A wireless sensor system for validation of real-time automatic calibration of groundwater transport models

In this paper, we present the use of a wireless sensor network in a lab for subsurface contaminant plume monitoring with the objective of automatic calibration of groundwater transport models. A tank configured to simulate an aquifer was used as a testbed, and a 2D model was created based on the setup. To simulate a contaminant plume, an ion tracer was injected into the tank. Sensor probes capable of detecting the plume were buried inside the tank, and wireless motes used to take readings from the sensors and relay data to a base station. More importantly, a run-time fault detection and diagnosis for abnormal sensor readings is designed and integrated into the data acquisition system. Further, an adaptive data collection technique is integrated that is able to provide evidence about the effectiveness of the groundwater transport model in use. Results from the tracer tests are presented, as well as lessons gained.     

Outdoor Air Contaminants and Indoor Air Quality under Transient Conditions

The indoor concentrations of contaminants originating from outdoor sources have been measured and calculated under transient conditions. The results show that contaminants that are supplied to an office building via the ventilation system can reach considerably high concentration levels. The indoor/outdoor concentration ratio and time lag are dependent on the air change rate. In buildings with low air change rates the indoor concentration variations are smoothed out compared to buildings with high air change rates. The results from the theoretical model are compared to the results from both laboratory and field measurements and the model is verified for well mixed conditions in a 20 m³ test chamber. The model can be used to simulate different control strategies for reduction of indoor contaminant concentrations related to outdoor sources. One such control strategy is based on reduction of the outdoor air change rate during periods with peak outdoor contaminant concentrations.     

Evaluation and application of anion exchange resins to measure groundwater uranium flux at a former uranium mill site

Laboratory tests and a field validation experiment were performed to evaluate anion exchange resins for uranium sorption and desorption in order to develop a uranium passive flux meter (PFM). The mass of uranium sorbed to the resin and corresponding masses of alcohol tracers eluted over the duration of groundwater installation are then used to determine the groundwater and uranium contaminant fluxes. Laboratory based batch experiments were performed using Purolite A500, Dowex 21K and 21K XLT, Lewatit S6328 A resins and silver impregnated activated carbon to examine uranium sorption and extraction for each material. The Dowex resins had the highest uranium sorption, followed by Lewatit, Purolite and the activated carbon. Recoveries from all ion exchange resins were in the range of 94-99% for aqueous uranium in the environmentally relevant concentration range studied (0.01-200 ppb). Due to the lower price and well-characterized tracer capacity, Lewatit S6328 A was used for field-testing of PFMs at the DOE UMTRA site in Rifle, CO. The effect on the flux measurements of extractant (nitric acid)/resin ratio, and uranium loading were investigated. Higher cumulative uranium fluxes (as seen with concentrations > 1 ug U/gram resin) yielded more homogeneous resin samples versus lower cumulative fluxes (<1 ug U/gram resin), which caused the PFM to have areas of localized concentration of uranium. Resin homogenization and larger volume extractions yield reproducible results for all levels of uranium fluxes. Although PFM design can be improved to measure flux and groundwater flow direction, the current methodology can be applied to uranium transport studies.     

Biological consequences of agricultural and urban land-use along the Maumee River,a major tributary to the Laurentian Great Lakes watershed

Many riverine systems are impacted by a combination of agricultural and urban land use. In this study, we assessed the impacts of high intensity agriculture and urban land use in the Maumee River, the largest Great Lakes tributary, using sunfish (Lepomis spp.). The land use gradient from agricultural headwaters to densely urban areas was hypothesized to be paralleled by a shift in the chemical signature and biological effects. We caged hatchery-reared sunfish at field sites and collected concurrently resident sunfish. We analyzed fish for alterations in morphological indices, hematological characteristics, and anatomical development. Water, sediment, and fish tissues were analyzed for pesticides, pharmaceuticals, and personal care products. Chemicals were detected in all samples, and no clear agricultural/urban distinction in water chemistry was apparent. We detected forty-three chemicals (19% of analyzed) in at least half of the water samples, and 101 chemicals (44%) in at least one water sample. The pesticides desethylatrazine (100% of samples) and heptachlor epoxide (89%), and pharmaceuticals iopamidol (100%) and sulfamethoxazole (89%) were frequently detected. Resident sunfish were more sensitive than caged sunfish, and both experienced elevated stress responses at urban sites. Declining biological indices suggest contaminant-related impairments which may have altered resource allocation and could have contributed to decreased sexual maturity. Agricultural, and especially urban, contaminants entering aquatic ecosystems as non-point sources affect sunfish biology through acute and chronic exposure. Natural resource managers are advised to broadly assess stressors prior to investing into stream restoration efforts.     

Leaching behavior of fly ash-waste glass and fly ash-slag-waste glass-based geopolymers

The leaching behavior of contaminants in the fly ash/waste glass or fly ash/blast furnace slag/waste glass-based geopolymers was investigated through surface area analysis and leaching tests. Spent fluorescent lamps classified as hazardous waste due to their specific contaminant contents were used as a source of waste glass. The results from semi-dynamic leaching tests showed that the mobility of contaminants increases as the amount of waste glass added to the synthesis mixture increases. These results are consistent with those obtained from the surface area analysis. However, the comparative analysis of mobility of contaminants between types of activated mixtures highlighted a different trend of mobility of contaminants to that of pore size distributions. Therefore, the leaching behavior of contaminants suggests that their immobilization in the activated mixtures might occur by both physical and chemical mechanisms. Also, it was emphasized that waste glass is not compliant with respect to its leachable Hg content, and that Hg and Pb exhibit high mobility in the geopolymers with high amount of waste glass added to the synthesis mixtures.     

空气传播分子污染物、源头及监控系统的研究

通过研究某半导体制造工厂应用AMC控制程序的案例,探讨关于AMC控制的具体内容,了解AMC并掌握如何制定正确的AMC评估战略、描述与建立AMC控制原则和规范、理解AMC控制系统的设计理念。     

Dispersal of exhaled air and personal exposure in displacement ventilated rooms

The influence of the human exhalation on flow fields, contaminant distributions, and personal exposure in displacement ventilated rooms is studied together with the effects of physical movement. Experiments are conducted in full-scale test rooms with life-sized breathing thermal manikins. Numerical simulations support the experiments. Air exhaled through the mouth can lock in a thermally stratified layer, if the vertical temperature gradient in breathing zone height is sufficiently large. With exhalation through the nose, exhaled air flows to the upper part of the room. The exhalation flow from both nose and mouth is able to penetrate the breathing zone of another person standing nearby. The stratification of exhaled air breaks down if there is physical movement in the room. As movement increases, the concentration distribution in the room will move towards a fully mixed situation. The protective effect of the boundary layer flow around the body of a moving person disappears at low speed, and is reduced for a seated person placed nearby due to horizontal air movements, which can also cause rebreathing of exhaled air for the seated person. The results indicate that the effect of the exhalation flow is no acute problem in most normal ventilation applications. However, exhalation and local effects caused by movement may be worth considering if one wishes to contain contaminants in certain areas, as in the case of tobacco smoking, in hospitals and clinics, or in certain industries.     

Assessing water quality impacts and cleanup effectiveness in streams dominated by episodic mercury discharges

Accurate pollutant mass budgets are needed for identifying contaminant sources and establishing cleanup goals. We monitored mercury discharges from an abandoned mine site in northern California with the objectives of: (1) estimating the mass loading of mercury from the site; (2) evaluating the factors that control the mercury discharges; (3) assessing the significance of peak flows in transporting contaminants; and (4) developing methods for measuring the effectiveness of cleanup efforts. We sampled water downstream from the mine site over a wide range of streamflows. Mercury concentrations varied over 2000-fold, from 485 to 1 040 000 ng/l, grossly exceeding the regulatory water quality objective of 12 ng/l at all times. Particulate mercury represented over 99.97% of the total mercury, and mercury concentrations were closely correlated to suspended sediment concentrations (r=0.98). Thus, we can use suspended sediment concentrations as a proxy for mercury concentrations, and calculate a continuous record of mercury flux from continuous monitoring of streamflow (using a small flume) and turbidity (using an optical backscatter sensor). Mercury fluxes inferred in this way are consistent with fluxes estimated from field samples. In January and February of 1998, our small abandoned mine site released approximately 82 kg of mercury to downstream waters. Most of the mercury was released during brief intense rainstorms. For example, in one 200-min period we recorded 3.4 cm of rain, a 2.6-fold increase in streamflow (460–1120 l/s), and an 82-fold increase in mercury flux (1.2–99 g/min). Over 75% of the total mercury flux during this 2-month period occurred in less than 10% of the total time. In systems such as this one, where contaminant transport is highly episodic, sampling programs that miss the high-flow episodes may greatly underestimate the actual water quality threat. In addition, changes in pollutant fluxes or concentrations in receiving waters may not reflect changes in pollutant sources (such as an environmental cleanup) if the stochastic forcing (e.g. intense rainstorms) varies through time. We propose that water quality trends can be more accurately measured by changes in the relationship between contaminant flux and stochastic driving factors, as expressed by contaminant rating curves.     

Electrokinetic remediation of wood preservative contaminated soil containing copper, chromium, and arsenic

As a result of wood treatment, and the recent banning of the copper, chromium, and arsenic (CCA) treated wood for residential use many CCA treatment facilities have been abandoned or being closed. Soil contamination resulting from CCA is common at these sites. In this study, the feasibility of electrokinetic technique to remove CCA from contaminated soil was investigated. To better understand the ionic mobility within the soil and to detect the generation and advancement of acid front, sampling ports were provided along the longitudinal axis of a test cell. To determine the effect of varying current, three tests were performed at different current densities of 5.9, 2.9, and 1.5mA/cm(2) for a period of 15 days. The initial concentrations of copper, chromium, and arsenic in the soil were 4800, 3100, and 5200mg/kg, respectively. Dilute nitric acid was used as an amendment to neutralize the hydroxyl ions produced at the cathode. Experiments resulted in removal efficiencies as high as 65% for copper, 72% for chromium, and 77% for arsenic. The results also indicated that the advancement of acid front favored desorption of metals from the soil and the metals were mobilized either as free cations or metal complexes. Chromium that was in its +6 valence state was transported as anion prior to its reduction. However, once the chromium was reduced to chromium(III) its transport direction reversed with transport being favored towards the cathode.