Data Report: Dissolved sulfide concentration and sulfur isotopic composition of sulfide and sulfate in pore waters, ODP Leg 204, Hydrate Ridge and vicinity, Cascadia margin, offshore Oregon

We report dissolved sulfide sulfur concentrations and the sulfur isotopic composition of dissolved sulfat e and sulfide in pore waters from sediments collected during Ocean Drilling Program Leg 204. Porewater sulfate is depleted rapidly as the depth to the sulfate/methane interface (SMI) occurs between 4.5 and 11 meters below seafloor at flank and basin locations. Dissolved sulfide concentration reaches values as high as 11.3 mM in Hole 1251E. Otherwise, peak sulfide concentrations lie between 3.2 and 6.1 mM and occur immediately above the SMI. The sul- fur isotopic composition of interstitial sulfate generally becomes enriched in 34 S with increasing sediment depth. Peak δ34 S-SO4 values occur just above the SMI and reach up to 53.1‰ Vienna Canyon Diablo Troilite (VCDT) in Hole 1247B. δ34 S-Σ HS values generally parallel the trend of δ34 S-SO4 values but are more depleted in 34S relative to sulfate, with values from –12.7‰ to 19.3 ‰ VCDT. Curvilinear sulfate profiles and carbon isotopic composition of total dissolved carbon dioxide at flank and basin sites strongly suggest that sulfate depletion is controlled by oxidation of sedimentary organic matter, despite the presence of methane gas hydrates in underlying sediments. Preliminary data from sulfur species are consistent with this interpretation for Leg 204 sedi- ments at sites not located on or near the crest of Hydrate Ridge

Characteristics and environmental problems of a eutrophic, seasonally-stratified lake, Wilgreen Lake, Madison County, Kentucky

Wilgreen Lake (Madison County, Kentucky) is listed as ‘‘nutrient impaired’’ by the United States Environmental Protection Agency and Commonwealth of Kentucky, and it also experiences high fecal microbe counts that restricts its use. The lake is a typical eutrophic lake, experiencing anoxia and dysoxia in its waters during summer stratification. Human activities in the watershed contribute additional nutrients to the lake that may exacerbate periods of anoxia, so knowing the sources of anthropogenic nutrient inputs to the lake would aid in developing best practices for development of lake shore areas and the watershed. Possible sources include residential fertilizers, cattle waste, and human sewage. High nutrient concentrations within surface waters generally occur only proximal to septic system clusters in the upper reaches of Taylor Fork. Bovine and human fecal microbes enter the lake causing periodic high fecal microbe counts, and are likewise restricted to shallow water areas especially after rain events. The areal distribution of high nutrient and fecal microbe values implicate septic systems as the most likely source of these pollutants, but runoff from pastureland must also contribute nutrients and fecal material. We plan to use additional tracing methods inthe future to determine the main sources of nutrients and fecal microbes

Stressing concepts and teaching in the classroom: A low-technology approach using concept tests and classroom polls

Electronic student response technologies can be used effectively to increase learning in the classroom. Although these systems are not terribly expensive, their purchase may be out of reach for many departments and institutions. Here we model a low-technology approach that stresses active learning, peer teaching, and testing student understanding of key concepts by using think-pair-share sessions and in-class responses to key concept-test questions. Questions used in class are chosen carefully to emphasize a concept essential to understanding some aspect of geoscience in an introductory geology course. Each class involves the introduction of a key concept question or questions followed by: classroom polling by show of hands; a brief, written response defending a student’s choice; discussion between two to three students; and a follow-up poll. This classroom activity is followed by an experiment, discussion, or lecture that demonstrates the question’s correct answer. In an example linking the layering of fluids by density with the layering of the Earth, two concept-test questions demonstrate the effectiveness of these in-class exercises. Polling showed that students increased their understanding of density layering through peer learning by increasing correct responses by 22 to 46%. Moreover, students extrapolated their understanding of density layering from simple fluids to Earth materials in a subsequent exercise when 88 to 100% of students chose the correct answer on first polling. Generally, use of technologies in the classroom is commendable, but is not essential to learning because techniques that highlight active learning and concepts form the core of student learning. Low-technology approaches can provide many of the same learning outcomes and are available to all. Fundamentally, necessary components for student learning require only students, faculty, and viable teaching strategies

Suspended sediment concentration in the Brushy Creek watershed, Kentucky

Suspended sediment concentration (SSC) can be used as a proxy for environmental health of stream water. For example, large sediment loads can cause harm to aquatic life and are a mechanism for introducing and transporting fecal microbes. We measure SSC of the Brushy Creek watershed, located in Rockcastle, Pulaski, and Lincoln Counties, where the Eastern Kentucky Environmental Research Institute (EK-ERI) has been conducting an assessment of the watershed. Two auto sampling units were placed in Brushy Creek to collect water samples for determination of SSC. The units collect samples every 14 hours for a two-week period, then samples are retrieved for analysis, and new sample bottles are loaded into the auto samplers. Sediment sampling has been in progress since January 2011 and will continue until November 2011. We measure sediment transport during dry, wet, and storm periods. Retrieved samples are brought to the laboratory where sediments are filtered and weighed to determine SSC. The SSC data have been evaluated along with records of rainfall events, as recorded by the UK Agriculture weather station located in Somerset, KY. Due to operational difficulties with our water and sediment samplers, we have only collected intermittent data, however, rainfall events seem to be correlated with increased SSC

Thermalisation by a boson bath in a pure state

We consider a quantum system weakly coupled to a large heat bath of harmonic oscillators. It is well known that such a boson bath initially at thermal equilibrium thermalises the system. We show that assuming a priori an equilibrium state is not necessary to obtain the thermalisation of the system. We determine the complete Schr\"odinger time evolution of the subsystem of interest for an initial pure product state of the composite system consisting of the considered system and the bath. We find that the system relaxes into canonical equilibrium for almost all initial pure bath states of macroscopically well-defined energy. The temperature of the system asymptotic thermal state is determined by the energy of the initial bath state as the corresponding microcanonical temperature. Moreover, the time evolution of the system is identical to the one obtained assuming that the boson bath is initially at thermal equilibrium with this temperature. A significant part of our approach is applicable to other baths and we identify the bath features which are requisite for the thermalisation studied

Patterns of heavy metal concentration in core sediments, Wilgreen Lake, Madison County, Kentucky

Elevated levels of cadmium, copper, lead, and nickel were found within the waters of Wilgreen Lake during a preliminary survey in 2007. Accumulation of heavy metals in freshwater systems is a known problem. Heavy metals enter the lake in the dissolved phase or adsorbed onto sediment particles and may be linked to industries within the lake’s watershed. Under certain geochemical conditions such as anoxia, heavy metals may detach from sediment particles and diffuse into overlying lake waters, causing a renewed influx of heavy metals into the ecosystem. We hypothesize that heavy metals should decrease in concentration upcore as a result of improving industrial practices and strengthening of heavy-metal regulations over time. To test our hypothesis, we took 1-meter-long cores of lake sediment in each of the two major tributaries to see if metal concentrations changed with depth. We sub-sampled the core, freeze-dried the samples, and extracted metals from the sediments using hydrogen peroxide and trace-metal-grade nitric acid according to established Environmental Protection Agency (EPA) protocols. Samples were sent to Activation Laboratories and analyzed for a host of metals using ICP/OES. Most trace metals (Sb, As, Cd, Co, Ni, Se, Ag, Tl, Th) showed no patterns with core depth or between tributaries. However, lead increased markedly upcore at both sites, being more concentrated within Taylor Fork sediment by ~30%. We are investigating the possible effect of lithology on heavy metal concentration, in addition to identifying plausible heavy metal sources in each watershed

Preliminary results of a fecal microbe survey in an eutrophic lake, Wilgreen Lake, Madison County, Kentucky

Wilgreen Lake is a small (~14 mi2) eutrophic lake formed by damming several tributary streams to Silver Creek, Madison County, Kentucky. The lake receives runoff from industrial and urban areas (Richmond) that comprise ~10% of the total watershed area; most runoff is from cattle pasture or human developments encircling the lake. Present and past developments are on septic systems, and effluent from these systems is known qualitatively to seep into lake waters. Our research group is currently conducting a study of the lake in order to identify major nutrient sources, and one possible tracer method is to quantitatively assay species-specific microbes in lake waters. In preparation for this effort in the 2007 field season, we sampled lake waters in July and August 2006 to characterize the spatial distribution and abundance of fecal microbes. Sampling stations (15 in number) encompass the lake’s breadth and include samples from not only the trunk of the lake system (where deeper water occurs) but also from 3 tributaries – two of which have possible inputs from septic systems. We use the Colisure method from IDEXX Laboratories to determine the most probable number (MPN) of total coliform and Escherichia coli bacteria. Higher numbers of fecal microbes occur in the two most densely populated tributaries, and we note 14 cases (at 8 sites) where assays exceed maximum standards of the EPA for bathing exposure (200 cfu per 100 mL for total coliform, TC; 235 cfu per 100 mL for E. coli, EC). The trunk locations show low numbers of fecal microbes (TC generally \u3c150 cfu per 100 mL; EC generally \u3c20 cfu per 50 mL) whereas the upper reaches of both Taylor’s Fork and Old Town Branch show higher microbial abundance (TC generally \u3e300 cfu per 100 mL; EC cfu generally \u3e100 per 100 mL). Another tributary stream with no apparent human effluent at present shows much lower fecal microbe abundance. From the data, we infer there is significant input from septic systems into these specific regions of the lake. There are several other sources that must be eliminated as possibilities, but it is likely that the source of these fecal microbes is from septic systems encircling the lake. Substantial residential development is underway around Wilgreen Lake at present, and we intend that 2007 field results inform development practices