William D. Kirkey

Estimating Colloidal Concentration Using Acoustic Backscatter

Interest has grown for using acoustic Doppler current profilers (ADCPs) to measure suspended solids concentrations (SSC) in aqueous environments because of the ability to make simultaneous unobtrusive long-term multipoint measurements with high spatial and temporal resolutions. The acoustic backscatter intensity (ABS) measured by ADCPs is a function of the particle size distribution, concentration, and incident acoustic signal strength and thus provides the theoretical basis for measuring SSC. The applicability of using ABS from a 2400-kHz ADCP to estimate SSC in units of volume concentration over variable particle size distributions is evaluated in a controlled laboratory study. Results from this research show a log-linear relationship between ABS and volume concentrations over variable size distributions. Volume concentrations predicted from the sonar equation using measured ABS and empirically derived response coefficients compare well with the measured concentrations over the full range of concentrations and particle size distributions tested. The ABS response is shown to be linear with the theoretical Rayleigh scattering target strength, calculated from the empirical particle size distribution, and thus explains the observed linearity over a variable particle size distribution. These results indicate that ABS can be used to provide meaningful volume concentration estimates for characteristically variable colloidal suspensions.

Understanding particle-mediated contaminant transport through real-time monitoring

Aquatic particles represent a significant sink for hydrophobic contaminants including Poly-Chlorinated Biphenyls (PCB). The riverbed of the Hudson River near Ft. Edward, New York is contaminated with PCBs due to the discharge of these chemicals from two General Electric Company (GE) capacitor manufacturing plants into the river from approximately 1947 to 1977. The contaminated sediments continue to be an active PCB source to the water column and biota. GE initiated remedial dredging operations in 2009 to remove the contaminated sediments and subsequently reduce PCB concentrations in fish, river water and sediment, and to minimize downstream transport. To meet these objectives, Environmental Protection Agency (EPA) required GE to follow three engineering performance standards (production, re-suspension and residual) during the dredging operation. Data collected from the River and Estuary Observation Network (REON) are presented in this paper to provide evidence of the capability of the observation network in characterizing particle dynamics which can guide in adaptive dredging operation to meet the objectives, and to track the improvements of water quality due to this remediation action. In this study, the particle dynamics at the Thompson Island Pool (TIP), where high PCB concentrations are found in the sediment and biota, were characterized with respect to stream velocity profiles, suspended sediment concentration and particle size distribution during a flood event. This characterization presented sediment resuspension and advection as potential mechanisms for sediment and sediment bound PCBs transport during a flood event. Moreover, integration of the monitoring datasets with the PCB fate and transport model can serve as a valuable diagnostic tool for investigating the impacts of PCB on the ecosystem of the Hudson River.

Development of an in-situ total phosphorus analyzer

A low cost autonomous, in-situ analyzer for orthophosphate and total phosphorus was developed and tested for near real time monitoring in aquatic and marine environments. The system applies the colorimetric stannous chloride-molybdenum blue method following oxidative digestion with acidic peroxodisulfate. A (fluorinated ethylene propylene) FEB tubing reactor coil is wrapped around a germicidal UV (254nm) light to accelerate the digestion reaction. A Nickel chromium wire (NiCr) wound between reactor coil wraps provides controlled heating for digestion. Reactor temperature is monitored continuously with a small temperature probe and controlled with a PID. A sequential injection analysis (SIA) method was chosen where the analyzer operates as a sequential batch reactor. Water sample and reagents are delivered through the microfluidics using syringe pump driven by linear actuators that are controlled with a Teensy microprocessor. To equalize pressures, reagent storage and waste are contained in collapsible reagent bags maintained at hydrostatic pressure outside the submersible housing. Following digestion and colorimetric reactions the sample is transferred to flow cell (5 cm path length) where a photodiode measures sample absorbance at 600 nm. For orthophosphate phosphorus measurements, the sample is not treated with digestion reagents, heat, or UV. Potassium dihydrogen phosphate and adenosine monophosphate (AMP) were used to assess analyzer performance for measuring orthophosphate and total phosphorus, respectively. The prototype analyzer produced a linear response during bench testing to total phosphorus with a precision of ±4.3% over a detection range concentration range of 30-200μg P/L. To evaluate the performance with natural waters, dilutions of algal culture with known phosphorus concentration were measured and found to be within 90% of nominal phosphorus concentrations. A preliminary cost analysis indicates that the operating components of the system (minus submersible housing) can be purchased for under

Estimating sub-surface dispersed oil concentration using acoustic backscatter response

3000 compared to

SENSE IT - student created water quality sensors

30,000 for commercially available systems. At this low cost of construction, this sensor design may be a viable option for use in nutrient monitoring programs. Considering that system components have been designed to withstand internal pressures equivalent to a water depth of 100 m with a designed duty capacity of 2 weeks suggest the possibility of applications in coastal waters and relatively deep lakes.

Large Eddy Simulation of the Flow Field in the Hudson River

The recent Deepwater Horizon disaster resulted in a dispersed oil plume at an approximate depth of 1000 m. Several methods were used to characterize this plume with respect to concentration and spatial extent including surface supported sampling and autonomous underwater vehicles with in situ instrument payloads. Additionally, echo sounders were used to track the plume location, demonstrating the potential for remote detection using acoustic backscatter (ABS). This study evaluated use of an Acoustic Doppler Current Profiler (ADCP) to quantitatively detect oil-droplet suspensions from the ABS response in a controlled laboratory setting. Results from this study showed log-linear ABS responses to oil-droplet volume concentration. However, the inability to reproduce ABS response factors suggests the difficultly in developing meaningful calibration factors for quantitative field analysis. Evaluation of theoretical ABS intensity derived from the particle size distribution provided insight regarding method sensitivity in the presence of interfering ambient particles.

Student enabled water quality sensors

This paper describes the structure and impact of an NSF-funded ITEST project designed to enrich science, technology, engineering, and mathematics (STEM) education using educational modules that teach students to construct, program, and test a series of sensors used to monitor water quality. During the three years of the SENSE IT project, over 60 teachers across New York, New Jersey and Washington were provided with equipment and professional development, and then implemented the modules in their classrooms with over 2,000 middle and high school students. Project evaluation results indicate that the curriculum was well received by teachers and students, could be integrated into several different subject areas and types of courses, and was effective for a wide range of students.

Sense the Hudson - Student developed environmental sensors classroom project

Large-eddy simulation (LES) has been conducted under idealized conditions in two river reaches of the Hudson River (New York, USA), with near-bank resolution set to some 5 meters in order to resolve large-scale motions of turbulence in the near-bank regions. To simplify analysis, simulation is performed at a constant discharge corresponding to a typical ebb tide. A standard Smagorinsky model is implemented in the commercial package FLUENT, with buoyancy neglected and bottom roughness set to zero. We perform Proper Orthogonal Decomposition (POD) on the LES results. POD modes are orthogonal flow fields that capture the kinetic energy in an optimally convergent fashion. Results show that only a few POD modes are enough to describe the most energetic flow dynamics. In a reach around the Indian Point power plant, the second and third modes reflect an interesting generation of separating eddies on the western bank, which we do not find with a URANS (standard k-e) computation on the same grid. To test our simulation, a comparison of simulation results with other simulation results and Acoustic Doppler Current Profiler (ADCP) data measured at West Point, New York will be presented.Copyright

KOOPMAN MODES IN A NEAR-BANK REGION OF A TIDAL RIVER

This paper describes efforts to enrich STEM education by providing classroom projects in which high school students build and deploy sensors for environmental monitoring. Through a series of educational modules, students learn about engineering and science through the design, construction, programming and testing of a student-implemented water monitoring network in the Hudson and St. Lawrence River regions in New York State. This paper provides an overview of the educational modules. A variety of sensors are described, which are suitably simple for design and construction from first principles by high school students while being accurate enough for students to make meaningful environmental measurements. The paper also describes how the sensor building activities can be tied to core curricula, enabling the modules to be utilized in standard classes by mathematics, science and computing teachers without disrupting the semester teaching goals. Furthermore, the paper presents the results of the first two years of the NSF SENSE IT project, during which 37 teachers have been equipped, trained on these materials, and have implement the modules with approximately 500 high school students.

Student-created Water Quality Sensors

Sense the Hudson is an innovative new project which integrates science, technology, engineering and mathematics (STEM) skills into a robust interdisciplinary curricula and teacher development effort in which high school students design, build, test, deploy and interpret their own environmental sensors.