AFFECTED ENVIRONMENT - SOIL

Plants may be affected by indirect modifications of the environment. Soil acidification, for example, can cause the leaching of nutrients, and the release of toxic aluminum. These effects may operate together to produce nutrient deficiencies or imbalances to plants. High soil concentrations of aluminum may prevent uptake and utilization of nutrients by plants.Increased availability of aluminum in soils has been implicated as a cause of forest declines in both Europe and the United States, possibly through the toxic effects on small feeder roots 14),... 

Pepper I.L., Bezdicek D.F., Baker A.S., Sims J.M. Silage com uptake of sludge-applied zinc and cadmium as affected by soil pH. J Environ Qual 1983 12 (2) 270-275. 

While not stated explicitly, in this discussion so far, it has been assumed that all the systems were well defined, at equilibrium, and at a constant 25°C. None of these conditions occur in soil in the environment. Soil is not a pure system and, often, all the components affecting redox reactions are not known, defined, or understood, and a host of different redox couples are likely to be present. Unless it is possible to take into account all couples present, it is not possible to describe the exact redox conditions in a soil without measuring it. 

Though the body itself forms the primary decompositional site, the soil beneath it may be equally important. Corpses located in outdoor environments on a terrestrial surface create an interface within which soil fauna and carrion-dwelling organisms interact. The interactions in this zone are affected by soil type, vegetation, decomposition of the corpse, and a variety of environmental factors. Apart from the work by Bornemissza (1957) and Lundt (1964) the succession of insects in this interface, and within the soil itself, has been largely overlooked in the literature, and the forensic implications have yet to be considered. 

Kruger, E.L., Somasundaram, L., Kanwar, R.S. (1993) Persistence and degradation of [14C]atrazine and [14C]deisopropylatrazine as affected by soil depth and moisture conditions. Environ. Toxicol. Chem. 12, 1959-1967. 

Several types of interactions are possible when a herbicide is introduced into the plant environment. In addition to the desired effects of the herbicide on weeds, growth alteration of crop plants may occur. It follows then that any pesticide, applied to plants or soils to control a specific pest, may also affect nontarget soil microorganisms and plants. Therefore the phenomenon of disease increase due to herbicides is not restricted to a specific group of herbicides, pathogens, or crops. 

Smolders, E., K. Oorts, P. Van Sprang, et al. 2009. Toxicity of trace metals in soil as affected by soil type and aging after contamination Using cahbrated bioavaUability models to set ecological soil standards. Environ. Toxicol. Ghem. 28 1633-1642. 

Environmental Problems—This section describes N Reactor operational activities that affected the environment. The affected environs are groundwater contamination (radionuclides, volatile organics, polychlorinated biphenyls (PCB), metals, and other Inorganics) soil contamination (surface and vadose zone contamination from radionuclides and organic compounds) biota contamination (flora [vegetation] and fauna [animals] from radionuclide uptake by plants or Ingestion by animals) and evaluated radiation at the Columbia River (unshielded sediments In the 1301-N Liquid Waste Disposal Facility). 

This section provides a description of environmental problems at the 100-N site linked to N Reactor operations. The operational activities affecting the environment are described first, followed by an assessment of the affected environments (groundwater, soil, and biota). The net effect of N Reactor operations on the environment is also included. 

Persistence of pesticides in the environment is controlled by retention, degradation, and transport processes and their interaction. Retention refers to the abihty of the soil to bind a pesticide, preventing its movement either within or outside of the soil matrix. Retention primarily refers to the sorption process, but also includes absorption into the soil matrix and soil organisms, both plants and microorganisms. In contrast to degradation that decreases the absolute amount of the pesticide in the environment, sorption processes do not affect the total amount of pesticide present in the soil but can decrease the amount available for transformation or transport. 

Transport processes describe movement of the pesticide from one location to another or from one phase to another. Transport processes include both downward leaching, surface mnoff, volatilization from the soil to the atmosphere, as weU as upward movement by capillary water to the soil surface. Transport processes do not affect the total amount of pesticide in the environment however, they can move the pesticide to sites that have different potentials for degradation. Transport processes also redistribute the pesticide in the environment, possibly contaminating sites away from the site of apphcation such as surface and groundwater and the atmosphere. Transport of pesticides is a function of both retention and transport processes. 

Many factors affect the mechanisms and kinetics of sorption and transport processes. For instance, differences in the chemical stmcture and properties, ie, ionizahility, solubiUty in water, vapor pressure, and polarity, between pesticides affect their behavior in the environment through effects on sorption and transport processes. Differences in soil properties, ie, pH and percentage of organic carbon and clay contents, and soil conditions, ie, moisture content and landscape position climatic conditions, ie, temperature, precipitation, and radiation and cultural practices, ie, crop and tillage, can all modify the behavior of the pesticide in soils. Persistence of a pesticide in soil is a consequence of a complex interaction of processes. Because the persistence of a pesticide can govern its availabiUty and efficacy for pest control, as weU as its potential for adverse environmental impacts, knowledge of the basic processes is necessary if the benefits of the pesticide ate to be maximized. 

CDU in pure form is a white powder. It is made slowly available to the soil solution by nature of its limited solubihty in water. Once in the soil solution, nitrogen from CDU is made available to the plant through a combination of hydrolysis and microbial decomposition. As with any CRE which is dependent on microbial action, the mineralization of CDU is temperature dependent. Product particle size has a significant effect on CDU nitrogen release rate. Smaller particles mineralize more rapidly because of the larger surface contact with the soil solution and the microbial environment. The rate of nitrogen release is also affected by pH because CDU degrades more rapidly in acidic soils. 

Adsorption — An important physico-chemical phenomenon used in treatment of hazardous wastes or in predicting the behavior of hazardous materials in natural systems is adsorption. Adsorption is the concentration or accumulation of substances at a surface or interface between media. Hazardous materials are often removed from water or air by adsorption onto activated carbon. Adsorption of organic hazardous materials onto soils or sediments is an important factor affecting their mobility in the environment. Adsorption may be predicted by use of a number of equations most commonly relating the concentration of a chemical at the surface or interface to the concentration in air or in solution, at equilibrium. These equations may be solved graphically using laboratory data to plot "isotherms." The most common application of adsorption is for the removal of organic compounds from water by activated carbon. 

From the practical point of view, the principal variation of environment which is definitely under the control of the cultivator, is, of course, the alteration in the composition of the soil, which is brought about by scientific manuring, llie analysis of fruits and vegetables will give the ordinary agriculturist much information as to the necessary mineral ingredients to be added to the soil but in the case of essential oils, the conditions are entirely different. The various parts of the plant tissue are affected in different ways by the same mineral salts, and successful development of the fruit or any other given part of the plant may have little or no relationship with the quantity or quality of essential oil produced. So that it is only by actual distillations of the plant, or portion of the plant, coupled with an exhaustive examination of the essential oil, that informative results can be obtained. 

The human impact on the environment affects many areas of our lives and future. One example is the effect of acid rain on biodiversity, the diversity of living things. In the prairies that extend across the heartlands of North America and Asia, native plants have evolved that can survive even nitrogen-poor soil and drought. By studying prairie plants, scientists hope to breed food plants that will be hardy sources of food in times of drought. However, acid rain is making some of these plants extinct. 

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