Evaluation of riverbed magnetic susceptibility for mapping biogeochemical hot spots in groundwater-impacted rivers     

Chen Wang  Martin A. Briggs  Frederick D. Day-Lewis  Lee D. Slater 《水文研究》2021,35(5):e14184

Redox hot spots occurring as metal-rich anoxic groundwater discharges through oxic wetland and river sediments commonly result in the formation of iron (Fe) oxide precipitates. These redox-sensitive precipitates influence the release of nutrients and metals to surface water and can act as ‘contaminant sponges’ by absorbing toxic compounds. We explore the feasibility of a non-invasive, high-resolution magnetic susceptibility (MS) technique to efficiently map the spatial variations of magnetic Fe oxide precipitates in the shallow bed of three rivers impacted by anoxic groundwater discharge. Laboratory analyses on Mashpee River (MA, USA) sediments demonstrate the sensitivity of MS to sediment Fe concentrations. Field surveys in the Mashpee and Quashnet rivers (MA, USA) reveal several discrete high MS zones, which are associated with likely anoxic groundwater discharge as evaluated by riverbed temperature, vertical head gradient, and groundwater chemistry measurements. In the East River (CO, USA), widespread cobbles/rocks exhibit high background MS from geological ferrimagnetic minerals, thereby obscuring the relatively small enhancement of MS from groundwater induced Fe oxide precipitates. Our study suggests that, in settings with low geological sources of magnetic minerals such as lowland rivers and wetlands, MS may serve as a complementary tool to temperature methods for efficiently mapping Fe oxide accumulation zones due to anoxic groundwater discharges that may function as biogeochemical hot spots and water quality control points in gaining systems.  相似文献   

Resistance of Enzymes to Ionizing Radiation under Model Conditions of the Martian Regolith     

Cheptsov  V. S.  Belov  A. A.  Vorobyova  E. A.  Pavlov  A. K.  Tsurkov  D. A.  Frolov  D. A.  Lomasov  V. N.  Chumikov  A. E. 《Solar System Research》2021,55(5):383-388

Solar System Research - Ionizing radiation is one of the main factors that destroy biomolecules in extraterrestrial conditions. The effects of radiation depend on the conditions of the exposure...  相似文献   

New Orbit and Estimate of the Mass of the Star 61 Cygni Based on Observations of it in 1819-2019     

Izmailov  I. S.  Shakht  N. A.  Polyakov  E. V.  Gorshanov  D. L.  Pogodin  M. A. 《Astrophysics》2021,64(2):160-171

Astrophysics - This paper is a continuation of our earlier work devoted to determining the orbit and mass of the star 61 Cyg and the changes in the photometric characteristics of its components....  相似文献   

Growing season evapotranspiration in boreal fens in the Athabasca Oil Sands Region: Variability and environmental controls     

Olena Volik  Eric Kessel  Adam Green  Richard Petrone  Jonathan Price 《水文研究》2021,35(2):e14020

Current efforts to assess changes to the wetland hydrology caused by growing anthropogenic pressures in the Athabasca Oil Sands Region (AOSR) require well-founded spatial and temporal estimates of actual evapotranspiration (ET), which is the dominant component of the water budget in this region. This study assessed growing season (May–September) and peak growing season (July) ET variability at a treed moderate-rich fen and treed poor fen (in 2013–2018), open poor fen (in 2011–2014), and saline fen (in 2015–2018) using eddy covariance technique and a set of complementary environmental data. Seasonal fluctuations in ET were positively related to net radiation, air temperature and vapour pressure deficit and followed trends typical for the Boreal Plains (BP) and AOSR with highest rates in June–July. However, no strong effect of water table position on ET was found. Strong surface control on ET is evident from lower ET values than potential evapotranspiration (PET); the lowest ET/PET was observed at saline fen, followed by open fen, moderately treed fen, and heavily treed fen, suggesting a strong influence of vegetation on water loss. In most years PET exceeded precipitation (P), and positive relations between P/PET and ET were observed with the highest July ET rates occurring under P/PET ~1. However, during months with P/PET > 1, increased P/PET was associated with decreased July ET. With respect to 30-year mean values of air temperature and P in the area, both dry and wet, cool and warm growing seasons (GS) were observed. No clear trends between ET values and GS wetness/coldness were found, but all wet GS were characterized by peak growing seasons with high daily ET variability.  相似文献   

Effectiveness of post-fire salvage logging stream buffer management for hillslope erosion in the U.S. Inland Northwest Mountains     

Peter R. Robichaud  Edwin D. Bone  Sarah A. Lewis  Erin S. Brooks  Robert E. Brown 《水文研究》2021,35(1):e13943

Active wildfire seasons in the western U.S. warrant the evaluation of post-fire forest management strategies. Ground-based salvage logging is often used to recover economic loss of burned timber. In unburned forests, ground-based logging often follows best management practices by leaving undisturbed areas near streams called stream buffers. However, the effectiveness of these buffers has not been tested in a post-wildfire setting. This experiment tested buffer width effectiveness with a novel field-simulated rill experiment using sediment-laden runoff (25 g/L) released over 40 min at evenly timed flow rates (50, 100 and 150 L/min) to measure surface runoff travel length and sediment concentration under unburned and high and low soil burn severity conditions at 2-, 10- and 22-month post-fire. High severity areas 2-month post-fire had rill lengths of up to 100 m. Rill length significantly decreased over time as vegetation regrowth provided ground cover. Sediment concentration and sediment dropout rate also varied significantly by soil burn severity. Sediment concentrations were 19 g/L for the highest flow 2-month post-fire and reduced to 6.9–14 g/L 10-month post-fire due to abundant vegetation recovery. The amount of sediment dropping out of the flow consistently increased over the study period with the low burn severity rate of 1.15 g L⁻¹ m⁻¹ approaching the unburned rate of 1.29 g L⁻¹ m⁻¹ by 2-year post-fire. These results suggest that an often-used standard, 15 m buffer, was sufficient to contain surface runoff and reduce sediment concentration on unburned sites, however buffers on high burn severity sites need to be eight times greater (120 m) immediately after wildfire and four times greater (60 m) 1-year post-fire. Low burn severity areas 1-year post-fire may need to be only twice the width of an unburned buffer (30 m), and 2-year post-fire these could return to unburned widths.  相似文献   

Early Quaternary Age of the Final Stage of Volcanism in the Central Part of the Sredinny Range of Kamchatka (K–Ar Data)     

Pevzner  M. M.  Lebedev  V. A.  Kuscheva  Yu. V.  Volynets  A. O.  Tolstykh  M. L.  Babansky  A. D. 《Doklady Earth Sciences》2020,490(1):1-3

Doklady Earth Sciences - A first set of K–Ar isotopic ages obtained, which allowed to estimate the age of the largest volcanoes of the Anaunsky Dol (3.2, 2.2 and 1.9 Ma) and eruptive centers...  相似文献   

The Natural Resource Management Planning Portal: Perspectives for NRM Planning and Reporting     

Birgita D. Hansen  Peter G. Dahlhaus  Robert G. Milne  Andrew D. MacLeod  Chris Pitfield 《社会与自然资源》2019,32(6):709-719

Natural Resource Management (NRM) is often conducted as a partnership between government and citizens. In Australia, government agencies formulate policy and fund implementation that may be delivered on-ground by community groups (such as Landcare). Since the late 1980s, over AUS$8b of Commonwealth investment has been made in NRM. However, quantitative evidence of environmental improvements is lacking. The NRM Planning Portal has been developed to (1) provide an online spatial information system for sharing Landcare and agency data; and (2) to facilitate NRM priority setting at local and regional planning scales. While the project successfully federates Landcare NRM activity data, challenges included (1) unstructured, non-standardized data, meaning that quantitative reporting against strategic objectives is not currently possible, and (2) a lack of common understanding about the value proposition for adopting the portal approach. Demonstrating the benefit of technology adoption is a key lesson for digital NRM planning.  相似文献   

Coupled Earth’s Thermosohere-Ionosphere Global Dynamics Model     

Dymnikov  V. P.  Kulyamin  D. V.  Ostanin  P. A. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(3):241-252

Izvestiya, Atmospheric and Oceanic Physics - A coupled Earth’s thermosohere-ionosphere global dynamics model (for altitudes of 90–500 km) is presented. This model is based on a...  相似文献   

Algorithm for the Atmospheric Correction of Shortwave Channels of the MSU-MR Radiometer of the Meteor-M No. 2 Satellite     

Kuchma  M. O.  Bloshchinskiy  V. D. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(9):909-915

Izvestiya, Atmospheric and Oceanic Physics - The problem of atmospheric correction for shortwave channels of a multispectral low-resolution scanning radiometer onboard the Meteor-M No. 2 satellite...  相似文献   

Tectonic and Geodynamic Settings of Formation of the Mesozoic Cumulative Dunite–Wehrlite–Olivine Clinopyroxenite—Gabbro Massif in Eastern Chukotka     

Ledneva  G. V.  Bazylev  B. A.  Layer  P.  Kuzmin  D. V.  Kononkova  N. N. 《Geotectonics》2020,54(4):455-476

Geotectonics - The dunite–wehrlite–clinopyroxenite–gabbro massif in Eastern Chukotka, a key object for geodynamic reconstructions of the Vel’may terrane, which represents...  相似文献