The Water Table: The Shifting Foundation of Life on Land

Hyperarid, arid, and semi-arid lands represent over a third of the Earth’s land surface, and are home to over 38 % of the increasing world population. Freshwater is a limiting resource on these lands, and withdrawal of groundwater substantially exceeds recharge. Withdrawals of groundwater for expanding agricultural and domestic use severely limit water availability for groundwater dependent ecosystems. We examine here, with emphasis on quantitative data, case histories of groundwater withdrawals at widely differing scales, on three continents, that range from the impact of a few wells, to the outcomes of total appropriation of flow in a major river system. The case histories provide a glimpse of the immense challenge of replacing groundwater resources once they are severely depleted, and put into sharp focus the question whether the magnitude of the current and future human, economic, and environmental consequences and costs of present practices of groundwater exploitation are adequately recognized.     

The Costs of Corrosion: A Perspective

Until recently the materials engineer relied upon a combination of his experience and the use of economic analysis to make the proper choice of materials. His economic analyses required projection of useful life, probable obsolescence, eventual cost of equipment replacement—all seasoned with future predictions on the costs of money and labor.     

The chemistry of atmospheric mercury: a review

The atmosphere is an important transient reservoir of mercury. In addition to its great capacity, the chemical processes transforming mercury between the elemental and divalent states strongly influence the transport characteristics and deposition rate of this toxic metal back to the ground. Modeling efforts to assess global cycling of mercury require an in-depth knowledge of atmospheric mercury chemistry. This review article provides selected physical and chemical properties of atmospheric mercury, and discusses the identified mercury transformation pathways mediated by ozone, S(IV), hydroperoxyl radical, hydroxyl radical, chlorine, nitrate radical and photolysis of Hg(II) complexes. Special attention is paid to the kinetics and mechanisms of the reactions interconverting mercury between elemental and divalent states. The significance and implications of each transformation pathway under atmospheric conditions are addressed. Future research areas that must be pursued to better understand the fate and transformation of mercury in the atmosphere are also projected.     

The West: asking heretical questions

Aldous Huxley said 'All great truths begin as heresy.' It is important for every generation to ask heretical questions. Some of the current heretical questions in the West have to do with 'growth' – both of the economy and of population. The question of growth gives rise to such other questions as sustainability, immigration and carrying capacity.     

The reaction of nitrogen dioxide with lung surface components: The reaction with cholesterol

The reaction of nitrogen dioxide (NO₂) with cholesterol was investigated. NO₂ reacted with the hydroxyl group in cholesterol to produce cholesteryl nitrite. In this reaction, other minor products were observed. Cholesteryl nitrate, however, was not detected as was reported by other workers. Water accelerates and oxygen retards this reaction.     

The Impact of Air Pollution On Eastern White Pine: The Chlorotic Dwarf Disease

Chlorotic dwarf is a serious disorder of eastern white pine (Pinus strobus L) in young plantations. Diseased trees are stunted and possess only current mottled foliage. Investigations into this problem were to define its symptomatology and etiology and to develop measures for control. Previous work had shown that susceptibility to chlorotic dwarf is genetically controlled and that the disease results from an aerological agent acting directly upon the foliage. By controlling the atmospheres around chlorotic dwarf field trees, evidence was obtained to prove that chlorotic dwarf is effected by the injury of gaseous dispersoids on the foliage of susceptible individuals.     

Flue Gas Desulfurization: The State of the Art

ABSTRACT

Coal-fired electricity-generating plants may use SO₂ scrubbers to meet the requirements of Phase II of the Acid Rain SO₂ Reduction Program. Additionally, the use of scrubbers can result in reduction of Hg and other emissions from combustion sources. It is timely, therefore, to examine the current status of SO₂ scrubbing technologies. This paper presents a comprehensive review of the state of the art in flue gas desulfurization (FGD) technologies for coal-fired boilers.

Data on worldwide FGD applications reveal that wet FGD technologies, and specifically wet limestone FGD, have been predominantly selected over other FGD technologies. However, lime spray drying (LSD) is being used at the majority of the plants employing dry FGD technologies. Additional review of the U.S. FGD technology applications that began operation in 1991 through 1995 reveals that FGD processes of choice recently in the United States have been wet limestone FGD, magnesium-enhanced lime (MEL), and LSD. Further, of the wet limestone processes, limestone forced oxidation (LSFO) has been used most often in recent applications.

The SO₂ removal performance of scrubbers has been reviewed. Data reflect that most wet limestone and LSD installations appear to be capable of ~90% SO₂ removal. Advanced, state-of-the-art wet scrubbers can provide SO₂ removal in excess of 95%.

Costs associated with state-of-the-art applications of LSFO, MEL, and LSD technologies have been analyzed with appropriate cost models. Analyses indicate that the capital cost of an LSD system is lower than those of same capacity LSFO and MEL systems, reflective of the relatively less complex hardware used in LSD. Analyses also reflect that, based on total annualized cost and SO₂ removal requirements: (1) plants up to ~250 MW_e in size and firing low- to medium-sulfur coals (i.e., coals with a sulfur content of 2% or lower) may use LSD; and (2) plants larger than 250 MW_e and firing medium- to high-sulfur coals (i.e., coals with a sulfur content of 2% or higher) may use either LSFO or MEL.     

The crystal structure of octachlorodibenzodioxin: Experimental and calculated

The crystal structure of octachlorodibenzo-p-dioxin (OCDD) was determined and compared with the calculated geometry obtained by the semi-empirical modified neglect of diatomic overlap (MNDO) method. Experimental and calculated geometries for OCDD show excellent agreement.     

The benzene problem: impact of three-way catalyst technology: potential for further improvement

Chemical ionisation mass spectrometry (CI-MS) was applied to study the benzene emission characteristics of a TWC-vehicle at a time resolution of one Hertz. Three important operating conditions with increased emissions were identified: at vehicle start; at extended stop-and-go situations; and whenever a catalyst-induced benzene formation occurs. The cold start influence was detectable for about 200 seconds of driving corresponding to a distance of 1.2 km. At hot engine/catalyst mean pre- and post-catalyst emission rates of 25–150 mg km^-1 and 0.1–135 mg km^-1 were determined. Catalyst conversion varied from 0.07 to >0.99. Even negative conversion efficiencies were observed at several occasions, indicating that benzene can be formed de novo in a TWC. It is of importance to lower benzene emissions at these critical operating conditions to further reduce ambient air levels in cities and with it the cancer risk for large proportions of our population.     

The Fate of Vanadium in an Urban Air Shed: The Lower Delaware River Valley

Vanadium compounds are toxic pollutants which require engineering control in the design stage. In the lower Delaware River Valley, the main sources are presently the combustion of vanadium rich fuel oils and the catalytic processing of high vanadium crudes. These and other Industrial emissions, result in atmospheric vanadium concentrations which have varied from 0.133 μg/m³ to 0.557 μg/m³ between 1958 and 1969. Compounds of vanadium, principally with oxygen and sulfur, are considered. The dominance of oxygen compounds over sulfur compounds as derived from equilibrium data, and the tendency of vanadium oxides to move toward vanadium’s maximum valence of +5, indicate the prevalence of V₂0₅ as the emission compound.     

Air Analysis: The Standard Dosage-Area Product

The Dosage-Area Product is an areawide smog index obtained by combining contaminant concentration, duration, and areal extent: DAP = c×f×A (ppm × hr × mi²). The first step in developing a DAP is to plot daily contaminant dosages from an air monitoring network and to draw isopleths showing the dosage pattern. The second step is to determine the areas between isopleths and to multiply these areas by the applicable dosage levels. The final step is to sum the above partial products into a single number and to add a type designator indicating the geographic configuration of the dosage pattern. The DAP smog index is a realistic yardstick for measuring areawide smog experience. Reproducible results are obtained at low cost by using standard techniques. The standard DAP smog index is also useful for: analyzing air pollution episodes, estimating contaminant trends, and informing the public.     

The SUCOZOMA program: results and challenges

The research program Sustainable Coastal Zone Management (SUCOZOMA), which was started in 1996 by the Swedish Foundation of Strategic Environmental Research, was motivated by the recognition of increasingly severe global, regional and national coastal problems. The program approached the complex issues of coastal eutrophication, fishing practices, and overexploited coastal resources, with a concerted effort involving multidisciplinarity, stakeholder cooperation, and a focus on the problems perceived as most serious by the public and decision-makers. As the program was concluded in 2004 it had resulted in the completion or near-completion of 22 doctoral dissertations and approximately one hundred publications. More than 40 scientists were involved in the program. G?teborg University was the host university, but important research teams have also been located at Stockholm University, the Beijer Institute, and the Kristineberg Marine Research Station of the Royal Swedish Academy of Sciences, and within the National Board of Fisheries. During the program, networks of stakeholders were established and SUCOZOMA had contributed to numerous political and administrative processes relevant for integrated coastal zone management (ICZM). SUCOZOMA program results can be grouped into different categories. Many of the projects in the two phases of the program produced results which can be defined as technical or practical and available for direct implementation in, e.g. mussel cultivation, restoration and safeguarding of spawning areas, seal-safe fishing gear or sustainable fishing of underexploited species. Other results can be characterized as policy oriented, and the impact of these can only be fairly evaluated as new policies are put into effect. SUCOZOMA resulted in important new knowledge regarding coastal science and management, but also concerning the organization required to conduct an end-user oriented multidisciplinary program effectively.     

The Caspian Sea region: environmental change

Ecosystems in the Caspian Sea region have been heavily modified by anthropogenic activities, mainly as a result of changes in the water flow and degradation of the water quality in the ecosystems. Changes in the regional environment have influenced regional economies, particularly obvious in the impacts on fish stocks. Using the methodology developed in the GIWA project, experts in the region carried out an assessment of the most important transboundary issues in shared waters in the region. This report focuses on the root causes for the most important drivers of environmental change in the region: habitat and community modification.     

The Emergence of Black Carbon as a Super-Sorbent in Environmental Chemistry: The End of Octanol?

The distribution of aromatic contaminants between environmental solids and water solution reflects both absorption by the organic matrix (organic carbon, OC) and adsorption to black carbon (BC). In many instances, adsorption to BC dominates the interaction between aromatic contaminants and environmental solids. This holds especially true for the pyrogenically produced PAHs and PCDD/Fs, but also for the industrially produced PCBs and PCNs. In the future, research will need to surface-normalize the adsorption onto BC surfaces. One of the key questions to be addressed is the relative distribution and availability of contaminants associated with OC and BC fractions in environmental solids.