Chemicals manmade

Water dissolves all kinds of substances and reacts chemically with many of the atmospheric pollutants we ve encountered in earlier chapters. Several nitrogen oxides and sulfur oxides react readily with water in the atmosphere to produce acidic rainfall that can have a very negative impact on our environment and on many building materials. Dissolved substances in liquid water can include natural minerals and chemicals, manmade fertilizers and pesticides, gasoline and fuel additives, toxic chemicals of all types, and even unused antibiotics that people have flushed down the toilet. To minimize environmental damage and to ensure a safe and adequate water supply, we must limit all types of pollution. We must control both the amount of pollution and the types of pollution to which we subject our water supply because what we ve got is all there is. The water must be used, reused, and used s ain, over and over, in a never-ending cycle. If it becomes polluted, we will have to clean it up. 

Chemists make compounds and strive to understand their reactions. My own interest lies in the chemistry of the compounds of the elements carbon and hydrogen, called hydrocarbons. These make up petroleum oil and natural gas and thus are in many ways essential for everyday life. They generate energy and heat our houses, fuel our cars and airplanes and are raw materials for most manmade materials ranging from plastics to pharmaceuticals. Many of the chemical reactions essential to hydrocarbons are catalyzed by acids and proceed through positive ion intermediates, called carbocations. 

Prior to 1940 only the naturally occurring actinides (thorium, protactinium and uranium) were known the remainder have been produced artificially since then. The transactinides are still being synthesized and so far the nine elements with atomic numbers 104-112 have been reliably established. Indeed, the 20 manmade transuranium elements together with technetium and promethium now constitute one-fifth of all the known chemical elements. 

When used as substitutes for asbestos fibers, plant fibers and manmade cellulose fibers show comparable characteristic values in a cement matrix, but at lower costs. As with plastic composites, these values are essentially dependent on the properties of the fiber and the adhesion between fiber and matrix. Distinctly higher values for strength and. stiffness of the composites can be achieved by a chemical modification of the fiber surface (acrylic and polystyrene treatment [74]), usually produced by the Hatschek-process 75-77J. Tests by Coutts et al. [76] and Coutts [77,78] on wood fiber cement (soft-, and hardwood fibers) show that already at a fiber content of 8-10 wt%, a maximum of strengthening is achieved (Fig. 22). 

CFC-12. These manmade chemicals absorb infrared radiation in a part of the spectrum where water vapor and CO2 do not already have strong bands. On the other hand, the manmade increase of CO2 is so large (currently ca. 25% since the mid-1800s - see Chapter 11) that it is the largest anthropogenic input to the greenhouse effect (not counting feedbacks). 

About half the manmade emissions of sulfur dioxide become sulfate aerosol. That implies that currently 35 Tg per year of sulfur in sulfur dioxide is converted chemically to sulfate. Because the molecular weight of sulfate is three times that of elemental sulfur, Q is about 105 Tg per year. Studies of sulfate in acid rain have shown that sulfates persist in the air for about five days, or 0.014 year. The area of the Earth is 5.1 x lO m. Substituting these values into the equation for B yields about 2.8 X 10 g/m for the burden. 

Somewhere between 70% and 90% of human cancers appear to be of environmental origin. Here environmental is used very broadly, and refers to anything not genetic. It refers not only to industrial chemicals and pollutants, but includes factors such as diet, sexual habits, smoking behavior, and natural and manmade radiation. 

The entire spectrum of inorganic fibers can be divided into two classes, based on differences in the crystallinity of the solids (Ray, 1978). Synthetic fibers have been known as man-made mineral fibers (MMMF) and manmade vitreous fibers (MMVF). But fibrous materials can be approached or divided in other ways. For example, in the Concise Encyclopedia of Chemical Technology (1985) the entry for chemical fibers includes both manmade and natural polymers, with the discussion centering on carbon-based compounds such as acetates, acrylics, and cellulose. Fibers of other inorganic compounds were not mentioned in the encyclopedia under this entry, but silica glass fibers were described under the heading Optical Fibers. ... 

These processes are both natural and manmade. In fact, the Los Angeles basin was called by the early Native American inhabitants the land of the smokes, and salt spray from oceans is a major source of Cl in the atmosphere. In many situations people have only exaggerated the natural chemicals and reactions that were present before we and our technology arrived. The Smoky Mountains are an example of natural smog caused by chemicals such as isoprene (the natural mbber monomer) and terpenes, which are emitted by trees. 

On a global scale the air layers within a few kilometers of the earth s surface are rapidly mixed by wind action. This region is called the troposphere. Natural and manmade sources of chemicals such as CH4 and other hydrocarbons, CO, SO, NO, ozone, and chlorine are emitted into the troposphere. Most of these are removed or reacted away to form harmless products by dissolving in rain, adsorption on solids, and chemical reactions. 

Thus we see that environmental modeling involves solving transient mass-balance equations with appropriate flow patterns and kinetics to predict the concentrations of various species versus time for specific emission patterns. The reaction chemistry and flow patterns of these systems are sufficiently complex that we must use approximate methods and use several models to try to bound the possible range of observed responses. For example, the chemical reactions consist of many homogeneous and catalytic reactions, photoassisted reactions, and adsorption and desorption on surfaces of hquids and sohds. Is global warming real [Minnesotans hope so.] How much of smog and ozone depletion are manmade [There is considerable debate on this issue.]... 

The potential of any chemical for environmental damage must be assessed before its commercialization, and our capability for doing so, should be expanded, although we recognize the possibihty that the new chemical might replace another substance, natural or manmade, already in use that could be even more damaging. Those cases demonstrate the need for continuous review of costs and benefits, which might not be the same for all countries and communities. 

Isophorone is a clear liquid with a peppermint-like odor. It evaporates faster than water but slower than charcoal starter or paint thinner, and it will not mix completely with water. Isophorone is a manmade chemical for use commercially, but it has been found to occur naturally in cranberries. It is used as a solvent in some printing inks, paints, lacquers, and adhesives. Isophorone does not remain in the air very long, but can remain in water for possibly more than 20 days. The length of time that isophorone will remain in soil is not known, but it probably is about the same as the length of time it remains in water. More information can be found in Chapters 3 and 4. 

While the Swedish Government sees the PP as an instrument to restrict the overall use of manmade chemicals in society, the EU Commission reserves its implementation of the PP to risks that in the event of non-action may have serious consequences. The EU Commission s statement is similar to the second sentence of Principle 15 in the Rio Declaration, which reserves the use of the PP to threats of serious or irreversible damage. The words of the EU Commission and the Rio Declaration impose considerable restraints on when the PP should be applied, and the EU Economic... 

Note that if the sediment surface were to consist of freshly sedimented particles with concentration Cssc = C°p, then the pore water in equilibrium with these particles would have the aqueous concentration C c = C p, and thus according to Eq. 23-24 the diffusive exchange flux Fsed difr would be zero. However, in most cases the sediment surface is not in equilibrium with the water column, because diagenetic processes change the physicochemical properties of the sediments and thus its solid-water distribution ratio, Kf, relative to. Furthermore, the sediment surface usually reflects a longer history of exposure to the chemical under consideration than the water column. Therefore, water and sediments would approach equilibrium only if the external loading to the lake has changed very slowly in the past. For manmade chemicals this is usually not the case. 

The introduction of rayon, nylon and other manmade fibers with their greater strengths per unit cross sectional area compared with cotton fabric has led to the use of rubber coated fabrics in the manufacture of various engineering products such as tyres, beltings and hoses and also several specialty products for the chemical process industries. The arduous service conditions prevailing... 

The chemical elements are the building blocks of nature. All substances are combinations of these elements. There are (as of 2005) 113 known chemical elements with the heaviest naturally occurring element being uranium (Z = 92). The 22 heaviest chemical elements, the transuranium elements, are manmade. The story of their synthesis, their properties, their impact on chemistry and physics, and their importance to society is fascinating. This story is of particular importance to nuclear chemistry because most of our knowledge of these elements and their properties comes from the work of nuclear chemists, and such work continues to be a major area of nuclear chemical research. One of us (GTS) has been intimately involved in the discovery and characterization of these transuranium elements. 

The chemical behavior of the transuranium elements is interesting because of its complexity and the insights offered into the chemistry of the lighter elements. The placing of these manmade elements into the periodic table (Fig. 15.1) represents one of the few significant alterations of the original periodic table of Mendelyeev. Since so little is known about the chemistry of the transactinide elements, one has the unique opportunity to test periodic table predictions of chemical behavior before the relevant experiments are done. 

Despite the diverse chemical types represented by forest pesticides, the variety of their formulations, and the many rates and routes of application, two factors remain consistently present in their environment—sunlight and powerful reagents. Quite apparently, these forces are active and acting. The well-known "blue haze" observed over forests in many parts of the world remote from man s chemical wastes is a result of photooxidation reactions of volatile natural chemicals similar to those which generate manmade smog. 

The photoreceptors of the eye utilize "dyes" to convert the incoming light into at least the precursor to a nervous system signal. The field of dye chemistry is extremely well developed and broad. It is also extremely complex. For many years, dye chemistry delineated itself between natural dyes and man-made dyes. This was done for a number of reasons the natural dyes were generally inferior in absorption, stability and applicability to all but the first few manmade counterparts and the natural dyes involved grossly different fabrication techniques. However, the chemical rules derived during the development of man-made dyes are also applicable to the natural dyes. In recent years, the separation between natural dye chemistry and man-made dye chemistry has begun to disappear. Many natural dyes can now be classified in the same tables as the man-made dyes. This will be demonstrated below. 

Thirty years after their production ban in most industrialized countries, PCBs are still present in the environment and in the food chain. PCBs are manmade chemicals that never existed in nature until the 1900s when they started to be released into the environment by manufacturing companies and consumers. These chlorinated oils have a low degree of reactivity. They are not flammable, have high electrical resistance, good insulating properties, and are very stable even when exposed to heat and pressure. All in all, they seemed to be the perfect oil for use in dielectric fluids, and as insulators for transformers and capacitors. Uses for... 

Both the activation of lignin and its crosslinking to form a binder for wood material could be performed by a single biotechnological process based on the observation that enzymes are often much more powerful catalysts in the conversion of naturally occurring polymer molecules than manmade chemicals can ever be. 

Psychoactive drugs can he classified according to whether they are natural or manmade, produced by our own bodies or by plantvS, crude mixtures of substances or single, purified chemicals. These differences may influence the relationships people form with drugs, and users, especially, should be aware of them. 

Pesticides are chemicals or biological substances used to kill or control pests. They fall into three major classes insecticides, fungicides, and herbicides (or weed killers). There are also rodenticides (for control of vertebrate pests), nematicides (to kill eelworms, etc.), molluscicides (to kill slugs and snails), and acaricides (to kill mites). These chemicals are typically manmade synthetic organic compounds, but there are exceptions which occur naturally that are plant derivatives or naturally occurring inorganic minerals. 

Our understanding of chemical dynamics has become increasingly more detailed as experimental and theoretical methods have advanced. One of the ultimate goals of these endeavors is to develop reliable, predictive models so that we can foretell the detailed outcome of chemical reactions. The motivation to develop such predictive capabilities is often driven by the need or desire to understand and describe the chemistry in some extreme environments. These extreme environments, with conditions well outside the range of common room temperatures or pressures, can be natural or manmade. 

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