The Environment Challenges for the Chemical Sciences in the 21st Century (2003) / Chapter Skim
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3 Challenges in Environmental Chemical Science
3 Challenges in Environmental Chemical Science
Pages 22-49
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From page 22... ...
In some cases, the source of such chemicals is natural, as in the highly publicized case of arsenic-contaminated groundwater in Bangladeshi and also in some parts of the United States.2 Chronic exposure to small amounts of arsenic in drinking water increases a person's risk of cancer and other diseases.3 High concentrations of arsenic found in the aquifers in Bangladesh and West Bengal pose serious threats to public health; estimates of population at risk run from 30,000,000 to a high of 80,000,000.4 In other instances, human activity has been the origin of the chemical release. Some of the most important cases are also the most ironic because the harmful effects on the environment were a direct consequence of a technological innovation that was intended to enhance environmental quality.
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From page 23... ...
CHALLENGES IN ENVIRONMENTAL CHEMICAL SCIENCE 23 How can environmental problems such as those associated with arsenic, DDT, and CFCs be solved? More specifically, how can the problems be resolved, how can release of pollutants into the environment be reduced or stopped, and how can harmful materials be removed from the environment?
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FUNDAMENTAL UNDERSTANDING Human Influence on the Natural Environment Evidence of anthropogenic influence on the natural environment is widespread: Examples include pesticide use (see Box 3-1) , stratospheric ozone depletion (see Box 3-2)
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26 THE ENVIRONMENT even more rapidly than either PCBs or dioxins.9 The most comprehensive assessment to date of PBDEs in the breast milk of North American women indicates that the body burden in Americans and Canadians is the highest in the world, 40 times greater than the highest levels reported for women in Sweden.~° Fluorinated organic compounds are globally distributed, environmentally persistent, and bioaccumulative.~i Water and Sediment Chemistry Environmental chemistry has progressed significantly over the past four to five decades from a science that was concerned primarily with measurements of trends in the distribution of problematic species in the environment to the more 9Ikonomou, M G.; Rayne, S.; Addison, R
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From page 27... ...
We need to move from empirical observations that feed well into large-scale models of transport, circulation, biodegradation, and other processes, to developing a fundamental understanding of the biogeochemical processes at a molecular level. It is only then that we can truly understand the factors governing such processes.
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From page 28... ...
Humic substances and their production from plant materials are important factors and we need to know more about the relevant biological and chemical processes down to the molecular level. Related to this is the nature of dissolved organic matter in natural waters a huge reactive and storage reservoir for carbon.
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From page 29... ...
We need to know how contaminants are hydrologically transported in a medium where they continually interact at the molecular level with DOM and with mineral, biological, and organic phases of soils and sediments. The occurrence and mobility of harmful chemical substances, whether of natural origin or anthropogenic contaminants, in the subsurface environment pose both an intellectual and fundamental scientific challenge and practical concerns for the use and management of groundwater resources.
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Not only does chemistry play an important role in characterizing the compounds of interest (a challenge for analytical chemists who often must do this at subpicomolar concentrations) , but it is central to understanding the processes by which bioavailable forms become incorporated into cellular struc.
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From page 31... ...
In addition, there is a need to characterize the chemical structure within particles. Whether individual particles are chemically homogeneous or have organic coatings or inorganic incrustations, for example, will affect their radiative properties, atmospheric removal, heterogeneous reactions, and role as nuclei for cloud droplet formation and growth, as well as their health consequences.
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i4Challenges for the Chemical Sciences in the 21st Century: National Security & Homeland Defense, National Research Council, The National Academies Press, Washington, D.C., 2002.
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Chemists and chemical engineers use three basic tools to measure and describe the chemistry that is taking place in our environment: 1. laboratory measurements and devices to simulate and characterize that chemistry; 2.
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Extensive research, enabled by improved analytical measurements, has been carried out on the mechanism of formation of dioxins and other chlorinated organics. Researchers discovered that many combustion-generated pollutants actually are formed after the flame zone not only by surface catalyzed reactions but also in the gas phase by high- and medium-temperature thermal processes.
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Atmospheric chemistry is dominated by trace species, ranging in mixing ratios (mole fractions) from a few parts per million, for methane in the troposphere and ozone in the stratosphere, to hundredths of parts per trillion, or less, for highly reactive species such as the hydroxyl radical.
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Just as ignorance of heterogeneous chemistry contributed to the failure of stratospheric ozone models to anticipate the formation of the antarctic ozone hole, much still is to be discovered and learned about the role of heterogeneous reactions in the troposphere.
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, anions (SO42-, NO3-, C1-, etc.) , and organic acids using particle collection and ion chromatography, and real-time particle mass spectrometry using thermal desorption-electron ionization.
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and fluorescence or mass spectrometry to obtain visual and time evolution information (NMR) and high specificity and sensitivity (optical and mass spectrometry)
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It is likely that in situ and remote sensing will be used concurrently, while the resulting data are evaluated in a model in real time. For example, impressive and expensive mobile measurement systems were used in evaluating the problem of stratospheric ozone depletion by simultaneously measuring several different radical species (halogen, hydrogen-oxygen, and nitrogen oxide)
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With such higher-performance computers, accurate quantum mechanical calculations should be possible with heavy elements for which relativistic corrections are significant, accurate zero-point energies can be calculated to improve the accuracy of thermodynamic calculations dramatically, and rate equations can be used to search more accurately for transition states and to study interracial reactions (including those at the cellular interfaces of biological systems)
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From page 41... ...
This is illustrated in for atmospheric chemistry in Figure 3-1. Current methodologies 2iMany of the relevant issues are covered in one of the other reports in this series, Challenges for the Chemical Sciences in the 21st Century: Information and Communications, National Research Council, The National Academies Press, Washington, D.C., 2003.
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From page 42... ...
Such problems include . the urban-to-regional migration of nitrate, sulfate, heavy metals, and organic soot into the broader environment and the associated public health issues; · forecasting climate change and testing the forecast in a way that is acceptable to decision makers in science and in public policy; · ultraviolet dosage and its relationship to ozone depletion; · structure-toxicity relationships; · forecasting adaptation to global climate change; · chemical behavior and trends in oceans and estuaries; · molecular origins of toxicity (including gene-toxicant interactions)
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The observations must be linked to trajectories, the trajectories must be initialized, and sources of specific chemicals must be identified along with the positions of those sources. Considerable progress has been made on observations and refinement of models to help explain low ozone loss at the mid-altitudes, the increase in UV dosage, the appearance of water vapor in the stratosphere, and possibly, of climate changes 50 million years ago.
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APPROACHES TO SOLUTIONS Pollution Prevention: Green Process Technology Green chemistry focuses on the design, at the molecular level, of manufacturing processes and products that are environmentally benign reducing or eliminating the use of hazardous materials. A common definition of green chemistry is "the design, development and implementation of chemical processes and products to reduce or eliminate substances hazardous to human health and the environment."22 Guided by a set of 12 principles,23 green chemistry offers the potential to develop technologies that could provide an important new approach to environmental protection through pollution prevention.
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A recent report from the RAND Science and Technology Policy Institute lists four major barriers to the development and implementation of new green technologies.24 Finding ways to overcome these barriers will be a significant challenge to chemists and chemical engineers as they pursue their R&D agenda in the environmental arena: neenng; · Need for additional research, technology development, or process engi24Lempert, R J.; Norling, P.; Pernin, C.; Resetar, S.; Mahnovski, S
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For example, in situ generation of hydrogen peroxide can be used to produce propylene oxide in place of the chlorohydrin route; and · Dimethyl carbonate: new methods for synthesis and use of dimethyl carbonate could greatly reduce the use of highly toxic feedstocks such as phosgene; other waste streams (such as HC1) would be reduced as well.
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From page 47... ...
[David Dixon, Appendix D] Factors that must be considered in developing a remediation strategy include the chemical nature, quantity, and location of the contaminants; the permeability of the soil and how soil interacts with contaminants; and how various cleanup or containment methods may impact workers, the community, and remediation costs.
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. Cost-effectiveness A major challenge to the chemists and chemical engineers in developing solutions to environmental problems is that of cost.
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Research investment will need to address interdisciplinary activities, the need for development of new instruments, improved computational capabilities, and shared user facilities that may be too expensive for individual institutions.
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