Bomba quimica tiempo

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  • Publicado : 16 de mayo de 2011
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chemical time bomb (CTB) is a chain of events resulting in the delayed and sudden occurrence of harmful effects caused by the mobilization of chemicals stored in soils and sediments in response to slow alterations of the environment. A chain of events can cause the sudden mobilization of aluminum from soils because of slow alterations in the capacity of soils to buffer acidification by aluminum.As soil acidification spreads, the region over which aluminum will be leached also increases. Gradual and diffuse pollution of soils causes a shift within the microbial community which in turn can affect the ability of soil microbes to biodegrade other harmful compounds. Not only heavy metals but also certain organic chemicals can unexpectedly inhibit bacterial degradation of certain pesticides.In designing programs to predict CTB, the most vulnerable areas should be examined. The bottom up approach for identifying CTBs uses what is known about processes and environmental conditions and works backward to predict or anticipate potential time bombs. When attempting to predict the occurrence of CTB some points to be considered are: environmental conditions that can have a dominant effect onsystem properties; certain processes that affect these environmental conditions; feedback mechanisms, such as effects of systemic changes on environmental conditions; the type of chemical (its persistence, metabolism, reaction products, toxicity, and the quantity released); loading and unloading mechanisms and processes; retention mechanisms and characteristics; system properties affectingretention; release and pathways; and targets and effects of release

Chemical time bomb in the CIS

The members of the Commonwealth of Independent States (CIS) have vast quantities of persistent organic pollutants (POPs) which are obsolete and redundant. None of the States knows how much of these chemicals it has to deal with, or what should be done with them. But a recent meeting in Moscow of CISdelegates provided the sketchy outlines of a very disturbing picture with global implications.

Now that the communist regime has been replaced, and the Soviet Union dissolved, one of the most worrying results of the mismatch between supply and demand of pesticides is emerging. Supply exceeded demand many times over, for many years. The result is an accumulation of unused pesticides.
    TheUnited Nations Environment Programme (UNEP) Chemicals section, based in Switzerland hosted the Moscow meeting, and is taking the lead in addressing the need to safely dispose of and find replacements for Persistent Organic Pollutants (POPs); those chemicals which threaten the global environment by virtue of their persistence, mobility and toxic properties. Most POPs are pesticides but they alsoinclude industrial chemicals such as polychlorinated biphenyls (PCBs), widely used in electrical equipment such as transformers and capacitors.
CIS reports
Reports given by the CIS States demonstrated a profound lack of knowledge about the scale and condition of obsolete pesticide stocks. The little information that was available indicated the existence of vast stocks of chemicals, much in very poorconditions and inappropriately managed. At the same time a high level of technical and scientific knowledge has been applied to the development of potentially creative ways of dealing with the waste. The ongoing economic crisis in the region has already led to quick, easy and very dangerous solutions being implemented. These include burial and incineration in cement kilns with no safeguards and noemission controls. More of this may well take place in the months and years to come, unless radical programmes are developed.
    In Russia there are an estimated 40,000 tonnes of pesticides and between 500-700,000 tonnes of PCB.  There is no detailed inventory of stockpiles, but funds have recently been allocated via UNEP for an inventory to be carried out.
    No large-scale facilities for...
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