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Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The isotope enabled atmospheric water balance model is applied to examine the spatial and temporal variations of δO in precipitation, amount effect and meteoric water lines (MWL) under four scenarios with different fractionation nature and surface evaporation inputs. The experiments are conducted under the same weather forcing in the framework of the water balance and stable water isotope balance. Globally, the spatial patterns of mean δO and global MWLs simulated by four simulation tests are in reasonably good agreement with the Global Network of Isotopes in Precipitation observations. The results indicate that the assumptions of equilibrium fractionation for simulating spatial distribution in mean annual δO and the global MWL, and kinetic fractionation in simulating δO seasonality are acceptable. In Changsha, four simulation tests all reproduce the observed seasonal variations of δO in precipitation. Compared with equilibrium fractionation, the depleted degree of stable isotopes in precipitation is enhanced under kinetic fractionation, in company with a decrease of isotopic seasonality and inter-event variability. The alteration of stable isotopes in precipitation caused by the seasonal variation of stable isotopes in vapour evaporated from the surface is opposite between cold and warm seasons. Four simulations all produce the amount effect commonly observed in monsoon areas. Under kinetic fractionation, the slope of simulated amount effect is closer to the observed one than other scenarios. The MWL for warm and humid climate in monsoon areas are well simulated too. The slopes and intercepts of the simulated MWLs decrease under kinetic fractionation. [ABSTRACT FROM AUTHOR]

Interannual variability of the atmospheric CO accumulation is at a similar magnitude of decadal average CO accumulation in the atmosphere. Part of observed variability in the atmospheric CO can be interpreted by large-scale climate variability. Teleconnection between the atmospheric CO anomalous tendency and selected large-scale coupled oceanic and atmospheric oscillations (AO, NAO, PDO, IOD, ENSO and SAM) are examined using wavelet-based multi-resolution analysis. The results indicate that all six oscillation indices appear to be associated with monthly CO concentration at most of the 13 examined stations. About 70 % of interannual variability of CO anomalous tendency at Mauna Loa and South Pole can be interpreted by the climatic indices. The temperature effects on the CO anomalous tendency are overall positive. At the monthly scale, they interpret 14 % variability in CO anomalous tendency in 1980-2011. At two high elevation stations (Mauna Loa and South Pole) with large footprints, the teleconnection signal is stronger (interpreting 20 and 25 % variability in monthly CO anomalous tendency, respectively). Including global mean monthly air temperature time series, slightly but significantly in the statistical sense, improves the proportion of monthly CO anomalous tendency being interpreted at most of the examined stations. The signs (positive vs. negative) in the association between monthly CO anomalous tendency and the significant climatic indices appear to reflect physical mechanisms leading to such teleconnections. [ABSTRACT FROM AUTHOR]

In this study, arsenic adsorption to an Australian laterite has been examined for a particle-size range between 38 μm and 25 mm. The results show that particle size influences both kinetic and equilibrium characteristics of arsenic adsorption. The equilibrium adsorption capacity increases from around 100 mg kg for laterite particles coarser than 4 mm, to around 160 mg kg for laterite particles between 75 μm and 4 mm, and to over 200 mg kg for laterite particles finer than 75 μm. The kinetic adsorption data can be fitted with the pseudo-second-order reaction model, in particular for finer particles where the film diffusion and/or surface reaction are important processes. The model-fitted rate constant remains steady for laterite particles coarser than 2 mm, increases moderately with particle size in the range between 75 μm and 2 mm, and increases dramatically for laterite particles finer than 75 μm. These arsenic adsorption behaviours can be explained by the relative importance of two particle-size-dependent processes: quick external-surface adsorption (more important for fine particles) and slow intraparticle adsorption (more important for coarse particles). Most of the external-surface adsorption completes in the first hour of the experiment. To apply the studied laterite for dissolved arsenic removal, it is recommended that fine particles, in particular finer than 75 μm, should be used if the contact time is the limitation, and that coarse particles, in particular 2-4 mm, should be used if sufficient contact time is available. [ABSTRACT FROM AUTHOR]

The spatial and temporal distributions of the stable isotopes such as HDO (or HHO, or HDO) and HO in atmospheric water vapor are related to evaporation in source places, vapor condensation during transport, and vapor convergence and divergence, and thus provide useful information for investigation and understanding of the global water cycle. This paper analyzes spatiotemporal variations of the content of isotope HDO (i.e., δ), in atmospheric water vapor, namely, δ, and the relationship of δ with atmospheric humidity and temperature at different levels in the troposphere, using the HDO and HO data retrieved from the Tropospheric Emission Spectrometer (TES) at seven pressure levels from 825 to 100 hPa. The results indicate that δ has a clear zonal distribution in the troposphere and a good correspondence with atmospheric precipitable water. The results also show that δ decreases logarithmically with atmospheric pressure and presents a decreasing trend from the equator to high latitudes and from lands to oceans. Seasonal changes of δ exhibit regional differences. The spatial distribution and seasonal variation of δ in the low troposphere are consistent with those in the middle troposphere, but opposite situations occur from the upper troposphere to the lower stratosphere. The correlation between δ and temperature has a similar distribution pattern to the correlation between δ and precipitable water in the troposphere. The stable isotope HDO in water vapor ( δ), compared with that in precipitation ( δ), is of some differences in spatial distribution and seasonal variation, and in its relationship with temperature and humidity, indicating that the impacts of stable isotopic fractionation and atmospheric circulation on the two types of stable isotopes are different. [ABSTRACT FROM AUTHOR]

HDS-SPAC, a new soil-plant-atmosphere continuum (SPAC) model, is developed for simulating water and heat transfer in SPAC. The model adopts a recently proposed hybrid dual source approach for soil evaporation and plant transpiration partitioning. For the above-ground part, a layer approach is used to partition available energy and calculate aerodynamic resistances, while a patch approach is used to derive sensible heat and latent heat fluxes from the two sources (soil and vegetation). For the below-ground part, soil water and heat dynamics are described by the mixed form of Richards equation, and the soil heat conductivity equation, respectively. These two parts are coupled through ground heat flux for energy transfer, root-zone water potential-dependent stomatal resistance, and surface soil water potential-dependent evaporation for water transfer. Evaporation is calculated from the water potential gradient at soil-atmosphere interface and aerodynamic resistance, and transpiration is determined using a Jarvis-type function linking soil water availability and atmospheric conditions. Some other processes, such as canopy interception and deep percolation, are also considered in the HDS-SPAC model. The hybrid dual-source approach allows HDS-SPAC to simulate heat and water transfer in an ecosystem with a large range of vegetation cover change temporally or spatially. The model was tested with observations at a wheat field in North China Plain over a time of three months covering both wet and dry conditions. The fractional crop covers change from 30% to over 90%. The results indicated that the HDS-SPAC model can estimate actual evaporation and transpiration partitioning and soil water content and temperature over the whole range of tested vegetation coverage. [ABSTRACT FROM AUTHOR]

A novel heterotrophic-autotrophic denitrification (HAD) approach supported by mixing granulated spongy iron, methanol, and mixed bacteria was proposed for the remediation of nitrate-nitrogen (NO-N) contaminated groundwater in a dissolved oxygen (DO)-rich environment. The HAD process involves biological deoxygenation, chemical reduction (CR) of NO-N and DO, heterotrophic denitrification (HD), and autotrophic denitrification (AD). Batch experiments were performed to: (1) investigate deoxygenation capacities of HAD; (2) determine the contributions of AD, HD, and CR to the overall NO-N removal in the HAD; and (3) evaluate the effects of environmental parameters on the HAD. There were 174, 205, and 2,437 min needed to completely reduce DO by the HAD, spongy iron-based CR, and by the mixed bacteria, respectively. The HAD depended on abiotic and biotic effects to remove DO. CR played a dominant role in deoxygenation in the HAD. After 5 days, approximately 100, 63.0, 20.1, and 9.7 % of the initial NO-N was removed in the HAD, HD, AD + CR, and CR incubations, respectively. CR, HD, and AD all contributed to the overall NO-N removal in the HAD. HD was the most important NO-N degradation mechanism in the HAD. There existed symbiotic, synergistic, and promotive effects of CR, HD, and AD within the HAD. The decrease in NO-N and the production of nitrite-nitrogen (NO-N) and ammonium-nitrogen (NH-N) in the HAD were closely related to the C to N weight ratio. The C to N ratio of 3.75:1 was optimal for complete denitrification. Denitrification rate at 27.5°C was 1.36 times higher than at 15.0°C. [ABSTRACT FROM AUTHOR]

In this paper, we examine the performance of four isotope incorporated GCMs, i.e., ECHAM4 (University of Hamburg), HadCM3 (Hadley Centre), GISS E (Goddard Institute of Space Sciences), and MUGCM (Melbourne University), by comparing the model results with GNIP (Global Network of Isotopes in Precipitation) observations. The spatial distributions of mean annual δD and mean annual deuterium excess d in precipitation, and the relationship between δO and δD in precipitation, are compared between GCMs and GNIP data over East Asia. Overall, the four GCMs reproduce major characteristics of δD in precipitation as observed by GNIP. Among the four models, the results of ECHAM4 and GISS E are more consistent with GNIP observed precipitation δD distribution. The simulated d distributions are less consistent with the GNIP results. This may indicate that kinetic fractionation processes are not appropriately represented in the isotopic schemes of GCMs. The GCM modeled MWL (meteoric water line) slopes are close to the GNIP derived MWL, but the simulated MWL intercepts are significantly overestimated. This supports that the four isotope incorporated GCMs may not represent the kinetic fractionation processes well. In term of LMWLs (local meteoric water lines), the simulated LMWL slopes are similar to those from GNIP observations, but slightly overestimated for most locations. Overall, ECHAM4 has better capability in simulating MWL and LMWLs, followed by GISS E. Some isotopic functions (especially those related to kinetic fractionation) and their parameterizations in GCMs may have caused the discrepancy between the simulated and GNIP observed results. Future work is recommended to improve isotopic function parameterization on the basis of the high-resolution isotope observations. [ABSTRACT FROM AUTHOR]

The efficiency of Australian laterites in arsenic adsorption has been examined using three laterite samples collected from different locations in South Australia. The characteristics such as electrical conductivity, pH, mineral compositions, and isoelectric point of laterite samples have been measured. The laterite samples are mainly composed of iron and aluminum oxides, and rutile (TiO). Two batch experiments have been performed to compare the efficiencies of different laterites to remove AS (III) from water at two different doses, and to examine whether pH influences arsenic adsorption. For 50 mg/l arsenic solution, at doses 1,000 g (laterite)/l (arsenic solution) and 200 g/l, the laterites removed more than 97% and 87-97%, respectively. At the dose of 200 g/l, adsorption capacity has been found to be 200-243 mg/kg. Out of the laterite samples from three localities, the Kangaroo Island laterite performed the best. This is probably related to its high content of gibbsite. It has been found that arsenic adsorption by laterite is not significantly affected at the examined pH ranges of 4.7-10.0. [ABSTRACT FROM AUTHOR]