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Natural Hazards - Prediction in ungauged basins (PUB) is as crucial as it is challenging. Thus far, there have been abundant regionalization studies on PUB, whereas "regionalization" is...     

Drinking-water treatment,climate change,and childhood gastrointestinal illness projections for northern Wisconsin (USA) communities drinking untreated groundwater

This study examined the relative importance of climate change and drinking-water treatment for gastrointestinal illness incidence in children (age <5 years) from period 2046–2065 compared to 1991–2010. The northern Wisconsin (USA) study focused on municipalities distributing untreated groundwater. A time-series analysis first quantified the observed (1991–2010) precipitation and gastrointestinal illness associations after controlling for seasonality and temporal trends. Precipitation likely transported pathogens into drinking-water sources or into leaking water-distribution networks. Building on observed relationships, the second analysis projected how climate change and drinking-water treatment installation may alter gastrointestinal illness incidence. Future precipitation values were modeled by 13 global climate models and three greenhouse-gas emissions levels. The second analysis was rerun using three pathways: (1) only climate change, (2) climate change and the same slow pace of treatment installation observed over 1991–2010, and (3) climate change and the rapid rate of installation observed over 2011–2016. The results illustrate the risks that climate change presents to small rural groundwater municipalities without drinking water treatment. Climate-change-related seasonal precipitation changes will marginally increase the gastrointestinal illness incidence rate (mean: ～1.5%, range: ?3.6–4.3%). A slow pace of treatment installation somewhat decreased precipitation-associated gastrointestinal illness incidence (mean: ～3.0%, range: 0.2–7.8%) in spite of climate change. The rapid treatment installation rate largely decreases the gastrointestinal illness incidence (mean: ～82.0%, range: 82.0–83.0%).     

Submarine hydrothermal activity and gold-rich mineralization at Brothers Volcano, Kermadec Arc, New Zealand

Brothers volcano, of the Kermadec intraoceanic arc, is host to a hydrothermal system unique among seafloor hydrothermal systems known anywhere in the world. It has two distinct vent fields, known as the NW Caldera and Cone sites, whose geology, permeability, vent fluid compositions, mineralogy, and ore-forming conditions are in stark contrast to each other. The NW Caldera site strikes for ??600?m in a SW?CNE direction with chimneys occurring over a ??145-m depth interval, between ??1,690 and 1,545?m. At least 100 dead and active sulfide chimney spires occur in this field and are typically 2?C3?m in height, with some reaching 6?C7?m. Their ages (at time of sampling) fall broadly into three groups: <4, 23, and 35?years old. The chimneys typically occur near the base of individual fault-controlled benches on the caldera wall, striking in lines orthogonal to the slopes. Rarer are massive sulfide crusts 2?C3?m thick. Two main types of chimney predominate: Cu-rich (up to 28.5?wt.% Cu) and, more commonly, Zn-rich (up to 43.8?wt.% Zn). Geochemical results show that Mo, Bi, Co, Se, Sn, and Au (up to 91?ppm) are correlated with the Cu mineralization, whereas Cd, Hg, Sb, Ag, and As are associated with the dominant Zn-rich mineralization. The Cone site comprises the Upper Cone site atop the summit of the recent (main) dacite cone and the Lower Cone site that straddles the summit of an older, smaller, more degraded dacite cone on the NE flank of the main cone. Huge volumes of diffuse venting are seen at the Lower Cone site, in contrast to venting at both the Upper Cone and NW Caldera sites. Individual vents are marked by low-relief (??0.5?m) mounds comprising predominately native sulfur with bacterial mats. Vent fluids of the NW Caldera field are focused, hot (??300°C), acidic (pH????2.8), metal-rich, and gas-poor. Calculated end-member fluids from NW Caldera vents indicate that phase separation has occurred, with Cl values ranging from 93% to 137% of seawater values. By contrast, vent fluids at the Cone site are diffuse, noticeably cooler (??122°C), more acidic (pH?1.9), metal-poor, and gas-rich. Higher-than-seawater values of SO₄ and Mg in the Cone vent fluids show that these ions are being added to the hydrothermal fluid and are not being depleted via normal water/rock interactions. Iron oxide crusts 3?years in age cover the main cone summit and appear to have formed from Fe-rich brines. Evidence for magmatic contributions to the hydrothermal system at Brothers includes: high concentrations of dissolved CO₂ (e.g., 206?mM/kg at the Cone site); high CO₂/³He; negative ??D and ??¹⁸O_H2O for vent fluids; negative ??³⁴S for sulfides (to ?4.6??), sulfur (to ?10.2??), and ??¹⁵N₂ (to ?3.5??); vent fluid pH values to 1.9; and mineral assemblages common to high-sulfidation systems. Changing physicochemical conditions at the Brothers hydrothermal system, and especially the Cone site, occur over periods of months to hundreds of years, as shown by interlayered Cu?+?Au- and Zn-rich zones in chimneys, variable fluid and isotopic compositions, similar shifts in ³He/⁴He values for both Cone and NW Caldera sites, and overprinting of ??magmatic?? mineral assemblages by water/rock-dominated assemblages. Metals, especially Cu and possibly Au, may be entering the hydrothermal system via the dissolution of metal-rich glasses. They are then transported rapidly up into the system via magmatic volatiles utilizing vertical (??2.5?km long), narrow (??300-m diameter) ??pipes,?? consistent with evidence of vent fluids forming at relatively shallow depths. The NW Caldera and Cone sites are considered to represent stages along a continuum between water/rock- and magmatic/hydrothermal-dominated end-members.     

Pharmaceuticals and Other Organic Waste Water Contaminants Within a Leachate Plume Downgradient of a Municipal Landfill

Ground water samples collected from the Norman Landfill research site in central Oklahoma were analyzed as part of the U.S. Geological Survey (USGS) Toxic Substances Hydrology Program's national reconnaissance of pharmaceuticals and other organic waste water contaminants (OWCs) in ground water. Five sites, four of which are located downgradient of the landfill, were sampled in 2000 and analyzed for 76 OWCs using four research methods developed by the USGS. OWCs were detected in water samples from all of the sites sampled, with 22 of the 76 OWCs being detected at least once. Cholesterol (a plant and animal steroid), was detected at all five sites and was the only compound detected in a well upgradient of the landfill. N,N-diethyltoluamide (DEBT used in insect repellent) and tri(2-chloroethyl) phosphate (fire-retardant) were detected in water samples from all four sites located within the landfill-derived leachate plume. The sites closest to the landfill had more detections and greater concentrations of each of the detected compounds than sites located farther away. Detection of multiple OWCs occurred in the four sites located within the leachate plume, with a minimum of four and a maximum of 17 OWCs detected. Because the landfill was established in the 1920s and closed in 1985, many compounds detected in the leachate plume were likely disposed of decades ago. These results indicate the potential for long-term persistence and transport of some OWCs in ground water.     

Stability of YREE complexes with the trihydroxamate siderophore desferrioxamine B at seawater ionic strength

Organic complexation of yttrium and the rare earth elements (YREEs), although generally believed to be important, is an understudied aspect of YREE solution speciation in the open ocean. We report the first series of stability constants for complexes of YREEs (except Ce and Pm) with the trihydroxamate siderophore desferrioxamine B (DFOB), representing a class of small organic ligands that have an extraordinary selectivity for Fe(III) and are found in surface seawater at low-picomolar concentrations. Constants were measured by potentiometric titration of DFOB (pH 3-10) in the presence of single YREEs, in simple media at seawater ionic strength (NaClO₄ or NaCl, I = 0.7 M). Under these circumstances, the terminal amine of DFOB does not deprotonate. The four acid dissociation constants of the siderophore were determined separately by potentiometric titration of DFOB alone.Values for the bidentate (log β₁), tetradentate (log β₂), and hexadentate (log β₃) complexes of La-Lu range from 4.88 to 6.53, 7.70 to 11.27, and 10.09 to 15.19, respectively, while Y falls between Gd and Tb in each case. Linear free-energy relations of the three stability constants with the first YREE hydrolysis constant, log , yield regression coefficients of >0.97. On the other hand, plots of the constants vs. the radius of the inner hydration sphere display an increasing deviation from linearity for the lightest REEs (La > Pr > Nd). This may signify steric constraints in DFOB folding around bulkier cations, a larger mismatch in coordination number, or a substantial degree of covalence in the YREE-hydroxamate bond.Complexes of the YREEs with DFOB are many orders of magnitude more stable than those with carbonate, the dominant inorganic YREE ligand in seawater. Speciation modeling with MINEQL indicates that, for an average seawater composition, the hexadentate complex could constitute as much as 28% of dissolved Lu at free DFOB concentrations as low as 10⁻¹³ M. Such conditions might occur when DFOB or other siderophores are present in excess over metals for which they have high affinity, like Fe(III) and Co(III), for example during plankton blooms. Even if it turns out that trihydroxamate siderophores are not the dominant organic YREE ligand in seawater, our results establish a benchmark for producing effects on YREE solution speciation comparable to that of DFOB: the free concentration of any weaker organic ligand L must exceed that of DFOB by a factor β₃/_Lβ₁, assuming its first order complex is formed in greatest abundance.     

Surface heat flow and CO2 emissions within the Ohaaki hydrothermal field,Taupo Volcanic Zone,New Zealand

Carbon dioxide emissions and heat flow have been determined from the Ohaaki hydrothermal field, Taupo Volcanic Zone (TVZ), New Zealand following 20 a of production (116 MW_e). Soil CO₂ degassing was quantified with 2663 CO₂ flux measurements using the accumulation chamber method, and 2563 soil temperatures were measured and converted to equivalent heat flow (W m⁻²) using published soil temperature heat flow functions. Both CO₂ flux and heat flow were analysed statistically and then modelled using 500 sequential Gaussian simulations. Forty subsoil CO₂ gas samples were also analysed for stable C isotopes. Following 20 a of production, current CO₂ emissions equated to 111 ± 6.7 T/d. Observed heat flow was 70 ± 6.4 MW, compared with a pre-production value of 122 MW. This 52 MW reduction in surface heat flow is due to production-induced drying up of all alkali–Cl outflows (61.5 MW) and steam-heated pools (8.6 MW) within the Ohaaki West thermal area (OHW). The drying up of all alkali–Cl outflows at Ohaaki means that the soil zone is now the major natural pathway of heat release from the high-temperature reservoir. On the other hand, a net gain in thermal ground heat flow of 18 MW (from 25 MW to 43.3 ± 5 MW) at OHW is associated with permeability increases resulting from surface unit fracturing by production-induced ground subsidence. The Ohaaki East (OHE) thermal area showed no change in distribution of shallow and deep soil temperature contours despite 20 a of production, with an observed heat flow of 26.7 ± 3 MW and a CO₂ emission rate of 39 ± 3 T/d. The negligible change in the thermal status of the OHE thermal area is attributed to the low permeability of the reservoir beneath this area, which has limited production (mass extraction) and sheltered the area from the pressure decline within the main reservoir. Chemistry suggests that although alkali–Cl outflows once contributed significantly to the natural surface heat flow (∼50%) they contributed little (<1%) to pre-production CO₂ emissions due to the loss of >99% of the original CO₂ content due to depressurisation and boiling as the fluids ascended to the surface. Consequently, the soil has persisted as the major (99%) pathway of CO₂ release to the atmosphere from the high temperature reservoir at Ohaaki. The CO₂ flux and heat flow surveys indicate that despite 20 a of production the variability in location, spatial extent and magnitude of CO₂ flux remains consistent with established geochemical and geophysical models of the Ohaaki Field. At both OHW and OHE carbon isotopic analyses of soil gas indicate a two-stage fractionation process for moderate-flux (>60 g m⁻² d⁻¹) sites; boiling during fluid ascent within the underlying reservoir and isotopic enrichment as CO₂ diffuses through porous media of the soil zone. For high-flux sites (>300 g m⁻² d⁻¹), the δ¹³CO₂ signature (−7.4 ± 0.3‰ OHW and −6.5 ± 0.6‰ OHE) is unaffected by near-surface (soil zone) fractionation processes and reflects the composition of the boiled magmatic CO₂ source for each respective upflow. Flux thresholds of <30 g m⁻² d⁻¹ for purely diffusive gas transport, between 30 and 300 g m⁻² d⁻¹ for combined diffusive–advective transport, and ?300 g m⁻² d⁻¹ for purely advective gas transport at Ohaaki were assigned. δ¹³CO₂ values and cumulative probability plots of CO₂ flux data both identified a threshold of ∼15 g m⁻² d⁻¹ by which background (atmospheric and soil respired) CO₂ may be differentiated from hydrothermal CO₂.     

Geochemistry of fluids associated with the 1995–1996 eruption of Mt. Ruapehu, New Zealand: signatures and processes in the magmatic-hydrothermal system

The 1995–1996 eruption of Mt. Ruapehu has provided a number of insights into the geochemical processes operating within the magmatic-hydrothermal system of this volcano. Both pre-eruption degassing of the rising magma and its eventual intrusion into the convective zone of the hydrothermal system beneath the lake were clearly reflected in lake water compositions. The eruptions of September–October 1995 expelled the lake, and provided the first-ever opportunity to characterise gas discharges from this volcano. The fumarolic discharges revealed compositions typical of andesite volcanoes and strong interaction with the enclosing meteoric and hydrothermal system fluids. Some 1.1 MT of SO₂ gas was released from the volcano between September 1995 and December 1996, whereas ca. twice this amount (2.2 MT equivalent SO₂) was erupted as soluble (i.e. leachable) oxyanions of sulphur. Significantly more sulphur was released from the volcano over this period than can be accounted for from the magma volume actually erupted. The evidence suggests that a sizable component of the evolved sulphur was remobilised from the long-lived hydrothermal system within the volcano during the 1995–1996 activity.     

Evolution of a vent-hosted hydrothermal system beneath Ruapehu Crater Lake,New Zealand

A two-year chemical monitoring program of Ruapehu Crater Lake shows that it has evolved considerably since the volcano's more active eruptive periods in the early 1970s. The present pH (20°C) of 0.6 is about one half unit more acid than the baseline values in the 1970s, whereas S/Cl ratios have increased markedly owing in part to declining HCl inputs into the lake, but also to absolute increases in SO₄ levels which now stand at the highest values ever recorded. Increases in K/Mg and Na/Mg ratios over the 20-year period are attributed to hydrothermal reaction processes in the vent which are presently causing dissolution of previously formed alteration phases such as natroalunite. These observations, combined with results of a recent heat budget analysis of the lake, have led to the development of hydrothermal convection model for the upper portion of the vent. Possible vent/lake chemical reaction processes between end member reactants have been modelled with the computer code CHILLER. The results are consistent with the view that variations in lake chemistry, which are initiated by the introduction of fresh magmatic material into the vent, reflect the extent of dissolution reaction progress on the magmatic material and/or its alteration products. The results also provide insights into the role of such vent processes in the formation of high sulfidation-type ore deposits.