The Environment Challenges for the Chemical Sciences in the 21st Century (2003) / Chapter Skim
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Appendix D: Workshop Presentations
Appendix D: Workshop Presentations
Pages 66-148
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From page 66... ...
Three problems of key importance in the area of observations and modeling are: · Migration of nitrate, sulfate, heavy metals, and organic soot from urban or regional areas into the broader environment and associated public health issues; Forecasting climate change and testing the forecast in a way that is acceptable to a much broader range of individuals involved both in science and in public policy; and .
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From page 67... ...
We understand chemical transformations very well as illustrated by the Los Angeles basin. We know exactly what reactions are taking place, but the lack of specificity on the location and strength of sources and the way those couple into the chemical transformation serves to prevent a link between science and public policy on that question.
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From page 68... ...
We know why ozone is destroyed over the Antarctic and over the arctic, but there is also a seasonally dependent midlatitude ozone loss. The months of March, April, and May define a key period when schools let out, final exams are over, and the younger population gets a large episodic dose of ultraviolet radiation.
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From page 69... ...
From the societal perspective, the raw numbers are large and important for basal cell carcinoma: 800,000 cases per year. Until we understand the mechanism of midlatitude ozone loss, a simple extrapolation may be inaccurate, but it provides an important reference for discussion (Figure 2~.
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From page 70... ...
There are indeed large ozone losses in the vortex, but all of the large-scale flow is from the tropics northward and downward. Also, because we know the seasonal phase of CO2 and water over the tropical tropopause, we know that there is no communication backward from the polar regions to midlatitudes in these key months of ozone loss.
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From page 71... ...
Consequently, we do not believe that in situ loss of ozone is responsible for the long term trend in midlatitude ozone erosion, even though that would be the most reasonable explanation. This brings us back to the fundamental unsolved question of the coupling between the tropics and high latitude.
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From page 72... ...
72 7 APPENDIX D FIGURE 3. Deep convection in the tropics.
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From page 73... ...
Consequently, we don't believe that this is the explanation. We believe that polar stratospheric clouds are trapping highlatitude radiation in the infrared, but we believe the mechanism comes from the following: If CO2 enters the system or heat moves northward, the gradient between the tropics and the poles begins to soften, leading to reduced excitation of gravity waves and planetary waves driving from the troposphere up into the stratosphere.
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From page 74... ...
We must still address the question of testing climate forecasts. Atmospheric CO2 levels are rapidly increasing, as documented in the Intergovernmental Panel on Climate Change (IPCC)
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From page 75... ...
In the light-duty vehicle segments today the typical fuel economy expectation of a Diesel engine is 40% greater than that of the gasoline engine at equal vehicle performance on a fuel volume-normalized basis. Because Diesel fuel has roughly 15% more energy per gallon than gasoline, the benefit is roughly 25% on an energy-normalized basis.
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From page 76... ...
High-pressure common-rail fuel systems are state of the art, they provide substantially improved combustion manipulation ability compared to all progenitors, and turbocharging has become standard on all small high-speed, automotive Diesel engines. (Turbocharging Diesel engines is highly beneficial to vehicle fuel efficiency since smaller engines with lower friction can be used.
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From page 77... ...
Hence, multisite thermal autoignition will occur, provided that a particular temperature threshold is attained. This process is capable of producing very low emissions, but timing control of the thermal autoignition process is severely compromised, since the injection event is no longer capable of precisely triggering heat release.
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From page 78... ...
to effect chemical reduction of the trapped NOx. NOx absorbers are extremely sulfur sensitive and are rendered inactive when fuelbound sulfur, which leaves the engine as SO2, becomes catalytically oxidized to SO3 whereupon it reacts "irreversibly" with barium to form the comparatively more stable barium sulfate.
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From page 79... ...
market of this high fuel-efficiency technology in light-duty segments, several areas in which the chemical sciences could play a role are listed below. While the chemical kinetics of the thermal autoignition process are relatively well understood, means of controlling the ignition timing in the engine cycle when operating in the HCCI mode are still elusive.
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From page 80... ...
In its supercntical state it is also highly compressible, so that the density rises from approximately 0.5 g/mL at the critical temperature to about 0.9 g/mL at 10 °C. In that same range, the viscosity and surface tension remain at least an order of magnitude lower than those of water and most organic solvents.
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From page 81... ...
When considered as a solvent for chemical reactions, carbon dioxide offers a major advantage because it is essentially inert over wide ranges of temperatures and pressures. This prevents CO2 from participating in any chemical reactions that can contaminate the product or terminate important elementary steps in a reaction that may control molecular structure or molecular weights.
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From page 82... ...
~ 9 i0 have demonstrated that these CO2-soluble surfactants are able to form micellar aggregates in CO2, and that these aggregates are able to enhance significantly the solubility of high molecular weight, oleophilic, and hydrophilic species. These CO2-soluble surfactants are also able to stabilize latex particles in CO2, and they can be used to form water-in-CO2 and CO2-in-water emulsions.
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From page 83... ...
Currently, commercial photolithographic processes utilize chemically amplified photoresists and photoacid generators (PAGs) that are deposited from organic solvents using a spin coating technique.
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From page 84... ...
The spin coating was carried out in a specially designed and built high-pressure spin coating tool.~3 i4 The pressure in the spinning chamber was maintained at precise values ranging from 5 to 15 psi below the equilibrium vapor pressure of the CO2-photoresist solution. Control of this chamber pressure was a key parameter in the determination of film quality and thickness, as the pressure differential was what governed the evaporation rate of the liquid CO2.
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From page 85... ...
At DuPont we are measuring the way we "create shareholder value while decreasing our environmental footprint along our value chains." The term "footprint" includes raw materials, energy, emissions and waste, as well as injuries, illnesses, and environmental incidents. We are integrating this concept into all business decisions, into all local actions at the community level, and into helping lawmakers make fact-based decisions in enacting new pieces of legislation.
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From page 86... ...
The commitment to continue this pursuit now has to be accompanied by a commitment to protect our environment. The chemical industry's challenge lies in cleaning up contaminated water, reducing toxic air emissions, and reducing energy consumption and waste that leads to soil contamination (Box 4~.
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From page 87... ...
It is therefore incumbent upon the chemical industry to take a strong stand on reducing the environmental footprint that it has generated and could potentially create in the future. We must progress from an attitude of just complying with federal regulations to one where we earn the public's trust and move on to sustainable development.
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From page 88... ...
300 250 Miiilon s of 200 pounds 150 100 50 288 o- L 186 107 92 92 60 57 48 ~\~x ~~ ~; ikb ~ ~ ~c: FIGURE 2 Chemical air emissions by industry. These industries contribute 95% of the total emissions (1999 data)
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From page 89... ...
UMA CHOWDHRY 4,000 ~ 3,935 250 'A 200 150 100 50 o 89 258 220 49 6 4 1 Metals Electric Primary Treatment, Chemicals Paper Coal Food Stone/ Electrical Generatin Metals Storage, Mining Clay/ Equip. 9 Disposal & Glass Facilities Solvent Recovery Facilities FIGURE 3 Chemical soil contamination by industry.
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From page 90... ...
We have adopted the Six Sigma methodology that uses statistically significant, data-based understanding to reduce defects in our manufacturing processes. This methodology, coupled with process innovation, has led to lower raw material usage, lower energy consumption, lower emissions, and lower waste with annual pretax savings of over $1 billion over the past three years.
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From page 91... ...
Phosgene serves as an intermediate for some of our specialty fibers and agricultural intermediates. The State of New Jersey required us to reduce carcinogenic CC14, which forms as a by-product when chlorine and carbon monoxide are heated at high pressure.
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From page 92... ...
This, combined with hybrid cross-linking, provided a thinner coating with superior durability and scratch resistance coupled with smoothness and higher gloss. Not only did we reduce waste at our manufacturing site by decreasing the use of solvents, but we were able to help our customer DaimlerChrysler reduce its volatile organic compounds by 1.5 pounds per vehicle, hazardous air pollutants by 0.45 lbs per vehicle, odor emissions by 86%, and total raw material usage by 20%.
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From page 93... ...
a conventional oxide catalyst show dramatic improvements. The chemical process operated at 25% conversion and 20% yield and used an organic solvent in a typical chemical reaction.
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From page 94... ...
94 Shell: Degussa: ~ + CO + H2 MACHO + H2O + H2 FIGURE 7 Traditional chemical routes to 3G. In Nature: Two microorganisms convert sugar to 3G stepwise.
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From page 95... ...
of corporate revenue from renewable resources; · source 10% of our energy needs from renewable resources; · reduce greenhouse gases by 65% vs.
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From page 96... ...
96 APPENDIX D Maturity Maturity Growth Birth Birth 1 802 1 900 2000 2100 FIGURE 10 The transition to smart, sustainable growth.
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From page 97... ...
TABLE 1 Categorization of Combustion-Generated Air Pollutants. Category Examples Smog precursors Acute tonics Toxic air pollutants Endocrine disrupting chemicals Halocarbons Fine particles Persistent radicals CO NOx, volatile organic compounds (VOCs)
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From page 98... ...
A combustion engineer might focus on developing methods for their mitigation through design of control technology or combustion modification to prevent their formation. Table 2 presents a combustion system from the viewpoint of a combustion scientist.
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From page 99... ...
BARRY DELLINGER 99 second. Organic radicals are less reactive and may have lifetimes of several microseconds.
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From page 100... ...
100 APPENDIX D bilized and play a significant, possibly dominant role. The properties and elementary reactions of these resonance-stabilized species are poorly characterized from the chemical viewpoint.
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From page 101... ...
Research Recommendations · Research on photothermal and thermal reactions in flares and plumes including photothermal chemistry and spectroscopy as well as destruction and formation of toxic air pollutants · Elementary reaction kinetic studies of resonance stabilized radicals and how they impact formation of PAH and PAH radicals · Mechanistic studies of the partial oxidation of PAHs by thermal, photolytic, and photothermal pathways . Elementary reaction kinetic studies of CHCs and BHCs with specific emphasis on the reactions of chlorinated phenol and other dioxin precursors; chemically activated displacement reactions; C1, Br, H
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From page 102... ...
Dependable methods for studying elementary gas-phase reactions of organic radicals at elevated temperature . systems Methods for studying the spectroscopic properties of high-temperature · Techniques for metal speciation Recommendations for Support of Research · Development of m~croarrays for rapid screening of biological end points of complex mixtures Risk assessment methods for multiple pollutants from multiple sources Biochemical reactions of environmentally persistent free radicals COMPUTATION AND ENVIRONMENTAL SCIENCE David A
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From page 103... ...
For example, accurate thermochemical and kinetic calculations for the design of nuclear waste processing facilities and green chemical processes or for predicting tropospheric oxidation processes relevant to aerosol formation are needed due to missing experimental data. In addition, simulation allows one to explore temporal and/or spatial domains that are not accessible by present experimental methods.
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From page 104... ...
· Reliable prediction of chemical processes for carbon management including aerosol formation (organic oxidations, inorganic NH3-H2SO4-H2O chemistry, and nucleation processes) and sequestration and capture of CO2 (e.g., in geologic formations and in the ocean)
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From page 105... ...
· Chemical processing, including tank waste processing and separation systems for tank wastes as well as sensor design, green chemical processing strategies for waste remediation, and chemical and petroleum production to minimize waste streams and energy consumption, homogeneous and heterogeneous catalyst design (e.g., controlled oxidation of organics to produce intermediates for the chemical process industry or NOX or SOX emission reduction from combustion systems) , and models of the behavior of waste storage systems (e.g., glasses for radionuclide storage in Waste Isolation Pilot Plant or Yucca Mountain)
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From page 106... ...
For example, even the most sophisticated experimental techniques are unable to provide the details of the chemical reactions occurring at the surface of a heterogeneous catalyst or information about how to tune a homogeneous catalyst to gain a factor of 2 to 4 in performance. The coupling of theory and experiment provides the most profound insights into catalyst behavior enabling the design of new catalysts.
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From page 107... ...
the usage of raw materials, (2) energy utilization, and (3)
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From page 108... ...
However, a key ingredient in the success as well as the cost-effectiveness of remediation efforts is fundamental knowledge about the chemical properties and interactions of the wastes with their environment. This information is needed in order to develop and use in situ processes as unlike ex situ processes, there is usually no easy way to effectively halt an in situ process once it has begun.
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From page 109... ...
The calculation of interactions of chemicals, including those containing radioactive elements, with environmental matrices such as soils is incredibly complex and will require tens to hundreds of sustained teraflops to begin to reliably predict the molecular interactions of chemicals with environmental systems and to provide the underlying data needed for reactive transport models. High-quality data are needed, and great care must be taken to minimize the errors in the calculated underlying data used in a sophisticated environmental or chemical process model so that errors in the data do not accumulate, propagate, and ultimately invalidate the macroscopic-scale model.
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From page 110... ...
However, with future generations of computational resources, it will be possible to address scientific and technical issues that are fundamental for quantitative analysis of fluid transport in terrestrial systems and essential for improving predictive capabilities. Computation is essential for predicting the intricate web of species, reactions, and interconnections of transport in the natural system.
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From page 111... ...
but less detail in spatial and temporal resolution. Subsurface simulations have actually begun to impact geochemistry, geophysics, and environmental chemistry by encouraging holistic and mechanistically detailed investigations where multiple processes and multiple reactive components are considered and monitored in complex subsurface materials.
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From page 112... ...
They are compute-intensive, data-intensive, memory-intensive, and analysis-intensive. One area in which computational chemistry has played an important role in atmospheric chemistry is in the development of alternatives to the chlorofluorocarbons involved in stratospheric ozone depletion.
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From page 113... ...
Computation will be the major tool that enables us to cross the many temporal and spatial scales that characterize environmental science. CHEMICALLY RELATED R&D AT THE EPA'S OFFICE OF RESEARCH AND DEVELOPMENT William H
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From page 114... ...
fine particulates in air, · drinking water contaminants, · diesel engine emissions, and · mercury in air and water. The core research includes topics such as · ecological monitoring and assessment of ecological resources, · health risks to sensitive populations, · pollution prevention and green chemistry, and · environmental economics.
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From page 115... ...
Drinking water provides another example in which the by-products of disinfection illustrate ways that environmental chemistry is part of our everyday activities. We have also been looking at the nature of the toxin associated with Pfiesteria in order to understand the chemistry by which Pfiesteria produces lesions in fish and potentially has the ability to poison humans.
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From page 116... ...
In atmospheric chemistry, a particular focus of our R&D activities is the development of air quality models and scaling to models that can predict local, regional, and global impacts on air quality from sources that we have the ability to control. A new generation of air-quality models looks at community modeling of air quality (CMAQj, and this has provided a real advance for some of the regulatory activities that go on in EPA's program.
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From page 117... ...
WILLIAM H FARLAND 117 house primarily in our National Exposure Research Laboratory and our National Risk Management Laboratory.
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From page 118... ...
8 Other Eng Mechanical/ Industrial/ Civil & Env Eng Chemistry Other Science Biological Eng Chemical Eng FIGURE 1 Chemical sciences dominate pollution-prevention grants portfolio. APPENDIX D and chemistry community (Figure 1~.
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From page 119... ...
There are some important differences between groundwater and surface water with respect to water quality. Surface water is considerably more vulnerable to pathogens; groundwater provides some level of "natural protection" against bacteria and viruses that can cause outbreaks of human disease.
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From page 120... ...
Furthermore, groundwater-based irrigation has allowed substantial expansion of agricultural activities and has drastically improved the nutritional status of people in these areas. Nonetheless, the lack of attention to groundwater quality has had profound human health consequences, and these experiences illustrate the importance of evaluating the quality as well as the quantity of groundwater resources.
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From page 121... ...
Biogeochemical Processes Affecting Groundwater Composition In the physical context of water movement in subsurface and water-rock contact, we may then consider the biogeochemical processes that can affect the distribution of a constituent X between the immobile and mobile phases in the subsurface (Table 2~. Obviously, mobile constituents are of the most direct concern because of the potential for human exposure.
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From page 122... ...
complexing agents. In order to gain insight into the evolution of groundwater composition, these biogeochemical processes must be examined, and subsurface materials characterized, over multiple scales ranging from nanometers to kilometers (Figure 1~.
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From page 123... ...
23 FIGURE 1 Interrogation of multiscale subsurface biogeochemical processes. lution rates for a wide variety of minerals as well as their properties as sorbents for both inorganic and organic chemical species.4 The effects of factors such as solution composition, the type and surface area of the solid, and biological activity on both dissolution and sorption processes have been studied at this scale.
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From page 124... ...
Although the level of biogeochem~cal sophistication incorporated in these codes vanes widely, a few do incorporate biogeochemical kinetics as well as equilibrium reactions. The USGS code PHREEQC9 combines reaction kinetics with one-dimensional transport, and the code HydroBioGeoChem 123D includes both three-dimensional flow and transport in the vadose (i.e., unsaturated)
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From page 125... ...
JANET G HERING 125 served in these aquifers include buried peat depositsi2 i3 and newly infiltrated organic carbon derived from agricultural activities.6 The coupled biogeochem~cal cycling of iron and arsenic has also recently been studied in a system dominated by the addition of iron as an engineering practice.~4 Since 1996, ferric chloride has been added as a coagulant to the Los Angeles Aqueduct in order to control the levels of naturally occurring arsenic that reach the water distribution system for the City of Los Angeles.
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From page 126... ...
Yet, various needs must be addressed if the challenge of providing safe and adequate water supplies is to be met. The interrogation of biogeochemical processes and subsurface materials at a fundamental level requires continued support that recognizes both the value of studying well-controlled model systems and the need to work directly in complex, environmental systems.
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From page 127... ...
Atmospheric and environmental chemistry are rapidly evolving disciplines that play a critical role in a wide variety of current environmental issues spanning local, regional, continental, and global scales. Effective management of these issues generally requires knowledge of chemical and physical properties over a wide range of spatial and temporal scales, with processes involving fluid media (atmospheric, oceanic, surface, and groundwater)
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From page 128... ...
The constraints imposed by traditional environmental measurement methods generally lead to environmental systems being badly undersampled in the spatial and/or temporal domains. The undersampling of environmental systems often has several unfortunate consequences.
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From page 129... ...
and assessments of the effectiveness of air quality regulations.2 Environmental Measurement Strategies It is important to recognize that environmental scientists make measurements for a variety of reasons, each of which imposes its own requirements and constraints on the instrumentation and measurement systems to be used. General environmental measurement modes include exploratory mapping and surveying, process investigations, baseline establishment and trend monitoring, and emission-deposition and other flux measurements.
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From page 130... ...
remote sensing instruments playing a large role in our understanding of global-scale environmental issues such as stratospheric ozone destruction and climate change. Further discussion of these three approaches, their application to a variety of environmental problems, and the instrument challenges they pose can be found in the report of a recent workshop on environmental instrumentation sponsored by the National Science Foundation.3 The environmental science community has made enormous advances in Instrumentation for Environmental Science 2000—Report of a Workshop and Symposium, National Science Foundation, Arlington, VA, 2000.
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From page 131... ...
One point made in the NSF report is that anticipated advances in sensors based on micro- and nanotechnologycoupled with advanced information technology solutions to the problems of data collection, processing, dissemination, and display may make the distributed sensor network measurement strategy much more powerful and affordable. Over the past 15 years, the atmospheric science community has developed a series of mobile platforms with highly accurate and specific fast response instrumentation that have revolutionized atmospheric chemistry field measurements.
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From page 132... ...
Proton Transfer Reaction Mass Spectrometer Rapid Measurement of selected VOC's ...; Condensation Particle Counter Number Density Tunable Diode Lasers Combinations of NO, NO2 CO, N2O, CH4, SO2, HCHO typical detection limit < 1 ppb ............
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From page 133... ...
In order to produce the instruments and platforms that meet the specifications required by the measurement strategies listed in Box 1, advances in enabling technologies must be exploited. Table 2 lists some of the enabling technologies that are currently undergoing rapid development and presents examples of the improvements in environmental instrumentation and measurement platforms they have or may soon allow.
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From page 134... ...
134 APPENDIX D TABLE 2 Impacts of Enabling Technologies Technology Examples of Evolving Impacts Structural materials Energy systems Electro-optics Semiconductor technology Ion optics Lighter, more robust sensors and sensor platforms Smaller, longer lasting off-grid power sources, enhanced platform propulsion systems Compact, efficient solid state lasers and detectors, compact long-path sampling cells, detector arrays Compact, robust electronics, throw-away sensors and data systems Ion traps, smaller TOF and quadrupole mass filter spectrometers Vacuum technology Fieldable sensors based on electron, ion, molecular, particle beam methods Information technology Real-time data processing and display, multisensor integration, data fusion and assimilation Control technology Autonomous instrument-platform operation, real-time Fluid dynamics Biotechnology Nanotechnology experimental design More efficient airborne platforms, better sampling systems Smaller, faster diagnostics for microbial and biologically active molecules Smaller, lighter, cheaper everything Figure 3 shows an airborne version of one recently developed fast response instrument made possible by recent advances in materials, vacuum technology, ion optics, fluid dynamics, information technology, and control technology.6 This aerosol mass spectrometer allows the real-time measurement and display of the nonrefractory, size-resolved (~30 nm to ~1500 nm) ambient aerosol particle mass loadings.
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From page 135... ...
" ' | /4 , ,, ,,,,, ,.,,, , ,,,,,,.,, ,,,, ,A, u L _. 12:00 PM 12:30 PM 1:00 PM 1:30 PM 2:00 PM 7/22/2002 Date and Time 2:30 PM 3:00 PM 3:30 PM 8000 6000 D 4000 2000 o FIGURE 4 Aerosol mass spectrometer airborne measurements of fine particle compositional mass loading and size distributions showing two sulfate aerosol layers in air masses from the Ohio River valley.
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From page 136... ...
The biological availability and use of these metals are modulated by intracellular and extracellular binding compounds produced by microorganisms. The chemistry of bioactive metals in the environment, including their coordination to binding agents and to appropriate centers in proteins, thus controls the efficiency of critical environmental processes that govern the global cycles of carbon and nitrogen.
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From page 137... ...
In the surface oceans, which are singularly depleted in zinc, a number of phytoplankton species have evolved the ability to replace zinc with cobalt and cadmium in carbonic anhydrase.2 3 In diatoms, which are arguably the most important primary producer in the modern oceans, it appears that the activity of the external carbonic anhydrase is enabled by the formation of a silica frustule that serves, in part, as a proton buffer at the surface of the cell.4 Unraveling the conditions that allow for an efficient Zn-Co-Cd replacement in carbonic anhydrase (and similar enzymes) in marine autotrophs and of the use of silica as a local proton buffer will provide a molecular understanding of the links between the global cycles of these trace metals and of CO2 and SiO2.
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From page 138... ...
All the steps in the nitrogen cycle are catalyzed by metalloenzymes (Figure 2~. For example, all forms of nitrogenase (the enzyme responsible for N2 fixation)
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From page 139... ...
NOTE: AMO = ammonium mono-oxygenase; HAO = hydroxylamine oxidoreductase; NAR = membrane-bound respiratory nitrate reductase; NAP = periplasmic respiratory nitrate reductase; NR = assimilatory nitrate reductase; NIR = respiratory nitrite reductase; NiR = assimilatory nitrite reductase; NIT = nitrogenase; NOR = nitric oxide reductase; N2OR = nitrous oxide reductase. rate of nitrogen fixation in the oceans.8 9 There is also some evidence that, in some suboxic waters, the concentration of available copper may be too low for the activity of the copper enzyme nitrous oxide reductase and result in N2O accumulation and release to the atmospheres Understanding the nitrogen cycle of the oceans and the release of some important greenhouse gases such as N2O to the atmosphere thus requires that we elucidate the acquisition of metals such as iron and copper and their biochemical utilization by various types of marine microbes.
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From page 140... ...
This paper outlines some of the new technologies that are playing an integral role in catalyzing that change. Topics of discussion include new chemical process technology and chemical catalysis that allows for more efficient production of herbicides as well as transgenic crops and their benefits to agriculture and the environment.
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From page 141... ...
The new catalyst technology had significant environmental benefits. These included the use of less toxic raw materials and the elimination of nearly all of the waste produced by the older technology.
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From page 142... ...
What we needed was a catalyst that could do two reactions at the same time. The first reaction converts glyphos ate intermediate to glyphosate and the other is to react away the undesirable by-products.
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From page 143... ...
This new technology has many economic and environmental benefits. Expansion of the global acreage planted with Roundup Ready crops has resulted in a reduction of the use of pesticides by nearly 50 million pounds per year.
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From page 144... ...
In this sense, 1947 represents the birth of stable isotope chemistry. Subsequently, an enormous range of applications has emerged utilizing isotope ratio measurements as a probe of natural processes that include studies of atmospheric chemical processes, paleoceanography and climate, stable isotope geochemistry, and planetary sciences.
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From page 145... ...
The inclusion of the second isotope ratio measurement adds a sensitive probe of processes that may not be afforded by concentration or single isotope ratio measurements. As such, the use of mass-independent isotope compositions of environmental molecular species has provided a new probe to understand natural processes and to characterize anthropogenic impacts.
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From page 146... ...
Most recently, isotopic measurements of a new variety have proven to be particularly valuable. These observations utilize high-precision measurements of the isotopomenc fragments of NO in a mass spectrometer.9~0~2 From such measurements, the internal N2O isotopomenc distribution may be determined.
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From page 147... ...
Atmospheric Aerosol Sulfate and Nitrate Atmospheric sulfate aerosols are known to exert a significant influence on Earth's surficial processes. They mediate climate, both as cloud condensation nuclei and as light-scattering agents.
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From page 148... ...
As is the case of sulfate, nitrate aerosols also possess large, mass-independent isotopic compositions. Nitrate concentrations may double in the next half-century with severe environmental consequences, including alteration of biodiversity, enhanced algal blooms, and loss of agricultural productivity.
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