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

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

Sulfur geochemistry and diagenesis in a gas hydrate terrane, Cascadia margin, offshore Oregon: Role of anaerobic methane oxidation

We present sulfide mineral data from south Hydrate Ridge located in a gas hydrate terrane, offshore Oregon. Sulfide sulfur concentration and the isotopic composition of sulfur (d34S) in authigenic sulfide minerals are analyzed from sediment samples collected on Ocean Drilling Project (ODP) Leg 204. Shallow sediment samples (\u3c25 mbsf) assess the relative importance of anaerobic methane oxidation (AMO) as a biogeochemical process, both here and at the Blake Ridge, another well known gas hydrate terrane offshore southeastern United States. Deep samples (\u3e25 mbsf) are used to evaluate sulfur diagenesis and its controls from early Pleistocene to the present. AMO, a microbially-mediated, sulfate-depleting process, creates an environment conducive to interstitial, authigenic sulfide mineral formation. When AMO is an important process, sulfide minerals are likely to be focused near the sulfate-methane interface (SMI) and become more enriched in heavy sulfur (34S). Preliminary data from two of three shallow sites show high authigenic sulfide sulfur levels (0.27 and 0.7 weight percent sulfur) immediately above the SMI compared to lower concentrations (0.12 and 0.41 weight percent sulfur) just below the SMI. The remaining site has no discernable pattern to the vertical distribution of sulfide sulfur concentration, but shows peak amounts of 0.52 weight percent sulfur above the SMI. Based on results from other sites in the region, we hypothesize that peak amounts of sulfide sulfur are likely precipitated due to production via AMO, but that that sulfate reduction of sedimentary organic matter is also responsible for sulfide mineralization within the sediments. The identification and timing of heavy sulfur enrichments (34S) in deep samples may have implications to the recognition of past gas hydrate occurrences and identify periods of significant methane transport

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

Accumulation of heavy metals in ecosystems is a known environmental problem, and several possible industry sources occur within the watershed of Wilgreen Lake, which is fed its two major tributaries, Taylor Fork and Old Town Branch. Elevated levels of cadmium, copper, lead, and nickel were found within the waters of Wilgreen Lake during a preliminary survey in 2007. A possible source of these contaminant occurrences is diffusion from lake sediments, which record past and present activities within their drainage basins. To obtain a history of anthropogenic practices within the drainage basin, we took 1-meter-long cores of lake sediment in each major tributary to see if metal concentrations changed with depth. The cores were taken from prominent levees that are relatively easy to sample and contain thick sediments with a good record of watershed history. 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 U.S. 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, Se, Ag, Tl, Th) show no pattern with core depth or between the Taylor Fork and Old Town Branch coring sites. Moreover, there was no correlation between core lithology and heavy metal content for any of the measured metals. Antimony, cadmium, and thallium show concentrations at or just above the method blank (\u3c0.1 mg/L). Arsenic, cobalt, nickel, selenium, silver, thallium, and thorium show background concentrations of 5, 12, 17, 1.5, \u3c0.1, 1.5, and 6 mg/L, respectively. Chromium, copper, and nickel within the Taylor Fork core respectively increase 43%, 25% and 19% in the upper 10 to 30 cm of the core from deeper baseline values, perhaps due to diagenetic precipitation. Lead increases markedly downcore within Taylor Fork sediments peaking at ~ 53 mg/L, or about 40% above a background concentration of 23 mg/L observed at Old Town Branch. Copper increases slightly downcore with a higher background level at Taylor Fork (18 versus 12 mg/L). Taylor Fork sediments thus display more lead and copper, consistent with industrial sites existing within this tributary’s watershed. These elevated concentrations perhaps reflect industrial releases in the past

Seasonal changes in stratification and oxygen content of a eutrophic lake, Wilgreen Lake, Madison County, Kentucky

Wilgreen Lake (Madison County, Kentucky) is listed by the Environmental Protection Agency as nutrient-impaired. The overabundance of nutrients is likely linked to the land-use practices in this area. Cattle pasture, residential developments served by septic systems, and urban/industrial areas lie in the lake’s watershed. We have studied the lake for two years to characterize its physical and chemical characteristics, and to identify nutrient sources. The 2007 field season began in March and continued through October. We measured temperature and oxygen levels along with other parameters at 1-meter depth intervals at 19 stations distributed along the length of the lake and within its tributaries. Oxygen and temperature values were plotted on lake cross sections to show seasonal changes from March to October. The lake was essentially unstratified in March but was stratified by April. Stratification persisted to the end of the field season in October. The thermocline set up between 3 and 4 meters for the duration of summer with little variation. Peak anoxia occurred in July with anoxic waters spanning about 6 meters to bottom; disoxic waters (up to 2 mL/L oxygen) occurred from the thermocline downward to the anoxic boundary. WilgreenLakeis a typical eutrophic lake. Heating in the spring leads to stratification. Phytoplankton growth in the photic zone yields organic matter to the lake’s lower layer and sediments. Here oxygen demand created by decomposition in both the water column and sediments of the lake causes disoxia and anoxia. Over the past two field seasons we have seen no increase in the amount of anoxic or disoxic waters. One of our aims in measuring the temperature and oxygenation of the lake so thoroughly is to detect any changes in the future. Continued nutrient loading may alter the characteristics of the lake and our study offers an effective comparison point