GEOCHEMISTRY OF METALS AND NUTRIENTS IN FINE-SEDIMENT PORE WATER IN BLACKTAIL AND SILVER BOW CREEKS, BUTTE, MONTANA

Historical mining in Butte, Montana has impacted surface and groundwater in the area. Although most of the known sources of contaminants of concern have been removed or remediated, metal loading continues to occur in lower Blacktail Creek and upper Silver Bow Creek. Possible sources of metals include upwelling groundwater and interaction between the stream and metal-rich sediment in the stream bed. To assess the importance of fine sediment as a source (or sink) for metals, this investigation used sediment pore water diffusion samplers (“peepers”). Peepers are ideal for capturing cm-scale vertical gradients in pore water chemistry across the sediment-water interface. Eight peepers were deployed in Blacktail Creek, six in Silver Bow Creek, one in Grove Gulch, and two in shallow ponds south of lower Blacktail Creek. Four piezometers were also installed in the ponds. Pore-water samples extracted from the peepers and piezometers were analyzed for dissolved trace metals, major ions, alkalinity, and selected nutrients. Sediment samples collected at some peeper sites were analyzed by X-ray diffraction and handheld X-ray fluorescence. Dissolved Fe, Mn, As, PO43-, and HCO3- ions generally increased with depth below the sediment-water interface. Pore-water concentrations of up to 609 mg/L Fe, 55 mg/L Mn, and 1.0 mg/L As were measured at depth. These increases in concentration were attributed to reductive dissolution of Fe- and Mn-oxides, coupled to organic matter decay, in the anoxic environment of the fine-grained sediment. Dissolved Fe2+ could then reprecipitate as Fe-oxides once it reached an aerobic environment and potentially reabsorb dissolved As. PO43- and HCO3- concentrations could also be influenced by sulfate reducing bacteria and oxidation of organic matter. Copper, lead, and zinc behaved differently, and generally had very low concentrations in the deeper samples. Bacterial sulfate reduction was indicated by trace levels of H2S, enough to precipitate Cu, Pb and Zn as sulfide minerals. In some cases, there was a zone where dissolved Cu and Zn concentrations increased sharply in the top 2–6 cm of the sediment column. This could indicate oxidation of fine-grained sulfide minerals in the near-surface pore water. Fick’s first law was used to quantify the diffusive flux of dissolved arsenic from the sediment pore water into Silver Bow and Blacktail Creeks. The same approach was use to estimate downwards diffusion of dissolved Zn from Grove Gulch into its own sediment. The calculated fluxes are negligible for the streams due to the short residence time of water passing through Lower Area One. However, upwards diffusion of As into the shallow ponds could lead to a build-up in dissolved As over time. Although the stream sediments act as a temporary metal sink, the fine sediments are eventually dispersed back into the main stream during periods of high streamflow and bioturbation. Periodic removal of these fine-grained sediments from the stream channels would reduce the total load of metals flowing down Silver Bow Creek

Two configurations of the Western Arctic Shelfbreak Current in summer

Author Posting. © American Meteorological Society, 2012. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 42 (2012): 329-351, doi:10.1175/JPO-D-11-026.1.Data from a closely spaced array of moorings situated across the Beaufort Sea shelfbreak at 152°W are used to study the Western Arctic Shelfbreak Current, with emphasis on its configuration during the summer season. Two dynamically distinct states of the current are revealed in the absence of wind, with each lasting approximately one month. The first is a surface-intensified shelfbreak jet transporting warm and buoyant Alaskan Coastal Water in late summer. This is the eastward continuation of the Alaskan Coastal Current. It is both baroclinically and barotropically unstable and hence capable of forming the surface-intensified warm-core eddies observed in the southern Beaufort Sea. The second configuration, present during early summer, is a bottom-intensified shelfbreak current advecting weakly stratified Chukchi Summer Water. It is baroclinically unstable and likely forms the middepth warm-core eddies present in the interior basin. The mesoscale instabilities extract energy from the mean flow such that the surface-intensified jet should spin down over an e-folding distance of 300 km beyond the array site, whereas the bottom-intensified configuration should decay within 150 km. This implies that Pacific Summer Water does not extend far into the Canadian Beaufort Sea as a well-defined shelfbreak current. In contrast, the Pacific Winter Water configuration of the shelfbreak jet is estimated to decay over a much greater distance of approximately 1400 km, implying that it should reach the first entrance to the Canadian Arctic Archipelago.This work was supported by National Science Foundation GrantsOCE-0726640,OPP-0731928, and OPP-0713250.2012-09-0

A New Methodology for Determining Possible Hatching Events Within Sphereoolithus Eggs

The Zhejiang province of China has provided an astounding amount of dinosaur eggs. The Museum of Natural History in Hangzhou houses over 1,000 of these mid- Cretaceous eggs. There has been extensive debate over whether eggs exhibiting circular openings represent a hatching event, predation, or breakage and crushing due to burial or more recent weathering. Using a new method, we suggest that eggs with openings valued at ≥ the modeled value are possible hatching events. We examined 38 Sphereoolithus eggs chosen based on three factors: (1)the observation of gleying inside the opening must not be attached to the primary shell structure, (2)the opening had to be observed within the least deformed hemisphere, and (3) it had to have clear and measurable axes in three dimensions. Using calipers, we measured the eggs’ lengths, widths, and heights, as well as the widest and longest points of the openings. This data was used to find the potential volume of the egg and the opening size. For this, we utilized a series of previously published equations, which allowed us to determine the eggs’ volume, potential fetus size, and the minimum burrowing capacity. We compared our modeled results to our measured results and found 14 of the 38 eggs we studied fell within the predicted model. To our knowledge, this system of modeling egg-hatching openings is the first of its kind. This method could help in distinguishing dinosaur eggs that are hatched from those eggs that are crushed by natural causes or suffer predation. This could also help identify the original position of the eggs, which is important in a region such as Zhejiang where fossil eggs are often sold to museums by the public, creating a gap in stratigraphic and sedimentological data

Geochemical Analysis of the Marginal Facies of the Bear Gulch Limestone, Central Montana

There are a limited number of late Mississippian age deposits with soft bodied preservation like the Bear Gulch Limestone (BGL) in central Montana to study the End Mississippian mass extinction, the Serpukhovian Biodiversity Crisis. Understanding units like the BGL might illuminate this important time period, and expand our understanding of current global climate change. Geochemical techniques never before applied to the BGL, have provided data that can be used reconstruct the paleoenironment of this fossil-bearing formation. The BGL holds an abundance of well-preserved soft-body fossils from the late Mississippian, including carbon films of organs, worms, and fish. The depositional setting is a restricted marine basin containing five biologic and lithological facies. The marginal facies within the study area is composed of three meters of dark brown fissile laminae. During the summer of 2012 a 220 cm2 area of 50 successive layers of the marginal facies was excavated. The fossils in each layer were compared to literature for species identification. Of the 50 samples, ten fossil bearing samples were selected for geochemical and mineralogical analysis. The samples were ground to 150 microns and examined using X-ray diffraction (XRD), coulometry, and the ferrozine method. XRD provides basic analysis of the mineralogy, used to assist in lithology identification. Coulometry measures total organic carbon content (TOC). TOC is used to assess the potential for petroleum and productivity of the basin. The TOC ranged from 0.72 to 4.17%. The ferrozine method provides data for the determination of the depositional setting. Our initial research has provided a series of methods that can be adapted for the study of additional BGL facies

Tropical field stations yield high conservation return on investment

Conservation funding is currently limited; cost-effective conservation solutions are essential. We suggest that the thousands of field stations worldwide can play key roles at the frontline of biodiversity conservation and have high intrinsic value. We assessed field stations’ conservation return on investment and explored the impact of COVID-19. We surveyed leaders of field stations across tropical regions that host primate research; 157 field stations in 56 countries responded. Respondents reported improved habitat quality and reduced hunting rates at over 80% of field stations and lower operational costs per km2 than protected areas, yet half of those surveyed have less funding now than in 2019. Spatial analyses support field station presence as reducing deforestation. These ‘earth observatories’ provide a high return on investment; we advocate for increased support of field station programs and for governments to support their vital conservation efforts by investing accordingly