Soil-Landscape relationships at the lower reaches of a watershed at Bear Creek near Oak Ridge, Tennessee

The watersheds at Bear Creek, Oak Ridge, TN, have similar soil–landscape relationships. The lower reaches of many of these watersheds consist of headwater riparian wetlands situated between sloping non-wetland upland zones. The objectives of this study are to examine the effects of (i) slope and geomorphic processes, (ii) human impacts, and (iii) particular characteristics of soils and saprolite that may effect drainage and water movement in the wetlands and adjacent landscapes in one of these watersheds. A transect was run from west to east in a hydrological monitored area at the lower reaches of a watershed on Bear Creek. This transect extended from a steep side slope position across a floodplain, a terrace, and a shoulder slope. On the upland positions of the Nolichucky Shale, mass wasting, overland flow and soil creep currently inhibit soil formation on the steep side slope position where a Typic Dystrudept is present, while soil stability on the shoulder slope has resulted in the formation of a well-developed Typic Hapludult. In these soils, argillic horizons occur above C horizons on less sloping gradients in comparison to steeper slopes, which have Bw horizons over Cr (saprolite) material. A riparian wetland area occupies the floodplain section, where a Typic Endoaquept is characterized by poorly drained conditions that led to the development of redoximorphic features (mottling), gleying, organic matter accumulation, and minimal development of subsurface horizons. A thin colluvial deposit overlies a thick well developed Aquic Hapludalf that formed in alluvial sediments on the terrace position. The colluvial deposit from the adjacent shoulder slope is thought to result from soil creep and anthropogenic erosion caused by past cultivation practices. Runoff from the adjacent sloping landscape and groundwater from the adjacent wetland area perhaps contribute to the somewhat poorly drained conditions of this profile. Perched watertables occur in upland positions due to dense saprolite and clay plugging in the shallow zones of the saprolite. However, no redoximorphic features are observed in the soil on the side slope due to high runoff. Remnants of the underlying shale saprolite, which occur as small discolored zones resembling mottles, are also present. The soils in the study have a CEC of

Use of particulate surrogates for assessing microbial mobility in subsurface ecosystems.

Particulate matter can play a vital role in delivering nutrients and micro organisms to groundwater. This paper uses bacteriophage and microsphere surrogates to study the delivery of particles to the subsurface and demonstrates the potential role that pH and ionic strength can play in limiting particle mobility.

Remote, subsurface detection of the algal toxin domoic acid onboard the Environmental Sample Processor: Assay development and field trials

The ability to detect harmful algal bloom (HAB) species and their toxins in real- or near real-time is a critical need for researchers studying HAB/toxin dynamics, as well as for coastal resource managers charged with monitoring bloom populations in order to mitigate their wide ranging impacts. The Environmental Sample Processor (ESP), a robotic electromechanical/fluidic system, was developed for the autonomous, subsurface application of molecular diagnostic tests and has successfully detected several HAB species using DNA probe arrays during field deployments. Since toxin production and thus the potential for public health and ecosystem effects varies considerably in natural phytoplankton populations, the concurrent detection of HAB species and their toxins onboard the ESP is essential. We describe herein the development of methods for extracting the algal toxin domoic acid (DA) from Pseudonitzschia cells (extraction efficiency >90%) and testing of samples using a competitive ELISA onboard the ESP. The assay detection limit is in the low ng/mL range (in extract), which corresponds to low ng/L levels of DA in seawater for a 0.5 L sample volume acquired by the ESP. We also report the first in situ detection of both a HAB organism (i.e., Pseudo-nitzschia) and its toxin, domoic acid, via the sequential (within 2-3 h) conduct of species- and toxin-specific assays during ESP deployments in Monterey Bay, CA, USA. Efforts are now underway to further refine the assay and conduct additional calibration exercises with the aim of obtaining more reliable, accurate estimates of bloom toxicity and thus their potential impacts. Published by Elsevier B.V.

Hydraulic Subsurface Measurements and Hydrodynamic Modeling as Indicators for Groundwater Flow Systems in the Rotondo Granite, Central Alps (Switzerland)

Regional groundwater flow in high mountainous terrain is governed by a multitude of factors such as geology, topography, recharge conditions, structural elements such as fracturation and regional fault zones as well as man-made underground structures. By means of a numerical groundwater flow model, we consider the impact of deep underground tunnels and of an idealized major fault zone on the groundwater flow systems within the fractured Rotondo granite. The position of the free groundwater table as response to the above subsurface structures and, in particular, with regard to the influence of spatial distributed groundwater recharge rates is addressed. The model results show significant unsaturated zones below the mountain ridges in the study area with a thickness of up to several hundred metres. The subsurface galleries are shown to have a strong effect on the head distribution in the model domain, causing locally a reversal of natural head gradients. With respect to the position of the catchment areas to the tunnel and the corresponding type of recharge source for the tunnel inflows (i.e. glaciers or recent precipitation), as well as water table elevation, the influence of spatial distributed recharge rates is compared to uniform recharge rates. Water table elevations below the well exposed high-relief mountain ridges are observed to be more sensitive to changes in groundwater recharge rates and permeability than below ridges with less topographic relief. In the conceptual framework of the numerical simulations, the model fault zone has less influence on the groundwater table position, but more importantly acts as fast flow path for recharge from glaciated areas towards the subsurface galleries. This is in agreement with a previous study, where the imprint of glacial recharge was observed in the environmental isotope composition of groundwater sampled in the subsurface galleries. Copyright © 2012 John Wiley & Sons, Ltd.