Chemical substances and the environment
In the last few decades people have become increasingly aware of the issues environmental chemistry encompasses and of its remarkable power to treat those issues. Environmental toxicologists and atmospheric and oceanic modelers are discovering crises at a prodigious rate, solutions are being suggested, and governments and international agencies are taking steps to implement them. It is tempting to see these changes as products of modern science, particularly modern chemistry: to believe that science has finally progressed sufficiently to allow humans to run the world properly (Mauskopf 1993). People can claim that man’s ability to model has allowed him to predict a set of photochemical reactions in the upper atmosphere and that his analytical abilities have enabled him to document, with startling sensitivity, that a number of these predictions are accurate. In this perspective environmental chemistry is likely to be seen as an outcome of the accumulation of chemical knowledge, the development of statistical research methods, and much better understandings of transport processes in soils, bodies of water, and the atmosphere (Mauskopf 1993).
Here it will be the product of a mature science where a certain level of knowledge has generated new research possibilities whose exploration leads to a recognition of needs for policy, to policies themselves, and to further research problems. It would seem to follow that there could have been little environmental chemistry prior to that maturity, simply because there would have been no grounds for concern or any sound basis for policy. In such a view, then, environmental chemistry is a product of knowledge and leads to action. In terms of the history of chemistry, the field of what may loosely be called environmental chemistry is rich with important and largely unstudied questions. It is perhaps the key area for understanding the interaction between chemistry on the one hand and society and culture on the other (Mauskopf 1993).
For years environmental chemistry had a reputation among chemical researchers as a soft science. Its practitioners were seen as interested mostly in tracking pollution, detoxifying hazardous chemicals, and recycling materials none of which got much respect in a culture where real chemists delved into the nitty-gritty of reaction dynamics and catalysis. And the few chemists who did want to look for environmentally friendly processes had a tough time getting funding approved by peer-review panels. But the situation is changing. The realization is spreading that environmental chemistry is more than pollution cleanup, and that designing chemical reactions to minimize waste is just as hard as designing reactions to maximize yield. Funding is also improving (Pool 1997). In 1992 the National Science Foundation and the Environmental Protection Agency started a program to pay for research into environment-friendly chemistry, and chemical companies themselves are carrying out similar research as the realization sinks in that, in the long run, it will cost less to make their products with a minimum of waste and risk than to keep the old methods and clean up after them. Finally, although it’s harder to measure, it seems that the chemical industry is changing its attitude on pollution control from foot-dragging resistance to an active, if not eager, commitment. Even with the changes in attitude among chemists and chemical company managers, it will be decades before the chemical industry reworks itself completely (Pool 1997).
Not only must chemists find new methods for synthesizing hundreds of chemicals, but those methods must also then be scaled up from laboratory demonstrations to industrial processes. Many, if not most, of the new methods will be less efficient than the ones they are replacing, so chemical engineers will have to be extra diligent in maximizing their yield, and chemical companies will have to weigh the environmental benefits against the economic disadvantages. Furthermore, the industry has hundreds of billions of dollars invested in plants and equipment, and it can afford to retrofit only a small part of that. Most of the changes will come as new plants are designed and built according to the new philosophy. Still, all the evidence today implies that it will happen. And when it does, it will be the most extensive technical fix in history: the remaking of an entire industry to reflect the changing needs and desires of the world around it (Wheeler 2004). Chemicals and the environment usually don’t go together but there are certain events where chemicals are needed to enhance the performance of the environment. Chemicals and some of its components create a certain reaction that proves vital for the longevity of some aspects of the environment. Chemical components are used to stabilize the soil through the process of lime stabilization.
Stabilization of soil
Soil is central to the natural terrestrial environment, No part of the environment is more important than any other, either in economic or ecological terms, but soil has the most linkages to other parts of the total natural environment. The interaction of other elements of the environment at any one place is expressed in the character of the soil. In itself, soil is a very complex environment, highly variable over space because it is produced by the interaction of environmental factors at any one point in space. Soil is a three-dimensional mantle of organic and inorganic material over most of the earth’s land surface. It is a multi-function medium, providing a rooting place for the anchorage and growth of plants, a habitat for soil flora and fauna, an environment for the decay of organic litter, a reservoir and drain for soil water, a store and supply of plant nutrients, a sink and pathways for pollutants, a foundation for buildings and roads, as well as being a vital natural resource for agriculture. Soil functions as an open system of many parts. To modify one part of the soil system, possibly through management, may create changes in other parts of the system (Compton et al. 1999).
All parts are interconnected and interactive as defined in an open system. Frequently, mistakes of bad management occur simply because of lack of understanding of the functioning of the soil system and, conversely, recovery may also be due to the resilience of its system character (Compton et al. 1999).Some changes in soils and sediments undoubtedly result from the inner workings of soil and sediment systems. Such changes will occur without environmental change. In sedimentology, internally driven changes are called autogenic and are contrasted with allogenic change that is induced by environmental fluctuations. These terms are equally applicable to pedogenic changes. In sediment systems, external and internal agents often have a cyclical character that imparts rhythm to sedimentation. Autocyclic processes include mud slumping, storms, and turbidity currents. Allocyclic processes include global sea-level fluctuations, climatic change, tectonic change, and changing biological productivity. It is sometimes difficult, but not usually impossible, to disentangle the effects of autocyclic and allocyclic processes (Huggett 1997). Orbital signals in small-scale stratigraphic sequences are plainly allogenic in origin. However, a large number of sediment sequences lack clear-cut orbital signals. This may be due to the cloaking effect of autocyclic perturbations. Some autocyclic processes produce a chaotic pattern of sedimentation rates and camouflage the orbital signals. In soils, autogenic changes often occur when internal thresholds are crossed and may be distinguished from allogenic changes (Huggett 1997). The soil undergoes various changes that block its use for agricultural or commercial use. One change that happens to the soil is when it has moisture. When the soil shows signs of moisture it will be difficult for the owners to use it according to their agricultural or commercial purpose. To counter soil moisture various processes are used depending on the extent of the damage and the gravity of the moisture. One method to counter soil moisture is the use of liming and liming processes.
Lime Stabilization
There are a number of approaches to the management and remediation of soil and surface water acidity, including liming, sensible forestry management and reduction of acid emissions into the atmosphere. Liming has long been practiced on agricultural land to remedy the problems of acidity, slow organic matter turnover, poor nodulation in some legumes, calcium and molybdenum deficiency, and aluminum and manganese toxicity. Liming materials most commonly used include ground limestone, chalk, marl and basic slag, the main active constituent being calcium carbonate; other minor components include quicklime, slaked lime and magnesium carbonate (Ellis & Mellor 1995). The lime requirement of a soil varies depending on its buffering capacity and is usually expressed as the amount of CaCO3 required to raise the pH of the top 15 cm of soil to the desired value. In temperate areas, the ideal soil pH is about 6.5 for arable crops and about 6.0 for grassland. In tropical areas, however, pH values of about 5.5 are often preferred, particularly in soils with high exchangeable aluminum contents, where phosphorus availability may be restricted under more alkaline conditions (Ellis & Mellor 1995).
Once the acid rain enters the soil, its impact will depend very much on the soil type and the underlying bedrock. Soils derived from granite, for example, will already be acidic, and therefore vulnerable to further increases. In contrast, soils developed over limestone, or some other calcium-rich source, will have the ability to neutralize large quantities of additional acid. Natural processes, such as the decay of organic matter or the weathering of minerals, increase the acidity of many soils, and it is often difficult to assess the contribution of acid rain to the total. Indeed, it has been argued that the addition of atmospheric acids may be relatively insignificant compared with those from in-soil processes. The situation is further complicated when such soils are developed for agriculture (Kemp 1994). To maintain productivity, it is necessary to make regular applications of fertilizer and lime, which mask acidification. Lime has been used as a means of sweetening acid soils for many years, and may be the reason that in areas of acid soils agricultural land is less affected by acid rain than the natural environment. In areas where natural regeneration is no longer possible, the restoration of the original chemical balance of the soil by liming and appropriate fertilizer application might allow reforestation to be successful. The neutralizing effects of the lime may last longer than those of the antacid, but they do wear off in 3 to 5 years and re-liming is necessary as long as acid loading continues. The treatment of the environment with lime to combat acidity is only a temporary measure, at best. It can be used to initiate recovery, or to control the problem until abatement procedures take effect, but since it deals only with the consequences of acid rain rather than the causes, it can never provide a solution (Kemp 1994). The process of liming neutralizes acidity in the soil and contributes to the increase of soil bacteria activity. Lime is known as a basic chemical, when used properly the soil it is applied on becomes more basic thus making it neutral. Over the years liming has undergone various changes; one change is the introduction of mini cone penetration.
Mini cone penetration
Soil strength is important for plant growth. Damaged, compacted soils where the grains are more closely locked together are difficult environments for plant growth. Field studies confirm that cone readings increase as biological productivity declines. The Critical Cone Index value is that which shows where root elongation is suppressed. It varies with clay content, bulk density and, inversely, with soil moisture. In soils with higher clay contents, the key control of root growth is not soil strength but the presence of shrinkage cracks which allow macro pores to form, through which roots penetrate (Halliwell & Watts 1996). The cone penetration test (CPT) is a method used to determine the geotechnical engineering properties of soils and delineating soil stratigraphy. The CPT is one of the most used and widely accepted methods for soil investigation worldwide. The early applications of CPT aimed to determine the soil geotechnical property of bearing capacity. The original cone penetrometers made use of simple mechanical measurements of the total penetration resistance to pushing a tool with a conical tip into the soil. Different methods were developed and used to separate the total measured resistance into components generated by the conical tip and friction generated by the rod string. CPT is gaining popularity because of its increased accuracy, speed of deployment, more continuous soil profile and reduced cost over other soil testing methods. Mini cone penetration test requires lesser force and it lowered certain standards in measurement. Mini cone penetration is used more on smaller masses of soil. It is used on soils that have lesser problems.
References
Compton, P, Devuyst, D, Hens, L & Nath, B (eds.) 1999,
Environmental management in practice: Compartments,
stressors, and sectors, 2nd edn, Routledge, London.
Ellis, SE & Mellor, A 1995, Soils and environment,
Routledge, New York.
Halliwell, L & Watts, S (eds.) 1996, Essential
environmental science: Methods & techniques, Routledge, New
York.
Huggett, R 1997, Environmental change: The evolving
ecosphere, Routledge, London.
Kemp, DD 1994, Global environmental issues: A
climatological approach, Routledge, New York
Mauskopf, SH (ed.) 1993, Chemical sciences in the modern
world, University of Pennsylvania Press, Philadelphia.
Pool, R 1997, Beyond engineering: How society shapes
technology, Oxford University Press, New York.
Wheeler, SM 2004, Planning for sustainability: creating
livable, equitable, and ecological communities, Routledge,
New York.
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