Metal contamination and filtering in soil from an iron (magnetite) mine–smelter complex in the critical Hudson Highlands watershed,New York

Organic material in metal contaminated soils around an abandoned magnetite mine–smelter complex in the critical Highlands watershed protects the groundwater and surface water from contamination. Metals in these waters were consistently below local and national water standards. Two groups of soil types cover the area: (1) Group A disturbed metal-rich soils, and (2) Group B undisturbed organic soils. Chromium and nickel were more elevated than other metals with Cr more widespread than Ni. In Group A, Cr correlated strongly with sesquioxides in the lower horizons (Fe₂O₃: r = 0.74, p < 0.025; Al₂O₃: r = 0.92, p < 0.005). In Group B, Cr correlated strongly (r = 0.96, p < 0.005) with soil organic matter (SOM) in the O-horizons. Ni–Cr (Group A: 52 and 70% in O- and lower horizons, respectively; Group B: ~100% in both horizons) and V–Cr correlations (78% only in Group A lower horizons) suggest similar retention mechanisms for these elements. Average soil \textpH_\textCaCl2 {\text{pH}}_{{{\text{CaCl}}_{2} }} for both groups ranged between 3.65 and 5.91, suggesting that soil acidity is determined by organic acids and solubility of Al³⁺ releasing H⁺ ions. SOM and sesquioxides contribute significantly to creating naturally occurring filtration systems, removing metals, and protecting water quality. High Ca, Fe, and Ti in Group A soils suggest slag and ash were mixed into the soils. Some low-Cr sources include magnetite, slag, and ash (100, 100 and 200 mg/kg, respectively). Constant ZrO ₂ :TiO ₂ ratios in the lower soils indicate soil formation from breakdown of underlying tailing rocks, contributing Cr to these layers.     

Glacial and deglacial climatic patterns in Australia and surrounding regions from 35 000 to 10 000 years ago reconstructed from terrestrial and near-shore proxy data

This study forms part of a wider investigation of late Quaternary environments in the Southern Hemisphere. We here review the terrestrial and near-shore proxy data from Australia, Indonesia, Papua New Guinea (PNG), New Zealand and surrounding oceans during 35–10 ka, an interval spanning the lead-up to the Last Glacial Maximum (LGM), the LGM proper (21 ± 2 ka), and the ensuing deglaciation. Sites selected for detailed discussion have a continuous or near continuous sedimentary record for this time interval, a stratigraphically consistent chronology, and one or more sources of proxy climatic data. Tropical Australia, Indonesia and PNG had LGM mean annual temperatures 3–7 °C below present values and summer precipitation reduced by at least 30%, consistent with a weaker summer monsoon and a northward displacement of the Intertropical Convergence Zone. The summer monsoon was re-established in northwest Australia by 14 ka. Precipitation in northeast Australia was reduced to less than 50% of present values until warmer and wetter conditions resumed at 17–16 ka, followed by a second warmer, wetter phase at 15–14 ka. LGM temperatures were up to 8 °C lower than today in mainland southeast Australia and up to 4 °C cooler in Tasmania. Winter rainfall was much reduced throughout much of southern Australia although periodic extreme flood events are evident in the fluvial record. Glacial advances in southeast Australia are dated to 32 ± 2.5, 19.1 ± 1.6 and 16.8 ± 1.4 ka, with periglacial activity concentrated towards 23–16 ka. Deglaciation was rapid in the Snowy Mountains, which were ice-free by 15.8 ka. Minimum effective precipitation in southern Australia was from 14 to 12 ka. In New Zealand the glacial advances date to ～28, 21.5 and 19 ka, with the onset of major cooling at ～28 ka, or well before the LGM. There is no convincing evidence for a Younger Dryas cooling event in or around New Zealand, but there are signs of the Antarctic Cold Reversal in and around New Zealand and off southern Australia. There remain unresolved discrepancies between the climates inferred from pollen and those inferred from the beetle and chironomid fauna at a number of New Zealand sites. One explanation may be that pollen provides a generalised regional climatic signal in contrast to the finer local resolution offered by beetles and chironomids. Sea surface temperatures (SSTs) were up to 5 °C cooler during the LGM with rapid warming after 20 ka to attain present values by 15 ka. The increase in summer monsoonal precipitation at or before 15 ka reflects higher insolation, warmer SSTs and steeper thermal gradients between land and sea. The postglacial increase in winter rainfall in southern Australia is probably related to the southward displacement of the westerlies as SSTs around Antarctica became warmer and the winter pack ice and Antarctic Convergence Zone retreated to the south.     

Groundwater recharge mechanism in an integrated tableland of the Loess Plateau,northern China: insights from environmental tracers

Assessing groundwater recharge characteristics (recharge rate, history, mechanisms (piston and preferential flow)) and groundwater age in arid and semi-arid environments remains a difficult but important research frontier. Such assessments are particularly important when the unsaturated zone (UZ) is thick and the recharge rate is limited. This study combined evaluations of the thick UZ with those of the saturated zone and used multiple tracers, such as Cl, NO₃, Br, ²H, ¹⁸O, ¹³C, ³H and ¹⁴C, to study groundwater recharge characteristics in an integrated loess tableland in the Loess Plateau, China, where precipitation infiltration is the only recharge source for shallow groundwater. The results indicate that diffuse recharge beneath crops, as the main land use of the study area, is 55–71 mm yr^?1 based on the chloride mass balance of soil profiles. The length of time required for annual precipitation to reach the water table is 160–400 yrs. The groundwater is all pre-modern water and paleowater, with corrected ¹⁴C age ranging from 136 to 23,412 yrs. Most of the water that eventually becomes recharge originally infiltrated in July–September. The Cl and NO₃ contents in the upper UZ are considerably higher than those in the deep UZ and shallow groundwater because of recent human activities. The shallow groundwater has not been in hydraulic equilibrium with present near-surface boundary conditions. The homogeneous material of the UZ and relatively old groundwater age imply that piston flow is the dominant recharge mechanism for the shallow groundwater in the tableland.     

Modelling Indonesian rainfall with a coupled regional model

Long-term high-resolution coupled climate model simulations using the Max Planck Institute Regional Climate Model and the Max Planck Institute Ocean Model have been performed with boundary forcings from two reanalyses: firstly from the European Centre for Medium-Range Weather Forecasts, and secondly from the joint reanalysis of the National Centers for Environmental Prediction and the National Center for Atmospheric Research. This study employs a special coupling setup using a regional atmospheric model and a global ocean model. The latter model applies a special conformal grid from a bipolar orthogonal spherical coordinate system, which allows irregular positions of the poles and focuses on the detail over the Maritime Continent. The coupled model was able to simulate stable and realistic rainfall variabilities without flux correction and at two different ocean resolutions. The coupled system is integrated for a period between 1979 and 1993 and the results are then compared to those from uncoupled runs and from observation. The results show improved performance after coupling: a remarkable reduction of overestimated rainfall over the sea for the atmospheric model and of warm SST biases for the ocean model. There is no significant change in rainfall variability at higher ocean model resolution, but the ocean circulation shows less transport variability within the Makassar Strait in comparison to observations. This paper has not been published or considered by any other journal in any language.     

Analytical Solutions for Determination of Non-Steady- State and Steady-State Capture Zones

This paper presents analytical solutions for determining non-steady-state capture zones produced by a single recovery well and steady-state capture zones produced by multiple recovery wells. Analysis of non-steady-slate capture zones is based on the lime-dependent location of caplure zone stagnation points and the geometric similarity between steady-slate and non-steady-state capture zones. The analytical solution of steady-state capture zones is obtained from spatial variations of discharge potential across the capture zone boundary. Both capture zone analyses are based on the assumptions of uniform flow field with a constant hydraulic conductivity, the Dupuit assumption of insignificant vertical flow, a negligible delayed yield, and a fully penetrating well with a constant pumping rate. For a ground water pump-and-trcat remediation program, the pumping rate and well location design variables can be adjusted to ensure containment of the ground water contaminant plume.     

Polarized EXAFS, distance-valence least-squares modeling (DVLS), and quantitative texture analysis approaches to the structural refinement of Garfield nontronite

This paper reports on the new application of polarized extended X-ray absorption fine structure (P-EXAFS) spectroscopy to fine-grained layer silicates taking the Garfield nontronite as a case study. Up to now application of P-EXAFS to structural studies of layer silicates has been restricted to single phyllosilicate crystals (Manceau et al. 1988; Manceau et al. 1990), but we show here that P-EXAFS can rigorously be applied to self-supporting clay films without loss of spatial resolution. The quantitative analysis of P-EXAFS requires however the preparation of highly oriented clay films, the orientation distribution of which can be assessed by texture goniometry. The Fe K-edge linear dichroism measurements were simulated by ab initio EXAFS modeling performed on a nontronite cluster whose structure was refined by distance-valence least-squares calculations. It is shown that ab initio modeling quantitatively accounts for the angular dependence of experimental EXAFS spectra. These calculations allowed for the identification of the fundamental character of single- and multiple-scattering paths of the photoelectron, and the structural interpretation of all spectral features observed up to 6.5?Å for the in-plane and out-of-plane radial structure functions of nontronite. In practice, P-EXAFS measurements allow the determination of the flattening angle of Fe(O,OH)₆ octahedra, cations distribution in the octahedral sheet with an enhanced sensitivity, and differentiation between dioctahedral and trioctahedral structures.     

Ice mass change in Greenland and Antarctica between 1993 and 2013 from satellite gravity measurements

We construct long-term time series of Greenland and Antarctic ice sheet mass change from satellite gravity measurements. A statistical reconstruction approach is developed based on a principal component analysis (PCA) to combine high-resolution spatial modes from the Gravity Recovery and Climate Experiment (GRACE) mission with the gravity information from conventional satellite tracking data. Uncertainties of this reconstruction are rigorously assessed; they include temporal limitations for short GRACE measurements, spatial limitations for the low-resolution conventional tracking data measurements, and limitations of the estimated statistical relationships between low- and high-degree potential coefficients reflected in the PCA modes. Trends of mass variations in Greenland and Antarctica are assessed against a number of previous studies. The resulting time series for Greenland show a higher rate of mass loss than other methods before 2000, while the Antarctic ice sheet appears heavily influenced by interannual variations.