Problem soils, definition

Electro-osmosis has been defined in the literature in many indirect ways, but the simplest definition comes from the Oxford English Dictionary, which defines it as the effect of an external electric held on a system undergoing osmosis or reverse osmosis. Electro-osmosis is not a well-understood phenomenon, and this especially apphes to polar non-ionic solutions. Recent hterature and many standard text and reference books present a rather confused picture, and some imply directly or indirectly that it cannot take place in uniform electric fields [31-35]. This assumption is perhaps based on the fact that the interaction of an external electric held on a polar molecule can produce only a net torque, but no net force. This therefore appears to be an ideal problem for molecular simulation to address, and we will describe here how molecular simulation has helped to understand this phenomenon [26]. Electro-osmosis has many important applications in both the hfe and physical sciences, including processes as diverse as water desahnation, soil purification, and drug delivery. 

The effects of transport on economy, people and on the environment are manifold. They include the consequences of transport accidents and fatalities, nuisance and health effects caused by steady noise exposure, air emissions and the exhaust and resuspension of particles, climate impacts by the emission of greenhouse gases, soil and water contamination, and the deterioration of natural habitats. Moreover, the financial burden of infrastructure provision and the additional travel and production costs caused by congestion should be mentioned but these items are mainly borne by transport users themselves and thus are only partly imposed on society as a whole. Not all of these effects are equally relevant for all means of transport. While accidents constitute the major problem of car travel, the railways definitely face a noise problem and air transport contributes most to the emission of climate gases. 

Jince the time of Berzelius, chemists have proposed structures for the amorphous, black substance known as humic acid. In the past 150 years, much experimental work has appeared on the nature of humic acid, most of it based on classical chemical and microbiological studies. Very little information about the molecular structure of humic add has resulted from these studies however. Some of the problems plaguing investigators in this field have been (a) variation in the source of humic acid, (b) variation in the definition of humic fractions of soil and coal, (c) lack of crystallinity of the samples, (d) uncertainty of molecular weight measurements, (e) variation in extraction techniques, and (f) variation in elemental composition. The little unambiguous information that exists today is based on extensive degradation of the humic acid polymer and represents only a small fraction of the total molecule. 

The application of chemical kinetics to even homogeneous solutions is often arduous. When kinetic theories are applied to heterogeneous soil constituents, the problems and difficulties are magnified. With the latter in mind, one must give definitions immediately for two terms—kinetics and... 

While the ratios defined in Eqs. (6) and (7) conveniently yield dimensionless factors, the last of these equations yields rather cumbersome units of m2 kg-1. These three transfer factor equations give some idea of the range of ways in which individual radioecologists have tackled the problem of expressing the gross uptake of radionuclides by plants in some easily quantifiable form, but it is Eq. (6) which provides us with the most commonly used definition which has been adopted by the International Union of Radioecologists (IUR) as the working definition for their soil-to-plant transfer factor data base. 

Furrer, G., Westall, J. C., and Sollins, P. (1989) The Study of Soil Chemistiy Through Quasi-steady State Models I. Mathematical Definition of the Problem, Geochim. Cosmochim. Acta 53, 595-601. 

The most serious problem in the study of humic substances is the lack of reproducibility of analytical results. One would expect soil humates to vary with soil type, aquatic humates to vary with water sources, and coal humates to vary with coal rank. But even within one well-defined source, the elemental composition will vary between samples, depending on extraction and fractionation procedures. There are cases in which the same authors have used the same source and the same extraction procedure and have obtained significantly different elemental analyses. Before any meaningful structural conclusions can be deduced from elemental analysis, a rational definition of humic substances will have to be established (MacCarthy, 1976 Malcolm and MacCarthy, 1979). 

Aramentano, T. V. (1979). The role of organic soils in the world carbon cycle problem definition and research needs. The Institute of Ecology, 37 pp. 

In this book air chemistry is defined as a branch of atmospheric science dealing with the atmospheric part of the biogeochemical cycle of different constituents. In other words this means that we will deal mainly with the atmospheric pathways of those components that are involved in the mass flow between the atmosphere and biosphere, as well as in chemical interactions between the air and the other media of our environment (soils, oceans etc.). It follows from this definition that, on the one hand, our discussion will be restricted to the troposphere and the stratosphere4 and, on the other hand, the photochemistry of the upper layers, the subject matter of the aeronomy (e.g. Nicolet, 1964), will be omitted. This separation of the (photo) chemistry of the lower (troposphere and stratosphere) and upper atmosphere makes it possible to give a more compact treatment of our problem, including the global anthropogenic effects due to the increase of air pollution. 

Petroleum hydrocarbons are a mixture of many substances. The results of petroleum analysis depend as much on the analytical method as the petroleum. As long as everyone works to a common definition there is no problem. The Total Petroleum Hydrocarbon Criteria Working Group (TPHCWG) convened in 1993 to develop scientifically defensible information for establishing soil cleanup levels that are protective of human health at petroleum contaminated sites. The TPHCWG compiled their data and analytical efforts into five volumes that can be accessed at http //www.aehs.com/publications/catalog/ contents/tph.htm ... 

Since this often applies to leaching experiments and to practical applications dealing with diffuse pollution, transport in soils is often treated as a one-dimensional problem. Using a 1-D mass balance equations, both concentration definitions are related through ... 

An additional definition problem relates to the description of sampling localities in many studies simply in terms of soil type. 

Tnteraction of aluminum and phosphate has long been a problem of interest to soil scientists and water chemists. Many different precipitates have been prepared by mixing solutions of aluminum salts and phosphate (4, 5, 6, 17). Some of these precipitates are crystalline, but many others are amorphous. Some have definite stoichiometric compositions, but many others do not. Some are dissolved in IN HCl almost instantaneously, but others can be dissolved only after prolonged heating. On the other hand, the formation of soluble complexes of aluminum and phosphate has been suggested (3y 8,14). 

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