Geology topics

Denise Akob

Publications and source records attributed to Denise Akob.

3 recordsLinked to original sources

USGS2019

Microbial Fe(II) oxidation by Sideroxydans lithotrophicus ES-1 in the presence of Schlöppnerbrunnen fen derived humic acids

Controlled laboratory experiments were combined with field measurements to better understand the interactions between dissolved organic matter (DOM) and reduced iron in organic-rich peatlands. Addition of peat-derived humic acid extract (HA) to Sideroxydans lithotrophicus ES-1 liquid cultures led to higher cell numbers and up to 1.4 times higher Fe(II) oxidation rates compared to chemical controls. This effect was positively correlated with increasing HA concentrations. Similar Fe(III) (oxyhydr)oxide mineralogies were formed both abiotically and biotically irrespective of HA amendment, but minerals formed in the presence of ES-1 and HA were smaller. ES-1 growth with HA promoted aggregation of Fe(III) products in agarose-stabilized gradient tubes as shown by voltammetric profiling. In situ voltammetry in an acidic, iron-rich peatland revealed a gap between oxygen penetration and iron reduction that may reflect active Fe(II)-oxidizing microorganisms. The highest abundance of Fe(II) oxidizers Sideroxydans (4.9 x 107 gene copies gww-1) and Gallionella (1.5 x 107 gene copies gww-1) in the upper peat layer coincided with small-sized minerals resembling nanoparticulate ferrihydrite or goethite. Our results suggest that microbially-mediated Fe(II) oxidation dominates in the presence of DOM leading to the formation of nano-sized biogenic Fe(III) (oxyhydr)oxides that might be are readily bioavailable and likely important to iron and carbon cycling.

FEMS Microbiology Ecology↗

USGS2019

Use of high-throughput screening results to prioritize chemicals for potential adverse biological effects within a West Virginia Watershed

Organic chemicals from industrial, agricultural, and residential activities can enter surface waters through regulated and unregulated discharges, combined sewer overflows, stormwater runoff, accidental spills, and leaking septic-conveyance systems on a daily basis. The impact of point and nonpoint contaminant sources can result in adverse biological effects for organisms living in or near surface waters. Assessing the adverse or toxic effects that may result when exposure occurs is complicated by the fact that many commonly used chemicals lack toxicity information or water quality standards. To address these challenges, an exposure-activity ratio (EAR) screening approach was used to prioritize environmental chemistry data in a West Virginia watershed (Wolf Creek). Wolf Creek is a drinking water source and recreation resource with documented water quality impacts from point and nonpoint sources. The EAR screening approach uses high-throughput screening (HTS) data from ToxCast as a method of integrating environmental chemical occurrence and biological effects data. Using water quality schedule 4433, which targets 69 organic waste compounds typically found in domestic and industrial wastewater, chemicals were screened for potential adverse biological affects at multiple sites in the Wolf Creek watershed. Cumulative EAR mixture values were greatest at Sites 2 and 3, where bisphenol A (BPA) and pentachlorophenol exhibited maximum EAR values of 0.05 and 0.002, respectively. Site 2 is downstream of an unconventional oil and gas (UOG) wastewater disposal facility with documented water quality impacts. Low-level organic contaminants were found at all sample sites in Wolf Creek, except Site 10, where Wolf Creek enters the New River. The application of an EAR screening approach allowed our study to extend beyond traditional environmental monitoring methods to identify multiple sites and chemicals that warrant further investigation.

West Virginia↗

USGS2008

Standards and specifications for the calibration and stability of amateur digital cameras for close-range mapping applications

Photogrammetry is concerned with the accurate derivation of spatial and descriptive information from imagery that can be used in several applications such as mapping, DEM generation, orthophoto production, construction planning, environmental monitoring, structural analysis, 3D visualization, and change detection. The type of cameras traditionally used for high accuracy projects were large format analogue cameras. In recent years, however, the use of digital cameras for photogrammetric purposes has become more prevalent. The switch by some users from analogue to digital cameras has been fuelled by the ease of use, decreasing cost, and increasing resolution of digital cameras. Digital photogrammetric cameras can be classified into several categories: line cameras (e.g., ADS40 from Leica Geosystems), large format frame cameras (e.g., DMC TM from Zeiss/Intergraph), and medium to small-format digital cameras. More recently, amateur medium-format digital cameras (MFDC) and small-format digital cameras (SFDC) are being used in photogrammetric activities (e.g., in conjunction with LiDAR systems, smaller flight blocks, and for close-range photogrammetric applications). The continuing development in the capabilities of digital photogrammetry coupled with users’ needs has spawned new markets in photogrammetric mapping with amateur digital cameras. With the wide spectrum of designs for amateur digital cameras, several issues have surfaced, including the method and quality of camera calibration, as well as long-term stability. This paper addresses these concerns and outlines possible solutions. First, we will start by introducing an automated methodology for an in-door camera calibration. The main objective of such a procedure is to provide mapping companies using these cameras with a simple calibration procedure that requires an easy-to-establish test field. The paper will then discuss the concept of how to evaluate camera stability, which will be followed by the introduction of a set of tools for its evaluation. Following the discussion on calibration and stability analysis, the paper will deal with several related questions: How to develop meaningful standards for evaluating the outcome from the calibration procedure; How to develop meaningful standards for evaluating the stability of the involved camera; Is there a flexibility in choosing the stability analysis tool based on the geo-referencing procedure; Can the stability analysis be used for evaluating the equivalency of different distortion models. Finally, experimental results are then provided for two small format digital cameras.

Conference Paper↗