a multiyear pattern and it closely follows the rainfall isotopic composition. We made a simple mass-balance model using the rainfall isotopic composition, inflow and outflow volumes, and meteorological parameters that fit well (R2 = 0.55; p-value < 0.05) with the observed isotopic composition of the reservoir. Based on this model, we estimated reservoir isotopic composition for the previous 20 years (2001-2021). The model also well reproduced a few years of historical data reported in the literature. In the model, we noted two conspicuous patterns: (1) multiyear cyclicity in δ18O and d-excess, and (2) a long-term enriching trend in δ18O. These patterns were not so obvious in rainfall because of the strong seasonality, which gets diluted in the reservoir because of the longer water residence time (~6 months). However, these patterns became visible in rainfall isotopes after removing the seasonal cycles. The observed multiyear patterns do not resemble with the known multiyear global processes, such as ENSO, PDO, and the East Asian Monsoon Index. However, the role of these global processes cannot be ruled out completely. We believe that because of the unique geographical location of the island, multiple moisture sources (South China Sea and central/northern China), dual monsoons (summer and winter monsoons), and complex hydrometeorological processes, the signals of these multiyear global processes get modulated and modified. The long-term enriching trend in δ18O seems to be a consequence of climate change. The enriching trend is more vivid during the winters than summers. This indicates the possible role of global warming and the expansion of the tropics because the Tropics of Cancer passes through central Taiwan. There also remains a significant knowledge gap in understanding the role of winter monsoons in East Asia. This study highlights the importance and the need for rigorous climatic research in Taiwan because of its unique location which makes it highly sensitive to climate change. This study may also have implications for paleoclimatic studies because it highlights the complex hydrometeorology of the region.

The detailed assessment of water resources and hydrological cycle component are very critical for attaining sustainable development goals (SDGs) in a region. One of the critical challenges in water cycle science is to understand the source of water in a river which vary seasonally and spatially. Here we deal with the spatial pattern of a river in the North Eastern Himalayas, which receives groundwater and snow meltwater supply to meet the perennial flow regime. We used stable water isotopes of oxygen & hydrogen in the river water sampled during pre-Monsoon season. This study focusses on the region of West Kameng District of Arunachal Pradesh, India covering drainage basin of 2 tributaries of Kameng river basin viz. Tenga & Dirang as shown in Figure 1. Our study used isotopic method to trace the sources of which forms river water at the headwater regions.The Local Meteoric Water line (LMWL) for the region is defined by δD = (8.046 ± 0.03). δ18O + (11.644 ± 0.5‰) as derived from analysis of water samples collected in March 2021. This LMWL is almost identical to the signature of precipitation collected during April – October, 2007 from station at Cherrapunjee Meghalaya, India as obtained from IAEA-GNIP data [δD = 8.068 δ18O + 12.347‰] as shown in Figure 2. The d-excess signatures from the two set of observations near similar, 11.21± 1.79 ‰ & 11.41± 2.21‰ respectively implying that river and rainwater in the study region are indistinguishable. Based on the observation we commented on the baseflow contribution of the river. Result suggests places where groundwater contribution to the river water is significantly high during dry time and overall enrichment of river water composition due to this process. We will provide estimate of base flow contribution based on mass balance equation, which is prominent more than 90% at higher elevation. The volume of the aquifer is large given the long residence time & can be estimated by timebound analysis of stable isotopes and tritium isotope.

Vehicular catalytic converters are used to regulate, reduce, and convert toxic and environmentally unfriendly compounds in exhaust gases into relatively inert and less harmful chemical species. The efficiency, however, is largely affected by the operating temperature of the converter which is set by the hot exhaust gas released from the combustion chamber. A major gas released during combustion is CO2, and its multiply substituted isotopocule, namely, 13C16O18O, provides a window of opportunity to probe directly the effective temperature of the converter in operation. Here, we report multiple isotopic measurements in exhaust CO2 (δ13C, δ17O, δ18O, and Δ47) of diesel (trucks and buses) and gasoline (sedans, trucks, and two-wheel motorcycles)-powered vehicles. For investigating the efficiency of a converter in reducing toxic compounds, we studied NOx processes through isotopic analysis of the exhaust N2O. We found that the degree of N2O reduction to N2 in gasoline-powered vehicles is high when the temperature is above 200 °C (inferred by Δ47). In contrast, diesel-powered vehicles produce N2O in abundance, probably a consequence of selective catalytic reduction of NOx, and the reduction efficiency depends on the converter temperature. In other words, the catalytic converters act as sinks and sources of N2O to the atmosphere in gasoline- and diesel-operated vehicles, respectively. We also report a new set of field data by measuring the isotopic compositions of CO2 and N2O in the Hsuehshan tunnel, a ∼13 km long highway tunnel in Taiwan. Elevated N2O concentrations inside the tunnel indicate that the emission of N2O by heavy-duty diesel vehicles is much higher compared to the reduction by gasoline-operated passenger cars, making the vehicular exhausts a net source of N2O to the atmosphere. The combined study of clumped isotopes and N2O concentration in exhaust gases suggests that it is useful to probe the operational temperature of catalytic converters and monitor the pollution level in operation, thus providing an opportunity for manufacturers to optimize the catalytic efficiency to reduce the level of toxic pollutants to the environment.

The intertrappean sediments and the bole beds of the Deccan volcanic province hold clues to the climatic condition in India during the Cretaceous/Paleocene transition. Earlier isotopic studies of the bulk clays from the ‘bole beds’ showed that the rainwater composition was lighter (δ18O -8‰) relative to the present-day (δ18O ~ -5‰). This was ascribed to an increase in the rainfall (amount effect). However, later reconstruction of the mean annual precipitation (MAP) from the intertrappean paleosol carbonates suggested that the amount was no different than the modern-day precipitation. One possible reason for this disagreement can be due to the low preservation potential of proxies used in these studies. The present study was carried out by analysing authigenic silica which is resistant to post-depositional modifications. Such silica deposits are abundant throughout the Deccan intertrappean sediments occurring as cherts, chertified limestone and silicified fossils. They form during the interaction of silica-rich water with the existing sediments or fossils, the silica being derived by leaching of the volcanic ash by surface run-off and/or from siliceous hydrothermal waters. Silicified woods were analyzed for their triple oxygen isotope ratios (expressed as δ17O and δ18O) to determine the silicification temperature and the isotopic composition of the silicifying fluid. The distribution of the obtained silicification temperature and water composition of diverse samples indicates a widely variable silicification environment. The silicification took place at temperatures from 25°C (near surface temperature) to 90°C (at relatively shallower levels of 50-100 m). In addition, the δ18O (VSMOW) values of silicification fluid varied from -14‰ to near 0‰. The geological, floral and faunal evidence suggest deposition of these woods in a continental fluvio-lacustrine environment. Isotope modelling of the data suggest a two-component fluid mixing between hydrothermal water and a lake water. Assuming this fluid to be derived from a mixture of meteoric water and volcanic hydrothermal water, the δ18O value of the local meteoric water is estimated to be -14‰ to -12‰. These values are lower by about 9‰ to 7‰ compared to today (mean annual δ18O over central India being ~-5‰). We ascribe this to an increase in the mean annual rainfall by about 400 mm. It is possible that the late cretaceous precipitation increased due to the warming caused by a high CO2 environment.

Stable oxygen isotopic composition (δ18O) of CO2 produced from carbonates in natural archives is a useful proxy for paleo precipitation and paleo temperature reconstruction. However, there exist multiple factors controlling the δ18O values, the applications of the δ18O alone for paleoclimate studies are thus limited. Anomaly in 17O in carbonates, expressed by Δ′17O=1000*ln(δ17O/1000+1)-λ*1000*ln(δ18O/1000+1) is another proxy to independently constrain aspects of climatic variables such as precipitation source variation and kinetic effects during carbonate precipitation. However, to use 17O anomaly for such studies, the triple oxygen isotope fractionation exponent (θ= lnα17/lnα18) must be known precisely. Knowledge of this parameter is central to emerging applications of carbonate triple oxygen isotopes to paleoclimate and paleo-hydrology studies. Though a number of theoretical and experimental studies have been carried out in the last few years, there remains no consensus on 𝛳 value for carbonate-water system, likely due to kinetic isotope fractionation during precipitation.Here, we measured Δ′17O in synthetic carbonates as well as in the water from which the carbonates are precipitated to check how reliable the Δ′17O value of the parent water can be reconstructed from the carbonates or carbonate-digested CO2. To determine θcarbonate_CO2-water for precipitated carbonates, we synthesized carbonates in the laboratory at temperatures ranging from 10 ⸰C to 66 ⸰C using passive/active CO2 degassing method. Triple oxygen isotope compositions of the water were determined using water-CO2 equilibration followed by CO2-O2 exchange method and of the carbonate (CO2 liberated by acid digestion) using CO2-O2 exchange method. We analyzed our isotope data for their possible kinetic isotope effect and determined the 𝛳carbonate_CO2-water value for precipitated carbonates. We find that most of our synthetic carbonate samples did not attain the equilibrium. The 𝛳carbonate_CO2-water increases as the disequilibrium effect increases. We determined the θcarbonate_CO2-water from the samples precipitating in equilibrium. Furthermore, we do not find any differences in the 𝛳carbonate_CO2-water value for carbonate precipitated in equilibrium at 25 ⸰C and 35 ⸰C. An important issue of using Δ′17O in carbonates is to resolve the 𝛳acid for acid digestion which is resolved in the present study. Additionally, we determined the temperature dependent variation in 𝛳acid and find no significant changes between 0 ⸰C and 70 ⸰C.

Nitrogen fertilizers result in high crop productivity but also enhance the emission of N

We report the oxygen isotopic anomaly (Δ17O) and clumped isotopic composition (Δ47) of CO2 sampled from the middle troposphere (~10 km above ground) during two CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) flights in summer and winter seasons: one from Düsseldorf to Isla Margarita on 11 August 2001 and the other from Puerto Plata to Munich on 21 February 2002. The mid‐tropospheric Δ17O values were higher than the near‐surface values by 0.051 ± 0.010 ‰, indicating enhanced stratospheric influence. The Δ47 values were also higher by 0.160 ± 0.015 ‰ compared to that from the lower troposphere. Stratospheric influence is supported by the observed correlations of the Δ17O values with the mixing ratios of N2O, O3, and 14CO, which carry stratospheric signatures. The increase in the anomaly in the free troposphere represents a balance between the stratosphere‐troposphere exchange fluxes and biogeochemical/hydrospheric isotopic resetting rates at the Earth surface. Using a simple two box model with the free tropospheric Δ17O values, an average surface exchange rate of CO2 between 327 and 772 PgC/year is inferred, giving a CO2 turnover time of 1.4 to 2.8 years in the atmosphere. The present estimates are based on a rather small set of free tropospheric data and have relatively large uncertainties, but they agree with the existing model and proxy‐based estimates.

The isotopic enhancement of atmospheric ozone (O3) is mainly determined by two processes of formation and photolytic decomposition. The formation is known to be associated with isotopic fractionation which can be as high as 120‰ relative to the parent oxygen. Photolysis‐induced isotopic fractionation in O3, however, is not known accurately. Absorption cross sections of various ozone species have been calculated by Zero Point Energy‐based model and quantum mechanical wave packet model. But their predictions pertaining to isotopic fractionations have not been verified experimentally. In the present work, we performed irradiation experiments of O3 at several wavelengths in the Hartley and Chappuis bands and determined the dissociative isotopic fractionation factors by a Rayleigh distillation model. In laboratory conditions, photolysis of ozone produces reactive atomic and/or molecular oxygen which influence the dissociative process through secondary chemistry. The complex interplay of primary photolysis and secondary chemistry was tracked by a kinetic model, and isotopic fractionation factors associated with photolysis alone were derived within a range of uncertainties. The fractionations are found to depend on the photon wavelength and deviate significantly at some wavelengths from the predicted values. For example, at 254 nm the zero point energy‐based models predict lower photolysis rate coefficients for the lighter isotopic species; the present data show about 50‰ higher values.

Vehicular catalytic converters are used to regulate, reduce, and convert toxic and environmentally unfriendly compounds in exhaust gases into relatively inert and less harmful chemical species. The efficiency, however, is largely affected by the operating temperature of the converter which is set by the hot exhaust gas released from the combustion chamber. A major gas released during combustion is CO

South China Sea (SCS), world’s largest marginal sea, plays an important role in the global as well as regional biogeochemical cycling of carbon and oxygen. However, its overall metabolic balance, primary production rates, and their link to East Asian Monsoon forcing still remain poorly constrained. Here, we report seasonal trends in triple oxygen isotope composition (17Δ) of dissolved O2, a tracer for biological O2, gross primary production (GP; inferred from δ17O and δ18O values), and net community production (NP; evaluated from oxygen–argon ratios) from the SouthEast Asian Time-series Study (SEATS) in SCS. Our results suggest stable mixed-layer GP rates of 1.8 g C m−2 d−1 and NP of −0.02 g C m−2 d−1 during the summer southwest monsoon, indicating the prevalence of net heterotrophy. During winter months characterised by stronger northeast monsoon forcing, the system is more dynamic with variable production rates, which may shift the metabolism from net heterotrophy to net autotrophy (NP up to ~0.15 g C  m−2 d−1). These findings underscore the importance of monsoon intensity on tilting the carbon balance from source to sink in a warm oligotrophic sea, and on driving the regional circulation pattern. Finally, our data from the deeper regions show that SCS circulation is strongly affected by monsoon wind forcing, with a larger part of the water column down to at least 400 m depth fully exchanged during a winter, suggesting the 17Δ of deep O2 as a valuable novel conservative tracer for probing mixing processes from a new perspective.

We present analyses of nitrogen and oxygen isotopic ratios and site‐preference (SP) values of atmospheric nitrous oxide samples obtained from Taiwan in west Pacific. Air samples were collected during September 2013 to January 2016 from Taipei and during November 2011 to December 2014 from Keelung, located in the northeastern coast of Taiwan. The average values of δ15N, δ18O, and SP are 6.4 ± 0.3 ‰, 44.0 ± 0.4 ‰, and 17.1 ± 1.0 ‰, respectively, at Taipei and 6.4 ± 0.2 ‰, 44.6 ± 0.4 ‰, and 17.9 ± 1.3 ‰, for δ15N, δ18O, and SP respectively, at Keelung, comparable to the average values (6.6 ± 0.2, 44.2 ± 0.2, and 18.1 ± 0.5 ‰, scaled to year 2014) from Hateruma, an open ocean station in western Pacific. Strong temporal variations in the delta values, however, are seen. During a subtropical jet‐strengthening period in October to mid‐December 2014, the δ15N, δ18O and SP values increased at the rate of 0.006 ± 0.002 ‰/day, 0.010 ± 0.002 ‰/day and 0.008 ± 0.002 ‰/day, respectively at Taipei and 0.013 ± 0.005 ‰/day, 0.011 ± 0.005 ‰/day and 0.011 ± 0.027 ‰/day at Keelung. This suggests intrusion of air to the lower troposphere from the stratosphere where δ15N, δ18O and SP values are higher. This is consistent with earlier observations of oxygen isotope anomaly in atmospheric CO2 and elevated 35S in sulfate aerosols, indicating frequent stratospheric intrusions in this region. The observed δ15N and δ18O values, along with the oxygen isotope anomaly in CO2 and multiple sulfur isotopes in sulfate, can be used to constrain local emissions from the surface, improving our knowledge of anthropogenic contribution to the global budget of N2O.

The thermal physiology of non-avian dinosaurs, especially the endothermic/ectothermic nature of their metabolism, inferred indirectly using body mass, biophysical modelling, bone histology and growth rate, has long been a matter of debate. Clumped isotope thermometry, based on the thermodynamically driven preference of 13C-18O bond in carbonate minerals of fossilized eggshells, yields temperature of egg formation in the oviduct and can delineate the nature of thermoregulation of some extinct dinosaur taxa. In the present study, the clumped isotope thermometry was applied to the eggshells of a few species of modern birds and reptiles to show that it is possible to obtain the body temperatures of these species in most of the cases. We then used this method to the fossil eggshells of Late Cretaceous sauropods and theropods recovered from western and central India. The estimated body temperatures varied between 29 °C and 46 °C, with an overall average of 37 °C, significantly higher than the environmental temperature (about 25 °C) of this region during the Late Cretaceous. The results also show that the theropod species with low body masses (~800 kg) had high body temperature (~38 °C), while some gigantic (~20000 kg) sauropods had low body temperatures that were comparable to or slightly higher than the environmental temperature. Our analyses suggest that these Late Cretaceous giant species were endowed with a capacity of variable thermoregulation to control their body temperature., Earth sciences, Paleobiology, Geochemistry, Dinosaur, Eggshell carbonate, Clumped isotopes, Body temperature, Thermal physiology.

RATIONALE In 'clumped isotope paleothermometry' carbonates are reacted with anhydrous phosphoric acid to extract CO2 that carries the isotopic signature of the reacting carbonates, and the amount of clumping in the product CO2 is measured. Previous theoretical models for determining clumped isotopic fractionation in product CO2 during acid digestion of carbonates are independent of the cations present in the carbonate lattice. Hence further study is required to understand the cationic effect. METHODS We studied the acid reaction mechanism based on the protonation of carbonates, calculated the acid fractionation factor for dolomite using the partition functions and vibrational frequencies obtained for the transition state structure, and determined the effect of cations on the acid fractionation factor. Experimentally, carbonates are reacted using the modified sealed vessel method and analyzed in the dual inlet of a ThermoFinnigan MAT 253 isotope ratio mass spectrometer. RESULTS The oretically obtained acid fractionation factor can be expressed as Δ47 acid fractionation in dolomite = -0.28563 + 0.49508 * (105 /T2 ) - 0.08231 * (105 /T2 )2 for a temperature range between 278.15 and 383.15 K. The theoretical slope of the dolomite-acid digestion curve is lower than that of the calcite-acid digestion curve obtained using the identical reaction mechanism. Our theoretical slope is consistent with the result from the common acid bath experiments but higher than the slope obtained in our experimental study using the modified sealed vessel method and in a previous theoretical study using the H2 CO3 model. CONCLUSIONS The transition state structure, obtained in our study, includes the cations present in the carbonate minerals and provides distinct acid fractionation factors for calcite and dolomite. The observed gentler slope of the theoretically calculated dolomite-acid digestion curve than of the calcite curve is expected considering the stronger Mg-O bond. Our experimental approach invokes post-digestion isotopic exchange and agrees with the previous theoretical estimates where post-digestion isotopic fractionation was considered.

Feitsui Reservoir, a freshwater body in Taiwan with minimal anthropogenic stress, meets the water demand for the population of more than five million living in Taipei city. In view of the biogeochemical processes controlling the long-term trophic status of this socio-economically and ecologically important aquatic system, probing the nitrogen cycle and its dynamics is essential. Here, we monitored the concentration and stable isotopic compositions (δ

Air quality in the megacity Delhi is affected not only by local emissions but also by pollutants from crop residue burning in the surrounding areas of the city, particularly the rice straw burning in the post monsoon season. As a major burning product, gaseous CO

Electron irradiation of ice is an important process in the Solar System, especially for icy satellites (e.g., Europa) whose tenuous atmospheres originate from the thermal and radiation-induced outgassing of their icy surfaces. Laboratory experiments have been performed on the electron irradiation of water ice to study the volatile gases (e.g., H2 and O2) that leave the surface and the chemical compounds (e.g., H2O2) that are produced inside the ice. Semi-empirical models have also been developed to estimate the production of the chemical species in the ice during irradiation as functions of electron energy and ice temperature. In this study, we build a chemistry-transport model to simulate chemical processes occurring in the ice during irradiation by 10 keV electrons and to describe how the chemical species of interest are formed, transported, and distributed in the ice. The simulated H2O2 mixing ratio agrees well with experiments performed by Hand and Carlson (2011). Our model can be applied to the surfaces of icy satellites (e.g., Europa) to estimate the oxidant generation in the ice and to evaluate the potential habitability of those satellites. This study calls for further experimental studies on ice under electron irradiation to constrain critical parameters such as rate coefficients and diffusion coefficients of volatile species produced by radiation in the ice.

Beryllium-7 (7Be), produced by the interaction of cosmic radiation with atoms and molecules primarily in the upper troposphere and lower stratosphere, provides a useful tracer of cross-tropopause transport and vertical mixing in the troposphere. In the western Pacific subtropical region, the interaction of the subtropical jet stream with monsoon systems potentially enhances the transport. Here, we report one year of 7Be measurements at daily resolution during 2010, at Mt. Lulin (2862 m above mean sea level; NOAA code: LLN), along with other gaseous compounds such as O3 and CO and meteorological information, to assess processes that affect the variability of 7Be. The 7Be concentrations are of the order 1 mBq/m3 or less. The 7Be activity is generally low during summer, largely due to precipitation and unfavorable conditions of atmospheric dynamics (i.e., prevalence of upward motion), but it is occasionally high because of the influence of typhoons. In winter and spring, stratospheric effects observed at the surface were frequent and significant, thereby directly affecting the strength of stratospheric effects on the troposphere, such as the tropospheric oxidation capacity. The effects of the stratospheric intrusions are seen by negative and positive correlations of 7Be with relative humidity and concentration of O3, respectively. The stratospheric effect is further supported by the presence of downwelling transport in this region in the European Centre for Medium-Range Weather Forecasts-Atmospheric Composition Reanalysis Version 4 CO, O3, and relative humidity data.

Author(s): Li, KF; Lin, LC; Bui, XH; Liang, MC | Abstract: We have retrieved the latitudinal and vertical structures of the 11nyear solar cycle modulation on ionospheric electron density using 14nyears of satellite-based radio occultation measurements utilizing the Global Positioning System. The densities at the crests of the equatorial ionization anomaly (EIA) in the subtropics near 300nkm in 2003 and 2014 (high solar activity with solar 10.7ncm flux, F10.7n≈n140nsolar flux unit (sfu)) were 3 times higher than that in 2009 (low solar activity F10.7n≈n70nsfu). The higher density is attributed to the elevated solar extreme ultraviolet and geomagnetic activity during high solar activity periods. The location of the EIA crests moved ~50nkm upward and ~10° poleward, because of the enhanced En×nB force. The EIA in the northern hemisphere was more pronounced than that in the southern hemisphere. This interhemispheric asymmetry is consistent with the effect of enhanced transequatorial neutral wind. The above observations were reproduced qualitatively by the two benchmark runs of the Thermosphere-Ionosphere-Electrodynamics General Circulation Model. In addition, we have studied the impact of the 11nyear solar cycle on the 27nday solar cycle response of the ionospheric electron density. Beside the expected modulation on the amplitude of the 27nday solar variation due to the 11nyear solar cycle, we find that the altitude of the maximal 27nday solar response is unexpectedly ~50nkm higher than that of the 11nyear solar response. This is the first time that a vertical dependence of the solar responses on different time scales is reported.

Accurate projection of CO2 concentration in time and space remains challenging because of complex interplay between anthropogenic emissions, biospheric responses, and climatic variabilities. While the increase of atmospheric CO2 concentration is due primarily to fossil fuel burning, natural climate variabilities are known to introduce intermittent changes in the global CO2 growth rates. Thus, understanding the correlation of climate and carbon cycling systems is important in assessing the anthropogenic and natural impacts. Here, we report decadal CO2 variabilities in western Pacific based on data from several ground-based stations in the region and Atmospheric Infrared Sounder (AIRS). In addition to the well-established El Nino–Southern Oscillation (ENSO), there exists a decadal changing CO2 trend in the datasets mentioned above. Analysis of ground-based CO2 measurements in northern Taiwan shows a decadal signal at amplitudes of ~5 ppm. In contrast, AIRS shows a similar trend but at a reduced amplitude of ~1 ppm. We attribute the decadal signal to dynamical factors related to the Pacific Decadal Oscillation (PDO). This decadal signal, however, is not reproduced by the state-of-the-art data assimilation system, CarbonTacker, suggesting a gap in our knowledge of the modulation of carbon cycling systems and climate.

The abundance variations of near surface atmospheric CO2 isotopologues (primarily 16O12C16O, 16O13C16O, 17O12C16O, and 18O12C16O) represent an integrated signal from anthropogenic/biogeochemical processes, including fossil fuel burning, biospheric photosynthesis and respiration, hydrospheric isotope exchange with water, and stratospheric photochemistry. Oxygen isotopes, in particular, are affected by the carbon and water cycles. Being a useful tracer that directly probes governing processes in CO2 biogeochemical cycles, Δ17O (=ln(1 + δ17O) − 0.516 × ln(1 + δ18O)) provides an alternative constraint on the strengths of the associated cycles involving CO2. Here, we analyze Δ17O data from four places (Taipei, Taiwan; South China Sea; La Jolla, United States; Jerusalem, Israel) in the northern hemisphere (with a total of 455 measurements) and find a rather narrow range (0.326 ± 0.005‰). A conservative estimate places a lower limit of 345 ± 70 PgC year−1 on the cycling flux between the terrestrial biosphere and atmosphere and infers a residence time of CO2 of 1.9 ± 0.3 years (upper limit) in the atmosphere. A Monte Carlo simulation that takes various plant uptake scenarios into account yields a terrestrial gross primary productivity of 120 ± 30 PgC year−1 and soil invasion of 110 ± 30 PgC year−1, providing a quantitative assessment utilizing the oxygen isotope anomaly for quantifying CO2 cycling.

New Horizons has granted us an unprecedented glimpse at the structure and composition of Pluto's atmosphere, which is comprised mostly of N_2 with trace amounts of CH_4, CO, and the photochemical products thereof. Through photochemistry, higher-order hydrocarbons are generated, coagulating into aerosols and resulting in global haze layers. Here we present a state-of-the-art photochemical model for Pluto's atmosphere to explain the abundance profiles of CH_4, C_2H_2, C_2H_4, and C_2H_6, the total column density of HCN, and to predict the abundance profiles of oxygen-bearing species. The CH_4 profile can be best matched by taking a constant-with-altitude eddy diffusion coefficient K_(zz) profile of 1 × 10^3 cm^2 s^(–1) and a fixed CH_4 surface mixing ratio of 4 × 10^(–3). Condensation is key to fitting the C_2 hydrocarbon profiles. We find that C_2H_4 must have a much lower saturation vapor pressure than predicted by extrapolations of laboratory measurements to Pluto temperatures. We also find best-fit values for the sticking coefficients of C_2H_2, C_2H_4, C_2H_6, and HCN. The top three precipitating species are C_2H_2, C_2H_4, and C_2H_6, with precipitation rates of 179, 95, and 62 g cm^(–2) s^(–1), respectively.

Continuous measurements of isotopic ratios in atmospheric water vapor in a western Pacific region (Taipei, Taiwan) in two winters (2011 and 2012) were made and analyzed to understand the moisture source characteristics. In wintertime, the so-called East Asian Monsoon dominates, largely affecting the climate and meteorology of this region. Being located in the subtropical region, Taipei provides an ideal opportunity for studying interactions between high latitude cold and dry continental air masses and low to mid-latitude warm and wet oceanic air. Indeed, the dual isotope function, d-excess shows the presence of two distinct moisture sources, contributing to the winter vapor isotope variability. Undoubtedly, the dominant moisture source is the high latitude continental cold air masses reaching Taipei with d-excess values of >20‰. Alongside, wet and warm air masses characterized by strong air-sea interaction from the surrounding oceans, possessing d-excess value of ∼10‰ also play a role. The interactions of these two distinct air masses cause the d-excess values to change by as much as ∼20‰ in a few days. Multiple regression analysis shows that source moisture composition and water vapor mixing ratio combined control over 60% of the observed variability. We developed a box model to show that both high and low d-excess events in the winter are primarily controlled by the humidity deficit over the ocean. The information obtained in this study could be used in interpreting the paleoclimate proxies within the East Asian region.

The importance of Asian countries towards increase of atmospheric pollutants is being examined critically in recent times. In this context, we carried out analysis of nitrates separated from aerosol samples collected during 2010 from Mt. Lulin (NOAA code: LLN), Taiwan, located at an altitude of 2 862 m above sea level. Large temporal variations are seen in δ15N, δ18O and Δ17O values of the nitrate, with day-to-day variations comparable to the seasonal amplitude. The δ15N values of nitrate are found to be higher in spring months (March–April; −1±3‰) and lower in summer (June–September; −5±3‰). Similarly, the δ18O (69 ± 15‰ versus 32 ± 13‰) and Δ17O (23 ± 5‰ versus 12 ± 4‰) values are higher in spring and lower in summer. The lowest δ18O value observed was 10.8‰. The higher values of δ15N in spring could be attributed to enhanced contribution from fossil fuel combustions, especially burning of coal in nearby Asian countries like China, with the resultant pollutants being brought to the Lulin station by long-range transport. An alternative explanation is the isotopic exchange reaction between N2O5 and HNO3 that elevates the δ15N value in nitrate. The oxygen isotope variability is explained by changes in contribution from two major pathways of nitrate formation from its precursor NOx molecules. During spring time, nitrate formation via the N2O5 pathway is dominant, resulting in higher values of both δ18O and Δ17O. In contrast, during summer, formation involving HO2/RO2 radicals becomes important, producing lower values of δ18O and Δ17O. A chemistry box model was used to study the nitrate formation pathways through oxidation of NO and NO2 via formation of NO2 and NO3−/HNO3. Both the model results and observations suggest that for the formation of NO2 from NO, the pathway via O3 is more active in spring, whereas in summer the pathway via HO2/RO2 radicals predominates. For the subsequent formation of NO3− and HNO3, the OH pathway is more active in summer than in spring. These suggestions are supported by a wind rose diagram and back trajectory analysis of air masses bringing the precursor NOx to the sampling site.