B41B-01
Clay-Catalyzed Incorporation of Arsenic to Bioorganic Moities: A Low-Cost Mechanism for Ameliorating As toxicity Aquatic Systems.
A method for ameliorating the toxicity of As has been developed. Succesive methylation of arsenic has been reported to represent an important detoxification pathway in aquatic systems. Clays are natural porous materials bearing high surface areas and interlayer spacing that allows entrapment of small-sized particles. Thus, clays are natural nanomaterials that can serve as efficient catalysts in natural or engineered systems. In this paper we study the kinetics of transformation of inorganic arsenic to arseno-organic complexes as affected by the following clay samples: Montmorillonite [SWy-2] from Crook Country, Wyoming, USA, and Hectorite [SHCa-1] from San Bernardino. Country, California, USA, and Nontronite [NG-1] from Australia. The effect of environmental factors, arsenic inicial concentration and speciation is discussed.
B41B-02
The Environmental Fate and Bioavailability of Arsenic in Cuitzeo, Michoacán, México .
Cuitzeo is located in Central Mexico. The Cuitzeo lake is very low, it has seven islands and a highway four kilometers long that crosses the lake. Detected concentrations of arsenic average 30-40 mg kg-1. In the salted waters a lot of "charal" (a small fish), main ingredient in many regional dishes, and ducks can be found. This study reports the effect of organic matter on As partitioning. Complexation of As with organic biomolecules that may contribute to detoxification pathways in Cuitzeo are discussed.
B41B-03
Investigating the Impact of a Burrowing Shrimp on Biogeochemical Processes and Microbial Communities in a Shallow Lagoon, Catalina Harbor, California, U.S.A.
Understanding the interactions between the activity of macrofauna organisms and the biogeochemistry and microbiology of marine sediments is crucial in evaluating marine ecosystem functioning and nutrient cycling. Burrows built by different organisms often vary in architecture, size, and permanence, making it difficult to extrapolate from one organism to another and from one location to another, the impact that bioturbation or bioirrigation has on the local biogeochemical processes. The overall goal of this study is to combine interdisciplinary approaches to assess the impact of the ghost shrimp Callianassa californiensis, on the biogeochemistry of a shallow lagoon located in Catalina Harbor, California, USA. Field investigations were performed in the lagoon along a transect from the shoreline out to 10 m. The area is bioturbated by Callianassa californiensis with a linear increase in burrows with distance from the shore (R2 = 0.9481). Highest numbers were found at the 10 m distance with approximately 866 burrows m-2. Oxygen penetration depths were determined using Clark-type amperometric microsensors. These measurements were accompanied by detailed analyses of sediment and pore water parameters (porosity, TOC, H2S, NH4+, NO3-, Fe (II)/Fe (III)) by taking sediment cores at 2 m intervals along the transect and slicing these cores in a vertical resolution of 1 cm. Microbial abundances with sediment depth and along the transect were determined by direct counts (AODC) and microbial diversity patterns were analyzed using the molecular finger printing method ARISA (Automated rRNA Intergenic Spacer Analysis). In addition to the field studies, we examined the effects of the shrimp burrows in more detail by using narrow aquaria (40 cm x 15 cm x 5 cm). Each aquarium was filled with sediment collected from the study site, populated by one or two shrimps, and placed in a flowing seawater system. The front walls of the aquaria were perforated with holes in a 1 cm grid that were filled with silicone, which allowed for sampling from the side, directly targeting specific burrow structures. We used three parallel setups, which was ideal for studying the burrow structure (average burrow depth was ~19.5 cm) and recording burrowing activity. Initially, detailed microsensor measurements were performed in vertical profiles in each aquarium but the aquaria also allowed for direct measurements from the side in and around deeper burrow compartments. Subsequently, the aquaria were subsampled in detail for geochemical and microbiological analyses by removing the front wall. The investigations clearly showed that the shrimp not only increased oxygen penetration into the sediment and thus altered the redox conditions throughout the sediment, but there was also a clear impact on microbial abundances and microbial community structures. Investigations are underway to estimate microbial activity increase associated with bioturbation activity (i.e. sulfate reduction, nitrogen fixation, ammonium oxidation).
B41B-04
Validation of MODIS driven clear-sky daytime net radiation over the Korean Peninsula
Net radiation is the balance of the shortwave and longwave radiation in upwelling and downwelling streams, which is the fundamental quantity of energy available at the earth's surface to drive processes of evapotranspiration, air and soil heating, photosynthesis, and energy storage in vegetation. MODIS provides a challenging tool for monitoring net radiation periodically, nearly twice per daytime (i.e. onboard Terra in the morning and onboard Aqua in the afternoon). The reliable MODIS driven estimates are however hindered by multiple error sources, for examples, related to heterogeneous land cover and complex topography. In this study, we utilized MODIS atmospheric and land products as inputs to estimate daytime shortwave, longwave, and net radiations and then, reliability of the radiation estimates and their errors associated with the input variables were evaluated over the Korean Peninsula. Our results indicate that MODIS is applicable to retrieve net radiation and its input variables (i.e. air temperature, vapor pressure, albedo, and shortwave and longwave radiations) with reasonable accuracy. Overall, Aqua MODIS showed better results than Terra MODIS. For examples, net radiation was better estimated at the forest site (root mean square errors (RMSE) of 42 and 38 W/m2 for Terra and Aqua) than the farmland site (88 and 59 W/m2), while accuracy of shortwave radiation was in opposite (RMSEs of 51 and 44 W/m2 for Terra and Aqua at the forest site; 44 and 26 W/m2 at the farmland site). The large error of net radiation at the farmland site was explained by considerable discrepancies in albedo, land surface emmisivity, and land surface temperature, which were closely related to sub-pixel land cover heterogeneity. On the other hand, the large error of solar radiation at the forest site indicates that effects of sub-pixel topographic complexity on direct and diffuse radiations need to be accounted for in complex terrain areas.
B41B-05
Mapping the Distribution of Cloud Forests Using MODIS Imagery
Tropical cloud forests - those forests that are frequently immersed in clouds or otherwise very humid, are
extremely difficult to map from the ground, and are not easily distinguished in satellite imagery from other forest
types, but they have a very different flora and fauna than lowland rainforest. Cloud forests, although found in many
parts of the tropics, have a very restricted vertical extent and thus are also restricted horizontally. As a result, they
are subject to both human disturbance (coffee growing for example) and the effects of possible climate change.
Motivated by a desire to seek meteorological explanations for the distribution of cloud forests, we have begun to
map cloudiness using MODIS Terra and Aqua visible imagery. This imagery, at ~1030 LT and 1330 LT, is an
approximation for mid-day cloudiness. In tropical regions the amount of mid-day cloudiness strongly controls the
shortwave radiation and thus the potential for evaporation (and aridity). We have mapped cloudiness using a
simple algorithm that distinguishes between the cloud-free background brightness and the generally more
reflective clouds to separate clouds from the underlying background.
A major advantage of MODIS imagery over many other sources of satellite imagery is its high spatial resolution
(~250m). This, coupled with precisely navigated images, means that detailed maps of cloudiness can be
produced. The cloudiness maps can then be related to the underlying topography to further refine the location of
the cloud forests. An advantage of this technique is that we are mapping the potential cloud forest, based on
cloudiness, rather than the actual cloud forest, which are commonly based on forest estimates from satellite and
digital elevation data. We do not derive precipitation, only estimates of daytime cloudiness.
Although only a few years of MODIS imagery has been used in our studies, we will show that this is sufficient to
describe the climatology of cloudiness with acceptable accuracy for its intended purposes. Even periods as short
as one month are sufficient for depicting the location of most cloud forest environments. However, we are
proceeding to distinguish different characteristics of cloud forests, depending on the overall frequency of
cloudiness, the seasonality of cloudiness, and the interannual variability of cloudiness.
These results should be useful to those seeking to describe relationships between the physical characteristics of
the cloud forests and their biological environment.
http:www.nssl.noaa.gov/projects/pacs/web/MODIS/
B41B-06
A Novel Finite-Element Based Algorithm for Impedance Tomography of Arbitrarily Shaped Trees
The electrical conductivity provides valuable information about trees due to its strong dependance on water
content and pore fillings.
Hence the impedance tomography is a cheap and non-destructive method for investigating the interior structure
and for monitoring ongoing processes by means of current injection and voltage measurements.
There are different algorithms for reconstructing the conductivity structure, most of them based on circle geometry.
However, the tree shape strongly influences the electric field and may yield misinterpretations.
We present a novel technique that is able to incorporate arbitrary shapes using unstructured triangular meshes.
The field simulation is carried out via the finite element method on two different meshes in order to improve the
efficiency:
The pure geometric effect is calculated once on a highly refined mesh, whereas the simulations in every iteration
are carried out very fast on a quite coarse mesh.
We apply a Gauss-Newton method with smoothness constraints regularization to solve the inverse problem on a
resolution-dependent mesh.
Different examples for impedance tomography are regarded.
For example we are able to detect a hollow core or regions of different stages of foulness.
We show the effect of tree shapes and how a wrong assumption leads to artifacts.
However there might be different reasons for conductive or resistive anomalies.
An additional information can be obtained by using additional data as from seismic velocity derived from acoustic
travel time tomography.
A structural joint inversion enforces structural similarities in both images such that the results are more
significant.
Impedance data can also be measured at different time steps revealing information on the processes.
A so-called reference technique is applied in order to focus on the temporal changes.
We present a 24-hour sequence of data obtained from a lime tree showing how fluid flow changes in the course
of daylight.
http:www.resistivity.net/
B41B-07
A Simple, Buoy Deployable Instrument for Accurate Dissolved Carbon Dioxide and Dissolved Inorganic Carbon Measurements in Freshwater and Marine Ecosystems
The need for better knowledge of (1) the oceanic sink for anthropogenic CO2, (2) the impact of anthropogenic CO2 on the oceanic CaCO3 system and (3) lake and stream metabolism in freshwater ecosystems is driving growing interest in real-time technologies to measure pCO2 and dissolved inorganic carbon (DIC). To be useful, these technologies must meet stringent data quality requirements of marine and freshwater biogeochemical research initiatives such as the Joint Global Ocean Flux Study, the Coral Reef Environmental Observatory Network, the National Ecological Observatory Network, and the Global Lake Ecological Observatory Network. In this presentation, we introduce new methodology and a device for unaccompanied measurement of pCO2 and DIC on research buoys or ocean/freshwater vessels. This small-scale, essentially "plug and play" device (shoe box size) has limited power requirements (≤1.8 amps) for continuous or discontinuous (e.g., one reading per hour) measurements and does not bio-foul. DIC and pCO2 can be measured in sequence using one infrared detector or in parallel using two. The accuracy and precision (<0.15% coefficient of variation) for pCO2 and DIC meet or approximate the data quality requirements for large-scale biogeochemical research initiatives. Training requirements are minimal, providing flexibility for deployments on multiple vessel types. The device works by induction of ebullition. A hydrostatic pressure drop upstream of a pump causes a temporary condition of gas oversaturation. The collection cell downstream of the pump then acts like an overpressurized soda bottle. As pressure is released within the collection cell, the dissolved gas streams passively and reliably into the infrared detector(s), at a nominal rate of 7 mL per minute, carrying CO2 into the cell essentially at its in-situ partial pressure. To measure DIC, a valve allows for the addition of acid to the sampling line upstream of the pump converting all DIC to CO2 prior to reaching the collection cell. With the acid valve on, DIC is measured. With the acid valve off, pCO2 is measured. We will present data illustrating the accuracy and precision of this device in both laboratory and field circumstances. We will also show the unique possibility of coupling not only pCO2 and DIC in one device, but dissolved organic carbon as well.
B41B-08
Transport of Oil-in-Water Emulsions Designed to Deliver Reactive Iron Particles in Porous Media
Treatment of subsurface regions contaminated with DNAPL is a significant challenge to environmental restoration. The focus of remediation has recently shifted from technologies that recover the contamination to technologies that destroy the contamination in situ. One method of in situ contaminant destruction employs nano- or submicron-size particles of reactive iron metal. Application of iron-based destruction technologies is currently limited by poor delivery of the reactive particles (i.e., lack of contact between the iron particles and the DNAPL). Encapsulation of the reactive particles within an oil-in-water emulsion is a novel approach that may facilitate delivery. The goal of this project was to investigate the transport behavior of emulsions (Tallow oil, Tween 80, and Span 80) within porous media. One-dimensional column experiments were conducted to evaluate pore-clogging when emulsions containing encapsulated reactive particles were passed through two homogeneous sands with an order of magnitude difference in intrinsic permeability. In these experiments, passing an emulsion through the sand column (4.8 cm i.d.) at a constant flow rate (0.86 mL/min) increased the hydraulic gradient by a factor of approximately three. The hydraulic gradient in each experiment was observed to stabilize after one pore volume of emulsion. Subsequent flushing with water recovered the initial hydraulic gradient. Together, these observations indicate that conductivity reductions during emulsion flushing were the result of viscosity and not the result of extensive pore-clogging. Analysis of effluent samples confirmed that there was minimal retention of the emulsion within the sand column. Results from these experiments suggest that emulsion encapsulation may be an effective means for transporting reactive iron particles within the subsurface environment.
B41B-09
ELECTROMAGNETIC DETECTION AND DIGITAL VISUALIZATION OF DNAPL CONTAMINANTS IN A TWO-DIMMENSIONAL SOILBED
Uncharacterized underground contamination at hundreds of thousands of sites in the United States poses major risks to public health. Excessive remediation cost of these sites and failure to achieve acceptable clean up levels are attributed to inadequate detection and monitoring of contaminants in underground systems. Electromagnetic technology and imaging systems may offer practical and cost effective technologies to detect and monitor contamination and enhance remediation practices. Cross Well Radar (CWR) is an innovative, semi-noninvasive technique that has proven valuable in detecting changes in electromagnetic properties when materials of different dielectric characteristics are present in underground environments. It may, therefore, serve to locate and monitor contaminants of differing dielectric properties in underground systems. The overall goal of our research is to evaluate the applicability of CWR technologies to detect, image and monitor the distribution of Dense Non-Aqueous Phase Liquids (DNAPLs) under variable saturation and flow conditions. Validation of this technology is conducted through powerful image analysis techniques, which can discriminate between regions of different amounts of contaminants. Experimental work involves placing transmitting and receiving loop antennas in a 2D SoilBED at preset locations, and measuring their transmission and reflection characteristics in the presence and absence of DNAPLs. Simultaneous acquisition of visible images is taken with a camera. The response of the antennas is compared with colorimetric indices developed for different mass concentrations. The indices are obtained through the application of the classification MatLab Toolboxs developed by CenSSIS. A 2D SoilBed system has been developed to evaluate two modes of concurrent detection and monitoring technologies: Cross Well Radar and Image Analysis (IA). Both technologies are applied concurrently in the SoilBed system during DNAPL transport experiments. Variations in electromagnetic (EM) waves are detected in the presence of contaminants, while color images are acquired. EM signal processing and IA algorithms are being developed to establish the relation between electrical soil properties variations and changes spatial and temporal mass of contaminants.